Huawei Sig Guide

HUAWEI BSC6000 Base Station Subsystem V900R003

BSS Signaling Analysis Guide

Issue

01

Date

2007-11-26

Part Number

00379162

Huawei Technologies Proprietary

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Copyright © 2007 Huawei Technologies Co., Ltd. All rights reserved. No part of this document may be reproduced or transmitted in any form or by any means without prior written consent of Huawei Technologies Co., Ltd.

Trademarks and Permissions and other Huawei trademarks are the property of Huawei Technologies Co., Ltd. All other trademarks and trade names mentioned in this document are the property of their respective holders.

Notice The information in this document is subject to change without notice. Every effort has been made in the preparation of this document to ensure accuracy of the contents, but the statements, information, and recommendations in this document do not constitute a warranty of any kind, express or implied.


HUAWEI BSC6000 Base Station Subsystem BSS Signaling Analysis Guide

Contents

Contents About This Document.....................................................................................................................1 1 BSS Signaling Fundamental....................................................................................................1-1 1.1 A Interface.......................................................................................................................................................1-2 1.1.1 A Interface Protocol Model....................................................................................................................1-2 1.1.2 Physical Layer on the A Interface..........................................................................................................1-3 1.1.3 MTP Layer on the A Interface...............................................................................................................1-3 1.1.4 SCCP Layer on the A Interface..............................................................................................................1-6 1.1.5 BSSAP Layer on the A Interface...........................................................................................................1-6 1.2 Abis Interface................................................................................................................................................1-11 1.2.1 Abis Interface Protocol Model.............................................................................................................1-11 1.2.2 Abis Interface Structure.......................................................................................................................1-12 1.2.3 Physical Layer on the Abis Interface ..................................................................................................1-14 1.2.4 LAPD Layer on the Abis Interface.......................................................................................................1-14 1.2.5 L3 Traffic Management Messages on the Abis Interface....................................................................1-15 1.2.6 L3 OM Messages on the Abis Interface...............................................................................................1-18 1.3 Um Interface..................................................................................................................................................1-20 1.3.1 Physical Layer on the Um Interface.....................................................................................................1-20 1.3.2 LAPD Layer on the Um Interface........................................................................................................1-21 1.3.3 L3 Entity on the Um Interface..............................................................................................................1-22

2 BSS Signaling Tracing..............................................................................................................2-1 2.1 Tracing the Messages on the Um Interface.....................................................................................................2-2 2.2 Tracing Messages on the Abis Interface.........................................................................................................2-3 2.2.1 Tracing the RSL Messages on the Abis Interface..................................................................................2-3 2.2.2 Tracing the OML Messages on the Abis Interface.................................................................................2-7 2.2.3 Tracing the ESL Messages on the Abis Interface..................................................................................2-9 2.2.4 Tracing the LAPD Messages on the Abis Interface.............................................................................2-12 2.3 Tracing the Messages on the A Interface......................................................................................................2-15 2.3.1 Tracing the BSSAP Messages on the A Interface................................................................................2-15 2.3.2 Tracing the MTP2 Messages on the Interface......................................................................................2-19 2.3.3 Tracing the MTP3 Messages on the A Interface..................................................................................2-22 2.3.4 Tracing the SCCP Messages on the A Interface..................................................................................2-25 2.4 Tracing Messages on the Pb Interface...........................................................................................................2-28 Issue 01 (2007-11-26)


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2.4.1 Tracing the Application Messages on the Pb Interface........................................................................2-28 2.4.2 Tracing the LAPD Messages on the Pb Interface................................................................................2-30 2.5 Tracing the Messages on the BSC-CBC Interface........................................................................................2-32 2.6 Tracing User Messages.................................................................................................................................2-33

3 BSS System Information...........................................................................................................3-1 3.1 BSS System Information Type........................................................................................................................3-2 3.1.1 System Information Type 1 ...................................................................................................................3-2 3.1.2 System Information Types 2, 2bis, 2ter, and 2quater.............................................................................3-6 3.1.3 System Information Type 3 ...................................................................................................................3-8 3.1.4 System Information Type 4 .................................................................................................................3-11 3.1.5 System Information Types 5, 5bis, and 5ter.........................................................................................3-12 3.1.6 System Information Type 6 .................................................................................................................3-13 3.1.7 System Information Type 7 .................................................................................................................3-14 3.1.8 System Information Type 8 .................................................................................................................3-14 3.1.9 System Information Type 13 ...............................................................................................................3-14 3.2 Internal BSC Signaling Procedure of the System Information.....................................................................3-15

4 Immediate Assignment.............................................................................................................4-1 4.1 Immediate Assignment Procedure..................................................................................................................4-2 4.2 Internal BSC Signaling Procedure of Immediate Assignment........................................................................4-4 4.3 Abnormal Immediate Assignment Cases........................................................................................................4-4 4.3.1 Failure in Receiving an Establish Indication Message After Channel Activation.................................4-4 4.3.2 BSC Sending an Immediate Assignment Reject Message.....................................................................4-5

5 Classmark Update......................................................................................................................5-1 5.1 Classmark Update Procedure..........................................................................................................................5-2

6 Location Update..........................................................................................................................6-1 6.1 Location Update Procedure.............................................................................................................................6-2 6.1.1 Periodic Update Procedure.....................................................................................................................6-2 6.1.2 IMSI Attach Procedure...........................................................................................................................6-3 6.1.3 Generic Location Update Procedure......................................................................................................6-3 6.2 Internal BSC Signaling Procedures of Location Update.................................................................................6-5 6.3 Abnormal Location Update Cases...................................................................................................................6-5 6.3.1 Location Update Not Started or Aborted on the MS Side......................................................................6-5 6.3.2 Location Update Failure on the Network Side.......................................................................................6-6

7 Authentication............................................................................................................................7-1 7.1 Authentication Principles................................................................................................................................7-2 7.2 Authentication Procedure................................................................................................................................7-2 7.3 Authentication Failure.....................................................................................................................................7-3 7.4 Internal BSC Signaling Procedure of Authentication.....................................................................................7-4 7.5 Abnormal Authentication Cases......................................................................................................................7-4 7.5.1 RR Connection Failure...........................................................................................................................7-5 ii


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7.5.2 Timer T3260 Expiry...............................................................................................................................7-5 7.5.3 SIM Unregistered...................................................................................................................................7-5

8 Ciphering.....................................................................................................................................8-1 8.1 Ciphering Procedure........................................................................................................................................8-2 8.2 Ciphering Mode Change.................................................................................................................................8-3 8.3 Internal BSC Signaling Procedure of Ciphering.............................................................................................8-3 8.4 Abnormal Ciphering Cases.............................................................................................................................8-4 8.4.1 BSS Sending a Cipher Mode Reject Message.......................................................................................8-4 8.4.2 MS Doing No Processing.......................................................................................................................8-4

9 TMSI Reallocation.....................................................................................................................9-1 9.1 TMSI Reallocation Procedure.........................................................................................................................9-2 9.2 Internal BSC Signaling Procedure of TMSI Reallocation..............................................................................9-2 9.3 Abnormal TMSI Reallocation Cases...............................................................................................................9-3 9.3.1 TMSI Reallocation Caused by RR Connection Failure on the Network Side.......................................9-3 9.3.2 TMSI Reallocation Caused by T3250 Expiry........................................................................................9-3

10 Speech Channel Assignment...............................................................................................10-1 10.1 Speech Channel Assignment Procedure......................................................................................................10-2 10.2 Channel Mode Modification Procedure......................................................................................................10-3 10.3 Internal BSC Signaling Procedure of Speech Channel Assignment...........................................................10-4 10.4 Abnormal Speech Channel Assignment Cases...........................................................................................10-5 10.4.1 BSC Sending an Assignment Failure Message..................................................................................10-5 10.4.2 BSC Receiving a Connection Failure Indication Message................................................................10-6 10.4.3 BSC Receiving an Error Indication Message.....................................................................................10-7

11 Mobile Originating Call Establishment............................................................................11-1 11.1 Mobile Originating Call Establishment Procedure.....................................................................................11-2 11.1.1 Early Assignment Procedure..............................................................................................................11-2 11.1.2 Late Assignment Procedure...............................................................................................................11-4 11.1.3 Very Early Assignment Procedure.....................................................................................................11-6 11.2 Internal BSC Signaling Procedure of Mobile Originating Call Establishment...........................................11-7 11.3 Abnormal Mobile Originating Call Establishment Cases...........................................................................11-7 11.3.1 Calling MS Cannot Be Heard.............................................................................................................11-8 11.3.2 MSC Releasing the Call after Sending a CM Service Reject Message..............................................11-8 11.3.3 Abnormal Procedure Caused by MS in Busy State............................................................................11-9 11.3.4 MSC Sending a Disconnect Message Instead of an Assignment Request Message..........................11-9 11.3.5 Abnormal Procedures Caused by MS Hangup...................................................................................11-9 11.3.6 Abnormal Procedures Caused by MSC Sending a Clear Command Message or a Disconnect Message .....................................................................................................................................................................11-10 11.3.7 LAPD Reporting an Error Indication Message During Call Establishment....................................11-10

12 Mobile Terminating Call Establishment...........................................................................12-1 12.1 Mobile Terminating Call Establishment Procedure....................................................................................12-2 12.2 Internal BSC Signaling Procedure of Mobile Terminating Call Establishment.........................................12-3 Issue 01 (2007-11-26)


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12.3 Abnormal Mobile Terminating Call Establishment Cases..........................................................................12-3 12.3.1 No Paging Message on the A Interface..............................................................................................12-3 12.3.2 No Paging Message on the Abis Interface.........................................................................................12-4 12.3.3 No Paging Response on the Abis Interface........................................................................................12-5 12.3.4 No Paging Response on the A Interface.............................................................................................12-6

13 BSC Release.............................................................................................................................13-1 13.1 Normal Release Procedure..........................................................................................................................13-2 13.2 Local Release Procedure.............................................................................................................................13-4

14 Handover..................................................................................................................................14-1 14.1 Handover Procedure....................................................................................................................................14-2 14.1.1 Intra-BSC Handover Procedure.........................................................................................................14-2 14.1.2 Inter-BSC Handover Procedure.........................................................................................................14-4 14.1.3 Inter-MSC Handover Procedure.........................................................................................................14-6 14.1.4 Inter-System Handover Procedure.....................................................................................................14-7 14.2 Internal BSC Signaling Procedure of Handover.........................................................................................14-9 14.2.1 Internal BSC Signaling Procedure of the Intra-BSC Handover.........................................................14-9 14.2.2 Internal BSC Signaling Procedure of the Inter-BSC Handover.........................................................14-9 14.2.3 Internal BSC Signaling Procedure of the Inter-MSC Handover......................................................14-10 14.2.4 Internal BSC Signaling Procedure of the Inter-System Handover...................................................14-10 14.3 Abnormal Handover Cases........................................................................................................................14-10 14.3.1 No Available Channels in the Target Cell.......................................................................................14-11 14.3.2 Old BSS Not Receiving a Specified Message upon T8 Expiry.......................................................14-11 14.3.3 Inter-Cell Handover Failure (MS Returning to the Old Channel)....................................................14-12 14.3.4 BSC Receiving a Connection Failure Indication Message..............................................................14-12 14.3.5 Forced Handover Failure..................................................................................................................14-13 14.3.6 Handover Failure Caused by CIC Malfunction................................................................................14-13 14.3.7 Handover Failure Caused by MS Access Failure.............................................................................14-13

15 Call Re-Establishment...........................................................................................................15-1 15.1 Call Re-Establishment Procedure................................................................................................................15-2 15.2 Internal BSC Signaling Procedure of Call Re-Establishment.....................................................................15-4 15.3 Abnormal Call Re-Establishment Cases.....................................................................................................15-4 15.3.1 Network Sending a CM Service Reject Message...............................................................................15-4 15.3.2 Call Re-Establishment Not Allowed or Re-Establishment Failure....................................................15-5 15.3.3 RR Connection Failure.......................................................................................................................15-5

16 Directed Retry.........................................................................................................................16-1 16.1 Directed Retry Procedure............................................................................................................................16-2 16.1.1 Intra-BSC Directed Retry Procedure..................................................................................................16-2 16.1.2 Inter-BSC directed retry procedure....................................................................................................16-4 16.1.3 Inter-MSC directed retry procedure...................................................................................................16-6 16.2 Internal BSC Signaling Procedure of Directed Retry.................................................................................16-7 16.2.1 Internal BSC Signaling Procedure of the Intra-BSC Directed Retry.................................................16-8 iv


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16.2.2 Internal BSC Signaling Procedure of the Inter-BSC Directed Retry.................................................16-8 16.2.3 Internal BSC Signaling Procedure of the Inter-MSC Directed Retry................................................16-9 16.3 Abnormal Directed Retry Cases..................................................................................................................16-9 16.3.1 No Available Channels in the Target Cell.........................................................................................16-9 16.3.2 Channel Activation Failure..............................................................................................................16-10

17 BSC Re-Assignment...............................................................................................................17-1 17.1 BSC Re-Assignment Procedure..................................................................................................................17-2 17.2 Internal BSC Signaling Procedure of BSC Re-Assignment........................................................................17-3 17.3 Abnormal BSC Re-Assignment Cases........................................................................................................17-3 17.3.1 BSC Failure in Initiating a Re-Assignment Procedure......................................................................17-3

18 Queuing and Preemption.....................................................................................................18-1 18.1 Queuing Procedure......................................................................................................................................18-2 18.2 Preemption Procedure.................................................................................................................................18-3 18.3 Internal BSC Signaling Procedure of Queuing and Preemption.................................................................18-4 18.4 Abnormal Queuing and Preemption Cases.................................................................................................18-4 18.4.1 BSC Sending the MSC a Clear Request Message..............................................................................18-4

19 Short Message Service...........................................................................................................19-1 19.1 Short Message Transfer Procedure.............................................................................................................19-2 19.1.1 Short Message Sending Procedure Initiated by an Idle MS...............................................................19-2 19.1.2 Short Message Receiving Procedure Initiated by an Idle MS............................................................19-3 19.1.3 Short Message Sending Procedure Initiated by a Busy MS...............................................................19-5 19.1.4 Short message receiving procedure initiated by a busy MS...............................................................19-5 19.2 Internal BSC Signaling Procedure of Short Message Transfer...................................................................19-6 19.3 Abnormal Short Message Transfer Cases...................................................................................................19-7 19.3.1 Short Message Sending Failure due to Authentication and Ciphering Disabled...............................19-7

20 Short Message Service Cell Broadcast...............................................................................20-1 20.1 SMSCB Procedure......................................................................................................................................20-2 20.1.1 CBC-BSC SMSCB Procedure...........................................................................................................20-2 20.1.2 BSC-BTS SMSCB Procedure............................................................................................................20-5 20.2 Internal BSC Signaling Procedure of the SMSCB......................................................................................20-6 20.3 Abnormal SMSCB Cases............................................................................................................................20-6 20.3.1 MS Failure in Receiving Cell Broadcast Messages...........................................................................20-7 20.3.2 CBCH Not Configured in a Cell........................................................................................................20-7

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Figures

Figures Figure 1-1 A interface signaling protocol model.................................................................................................1-3 Figure 1-2 L3 signaling message processing procedure.......................................................................................1-5 Figure 1-3 Abis interface protocol model..........................................................................................................1-12 Figure 1-4 Abis interface structure.....................................................................................................................1-13 Figure 1-5 Logical links on the Abis interface...................................................................................................1-14 Figure 1-6 Management objects.........................................................................................................................1-18 Figure 1-7 Interfaces of L1 on the Um interface................................................................................................1-21 Figure 1-8 L3 signaling message processing procedure.....................................................................................1-24 Figure 1-9 Services provided by the RR sublayer..............................................................................................1-25 Figure 1-10 Services provided by the MM sublayer..........................................................................................1-25 Figure 2-1 Tracing messages on the Um interface (set TRX as the filter condition)...........................................2-2 Figure 2-2 Results of tracing messages on the Um interface...............................................................................2-3 Figure 2-3 Trace & Monitor tab page...................................................................................................................2-5 Figure 2-4 Trace the RSL Message at Abis Interface dialog box........................................................................2-6 Figure 2-5 Tracing the RSL messages on the Abis interface ..............................................................................2-7 Figure 2-6 Trace & Monitor tab page...................................................................................................................2-8 Figure 2-7 Trace the OML Message at Abis Interface dialog box.......................................................................2-8 Figure 2-8 Tracing the OML messages on the Abis interface .............................................................................2-9 Figure 2-9 Trace & Monitor tab page.................................................................................................................2-10 Figure 2-10 Trace the ESL Message at Abis Interface dialog box.....................................................................2-11 Figure 2-11 Tracing the ESL messages on the Abis interface ..........................................................................2-11 Figure 2-12 Trace & Monitor tab page...............................................................................................................2-13 Figure 2-13 Trace the LAPD Message at Abis Interface dialog box.................................................................2-14 Figure 2-14 Tracing the LAPD messages on the Abis interface .......................................................................2-15 Figure 2-15 Trace & Monitor tab page...............................................................................................................2-16 Figure 2-16 Trace the BSSAP Message at A Interface dialog box....................................................................2-17 Figure 2-17 Tracing the BSSAP messages at A interface .................................................................................2-18 Figure 2-18 Trace the BSSAP Message at A Interface (1)................................................................................2-18 Figure 2-19 Trace & Monitor tab page...............................................................................................................2-20 Figure 2-20 Trace the MTP2 Message at A Interface dialog box......................................................................2-21 Figure 2-21 Tracing the MTP2 messages on the A interface ............................................................................2-22 Figure 2-22 Trace & Monitor tab page...............................................................................................................2-23 Figure 2-23 Tracing the MTP3 Messages at A Interface...................................................................................2-24 Issue 01 (2007-11-26)


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Figures

Figure 2-24 Tracing the MTP3 messages at A interface ...................................................................................2-25 Figure 2-25 Trace & Monitor tab page...............................................................................................................2-26 Figure 2-26 Tracing the SCCP Messages on the A Interface.............................................................................2-27 Figure 2-27 Tracing the SCCP messages on the A interface.............................................................................2-28 Figure 2-28 Trace & Monitor tab page...............................................................................................................2-29 Figure 2-29 Trace the Application Message at Pb Interface dialog box............................................................2-30 Figure 2-30 Trace & Monitor tab page...............................................................................................................2-31 Figure 2-31 Trace the LAPD Message at Pb Interface dialog box.....................................................................2-32 Figure 2-32 Trace the Message at BSC-CBC Interface dialog box...................................................................2-33 Figure 2-33 Trace User Message dialog box......................................................................................................2-34 Figure 2-34 Result of tracing user messages......................................................................................................2-35 Figure 3-1 Set Cell Attributes dialog box..........................................................................................................3-17 Figure 4-1 Immediate assignment procedure.......................................................................................................4-2 Figure 5-1 Classmark update procedure...............................................................................................................5-2 Figure 7-1 Authentication procedure....................................................................................................................7-3 Figure 7-2 Unsuccessful authentication procedure..............................................................................................7-4 Figure 8-1 Ciphering procedure...........................................................................................................................8-2 Figure 9-1 TMSI reallocation procedure..............................................................................................................9-2 Figure 10-1 Speech channel assignment procedure...........................................................................................10-2 Figure 10-2 Channel mode modification procedure...........................................................................................10-4 Figure 11-1 Early assignment procedure............................................................................................................11-3 Figure 11-2 Late assignment procedure.............................................................................................................11-5 Figure 11-3 Very early assignment procedure...................................................................................................11-6 Figure 12-1 Mobile terminating call establishment procedure...........................................................................12-2 Figure 13-1 Normal release procedure...............................................................................................................13-3 Figure 13-2 Local release procedure..................................................................................................................13-5 Figure 14-1 Intra-BSC handover procedure.......................................................................................................14-3 Figure 14-2 Inter-BSC handover procedure.......................................................................................................14-5 Figure 14-3 Inter-MSC handover procedure......................................................................................................14-7 Figure 14-4 GSM-to-UMTS handover procedure .............................................................................................14-8 Figure 14-5 UMTS-to-GSM handover procedure..............................................................................................14-8 Figure 15-1 Call re-establishment procedure.....................................................................................................15-2 Figure 16-1 Intra-BSC directed retry procedure................................................................................................16-3 Figure 16-2 Inter-BSC directed retry procedure................................................................................................16-5 Figure 16-3 Inter-MSC directed retry procedure................................................................................................16-7 Figure 17-1 BSC re-assignment procedure........................................................................................................17-2 Figure 18-1 Queuing procedure.........................................................................................................................18-2 Figure 18-2 Preemption procedure.....................................................................................................................18-3 Figure 19-1 Short message sending procedure initiated by an idle MS.............................................................19-2 Figure 19-2 Short message receiving procedure initiated by an idle MS...........................................................19-4 Figure 19-3 Short message sending procedure initiated by a busy MS.............................................................19-5 Figure 19-4 Short message receiving procedure initiated by a busy MS...........................................................19-6 viii


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Figure 20-1 Procedure for Sending or Replacing a Message.............................................................................20-2 Figure 20-2 Procedure for deleting an existing message....................................................................................20-3 Figure 20-3 Procedure for querying the CBCH status.......................................................................................20-3 Figure 20-4 Procedure for querying the message status.....................................................................................20-4 Figure 20-5 Procedure for resetting a cell..........................................................................................................20-4 Figure 20-6 Procedure for setting the DRX.......................................................................................................20-5 Figure 20-7 BSC Sending an SMS Broadcast Command Message...................................................................20-5 Figure 20-8 BTS Sending the BSC a CBCH Loading Indication Message.......................................................20-6 Figure 20-9 SMSCB procedure..........................................................................................................................20-6

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Tables

Tables Table 1-1 BSSAP protocol functionality..............................................................................................................1-8 Table 1-2 Administrative State...........................................................................................................................1-18 Table 1-3 Operational State................................................................................................................................1-19 Table 1-4 Available State...................................................................................................................................1-19 Table 3-1 Cell channel description.......................................................................................................................3-3 Table 3-2 Format of cell channel description.......................................................................................................3-3 Table 3-3 Relation between "S" and "T"..............................................................................................................3-5 Table 3-4 Multiband reporting............................................................................................................................. 3-7 Table 3-5 Meaning of the CCCH-CONF............................................................................................................. 3-9 Table 3-6 Parameters affecting cell priority in cell selection.............................................................................3-11 Table 3-7 RACH control parameters in System Information Type 1 and the corresponding parameters on the BSC6000 Local Maintenance Terminal..........................................................................................................3-16 Table 3-8 Control channel parameters in System Information Type 3 and the corresponding parameters on the BSC6000 Local Maintenance Terminal..........................................................................................................3-18 Table 3-9 Cell option parameters in System Information Type 3 and the corresponding parameters on the BSC6000 Local Maintenance Terminal...........................................................................................................................3-18 Table 3-10 Cell selection parameters in System Information Type 3 and the corresponding parameters on the BSC6000 Local Maintenance Terminal..........................................................................................................3-19 Table 3-11 Rest Oct parameters in System Information Type 4 and the corresponding parameters on the BSC6000 Local Maintenance Terminal...........................................................................................................................3-20

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About This Document

About This Document

Purpose This document describes the GBSS signaling fundamental, signaling trace, and system information, as well as the procedures such as location update, authentication, encryption, and call procedure.

Versions The following table lists the product versions related to this document. Product Names

Models

Versions

BSC

BSC6000

V900R001

PCU

PCU6000

V300R008

BTS

BTS3012

V300R004&V300R005&V300R006

BTS3012AE

V300R005&V300R006

BTS3006C

V300R005&V300R006

BTS3002E

V300R005

Intended Audience This document is intended for: l

Network planning engineers

l

Field engineers

l

System engineers

l

Shift operators

l

Network operators

l

Network management engineers

Change History Refer to Changes in BSS Signaling Analysis Guide. Issue 01 (2007-11-26)


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About This Document

Organization 1 BSS Signaling Fundamental The external BSS interfaces, which are the Um interface between the BSS and the MS, and the A interface between the BSS and the MSC, are standard interfaces. The Abis interface between the BSC and the BTS is an internal interface. 2 BSS Signaling Tracing This describes the BSS signaling tracing, which consists of the signaling tracing on the Um interface, Abis interface, A interface, Pb interface, and BSC-CBC interface, and single user signaling tracing. 3 BSS System Information System information (SI) refers to the major radio network parameters on the Um interface such as the network identification parameters, cell selection parameters, system control parameters, and network functional parameters. 4 Immediate Assignment This topic describes immediate assignment including its internal BSC signaling procedure and abnormal cases. 5 Classmark Update The MS classmark specifies the service capability, supported frequency bands, power capability, and ciphering capability of an MS in the GSM network. It is categorized into classmark 1, classmark 2, and classmark 3. 6 Location Update In the GSM system, MS location information is stored in the HLR, the VLR, and the MS. When the location information changes, relevant information in the HLR, the VLR, and the MS must be changed accordingly, which can be realized through the location update procedure. 7 Authentication The purpose of authentication is to permit the network to check whether the identity provided by the MS is acceptable or not and to prevent the private information of the legal subscribers from being stolen. 8 Ciphering Ciphering is used to secure the information exchange between an MS and a BTS. The information consists of the signaling information and the subscriber information. The subscriber information consists of the subscriber data and the subscriber voice. 9 TMSI Reallocation The TMSI reallocation takes place in ciphering mode. It is generally related to another procedure, such as location update or call establishment. 10 Speech Channel Assignment The speech channel assignment is the procedure for assigning TCHs to the MS according to the service requests. 11 Mobile Originating Call Establishment 2


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Mobile originating call refers to an MS calling another MS or a fixed phone. 12 Mobile Terminating Call Establishment Mobile terminating call refers to an MS called by another MS or a fixed phone. 13 BSC Release BSC release consists of the normal release and the local release. 14 Handover Handover is one of the basic functions of the GSM. It enables calls to be set up in better cells and reduces call drops. Handover also lowers cross interference. The handover procedure consists of handover triggering, handover preparation, handover decision, and handover execution. 15 Call Re-Establishment The call re-establishment procedure allows an MS to resume a connection after a radio link failure. It may take place in a new cell or a new location area. 16 Directed Retry Directed retry is a special type of handover. It refers to the process of assigning an MS to a TCH in a cell other than the serving cell when no radio resources are available. It is triggered by the assignment procedure and employs internal or external handover procedures. 17 BSC Re-Assignment BSC re-assignment refers to a TCH assignment procedure initiated by the BSC after the BSC receives an Assignment Failure message from the MS on the SDCCH. BSC re-assignment raises the rate of assignments on the Um interface. 18 Queuing and Preemption This topic describes queuing and pre-emption. 19 Short Message Service For an idle MS, short messages are transferred on the SDCCH. For a busy MS, however, short messages are transferred on the SACCH. The point-to-point short message procedure comprises two fundamental procedures: mobile originating short message transfer procedure and mobile terminating short message transfer procedure. 20 Short Message Service Cell Broadcast The short message service cell broadcast (SMSCB) is similar to the paging station broadcast service. The operators broadcast messages to the subscribers in the specified areas. The subscribers that subscribe to the service receive the messages broadcast by the operators.

Conventions 1. Symbol Conventions The following symbols may be found in this document. They are defined as follows

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About This Document

Symbol

Description

DANGER

WARNING

CAUTION

Indicates a hazard with a high level of risk that, if not avoided, will result in death or serious injury. Indicates a hazard with a medium or low level of risk which, if not avoided, could result in minor or moderate injury. Indicates a potentially hazardous situation that, if not avoided, could cause equipment damage, data loss, and performance degradation, or unexpected results. Indicates a tip that may help you solve a problem or save your time.

TIP

Provides additional information to emphasize or supplement important points of the main text.

NOTE

2. General Conventions Convention

Description

Times New Roman

Normal paragraphs are in Times New Roman.

Boldface

Names of files,directories,folders,and users are in boldface. For example,log in as user root .

Italic

Book titles are in italics.

Courier New

Terminal display is in Courier New.

3. Command Conventions

4

Convention

Description

Boldface

The keywords of a command line are in boldface.

Italic

Command arguments are in italic.

[]

Items (keywords or arguments) in square brackets [ ] are optional.

{x | y | ...}

Alternative items are grouped in braces and separated by vertical bars.One is selected.

[ x | y | ... ]

Optional alternative items are grouped in square brackets and separated by vertical bars.One or none is selected.

{ x | y | ... } *

Alternative items are grouped in braces and separated by vertical bars.A minimum of one or a maximum of all can be selected.


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Convention

Description

[ x | y | ... ] *

Alternative items are grouped in braces and separated by vertical bars.A minimum of zero or a maximum of all can be selected.

4. GUI Conventions Convention

Description

Boldface

Buttons,menus,parameters,tabs,window,and dialog titles are in boldface. For example,click OK.

>

Multi-level menus are in boldface and separated by the ">" signs. For example,choose File > Create > Folder .

5. Keyboard Operation Convention

Description

Key

Press the key.For example,press Enter and press Tab.

Key1+Key2

Press the keys concurrently.For example,pressing Ctrl+Alt+A means the three keys should be pressed concurrently.

Key1,Key2

Press the keys in turn.For example,pressing Alt,A means the two keys should be pressed in turn.

6. Mouse Operation

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Action

Description

Click

Select and release the primary mouse button without moving the pointer.

Double-click

Press the primary mouse button twice continuously and quickly without moving the pointer.

Drag

Press and hold the primary mouse button and move the pointer to a certain position.


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1

1 BSS Signaling Fundamental

BSS Signaling Fundamental

About This Chapter The external BSS interfaces, which are the Um interface between the BSS and the MS, and the A interface between the BSS and the MSC, are standard interfaces. The Abis interface between the BSC and the BTS is an internal interface. 1.1 A Interface This topic describes the A interface protocol model that consists of the physical layer, MTP layer, SCCP layer, and BSSAP layer. 1.2 Abis Interface The Abis interface lies between the BTS and the BSC. It complies with GSM Rec.08.5X series. The Abis interface is an internal interface of the BSS. The interworking between the BSC and BTS equipment from different manufactures is not available. The terrestrial traffic channels on the Abis interface map the radio traffic channels on the Um interface. 1.3 Um Interface The Um interface lies between an MS and the BTS. It is used for the interworking between the MS and the fixed part of the GSM system. The links on the Um interface are radio links. The Um interface transmits the information about radio resource management, mobility management, and connection management.

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1.1 A Interface This topic describes the A interface protocol model that consists of the physical layer, MTP layer, SCCP layer, and BSSAP layer. 1.1.1 A Interface Protocol Model The A interface is defined as a standard communication interface between the NSS and the BSS. 1.1.2 Physical Layer on the A Interface The physical layer on the A interface is a 2 Mbit/s 75-ohm coaxial cable or 120-ohm twisted pair. 1.1.3 MTP Layer on the A Interface The MTP layer on the A interface provides reliable signaling message transfer in the signaling network. In case of system failure and signaling network failure, it takes measures to avoid or reduce the message loss, repetition, and out of sequence. 1.1.4 SCCP Layer on the A Interface The network layer services provided by the SCCP are classified into connectionless service and connection-oriented service. 1.1.5 BSSAP Layer on the A Interface The BSSAP protocol, which serves as the A interface specification, describes two types of messages, BSSMAP messages and DTAP messages.

1.1.1 A Interface Protocol Model The A interface is defined as a standard communication interface between the NSS and the BSS. It is between the BSC and the MSC. The physical links on the A interface are standard 2.048 Mbit/s Pulse Code Modulation (PCM) digital links. The A interface transmits the information about MS management, mobility management, connection management, and service flow control. The A interface connects the BSC and the MSC from different manufactures. The GSM system uses the SS7 on the A interface. Physically, the A interface is the trunk circuit interface between the BSC and the MSC. Figure 1-1 shows the A interface signaling protocol model.

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Figure 1-1 A interface signaling protocol model BSS

MSC

BSSAP

BSSAP

DTAP

BSSMAP

DTAP

BSSMAP

Distribution function

Distribution function

SCCP

SCCP

MTP

MTP

Physical layer

A

DTAP: Direct Transfer Application MTP: Message Transfer Part Part BSSAP: Base Station Subsystem Application Part

SCCP: Signaling Connection Control Part

BSSMAP: Base Station Subsystem Management Application Part

1.1.2 Physical Layer on the A Interface The physical layer on the A interface is a 2 Mbit/s 75-ohm coaxial cable or 120-ohm twisted pair. The features of the physical layer on the A interface are as follows: l

The 2 Mbit/s transmission rate complies with the G.703.

l

The frame structure, synchronization, and timing comply with the G.705.

l

The fault management complies with the G.732.

l

CRC4 complies with the G.704.

1.1.3 MTP Layer on the A Interface The MTP layer on the A interface provides reliable signaling message transfer in the signaling network. In case of system failure and signaling network failure, it takes measures to avoid or reduce the message loss, repetition, and out of sequence. The MTP protocols are defined in ITU-T Q.701–Q.710 recommendations. The MTP layer comprises three sublayers, the signaling data link sublayer, signaling link sublayer, and signaling network sublayer.

Signaling Data Link Sublayer The signaling data link function layer (L1) defines the physical, electrical, and functional features of signal data. It specifies the way to connect with data links. A signaling data link transmits signaling in both directions. It comprises two data paths of 64 kbit/s and of opposite directions. Generally, a signaling data link occupies timeslot 16 of a trunk. The specific timeslot is Issue 01 (2007-11-26)


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determined through the negotiation between the BSC and the MSC. The timeslot can be used to establish a semi-permanent connection. A signaling data link serves as an information bearer of SS7. One of the important features of the signaling data link is that the information transferred on the link is transparent, that is, the data transferred on the link cannot be changed. Therefore, equipment such as echo canceler, digital attenuator, and A/u rate converter, cannot be connected to this link.

Signaling Link Function Layer Signaling link function layer (L2) specifies the functions and procedures for sending signaling to data links. Together with L1, it provides reliable signaling message transfer between two directly connected signaling points. Due to long-distance transmissions, a certain rate of bit errors may be caused on the data link between adjacent signaling points. However, no error is allowed in CCS7 signaling message codes. L2 guarantees error-free transmission of message codes when there are bit errors on L1. L2 performs signaling unit delimitation, signaling unit alignment, error detection, error correction, initial alignment, processor fault detection, flow control, and signaling link error rate monitoring.

Signaling Network Function Layer By controlling the route and performance of the signaling network, signaling network function layer (L3) guarantees reliable transmission of signaling information to the user part, no matter whether the signaling network is functional or not. The signaling network is functionally classified into the signaling message processing part and the signaling network management part. l

Signaling message processing part The signaling message processing part sends signaling messages from the user part of a signaling point to the target signaling links or user parts. The user part in the BSS refers to the SCCP only. The signaling message processing part comprises three smaller parts: message routing (MRT), message discrimination (MDC), and message distribution (MDT), as shown in Figure 1-2.

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Figure 1-2 L3 signaling message processing procedure MTP user part

Message distribution Messages to the local signaling point Messages to the other signaling points Message Message routing discrimination

MTP2 signaling link

–

Message Routing (MRT) The MRT selects message routes. By using the information contained in the route mark, destination signaling point code (DPC), and signaling link selection code (SLS), the MRT selects a signaling link that transfers the signaling messages to a destination signaling point.

–

Message Discrimination (MDC) The MDC receives the messages from L2 to ascertain whether the destination of the messages is the local signaling point. If the destination is the local signaling point, the MDC sends the messages to the MDT. If the destination is not the local signaling point, the MDC sends the messages to the MRT.

–

Message Distribution (MDT) The MDT allocates the messages from the MDC to the user part, the signaling network management part, and the test & maintenance part.

l

Signaling network management part The signaling network management part reconstructs the signaling network, and keeps and recovers the normal transmission of signaling units when the signaling network fails. It consists of three smaller parts: signaling traffic management (STM), signaling link management (SLM), and signaling route management (SRM). –

Signaling Traffic Management (STM) The STM part transmits the signaling data from one link or route to another or to multiple available links or routes when the signaling network fails. It also temporarily reduces signaling traffic in case of congestion at a signaling point.

–

Signaling Link Management (SLM) The SLM part recovers, enables, or disconnects the signaling links in the signaling network. It ensures the provisioning of certain pre-determined link groups. The connections between signaling data links and signaling terminals are normally established through man-machine commands. The operations in the signaling system

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cannot automatically change the previous connection relations. The SLM comprises link test, link prohibition and unprohibion, link switchover and switchback, as well as link activation and deactivation. –

Signaling Route Management (SRM) The SRM ensures reliable exchange of signaling route availability information between signaling points so that signaling routes can be blocked or unblocked. It comprises prohibited transfer, allowed transfer, controlled transfer, and restricted transfer, as well as signaling route group test and signaling route group congestion test.

1.1.4 SCCP Layer on the A Interface The network layer services provided by the SCCP are classified into connectionless service and connection-oriented service. The SCCP, with the help of MTP L3, provides complete network layer functions and reliable services for information exchange in any form. The network layer services provided by the SCCP are classified into connectionless service and connection-oriented service. The connectionless service indicates that an MS does not establish a signaling or connection in advance, but uses the routing function of the SCCP and of the MTP to directly transmit data in the signaling network. The connectionless service is applicable to the transmission of a small quantity of data. The connection-oriented service indicates that an MS establishes a signaling connection in advance and directly transfers data on the signaling connection, instead of using the route selection function of the SCCP. The connection-oriented service is applicable to the transmission of a large quantity of data, and effectively shortens the delay of batch data transmission. The SCCP also performs routing and network management functions. It performs addressing based on the address information such as the DPC, subsystem number (SSN), and global title (GT). The DPC is the destination singling point code used by the MTP. The SSN is the subsystem number. The DPC and the SSN are used to identify different SCCP users, such as the ISUP users, MAP users, TCAP users, and BSSAP users in the same node. They help to compensate the insufficiency of MTP users and to enlarge the addressing scope. The BSS does not use the GT addressing mode, which is not described here. The SCCP performs signaling point state and subsystem state management, active/standby subsystem switchover, status information broadcast, and subsystem state test. The SCCP management (SCMG) maintains the network functions by reselecting a route or adjusting the traffic volume in case of network failure or congestion. The SCCP protocols are defined in ITU-T Q.711–Q.716 recommendations.

1.1.5 BSSAP Layer on the A Interface The BSSAP protocol, which serves as the A interface specification, describes two types of messages, BSSMAP messages and DTAP messages.

Overview of the BSSAP Protocol The BSSAP protocol, which serves as the A interface specification, describes two types of messages, BSSMAP messages and DTAP messages. For DTAP messages, the A interface is merely equivalent to a transport channel. On the BSS side, DTAP messages are directly transmitted to radio channels. On the NSS side, DTAP messages are transmitted to the specific functional processing units. 1-6


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The BSSAP protocol is defined in GSM Rec. 08.08 and 04.08.

Typical Messages The BSSAP protocol, which serves as the A interface specification, describes two types of messages, BSSMAP messages and DTAP messages. l

DTAP messages Based on the functional units that process DTAP messages on the NSS side, the DTAP messages are classified into Mobile Management (MM) messages and Call Control (CC) messages.

l

–

The MM messages include messages related to authentication, Configuration Management (CM) service request, identification request, IMSI detach, location update, MM state, and TMSI reallocation.

–

The CC messages include messages related to alerting, call proceeding, connection, establishment, modification, release, disconnection, notification, state query, and DTMF startup.

BSSMAP messages The BSSMAP messages are classified into connectionless messages and connectionoriented messages. –

Connectionless messages The connectionless messages include block, unblock, handover, resource, reset, and paging messages. The block and unblock messages consist of block, block acknowledge, unblock, and unblock acknowledge messages. The group block and unblock messages consist of group block, block acknowledge, unblock, and unblock acknowledge messages. The handover messages include handover candidate request messages and handover candidate response messages. The resource messages include resource request messages and resource indication messages. The reset messages include reset and reset acknowledge messages.

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Connection-oriented messages The connection-oriented messages include messages related to assignment, handover, clear, and ciphering. The Assignment messages include the assignment request message, assignment complete message, and assignment failure message. The handover messages include the Handover Request, Handover Request Ackowledge, Handover Command, Handover Complete, and Handover Failure messages. The clear messages include the Clear Request and Clear Complete messages. The ciphering messages include the Cipher Mode Command and the Cipher Mode Complete messages.

BSSAP Protocol Functionality The BSSAP protocol functions in connection-oriented mode or connectionless mode. When an MS needs to exchange service-related messages with the NSS on radio channels and there is no MS-related SCCP connection between the BSS and the NSS, a new connection must be established. Issue 01 (2007-11-26)


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1 BSS Signaling Fundamental l

When an MS sends an Access Request message on the RACH, the BSS assigns a dedicated channel (SDCCH or TCH) to the MS. After an L2 connection is established on the assigned SDCCH or FACCH, the BSS starts a connection establishment.

l

When the MSC decides to perform an external handover (the target BSS might be the serving BSS), it must reserve a new DCCH or TCH from the target BSS. Then the MSC starts a connection establishment.

Using the connection and connectionless messages, the BSSAP protocol implements the functionalality described in Table 1-1. Table 1-1 BSSAP protocol functionality Number

Function

Description

1

Assignment

Assignment ensures that dedicated radio resources are properly allocated or reallocated to an MS. The BSS automatically processes the initial random access and immediate assignment of an MS to a DCCH, without the control of the MSC.

2

Block / Unblock Circuit

During an assignment procedure, the MSC needs to select available terrestrial circuits. If the BSS considers that some terrestrial circuits become unavailable or available, it notifies the MSC by initiating a Block/ Unblock procedure.

3

Resource Indication

Resource indication serves to notify the MSC of the following:

4

Reset

l

Number of radio resources that can be used as TCHs in the BSS

l

Number of available and allocated radio resources

l

The MSC does not easily obtain the previous information directly from the MSC-controlled services. The MSC must take the information into consideration when the it decides to perform an external handover.

The purpose of reset is to initialize the BSS or the MSC. For example, if the BSS is faulty and loses all the reference messages about processing, it sends a Reset message to the MSC. Upon receiving the Reset message, the MSC releases the affected calls, deletes the affected reference messages, and sets all the circuits related to the BSS to idle. If the MSC or BSS is only partially faulty, the affected parts can be cleared through the Clear procedure.

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Number

Function

Description

5

Handover Required

The BSS may send the MSC a Handover Required message, requesting the MSC to hand over an MS that are allocated dedicated resources. The handover reasons as are as follows: The BSS detects a radio cause for a handover. The MSC starts a handover candidate enquiry procedure, and the MS is waiting for a handover. Due to congestion, the serving cell must be changed during call establishment, for example, during directed retry. The Handover Required message is resent at a certain interval till one of the following situations occurs:

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l

A Handover Command message is received from the MSC.

l

A Reset message is received.

l

All the communications with MSs are disrupted and the processing is stopped.

l

The processing is complete, for example, the call is cleared.

6

Handover Resource Allocation

Through handover resource allocation, the MSC requests resources from the target BSS based on the handover request, and the target BSS reserves resources and waits for an MS to access the reserved resources (channel).

7

Handover Procedure

Handover procedure is a procedure in which the MSC instructs an MS to access the radio resources in a target cell. When handover is performed, the original dedicated radio resources and terrestrial resources are maintained until the MSC sends a Clear Command message or until the resources are reset.


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Number

Function

Description

8

Radio and Terresterial Resource Release

When a processing is complete, the MSC sends the BSS a Clear Command message, requesting the BSS to release radio resources. Upon receiving the Clear Command message, the BSS starts a clear procedure on the Um interface, sets the configured terrestrial circuits to idle, and responds the MSC with a Clear Complete message. Upon receiving the Clear Complete message, the MSC releases the terrestrial resources. If the BSS needs to release resources, it sends the MSC a Clear Request message. Then the MSC initiates a release procedure to release the specific terrestrial and radio resources.

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9

Paging

The paging to an MS is transmitted through the SCCP connectionless service over the BSSMAP. When the BSS receives a Paging Response message on the Um interface, it establishes an SCCP connection to the MSC. The paging response message, which is carried in the Complete L3 Information, is transmitted to the MSC through this SCCP connection.

10

Flow Control

Flow control ensures stable working state of an entity by preventing the entity from receiving too much traffic. Flow control on the A interface is performed through traffic control at the traffic source. It comprises five levels. It is performed based on subscriber classes.

11

Classmark Update

Classmark update serves to notify a receiving entity of the classmark messages from an MS. Generally, the BSS notifies the MSC upon receiving the classmark messages from an MS. When a handover is complete, the MSC sends the new BSS the classmark messages from the relevant MS on the A interface.

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Cipher Mode Control

The cipher mode control procedure allows the MSC to send the Cipher Mode Control message to the BSS and to start the subscriber equipment and the signaling cipher equipment using a correct ciphering key (Kc).


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Number

Function

Description

13

Queue Indication

The queue indication procedure serves to notify the MSC that the BSS will delay the allocation of some radio resources. The procedure takes effect only when the queuing function is used for traffic channel assignment and traffic channel handover in the BSS.

14

Load Indication

Load indication serves to notify all neighbor BSSs of the traffic state of a cell so that the handover services in an MSC can be controlled as a whole. In a certain period, the neighbor BSSs take the traffic states of neighbor cells into account during a handover.

1.2 Abis Interface The Abis interface lies between the BTS and the BSC. It complies with GSM Rec.08.5X series. The Abis interface is an internal interface of the BSS. The interworking between the BSC and BTS equipment from different manufactures is not available. The terrestrial traffic channels on the Abis interface map the radio traffic channels on the Um interface. 1.2.1 Abis Interface Protocol Model This topic describes the Abis interface protocol model. 1.2.2 Abis Interface Structure The Abis interface supports three types of internal BTS configurations. 1.2.3 Physical Layer on the Abis Interface The physical layer on the Abis interface are 2 Mbit/s PCM links. It provides thirty-two 64 kbit/ s channels. 1.2.4 LAPD Layer on the Abis Interface This topic describes the functions of the LAPD layer on the Abis interface. 1.2.5 L3 Traffic Management Messages on the Abis Interface L3 traffic management messages on the Abis interface enables the MS to exchange information with the BSS or NSS on the Um interface and to perform some radio resource management functions under the control of the BSC. 1.2.6 L3 OM Messages on the Abis Interface This topic describes the L3 OM messages on the Abis interface.

1.2.1 Abis Interface Protocol Model This topic describes the Abis interface protocol model. Figure 1-3 shows the Abis interface protocol model.

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Figure 1-3 Abis interface protocol model BTS

BSC

RR RR BTSM LAPDm LAPD Sign. Layer 1 Layer 1

BTSM LAPD Layer1

BSSAP

SCCP MTP

Abis interface

BTSM: BTS Management

BSSAP: Base Station Subsystem Application Part

SCCP: Signaling Connection Control Part

LAPD: Link Access Procedure on the D Channel

LAPD: Link Access Procedure on the Dm Channel

RR: Radio Resource Management

MTP: Message Transfer Part

The following describes the Abis interface protocol model: l

Layer 1 on the Abis interface is a bottom-layer driver based on the hardware. It transfers data to the physical link.

l

The layer 2 protocol on the Abis interface is based on the LAPD. The LAPD addresses a Transceiver (TRX) or Base Control Function (BCF) through the Terminal Equipment Identifier (TEI). The LAPD uses different logical links for message transmissions. Radio signaling links (RSL) transmit service management messages. Operation and maintenance links (OML) transmit network management messages. Layer 2 management links (L2ML) transmit L2 management messages.

l

RR messages are mapped onto the BSSAP by the BSC. Most RR messages are transparently transmitted by the BTS, except for some messages that must be interpreted and executed. For example, ciphering, random access, paging, and assignment messages are processed by the BTS Management (BTSM) entities in the BSC and in the BTS.

l

Neither the BSC nor the BTS interprets Connection Management (CM) messages and Mobility Management (MM) messages. These messages are transmitted on the A interface by the Direct Transfer Application Part (DTAP). On the Abis interface, DTAP messages are transmitted as transparent messages.

1.2.2 Abis Interface Structure The Abis interface supports three types of internal BTS configurations. Figure 1-4 shows the Abis interface structure. The three types BTS configurations on the Abis interface are as follows:

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l

A single TRX

l

Multiple TRXs connected with the BSC through one physical link

l

Multiple TRXs connected with the BSC through different physical links


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Figure 1-4 Abis interface structure BSS Abis TRX

BTS1

BCF TRX TRX

A MSC

Abis

BTS2

TRX

BSC

BCF Abis TRX TRX

BTS3

TRX TRX BCF

l

Transceiver (TRX) is a functional entity defined in the Public Land Mobile Network (PLMN). It supports eight physical channels of one TDMA frame.

l

The Base Control Function (BCF) is a functional entity that performs common control functions including BTS initialization, software loading, channel configuration, and operation and maintenance.

The following two types of channels are on the Abis interface: l

Traffic channels of 8 kbit/s, 16 kbit/s, and 64 kbit/s, which carry speech or data from radio channels

l

Signaling channels of 16 kbit/s, 32 kbit/s, and 64 kbit/s, which carry signaling between the BSC and an MS, and between the BSC and the BTS

 A TEI is assigned to obtain the unique address of a TRX. Each BCF has a unique TEI. Three different logical links are defined with a TEI, as shown in Figure 1-5. l

RSL: used to support traffic management procedures, one for each TRX

l

OML: used to support network management procedures, one for each BCF

l

L2ML: used to transmit L2 management messages

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Figure 1-5 Logical links on the Abis interface BSC

BTS RSL SAP1=0

TRX

OML SAP1=62

TEI1

L2ML SAP1=63 BCF RSL SAP1=0 LAYER 2

OML SAP1=62

TRX TEI2

L2ML SAP1=63

TEI

BCF RSL SAP1=0 OML SAP1=62

MANA GEMENT

TRX

TEI3

L2ML SAP1=63 BCF OML SAP1=62 L2ML SAP1=63

TEI4

BCF

BCF

1.2.3 Physical Layer on the Abis Interface The physical layer on the Abis interface are 2 Mbit/s PCM links. It provides thirty-two 64 kbit/ s channels. The electrical parameters of the physical layer conform to the ITU-T G.703 recommendations. The BSS is the connection point between radio channels and terrestrial channels. The coding schemes and rates of the two types of channels are different. The coding rate of the radio channels in the BSS is 16 kbit/s, and the rate of the channels on the Abis interface is 64 kbit/s. To save the transmission cost, different multiplexing modes, for example, 10:1, 12:1, and 15:1, are used on the Abis interface.

1.2.4 LAPD Layer on the Abis Interface This topic describes the functions of the LAPD layer on the Abis interface.

Overview The data link layer (L2) on the Abis interface uses the LAPD protocol. It receives data from the physical layer (L1) and provides connection-oriented or connectionless services for L3. The Service Access Point (SAP) of L2 is the connection point for providing services for L3. It is identified by an SAPI. A data link connection endpoint is identified by a data link connection endpoint identifier or a data link connection identifier (DLCI) from the perspective of L2 or L2, respectively. 1-14


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For the information exchange between two or more L3 entities, data links must be established between L3 entities. The co-operation between L2 entities is controlled by the protocol of the peer layer. The message units at L2 are transmitted between L2 entities through L1. Inter-layer service requests are processed through service primitives.

Functions The LAPD reliably transfers end-to-end information between L3 entities through the D channel. Specifically, the LAPD supports: l

Multiple terminal devices between MSs and physical interfaces

l

Multiple L3 entities

The functions of the LAPD layer on the Abis interface are as follows: l

Providing one or multiple data links on the D channel

l

Delimiting, locating, and transparently transmitting frames so that a string of bits transmitted in the form of frames on the D channel can be identified

l

Controlling and keeping the sequence of frames

l

Checking for transmission errors, format errors, and operation errors on data link connections

l

Making recoveries based on the detected transmission errors, format errors, and operation errors

l

Notifying the management layer entities of unrecoverable errors

l

Performing flow control

The LAPD layer on the Abis interface provides the means for information transfer between multiple combinations of data link connection points. The information may be transferred through point-to-point data link connections or broadcast data link connections.

1.2.5 L3 Traffic Management Messages on the Abis Interface L3 traffic management messages on the Abis interface enables the MS to exchange information with the BSS or NSS on the Um interface and to perform some radio resource management functions under the control of the BSC. In terms of processing, traffic management messages are classified into transparent and nontransparent messages.   l

The transparent messages refer to the messages directly forwarded without interpretation or processing by the BTS.

l

The non-transparent messages refer to the messages that are transmitted between the BSC and the BTS and that must be processed and structured by the BTS.

In terms of functions, traffic management messages are classified into the following: l

Radio link layer management messages that are used to manage the data link layer on radio channels

l

Dedicated channel management messages that used to manage dedicated channels such as the SDCCH and TCH

l

Common control channel management messages that are used to manage common control channels

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TRX management messages that are used to manage TRXs NOTE

The transparency and group of traffic management messages are determined by the message discriminator at the header of the messages. l

Radio link management procedures Radio link management procedures consist of the following:

l

–

Link establishment indication procedure: used by the BTS to indicate to the BSC that an MS-originated multi-frame-mode link establishment is successful. Upon receiving the indication from the BTS, the BSC establishes an SCCP link to the MSC.

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Link establishment request procedure: used by the BSC to request the establishment of a multi-frame link on a radio channel.

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Link release indication procedure: used by the BTS to indicate to the BSC that an MSinitiated radio link release is complete.

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Link release request procedure: used by the BSC to request the release of a radio link.

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Transmission of transparent L3 messages on the Um interface in acknowledged mode: used by the BSC to request the transmission of transparent L3 messages to an MS on the Um interface in acknowledged mode

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Reception of transparent L3 messages on the Um interface in acknowledged mode: used by the BTS to notify the BSC that transparent L3 messages are received on the Um interface in acknowledged mode

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Transmission of transparent RIL3 messages on the Um interface in unacknowledged mode: used by the BSC to request the transmission of transparent L3 messages to an MS on the Um interface in unacknowledged mode

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Reception of transparent RIL3 messages on the Um interface in unacknowledged mode: used by the BTS to notify the BSC that transparent L3 messages are received on the Um interface in unacknowledged mode

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Link error indication procedure: used by the BTS to notify the BSC in case of errors at the radio link layer

Dedicated channel management procedures The dedicated channel management procedures consist of the following:

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Channel activation procedure: used by the BSC to request the BTS to activate a dedicated channel for an MS. Then the BSC assigns the activated channel to the MS through an Immediate Assignment, Assignment Command, Additional Assignment, or Handover Command message.

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Channel mode modification procedure: used by the BSC to request the BTS to change the mode of an activated channel.

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Handover detection procedure: used between the target BTS and the target BSC to detect the access of an MS being handed over.

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Ciphering mode command procedure: used to start the ciphering procedure defined in GSM Rec. 04.08.

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Measurement report procedure: consists of the mandatory basic measurement report procedure and optional measurement report preprocessing procedure. The BTS reports all the parameters related to handover decisions to the BSC through this procedure.

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SACCH deactivation procedure: used by the BSC to deactivate the SACCH related to a TRX according to the Channel Release procedure defined in GSM Rec. 04.08. Huawei Technologies Proprietary

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l


–

Radio channel release procedure: used by the BSC to release a radio channel that is no longer needed.

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MS power control procedure: used by the BSS to control the transmit power of an MS for which a channel is already activated. The power control decision must be performed in the BSC. It can also be performed in the BTS.

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BTS transmit power control procedure: used by the BSS to control the transmit power of a TRX with an activated channel. The BTS transmit power control decision must be performed in the BSC. It can also be performed in the BTS.

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Connection failure procedure: used by the BTS to notify the BSC that an activated dedicated channel is unavailable.

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Physical context request procedure: used by the BSC to obtain the information about the physical context of a radio channel prior to a channel change. It is an optional procedure.

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SACCH information modification procedure: used by the BSC to request the BTS to change the filling system information on a specific SACCH.

Common channel management procedures The common channel management procedures consist of the following:

l

–

MS-initiated channel request procedure: triggered when a TRX detects a Channel Request message from an MS

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Paging procedure: used to page an MS on a specific paging sub-channel This procedure is used in an MS terminating call establishment procedure. It is initiated by the MSC through the BSC. Based on the IMSI of the called MS, the BSC determines the paging group to be used. Then it sends to the BTS the paging group number together with the identity of the MS.

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Immediate assignment procedure: used by the BSC to immediately assign a dedicated channel to an MS when the MS accesses the BTS.

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Delete indication procedure: used by the BTS to notify the BSC that an Immediate Assign Command message is deleted due to AGCH overload.

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CCCH load indication procedure: used by the BTS to notify the BSC of the load on a specified CCCH if the load exceeds the preset threshold on the OMC. The indication period is also set on the OMC.

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Broadcast information modification procedure: used by the BSC to notify the BTS of the new system information to be broadcast on the BCCH.

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Short message service cell broadcast procedure: used by the BSC to request short message service cell broadcast messages from the BTS.

TRX management procedures The TRX management procedures consist of the following:

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SACCH filling information modify procedure: used by the BSC to notify the BTS of the new system information to be used as filling information on all downlink SACCHs

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Radio resource indication procedure: used by the BTS to notify the BSC of the interference levels on the idle channels of a TRX

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Flow control procedure: used by the Frame Unit Controller (FUC) in a TRX to notify the BSC of the TRX overload due to CCCH overload, AGCH overload, or TRX processor overload

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Error reporting procedure: used by the BTS to notify the BSC of the detected downlink message errors, which cannot be reported through any other procedure Huawei Technologies Proprietary

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1.2.6 L3 OM Messages on the Abis Interface This topic describes the L3 OM messages on the Abis interface.

OM Information Model The OM information model consists of the following: l

Management objects The management objects are site, cell, carrier (TRX), and channel. Figure 1-6 shows the management objects. Figure 1-6 Management objects SITE

CELL 0

CELL 1

TRX0

TRX1

BTS

Chann el 0

l

Chann el 1

CELL n

…

…

TRXm

TRX

…

Chanel 7

Addressing of management objects Network management messages are addressed through the classes and instances of the management objects. Each object instance in the BTS has a complete L2 connection description. The first established connection is assigned a semi-permanent or permanent default TEI. The subsequent connections are assigned the TEIs provided during the establishment of TEI procedures. Object instances can also use L3 addresses. The mixed use of L2 addressing and L3 addressing enables one site to have one or multiple physical links.

l

Management object state A management object can be in three states, the administrative state, operational state, and availability state. For details, see Table 1-2, Table 1-3, and Table 1-4. The available state further describes the operational state, and only the BSC controls the administrative state. Table 1-2 Administrative State

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Status

Description

Locked

The BSC has disconnected all the calls passing this management object, and no new services can be connected to this object.


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Status

Description

Shut Down

No new services can be connected to this management object, and ongoing calls are maintained.

Unlocked

New services can be connected to this management object.

Table 1-3 Operational State Status

Description

Disabled

Resources are totally inoperable and can no longer provide services for MSs.

Enabled

Resources are partially or fully operable.

Table 1-4 Available State Status

Description

In Test

The resource is undergoing a test procedure. The operational state is disabled.

Failed

The resource has an internal fault that prevents it from operating. The operational state is disabled.

Power Off

The resource requires power and is not powered on. The operational state is disabled.

Off Line

The resource requires automatic or manual operations to make it available for use. The operational state is disabled.

Dependency

The resource cannot operate because some other resources on which it depends are unavailable. The operational state is disabled.

Degraded

The service is degraded due to some reasons such as speed or capacity. The operational state is enabled.

Not Installed

The hardware or software of the management object is not installed. The operational state is disabled.

Basic Procedures All procedures are based on formatted OM messages. Most formatted OM messages initiated by the BSC or the BTS require the peer L3 to respond with formatted OM messages. This pair of formatted OM messages or a formatted OM message that does not require a response is called a basic procedure. Issue 01 (2007-11-26)


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All formatted OM messages are sent on L2 in the form of I frames. A group of messages, also called structured procedures, are based on the combination of some basic procedures. For a specific object instance, if a certain basic procedure is not complete, the system does not start the subsequent basic procedures. When there is no response to a formatted OM message from the peer L3 upon L3 timer expiry, the basic procedure is considered as not "completed." When there is no response (ACK or NACK) in the previous basic procedure upon L3 timeout, no subsequent basic procedure is sent to this object instance. The default value for L3 timeout is 10 seconds. If part of an original message is not understood or supported, the entire message is discarded. An ACK message from an object instance indicates an affirm response. It is used to notify the sender that the command is executed or will be executed. An NACK message from an object instance indicates a disaffirm response. It is used to notify the sender of the unsuccessful execution of the command and of the failure cause. The basic procedures are classified into the following: l

Software loading management procedure

l

Abis interface management procedure

l

Transmission management procedure

l

Abis interface management procedure

l

Test management procedure

l

State management and event report procedure

l

Equipment state management procedure

l

Other procedures

1.3 Um Interface The Um interface lies between an MS and the BTS. It is used for the interworking between the MS and the fixed part of the GSM system. The links on the Um interface are radio links. The Um interface transmits the information about radio resource management, mobility management, and connection management. 1.3.1 Physical Layer on the Um Interface The physical layer (L1) is the bottom layer on the Um interface. It defines the radio access capabilities of the GSM and provides basic radio channels for information transfer at higher layers. 1.3.2 LAPD Layer on the Um Interface The data link layer (L2) is the middle layer on the Um interface. It uses the LAPDm protocol. It defines various data transmission structures for controlling data transmission. 1.3.3 L3 Entity on the Um Interface The L3 entity consists of many functional program blocks. These program blocks transfer message units between all L3 entities and between L3 and its adjacent layers.

1.3.1 Physical Layer on the Um Interface The physical layer (L1) is the bottom layer on the Um interface. It defines the radio access capabilities of the GSM and provides basic radio channels for information transfer at higher layers. 1-20


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L1 is the bottom layer on the Um interface. It provides physical links for transmitting bit streams. It also provides higher layers with various logical channels, including traffic channels and signaling channels. Each logical channel has its own logical access point. Figure 1-7 shows the interfaces between L1 and the data link layer, the radio resource management sublayer (RR) of L3, and other functional units. Figure 1-7 Interfaces of L1 on the Um interface Radio resource management (3) Data link layer MPH primitive

Other functional units

PH primitive

TCH

Physical layer

L1 provides the following services: l

Access capability L1 provides a series of limited logical channels for transmission service. Logical channels are multiplexed on physical channels. Each TRX has eight physical channels. Through data configuration, logical channels are mapped to physical channels.

l

Bit error detection L1 provides error protection transmission, including error detection and correction.

l

Cyphering Based on a selected ciphering algorithm, the BSS ciphers the bit sequence.

1.3.2 LAPD Layer on the Um Interface The data link layer (L2) is the middle layer on the Um interface. It uses the LAPDm protocol. It defines various data transmission structures for controlling data transmission. L2 provides reliable dedicated data links between an MS and the BTS. It uses the LAPDm protocol that evolves from the LAPD protocol. The SAP of L2 is the connection point for providing services for L3. An SAP is identified by an SAPI. Each SAP is associated with one or multiple DLCEPs. Currently, two SAPI values, 0 (main signaling) and 3 (short messages), are defined in the LAPDm protocol.

Functions LAPDm transfers information between L3 entities through the Dm channel on the Um interface. LAPDm supports multiple L3 entities, L1 entities, and signaling on BCCH, PCH, AGCH, and DCCH. NOTE

The Dm channel is a generic term for all the signaling channels on the Um interface in the GSM system. For example, the Dm channel can be PCH or BCCH.

LAPDm performs the following functions: l

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Providing one or more data link connections (DLCs) on the Dm channel. Each DLC is identified by a data link connection identifier (DLCI). Huawei Technologies Proprietary

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Allowing frame type identification

l

Allowing L3 message units to be transparently transmitted between L3 entities

l

Performing sequence control to maintain the order of the frames transmitted through a DLC

l

Detecting format errors and operation errors on data links

l

Performing flow control

l

Establishing a contention resolution on a data link after an access request is detected on the RACH

Operation Type L2 transmits L3 information in unacknowledged and acknowledged modes. One Dm channel can be in both modes at the same time. l

Unacknowledged mode In unacknowledged mode, L3 information is transferred in Unnumbered Information (UI) frames. L2 does not acknowledge the UI frames or perform flow control or error correction. The unacknowledged mode is applicable to different types of control channels except the RACH.

l

Acknowledged mode In acknowledged mode, L3 information is transferred in numbered Information (I) frames. L2 acknowledges the I frames. It performs error correction by resending unacknowledged frames. When L2 fails to correct errors, it informs the specific L3 entity of the correction failure. Flow control procedures are also defined. The acknowledged mode is applicable to the DCCH.

Information Transfer Mode Information is transferred in different modes on different channels. l

Information transfer on the BCCH: The BCCH transfers the broadcast messages from the BTS to the MS. Only the acknowledged mode can be used on the BCCH.

l

Information transfer on the PCH+AGCH: These channels transfer messages from the BTS to the MS. Only the unacknowledged mode is applicable to the PCH+AGCH.

l

Information transfer on the DCCH: Either the acknowledged or the unacknowledged mode can be used. The transfer mode is determined by L3.

Data Link Release L2 release is initiated by L3. The data links in frame mode are released in the following modes: l

Normal release The BTS and the MS exchange DISC frames and UA frames or DM frames.

l

Local release No frames are exchanged. Generally used in abnormal cases.

1.3.3 L3 Entity on the Um Interface The L3 entity consists of many functional program blocks. These program blocks transfer message units between all L3 entities and between L3 and its adjacent layers. 1-22


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Overview The L3 entity consists of many functional program blocks. These program blocks transfer message units between all L3 entities and between L3 and its adjacent layers. L3 performs the following functions: l

Establishing, operating, and releasing dedicated radio channels (RR)

l

Performing location update, authentication, and TMSI reallocation (MM)

l

Establishing, maintaining, and terminating circuit-switched calls (CC)

l

Supporting supplementary services (SS)

l

Supporting short messages service (SMS)

L3 uses L3 signaling protocols between the MS and the network. Here the functions of different entities in the BSS are not taken into consideration. L3 and its supported lower layers, therefore, provide the Mobile Network Signaling (MNS) service to the upper layers. The service interfaces between L3 and higher layers and the interactions between the adjacent sublayers in L3 are described in primitives and parameters. The three sublayers in L3 perform information exchange between peer entities.

Structure and Functions L3 consists of three sublayers. The CM sub-layer (the highest sub-layer) consists of three functional entities: Call Control (CC), Short Message Service (SMS), and Supplementary Service (SS). In total, L3 on the Um interface has five functional entities. The five functional entities perform the following functions: l

Radio Resource Management (RR) Establishing, maintaining, and releasing physical channels and logical channels, as well as performing cross-cell connection upon the request from the CM sublayer

l

Mobility Management (MM) Performing MS-specific functions and notifying the network when an MS is activated and deactivated, or when the location area of an MS changes. It is also responsible for the security of activated radio channels.

l

Call Control (CC) Performing all necessary functions to establish or release CS connections

l

Supplementary Service (SS) Performing all necessary functions to support GSM supplementary services

l

Short Messages Service (SMS) Performing all necessary functions to support point-to-point GSM short message services

In addition to the previous functions, L3 performs functions related to the transmission of messages, for example, multiplexing and splitting. These functions are defined in the Radio Resource Management and Mobility Management. They route messages according to the protocol discriminator (PD) and transaction identifier (TI), which are part of the message header. The routing function of the MM enables the MM to route the messages of the CM entities and the messages of the MM entity to the RR service access point (RR-SAP), and multiplexes the messages in case of concurrent transactions. The routing function of the RR distributes the tobe-sent messages according to their PD and the actual channel configuration. The messages provided at different service access points of layer 2 are split by the RR routing function according to the PD. If a message belongs to the RR sublayer, this message is transmitted Issue 01 (2007-11-26)


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to the RR entity based on the TI. The other messages are sent to the MM sublayer through the RR-SAP. If a message belongs to the MM sublayer, the message is transmitted to the MM entity based on the TI. The other messages are sent to the CM sublayer through the MM-SAPs, and then to the CM entities. Figure 1-8 shows the L3 signaling protocol model on the Um interface. Figure 1-8 L3 signaling message processing procedure Mobile network services

MNCC-SAP

CC

MNSS-SAP

MNSMS-SAP

S S

SM S MMSS-SAP

MMCC-SAP

MMSMS-SAP

MMREG -SAP MM CC

Layer 3 signaling

MM

SS

SMS

RR-SAP RR

RR PD RR

SDCCH SACCH

SAPI 3 RACCH BCCH AGCH+PCH SDCCH SACCH FACCH

SAPI 0

The RR sublayer at the bottom receives the services from L2 through various service access points (that is, various types of channels) of L2, and provides services to the MM sublayer through RR-SAP. The MM sublayer provides services to different entities through different SAPs: to the CC through MMCC-SAP, to the SS through MMSS-SAP, to the SMS through MMSMS-SAP, and to the high layer through MMREG-SAP. The three independent entities (CC, SS, and SMS) of the CM sublayer provide services to higher layers through MNCC-SAP, MNSS-SAP, and MNSMS-SAP respectively.

Service Feature L3 on the MS side provides the following services: l

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Registration services, that is, IMSI attach and detach


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l

Call control services, including normal establishment of MS originating calls, emergency establishment of MS originating calls, call hold, call termination, and support for callrelated supplementary services

l

Support for call independent supplementary services

l

Support for short messages service

L3 on the network side provides the following services: l

Call control services, including call establishment, call hold, call termination, and support for call-related supplementary services

l

Support for call independent supplementary services

l

Support for short messages service

L3 provides the following services between the MS and the network: l

For the services provided by the RR, see Figure 1-9. These services are provided to the MM through RR-SAP. They are used to set up control channel connections and traffic channel connection, indicate ciphering mode, release control channel connections, and transmit control data.

l

For the services provided by the MM, see Figure 1-10. These services are used to manage the three entities (CC, SS, and SMS) of the CM sublayer. Figure 1-9 Services provided by the RR sublayer MS side

Network side

Mobile management sublayer RRprimitive RR SAP Protocol of the peer layer of the RR sublayer

Radio resource management sublayer

Figure 1-10 Services provided by the MM sublayer MS side CC

SS

Network side SMS

Mobile management sublayer

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CC

Protocol of the peer layer of the MM sublayer

SS

SMS

Mobile management sublayer


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2 BSS Signaling Tracing

2

BSS Signaling Tracing

About This Chapter This describes the BSS signaling tracing, which consists of the signaling tracing on the Um interface, Abis interface, A interface, Pb interface, and BSC-CBC interface, and single user signaling tracing. 2.1 Tracing the Messages on the Um Interface This describes how to trace all the layer 3 signaling messages on the Um interface through the LMT. 2.2 Tracing Messages on the Abis Interface This topic describes how to trace the RSL, OML, ESL, LAPD messages on the Abis interface. 2.3 Tracing the Messages on the A Interface This topic describes how to trace the BSSAP, MTP2, MTP3, and SCCP messages on the A interface. 2.4 Tracing Messages on the Pb Interface This topic describes how to trace the application messages and LAPD messages on the Pb interface. 2.5 Tracing the Messages on the BSC-CBC Interface This describes how to trace signaling messages of the interfaces between the BSC and CBC through the LMT. 2.6 Tracing User Messages This describes how to trace signaling messages on the interfaces of the specified user through the LMT.

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2.1 Tracing the Messages on the Um Interface This describes how to trace all the layer 3 signaling messages on the Um interface through the LMT.

Prerequisite l

The LMT runs normally.

l

The communication between the BSC and the BTS is normal.

Context Tracing the messages on the Um interface includes the following: l

Tracing layer 3 messages on the Um interface

l

Supporting filtering messages based on TRXs or a maximum of 16 cells

l

The data of the BSSAP messages on the A interface can be browsed.

Procedure Step 1 On the Trace & Monitor tab page, choose Trace > Trace the Message at Um Interface. A dialog box is displayed, as shown in Figure 2-1. Figure 2-1 Tracing messages on the Um interface (set TRX as the filter condition)

Step 2 Set Filter Condition and Color. NOTE

When the Filter Condition is set to TRX or Cell, the execution interfaces are different. In this topic, the instance when the Filter Condition is set to TRX is illustrated. Max Number: 16 indicates that the maximum number of cells that can be selected is 16.

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Step 3 Set the Tracing Mode to start the tracing. l

If the Tracing Mode is set to Report, and click OK, the messages on the Um interface are traced in the Report mode. The tracing result is shown in Figure 2-2.

l

If the Tracing Mode is set to Save on Server, and click OK, the messages on the Um interface are traced in the Save on Server mode. The LMT no longer displays the tracing messages.

Figure 2-2 Results of tracing messages on the Um interface

----End

2.2 Tracing Messages on the Abis Interface This topic describes how to trace the RSL, OML, ESL, LAPD messages on the Abis interface. 2.2.1 Tracing the RSL Messages on the Abis Interface This describes how to trace all the signaling messages on the Abis interface through the LMT. 2.2.2 Tracing the OML Messages on the Abis Interface This describes how to trace all the OML messages at Abis interface through the LMT. 2.2.3 Tracing the ESL Messages on the Abis Interface This describes how to trace all the ESL messages at Abis interface through the LMT. 2.2.4 Tracing the LAPD Messages on the Abis Interface This describes how to trace the LAPD messages on the Abis interface through the LMT.

2.2.1 Tracing the RSL Messages on the Abis Interface This describes how to trace all the signaling messages on the Abis interface through the LMT.

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Prerequisite l


l


Context Tracing the RSL messages on the Abis interface includes the following: l

Tracing the RSL messages on the Abis interface based on TRXs or cells. Tracing messages based on TRXs or cells (a maximum of 16 cells).

l

Tracing the RSL messages based on message types, such as measurement report, channel request, paging, RLM, and TRXM.

l


CAUTION After the BTS connected to the Abis interface is moved manually, close the message trace of this type and restart the message trace function.

Procedure Step 1 Click the Trace & Monitor tab. A dialog box is displayed, as shown in Figure 2-3.

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Figure 2-3 Trace & Monitor tab page

Step 2 Choose Trace > Trace the Message at Abis Interface > RSL Message. A dialog box is displayed, as shown in Figure 2-4.

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Figure 2-4 Trace the RSL Message at Abis Interface dialog box

Step 3 Set Message Type, Filtering Condition, Color, and Tracing Mode. Step 4 Click OK.

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l

In Figure 2-4, if the Tracing Mode is set to Save on Server, click OK, the RSL messages on the Abis interface are traced in the Save on Server mode. The LMT no longer receives the tracing messages.

l

In Figure 2-4, if the Tracing Mode is set to Report, click OK, the RSL messages are traced in the Report mode. The tracing result is shown in Figure 2-5.


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Figure 2-5 Tracing the RSL messages on the Abis interface

----End

2.2.2 Tracing the OML Messages on the Abis Interface This describes how to trace all the OML messages at Abis interface through the LMT.

Prerequisite l


l


Context Tracing the OML messages on the Abis interface includes the following: l

Tracing the OML messages at Abis interface based on sites (a maximum of 16 sites)

l

Tracing the OML messages at Abis interface based on message types, such as public messages and OM messages.

l



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Step 2 Choose Trace > Trace the Message at Abis Interface > OML Message. A dialog box is displayed, as shown in Figure 2-7. Figure 2-7 Trace the OML Message at Abis Interface dialog box

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Step 3 Set Message Type, Color, and Tracing Mode. Select cells from the Candidate Cells box and add them to the Selected Cells box. Step 4 Click OK. l

In Figure 2-7, if the Tracing Mode is set to Save on Server, click OK, the OML messages on the Abis interface are traced in the Save on Server mode. The LMT no longer receives the tracing messages.

l

In Figure 2-7, if the Tracing Mode is set to Report, click OK, the OML messages are traced in the Report mode. The tracing result is shown in Figure 2-8.

Figure 2-8 Tracing the OML messages on the Abis interface

----End

2.2.3 Tracing the ESL Messages on the Abis Interface This describes how to trace all the ESL messages at Abis interface through the LMT.

Prerequisite l


l


Context Tracing the ESL messages on the Abis interface includes the following: l

Tracing the ESL messages on the Abis interface based on sites (a maximum of 16 sites)

l

Tracing the ESL messages on the Abis interface based on message types, such as public messages and OM messages.

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Procedure Step 1 Click the Trace & Monitor tab. A dialog box is displayed, as shown in Figure 2-9. Figure 2-9 Trace & Monitor tab page

Step 2 Choose Trace > Trace the Message at Abis Interface > ESL Message. A dialog box is displayed, as shown in Figure 2-10.

2-10


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Figure 2-10 Trace the ESL Message at Abis Interface dialog box

Step 3 Set Message Type, Color, and Tracing Mode. Select cells from the Candidate Cells box and add them to the Selected Cells box. Step 4 Click OK. l

In Figure 2-10, if the Tracing Mode is set to Save on Server, click OK, the OML messages on the Abis interface are traced in the Save on Server mode. The LMT no longer receives the tracing messages.

l

In Figure 2-10, if the Tracing Mode is set to Report, click OK, the ESL messages are traced in the Report mode. The tracing result is shown in Figure 2-11.

Figure 2-11 Tracing the ESL messages on the Abis interface

----End Issue 01 (2007-11-26)


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2.2.4 Tracing the LAPD Messages on the Abis Interface This describes how to trace the LAPD messages on the Abis interface through the LMT.

Prerequisite l


l


Context Tracing the LAPD messages on the Abis interface includes the following: l

Tracing the LAPD messages on the Abis interface; supporting tracing TRXs and BTSs

l

Tracing link messages based on the link number of the TRX

l

Tracing link messages based on the link number of the BTS

l



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Step 2 Choose Trace > Trace the Message at Abis Interface > LAPD Message. A dialog box is displayed, as shown in Figure 2-13.

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Figure 2-13 Trace the LAPD Message at Abis Interface dialog box

Step 3 Set the parameters in the Link Type, Location, Color, and Tracing Mode areas. Step 4 Click OK.

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l

In Figure 2-13, if the Tracing Mode is set to Save on Server, click OK, the LAPD messages on the Abis interface are traced in the Save on Server mode. The LMT no longer receives the tracing messages.

l

In Figure 2-13, if the Tracing Mode is set to Report, click OK, the LAPD messages are traced in the Report mode. The tracing result is shown in Figure 2-14.


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Figure 2-14 Tracing the LAPD messages on the Abis interface

----End

2.3 Tracing the Messages on the A Interface This topic describes how to trace the BSSAP, MTP2, MTP3, and SCCP messages on the A interface. 2.3.1 Tracing the BSSAP Messages on the A Interface This describes how to trace all the layer signaling messages on the A interface, such as connection-oriented messages and non-connection-oriented messages. 2.3.2 Tracing the MTP2 Messages on the Interface This describes how to trace all the layer 2 messages on the A interface, except the FISU message. 2.3.3 Tracing the MTP3 Messages on the A Interface This describes how to trace all the layer 3 messages at A interface. 2.3.4 Tracing the SCCP Messages on the A Interface This describes how to trace the SCCP messages on the A interface based on the DPC, the SCCP user message, and the MTP3 primal message.

2.3.1 Tracing the BSSAP Messages on the A Interface This describes how to trace all the layer signaling messages on the A interface, such as connection-oriented messages and non-connection-oriented messages.

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Prerequisite l


l

The communication between the BSC and the MSC is normal.

Context Tracing the BSSAP messages on the A interface includes the following: l

Tracing the BSSAP messages traces all the layer 3 signaling messages on the A interface, such as connection-oriented messages and non-connection-oriented messages.

l

For connection-oriented messages, the BSSAP messages on the A interface are traced based on cells. The maximum number of cells for this purpose is 16.

l

For non-connection-oriented messages, the BSSAP messages on the A interface are traced based on the message type, including DTAP, BSSMAP, and Paging messages.

l



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Step 2 Choose Trace > Trace the Message at A Interface > BSSAP Message. A dialog box is displayed, as shown in Figure 2-16. Figure 2-16 Trace the BSSAP Message at A Interface dialog box

Step 3 Set Message Type, Color, Tracing Mode, and Site. Select cells from the Candidate Cells box and add them to the Selected Cells box. Step 4 Click OK. l

In Figure 2-16, if the Tracing Mode is set to Save on Server, click OK, the BSSAP messages are traced in the Save on Server mode. The LMT no longer receives the tracing messages.

l

In Figure 2-16, if the Tracing Mode is set to Report, click OK, the BSSAP messages are traced in the Report mode. The tracing result is shown in Figure 2-17.

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Figure 2-17 Tracing the BSSAP messages at A interface

----End

Postrequisite In Figure 2-17, right-click the message to be analyzed. A shortcut menu is displayed, as shown in Figure 2-18. Figure 2-18 Trace the BSSAP Message at A Interface (1)

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NOTE

As shown in Figure 2-17, the shortcut menu provides the following options: l

To clear the displayed messages at A interface, choose Clear Message.

l

To stop scrolling the displayed messages at A interface, choose Stop Scroll.

l

To stop the current tracing task, choose Stop Trace.

l

To restart the tracing, choose Restart Trace.

l

To view the established tracing task, choose View Task.

l

To search for the specified character string, choose Search.

l

To save the selected messages at A interface, choose Save Selection.

l

To save all the traced messages at A interface, choose Save All.

2.3.2 Tracing the MTP2 Messages on the Interface This describes how to trace all the layer 2 messages on the A interface, except the FISU message.

Prerequisite l


l


Context Tracing the MTP2 messages on the A interface includes the following: l

Tracing the layer 2 messages on the A interface, not including the FISU message

l

Tracing the MTP2 messages based on the specified subrack, slot, and link number.

l

Filtering MTP2 messages based on message types, such as the LSSU message and MSU message.

l



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Step 2 Choose Trace > Trace the Message at A Interface > MTP2 Message. A dialog box is displayed, as shown in Figure 2-20.

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Figure 2-20 Trace the MTP2 Message at A Interface dialog box

Step 3 Set Message Type, Location, Tracing Mode, and Color. Step 4 Click OK. l

In Figure 2-20, if the Tracing Mode is set to Save on Server, click OK, the MTP2 messages are traced in the Save on Server mode. The LMT no longer receives the tracing messages.

l

In Figure 2-20, if the Tracing Mode is set to Report, click OK, the MTP2 messages are traced in the Report mode. The tracing result is shown in Figure 2-21.

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Figure 2-21 Tracing the MTP2 messages on the A interface

----End

2.3.3 Tracing the MTP3 Messages on the A Interface This describes how to trace all the layer 3 messages at A interface.

Prerequisite l


l

The communication between the LMT and the BSC is normal.

l

The MTP3 links are configured.

Context Tracing the MTP3 messages on the A interface includes the following: l

Tracing the MP3 messages based on the link number, link set, and DSP.

l

Tracing the MP3 messages based on the message types, such as the SNM, SLT, MT, and L2_CHANGE.


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Step 2 Choose Trace > Trace the Message at A Interface > MTP3 Message. A dialog box is displayed, as shown in Figure 2-23.

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Figure 2-23 Tracing the MTP3 Messages at A Interface

Step 3 Set Message Type, Tracing Type, Location, Message Filter, Tracing Mode, and Color. Step 4 Click OK.

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l

In Figure 2-23, if the Tracing Mode is set to Save on Server, click OK, the MTP3 messages are traced in the Save on Server mode. The LMT no longer receives the tracing messages.

l

In Figure 2-23, if the Tracing Mode is set to Report, click OK, the MTP3 messages are traced in the Report mode. The tracing result is shown in Figure 2-24.


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Figure 2-24 Tracing the MTP3 messages at A interface

----End

2.3.4 Tracing the SCCP Messages on the A Interface This describes how to trace the SCCP messages on the A interface based on the DPC, the SCCP user message, and the MTP3 primal message.

Prerequisite l


l

The communication between the LMT and the BSC is normal.

l

The SCCP link is configured.


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Step 2 Choose Trace > Trace the Message at A Interface > SCCP Message. A dialog box is displayed, as shown in Figure 2-26.

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Figure 2-26 Tracing the SCCP Messages on the A Interface

Step 3 Set the parameters in the Tracing Type, Location, Tracing Mode, and Color areas. Step 4 Click OK. l

In Figure 2-26, if the Tracing Mode is set to Save on Server, click OK, the SCCP messages are traced in the Save on Server mode. The LMT no longer receives the tracing messages.

l

In Figure 2-26, if the Tracing Mode is set to Report, click OK, the SCCP messages are traced in the Report mode. The tracing result is shown in Figure 2-27.

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Figure 2-27 Tracing the SCCP messages on the A interface

----End

2.4 Tracing Messages on the Pb Interface This topic describes how to trace the application messages and LAPD messages on the Pb interface. 2.4.1 Tracing the Application Messages on the Pb Interface This describes how to trace the application messages on the the Pb interface through the LMT. 2.4.2 Tracing the LAPD Messages on the Pb Interface This describes how to trace the layer 2 messages on the Pb interface through the LMT. You can trace the LAPD messages on the Pb interface based on the specified link.

2.4.1 Tracing the Application Messages on the Pb Interface This describes how to trace the application messages on the the Pb interface through the LMT.

Prerequisite l


l


Context Tracing the application messages on the Pb interface includes the following: 2-28


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l

Tracing application messages on the Pb interface

l

Tracing application messages on the Pb interface for the specified PCU.

l

Tracing application messages on the Pb interface based on cells (a maximum of 16 cells).

l

Tracing PAGING messages, CONFUSION messages, PCIC messages, and other messages

l



Step 2 Choose Trace > Trace the Message at Pb Interface > Application Message. A dialog box is displayed, as shown in Figure 2-29.

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2-29



Figure 2-29 Trace the Application Message at Pb Interface dialog box

Step 3 Set Message Type, Location, Color, and Tracing Mode. Select cells from the Candidate Cells box and add them to the Selected Cells box. Step 4 Click OK. l

In Figure 2-29, if the Tracing Mode is set to Report, click OK, the application messages are traced in the Report mode.

l

In Figure 2-29, if the Tracing Mode is set to Save on Server, click OK, the application messages on the Pb interface are traced in the Save on Server mode. The LMT no longer receives the tracing messages.

----End

2.4.2 Tracing the LAPD Messages on the Pb Interface This describes how to trace the layer 2 messages on the Pb interface through the LMT. You can trace the LAPD messages on the Pb interface based on the specified link.

Prerequisite l


l


Context Tracing the LAPD messages on the Pb interface includes the following: l

Tracing layer 2 messages on the Pb interface

l


Procedure Step 1 Click the Trace & Monitor tab. A dialog box is displayed, as shown in Figure 2-30. 2-30


Issue 01 (2007-11-26)




Step 2 Choose Trace > Trace the Message at Pb Interface > LAPD Message. A dialog box is displayed, as shown in Figure 2-31.

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2-31



Figure 2-31 Trace the LAPD Message at Pb Interface dialog box

Step 3 Set the parameters in the Message Type, Color, and Tracing Mode areas. Step 4 Click OK. l

In Figure 2-31, if the Tracing Mode is set to Report, click OK, the application messages are traced in the Report mode.

l

In Figure 2-31, if the Tracing Mode is set to Save on Server, click OK, the LAPD messages on the Pb interface are traced in the Save on Server mode. The LMT no longer receives the tracing messages.

----End

2.5 Tracing the Messages on the BSC-CBC Interface This describes how to trace signaling messages of the interfaces between the BSC and CBC through the LMT.

Prerequisite

2-32

l


l

The communication between the BSC and the BTS is normal. Huawei Technologies Proprietary

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Context Tracing the messages on the BSC-CBC interface includes the following: l

Tracing signaling messages of the interfaces between the BSC and CBC through the LMT.

l


Procedure Step 1 On the Trace & Monitor tab page, choose Trace > Trace the Message at BSC-CBC Interface. A dialog box is displayed, as shown in Figure 2-32. Figure 2-32 Trace the Message at BSC-CBC Interface dialog box

Step 2 Set Tracing Mode and Color, and then click OK. l

If the Tracing Mode is set to Report, the BSC-CBC interface messages are traced in the Report mode.

l

If the Tracing Mode is set to Save on GBAM. The BSC-CBC interface messages are traced in the Save on Server mode. The LMT no longer displays the tracing messages.

----End

2.6 Tracing User Messages This describes how to trace signaling messages on the interfaces of the specified user through the LMT.

Prerequisite l


l


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2-33



Context Tracing the user messages includes the following: l

Tracing signaling messages on the A interface, Abis interface, Pb interface, Um interface, and BSC-CBC interface

l

Tracing messages on the specified interface

l

Tracing the specified traced users through IMSI, IMEI, TMSI, MSISDN, or channel

l


Procedure Step 1 On the Trace & Monitor tab page, choose Trace > Trace User Message. A dialog box is displayed, as shown in Figure 2-33. Figure 2-33 Trace User Message dialog box

Step 2 Set Interface Type, and Color, type the IMSI, TMSI, MSISDN, IMEI, or channel of the user to be traced. Step 3 Set the Tracing Mode to start the tracing. l

2-34

If the Tracing Mode is set to Report, and click OK, the interface messages of the user are traced in the Report mode. The tracing result is shown in Figure 2-34.


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Figure 2-34 Result of tracing user messages

l

If the Tracing Mode is set to Save on Server, and click OK, the messages on the user interface are traced in the Save on Server mode. The LMT no longer displays the tracing messages.

----End

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3 BSS System Information

3

BSS System Information

About This Chapter System information (SI) refers to the major radio network parameters on the Um interface such as the network identification parameters, cell selection parameters, system control parameters, and network functional parameters. 3.1 BSS System Information Type The BSS system information consists of System Information Type 1 , System Information Type 2, System Information Type 2bis, System Information Type 2ter, System Information Type 2quater, System Information Type 3, System Information Type 4, System Information Type 5, System Information Type 5bis, System Information Type 5ter, System Information Type 6, System Information Type 7, System Information Type 8, and System Information Type 13. 3.2 Internal BSC Signaling Procedure of the System Information This describes the internal BSC signaling procedure of the system information.

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3-1



3.1 BSS System Information Type The BSS system information consists of System Information Type 1 , System Information Type 2, System Information Type 2bis, System Information Type 2ter, System Information Type 2quater, System Information Type 3, System Information Type 4, System Information Type 5, System Information Type 5bis, System Information Type 5ter, System Information Type 6, System Information Type 7, System Information Type 8, and System Information Type 13. 3.1.1 System Information Type 1 System Information Type 1 is sent on the BCCH by the network to all the MSs within the cell. It provides information about the Random Access Channel (RACH) control and the cell allocation (CA). 3.1.2 System Information Types 2, 2bis, 2ter, and 2quater This topic describes the functions and contents of System Information Types 2, 2bis, 2ter, and 2quater. 3.1.3 System Information Type 3 System Information Type 3 describes the location area identification, cell identity, RACH control, and parameters of cell selection. It is mandatory and is sent on the BCCH. 3.1.4 System Information Type 4 System Information Type 4 is sent on the BCCH by the network. It provides information about the location area identification, RACH control, cell selection parameters, and available CBCH information. 3.1.5 System Information Types 5, 5bis, and 5ter This topic describes the functions and contents of System Information Types 5, 5bis, and 5ter. 3.1.6 System Information Type 6 System Information Type 6 provides information about the location area identification, cell identity, and other parameters of cell functions. 3.1.7 System Information Type 7 System Information Type 7 is sent on the BCCH. It provides information about cell reselection parameters. 3.1.8 System Information Type 8 System Information Type 8 is mandatory and is sent on the BCCH. It provides information about cell reselection parameters. 3.1.9 System Information Type 13 System Information Type 13 is sent on the BCCH by the network. It provides information related to GPRS in the cell.

3.1.1 System Information Type 1 System Information Type 1 is sent on the BCCH by the network to all the MSs within the cell. It provides information about the Random Access Channel (RACH) control and the cell allocation (CA).

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Functions System Information Type 1 is sent on the BCCH by the network to all the MSs within the cell. It provides information about the Random Access Channel (RACH) control and the cell allocation (CA).

Contents SYS INFO 1 l

Cell Channel Desc.

l

RACH Control Para.

l

SI 1 Rest Octets.

l

CA table One cell can be configured with a maximum of 64 frequencies. The actual configuration of cell frequencies is subject to the Table 3-1. The BSC selects a format of cell channel description based on the configuration of cell frequencies. The format of cell channel description is defined by octet 2, Format ID (Bit 128, Bit 127, Bit 124, Bit 123, and Bit 122) in the Table 3-2. Table 3-1 Cell channel description 8

7

6

5

4

3

2

1

Cell Channel Description IEI

octet 1

Bit

Bit

0

0

Bit

Bit

Bit

Bit

128

127

Spar e

Spare

124

123

122

121

Bit

Bit

Bit

Bit

Bit

Bit

Bit

Bit

120

119

118

117

116

115

114

113

…

…

…

…

…

…

…

…

Bit

Bit

Bit

Bit

Bit

Bit

Bit

Bit

8

7

6

5

4

3

2

1

octet 2

octet 3 … octet 17

Table 3-2 Format of cell channel description Bit 128

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Bit 127

Bit 124

Bit 123

Bit 122

Format Notation

0

0

X

X

X

bit map 0

1

0

0

X

X

1024 range

1

0

1

0

0

512 range

1

0

1

0

1

256 range


3-3



Bit 128

Bit 127

Bit 124

Bit 123

Bit 122

Format Notation

1

0

1

1

0

128 range

1

0

1

1

1

variable bit map

Different formats of cell channel description correspond to different numbers of available cell frequencies. Assume that the number of available frequencies for a cell is n (except for duplicate and invalid frequencies). ARFCN(i) (i=1,…,n) represents the Absolute Radio Frequency Channel Number. The numbers of available frequencies for different formats of cell channel description are as follows: –

Bit map 0 The bit map 0 format is used for GSM 900 frequencies. The number of available frequencies is 64 if 1 ≤ARFCN(i) ≤ 124.

–

1024 range If the 1024 range format is used, the number of available frequencies for a cell is equal to or smaller than 16. For a GSM 900 cell, 1 ≤ ARFCN (i) ≤ 124. For a GSM 1800 cell, 512 ≤ ARFCN (i) ≤ 885.

–

512 range If the 512 range format is used, the number of available frequencies for a cell is equal to or smaller than 18. The interval between any two frequencies must be less than 512.

–

256 range If the 256 range format is used, the number of available frequencies for a cell is equal to or smaller than 22. The interval between any two frequencies must be less than 256. For example, in 128 range format, frequency 512 and frequency 812 cannot be configured together.

–

128 range If the 128 range format is used, the number of available frequencies for a cell is equal to or smaller than 29. The interval between any two frequencies must be less than 128. For example, in 128 range format, frequency 512 and frequency 712 cannot be configured together.

–

Variable bit map If the variable bit map format is used, the number of available frequencies for a cell is equal to or smaller than 64. The interval between any two frequencies must be 1–111. For example, in variable bit map format, you can configure 64 frequencies numbered from 512 to 575 with an increment of 1. However, you cannot configure 64 frequencies numbered from 512 to 638 with an increment of 2. NOTE

The early-mentioned restrictions are mainly for the GSM1800 frequencies. l

RACH Control Para. The RACH control parameters include the following: –

MAX retrans Maximum number of retransmissions (Max Retrans) defines the maximum number of channel request messages that can be resent before a MS receives an immediate

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assignment message. Therefore, the number of channel request messages that an MS can send is M (Max Retrans) plus 1. The parameter has two bits, ranging from 0 to 3. The corresponding maximum numbers of retransmissions are 1, 2, 4, and 7. –

Tx_integer Number of slots to spread transmission (Tx-integer) defines the number of timeslots between two consecutive transmissions of channel request messages.

–

CELL_BAR_ACCESS Cell Bar Access (CBA) determines whether an MS can gain access to a cell. It has only one bit. Value 0 of this bit means that the MS can access the cell, and value 1 of this bit means the MS cannot access the cell. This parameter does not affect the handover access of the MS.

–

AC CN Access Control Class N (AC CN) defines the access class for an MS. Each class is represented by a bit. N = 0, 1, … 9, 11, …, 15, totally 16 bits. If the AC CN bit is 1, the access of an MS with AC C = N is barred. Otherwise, the access of the MS with AC C = N is permitted. The MSs of classes 11–15 have a higher access priority than the MSs of classes 0–9. The MSs of classes 11-15 have the same priority. So do the MSs of classes 0–9.

–

RE Call reestablishment allowed (RE) determines whether call reestablishment is allowed when call drops occur. The parameter has one bit. Value 0 means that call reestablishment is allowed in the cell. Value 1 means that call reestablishment is not allowed in the cell.

–

EC Emergency call allowed (EC) determines whether emergency calls are allowed when there is no SIM or the access is barred. The parameter has one bit. Value 0 means that emergency calls are allowed in the cell to all MSs. Value 1 means that emergency calls are not allowed in the cell except for the MSs that belong to classes 11–15. NOTE

A random value, which belongs to {S, S+1,....S+T-1}, is used as the time interval between two consecutive transmissions of channel request messages sent by an MS. The units of timeslot intervals are TDMA frames. "S" is subject to the configuration of common channels. "T" is Txinteger.

Table 3-3 lists the relation between "S" and "T". Table 3-3 Relation between "S" and "T" Tx-Integer

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Non Combined CCCH

Combined CCCH

3, 8, 14, 50

55

41

4, 9, 16

76

52

5, 10, 20

109

58

6, 11, 25

163

86

7, 12, 32

217

115


3-5


3 BSS System Information NOTE

When satellite transmission is used, Huawei recommends that Max retrans is set to 4 and Txinteger is set to 32 to reduce the delay caused by satellite transmission. l

SI 1 Rest Octets The SI 1 Rest Octets information element has eight bits. It contains indication information about the PCS 1900 and the DCS 1800 and spare bits.

3.1.2 System Information Types 2, 2bis, 2ter, and 2quater This topic describes the functions and contents of System Information Types 2, 2bis, 2ter, and 2quater.

Functions System Information Type 2 is sent on the BCCH by the network to all MSs within the cell. It provides information about the RACH control, NCC Permitted, and the BCCH allocation (BA1) in the neighbor cells. Generally, System Information Types 2, 2bis, and 2ter describe different parts of the BA1 list. The MS reads and decodes the BA1 list and then performs cell reselection in idle mode. A GSM 900 MS in PHASE 1 recognizes only the neighbor cell frequencies described in System Information Type 2 and ignores the neighbor cell frequencies described in System Information Types 2bis and 2ter. System Information Type 2bis is sent optionally on the BCCH by the network to all MSs within the cell. It provides information about the RACH control and the extension of the BCCH allocation in the neighbor cells (part of BA1). System Information Type 2 does not describe all the frequencies in the BA1 list. Therefore, System Information Type 2bis describes the rest of the frequencies that are on the same frequency band. System Information Type 2ter is sent optionally on the BCCH by the network to all MSs within the cell. It provides information about the extension of the BCCH allocation in the neighbor cells (part of BA1). It is read only by the dual-band MSs. The GSM 900 MSs and the GSM 1800 MSs ignore this message because of band difference. System Information Type 2quater provides information about the BCCH allocation in the 3G neighbor cells under the condition that the inter-system handover is supported and the 3G neighbor cells are configured. It is used for the reselection of 3G cells.

Contents l

l

l

SYS INFO 2 –

Neighbor Cell Desc.

–

NCC permitted

–

RACH Control Para.

SYS INFO 2 BIS –

Neighbor Cell Desc.

–

RACH Control Para.

SYS INFO 2TER –

l

SYS INFO 2QUATER –

3-6

Neighbor Cell Desc. (Extended) SI 2quater Rest Octets. Huawei Technologies Proprietary

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HUAWEI BSC6000 Base Station Subsystem BSS Signaling Analysis Guide l


Neighbor Cell Description (BA1) The Neighbor Cell Description information element provides the absolute channel numbers of the BCCH carriers in the neighbor cells of the current cell. Currently, Huawei supports a maximum of 32 neighbor cells per cell. Except for bit 5 (BA-IND) and bit 6 (EXT-IND) of octet 2, the Neighbor Cell Description information element is coded as the Cell Channel Description information element. For details, refer to the cell channel description in 3.1.1 System Information Type 1 . The extension indication (EXT-IND) is sent in System Information Types 2 and 5. It indicates whether there are extended neighbor cell frequencies sent in System Information Types 2bis and 5bis. If the EXT-IND bit is set to 0, System Information Types 2 and 5 carry the complete BA. If the EXT-IND bit is set to 1, System Information Types 2 and 5 carry only a part of the BA. The BA indication (BA-IND) is sent in System Information Types 2 and 5. It has one bit and is used by the MS to discriminate the changes in the BA1 or the BA2. If the adjacent cell relation and the BA2 are modified during the conversation, the BA-IND bit in System Information Type 5 should be 1, indicating that the MS should decode the neighbor cell frequencies again. The default of the BA-IND bit is 0.

l

The NCC Permitted information element is sent in System Information Types 2 and 6. It has eight bits and provides all the NCCs required by MSs. If bit N is 0 (0 ≤ N ≤ 7), the MS does not measure the power level of the cell where the NCC is N, which means that the MS is not handed over to the network where the NCC is N. The NCC Permitted information element is mainly used for handovers and cell reselection.

l

For details about the RACH Control Para. information element, refer to 3.1.1 System Information Type 1 .

l

The Neighbor Cell Description 2 information element is sent in System Information Types 2ter and 5ter. Except for bit 5 (BA-IND) and bits 6 and 7 (Multiband_Reporting) of octet 2, the Neighbor Cell Description 2 information element is coded as the Cell Channel Description information element. For details, refer to 3.1.1 System Information Type 1 . The Multiband Reporting information element is sent in System Information Types 2ter and 5ter. It has two bits and is used to request the dual-band MS to report information about neighbor cells of multiple bands. For details, refer to Table 3-4. Table 3-4 Multiband reporting Multiband Reporting (2 bits)

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Meaning

0

The MS reports six cells where the signal strength is the strongest, irrespective of the band used.

1

The MS reports a neighbor cell that is on a different band. It reports in the other five positions the neighbor cells that are on the same band.

10

The MS reports two neighbor cells that are on a different band. It reports in the other four positions the neighbor cells that are on the same band.

11

The MS reports three neighbor cells that are on a different band. It reports in the other three positions the neighbor cells that are on the same band.


3-7


3 BSS System Information l

SI 2quater Rest Octets The SI 2quater Rest Octets information element has the following parameters: –

BA_IND, 3G_BA_IND, and MP_CHANGE_MARK

–

3G Neighbor Cell Description and Index_Start_3G

–

UTRAN FDD Description and UTRAN TDD Description

–

3G MEASUREMENT PARAMETERS Description

3.1.3 System Information Type 3 System Information Type 3 describes the location area identification, cell identity, RACH control, and parameters of cell selection. It is mandatory and is sent on the BCCH.

Functions System Information Type 3 describes the location area identification, cell identity, RACH control, and parameters of cell selection. It is mandatory and is sent on the BCCH.


Cell Identity

l

LAI

l

Cell Option (BCCH)

l

Cell Selection Para.

l

RACH Control Para.

l

SI 3 Rest Octets.

l

CGI Cell Global Identification (CGI) consists of the Location Area Identification (LAI) and the Cell Identity (CI). The LAI consists of the Mobile Country Code (MCC), the Mobile Network Code (MNC), and the Location Area Code (LAC). System Information Types 3, 6, and 4 contain all or part of the CGI information. Upon receiving the system information, the MS decodes the CGI. Based on the MCC and the MNC, the MS determines whether to access the network in the cell and whether the current location area has changed or not. If the location area has changed, the MS initiates a location update procedure. The MCC is unique worldwide. It consists of three decimal numerals. For example, the MCC of China is 460. The MNC is unique nationwide. For example, the MNC of China Mobile is 00, and the MNC of China Unicom is 01. The LAC and the CI are planned by each GSM network operator. Both the LAC and the CI have two octets. The CI ranges from 0X0001 to 0XFFFE. 0X0000 and 0XFFFF are reserved.

l

Control Channel Desc. The Control Channel Description information element has the following parameters: –

MSCR The MSC Release (MSCR) parameter indicates the release of an MSC. The parameter has one bit. If the bit is 0, the MSC is released in 1998 or earlier. If it is 1, the MSC is released in 1999 or later.

–

3-8

ATT Huawei Technologies Proprietary

Issue 01 (2007-11-26)



The Attach-Detach Allowed (ATT) parameter indicates whether the MS is allowed to initiate an IMSI attach and detach procedure. The ATT has one bit. If it is 0, the MS is not allowed. If it is 1, the MS is allowed. –

CCCH-CONF The CCCH-CONF parameter determines the combination mode of the CCCH. The CCCH-CONF has three bits. Table 3-5 describes the meaning of the CCCH-CONF. Table 3-5 Meaning of the CCCH-CONF CCCH-CONF (Three Bits)

Number of CCCH Message Blocks in One BCCH Multiframe

0

One basic physical channel used for CCCH, not shared with SDCCHs

9

1

One basic physical channel used for CCCH, shared with SDCCHs

3

10

Two basic physical channels used for CCCH, not shared with SDCCHs

18

100

Three basic physical channels used for CCCH, not shared with SDCCHs

27

110

Four basic physical channels used for CCCH, not shared with SDCCHs

36

Others

–

Meaning

Reserved

-

BS_AG_BLKS_RES The BS_AG_BLKS_RES parameter indicates the proportion of AGCH message blocks in the CCCH message blocks. If the CCCH-CONF is 001, the BS_AG_BLKS_RES ranges from 0 to 2. If the CCCH-CONF is not 001, the BS_AG_BLKS_RES ranges from 0 to 7. After the CCCH-CONF is set, the BS_AG_BLKS_RES is actually used to determine the proportions of AGCHs and PCHs on the CCCH. You can modify the BS_AG_BLKS_RES to balance the loading of AGCHs and PCHs.

–

BS-PA-MFRAMS The BS-PA-MFRAMS parameter indicates the number of multiframes contained in a period for the transmission of Paging Request messages to the same paging subgroup. It actually determines the number of paging subchannels contained in the paging channel of a cell. It has three bits. The value range is 0-7, representing 2-9 multiframes periods for transmission of Paging Request messages to the same paging subgroup respectively.

–

T3212 The timeout value of timer T3212 indicates the frequency of periodic location update. It has eight bits. The value range is 0-255. Each unit indicates six minutes. Value 0 indicates that periodic location update is not performed.

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3-9



Cell Selection Para. The Cell Selection Para. affect the activities of an MS after it is switched on. These parameters include the following: –

Cell Reselection Hysteresis An MS can perform cell reselection only if the difference between the signal level of the neighbor cell (in a different location area) and the C2 of the local cell is greater than the value of Cell Reselection Hysteresis. This parameter has three bits, ranging from 0 to 7. The range of the signal level is 0-14 dB.

–

MS_TXPWR_MAX_CCH The MS_TXPWR_MAX_CCH parameter indicates the transmit power the MS may use before it receives the power control command. The parameter has five bits, ranging from 0 to 31. Each value corresponds to the output power of an MS.

–

RXLEV_ACCESS_MIN The RXLEV_ACCESS_MIN indicates the minimum received signal level required for the MS to access the system. It has six bits, ranging from 0 to 63. The range of the signal level is from -110 dBm to -47 dBm.

–

ACS The ACS parameter indicates whether the MS uses C2 during cell reselection. It has only one bit. In System Information Type 3, this parameter is meaningless. In System Information Type 4, value 0 of the bit indicates that the SI4 REST of System Information Type 4 is used to calculate the parameters related to C2. Other values indicate that the REST of System Information Types 7 and 8 are used to calculate the parameters related to C2.

–

NECI The NECI parameter indicates whether the current cell supports half rate services or not. It has only one bit. Value 0 of the bit indicates that the current cell does not support half rate services. Value 1 of the bit indicates that the current cell supports half rate services.

l

RACH Control Para. For details, refer to 3.1.1 System Information Type 1 .

l

SI 3 Rest Octets The SI3 Rest Octets information element has the following parameters: –

PI This parameter indicates whether the MS uses C2 as the cell reselection parameter and whether the parameter used to calculate C2 exists or not. It has only one bit. Value 0 of the bit indicates that the MS uses C1 as the cell reselection parameter. Value 1 of the bit indicates that the MS uses C2 that is derived from the system information as the cell reselection parameter.

–

CBQ The Cell Bar Qualify (CBQ) parameter has only one bit. Along with CELL_BAR_ACCESS, it indicates the priority of a cell. For details, refer to Table 3-6.

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Table 3-6 Parameters affecting cell priority in cell selection CBQ

–

CBA

Priority of Cell Selection

Status of Cell Reselection

0

0

Normal

Normal

0

1

Barred

Barred

1

0

Low

Normal

1

1

Low

Normal

CRO The Cell Reselect Offset (CRO) parameter applies an offset to C2. It has six bits. The range of the signal level is 0–126 dB. Along with TO and PT, the CRO is used to regulate C2 manually.

–

TO The value range of the TEMPORARY_OFFSET (TO) parameter is 0–7. Each level represents 10 dB. For example, 0 refers to 0 dB, 1 refers to 10 dB, 6 refers to 60 dB, and 7 refers to infinity.

–

PT The value range of the Penalty Time (PT) parameter is 0–31. Each level represents 20 seconds. For example, 0 refers to 20 s and 30 refers to 620 s. 31 is reserved to indicate that CRO is subtracted from C2 and that TO is ignored.

–

2TI This 2TI parameter indicates whether System Information Type 2quater can be obtained or not.

–

ECSC The Early Classmark Sending Control (ECS) parameter indicates whether the ECS is allowed or not.

–

GPRS This GPRS parameter indicates whether the GPRS is supported or not.

–

SI2quaterI The SI2quaterI parameter indicates whether System Information Type 2quater can be obtained or not.

3.1.4 System Information Type 4 System Information Type 4 is sent on the BCCH by the network. It provides information about the location area identification, RACH control, cell selection parameters, and available CBCH information.

Functions System Information Type 4 is sent on the BCCH by the network. It provides information about the location area identification, RACH control, cell selection parameters, and available CBCH information. The optional IEs CBCH Channel Description and CBCH Mobile Allocation are used when the system supports cell broadcast. These IEs describe the configurations of the CBCH and the related frequency information. Issue 01 (2007-11-26)


3-11




LAI

l

Cell Selection Para.

l

RACH Control Para.

l

CBCH Channel Desc. (optional)

l

CBCH Mobile Allocation (optional)

l

SI4 Rest Oct.

l

LAI For details, refer to 3.1.3 System Information Type 3 .

l

Cell Selection Para. For details, refer to 3.1.3 System Information Type 3 .

l

RACH Control Para. For details, refer to 3.1.2 System Information Types 2, 2bis, 2ter, and 2quater.

l

CBCH Channel Description and CBCH Mobile Allocation Both CBCH Channel Description and CBCH Mobile Allocation are optional. If the system supports cell broadcast, CBCH Channel Description indicates the configuration of the CBCH. If the CBCH is in frequency hopping mode, CBCH Mobile Allocation is mandatory.

l

SI4 Rest Oct. If the cell selection parameter ACS is set to No, the SI4 Rest Oct. is used to calculate the cell reselection parameter C2. The criteria for cell reselection are as follows: –

When PENALTY_TIME = 31, C2 = C1 - CELL_RESELECT_OFFSET

–

When PENALTY_TIME is not equal to 31, C2 = C1 + CELL_RESELECT_OFFSET - TEMPORARY_OFFSET x H(PENALTY_TIME-T) For a non-serving cell, if x < 0, H (x) = 0; if x 0, H (x) = 1. For a serving cell, H (x) = 0.

The SI4 Rest Oct. information element has the following parameters: –

PI For details, refer to 3.1.3 System Information Type 3 .

–

CBQ For details, refer to 3.1.3 System Information Type 3 .

–

CRO For details, refer to 3.1.3 System Information Type 3 .

–

TO For details, refer to 3.1.3 System Information Type 3 .

–

PT For details, refer to 3.1.3 System Information Type 3 .

3.1.5 System Information Types 5, 5bis, and 5ter This topic describes the functions and contents of System Information Types 5, 5bis, and 5ter. 3-12


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Functions System Information Type 5 provides the frequency information of the neighbor cells (BA2). It is mandatory and is sent on the SACCH. Different from System Information Type 2, the MS can read the frequency information described in System Information Type 5 when it is in the conversation state and report the information about the neighbor cells in the measurement report. Such information is used for handovers. A GSM 900 MS in PHASE 1 recognizes the neighbor cell frequencies described only in System Information Type 5 and ignores the neighbor cell frequencies described in System Information Types 5bis and 5ter. System Information Type 5bis provides the frequency information of the neighbor cells (part of BA2). It is optional and is sent on the SACCH. System Information Type 5 does not describe all the frequencies in the BA1 list. Therefore, System Information Type 5bis describes the rest of the frequencies that are on the same frequency band. System Information Type 5ter provides the frequency information of the neighbor cells (part of BA2). It is sent on the SACCH. Only the dual-band MSs read this message. The GSM 900 MSs and the GSM 1800 MSs ignore this message.

Contents SYS INFO 5- - Neighbor Cell Desc. l

SYS INFO 5- - Neighbor Cell Desc.

l

SYS INFO 5TER - - Neighbor Cell Desc. (Extended)

l

Neighbor Cell Desc. For details, refer to 3.1.2 System Information Types 2, 2bis, 2ter, and 2quater.

l

Neighbor Cell Description (Extended) For details, refer to 3.1.2 System Information Types 2, 2bis, 2ter, and 2quater.

3.1.6 System Information Type 6 System Information Type 6 provides information about the location area identification, cell identity, and other parameters of cell functions.

Functions System Information Type 6 provides information about the location area identification, cell identity, and other parameters of cell functions. It is mandatory and is sent on the SACCH.


Cell Identity

l

LAI

l

Cell Option (BCCH)

l

NCC Permitted

l

CGI For details, refer to 3.1.3 System Information Type 3 .

l

Cell Option For details, refer to 3.1.3 System Information Type 3 .

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NCC Permitted For details, refer to 3.1.2 System Information Types 2, 2bis, 2ter, and 2quater.

3.1.7 System Information Type 7 System Information Type 7 is sent on the BCCH. It provides information about cell reselection parameters.

Functions System Information Type 7 is sent on the BCCH. It provides information about cell reselection parameters.

Contents SI 7 Rest Octets The SI 7 Rest Octets information element contains the cell reselection parameters used by the MS. It may also contain the Power Offset parameter used by the DCS1800 Class 3 MS. The coding scheme of SI 7 Rest Octets is the same as that of SI 4 Rest Octets. For details, refer to 3.1.4 System Information Type 4 .

3.1.8 System Information Type 8 System Information Type 8 is mandatory and is sent on the BCCH. It provides information about cell reselection parameters.

Functions System Information Type 8 is mandatory and is sent on the BCCH. It provides information about cell reselection parameters.

Contents SI 8 Rest Octets The SI 8 Rest Octets information element contains the cell reselection parameters used by the MS. It may also contain the Power Offset parameter used by the DCS1800 Class 3 MS. The coding scheme of SI 8 Rest Octets is the same as that of SI 4 Rest Octets. For details, refer to 3.1.4 System Information Type 4 .

3.1.9 System Information Type 13 System Information Type 13 is sent on the BCCH by the network. It provides information related to GPRS in the cell.

Functions System Information Type 13 is sent on the BCCH by the network. It provides information related to GPRS in the cell.

Contents SI 13 Rest Octets 3-14


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The SI 13 Rest Octets information element has the following parameters: l

BCCH_CHANGE_MARK The BCCH_CHANGE_MARK parameter has three bits. It changes according to the messages sent on the BCCH.

l

SI_CHANGE_FIELD The SI parameter is binary and indicates that the last bit of the BCCH_CHANGE_MARK parameter has changed. It has four bits and ranges from 0 to 15.

l

SI13_CHANGE_MARK The SI13_CHANGE_MARK parameter ranges from 0 to 3.

l

RAC The RAC parameter is binary and indicates the routing area code. It has eight bits.

l

SPGC_CCCH_SUP The SPGC_CCCH_SUP parameter indicates whether the CCCH supports the SPLIT_PG_CYCLE parameter or not. Value 0 indicates that the CCCH does not support SPLIT_PG_CYCLE. Value 1 indicates that the CCCH supports SPLIT_PG_CYCLE.

l

PRIORITY_ACCESS_THR The PRIORITY_ACCESS_THR parameter indicates whether packet access is supported or not. It has three bits. Value 000 indicates that packet access is not supported. Values 001 and 010 are reserved, indicating by default that packet access are not supported. Values 011, 100, 101, and 110 indicate that users of priorities 1, 1 and 2, 1 to 3, and 1 to 4, respectively, support packet access. Value 111 is reserved, indicating that packet access is supported.

l

NETWORK_CONTROL_ORDER The NETWORK_CONTROL_ORDER parameter has two bits. Value 00 indicates that the cell controls cell reselection and no measurement reports are sent. Value 01 indicates that the cell controls cell reselection and the MS sends the measurement reports. Value 10 indicates that the network controls cell reselection and the MS sends the measurement reports. Value 11 is reserved.

l

PSI1_REPEAT_PERIOD The PSI1_REPEAT_PERIOD parameter indicates the retransmit period of the PSI2. It has four bits. Value 0000 indicates that the retransmit period is one multiframe. Value 0001 indicates that the retransmit period is two multiframes. Value 0010 indicates that the retransmit period is three multiframes. By analogy, value 1110 indicates that the retransmit period is 15 multiframes and value 1111 indicates that the retransmit period is 16 multiframes.

l

System Information Type 13 also include parameters such as the GPRS Mobile Allocation, GPRS Cell Options, GPRS Power Control, Parameters struct, and PBCCH Description struct.

3.2 Internal BSC Signaling Procedure of the System Information This describes the internal BSC signaling procedure of the system information.

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System Information Type 1 You can obtain the Cell Frequency in System Information Type 1 in the Cell Attributes window. Table 3-7 lists the RACH control parameters in System Information Type 1 and the corresponding parameters on the BSC6000 Local Maintenance Terminal. Table 3-7 RACH control parameters in System Information Type 1 and the corresponding parameters on the BSC6000 Local Maintenance Terminal RACH Control Parameters in System Information Type 1

Parameters on the BSC6000 Local Maintenance Terminal

Max Retrans

MS MAX Retrans

Tx_interger

Tx_interger

Cell Bar Access

Cell_Bar_ Access

AC

Common Access Control Class and Special Access Control Class

RE

Call Reestablishment Forbidden

EC

Emergent Call Disable

To configure the parameters listed in the table on the BSC6000 Local Maintenance Terminal, do as follows:

3-16

l

In the dialog box shown in Figure 3-1, click Call Control. Then set MS MAX retrans, Common Access Control Class, Special Access Control Class, and Emergent Call Disable.

l

In the dialog box shown in Figure 3-1, click Idle Mode. Set Tx-integer (RACH Timeslot that equals to a TDMA frame, 4.615ms) and Cell_Bar_Access.

l

In the dialog box shown in Figure 3-1, set Call Reestablishment Forbidden.


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Figure 3-1 Set Cell Attributes dialog box

NOTE

If cell flow control is enabled, the MAX Retrans and Tx_interger parameters in System Information Type 1 are automatically regulated according to the current flow control system.

System Information Types 2, 2bis, and 2ter l

The information on neighbor cell frequencies in System Information Types 2, 2bis, and 2ter is obtained from the 2G BA1 Table. The Ncc Permitted parameter in System Information Type 2 is obtained from the Ncc Permitted field in the Idle Mode. The RACH Control Parameters in System Information Types 2 and 2bis are the same as that in System Information Type 1. For details, see Table 3-7.

l

The information in System Information Type 2quater is obtained from the UTRAN System Message, UTRAN FDD Cell BA1, and UTRAN TDD Cell BA1.

l

To configure the parameters listed in the table on the BSC6000 Local Maintenance Terminal, do as follows:

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–

In the dialog box shown in Figure 3-1, click Idle Mode, select Advanced, and then set the neighbor cell frequency in 2G BA1 Table.

–

In the dialog box shown in Figure 3-1, click Idle Mode. Then set NCC Permitted.


3-17


3 BSS System Information –

In the dialog box shown in Figure 3-1, click Call Control, and then click Advanced. Then set the UTRAN system message in UTRAN System Message.

–

In the dialog box shown in Figure 3-1, click Idle Mode, and then click Advanced. Then set the UTRAN neighbor cell frequency in UTRAN FDD Cell BA1.

–

In the dialog box shown in Figure 3-1, click Idle Mode, and then click Advanced. Then set the UTRAN neighbor cell frequency in UTRAN TDD Cell BA1.

System Information Type 3 The CGI in System Information Type 3 is obtained from the Cell Attributes window. Table 3-8 lists the control channel parameters in System Information Type 3 and the corresponding parameters on the BSC6000 Local Maintenance Terminal. Table 3-8 Control channel parameters in System Information Type 3 and the corresponding parameters on the BSC6000 Local Maintenance Terminal Control Channel Parameters in System Information Type 3


ATT

ATT

CCCH-CONF

CCCH Conf

BS_AG_BLKS_RES

BS_AG_BLKS_RES

BS-PA-MFRAMS

BS-PA-MFRARMS

T3212

Period of Periodic Location Update (6 minutes)

To configure the parameters listed in the table on the BSC6000 Local Maintenance Terminal, do as follows: In the dialog box shown in Figure 3-1, click Idle Mode. Set ATT, CCCH-CONF, BS_AG_BLKS_RES, BS-PA-MFRAMS, and T3212. Table 3-9 lists the cell option parameters in System Information Type 3 and the corresponding parameters on the BSC6000 Local Maintenance Terminal. Table 3-9 Cell option parameters in System Information Type 3 and the corresponding parameters on the BSC6000 Local Maintenance Terminal Cell option parameters in System Information Type 3


PWRC

PWRC

DTX

UL DTX

Radio Link Timeout

Radio Link Timeout

To configure the parameters listed in the table on the BSC6000 Local Maintenance Terminal, do as follows: 3-18


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l

In the dialog box shown in Figure 3-1, click Other Attributes, and then click Advanced. On the Public Channel Control tab page, set PWRC.

l

In the dialog box shown in Figure 3-1, set UL DTX.

l

In the dialog box shown in Figure 3-1, click Call Control. Set Radio Link Timeout (SACCH period (480ms)).

Table 3-10 lists the cell option parameters in System Information Type 3 and the corresponding parameters on the BSC6000 Local Maintenance Terminal. Table 3-10 Cell selection parameters in System Information Type 3 and the corresponding parameters on the BSC6000 Local Maintenance Terminal Cell Selection Parameters in System Parameters on the BSC6000 Local Information Type 3 Maintenance Terminal Cell Reselection Hysteresis

CRH

MS_TXPWR_MAX_CCH

MS_TXPWR_MAX_CCH

RXLEV_ACCESS_MIN

RXLEV_ACCESS_MIN

ACS

PI

NECI

Support Half Rate

To configure the parameters listed in the table on the BSC6000 Local Maintenance Terminal, do as follows: l

In the dialog box shown in Figure 3-1, click Idle Mode. Set CRH and ACS.

l

In the dialog box shown in Figure 3-1, click Other Attributes, select Advanced and Common Channel Control, and then set MS_TXPWR_MAX_CCH and Half rate supported.

l

In the dialog box shown in Figure 3-1, set RXLEV_ACCESS_MIN.

The RACH Control Parameters information element in System Information Type 3 is the same as that in System Information Type 1. For details, refer to Table 3-7.

System Information Type 4 The Location Area Identification in System Information Type 4 is obtained from the Cell Attributes window. For the Cell Selection Parameters, see Table 3-10. The RACH Control Parameters information element in System Information Type 4 is the same as that in System Information Type 1. For details, see Table 3-7. Table 3-11 lists the Rest Oct parameters in System Information Type 4 and the corresponding parameters on the BSC6000 Local Maintenance Terminal.

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Table 3-11 Rest Oct parameters in System Information Type 4 and the corresponding parameters on the BSC6000 Local Maintenance Terminal Rest Oct Parameters in System Information Type 4


PI

PI

CBQ Cell Bar Quality

Cell_Bar_Qualify

CRO

CRO (2dB)

TO TO, TEMPORARY_OFFSET PT

TO PT (s)

To configure the parameters listed in the table on the BSC6000 Local Maintenance Terminal, do as follows: l

In the dialog box shown in Figure 3-1, click Idle Mode. Set PI, CBQ, and CRO (2 dB).

l

In the dialog box shown in Figure 3-1, click Idle Mode, and then click Advanced. On the Idle Parameter tab page, set TO and PT.

Other System Information l

The information on neighbor cell frequencies in System Information Types 5, 5bis, and 5ter is obtained from the 2G BA2 Table, UTRAN FDD Cell BA1, and UTRAN TDD Cell BA1. To configure the parameters listed in the table on the BSC6000 Local Maintenance Terminal, do as follows:

3-20

–

Click HO Data, and then select Advanced and 2G BA2 Table. Then set the corresponding parameters.

–

In the dialog box shown in Figure 3-1, click HO Data, and then select Advanced and UTRAN FDD Cell BA1. Then set the corresponding parameters.

–

In the dialog box shown in Figure 3-1, click HO Data, and then select Advanced and UTRAN TDD Cell BA1. Then set the corresponding parameters.

l

The CGI in System Information Type 6 is obtained from the Cell Attributes window. The Cell Options information element in System Information Type 6 is the same as that in System Information Type 3. For details, see Table 3-9. The procedure for configuring NCC Permitted is the same as that for configuring NCC Permitted in System Information Type 2.  

l

The Rest Oct in System Information Type 7 is the same as that in System Information Type 4. See Table 3-11.

l

The Rest Oct in System Information Type 8 is the same as that in System Information Type 4. See Table 3-11.

l

System Information Type 13 is not processed in the BSC and is directly forwarded to the BTS.


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4 Immediate Assignment

4

Immediate Assignment

About This Chapter This topic describes immediate assignment including its internal BSC signaling procedure and abnormal cases. 4.1 Immediate Assignment Procedure The purpose of immediate assignment is to establish a Radio Resource (RR) connection between an MS and the network on the Um interface. The immediate assignment procedure is initiated by the MS. 4.2 Internal BSC Signaling Procedure of Immediate Assignment This topic describes the internal BSC signaling procedure of immediate assignment. 4.3 Abnormal Immediate Assignment Cases This topic describes the abnormal immediate assignment cases.

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4-1



4.1 Immediate Assignment Procedure The purpose of immediate assignment is to establish a Radio Resource (RR) connection between an MS and the network on the Um interface. The immediate assignment procedure is initiated by the MS. Figure 4-1 shows the immediate assignment procedure. Figure 4-1 Immediate assignment procedure MS

BTS

BSC

Channel Request(1) RACH Channel Required(2) Channel Activation(3) Channel Activation Acknowledge(4) Immediate Assignment Command(5) AGCH Start T3101

SABM(6) main DCCH UA(7) main DCCH Establish Indication(8)

Stop T3101

1.

The MS sends the BTS a Channel Request message on the RACH. The Channel Request message contains the Establish Cause and Random Reference parameters. It has eight bits. Bits 3 to 6 indicate the access cause, and bit 5 to 2 carry the identifier. Based on a Channel Request message, a maximum of 32 MSs are discriminated. The UA response messages on the Um interface are used to discriminate more MSs.

2.

The BTS sends the BSC a Channel Required message. The Channel Required message contains the Request Reference and Access Delay parameters. The Request Reference parameter contains the random access reference value and the absolute frame number of the received access burst. The Access Delay is the delay of the access burst.

3.

4-2

Upon receiving the Channel Required message, the BSC assigns a signaling channel and sends the BTS a Channel Activation message to activate a radio channel. The Channel Activation message carries the activation type, channel mode, level, and TA. Huawei Technologies Proprietary

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4.

Upon receiving the Channel Activation message, if the channel type is correct, BTS2 turns on the power amplifier on the specified channel to receive information in the uplink direction and sends a Channel Activation Acknowledge message to the BSC.

5.

The BSC sends through the BTS to the MS an Immediate Assignment Command message. The Immediate Assignment Command message is sent on the AGCH. It carries the Immediate Assignment Extend message and the assignment information of two MSs. The Immediate Assignment Command message has the following information elements: l

Dedicated mode or TBF The Dedicated mode or TBF information element requests the MS to decode the rest of the message to an Immediate Assignment message or to allocate a Temporary Block Flow.

l

Page Mode The Paging Mode information element controls the action of the MSs in a paging group.

l

Channel Description The Channel Description information element describes an assigned channel and the corresponding SACCH. It carries the Channel Type, TDMA offset, timeslot, and absolute RF channel number.

l

Request Reference The Request Reference information element contains the random access reference value and the absolute frame number of the received access burst. The Access Delay is the delay of the access burst.

l

Time Advance This Time Advance information element provides the initial timing advance value. NOTE

If the BSC has no available channels, it sends the MS an Immediate Assignment Reject message or an Immediate Assignment Extend Reject message.

6.

l

After receiving the Immediate Assignment Reject message, the MS starts timer T3122 upon receiving one of the last three channel requests. Before timer T3122 expires, the MS is not permitted to access the network nor initiate access attempts except emergency calls in the same cell. It returns to idle mode and waits on the paging channel.

l

If the Immediate Assignment Reject message is received for the first time, the MS starts timer T3126. Timer T3126 starts when the number of Channel Request messages sent by the MS reaches the maximum value. When timer T3126 expires, the immediate assignment procedure fails.

The MS sends an SABM frame on the main DCCH. The SABM is a frame in the LAPDm protocol at the data link layer. It is the first frame to establish a multiple frame acknowledged mode. The messages on the Um interface come in two types, signaling messages and short messages. They are identified by the Service Access Point Identifier (SAPI). The service access point is the point at which the data link layer provides services to layer 3. SAPI 0 supports the transfer of signaling, and SAPI 3 supports the transfer of short messages. In the GSM network, an SABM frame carries a signaling message, the layer 3 service request message. The layer 3 service request message contains the identity of MS and indicates which service MS is requesting. The layer 3 service request messages are categorized into CM service requests, location update requests, IMSI detach, and paging responses. These messages contain the IMSI, detailed access cause, and classmarks.

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4 Immediate Assignment NOTE

The main DCCH is the primary signaling channel and is generally the SDCCH, FACCH, and SACCH.

7.

The BTS responds with a UA frame on the main DCCH. The UA frame is an unnumbered acknowledge frame of the LAPDm protocol at the data link layer. It confirms the SABM frame. When the Channel Request messages sent by two MSs have the same contents, the two MSs may be assigned the same dedicated channel. Upon receiving the SABM frame, the BTS sends the MS a UA frame that contains the same information as the received SABM frame. If the IMSI contained in the SABM frame is different from that in the UA frame, the MS leaves this channel and starts another access attempt. If the IMSI contained in the SABM frame is the same as that in the UA frame, the MS stays on the assigned channel.

8.

The BTS sends the BSC an Establish Indication message. This Establish Indication message indicates the establishment of a radio connection in multi-frame mode and contains parameters Link Identifier and L3 Information. The Link Identifier parameter identifies the signaling channel type and the message priority of SAPI and SAPI 0. The L3 Information parameter is a complete L3 message.

4.2 Internal BSC Signaling Procedure of Immediate Assignment This topic describes the internal BSC signaling procedure of immediate assignment. l

Upon receiving the Channel Required message from the BTS, the BSC assigns a signaling channel according to the specified channel type and channel algorithm.

l

During random access, upon receiving the Establish Indication message from the BTS, the BSC sends the MSC a CM Service Request message that carries the target CGI based on the MCC, MNC, LAC, and CI parameters in the Cell Attributes window.

4.3 Abnormal Immediate Assignment Cases This topic describes the abnormal immediate assignment cases. 4.3.1 Failure in Receiving an Establish Indication Message After Channel Activation This topic describes the fault, probable causes, and handling suggestions. 4.3.2 BSC Sending an Immediate Assignment Reject Message This topic describes the fault, probable causes, and handling suggestions.

4.3.1 Failure in Receiving an Establish Indication Message After Channel Activation This topic describes the fault, probable causes, and handling suggestions.

Fault The BSC sends the MS an Immediate Assignment Command message but does not receive an Establish Indication message from the BTS. 4-4


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Probable Causes The probable causes are as follows: 1.

The design of the MS does not comply with the protocols. The MS sends the Channel Request message for many times and the BSS assigns and activates multiple signaling channels.

2.

Even when the BSS is functional, the MS may send several Channel Request messages during one RR connection attempt. The BSS activates multiple signaling channels, but the MS uses only one of them. The BSC cannot receive the Establish Indication messages from other channels and therefore releases the channel after timer T3101 expires. If the number of slots for spread transmission (Tx-integer) is set properly, the reason may be that the BTS receives the uplink signals correctly but the MS cannot receive the downlink signals. Meanwhile, as indicated in the signaling tracing on the Um interface on the MS side, the BSC does not receive a response message from the BTS after sending a Channel Request message.

3.

The Tx-integer and the CCCH are not set correctly. The settings of the Tx-integer and the CCCH affect the interval at which an MS resends the Channel Request messages.

Handling Suggestions l

Use another MS to determine whether the problem lies in the MS itself.

l

Check whether the received level and received quality on the uplink and downlink are normal. If the MS is near the BTS, but the received level and received quality is low, check whether the antenna system, MS antenna, and MS battery are functional.

l

Check whether the Tx-integer and the CCCH are set correctly.

4.3.2 BSC Sending an Immediate Assignment Reject Message This topic describes the fault, probable causes, and handling suggestions.

Fault Upon receiving the Channel Required message, the BSC sends the MS an Immediate Assignment Reject message.


The BSC finds no suitable signaling channel, that is, a SDCCH or a TCH, to assign to the MS. This is because that the channels are busy or blocked.

2.

Upon receiving a Channel Activation message, the BTS sends the BSC many Channel Activation Negative Acknowledge messages.


Check whether the channels are busy or blocked and whether the TRXs are functional. Add TRXs to the BTS, modify the access threshold, and enable the directed retry.

l

Check whether the channel states on the BSC and the BTS are the same. If not, you can infer that the transmission on the Abis interface is unstable. Check also the BTS boards.

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5 Classmark Update

5

Classmark Update

About This Chapter The MS classmark specifies the service capability, supported frequency bands, power capability, and ciphering capability of an MS in the GSM network. It is categorized into classmark 1, classmark 2, and classmark 3. 5.1 Classmark Update Procedure This topic describes the classmark update procedure.

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5 Classmark Update

5.1 Classmark Update Procedure This topic describes the classmark update procedure.

Signaling Procedure Figure 5-1 shows the classmark update procedure. Figure 5-1 Classmark update procedure MS

BSS

MSC

System Information Type3 BCCH SABM SDCCH

Complete Layer 3 Inforamtion

Classmark Change(1) SDCCH

Classmark Update(2)

Classmark Request(3) Classmark Enquiry(4) main DCCH Classmark Change(5) main DCCH Classmark Update(6)

If the ECSC is allowed in System Information Type 3, an MS, for example, a dual-band MS or a vehicle mounted MS, can initiate a classmark update procedure by sending a Classmark Change message on the dedicated channel assigned by the network. The Classmark Change message carries the updated classmark 2 information element or even a classmark 3 information element.

5-2

1.

Upon receiving the Classmark Change message, the BSS sends the MSC a Classmark Update message. The Classmark Update message carries the classmark 2 and classmark 3 information elements. It is a bi-directional message.

2.

When an MM connection is established between the MS and the MSC, the MSC initiates a classmark update procedure by sending the BSS a Classmark Request message on an SCCP.

3.

Upon receiving the Classmark Request message, the BSS: l

Sends the MSC a Classmark Update message

l

Sends the MS a Classmark Enquiry message

l

Takes no action Huawei Technologies Proprietary

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4.

5 Classmark Update

Upon receiving the Classmark Enquiry message, the MS sends the BSS a Classmark Change message. The Classmark Change message has the same contents as the Classmark Change message described in 1.

Procedure Description l

Figure 5-1 is divided by the broken lines into three parts, in which the upper part indicate whether the ECSC is supported.

l

The middle part in Figure 5-1 shows the classmark update procedure initiated by the MS when the ECSC is allowed in System Information Type 3.

l

The lower part in Figure 5-1 shows the classmark update procedure initiated by the MSC.

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6 Location Update

6

Location Update

About This Chapter In the GSM system, MS location information is stored in the HLR, the VLR, and the MS. When the location information changes, relevant information in the HLR, the VLR, and the MS must be changed accordingly, which can be realized through the location update procedure. 6.1 Location Update Procedure The location update procedure is a general procedure and is used for generic location update, periodic update, and IMSI attach. 6.2 Internal BSC Signaling Procedures of Location Update This describes the internal BSC signaling procedures of location update. 6.3 Abnormal Location Update Cases This topic describes the abnormal location update cases.

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6 Location Update

6.1 Location Update Procedure The location update procedure is a general procedure and is used for generic location update, periodic update, and IMSI attach. 6.1.1 Periodic Update Procedure Periodic update is used to periodically notify the network of the MS availability. 6.1.2 IMSI Attach Procedure The IMSI attach procedure is the complement of the IMSI detach procedure. It is used to indicate the IMSI as active in the network. 6.1.3 Generic Location Update Procedure This topic describes the generic location update procedure.

6.1.1 Periodic Update Procedure Periodic update is used to periodically notify the network of the MS availability. Periodic update is used to periodically notify the network of the MS availability. The location update type information element in the Location Updating Request message indicates periodic update. The periodic location update procedure is controlled by timer T3212 in the MS. If the timer is not started, it is started each time the MS enters the Normal Service or Attempting to Update state of the MM Idle state. When the MS leaves the MM Idle state, timer T3212 continues running until it expires. The MM Idle state indicates that the MS is not activated, is in the interception state, and does not process any call procedure. Timer T3212 is stopped (is set to its initial value 0 for the next start) when: l

A Location Updating Accept or Location Updating Reject message is received.

l

An Authentication Reject message is received.

l

The first MM message such as the Location Updating Accepted and the CM Service Accept message is received, or ciphering mode setting is complete when the MM connection is set up, except when the most recent service state is Limited Service.

l

The MS has responded to paging and has received the first correct layer 3 message except the RR message.

l

Timer T3212 expires.

l

The MS is deactivated, that is, the MS is switched off or the SIM is removed.

When timer T3212 expires, the following cases might occur:

6-2

l

The location update procedure is started and the timer shall be set to its initial value for the next start.

l

If the MS is in other states than MM Idle, the location update procedure is delayed until the MS enters the MM Idle state.

l

If the MS is in the No Cell Available, Limited Service, PLMN Search, or PLMN SearchNormal Service state, the location update procedure is delayed until the MS leaves the service state. Huawei Technologies Proprietary

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6 Location Update

If the system information indicates that periodic location update shall not be used, the procedure is not started. The timeout value is carried by the Control Channel Description IE in the System Information Type 3 message.

The T3212 timeout value is not changed in the No Cell Available, Limited Service, PLMN Search, or PLMN Search-Normal Service states. When the timeout value is changed during serving cell change and the timer is running, the MS restarts the timer with the value t modulo t1. t1 is the new T3212 timeout value, and t is the current timer value. When timer T3212 stops, the MS restarts the timer with a random value between between 1 and t1.

6.1.2 IMSI Attach Procedure The IMSI attach procedure is the complement of the IMSI detach procedure. It is used to indicate the IMSI as active in the network. The System Information Type 3 message carries an ATT flag that indicates whether the attach and detach procedures are required to be used or not. If the IMSI attach and detach procedures are required by the network, the MS will trigger the IMSI attach procedure during IMSI activation. When the MS activates the IMSI within the network coverage area or moves into the coverage area, the IMSI attach procedure is triggered only when the Update Status is Updated and the stored LAI is the same as that broadcast on the BCCH of the current serving cell. Otherwise, a generic location update procedure is triggered, which is independent of the ATT flag indication. IMSI attach is performed through the generic location update procedure. The location update type information element in the Location Updating Request message must in this case indicate IMSI attach.

6.1.3 Generic Location Update Procedure This topic describes the generic location update procedure. The generic location update procedure is as follows: l

Network requesting additional MS capability information The network may initiate a classmark interrogation procedure to obtain the MS capability information such as the encryption capability and the short message transmission and reception capability.

l

Network requesting for identification The network may initiate an identification request procedure if it cannot get the IMSI from the TMSI and LAI or it requires the IMEI.

l

Authentication by the network The authentication procedure may be initiated by the network upon receipt of the Location Updating Request message from the MS.

l

Ciphering mode setting by the network The ciphering mode setting procedure may be initiated by the network if a new TMSI has to be allocated.

l

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Attempt counter Huawei Technologies Proprietary

6-3


6 Location Update

To limit the number of location update attempts, when a location update fails, an attempt counter is used. The counter counts the number of consecutive unsuccessful location update attempts and increases by 1 when a location update fails. The attempt counter is reset when: –

The MS is switched on.

–

A SIM is inserted.

–

A location update is complete.

–

A location update with the cause value 11 (PLMN not Allowed), 12 (Location Area not Allowed), 13 (Roaming not Allowed in This Location Area), or 15 (No Suitable Cells in Location Area) is complete.

–

The service state changes from Attempting to Update.

–

The MS enters a new location area.

–

Timer T3212 expires.

–

The location update is triggered by the CM sublayer requests.

The attempt counter is used to decide whether a location update needs to be initiated after timer T3211 expires. l

Location update not accepted by the network If the location update is not accepted, the network sends a Location Updating Reject message to the MS. The MS receiving a Location Updating Reject message stops timer T3210, stores the reject cause, starts timer T3240, enters state Location Updating Rejected, and awaits the release of the RR connection triggered by the network. It deletes the Equivalent PLMNs list when the reject cause is not #12, #14, or #15. Upon the release of the RR connection, the MS takes the following actions depending on the stored reject cause: –

# 2 (IMSI Unknown in HLR)

–

# 3 (Illegal MS)

–

# 6 (Illegal ME)

If the reject value is #2, #3, or #6, the MS sets the update state to Roaming Not Allowed, deletes any TMSI, stored LAI, and ciphering key sequence number, and considers the SIM as invalid until it is switched off or the SIM is removed. –

# 11 (PLMN not Allowed)

–

# 12 (Location Area not Allowed)

–

# 13 (Roaming not Allowed in This Location Area)

–

# 15 (No Suitable Cells in Location Area)

If the reject value is #11, #12, #13, or #15, the MS deletes any LAI, TMSI, and ciphering key sequence number stored in the SIM, resets the attempt counter, and sets the update state to Roaming Not Allowed. The MS stores the LAI and the PLMN identity in a suitable forbidden list, for example, in the Forbidden PLMN List for cause #11, in the list of Forbidden Location Areas for Regional Provision of Service for cause #12, in the list of Forbidden Location Areas for Roaming for cause #13 (The MS performs a PLMN selection instead of a cell selection when it returns to the MM Idle state), and in the list of Forbidden Location Areas for Roaming for cause #15 (The MS searches a suitable cell in a location area of the same PLMN). Other reject values are considered as abnormal cases. 6-4


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Release of the RR connection after location update When the location update procedure is complete, the MS (except when it has a follow-on application request and has received the proceed indication from the network) sets timer T3240 and enters the Wait For Network Command state, expecting the release of the RR connection. The network may keep the RR connection for a network-initiated MM connection, or may allow a mobile-initiated MM connection. Any release of the RR connection is initiated by the network. If the RR connection is not released within a given time controlled by timer T3240, the MS aborts the RR connection. Then the MS enters the MM Idle state. When the MS enters the Normal Service or Attempting to Update state, either timer T3212 or timer T3211 is started.

6.2 Internal BSC Signaling Procedures of Location Update This describes the internal BSC signaling procedures of location update. On receiving the Channel Required message from the BTS, the BSC assigns a signaling channel. During random access, on receiving the Establish Indication message from the BTS, the BSC sends the MSC a Location Updating Request message that carries the target CGI based on the MCC, MNC, LAC, and CI parameters in the Cell Attributes window. NOTE

You can find the periodic location update time in the Periodic Location Update Time Limit by selecting Idle Mode in the Cell Attributes window. The periodic location update time is delivered to the MS in the System Information Type 3 message.

6.3 Abnormal Location Update Cases This topic describes the abnormal location update cases. 6.3.1 Location Update Not Started or Aborted on the MS Side This topic describes the fault, probable causes, and handling suggestions. 6.3.2 Location Update Failure on the Network Side This topic describes the fault, probable causes, and handling suggestions.

6.3.1 Location Update Not Started or Aborted on the MS Side This topic describes the fault, probable causes, and handling suggestions.

Fault The location update procedure is not started or is aborted.

Probable Causes The probable causes are as follows: l

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Access barred because of access class control Huawei Technologies Proprietary

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6 Location Update

The location update procedure is not started. The MS stays in the current serving cell and starts the normal cell reselection procedure. It starts the location update procedure as soon as it gains access or at cell change. l

Receiving an Immediate Assignment Reject message during random access (in A/Gb mode only) The location update procedure is not started. The MS stays in the chosen serving cell and starts the normal cell selection procedure. The waiting timer T3122 is reset when a cell change occurs. The location update procedure is started as soon as timer T3122 expires.

l

Random access failure (in A/Gb mode only) Timer T3213 is started when random access fails. When it expires, the procedure is attempted again if still necessary. If two successive random access attempts fail, the location update procedure attempt is aborted.

l

RR connection failure The location update procedure is aborted.

l

T3212 expiry The location update procedure and the RR connection are aborted.

l

RR release before the normal end of procedure The location update procedure is aborted.

l

RR connection establishment failure (in Iu mode only)

Handling Suggestions Refer to 4.1 Immediate Assignment Procedure. Based on the cause values carried by the Location Updating Rejected message, you can also refer to the following suggestions: l

Cause values #2, #3, #6, #11, #12, and #13 Check whether the subscription information in the HLR and the subscriber data in the VLR is correct.

l

Cause value #15 Check whether the CGI and the LAC are consistent and correct on the MSC and the BSC.

6.3.2 Location Update Failure on the Network Side This topic describes the fault, probable causes, and handling suggestions.

Fault Location update fails, and the network sends a Location Updating Reject message.


RR connection failure If an RR connection fails during a common procedure integrated with the location update procedure, the behavior of the network is the same as that in a common procedure. If an RR connection fails when a common procedure does not exist, the location update procedure towards the MS is aborted.

2. 6-6

Location update not accepted by the network Huawei Technologies Proprietary

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If the Location Updating Request message is received with a protocol error, the network returns a Location Updating Reject message with one of the following reject causes: l

#03 (Illegal MS)

l

#97 (Message Type Non-Existent or not Implemented)

l

#98 (Message Type not Compatible with the Protocol State)

l

#111 (Protocol Error, Unspecified)

Upon sending the response, the network starts the channel release procedure. 3.

Network failure If the MSC, VLR, or HLR is faulty, the network sends a Location Updating Reject message with the cause value #17 (Network Failure). Generally, if the CGI or the LAC are not consistent on the MSC and the BSC, the cause value may also be #17.

Handling Suggestions Refer to 4.1 Immediate Assignment Procedure. If the cause value is #17, refer to the following suggestions: 1.

Check whether the CGI and the LAC are consistent on the MSC and the BSC, especially whether the both the LAC and the CI are decimal or hexadecimal.

2.

Check the hardware of the MSC, VLR, or HLR.

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7 Authentication

7

Authentication

About This Chapter The purpose of authentication is to permit the network to check whether the identity provided by the MS is acceptable or not and to prevent the private information of the legal subscribers from being stolen. 7.1 Authentication Principles The authentication procedure is always initiated and controlled by the network. 7.2 Authentication Procedure This topic describes the authentication procedure. 7.3 Authentication Failure Different ways of identification used by the MS may lead to different unsuccessful authentication procedures. 7.4 Internal BSC Signaling Procedure of Authentication This topic describes the internal BSC signaling procedure of authentication. 7.5 Abnormal Authentication Cases This topic describes the abnormal authentication cases.

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7 Authentication

7.1 Authentication Principles The authentication procedure is always initiated and controlled by the network. The network initiates the authentication procedure in the following cases: l

The MS applies to change the subscriber information in the VLR or the HLR.

l

Service access is initiated. For example, when the MS originates a call, is called, activated, or deactivated, or the supplementary service is initiated.

l

The MS accesses the network for the first time after the MSC/VLR restarts.

l

The ciphering key Kc on the network does not match that on the MS.

The purpose of authentication twofold: l

To permit the network to check whether the identity provided by the MS is acceptable or not

l

To provide parameters that enable the MS to calculate a new ciphering key

The authentication procedure uses an Authentication Triplet, namely RAND, Kc, and SERS. The Authentication Triplet is calculated in the authentication center of the GSM network. When registering in a GSM network, each subscriber is assigned a Mobile Station International ISDN Number (MSISDN) and an International Mobile Subscriber Identity (IMSI). The IMSI is written into the SIM through a SIM writer. The SIM writer also generates an authentication parameter Ki, which is stored in the SIM and the authentication center as well. The IMSI and Ki are permanent information. A pseudo-random number generator is used in the authentication center to generate an unpredictable pseudo random number RAND. In the authentication center, the RAND and Ki generate a signed response (SRES) through algorithm A3 and a ciphering key Kc through algorithm A8. The three parameters RAND, Kc, and SERS constitute an Authentication Triplet, which are stored as part of the subscriber data in the HLR. Generally, the authentication center sends five groups of Authentication Triplet to the HLR at one time. The HLR automatically stores them. The HLR can store ten groups of Authentication Triplet. Upon request, the HLR sends five groups of Authentication Triplet to the MSC/VLR at one time. The MSC/VLR uses the Authentication Triplet one by one. When only two groups are left, the MSC/VLR requests the HLR for the Authentication Triplet again.

7.2 Authentication Procedure This topic describes the authentication procedure. Figure 7-1 shows the authentication procedure.

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Figure 7-1 Authentication procedure MS

BTS

BSC

MSC

Authentication Request(1) SDCCH Start T3260 Authentication Response(2) SDCCH StopT3260

The authentication procedure is as follows: 1.

The network initiates an authentication procedure by sending an Authentication Request message to the MS and starts timer T3260. The Authentication Request message carries a 128-bit RAND that is used to calculate the response parameters. It also carries the Ciphering Key Sequence Number (CKSN) assigned to the ciphering key.

2.

Upon receiving the Authentication Request message, the MS calculates the SRES required by the Authentication Response message and the new ciphering key Kc. The SRES is calculated based on the RAND and Ki through algorithm A3. After writing the new ciphering key Kc and the CKSN in the SIM, the MS sends the network an Authentication Response message. Upon receiving the Authentication Response message, the network stops timer T3260 and compares the stored SRES with the SRES in the Authentication Response message. If the SRESs are the same, the authentication procedure is complete, and the successive procedures, for example, the ciphering procedure, start.

7.3 Authentication Failure Different ways of identification used by the MS may lead to different unsuccessful authentication procedures. If authentication fails, that is, if the response is not valid, the network may distinguish between the following two ways of identification used by the MS: 1.

If the TMSI is used, the network initiates the identification procedure. If the IMSI given by the MS differs from that in the network, the network restarts the authentication procedure. If the IMSI given by the MS is the expected one, the network returns an Authentication Reject message.

2.

if the IMSI is used, the network sends an Authentication Reject message. Figure 7-2 shows the unsuccessful authentication procedure.

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7 Authentication

Figure 7-2 Unsuccessful authentication procedure MS

BTS

BSC

MSC

Authentication Request(1) SDCCH Authentication Response(2) SDCCH Authentication Reject(3) SDCCH

If the Authentication Reject message is received when the MS is in the IMSI Detach Initiated state, timer T3220 will be stopped when the RR connection is released. The MS, if possible, starts the local release procedure after the normal release procedure or timer T3220 expiry. If not possible, for example, during IMSI detachment at MS power-down, the RR sublayer on the MS side is aborted. If the Authentication Reject message is received in any other state, the MS aborts any MM connection establishment or call re-establishment procedure, stops all the timers T3210 or T3230, releases all the MM connections, starts timer T3240, and enters the Wait For Network Command state, expecting the release of the RR connection. If the RR connection is not released within a given time controlled by timer T3240, the MS aborts the RR connection. In both cases, either after an RR connection release triggered from the network or after an RR connection abort requested by the MS, the MS enters the No IMSI substate of the MM Idle state.

7.4 Internal BSC Signaling Procedure of Authentication This topic describes the internal BSC signaling procedure of authentication. The authentication is initiated and controlled by the MSC, and the BSC does no special processing.

7.5 Abnormal Authentication Cases This topic describes the abnormal authentication cases. 7.5.1 RR Connection Failure This topic describes the fault, probable causes, and handling suggestions. 7.5.2 Timer T3260 Expiry This topic describes the fault, probable causes, and handling suggestions. 7.5.3 SIM Unregistered This topic describes the fault, probable causes, and handling suggestions.

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7.5.1 RR Connection Failure This topic describes the fault, probable causes, and handling suggestions.

Fault The authentication procedure fails, and the network releases all the MM connections.

Probable Causes Upon detecting an RR connection failure before an Authentication Response message is received, the network releases all the MM connections (if any) and aborts any ongoing MMspecific procedure.

Handling Suggestions Check whether interference exists on the Um interface.

7.5.2 Timer T3260 Expiry This topic describes the fault, probable causes, and handling suggestions.

Fault The authentication procedure fails.

Probable Causes If timer T3260 expires before an Authentication Response message is received, the network releases the RR connection and all the MM connections, aborts the authentication procedure and all the ongoing MM connections (if any), and starts the RR connection release procedure.

Handling Suggestions Check whether the timeout value of timer T3260 is appropriate.

7.5.3 SIM Unregistered This topic describes the fault, probable causes, and handling suggestions.

Fault The network directly responds to the MS with an Authentication Reject message.

Probable Causes If the SIM of an MS is not registered in the network, the network returns an Authentication Reject message to the MS.

Handling Suggestions Register the SIM correctly. Issue 01 (2007-11-26)


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8 Ciphering

8

Ciphering

About This Chapter Ciphering is used to secure the information exchange between an MS and a BTS. The information consists of the signaling information and the subscriber information. The subscriber information consists of the subscriber data and the subscriber voice. 8.1 Ciphering Procedure Whether ciphering is used or not is determined by the radio resource management entity. The ciphering procedure is initiated by the network and is performed in the BTS. To cipher the user data, you must enter the corresponding parameters in the ciphering program. The ciphering key Kc is generated by the AUC, is stored in the MSC/VLR, and is sent to the BTS before ciphering. 8.2 Ciphering Mode Change The MSC sends a Ciphering Mode Change command, and the BTS performs the ciphering mode change. 8.3 Internal BSC Signaling Procedure of Ciphering This topic describes the internal BSC signaling procedure of ciphering. 8.4 Abnormal Ciphering Cases This topic describes the abnormal ciphering cases.

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8 Ciphering

8.1 Ciphering Procedure Whether ciphering is used or not is determined by the radio resource management entity. The ciphering procedure is initiated by the network and is performed in the BTS. To cipher the user data, you must enter the corresponding parameters in the ciphering program. The ciphering key Kc is generated by the AUC, is stored in the MSC/VLR, and is sent to the BTS before ciphering.

Signaling Procedure Figure 8-1 shows the ciphering procedure. Figure 8-1 Ciphering procedure MS

BTS

Ciphering Mode Command(3)

BSC Encryption Mode Command(2)

MSC Ciphering Mode Command(1)

SDCCH Ciphering Mode Command(4) SDCCH

Ciphering Mode Command(5)

The ciphering procedure is as follows: 1.

The MSC sends the BSC a Ciphering Mode Command message. The Ciphering Mode Command message carries the required ciphering algorithms including A5/0, the ciphering key Kc, and whether the Ciphering Mode Complete message sent by the MS must carry the IMEI.

2.

According to the ciphering algorithm in the Ciphering Mode Command message, the ciphering algorithm allowed by the BSC, and the ciphering algorithm supported by the MS, the BSC determines the algorithm to be used and notifies the BTS.

3.

The BTS sends the Ciphering Mode Command message to notify the MS of the ciphering algorithm.

4.

Upon receiving the Ciphering Mode Command message, the MS starts sending the ciphering mode and then responds the BSC with a Cipher Mode Complete message.

5.

Upon receiving the Ciphering Mode Complete message from the MS, the BSC notifies the MSC of the ciphering completion.

Procedure Description For details about the ciphering procedure, refer to the following: l

A5 ciphering algorithm As specified in the GSM protocol, there are eight ciphering algorithms, A5/0–A5/7, in which A5/0 indicates Not Ciphered. The ciphering mode setting procedure is initiated by

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8 Ciphering

the network. The required ciphering algorithm is specified in the Ciphering Information element of the Ciphering Mode Command message. l

Ciphering algorithm selection When an MS initiates a call, it sends a CM Service Request message that carries classmark 2, classmark 3, and the ciphering algorithm supported by the MS. When the ECSC is set to 1, classmark 3 is carried in the CM Service Request message. When the ECSC is set to 0, classmark 3 can only be carried in the CM Service Request message through classmark change or update. Therefore, set the ECSC to 1 when ciphering is used. According to the ciphering algorithm in the Cipher Mode Command message, the ciphering algorithm allowed by the BSC, and the ciphering algorithm in the CM Service Request message, the BSC determines the algorithm to be used. In a reverse order, the BSC selects an applicable algorithm from the intersection of the early-mentioned three algorithms. The priority of the algorithms is A5/7 > A5/6 > A5/5 > A5/4 > A5/4 > A5/3 > A5/2 > A5/1 > A5/0.

l

Ciphering during handover The Handover Request message carries an Ciphering Information element. The Ciphering Information element specifies the required ciphering algorithm and the ciphering key. If one of the two A interfaces of the two BSSs is in PHASE I, because of the defects in the ETSI GSM PHASE I protocol (no ciphering mode setting information unit is included in the Handover Command message), the two BSSs interoperate only when they use the same ciphering algorithm such as A5/0 or A5/2. Otherwise, special processing (modifying the inter-BSC handover command) is required in the target MSC or the target BSC (or the serving MSC or the serving BSC). During the interconnection on the A interface in ciphering mode, to avoid unsuccessful handovers, you must know whether additional data configuration is required on the BSCs and MSCs from different manufacturers.

8.2 Ciphering Mode Change The MSC sends a Ciphering Mode Change command, and the BTS performs the ciphering mode change. The BTS performs and manages ciphering. The BSC does no processing. If the ciphering mode is changed, 1.

The BTS performs the sending configuration in old mode and the receiving configuration in new mode.

2.

The MS is configured in a completely new mode, including transmission and reception.

3.

The BTS is configured in a completely new mode.

8.3 Internal BSC Signaling Procedure of Ciphering This topic describes the internal BSC signaling procedure of ciphering. The internal BSC signaling procedure of ciphering is as follows: 1.

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Upon receiving the Ciphering Mode Command message from the MSC, the BSC checks the classmarks of the MS and the settings of the Ciphering Algorithm in the Cell Attributes dialog box.


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8 Ciphering

2.

According to the ciphering algorithm in the Ciphering Mode Command message, the ciphering algorithm allowed by the BSC, and the ciphering algorithm in the CM Service Request message, the BSC determines the algorithm to be used.

3.

In a reverse order, the BSC selects an applicable algorithm from the intersection of the early-mentioned three algorithms. The priority of the algorithms is A5/7 > A5/6 > A5/5 > A5/4 > A5/4 > A5/3 > A5/2 > A5/1 > A5/0. The determined ciphering mode is carried in the Cipher Mode Command message that is sent to the BTS.

8.4 Abnormal Ciphering Cases This topic describes the abnormal ciphering cases. 8.4.1 BSS Sending a Cipher Mode Reject Message This topic describes the fault, probable causes, and handling suggestions. 8.4.2 MS Doing No Processing This topic describes the fault, probable causes, and handling suggestions.

8.4.1 BSS Sending a Cipher Mode Reject Message This topic describes the fault, probable causes, and handling suggestions.

Fault The BSS sends the MSC a Cipher Mode Reject message.


The BSS does not support the ciphering algorithm specified in the Ciphering Mode Command message. It sends the MSC a Cipher Mode Reject message with the cause value Ciphering Algorithm Not Supported.

2.

If the BSS has initiated ciphering before the MSC requires changing the ciphering algorithm, the BSS sends the MSC a Cipher Mode Reject message.


Check whether the BSS supports the ciphering algorithm specified in the Ciphering Mode Command message.

l

Check whether the BSS has initiated ciphering.

8.4.2 MS Doing No Processing This topic describes the fault, probable causes, and handling suggestions.

Fault Upon receiving the Ciphering Mode Command message, the MS does no processing.

Probable Causes The Ciphering Mode Command message is considered valid when: 8-4


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l

It carries an Algorithm Identifier and is received by the MS in No Ciphering mode.

l

It carries No Algorithm Identifier and is received by the MS in No Ciphering mode.

l

It carries No Algorithm Identifier and is received by the MS in Ciphering mode.

The Ciphering Mode Command message received in other cases, for example, when it carries an Algorithm Identifier and is received in Ciphering mode, is considered erroneous. In this case, the MS sends an RR Status message with the cause value Protocol Error and does no further processing.

Handling Suggestions Check the mode that the MS is in and the Ciphering Mode Command message.

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9 TMSI Reallocation

9

TMSI Reallocation

About This Chapter The TMSI reallocation takes place in ciphering mode. It is generally related to another procedure, such as location update or call establishment. 9.1 TMSI Reallocation Procedure The purpose of the TMSI reallocation procedure is to provide identity confidentiality, that is, to protect a user against being identified and located by an intruder. Usually, the TMSI reallocation is performed at least at each change of a location area. It can be initiated at any time by the network if an RR connection exists between the network and an MS. 9.2 Internal BSC Signaling Procedure of TMSI Reallocation This topic describes the internal BSC signaling procedure of TMSI reallocation. 9.3 Abnormal TMSI Reallocation Cases This topic describes the abnormal TMSI reallocation cases.

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9 TMSI Reallocation

9.1 TMSI Reallocation Procedure The purpose of the TMSI reallocation procedure is to provide identity confidentiality, that is, to protect a user against being identified and located by an intruder. Usually, the TMSI reallocation is performed at least at each change of a location area. It can be initiated at any time by the network if an RR connection exists between the network and an MS. Figure 9-1 shows the TMSI reallocation procedure. Figure 9-1 TMSI reallocation procedure MS

BTS

BSC

MSC

TMSI Reallocation Command(1) SDCCH

TMSI Reallocation Complete(2)

Start T3250

SDCCH StopT3250

The TMSI reallocation procedure is as follows: l

The network initiates the TMSI reallocation procedure by sending a TMSI Reallocation Command message to the MS and starts timer T3250. The TMSI Reallocation Command message carries a new combination of TMSI and LAI allocated by the network or an LAI and the IMSI if the used TMSI is deleted. Usually, the TMSI Reallocation Command message is sent to the MS using an RR connection in ciphering mode.

l

Upon receiving the TMSI Reallocation Command message, the MS stores the LAI in the SIM. If the received identity is the IMSI of the relevant MS, the MS deletes any TMSI. If the received identity is a TMSI, the MS stores the TMSI in the SIM. In both cases, the MS sends a TMSI Reallocation Complete message to the network. Upon receiving the TMSI Reallocation Complete message, the network stops timer T3250. If a TMSI is sent to the MS, the network considers the new TMSI as valid. If an IMSI is sent to the MS, the network considers the old TMSI as deleted.

9.2 Internal BSC Signaling Procedure of TMSI Reallocation This topic describes the internal BSC signaling procedure of TMSI reallocation. The network initiates and controls the TMSI reallocation procedure and the BSC does no special processing.

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9.3 Abnormal TMSI Reallocation Cases This topic describes the abnormal TMSI reallocation cases. 9.3.1 TMSI Reallocation Caused by RR Connection Failure on the Network Side This topic describes the fault, probable causes, and handling suggestions. 9.3.2 TMSI Reallocation Caused by T3250 Expiry This topic describes the fault, probable causes, and handling suggestions.

9.3.1 TMSI Reallocation Caused by RR Connection Failure on the Network Side This topic describes the fault, probable causes, and handling suggestions.

Fault The TMSI is reallocated due to RR connection failure on the network side.

Probable Causes If the RR connection fails before the TMSI Reallocation Complete message is received, all MM connections should be released and both the old and the new TMSIs should be considered as occupied for a certain recovery time. During this period the network may: l

Use the IMSI for paging if the MS is the called party. Upon response from the MS, the TMSI reallocation is restarted.

l

Consider the new TMSI as valid if the MS is the calling party.

Initiate an identification procedure followed by a new TMSI reallocation if the MS uses the old TMSI.

Handling Suggestions No handling is required.

9.3.2 TMSI Reallocation Caused by T3250 Expiry This topic describes the fault, probable causes, and handling suggestions.

Fault The network releases the RR connection.

Probable Causes The TMSI reallocation is supervised by the timer T3250 in the network. At the first expiry of timer T3250, the network releases the RR connection. In this case, the network aborts the reallocation procedure, releases all MM connections, and follows the rules for RR connection failure. Issue 01 (2007-11-26)


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Handling Suggestions The BSC does no special processing.

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10 Speech Channel Assignment

Speech Channel Assignment

About This Chapter The speech channel assignment is the procedure for assigning TCHs to the MS according to the service requests. 10.1 Speech Channel Assignment Procedure This topic describes the speech channel assignment procedure. 10.2 Channel Mode Modification Procedure This topic describes the channel mode modification procedure. 10.3 Internal BSC Signaling Procedure of Speech Channel Assignment This describes the internal BSC signaling procedure of speech channel assignment. 10.4 Abnormal Speech Channel Assignment Cases This topic describes the abnormal speech channel assignment cases.

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10.1 Speech Channel Assignment Procedure This topic describes the speech channel assignment procedure. Figure 10-1 shows the speech channel assignment procedure. Figure 10-1 Speech channel assignment procedure MS

BTS

BTS

BSC Assignment Request(1) Start T10

Channel Activation(2) Channel Activation Acknowledge(3) Assignment Command(4) main DCCH Start T3107 SABM(5) FACCH

Establishment Indication(7)

UA(6) FACCH Assignment Complete(8) FACCH Stop T3107 Assignment Complete(9)

Stop T10

The speech channel assignment procedure is as follows: 1.

10-2

The MSC requests the radio resources from the BSS through the SCCP connection and starts timer T10. The Assignment Request message carries the Channel Type, Priority, Circuit Identity Code, and Downlink DTX Flag. l

The Channel Type parameter has five to ten bytes. The third byte "speech / data indicator" indicates speech, data, or signaling. The fourth byte "channel rate and type" indicates the number of half-rate channels or full-rate channels and the number of related physical channels. The remaining bytes indicate speech versions 1–5.

l

The Priority parameter indicates different priority levels and whether queuing and preemption is performed.


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l

The Circuit Identity Code parameter is used for the physical connection between the BSC and the MSC.

l

The Downlink DTX Flag parameter indicates whether discontinuous transmission is allowed.

2.

For details about the Channel Activation message, refer to 4 Immediate Assignment.

3.

For details about the Channel Activation Acknowledge message, refer to 4 Immediate Assignment.

4.

Upon receiving the Channel Activation Acknowledge message, the BSC sends the MS an Assignment Command message on the SDCCH and starts timer T3107. The Assignment Command message carries the Channel Description, Power Command, and Channel Mode. For details about these parameters, refer to the immediate assignment procedure.

5.

Upon receiving the Assignment Command message from the BTS, the MS adjusts the signaling to the TCH and sends the SABM frame on the FACCH. The SABM frame is the first frame during the setup of multi-frame verification mode and does not carry layer 3 messages.

6.

Upon receiving the SABM frame, the BTS responds to the MS with a UA frame on the FACCH. The UA frame does not carry layer 3 messages.

7.

Then the BTS sends the BSC an Establishment Indication message. The Establishment Indication message does not carry layer 3 messages. The system responds with a UA Acknowledgement frame.

8.

Upon receiving the UA frame, the MS sends an Assignment Complete message on the FACCH to notify the BSC of the channel assignment completion. Then it stops Timer T3107.

9.

The BSC sends the MSC the Assignment Complete message and stops timer T10. The Assinment Complete message carries the Chosen Channel, Circuit Pool, and Speech version. The meanings of the parameters are as follows: l

Chosen Channel Inidicates the type of the assigned channel

l

Circuit Pool Indicates the circuit pool information

l

Speech Version Indicates the speech coding algorithm

10.2 Channel Mode Modification Procedure This topic describes the channel mode modification procedure. Figure 10-2 shows the channel mode modification procedure.

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Figure 10-2 Channel mode modification procedure MS

BTS

BSC

MSC Assignment Request(1) Start T10

Mode Modify(2) Mode Modify Acknowledge(3) Channel Mode Modify(4) main DCCH Channel Mode Modify Acknowledge(5) main DCCH

Assignment Commplete(6) StopT10

The channel mode modification procedure is as follows: 1.

For details about the Assignment Request message, refer to 10.1 Speech Channel Assignment Procedure.

2.

Upon receiving the Assignment Request message, the BSC sends the BTS a Mode Modify message. The Mode Modify message carries the Channel Mode parameter.

3.

If the channel mode is changed, the BTS sends the BSC a Mode Modify Acknowledge message to the BSC. If the channel mode cannot be changed, the BTS sends the BSC a Mode Modify Negative Acknowledge message.

4.

Upon receiving the Mode Modify Acknowlege message, the BSC sends the MS a Channel Mode Modify message. The Channel Mode Modify message carries the information of the channel to be changed and the mode of channel after change.

5.

If the channel mode is changed, the MS sends the BSC a Channel Mode Modify Acknowledge message. If the MS does not support the specified mode, it stays in the original mode. The Channel Mode Modify Acknowledge message carries the mode information.

6.

For details about the Assignment Complete message, refer to 10.1 Speech Channel Assignment Procedure.

10.3 Internal BSC Signaling Procedure of Speech Channel Assignment This describes the internal BSC signaling procedure of speech channel assignment. The internal BSC signaling procedure of speech channel assignment is as follows: 1.

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On receiving the Assignment Request message from the MSC, the BSC checks the channel type. Choose Other Attributes > Advanced > Other Parameters. Check whether the Huawei Technologies Proprietary

Issue 01 (2007-11-26)



Data Service Allowed is enabled. If not, the BSC responds with an Assignment Failure message. 2.

Based on the CIC in the Assignment Request message, the BSC checks the E1 timeslots on the A interface and confirms the existence of CIC. It also checks whether the circuit pool of the configured CIC, the channel type in the Assignment Request message, and the capacity of the GDPUT are collided. If they are collided, the BSC responds with an Assignment Failure message.

3.

On receiving the Assignment Complete message from the MS, the BSC fills the message with the A Interface Tag and sends the message to the MSC. You can choose BSC Property > Basic Data to display the A Interface Tag.

10.4 Abnormal Speech Channel Assignment Cases This topic describes the abnormal speech channel assignment cases. 10.4.1 BSC Sending an Assignment Failure Message This describes the fault, probable causes, and handling suggestions. 10.4.2 BSC Receiving a Connection Failure Indication Message This topic describes the fault, probable causes, and handling suggestions. 10.4.3 BSC Receiving an Error Indication Message This topic describes the fault, probable causes, and handling suggestions.

10.4.1 BSC Sending an Assignment Failure Message This describes the fault, probable causes, and handling suggestions.

Description Upon receiving the Assignment Request message, the BSC responds with an Assignment Failure message.

Analysis The probable causes are as follows: 1.

Radio Interface Message Failure The MS fails to access the speech channel. It sends an Assignment Failure message on the signaling channel. Due to the particularity of the transmission on the Um interface, this case happens the most frequently and cannot be solved.

2.

Equipment Failure The BSC hardware is faulty.

3.

No Radio Resource Available The BSC has no appropriate speech channels for assignment. The possible reason is that all the speech channels are busy or that the speech channels are blocked.

4.

Requested Terrestrial Resource Unavailable

5.

Requested Transcoding/Rate Adaption Unavailable

6.

Terrestrial Resource Already Allocated

7.

Invalid Message Contents

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8.

Radio Interface Failure - Reversion To Old Channel

9.

Requested Speech Version Unavailable

10. Timer T3107 expiry

Handling Suggestions The respective handling suggestions are as follows: l

Check the access-related parameters of the antenna system, BTS boards, and BSC data configuration.

l

Check the following: –

Communication between modules and subracks in the BSC

–

Communication on the A interface, for example, the cable connections between GEIUAs and subracks

l

Add TRXs to the BTS, modify the access threshold, and enable the directed retry.

l

The circuits on the A interface on the BSC side are abnormal, for example, the CIC in the Assignment Request message is not available. Check the consistency of the A interface data on the MSC and the BSC. Check also the CIC state.

l

Check the transmission on the A interface.

l

Check whether the CIC configuration on the BSC and the MSC is consistent. If not, manually reset the CIC on the BSC6000 Local Maintenance Terminal.

l

Check whether the message conforms to the protocols.

l

Check the environment quality on the Um interface. For example, check the quality of the level.

l

Check whether the BSC supports the requested speech version.

l

Check whether the timeout value of timer T3107 is appropriate.

10.4.2 BSC Receiving a Connection Failure Indication Message This topic describes the fault, probable causes, and handling suggestions.

Fault During the assignment procedure, the BSC receives a Connection Failure Indication message.


Radio link failure

l

Hardware failure

Handling Suggestions The handling suggestions are as follows: l

Check the resources on the Um interface.

l

Check the following: –

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Communication between subracks Huawei Technologies Proprietary

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HUAWEI BSC6000 Base Station Subsystem BSS Signaling Analysis Guide –


Communication on the A interface, for example, the cable connections between GEIUBs and subracks

10.4.3 BSC Receiving an Error Indication Message This topic describes the fault, probable causes, and handling suggestions.

Fault During the assignment procedure, the BSC receives an Error Indication message.


Protocol disconformity

l

Link layer failure

l

Timer T200 expiry

l

MS failure in receiving a UA frame


Check the contents of the frames at the data link layer.

l

Check the status of the data link layer.

l

Check the timeout value of timer T200.

l

Check the contents of the SABM frame.

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11

11 Mobile Originating Call Establishment

Mobile Originating Call Establishment

About This Chapter Mobile originating call refers to an MS calling another MS or a fixed phone. 11.1 Mobile Originating Call Establishment Procedure In terms of the assignment type, the mobile originating call establishment procedure is categorized into the early assignment procedure, late assignment procedure, and very early assignment procedure. The MSC determines the early assignment procedure and the late assignment procedure. The BSS determines the very early assignment procedure based on the radio resources. 11.2 Internal BSC Signaling Procedure of Mobile Originating Call Establishment This describes the internal BSC signaling procedure of mobile originating call establishment. 11.3 Abnormal Mobile Originating Call Establishment Cases This topic describes the abnormal mobile originating call establishment cases.

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11.1 Mobile Originating Call Establishment Procedure In terms of the assignment type, the mobile originating call establishment procedure is categorized into the early assignment procedure, late assignment procedure, and very early assignment procedure. The MSC determines the early assignment procedure and the late assignment procedure. The BSS determines the very early assignment procedure based on the radio resources. 11.1.1 Early Assignment Procedure This topic describes the early assignment procedure, namely the mobile originating call establishment without OACSU procedure. 11.1.2 Late Assignment Procedure This topic describes the late assignment procedure, namely the mobile originating call establishment with OACSU procedure. 11.1.3 Very Early Assignment Procedure This topic describes the very early assignment procedure, namely the Mobile Originating Call Establishment with OACSU procedure.

11.1.1 Early Assignment Procedure This topic describes the early assignment procedure, namely the mobile originating call establishment without OACSU procedure. Figure 11-1 shows the early assignment procedure.

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Figure 11-1 Early assignment procedure MS

BSC

BTS

MSC

Immediate Assignment Procedure Establish Indication (CM Service Request)(1)

CR(L3:CM Service Request)(2) CC(3)

CM Service Accepted(4) FACCH Setup(5) SDCCH Call Proceeding(6) SDCCH TCH Assignment Procedure Alerting(7) FACCH Connect(8) FACCH Connect Acknowledge(9) SDCCH Talking(10) Release Procedure

The early assignment procedure is as follows: 1.

The BTS sends the BSC an Establishment Indication message. The Establishment Indication message accurately indicates the reason for the access of an MS, for example, the cause values for mobile originating call establishment and for IMSI detach are different. The message also carries the content of the CM Service Request message.

2.

The BSC establishes an SCCP link connection on the A interface and sends the MSC a CM Service Request message.

3.

The MSC sends the BSC a Connect Confirm message.

4.

The MSC sends the MS a CM Service Accepted message on the SDCCH on the Um interface.

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5.

The calling MS sends a Setup message on the SDCCH. The Setup message carries all the information required on the network side for processing the call, including the number of the called MS.

6.

The MSC sends the calling MS a Call Proceeding message on the SDCCH on the Um interface. The Call Proceeding message indicates that a call is being processed and the mobile originating call processing procedure is initiated.

7.

The MSC sends the MS an Alerting message on the FACCH on the Um interface. Then the calling MS hears a ringing tone.

8.

The MSC sends the calling MS a Connect message on the FACCH on the Um interface. The Connect message is used to notify the MS that the connection is established.

9.

The calling MS responds to the MSC with a Connect Acknowledge message on the FACCH.

10. The calling and the called MSs enter the session state.

11.1.2 Late Assignment Procedure This topic describes the late assignment procedure, namely the mobile originating call establishment with OACSU procedure. Figure 11-2 shows the late assignment procedure.

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Figure 11-2 Late assignment procedure MS

BSC

BTS

MSC

Immediate Assignment Procedure Establish Indication (CM Service Request)(1)


CM Service Accepted(4) SDCCH Setup(5) SDCCH Call Proceeding(6) SDCCH Alerting(7) SDCCH TCH Assignment Procedure Connect(8) FACCH Connect Acknowledge(9) SDCCH Talking(10) Release Procedure

For details about the late assignment procedure, refer to 11.1.1 Early Assignment Procedure. 1.

The difference between the late assignment procedure and the early assignment procedure is that the assignment procedure of the former takes place after the Alerting message is sent.

2.

The late assignment saves the seizure time of speech channels.

3.

The disadvantage of the procedure shown in Figure 11-2 is that if the subsequent assignment is unsuccessful, the called MS can only hear the ring tone but cannot make calls. Therefore, in actual application, the early assignment procedure is used instead of the late assignment procedure.

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11.1.3 Very Early Assignment Procedure This topic describes the very early assignment procedure, namely the Mobile Originating Call Establishment with OACSU procedure. Figure 11-3 shows the very early assignment procedure. Figure 11-3 Very early assignment procedure MS

BTS

BSC

MSC

Immediate Assignment TCH Procedure Establish Indication (CM Service Request)(1)


CM Service Accepted(4) FACCH Setup(5) FACCH Call Proceeding(6) FACCH TCH Mode Modify Alerting(7) FACCH Connect(8) FACCH Connect Acknowledge(9) FACCH Talking(10) Release Procedure

For details about the very early assignment procedure, refer to 11.1.1 Early Assignment Procedure. 1.

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The difference between the very early assignment procedure and the 11.1.1 Early Assignment Procedure is that in the former, the TCH is assigned as a signaling channel during the immediate assignment procedure. Therefore, no TCH needs to be assigned during the assignment procedure, and the assigned TCH is adjusted to a speech channel through the Mode Modify message. Huawei Technologies Proprietary

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2.


During the immediate assignment procedure, if no idle SDCCHs but TCHs are available and TCH immediate assignment is allowed in the BSC data configuration, the very early assignment procedure will take place.

11.2 Internal BSC Signaling Procedure of Mobile Originating Call Establishment This describes the internal BSC signaling procedure of mobile originating call establishment. The internal BSC signaling procedure of mobile originating call establishment is as follows: 1.

On receiving the Channel Required message from the BTS, the BSC assigns a signaling channel according to the channel type and channel assignment algorithm in the Channel Required message. The TCH Immediate Assignment Allowed in the Cell Attributes window may be involved in the channel assignment.

2.

During random access, on receiving the Establish Indication message from the BTS, the BSC sends the MSC a CM Service Request message that carries the target CGI based on the MCC, MNC, LAC, and CI.

3.

On receiving the Assignment Request message from the MSC, the BSC checks the channel type. Choose Other Attributes > Advanced > Other Parameters. Check whether Data Service Allowed is supported.

4.

If the data service is not supported, an Assignment Failure message is returned. Based on the CIC in the Assignment Request message, the BSC checks the E1 timeslots on the A interface and confirms the existence of CIC. It also checks whether the circuit pool of the configured CIC, the channel type in the Assignment Request message, and the capacity of the GDPUC are collided. If they are collided, the BSC responds with an Assignment Failure message.

5.

On receiving the Assignment Complete message from the MS, the BSC fills the message with the A Interface Tag and sends the message to the MSC. You can choose BSC Property > Basic Data to display the A Interface Tag.

11.3 Abnormal Mobile Originating Call Establishment Cases This topic describes the abnormal mobile originating call establishment cases. 11.3.1 Calling MS Cannot Be Heard This topic describes the fault, probable causes, and handling suggestions. 11.3.2 MSC Releasing the Call after Sending a CM Service Reject Message This topic describes the fault, probable causes, and handling suggestions. 11.3.3 Abnormal Procedure Caused by MS in Busy State This topic describes the fault, probable causes, and handling suggestions. 11.3.4 MSC Sending a Disconnect Message Instead of an Assignment Request Message This topic describes the fault, probable causes, and handling suggestions. 11.3.5 Abnormal Procedures Caused by MS Hangup This topic describes the fault, probable causes, and handling suggestions. Issue 01 (2007-11-26)


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11.3.6 Abnormal Procedures Caused by MSC Sending a Clear Command Message or a Disconnect Message This topic describes the fault, probable causes, and handling suggestions. 11.3.7 LAPD Reporting an Error Indication Message During Call Establishment This topic describes the fault, probable causes, and handling suggestions.

11.3.1 Calling MS Cannot Be Heard This topic describes the fault, probable causes, and handling suggestions.

Fault When late assignment is enabled, the called MS cannot hear the calling MS.

Probable Causes TCH assignment fails.

Handling Suggestions Disable the late assignment.

11.3.2 MSC Releasing the Call after Sending a CM Service Reject Message This topic describes the fault, probable causes, and handling suggestions.

Fault After sending a CM Service Reject message, the MSC sends a Clear Command message to release the call.


The MSC cannot find the subscriber information and considers that the subscriber is illegal.

l

Authentication or encryption fails.

l

The MSC does not support the applied service in the CM Service Request message.

l

The MSC has no sufficient resources for the access, for example, no idle CICs.

Handling Suggestions The handling suggestions are as follows:

11-8

l

The MS makes a subscription under the MSC.

l

Check the subscriber information.

l

Hand over the MS to a cell under another MSC.

l

Wait for the MSC to release the resources, or expand the MSC transmission capability on the A interface. Huawei Technologies Proprietary

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11.3.3 Abnormal Procedure Caused by MS in Busy State This topic describes the fault, probable causes, and handling suggestions.

Fault After the assignment success of the calling MS, the network sends a Disconnect message with the cause value User Busy. The onhook by the calling MS or a Clear Command message sent by the MSC triggers the release of the BSC resources.

Probable Causes The MS is busy.

Handling Suggestions Wait for the onhook of the called MS and make a second call.

11.3.4 MSC Sending a Disconnect Message Instead of an Assignment Request Message This topic describes the fault, probable causes, and handling suggestions.

Fault The MSC does not send an Assignment Request message. It sends a Disconnect message to clear the call.

Probable Causes The A interface may be faulty.

Handling Suggestions Check the following: l

The state of the A interface circuit on the MSC side

l

The consistency of the A interface data on the MSC and the BSC, especially the circuit pool data

11.3.5 Abnormal Procedures Caused by MS Hangup This topic describes the fault, probable causes, and handling suggestions.

Fault The call establishment procedure is terminated.

Probable Causes l

The MS hangs up.

l

The calling or the called MS hangs up during a procedure, which causes abnormality in the subsequent procedures. For example, after the BSC receives an Assignment Request

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message from the MSC, the MS suddenly hangs up. In that case, the call establishment procedure may be terminated before the BSC responds to the MSC with an Assignment Complete message or an Assignment Failure message. As a result, the procedure is neither a successful assignment procedure (The BSC sends an Assignment Complete message.) nor an unsuccessful assignment procedure (The BSC sends an Assignment Failure message.).

Handling Suggestions No handling is required.

11.3.6 Abnormal Procedures Caused by MSC Sending a Clear Command Message or a Disconnect Message This topic describes the fault, probable causes, and handling suggestions.

Fault The MSC sends a Clear Command message or a Disconnect message.

Probable Causes Check the following: l

The cause value in the Clear Command message If a call terminates normally, the cause value in the Clear Command message is Call Control. Otherwise, the cause value may be Protocol Error or Equipment Failure.

l

The time difference between the previous message and the Clear Command message or the Disconnect message Check whether the abnormal procedure is triggered by timeout.


l

If the cause value in the Clear Command message is Call Control, no abnormality exists. If the cause value in the Clear Command message is Protocol Error, refer to the related protocols. If the cause value in the Clear Command message is Equipment Failure, check the related BSC hardware: –

Connection on the Ater interface

–

GEIUA in the GTCS

Check the timeout values of the related timers.

11.3.7 LAPD Reporting an Error Indication Message During Call Establishment This topic describes the fault, probable causes, and handling suggestions.

Fault The LAPD reports an Error Indication message during call establishment. 11-10


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Inconformity with protocols

l

LAPD link failure

l

Timer T200 expiry

l

MS failure in receiving a UA frame


Check the contents of the frames at the data link layer.

l

Check the status of the data link layer.

l

Check the timeout value of timer T200.

l

Check contents of the SABM frame.

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12

12 Mobile Terminating Call Establishment

Mobile Terminating Call Establishment

About This Chapter Mobile terminating call refers to an MS called by another MS or a fixed phone. 12.1 Mobile Terminating Call Establishment Procedure This topic describes the mobile terminating call establishment procedure. For details, refer to GSM Rec. 24008, 24080, 48008, 48018, and 48058. 12.2 Internal BSC Signaling Procedure of Mobile Terminating Call Establishment This describes the internal BSC signaling procedure of mobile terminating call establishment. 12.3 Abnormal Mobile Terminating Call Establishment Cases This topic describes the abnormal mobile terminating call establishment cases.

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12.1 Mobile Terminating Call Establishment Procedure This topic describes the mobile terminating call establishment procedure. For details, refer to GSM Rec. 24008, 24080, 48008, 48018, and 48058. Figure 12-1 shows the mobile terminating call establishment procedure. Figure 12-1 Mobile terminating call establishment procedure MS

BSC

BTS

MSC Paging(1)

Paging Command(2) Paging Request(3) PCH Channel Request(4) RACH Immediate Assignment Procedure Establish Indication (Paging Response)(5)

CR(CL31)(6) CC(7)

CM Service Accepted(8) SDCCH SDCCH

Setup(9) Call Confirmmed(10)

SDCCH TCH Assignment Procedure Alerting(11) FACCH

Connect(12) Connect Acknowledge(13)

FACCH FACCH

Talking(14) Release Procedure

The mobile terminating call establishment procedure is as follows: 1.

12-2

When the paged MS is in the service area of the MSC, the MSC sends the BSC a Paging message. The Paging message can also be sent to the BSC by the SGSN through the PCU on the Gb interface. It carries a list of paging cells (optional), TMSI, and IMSI.


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2.

The BSC sends the BTS a Paging Command message that carries the number of the occupied timeslot and the number of the paging sub-channel.

3.

Upon receiving the Paging Command message from the BSC, the BTS sends the paged MS a Paging Request message on the paging sub-channel. The Paging Request message carries the IMSI or TMSI of the paged MS.

4.

After decoding the Paging message, if the MS finds itself the paged MS, it sends the BTS a Channel Request message to trigger an Initial Channel Assignment procedure.

5.

For details about other messages, refer to 11.1 Mobile Originating Call Establishment Procedure.

12.2 Internal BSC Signaling Procedure of Mobile Terminating Call Establishment This describes the internal BSC signaling procedure of mobile terminating call establishment. The internal BSC signaling procedure of mobile terminating call establishment is as follows: 1.

On receiving the Paging message, the BSC forwards the message to the service module in the BM subrack that is configured with SS7. Based on the CGI in the Paging message, the service module checks the information of the paged cell. If the paged cell is in the BM subrack where the service module is located, the service module directly sends the Paging message to the cell. If the paged cell is in another BM subrack, the service module forwards the Paging message to the service module in that BM subrack.

2.

The service module in the BM subrack first checks whether the Allow eMLPP is set to Yes in Call Control of > Cell Attributes. Then the service module determines the paging packet based on the BS_AG_BLKS_RES, CCCH_CONF, and BS_PA_MFRAMES in Idle Mode of > Cell Attributes. After that, it sends the Paging message to the BTS.

12.3 Abnormal Mobile Terminating Call Establishment Cases This topic describes the abnormal mobile terminating call establishment cases. 12.3.1 No Paging Message on the A Interface This topic describes the fault, probable causes, and handling suggestions. 12.3.2 No Paging Message on the Abis Interface This describes the fault, probable causes, and handling suggestions. 12.3.3 No Paging Response on the Abis Interface This describes the fault, probable causes, and handling suggestions. 12.3.4 No Paging Response on the A Interface This topic describes the fault, probable causes, and handling suggestions.

12.3.1 No Paging Message on the A Interface This topic describes the fault, probable causes, and handling suggestions.

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Fault The MSC does not send a Paging message to the BSC, as indicated in the signaling tracing on the A interface.

Probable Causes The probable cause lies on the NSS side.

Handling Suggestions Check the data configuration and subscriber information in the MSC/VLR and the HLR. Power off the called MS and then power it on to make test calls. l

Check whether the subscriber data in the VLR is correct. When an MS is called, the MSC determines the current state of the MS based on the subscriber data in the VLR. The subscriber data includes the the active state, registered location area, and registered cells. Then the MSC determines whether and how to send a Paging message. If the state of the MS changes, for example, the MS is switched off or moves to another location area, but it has not registered in the network or the subscriber data in the VLR is not updated, the paging may fail. In this case, the MS needs to originate a location update procedure to ensure that the subscriber data in the VLR is correct. On the BSC side, the system information indicates the location update period of the MS. For details, refer to 6.1 Location Update Procedure. On the MSC side, there is also a location update period. The location update period on the BSC side is shorter than that on the MSC side. Therefore, the MS must originate a location update within the period specified by the MSC.

l

Check whether the parameters of location areas and cells on the MSC side are correct. Incorrect parameter configuration of location areas and cells on the MSC side may lead to unsuccessful transmission of the Paging message. For example, if the target BSC is incorrectly configured, the Paging message is sent to the wrong BSC.

12.3.2 No Paging Message on the Abis Interface This describes the fault, probable causes, and handling suggestions.

Description Upon receiving the Paging message from the MSC, the BSC does not send a Paging Command message to the BTS, as indicated in the message tracing on the Abis interface.

Analysis The probable cause lies on the BSC side.


Check whether the flow control procedure is triggered. –

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Check whether the PCH or AGCH is overloaded due to a sharp increase in short messages or a burst of access requests. Huawei Technologies Proprietary

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You can verify the change by comparing the values of the counters Immediate Assignment Requests and MSC Paging Requests (Circuit Service) before and after the problem occurs. –

l

Choose BSC Property > Flow Control Data. Check whether the flow control parameters are consistent with those described in the Version Matching Guide.

Check whether the data is correct. –

Check whether the CGI on the BSC side is consistent with that in the LAC carried in the Paging message. Check whether the configuration data of the cell is correct on the BSC6000 Local Maintenance Terminal. Incorrect parameter configuration of location areas and cells on the MSC side may lead to unsuccessful transmission of the Paging message. For example, if the target BSC is incorrectly configured, the Paging message is sent to the wrong BSC.

–

Check whether the paging-related parameters on the BSC side are configured correctly. Choose Cell Attributes > Idle Mode. Check whether the parameters BS_AG_BLKS_RES, CCCH_CONF, and BS_PA_MFRAMES are set correctly.

l

Check the communications between the subracks in the BSC. On receiving the Paging message from the MSC, the BSC starts paging based on the location area and cell information in the Paging message. Huawei BSC has multiple subracks. The Paging Command message sent from the BSC to the BTS may be forwarded between subracks. If the communication between the subracks is abnormal, the Paging Command message may not be forwarded, and no Paging Command message is sent on the Abis interface. You can view the BSC alarms to check the communication between the modules.

12.3.3 No Paging Response on the Abis Interface This describes the fault, probable causes, and handling suggestions.

Description After sending the BTS a Paging Command message, the BSC does not receive an Establishment Indication (Paging Response) message, as indicated in the message tracing on the Abis interface.

Analysis The probable causes are incorrect data configuration and poor radio coverage.


Check whether the PCH or AGCH is overloaded due to a sharp increase in short messages or a burst of access requests. You can verify the change by comparing the values of the counters Immediate Assignment Requests and MSC Paging Requests (Circuit Service) before and after the problem occurs.

l

Check whether the problem lies in the mobile equipment or in the SIM. Faulty mobile equipment or faulty SIM may lead to the problem. –

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Insert another SIM into the mobile equipment to check whether the problem lies in the SIM. Huawei Technologies Proprietary

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12 Mobile Terminating Call Establishment –

l

l


Insert the SIM into another mobile equipment to check whether the problem lies in the mobile equipment.

To check whether the problem lies in the BTS, make test calls in the following locations: –

Other cells under the same BTS

–

Other sites of the same site type

–

Other sites of a different site type

–

Sites from other manufacturers

Check whether the data is correct. –

Check whether the paging-related parameters on the BSC side are configured correctly. Choose Cell Attributes > Idle Mode. Check whether the parameters BS_AG_BLKS_RES, CCCH_CONF, BS_PA_MFRAMES, and TX-Integer (RACH Timeslot (Equals to a TDMA Rrame, 4.615 ms) are set correctly. Choose Cell Attributes > Call Control. Check whether the parameters such as the MS MAX Retrans are set correctly.

–

Check whether the values of the Location Update Period on the BSC and the MSC are set correctly. Choose Cell Attributes > Call Control. Check whether the parameters such as the Period of Periodic Location Update (6 minutes) are set correctly. The location update period on the BSC side is shorter than that on the MSC side. For details, refer to 6.1 Location Update Procedure.

l

Check the radio coverage. Poor radio coverage may lead to the existence of dead zones where an MS cannot receive the Paging Request message. Therefore, it cannot be paged. This case does not exist globally.

12.3.4 No Paging Response on the A Interface This topic describes the fault, probable causes, and handling suggestions.

Fault Upon receiving the Establishment Indication (Paging Response) message from the BTS, the BSC does not send any message to the MSC, as indicated in the message tracing on the Abis interface and the A interface.

Probable Causes The SS7 is faulty.

Handling Suggestions Troubleshoot the SS7 signaling intermittence.

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13 BSC Release

13

BSC Release

About This Chapter BSC release consists of the normal release and the local release. 13.1 Normal Release Procedure Normal release is originated by the MS or the MSC. Upon onhook, the calling MS sends a Disconnect message to the MSC. Then the corresponding MSC sends the Disconnect message to the called MS. 13.2 Local Release Procedure The local release procedure is initiated by the BSC.

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13 BSC Release

13.1 Normal Release Procedure Normal release is originated by the MS or the MSC. Upon onhook, the calling MS sends a Disconnect message to the MSC. Then the corresponding MSC sends the Disconnect message to the called MS.

Signaling Procedure After the access of the MS, the BSC initiates the release procedure upon service requests, for example, MS onhook. Figure 13-1 shows the BSC normal release procedure.

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13 BSC Release

Figure 13-1 Normal release procedure MS

BSC

BTS

MSC

Disconnect(1) FACCH Start T305 Release(2) FACCH

Start T308

Start T305 Release Complete(3) FACCH Stop T308 Clear Command(4) Channel Release(5) FACCH Stop T3109 Deactivate SACCH(8) DISC(6) FACCH

Release Indication(9)

UA(7)

Stop T3109

FACCH

Start T3111 Stop T3111

RF Channel Release(10) RF Channel Release Acknowledge(12)

Clear Complete(11)

RLSD(13) RLC(14)

The BSC normal release procedure is as follows: 1.

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Upon onhook, the calling MS sends a Disconnect message to the MSC and starts timer T305. The Disconnect message carries the cause for disconnection.


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13 BSC Release

2.

The MSC sends the calling MS a Release message and at the same time sends the called MS a Disconnect message. The network starts timer T308.

3.

Upon receiving the Release message, the calling MS stops timer T305, releases the MM connection, and sends the MSC a Release Complete message.

4.

Upon receiving the Release Complete message, the MSC stops timer T308, releases the MM connection, and sends the BSC a Clear Command message. The Clear Command message notifies the BSC of releasing the resources on the A interface and the Um interface.

5.

The BSC sends a Channel Release message and starts timer T3109. The Channel Release message carries the RR cause filed and notifies the MS and the BTS of releasing the logic channels on the Um interface.

6.

Upon receiving the Channel Release message, the MS disconnects the uplink signaling link and sends the BTS a DISC frame, indicating that the logic channels are released.

7.

The BTS sends the MS a UA frame. Upon receiving the UA frame, the MS returns to the CCCH and enters the idle state.

8.

The BSC sends the BTS a Deactivate SACCH message, deactivates the associated channels, and releases the downlink channel associated signaling.

9.

Upon receiving the DISC frame, the BTS sends the BSC a Release Indication message, stops timer T3109, and starts timer T3111. The Release Indication message indicates that the MS has released the logic channels on the Um interface.

10. Upon timer T3111 expiry, the BSC sends the BTS an RF Channel Release message. Timer T3111 is used to reserve a period for the acknowledgement of disrupted connection. 11. The BTS sends the BSC an RF Channel Release Acknowledge message, indicating that the RF channels on the radio interface are released and can be used for re-assignment. 12. The BSC responds to the MSC with a Clear Complete message. 13. The MSC sends the BSC an RLSD message to release the SCCP connection. 14. The BSC responds to the MSC with an RLC message, indicating that the SCCP connection is released.

Procedure Description l

Steps 1 through 3 shown in Figure 13-1 is the call connection release. NOTE

Figure 13-1 shows the MS originating release procedure. For the network originating release procedure, the directions of only the three transparent transmission messages are opposite. l

Steps 4 through 14 shown in Figure 13-1 is the radio resource release. After the connections at the CC layer and at the MM layer are released, the network sends the BSC a Clear Command message to request the release of the SCCP signaling link. The Clear Command message carries the clear causes such as the Handover Successful or Call Control. If the release is caused by radio interface message failures, radio link failures, or equipment failures, the BSC sends a Clear Request message to the system. Then, the MSC delivers the Clear Command message.

13.2 Local Release Procedure The local release procedure is initiated by the BSC. Figure 13-2 shows the local release procedure. 13-4


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13 BSC Release

Figure 13-2 Local release procedure BTS

BSC Deactivate SACCH (1) Release Request (2) Release Confirm (3) RF Channel Release(4) RF Channel Release Acknowledge (5)

l

The BSC sends the BTS a Deactivate SACCH message to deactivate the associated channels.

l

The BSC sends the BTS a Release Request message with the cause value Local End Release. In this case, the release procedure has nothing to do with the MS.

l

Upon receiving the Release Request message with the cause value Local End Release, the BTS responds to the BSC with a Release Confirm message. If the Release Request message carries other cause values, the BTS sends a DISC frame to the MS. Only after receiving the UA frame or DM frame from the MS, the BTS sends the Release Confirm message to the BSC.

l

The BSC sends an RF Channel Release message to the BTS.

l

The BTS sends an RF Channel Release Acknowledge message to the BSC.

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14 Handover

14

Handover

About This Chapter Handover is one of the basic functions of the GSM. It enables calls to be set up in better cells and reduces call drops. Handover also lowers cross interference. The handover procedure consists of handover triggering, handover preparation, handover decision, and handover execution. 14.1 Handover Procedure The handover procedure is categorized into the intra-BSC handover procedure, inter-BSC handover procedure, inter-MSC handover procedure, and inter-system handover procedure. 14.2 Internal BSC Signaling Procedure of Handover The internal BSC signaling procedure of handover is categorized by intra-BSC handover, interBSC handover, inter-MSC handover, and inter-system handover. 14.3 Abnormal Handover Cases This topic describes the abnormal handover cases.

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14 Handover

14.1 Handover Procedure The handover procedure is categorized into the intra-BSC handover procedure, inter-BSC handover procedure, inter-MSC handover procedure, and inter-system handover procedure. 14.1.1 Intra-BSC Handover Procedure This topic describes the intra-BSC handover procedure. 14.1.2 Inter-BSC Handover Procedure This topic describes the inter-BSC handover procedure. 14.1.3 Inter-MSC Handover Procedure This topic describes the inter-MSC handover procedure. 14.1.4 Inter-System Handover Procedure This topic describes the inter-system handover procedure.

14.1.1 Intra-BSC Handover Procedure This topic describes the intra-BSC handover procedure. Figure 14-1 shows the intra-BSC handover procedure.

14-2


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Figure 14-1 Intra-BSC handover procedure MS

BTS2

BSC

Channel Activation(3) Handover Access(6) FACCH

BTS1

Measurement Result(2)

Channel Activation Acknowledge(4) Start T3103

MS

MSC

Measurement Report(1) SACCH Handover Command(5) FACCH

Start T3124 Handover Access FACCH

Handover Detect(7)

PHY INFO(8) FACCH Stop T3124 SABM(9) FACCH

Establish Indication(10)

UA(11) FACCH

Handover Complete(12)

FACCH Stop T3103 Handover Perfomed(13)

1.

The MS sends BTS1 a measurement report on an SACCH on the Um interface.

2.

BTS 1 forwards the measurement report to the BSC.

3.

Based on the measurement report, the BSC determines whether to hand over the MS to another cell. If a handover is required, the BSC sends BTS 2 a Channel Activation message.

4.

Upon receiving the Channel Activation message, if the channel type is correct, BTS 2 turns on the power amplifier on the specified channel to receive information on the uplink, and sends a Channel Activation Acknowledge message to the BSC.

5.

Upon receiving the Channel Activation Acknowledge message, the BSC sends BTS 1 a Handover Command message. Then BTS 1 forwards the command to the MS. The message is sent on an FACCH on the Um interface. BTS 1 starts timer T3103. The Handover Command message has all the information to be transferred on the new channel and the data required for accessing the MS. It also indicates whether the handover is synchronous or asynchronous.

6.

Upon receiving the Handover Command message, the MS attempts the access and sends BTS 2 a Handover Access message on the FACCH.

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14 Handover

7.

Upon receiving the Handover Access message, BTS 2 sends the BSC a Handover Detect message.

8.

Whether a PHY INFO message is sent or not depends on the handover type. l

Asynchronous handover After the channels of BTS 2 are activated, BTS 2 waits for the access of the MS on a dedicated channel until timer T3103 expires. Upon detecting the Handover Access message from the MS, BTS 2 sends the BSC a Handover Detect message and at the same time to the MS a PHY INFO message on an FACCH. The PHY INFO message carries the new TA calculated by BTS 2. Upon receiving the PHY INFO message, the MS sends BTS 2 an SABM frame.

l

Synchronous handover BTS2 does not send the PHY INFO message. Upon sending the Handover Access message, the MS sends BTS 2 the SABM frame.

9.

When the PHY INFO message is sent depends on the handover type. l

Asynchronous handover The MS starts timer T3124 upon sending the Handover Access message for the first time. It stops timer T3124 upon receiving the PHY INFO message, and sends BTS 2 an SABM frame on an FACCH.

l

Synchronous handover Upon sending the Handover Access message, the MS sends BTS 2 an SABM frame.

10. Upon receiving the first SABM frame, BTS 2 sends an Establishment Indication message to notify the BSC of radio link establishment. 11. At the same time, BTS2 sends a UA frame on an FACCH to notify the MS of radio link establishment. 12. The MS sends BTS 2 a Handover Complete message on the FACCH. BTS 2 forwards the message to notify the BSC of the handover success. The Handover Complete message carries only the handover complete indication. The MS does not return to the old channel after sending this message. If the MS does not receive the PHY INFO message or the UA frame from the target cell, it sends a Handover Failure message on the old channel. 13. Upon receiving the Handover Complete message, the BSC stops timer T3103 and sends a Handover Performed message to notify the MSC of the handover completion. The Handover Performed message carries the handover type. At the same time, the BSC sends an RF Channel Release message to notify BTS 1 of channel release. The target cell forwards to the BSC the Handover Complete message it receives from the MS. Upon receiving the Handover Complete message, the BSC sends an RF Channel Release message to notify BTS 1 of channel release. Upon receiving the RF Channel Release message, BTS 1 sends an RF Channel Release Acknowledge message. The message indicates that the radio channel is released and ready for reallocation.

14.1.2 Inter-BSC Handover Procedure This topic describes the inter-BSC handover procedure. Figure 14-2 shows the inter-BSC handover procedure.

14-4


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14 Handover

Figure 14-2 Inter-BSC handover procedure MS

BTS1

BSC1

Measurement Report from MS(1)

MSC

Handover Required(2)

SACCH

Start T7 Handover Command(7)

BSC2

Handover Request(3) Handover Request Acknowledge(6)

BTS2

MS

Channel Activation(4) Channel Activation Acknowledge(5)

Stop T7 Handover Command(9) FACCH

Handover Command(8)

Handover Access(9)

Start T8

Start T3124

Handover Detect(12)

Handover Access(10)

Handover Detect(11)

FACCH PHY INFO(13) FACCH Stop T3124


SABM(14) FACCH UA(16) FACCH

Clear Command(20)



Handover Complete(17) FACCH

Stop T8 Clear Complete(21)

The inter-BSC handover procedure involves more A-interface signaling procedures than the intra-BSC handover procedure. These signaling procedures are described subsequently. For details about other signaling messages, refer to 14.1.2 Inter-BSC Handover Procedure. 1.

When an MS needs to be handed over to a cell controlled by BSC 2, BSC 1 sends the MSC a Handover Required message and starts timer T7. This message carries the CELL IDs of the target cell group and the serving cell, and the handover cause.

2.

Upon receiving the Handover Required message, if the MSC finds that the location area of the target cell is under itself, it sends BSC 2 a Handover Request message. The Handover Request message carries the information, transmission mode, MS classmark, and required channel classmark of the serving and the target cells. Upon receiving the Handover Request message, BSC 2 sends the MSC an SCCP Connection Confirm message, indicating that its

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14 Handover

connection to the MSC is established. The A interface messages are sent through this SCCP connection. 3.

BSC 2 activates a new channel and sends a Handover Request Acknowledge message to notify the MSC that the channel is now available. The Handover Request Acknowledge message carries the information of the allocated handover resources and the handover command indicating that the BSC is ready.

4.

Upon receiving the Handover Request Acknowledge message, the MSC sends BSC 1 a Handover Command message. Then BSC 1 stops timer T7. BSC 1 sends the MS a Handover Command message and starts timer T8, requesting the MS to access the new channel. The Handover Command message carries the cell ID, channel type, and handover reference.

5.

Upon receiving the Handover Complete message from BSC 2, the MSC sends BSC 1 a Clear Command message. The Clear Command message carries the clearance causes. BSC 1 stops timer T8, initiates a channel release procedure, and sends the MSC a Clear Complete message. NOTE

If the serving cell and the target cell are in different location areas, the MS initiates a location update procedure after a call is complete.

14.1.3 Inter-MSC Handover Procedure This topic describes the inter-MSC handover procedure. Figure 14-3 shows the inter-MSC handover procedure.

14-6


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Figure 14-3 Inter-MSC handover procedure MS

BTS1

BSC1

Measurement Report from MS(1) SACCH

MSC1

Handover Required(2)

MSC2

Perform Handover(3)

Radio Channel Ack(8)

BSC2

Handover Request(4)

Handover Request Acknowledge(7)

BTS2

MS

Channel Activation(5) Channel Activation Acknowledge(6)

IAM(9) Handover Command(11)

Handover Command(12)

ACM(10)

FACCH Handover Detect(15)

Handover Detect(14)

Handover Access(13) FACCH PHY INFO(16) FACCH PHY INFO(17) FACCH


SABM(18) FACCH UA(20) FACCH

Clear Command(25)

Send End Signal(24)



Handover Complete(21) FACCH

Clear Complete(26)

For the inter-MSC handover procedure, refer to 14.1.1 Intra-BSC Handover Procedure and 14.1.2 Inter-BSC Handover Procedure. The messages on the E interface are as follows: 1.

Perform Handover: MAP layer message. It contains the CGI of the serving cell and the target cell and the required channel type. It informs MSC2 that a handover will be initiated.

2.

Radio Channel Acknowledge: MAP layer message. It carries the information of the new channel in the target cell and the handover number.

3.

IAM: initial address message. It is a TUP/ISUP message.

4.

ACM: address complete message. It is a TUP/ISUP message.

5.

Send End Signal: MAP layer message.

14.1.4 Inter-System Handover Procedure This topic describes the inter-system handover procedure. Issue 01 (2007-11-26)


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Figure 14-4 shows the inter-system handover procedure. Figure 14-4 GSM-to-UMTS handover procedure MS

BSS

MSC

RNC

MS

Handover Required(1) Inter System to UTRAN Handover Command(2)

Handover Command(3) FACCH

Handover to UTRAN Complete(4)

Start T3121 Handover Complete(5)

FACCH

Stop T3121 Clear Command(6) Clear Complete(7)

Figure 14-5 UMTS-to-GSM handover procedure BSS

MS

MSC

RNC

MS

Handover Request(1) Handover Request Acknowledge(2) Handover Access(5) FACCH Handover Access(7) FACCH

Handover Request Acbowledge(3)

FACCH

Handover Detect(6) Handover Complete(8)

Handover Command(4)


The GSM-to-UMTS handover procedure is as follows:

14-8

1.

The BSS sends a Handover Required message to the MSC.

2.

Upon receiving the Handover Required message, the MSC sends the BSS an Inter System To UTRAN Handover Command message and starts timer T3121.

3.

Upon receiving the Inter System To UTRAN Handover Command message, the BSS sends the MS a Handover Command message on an FACCH.

4.

After the connection is successfully established, the MS sends the RNC a Handover to UTRAN Complete message on a UTRAN channel. Huawei Technologies Proprietary

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5.

The RNC forwards the Handover Complete message to the MSC.

6.

Upon receiving the Handover Complete message, the MSC stops timer T3121 and initiates a channel release procedure. NOTE

For the UMTS-to-GSM handover procedure, refer to the GSM-to-UMTS handover procedure mentioned earlier.

14.2 Internal BSC Signaling Procedure of Handover The internal BSC signaling procedure of handover is categorized by intra-BSC handover, interBSC handover, inter-MSC handover, and inter-system handover. 14.2.1 Internal BSC Signaling Procedure of the Intra-BSC Handover This topic describes the internal BSC signaling procedure of the intra-BSC handover. 14.2.2 Internal BSC Signaling Procedure of the Inter-BSC Handover This topic describes the internal BSC signaling procedure of the inter-BSC handover. 14.2.3 Internal BSC Signaling Procedure of the Inter-MSC Handover This topic describes the internal BSC signaling procedure of the inter-MSC handover. 14.2.4 Internal BSC Signaling Procedure of the Inter-System Handover This describes the internal BSC signaling procedure of the inter-system handover.

14.2.1 Internal BSC Signaling Procedure of the Intra-BSC Handover This topic describes the internal BSC signaling procedure of the intra-BSC handover. 1.

If the BSC considers that the call meets the handover conditions, it selects a candidate cell from the candidate cell list based on the priority in a descending order. If the candidate cell is internal BSC, the BSC notifies the candidate cell of initiating an intra-BSC handover procedure, and the candidate cell will be the target cell.

2.

The target cell allocates a channel and notifies BTS 2 of channel activation.

3.

After BTS 2 activates the channel, BTS 1 sends the MS a Handover Command message. Then BSC 2 starts timer T3103 to wait for the Handover Detect message.

4.

After receiving the Handover Detect message, BTS 2 continues to wait for the Establishment Indication message and the Handover Complete message.

5.

After BTS 2 receives the Handover Complete message, BSC 2 stops timer T3103 and considers that the call is set up in the target cell.

6.

BSC 1 notifies BTS 1 of initiating a local release procedure. At the same time, it sends a Handover Performed message to notify the MSC of the handover completion.

14.2.2 Internal BSC Signaling Procedure of the Inter-BSC Handover This topic describes the internal BSC signaling procedure of the inter-BSC handover. 1.

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If the BSC considers that the call meets the handover conditions, it selects a candidate cell from the candidate cell list based on the priority in a descending order. If the candidate cell is an external cell, the inter-BSC handover procedure is directly triggered. For the serving cell, the external cell is the target cell, and the BSC where the target cell is located is the target BSC, namely BSC 2. Huawei Technologies Proprietary

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14 Handover

2.

Upon handover initiation, BTS 1 sends the MSC a Handover Required message and starts timer T17 to wait for a Handover Command message.

3.

Upon receiving the Handover Ruest message from the MSC, BSC 2 allocates and activates channels according to the target cell ID in the message. After channel activation, BTS 2 sends the MSC a Handover Request Acknowledge message that carries the Handover Command message.

4.

BTS 1 forwards to the MS the Handover Command message that BSC 1 receives and at the same time starts timer T8 to wait for the handover completion. If the Clear Command message with the cause value Handover Success is received before T8 expires, BSC 1 considers that the handover is successful. If the MS returns to the old channel before timer T8 expiry, BSC 1 stops timer T8 and sends the MSC a Handover Failure message. If timer T8 expires, BSC 1 considers that the call drops and sends the MSC a Clear Request message.

5.

BTS 2 forwards the Handover Detect message to the MSC and continues to wait for the Establishment Indication message and the Handover Complete message.

6.

Upon receiving the Handover Complete message, BTS 2 sends a Handover Complete message to notify the MSC of handover completion.

7.

Upon receiving the Clear Command message, BTS 1 releases the radio resources the call occupies and returns the MSC a Clear Complete message.

14.2.3 Internal BSC Signaling Procedure of the Inter-MSC Handover This topic describes the internal BSC signaling procedure of the inter-MSC handover. The internal BSC signaling procedure of the inter-MSC handover is the same as that described in 14.2.2 Internal BSC Signaling Procedure of the Inter-BSC Handover.

14.2.4 Internal BSC Signaling Procedure of the Inter-System Handover This describes the internal BSC signaling procedure of the inter-system handover. Compared with the internal system handover, the BSC in the inter-system handover procedure performs more actions as described subsequently: l

Obtaining the UTRAN neighbor cell information and the UTRAN system parameters from the Idle Mode, Handover Data, and Other Attributes in the Cell Attributes window.

l

Recording the capability of the MS

The internal BSC signaling procedure of the inter-system handover is the same as that described in 14.2.2 Internal BSC Signaling Procedure of the Inter-BSC Handover.

14.3 Abnormal Handover Cases This topic describes the abnormal handover cases. 14.3.1 No Available Channels in the Target Cell This describes the fault, probable causes, and handling suggestions. 14.3.2 Old BSS Not Receiving a Specified Message upon T8 Expiry This describes the fault, probable causes, and handling suggestions. 14-10


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14.3.3 Inter-Cell Handover Failure (MS Returning to the Old Channel) This topic describes the fault, probable causes, and handling suggestions. 14.3.4 BSC Receiving a Connection Failure Indication Message This topic describes the fault, probable causes, and handling suggestions. 14.3.5 Forced Handover Failure This topic describes the fault, probable causes, and handling suggestions. 14.3.6 Handover Failure Caused by CIC Malfunction This topic describes the fault, probable causes, and handling suggestions. 14.3.7 Handover Failure Caused by MS Access Failure This topic describes the fault, probable causes, and handling suggestions.

14.3.1 No Available Channels in the Target Cell This describes the fault, probable causes, and handling suggestions.

Description No channels are available in the target cell.

Analysis The probable causes are as follows: l

During an inter-cell handover, no TCHs are available in the target cell.

l

During a cross-cell handover, no SDCCHs are available in the target cell.

l

During an intra-cell handover due to bad quality, no TCHs are available in the cell.


Check whether the target cell is congested. If yes, add TRXs to the target cell.

l

On the Cell Attributes tab page, click Channel Management. In the displayed dialog box, click Advanced. On the Huawei Channel Allocation Algorithm II and Radio Channel Management and Control tab page, check whether TCH Traffic Busy Threshold (%) is set properly.

l

On the Cell Attributes tab page, click Channel Management. In the displayed dialog box, check whether Enhanced TCH Adjust Allowed is set properly.

14.3.2 Old BSS Not Receiving a Specified Message upon T8 Expiry This describes the fault, probable causes, and handling suggestions.

Description The old BSS does not receive a Clear Command message from the MSC or a Handover Failure message from the MS upon T8 expiry. Issue 01 (2007-11-26)


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14 Handover

Analysis If the old BSS does not receive a Clear Command message from the MSC or a Handover Failure message from the MS upon T8 expiry, it will release the dedicated channels and send the MSC a Clear Request message with the cause value Radio Interface Message Failure. Before a Clear Command message is received, the terrestrial resources on the old BSS side remain allocated. On receiving the Clear Command message, the old BSS changes the state of the terrestrial resources to idle and sends a Clear Complete message to the MSC. Then the MSC releases the SCCP connection to the old BSS and thus terminates the connection with the BSS.

Handling Suggestions On the Cell Attributes tab page, click Other Attributes. Then click Advanced. On the Cell Timer tab page, check whether T8 is set properly.

14.3.3 Inter-Cell Handover Failure (MS Returning to the Old Channel) This topic describes the fault, probable causes, and handling suggestions.

Fault The MS returns to the old channel after inter-cell handover failure.

Probable Causes The probable causes are that the MS cannot access the old channel due to bad transmission quality on the Um interface, low level, or incorrect data configuration of the external cells.

Handling Suggestions Check the transmission quality on the Um interface.

14.3.4 BSC Receiving a Connection Failure Indication Message This topic describes the fault, probable causes, and handling suggestions.

Fault Calls drop.


Radio link failure

l

Hardware faults

Handling Suggestions

14-12

l

Check the resources on the Um interface.

l

Check the antenna system and the power amplifier. Huawei Technologies Proprietary

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14.3.5 Forced Handover Failure This topic describes the fault, probable causes, and handling suggestions.

Fault Forced handover fails.

Probable Causes l

No neighbor cell

l

Incorrect configuration of the neighbor cell

l

No resources in the neighbor cell

l

Bad radio conditions in the neighbor cell

Handling Suggestions Check the data configuration and the radio conditions of the neighbor cell, for example, the level.

14.3.6 Handover Failure Caused by CIC Malfunction This topic describes the fault, probable causes, and handling suggestions.

Fault Handover fails. The cause value of the Handover Failure message is Requested Terrestrial Resource Unavailable.

Probable Causes If the CIC allocated in the Handover Request message received by the target BSC is marked as BLOCK, the target BSC will respond to the MSC with a Handover Failure message with the cause value Requested Terrestrial Resource Unavailable.

Handling Suggestions Check the state of the CIC.

14.3.7 Handover Failure Caused by MS Access Failure This topic describes the fault, probable causes, and handling suggestions.

Fault The MS cannot be handed over.

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Handling Suggestions

14-14

l

Check whether the handover trigger conditions are met.

l

Check whether there is a neighbor cell list in the measurement report.

l

Check whether the neighbor cell has available channels.

l

Check whether the data of the neighbor cell is incorrect, for example, whether there is inconsistency in CGI.


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15 Call Re-Establishment

15

Call Re-Establishment

About This Chapter The call re-establishment procedure allows an MS to resume a connection after a radio link failure. It may take place in a new cell or a new location area. 15.1 Call Re-Establishment Procedure This describes the call re-establishment procedure. 15.2 Internal BSC Signaling Procedure of Call Re-Establishment The call re-establishment is controlled by the MSC, and the BSC does no special processing. 15.3 Abnormal Call Re-Establishment Cases This topic describes the abnormal call re-establishment cases.

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15.1 Call Re-Establishment Procedure This describes the call re-establishment procedure.

Signaling Procedure Figure 15-1 shows the call re-establishment procedure. Figure 15-1 Call re-establishment procedure BSS

MS

MSC

Connection Failure Indication(radio link failure)(1) Channel Request(5) RACH RACH

RNC

Clear Request(2)

Clear Command(3) Establish Indication(CM Reestablishment Request)(6) CM Re-establishment Request(7) CM Service Accepted (9)

CC(8) Cipher Mode Command(10)

Start T3230

Cipher Mode Complete(11) Assignment Request(12)

Status Enquiry(14) FACCH

Assignment Complete(13) Start T322

Status(15) FACCH

Stop T322

Stop T3230

15-2

1.

After a radio link failure is detected, the BTS sends the BSC a Connection Failure Indication message, which contains the cause value for radio link failure.

2.

The BSC sends the MSC a Clear Request message, which contains the cause for the abnormal release.

3.

On receiving the Clear Request message, the MSC sends the BSC a Clear Command message, requesting the release of radio resources.

4.

The BSC initiates a release procedure, releases the channel resources on the Um interface, and returns a Clear Complete message to the MSC. Huawei Technologies Proprietary

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5.

The MS sends the BTS a Channel Request message and initiates an immediate assignment procedure.

6.

The BTS initiates a call re-establishment procedure by sending the BSC a CM Reestablishment Request message. In addition, the MM entity of the MS starts timer T3230, gives an indication to all CM entities that are being re-established, and remains in the MM sublayer state Wait For Reestablish. The CM Re-Establishment Request message contains the IMSI (or TMSI), classmark 2, and Ciphering Key Sequence Number (CKSN).

7.

The BSC establishes an SCCP link connection on the A interface and sends the MSC a CM Service Request message.

8.

The MSC sends the BSC a Connect Confirm message.

9.

The MSC sends the MS a CM Service Accepted message on the SDCCH on the Um interface.

10. The MSC initiates the ciphering mode setting procedure by sending a Cipher Mode Command message. For details, refer to the ciphering procedure. Once the ciphering procedure is complete or the CM Service Accept message is received, the MS stops timer T3230 and enters the MM sublayer state MM Connection Active. 11. The BSC returns a Cipher Mode Complete message to the MSC. 12. The MSC sends the BSC an Assignment Request message and initiates a signaling processing procedure. For details about the signaling procedure, refer to the mobile originating call establishment procedure. 13. The BSC returns an Assignment Complete message to the MSC. 14. The MSC initiates the status enquiry procedure by sending the MS a Status Enquiry message. At the same time, timer T322 is started. 15. The MS reports its call state or attach state to the MSC. The MSC stops timer T322 accordingly.

Procedure Description For details of the call re-establishment procedure, refer to the following: 1.

Steps 1 through 4 shown in Figure 15-1 is radio resource release procedure, which is the same as the normal release procedure.

2.

Steps 5 through 9 shown in Figure 15-1 is the immediate assignment procedure, namely, the signaling channel seizure procedure.

3.

Steps 10 and 11 shown in Figure 15-1 is the ciphering procedure.

4.

Steps 12 and 13 shown in Figure 15-1 is the assignment procedure.

5.

Initiation of the call re-establishment procedure If a cell is required to support call re-establishment, Call Re-Establishment in Cell Attributes must be selected, and the cell cannot be in barred state. Upon detection of a link failure, the MS sends a Channel Request message with the cause value Call Re-Establishment in the selected cell. The previous channel resources are released by the BSC after the timer on the BTS side expires. Upon detection of a link failure, the BTS sends the BSC a Connection Failure message with the cause value Radio Link Failure. Then the BSC releases the corresponding radio resources and waits for the call re-establishment request from the MS.

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Mode of the MS in the call re-establishment procedure Huawei Technologies Proprietary

15-3



The MS cannot return to idle mode during a call re-establishment procedure. Therefore, if the cell selected for call re-establishment is not the location area, the MS cannot perform location update until the call re-establishment procedure is complete.

15.2 Internal BSC Signaling Procedure of Call ReEstablishment The call re-establishment is controlled by the MSC, and the BSC does no special processing.

15.3 Abnormal Call Re-Establishment Cases This topic describes the abnormal call re-establishment cases. 15.3.1 Network Sending a CM Service Reject Message This topic describes the fault, probable causes, and handling suggestions. 15.3.2 Call Re-Establishment Not Allowed or Re-Establishment Failure This describes the fault, probable causes, and handling suggestions. 15.3.3 RR Connection Failure This topic describes the fault, probable causes, and handling suggestions.

15.3.1 Network Sending a CM Service Reject Message This topic describes the fault, probable causes, and handling suggestions.

Fault After the MSC receives a CM Re-Establishment Request message, if the RR sublayer sends an indication that the ciphering mode setting procedure is complete, or if a CM Service Accept message is received, you can infer that the MS accepts the services. The MS re-enters the MM sublayer state MM Connection Active. If the re-establishment request from the MS does not correspond to its current call state, the network returns the MS a CM Service Reject message.


IMSI Unknown in VLR

l

Illegal MS

l

Network Failure

l

Congestion

l

Service Option not Supported

l

Service Option Temporarily out of Order

Irrespective of the reject cause, upon receiving a CM Service Reject message, the MS releases the MM connection and the relevant RR connection. 15-4


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Check whether the location update procedure is performed successfully to ensure that the IMSI is loaded to the VLR. In addition, check whether the IMSI exists in the HLR.

l

Check whether the MS can access the network and can perform location update. If not, replace the MS with a new one that can access the network.

l

Modify the configuration that corresponds to call re-establishment on the network side.

l

Configure more channels.

l

Modify the configuration that corresponds to call re-establishment on the network side.

l

Modify the configuration that corresponds to call re-establishment on the network side, for example, the CM service related functions.

l

If the early-mentioned measures do not work, analyze the values of the corresponding information elements to find out in which network element the fault takes place. Then perform detailed analysis in the located network element.

15.3.2 Call Re-Establishment Not Allowed or Re-Establishment Failure This describes the fault, probable causes, and handling suggestions.

Description When an MM connection is established, the MM layer sends an indication to the CC layer. If the MM layer is disconnected, the connection may be re-established through a CC request.

Analysis The probable causes are as follows: l

If re-establishment is not allowed, and the call is initiated within the establishment or clearing period, the CC layer releases the MM connection.

l

If re-establishment is unsuccessful, the MM connection is released, and a release indication is sent to the CC layer.

Handling Suggestions Check whether the Call Reestablishment Forbidden parameter of the cell where the reestablishment procedure is initiated is set properly and whether the cell is barred.

15.3.3 RR Connection Failure This topic describes the fault, probable causes, and handling suggestions.

Fault Upon detection of a random access failure or an RR connection failure, the MS stops timer T3230, aborts the call re-establishment procedure, and releases all active MM connections. Upon detection of an RR connection failure, the MSC aborts the call re-establishment procedure and releases all active MM connections. Issue 01 (2007-11-26)


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Probable Causes The probable causes can be found out through signaling tracing.

Handling Suggestions The handling suggestions are as follows:

15-6

l

If the transmission quality on the Um interface is poor, use a test MS to measure the signaling quality on the uplink and downlink and the power level. Improve the transmit and receive quality and reduce the interference.

l

If the channels are congested, register and observe the relevant traffic statistics to determine the severity congestion. Exapnd the system capacity if the congestion rate is high.

l

If the problem lies in the network, make adjustments on the network side to locate the phases in which response delay happens.


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16 Directed Retry

16

Directed Retry

About This Chapter Directed retry is a special type of handover. It refers to the process of assigning an MS to a TCH in a cell other than the serving cell when no radio resources are available. It is triggered by the assignment procedure and employs internal or external handover procedures. 16.1 Directed Retry Procedure The directed retry procedure is categorized into the intra-BSC directed retry procedure, interBSC directed retry procedure, and inter-MSC directed retry procedure. 16.2 Internal BSC Signaling Procedure of Directed Retry The internal BSC signaling procedure of directed retry is categorized by intra-BSC directed retry, inter-BSC directed retry, and inter-MSC directed retry. 16.3 Abnormal Directed Retry Cases This topic describes the abnormal directed retry cases.

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16 Directed Retry

16.1 Directed Retry Procedure The directed retry procedure is categorized into the intra-BSC directed retry procedure, interBSC directed retry procedure, and inter-MSC directed retry procedure. 16.1.1 Intra-BSC Directed Retry Procedure This topic describes the intra-BSC directed retry procedure. 16.1.2 Inter-BSC directed retry procedure This topic describes the inter-BSC directed retry procedure. 16.1.3 Inter-MSC directed retry procedure This topic describes the inter-MSC directed retry procedure.

16.1.1 Intra-BSC Directed Retry Procedure This topic describes the intra-BSC directed retry procedure. Figure 16-1 shows the intra-BSC directed retry procedure.

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Figure 16-1 Intra-BSC directed retry procedure MS

BTS1 Channel Request(1)

RACH

BSC

MSC

BTS2

MS

Channel Required(2) Channel Activation(3)

Immediate Channel Activation Assignment Acknowledge(4) Command(5) AGCH SABM(6) Establish Indication (CM Service CR(Complete SDCCH Request)(8) L3 Information)(9)

UA(7)

CM Service Accepted(11) Setup(12) SDCCH SDCCH

CC(10)

Call Proceeding(13) Assignment Request(14) Channel Activation Acknowledge(16)

Handover Command(17)

Start T3103

Handover Access(18)

Handover Detect(19)

SDCCH

FACCH PHY INFO(20) FACCH


PHY INFO(21) FACCH SABM(22) FACCH


UA(24) FACCH

Stop T3103 Assignment Complete(26)

1.

The MS sends the BTS a Channel Request message on the RACH.

2.

The BTS sends the BSC a Channel Required message.

3.

Upon receiving the Channel Required message, the BSC assigns a signaling channel and sends the BTS a Channel Activation message.

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16 Directed Retry

4.

Upon receiving the Channel Activation message, if the channel type is correct, the BTS enables the power amplifier on the AGCH, starts receiving the uplink information, and sends the BSC a Channel Activation Acknowledge message.

5.

Upon receiving the Channel Activation Acknowledge message, the BSC sends an Immediate Assignment Command message on the AGCH to notify the MS of channel access.

6.

After the MS successfully accesses the channel, the MSC sends the BSC an Assignment Request message requesting for TCH radio resources. The Assignment Request message carries the information on the circuits between the MSC and the BSC. If no TCH is available in the serving cell, the BSC attempts to hand over the MS to a neighbor cell that provides voice services. If the target cell and the serving cell are controlled by the same BSC, the directed retry is an intra-BSC directed retry.

The intra-BSC directed retry procedure is as follows: 1.

Steps 1 through 8 in the procedure shown in Figure 16-1 are the random access and immediate assignment procedures, in which the BSS assigns a signaling channel to the MS.

2.

Steps 14 through 24 in the procedure shown in Figure 16-1 are TCH directed retry procedure, in which the BSS assigns a speech channel to the MS.

16.1.2 Inter-BSC directed retry procedure This topic describes the inter-BSC directed retry procedure. Figure 16-2 shows the inter-BSC directed retry procedure.

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Figure 16-2 Inter-BSC directed retry procedure BTS1

MS

Channel Request(1) RACH

BSC1

MSC

BSC2

BTS2

MS

Channel Required(2) Channel Activation(3)

Immediate Assignment Command(5) AGCH SABM(6) SDCCH UA(7)

Establish Indication (CM Service Request)(8)

CR (Complete Layer3 Information)(9)

CM Service Accepted(11) SDCCH SDCCH SDCCH

CC(10) Setup(12) Call Proceeding(13) Assignment Request(14) Handover Required(15)

Handover Request(16) Start T10 Channel Activation(17)

Handover Command(20) Handover Command(21)

Handover Channel Activation Request Acknowledge(19) Acknowledge(18)

Start T8

Handover Access(22)

SDCCH

FACCH PHY INFO(25) FACCH PHY INFO(26) FACCH Establish Indication(28)

SABM(27) FACCH UA(29)

Handover Complete(30) Stop T10 Clear Command(32)

FACCH

FACCH



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16 Directed Retry

The inter-BSC directed retry procedure involves more A-interface signaling procedures than the intra-BSC directed retry procedure. These signaling procedures are described subsequently. For details about other signaling messages, refer to 16.1.1 Intra-BSC Directed Retry Procedure. 1.

When the MS must be handed over to a cell under BSC 2, BSC 1 sends the MSC a Handover Required message requesting the MS to initiate an outgoing inter-BSC handover.

2.

Upon receiving the Handover Required message, the MSC sends BSC 2 a Handover Request message.

3.

BSC 2 activates a new channel and sends a Handover Request Acknowledge message to notify the MSC that the channel is now available.

4.

Upon receiving the Handover Request Acknowledge message, the MSC sends BSC 1 a Handover Command message. BSC 1 forwards the Handover Command message on a TCH to notify the MS of channel access.

5.

Upon receiving the Handover Complete message from BSC 2, the MSC sends BSC 1 a Clear Command message. BSC 1 initiates a local release procedure and sends the MSC a Clear Complete message.

16.1.3 Inter-MSC directed retry procedure This topic describes the inter-MSC directed retry procedure. Figure 16-3 shows the inter-MSC directed retry procedure.

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Figure 16-3 Inter-MSC directed retry procedure MS

BTS1

BSC1

MSC1

MSC2

BTS2

BSC2

MS

Assignment Request(1) Handover Required(2)

Perform Handover(3)

Handover Request(4) Start T10 Channel Activation(5)

Channel Handover Activation Request Acknowledge(6) Radio Channel Acknowledge(7) Acknowledge(8) IAM(9) Handover Command(11) Hand Command(12)

ACM(10)

Start T8

SDCCH

Handover Detect(14)

Handover Access(13) FACCH PHY INFO(15) FACCH PHY INFO(16)

Handover Detect(17)

FACCH Establish Indication(19）


SABM(18) FACCH UA(20） FACCH

Stop T10

Clear Command(24)

Send End Signal(23)

FACCH



For details about the inter-MSC directed retry procedure, refer to 16.1.2 Inter-BSC directed retry procedure.

16.2 Internal BSC Signaling Procedure of Directed Retry The internal BSC signaling procedure of directed retry is categorized by intra-BSC directed retry, inter-BSC directed retry, and inter-MSC directed retry. 16.2.1 Internal BSC Signaling Procedure of the Intra-BSC Directed Retry This describes the internal BSC signaling procedure of the intra-BSC directed retry. 16.2.2 Internal BSC Signaling Procedure of the Inter-BSC Directed Retry This describes the internal BSC signaling procedure of the inter-BSC directed retry. Issue 01 (2007-11-26)


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16.2.3 Internal BSC Signaling Procedure of the Inter-MSC Directed Retry This topic describes the internal BSC signaling procedure of the inter-MSC directed retry.

16.2.1 Internal BSC Signaling Procedure of the Intra-BSC Directed Retry This describes the internal BSC signaling procedure of the intra-BSC directed retry. After the BSC receives the Assignment Request message from the MSC, if the cell where the call is originated has no available TCHs or Assignment Cell Load Judge is enabled, and the Directed Retry Allowed in the Cell Attributes window is selected, a directed retry procedure is triggered. NOTE

Directed retry is a special type of handover.

1.

If the BSC considers that the call meets the handover trigger conditions, it selects a candidate cell from the candidate cell list based on the priority in a descending order. If the candidate cell is under the same BSC as the serving cell, the BSC notifies the candidate cell of initiating an intra-BSC directed retry procedure, and the candidate cell will be the target cell.

2.

A channel in the target cell is assigned and the BTS2 that serves the target cell is notified to activate the channel.

3.

After BTS2 activates the channel, the BSC notifies the MS to send a Handover Command message to BTS1. Meanwhile, BSC2 starts timer T3103 to wait for the Handover Detect message.

4.

On receiving the Handover Detect message, BTS2 continues to wait for the Establishment Indication message and the Handover Complete message.

5.

After BTS2 receives the Handover Complete message, BSC2 stops timer T3103 and considers that the call is set up in the target cell.

6.

The BSC sends an Assignment Complete message to notify the MSC of the assignment completion. The Assignment Complete message carries the information of the target cell. At the same time, BSC1 notifies BTS1 to initiate a local release procedure.

16.2.2 Internal BSC Signaling Procedure of the Inter-BSC Directed Retry This describes the internal BSC signaling procedure of the inter-BSC directed retry. After the BSC receives the Assignment Request message from the MSC, if the cell where the call is originated has no available TCHs or Assignment Cell Load Judge is enabled, and the Directed Retry Allowed in the Cell Attributes window is selected, a directed retry procedure is triggered. If the target cell of the directed retry is an external cell, the inter-BSC directed retry procedure is triggered. NOTE

Directed retry is a special type of handover.

The BSC starts an eight-second timer awaiting the Handover Detect message from the BTS. At the same time, it initiates a forced handover procedure. 1.

16-8

If the BSC considers that the call meets the handover trigger conditions, it selects a candidate cell from the candidate cell list based on the priority in a descending order. If the Huawei Technologies Proprietary

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16 Directed Retry

candidate cell is an external cell, the outgoing BSC directed retry procedure, namely the inter-BSC handover procedure is triggered. 2.

Upon handover initiation, BTS1 sends the MSC a Handover Required message and starts timer T17 to wait for a Handover Command message.

3.

On receiving the Handover Request message from the MSC, BSC1 allocates and activates a channel according to the target cell ID in the message. After channel activation, BTS2 sends the MSC a Handover Request Acknowledge message that carries the Handover Command message.

4.

BTS1 forwards to the MS the Handover Command message that BSC1 receives and at the same time starts timer T8 to wait for the handover completion. If the Clear Command message with the cause value Handover Success or Call Control is received before T8 expires, BSC 1 considers that the handover is successful. If the MS returns to the old channel before T8 expires, BSC1 stops T8 and sends the MSC a Handover Failure message. If T8 expires, BSC1 considers that the call drops and sends the MSC a Clear Request message.

5.

BTS2 forwards the Handover Detect message to the MSC and continues to wait for the Establishment Indication message and the Handover Complete message.

6.

On receiving the Handover Complete message, BTS2 stops timer T3103B2 and sends a Handover Complete message to notify the MSC of handover completion.

7.

On receiving the Clear Command message, BTS2 releases the radio resources the call occupies and returns the MSC a Clear Complete message.

16.2.3 Internal BSC Signaling Procedure of the Inter-MSC Directed Retry This topic describes the internal BSC signaling procedure of the inter-MSC directed retry. The internal BSC signaling procedure of the inter-MSC directed retry is the same as that of the inter-BSC directed retry.

16.3 Abnormal Directed Retry Cases This topic describes the abnormal directed retry cases. 16.3.1 No Available Channels in the Target Cell This topic describes the fault, probable causes, and handling suggestions. 16.3.2 Channel Activation Failure This topic describes the fault, probable causes, and handling suggestions.

16.3.1 No Available Channels in the Target Cell This topic describes the fault, probable causes, and handling suggestions.

Fault When no channels are available in the target cell, BSC 2 sends BSC 1 a handover failure message, and BSC 1 sends the MSC an Assignment Failure message.

Probable Causes No TCHs are available in the target cell. Issue 01 (2007-11-26)


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Handling Suggestions Check whether the target cell is congested. If yes, add TRXs to the target cell.

16.3.2 Channel Activation Failure This topic describes the fault, probable causes, and handling suggestions.

Fault When channel activation in the target cell fails, BSC 2 sends the MSC an Assignment Failure message.

Probable Causes The desired channel in the target cell fails to be activated due to TRX failure.

Handling Suggestions Locate the channel number in the Channel Activation Negative Acknowledge message, and check whether the corresponding TRX fails. If the TRX fails, replace it.

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17 BSC Re-Assignment

17

BSC Re-Assignment

About This Chapter BSC re-assignment refers to a TCH assignment procedure initiated by the BSC after the BSC receives an Assignment Failure message from the MS on the SDCCH. BSC re-assignment raises the rate of assignments on the Um interface. 17.1 BSC Re-Assignment Procedure This topic describes the BSC re-assignment procedure. 17.2 Internal BSC Signaling Procedure of BSC Re-Assignment This topic describes the internal BSC signaling procedure of BSC re-assignment. 17.3 Abnormal BSC Re-Assignment Cases This topic describes the abnormal BSC re-assignment cases.

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17.1 BSC Re-Assignment Procedure This topic describes the BSC re-assignment procedure. Figure 17-1 shows the BSC re-assignment procedure. Figure 17-1 BSC re-assignment procedure MS

BTS

BSC Assignment Command

MSC ……

SDCCH Start T3107

…… Assignment Failure SDCCH

Stop T3107 Channel Activation(1) Channel Activation Acknowldge(2) Start T3107

Assignment Command(3) SDCCH SABM(4) FACCH UA(5) FACCH


Assignment Complete(7) FACCH Stop T3107

17-2

1.

After the BSC receives the Assignment Failure message from the MS, the network stops timer T3107. After internal processing, the BSC sends the BTS a Channel Activate message.

2.

Upon receiving the Channel Activation Acknowledge message from the BTS, the BSC does internal processing.

3.

The BSC sends the MS an Assignment Command message on the SDCCH that is not released.

4.

The MS sends the BTS an SABM frame on the main DCCH specified in the Assignment Command message. Huawei Technologies Proprietary

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5.

The BTS sends the MS a UA frame on the main DCCH.

6.

The BTS sends the BSC an Establish Indication message.

7.

Upon accessing the speech channel, the MS sends the BSC an Assignment Complete message on the main DCCH.

8.

Upon successful assignment of a TCH and a terrestrial circuit, the BSC sends the MSC an Assignment Complete message on the occupied TCH, indicating that the call enters the session state.

17.2 Internal BSC Signaling Procedure of BSC ReAssignment This topic describes the internal BSC signaling procedure of BSC re-assignment. The BSC sends the BTS an Assignment Command message and starts timer T3107. Before timer T3107 expires, the BSC receives an Assignment Failure from the BTS. 1.

Based on the Assignment Request message, the BSC selects an appropriate carrier, activates a channel, and sends the BTS an Assignment Command message. The Assignment Command message carries the information about the new channel.

2.

The BSC records the information on the first assignment, such as the channel assignment requirements, voice version supported by the MSC, TRX number, band attributes, MS maximum and minimum power, call type, handover type, indexes of neighbor cells, requirements for downlink DTX, classmark 2, classmark 3, and cell number.

3.

Based on the circuit pool number in the first assignment, the BSC obtains the circuit capability and attaches the channel type parameter in the Channel Assignment Command message.

4.

Based on the channel priority in the Assignment Request message from the MSC, the BSC fills the channel priority in the Assignment Command message.

5.

Based on the cell type in the first assignment, the BSC fills cell type in the Assignment Command message.

6.

After all relevant requirements are specified, the BSC assigns a channel as required. The subsequent procedure is the same as that of the first assignment.

17.3 Abnormal BSC Re-Assignment Cases This topic describes the abnormal BSC re-assignment cases. 17.3.1 BSC Failure in Initiating a Re-Assignment Procedure This topic describes the fault, probable causes, and handling suggestions.

17.3.1 BSC Failure in Initiating a Re-Assignment Procedure This topic describes the fault, probable causes, and handling suggestions.

Fault After sending an Assignment Command message, the BSC does not initiate a re-assignment procedure although re-assignment is enabled. Issue 01 (2007-11-26)


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Probable Causes Upon receiving the Channel Activation Acknowledge message, the BSC sends the MS an Assignment Command message on the SDCCH and starts timer T3107. If timer T3107 expires, the BSC does not initiate a re-assignment procedure. Upon receiving a Connect Failure message from the BTS, the BSC does not initiate a reassignment procedure. When timer T3107 expires or a Connect Failure message is received, the BSC releases related resources. NOTE

For details, refer to GSM Rec. 0858 and 0808.

Handling Suggestions If the BSC receives a Connect Failure message from the BTS, the transmission quality on the A interface should be improved. To improve the transmission quality on the A interface and to reduce interference, perform a drive test to check the signaling level on the downlink and uplink channels.

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18 Queuing and Preemption

18

Queuing and Preemption

About This Chapter This topic describes queuing and pre-emption. 18.1 Queuing Procedure If no TCHs are available and queuing is allowed, the assignment requests are placed in a waiting queue. When the TCHs are available, they are assigned in the queuing sequence. 18.2 Preemption Procedure Preemption refers to handing over a subscriber with a lower priority to another speech channel or cell so that a subscriber with a higher priority acquires the speech channel resources. 18.3 Internal BSC Signaling Procedure of Queuing and Preemption This topic describes the internal BSC signaling procedure of queuing and pre-emption. 18.4 Abnormal Queuing and Preemption Cases This topic describes the abnormal queuing and pre-emption cases.

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18.1 Queuing Procedure If no TCHs are available and queuing is allowed, the assignment requests are placed in a waiting queue. When the TCHs are available, they are assigned in the queuing sequence. Figure 18-1 shows the queuing procedure. Figure 18-1 Queuing procedure MS

BTS

BSC

MSC

Immediate Assignment Procedure Setup SDCCH Call Proceeding SDCCH

Assignment Request(1) Queuing Indication Start T11

Start Tqho

StopT11

TCH Assignment Procedure(2) Assignment Complete StopTqho TALKING

Release Procedure

18-2

1.

The MSC sends the BSC an Assignment Request message and finds that no speech channel is available. If queuing is allowed, the assignment request is placed in a queue, and timer T11 is started.

2.

When a speech channel is assigned, the queuing procedure is complete, and timer T11 stops.


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18.2 Preemption Procedure Preemption refers to handing over a subscriber with a lower priority to another speech channel or cell so that a subscriber with a higher priority acquires the speech channel resources. Figure 18-2 shows the pre-emption procedure. Figure 18-2 Preemption procedure Low Priority MS

High Priority MS

BTS

BSC

BSC

Talking

Release Procedure or Handover Procedure(2)

Assignment Request

Preemption Start (1)

Start T11 Start Tqho StopT11

TCH Assignment Procedure Assignment Complete StopTqho

TALKING

Release Procedure

1.

The MSC sends the BSC an Assignment Request message and finds that no speech channel is available. If pre-emption is allowed and the priority of the subscriber is higher than the priority of the subscriber that occupies the speech channel, the preemption procedure is initiated.

2.

The subscriber with a lower priority is handed over to another speech channel or cell.

3.

The subscriber with a higher priority seizes the speech channel and the pre-emption procedure is complete.

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18.3 Internal BSC Signaling Procedure of Queuing and Preemption This topic describes the internal BSC signaling procedure of queuing and pre-emption. 1.

Internal BSC signaling procedure of queuing The BSC processes the requests from the MSC, manages the queuing, and determines whether queuing is allowed. Only assignment requests and inter-cell handover requests can be queued. Upon receiving an Assignment Request message, the BSC searches for an available channel. If no channel is available, the BSC sends the MSC a Queuing Indication message and starts timer T11. The timeout value of timer T11 is configurable. The BSC places the Assignment Request message in a queue and starts the message when appropriate. Upon assigning a TCH, the BSC stops timer T11 and sends the MSC an Assignment Complete message.

2.

Internal BSC signaling procedure of pre-emption If no TCH is available, the BSC checks the pre-emption settings and starts a pre-emption procedure. Among all occupied TCHs, the BSC searches for a TCH that has comparatively lower priority and that meets the pre-emption requirements. If no such TCHs are available, the queuing procedure is triggered. The BSC checks whether eMLPP is enabled. If eMLPP is enabled, the preempted call is forced to perform an outgoing cell handover. The call with a higher priority preempts the released TCH. If eMLPP is not enabled, the call with a lower priority is directly released, and the call with a higher priority preempts the TCH.

18.4 Abnormal Queuing and Preemption Cases This topic describes the abnormal queuing and pre-emption cases. 18.4.1 BSC Sending the MSC a Clear Request Message This topic describes the fault, probable causes, and handling suggestions.

18.4.1 BSC Sending the MSC a Clear Request Message This topic describes the fault, probable causes, and handling suggestions.

Description The BSC sends the MSC a Clear Request message.

Probable Causes If the BSC finds no available TCH after timer T11 expiry, the BSC removes the Assignment Request message from the queue and sends the MSC a Clear Request message with the cause No Radio Resource Available. 18-4


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After a TCH allocation fails, the BSC sends the MSC an Assignment Failure message. Then, the MSC stops timer Tqho.

Handling Suggestions Check whether there is an allocable TCH inside the BSC.

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19 Short Message Service

19

Short Message Service

About This Chapter For an idle MS, short messages are transferred on the SDCCH. For a busy MS, however, short messages are transferred on the SACCH. The point-to-point short message procedure comprises two fundamental procedures: mobile originating short message transfer procedure and mobile terminating short message transfer procedure. 19.1 Short Message Transfer Procedure The short message transfer procedure comprises the short message sending and receiving procedures initiated by an idle or a busy MS. 19.2 Internal BSC Signaling Procedure of Short Message Transfer This describes the internal BSC signaling procedure of short messages transfer. 19.3 Abnormal Short Message Transfer Cases This topic describes the abnormal short message transfer cases.

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19.1 Short Message Transfer Procedure The short message transfer procedure comprises the short message sending and receiving procedures initiated by an idle or a busy MS. 19.1.1 Short Message Sending Procedure Initiated by an Idle MS This topic describes the short message sending procedure initiated by an idle MS. 19.1.2 Short Message Receiving Procedure Initiated by an Idle MS This topic describes the short message receiving procedure initiated by an idle MS. 19.1.3 Short Message Sending Procedure Initiated by a Busy MS This topic describes the short message sending procedure initiated by a busy MS. 19.1.4 Short message receiving procedure initiated by a busy MS This topic describes the short message receiving procedure initiated by a busy MS.

19.1.1 Short Message Sending Procedure Initiated by an Idle MS This topic describes the short message sending procedure initiated by an idle MS. Figure 19-1 shows the short message sending procedure initiated by an idle MS. Figure 19-1 Short message sending procedure initiated by an idle MS MS

BTS

BSC

MSC

Immediate Assignment Procedure Authentication Request SDCCH SDCCH

Authentication Response Ciphering Mode Command

SDCCH SDCCH

Ciphering Mode Complete CM Service Accepted (1)

SDCCH SABM (SAPI 3)(2) SDCCH

Establish Indication (SAPI)(3)

UA(4) SDCCH SDCCH

CP DATA(5) CP Acknowledge(6)

SDCCH SDCCH

CP DATA(7) CP Acknowledge(8)

SDCCH Release Procedure

19-2


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l

Steps 1 through 4 in the procedure are the random access and immediate assignment procedures, in which the BSS assigns a signaling channel to the MS.

l

Steps 5 through 8 is the short message sending procedure.

The following describes the short message sending procedure initiated by an idle MS: 1.

The MS sends an SABM frame again, requesting the network to establish the SMS.

2.

The BSC provides a transparent-transmission channel for short message exchange between the MS and the MSC.

In this procedure, the MSC, if possible, sends the BSC an Access Request message for channel allocation. The time for sending the Access Request message is the same as that for an ordinary call. The BSC provides the SMS either by allocating a new channel or by using the original SDCCH. The protocol on Point to Point SMS covers four layers, which are the connection management layer (CM), relay layer (RL), transport layer (TL), and application layer (AL). Both the CP DATA message and the CP Acknowledge message shown in Figure 19-1 are transferred at the CM layer. The CP_DATA message carries the contents of the messages at the RL and AL layers. The CP Acknowledge message is the acknowledgement message of the CP DATA message.

19.1.2 Short Message Receiving Procedure Initiated by an Idle MS This topic describes the short message receiving procedure initiated by an idle MS. Figure 19-2 shows the short message receiving procedure initiated by an idle MS.

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Figure 19-2 Short message receiving procedure initiated by an idle MS MS

BTS

BSC

MSC Paging(1)

Paging Request

Paging Command(2)

PCH Immediate Assignment Prcedure CR(Complete Layer3 Information(3) CC(4) Authentication Request(5) SDCCH Authentication Response(6) SDCCH

Cipherding Mode Commnd(7) SDCCH Cipherding Mode Complete(8)

SDCCH Establis Request(SAPI 3)(10)

CP DATA(9)

SABM(SAPI 3)(11) SDCCH UA(12) SDCCH

Release Indication(9) Establish Confirm(SAPI 3)(13) CP DATA(14)

SDCCH CP Acknowledge(15) SDCCH

CP DATA(16)

SDCCH

CP Acknowledge(17) SDCCH Release Procedure

In Figure 19-2, l

Steps 1 through 3 is the paging response and immediate assignment procedure. The MSC sends a Paging Command message. The MS requests for an SDCCH channel and returns a Paging Response message.

l

Steps 14 through 17 is a connection establishment and short message sending procedure. During the short message mobile terminating procedure, the BSC sends the MS an Establishment Request message, requesting for connection establishment. If the BSC

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receives an Establishment Confirm message from the MS, the channel for SMS is established. The BSC transfers short messages on the transparent channel until the procedure is complete.

19.1.3 Short Message Sending Procedure Initiated by a Busy MS This topic describes the short message sending procedure initiated by a busy MS. Figure 19-3 shows the short message sending procedure initiated by a busy MS. Figure 19-3 Short message sending procedure initiated by a busy MS MS

BTS

BSC

MSC

ACTIVE CALL CM Service Request(1) FACCH CM Service Accepted(2) FACCH SABM (SAPI 3)(3) Establish Indication(4)

FACCH UA(5) FACCH

CP DATA(6) SACCH CP Acknowledge(7) SACCH CP DATA(8) SACCH

CP Acknowledge(9)

SACCH ACTIVE CALL

The following describes the short message sending procedure initiated by a busy MS: 1.

The MS sends the MSC a CM Service Request message on the FACCH. If the MSC responds with a CM Service Accepted message, a link at the CC layer is established.

2.

A link at the CC layer is established on the SACCH for sending short messages.

19.1.4 Short message receiving procedure initiated by a busy MS This topic describes the short message receiving procedure initiated by a busy MS. Figure 19-4 shows the short message receiving procedure initiated by a busy MS. Issue 01 (2007-11-26)


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Figure 19-4 Short message receiving procedure initiated by a busy MS MS

BTS

BSC

MSC

ACTIVE CALL Establish Request(SAPI 3)(2)

CP DATA(1)

SABM (SAPI 3)(3) FACCH UA(5)

Establish Confirm (SAPI 3)(5)

FACCH

CP DATA(6) SACCH SACCH

CP Acknowledge(7) CP DATA(8)

SACCH

CP Acknowledge(9) SACCH ACTIVE CALL

The following describes the short message receiving procedure initiated by a busy MS: 1.

Upon receiving a CP DATA message from the MSC, the BSC establishes a link for receiving short messages at the RR layer.

2.

Upon receiving a CP Acknowlege message from the MS, the MSC sends short messages.

19.2 Internal BSC Signaling Procedure of Short Message Transfer This describes the internal BSC signaling procedure of short messages transfer.

19-6

1.

Based on the classmark reported by the MS, the BSC checks whether the MS supports SMS.

2.

On receiving the short messages from the MS, the BSC checks the value of the parameter Short Message Uplink Disabled. You can set the parameter through the following procedure: On the Cell Attributes tab page, click Call Control. In the displayed dialog box, click Advanced. Then click the Call Control tab and set the parameter. If the parameter is set to Yes, short message cannot be sent.

3.

On receiving the short messages from the MS, the BSC checks the value of the parameter Short Message Downlink Disabled. You can set the parameter through the following procedure: On the Cell Attributes tab page, click Call Control. In the displayed dialog box, click Advanced. Then click the Call Control tab and set the parameter. If the parameter is set to Yes, short messages cannot be sent. Huawei Technologies Proprietary

Issue 01 (2007-11-26)



19.3 Abnormal Short Message Transfer Cases This topic describes the abnormal short message transfer cases. 19.3.1 Short Message Sending Failure due to Authentication and Ciphering Disabled This topic describes the fault, probable causes, and handling suggestions.

19.3.1 Short Message Sending Failure due to Authentication and Ciphering Disabled This topic describes the fault, probable causes, and handling suggestions.

Fault Some MSs fail to send short messages because the authentication and ciphering function is disabled.

Probable Causes The short message procedure specified in the GSM protocols involves the authentication and ciphering procedure. For some MSs, short message sending fails if no authentication and ciphering procedure is involved in the short message procedure.

Handling Suggestions The MSC initiates an authentication and ciphering procedure.

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20

20 Short Message Service Cell Broadcast

Short Message Service Cell Broadcast

About This Chapter The short message service cell broadcast (SMSCB) is similar to the paging station broadcast service. The operators broadcast messages to the subscribers in the specified areas. The subscribers that subscribe to the service receive the messages broadcast by the operators. 20.1 SMSCB Procedure The SMSCB procedure comprises the CBC-BSC SMSCB procedure and the BSC-BTS SMSCB procedure. 20.2 Internal BSC Signaling Procedure of the SMSCB This describes the internal BSC signaling procedure of the SMSCB. 20.3 Abnormal SMSCB Cases This topic describes the abnormal SMSCB cases.

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20.1 SMSCB Procedure The SMSCB procedure comprises the CBC-BSC SMSCB procedure and the BSC-BTS SMSCB procedure. 20.1.1 CBC-BSC SMSCB Procedure This topic describes the CBC-BSC SMSCB procedure. 20.1.2 BSC-BTS SMSCB Procedure This topic describes the BSC-BTS SMSCB procedure.

20.1.1 CBC-BSC SMSCB Procedure This topic describes the CBC-BSC SMSCB procedure.

Procedure for Sending or Replacing a Message Figure 20-1 shows the procedure for sending or replacing a message. Figure 20-1 Procedure for Sending or Replacing a Message CBC

BSC

Write Replace Request1

Report Response2

1.

2.

The CBC sends the BSC a Write Replace Request message. l

If the message is new, the BSC saves the message in the message library.

l

If the message is sent for replacing the existing message, the BSC deletes the existing message and saves the new message in the message library.

The BSC sends the CBC a response message. l

If the parameters in the Write Replace Request message are legal, the CBC sends a Report Response message.

l

If the parameters in the Write Replace Request message are illegal, the CBC sends a Reject Response message.

Deleting an Existing Message Figure 20-2 shows the procedure for deleting an existing message. 20-2


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Figure 20-2 Procedure for deleting an existing message CBC

BSC

Kill Request1

Report Response2

1.

The CBC sends the BSC a Kill Request message.

2.


If the parameters in the Kill Request message are legal, the BSC deletes the existing message and sends the CBC a Report Response message.

l

If the parameters in the Kill Request message are illegal, the BSC sends the CBC a Reject Response message.

Querying the CBCH Status Figure 20-3 shows the procedure for querying the CBCH status. Figure 20-3 Procedure for querying the CBCH status CBC

BSC

Status CBCH Query Request(1)

Status CBCH Query Response(2)

1.

The CBC sends the BSC a Status CBCH Query Request message.

2.


If the parameters in the Status CBCH Query Request message are legal, the BSC sends the CBC a Status CBCH Query Response message.

l

If the parameters in the Status CBCH Query Request message are illegal, the BSC sends the CBC a Reject Response message.

Querying the Message Status Figure 20-4 shows the procedure for querying the message status. Issue 01 (2007-11-26)


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Figure 20-4 Procedure for querying the message status CBC

BSC

Status Message Query Request(1)

Status Message Query Response(2)

1.

The CBC sends the BSC a Status Message Query Request message.

2.


If the parameters in the Status Message Query Request message are legal, the BSC sends the CBC a Status Message Query Response message.

l

If the parameters in the Status Message Query Request message are illegal, the BSC sends the CBC a Reject Response message.

Resetting a Cell Figure 20-5 shows the procedure for resetting a cell. Figure 20-5 Procedure for resetting a cell CBC

BSC

Reset Request(1)

Restart Indication Response(2)

1.

The CBC sends the BSC a Reset message.

2.


If the CBCH of the specified cell is normal, the BSC responds with a Restart Indication Response message.

l

If the CBCH of the specified cell is abnormal, the BSC responds with a Failure Indication Response message.

Setting the DRX Figure 20-6 shows the procedure for setting the discontinuous reception (DRX). 20-4


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Figure 20-6 Procedure for setting the DRX CBC

BSC

Set DRX Request(1)

Set DRX Response(2)

1.

The CBC sends the BSC a Set DRX Request message.

2.


If the parameters in the Set DRX Request message are legal, the BSC sends the CBC a Set DRX Response message.

l

If the parameters in the Kill Request message are illegal, the BSC sends the CBC a Reject Response message.

20.1.2 BSC-BTS SMSCB Procedure This topic describes the BSC-BTS SMSCB procedure. The BSC sends the BTS the CBS information through an SMS Broadcast Command message, which specifies the channel to be used. See Figure 20-7. Figure 20-7 BSC Sending an SMS Broadcast Command Message BSC

BTS

SMS Broadcast Command

MS

SMS 1(1) CBCH SMS 2(2) CBCH

…… SMS n(3) CBCH

The BTS reports the load status of the CBCH to the BSC through a CBCH Loading Indication message and requests the BSC to perform flow control. See Figure 20-8.

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Figure 20-8 BTS Sending the BSC a CBCH Loading Indication Message BSC

BTS

CBCH Loading Indication(1)

20.2 Internal BSC Signaling Procedure of the SMSCB This describes the internal BSC signaling procedure of the SMSCB. 1.

The CBIP in the GXPUT obtains the IP addresses of the CBC and the CBIP from the database and establishes communication through a SOCKET link.

2.

The CBIP obtains the cell information from the database, filters the cells without CBCHs, and writes in the cell information library the information of the cells with CBCHs .

3.

The CBIP obtains the contents of the SMS to be broadcast from the CBC and writes the contents in the message library. The contents include the number of retransmissions and the retransmission interval.

4.

The GXPUT receives the messages from the CBC, and the CBPI processes the messages.

5.

Upon expiry of the SMSCB timer, the CBIP checks every cell for messages to be broadcast. l

If there are messages to be broadcast, the CBIP sends the messages to the corresponding GXPUM, and the GEIUB forwards the messages to the corresponding BTS. The GXPUT manages the SMSCB of the entire BSC.

l

If there are no messages to broadcast, no processing is required.

NOTE

The delivery of the cell broadcast messages is triggered by SMSCB timer expiry.

Figure 20-9 SMSCB procedure

GMPS

GEPS

G X P U T

G X P U M

G T N U

G E I U B

G X P U M

G T N U

G E I U B

20.3 Abnormal SMSCB Cases This topic describes the abnormal SMSCB cases. 20-6


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20.3.1 MS Failure in Receiving Cell Broadcast Messages This describes the fault, probable causes, and handling suggestions. 20.3.2 CBCH Not Configured in a Cell This describes the fault, probable causes, and handling suggestions.

20.3.1 MS Failure in Receiving Cell Broadcast Messages This describes the fault, probable causes, and handling suggestions.

Description The MS fails to receive call broadcast messages.

Analysis The probable causes are as follows: 1.

The SMSCB switch of the MS is turned off, and the relevant channel number is not configured.

2.

The setting of the IP address in the GXPUT and that in the CBC are different.

3.

The communication between the GXPUT and the CBC is disrupted. For example, the CBC Communication Disrupted alarm with the ID 102 is generated.

Handling Suggestions Locate the problem through message tracing and on the Site Maintenance System. 1.

Check whether SMS Broadcast Command messages exist on the Abis interface of the relevant cell.

2.

Send the system information of the relevant cell on the Site Maintenance System and check whether the IE CBCH DESP message in System Information Type 4 is correct.

20.3.2 CBCH Not Configured in a Cell This describes the fault, probable causes, and handling suggestions.

Description l

The cell is abnormal.

l

The CBC cannot perform any operation or the operation is performed unsuccessfully.

l

No cell broadcast messages are sent.

l

No cell broadcast messages are received.

Analysis The cause value of the failed signaling is Specified Cell Not Found. The problem lies in that the CBCH of the cell is not configured. Issue 01 (2007-11-26)


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Handling Suggestions Check whether the CBCH of the cell is configured. If not, add the CBCH on the BSC6000 Local Maintenance Terminal.

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Huawei Sig Guide

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