Nokia - Dynamic Abis Pool

GSM/EDGE BSS, Rel. RG20(BSS), Operating Documentation, Issue 04

Feature description

BSS10045: Dynamic Abis DN0431625 Issue 5-0 Approval Date 2010-04-30

Confidential

BSS10045: Dynamic Abis

The information in this document is subject to change without notice and describes only the product defined in the introduction of this documentation. This documentation is intended for the use of Nokia Siemens Networks customers only for the purposes of the agreement under which the document is submitted, and no part of it may be used, reproduced, modified or transmitted in any form or means without the prior written permission of Nokia Siemens Networks. The documentation has been prepared to be used by professional and properly trained personnel, and the customer assumes full responsibility when using it. Nokia Siemens Networks welcomes customer comments as part of the process of continuous development and improvement of the documentation. The information or statements given in this documentation concerning the suitability, capacity, or performance of the mentioned hardware or software products are given "as is" and all liability arising in connection with such hardware or software products shall be defined conclusively and finally in a separate agreement between Nokia Siemens Networks and the customer. However, Nokia Siemens Networks has made all reasonable efforts to ensure that the instructions contained in the document are adequate and free of material errors and omissions. Nokia Siemens Networks will, if deemed necessary by Nokia Siemens Networks, explain issues which may not be covered by the document. Nokia Siemens Networks will correct errors in this documentation as soon as possible. IN NO EVENT WILL Nokia Siemens Networks BE LIABLE FOR ERRORS IN THIS DOCUMENTATION OR FOR ANY DAMAGES, INCLUDING BUT NOT LIMITED TO SPECIAL, DIRECT, INDIRECT, INCIDENTAL OR CONSEQUENTIAL OR ANY LOSSES, SUCH AS BUT NOT LIMITED TO LOSS OF PROFIT, REVENUE, BUSINESS INTERRUPTION, BUSINESS OPPORTUNITY OR DATA,THAT MAY ARISE FROM THE USE OF THIS DOCUMENT OR THE INFORMATION IN IT. This documentation and the product it describes are considered protected by copyrights and other intellectual property rights according to the applicable laws. The wave logo is a trademark of Nokia Siemens Networks Oy. Nokia is a registered trademark of Nokia Corporation. Siemens is a registered trademark of Siemens AG. Other product names mentioned in this document may be trademarks of their respective owners, and they are mentioned for identification purposes only. Copyright © Nokia Siemens Networks 2010. All rights reserved

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Important Notice on Product Safety This product may present safety risks due to laser, electricity, heat, and other sources of danger. Only trained and qualified personnel may install, operate, maintain or otherwise handle this product and only after having carefully read the safety information applicable to this product. The safety information is provided in the Safety Information section in the “Legal, Safety and Environmental Information” part of this document or documentation set.

The same text in German:

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Wichtiger Hinweis zur Produktsicherheit Von diesem Produkt können Gefahren durch Laser, Elektrizität, Hitzeentwicklung oder andere Gefahrenquellen ausgehen. Installation, Betrieb, Wartung und sonstige Handhabung des Produktes darf nur durch geschultes und qualifiziertes Personal unter Beachtung der anwendbaren Sicherheitsanforderungen erfolgen. Die Sicherheitsanforderungen finden Sie unter „Sicherheitshinweise“ im Teil „Legal, Safety and Environmental Information“ dieses Dokuments oder dieses Dokumentationssatzes.

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DN0431625 Issue 5-0


Table of contents This document has 28 pages. Summary of Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

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1

Overview of Dynamic Abis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9

System impact of Dynamic Abis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Impact on transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Impact on BSS performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 User interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Impact on Network Switching Subsystem (NSS) . . . . . . . . . . . . . . . . . . 14 Impact on NetAct products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Impact on mobile stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Impact on interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3 3.1 3.2 3.3 3.4

Technical description of Dynamic Abis . . . . . . . . . . . . . . . . . . . . . . . . . Capacity-related parameters of Dynamic Abis. . . . . . . . . . . . . . . . . . . . Abis L1 frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . GPRS temporary block flow (TBF). . . . . . . . . . . . . . . . . . . . . . . . . . . . . EGPRS temporary block flow (TBF) . . . . . . . . . . . . . . . . . . . . . . . . . . .

16 16 17 18 18

4 4.1 4.2 4.3

Functionality of Dynamic Abis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dynamic Abis pool management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . EGPRS dynamic Abis pool connections . . . . . . . . . . . . . . . . . . . . . . . . Dynamic Abis pool in a PCU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

20 20 22 23


3


List of figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10

4

An example of T1 allocation . . Equation 1. . . . . . . . . . . . . . . . Equation 2. . . . . . . . . . . . . . . . Equation 3. . . . . . . . . . . . . . . . Equation 4. . . . . . . . . . . . . . . . Equation 5. . . . . . . . . . . . . . . . Equation 6. . . . . . . . . . . . . . . . Equation 7. . . . . . . . . . . . . . . . Equation 8. . . . . . . . . . . . . . . . Equation 9. . . . . . . . . . . . . . . .


....... ....... ....... ....... ....... ....... ....... ....... ....... .......

...... ...... ...... ...... ...... ...... ...... ...... ...... ......

....... ....... ....... ....... ....... ....... ....... ....... ....... .......

...... ...... ...... ...... ...... ...... ...... ...... ...... ......

.......7 . . . . . . 24 . . . . . . 24 . . . . . . 24 . . . . . . 25 . . . . . . 26 . . . . . . 26 . . . . . . 27 . . . . . . 27 . . . . . . 28

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List of tables Table 1 Table 2 Table 3 Table 4 Table 5 Table 6

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Required additional or alternative hardware or firmware . . . . . . . . . . . . 9 Required software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Impact of Dynamic Abis on BSC units . . . . . . . . . . . . . . . . . . . . . . . . . 12 Counters of Dynamic Abis Measurement . . . . . . . . . . . . . . . . . . . . . . . 14 Maximum number of DAPs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Coding schemes and need for master and slave channels on Abis. . . 17


5

Summary of Changes


Summary of Changes Changes between document issues are cumulative. Therefore, the latest document issue contains all changes made to previous issues. Changes between issues 5-0 (2010/04/30, BSS15 RG20) and 4-1 (2000/02/02, BSS14 RG10) System impact of Dynamic Abis (2) – Updated the section, Requirements for release RG20(BSS) – Updated the section, User interface to include a new alarm- 3483 PCU RESTARTED Functionality of Dynamic Abis (4) – Updated section Dynamic Abis pool management, EGPRS dynamic Abis pool connections, and Dynamic Abis pool in a PCU to integrate the impact of BSS21232: AUTOMATIC EDAP REALLOCATION IN PCU feature

Changes made between issues 4-1 and 4-0 Information on InSite BTS has been removed. Changes made between issues 4-0 and 3-0 Information on Downlink Dual Carrier have been added. Information on PCU2-E has been added and modified in sections System impact of Dynamic Abis, Technical description of Dynamic Abis, and Functionality of Dynamic Abis. Information on PCU2-D/U has been modified in section Functionality of Dynamic Abis.

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Overview of Dynamic Abis

1 Overview of Dynamic Abis Dynamic Abis splits Abis E1/T1 transmission lines into: • •

permanent 16 kbit/s sub-timeslots for signalling, voice, and data Dynamic Abis pools (DAP) for radio timeslots that require more than 16 kbit/s transmission capacity from Abis

The DAP area used by GPRS/EDGE is called the EGPRS dynamic Abis pool (EDAP). The DAP can be shared by a number of EDGE-capable transceivers (TRXs) in the same base control function (BCF) cabinet. The DAP and the TRXs sharing it have to be allocated to the same Abis E1/T1 transmission line. The following figure illustrates an example of T1 Dynamic Abis configuration; DAP 1 is shared by TRXs 1, 3, and 5: TSL 1

MBCCH

SDCCH

TCHF

TCHF

TCHF

TCHF

TCHF

TCHF

TCHF

TCHF

TCHF

TCHF

TCHF

TCHD

TCHD

TCHD

MBCCH

SDCCH

TCHF

TCHF

TCHF

TCHF

TCHF

TCHF

TCHF

TCHF

TCHF

TCHF

TCHF

TCHD

TCHD

TCHD

MBCCH

SDCCH

TCHF

TCHF

TCHF

TCHF

TCHF

TCHF

TCHF

TCHF

TCHF

TCHF

TCHF

TCHD

TCHD

TCHD

EDGE TRX 1 BTS 1, SEGMENT 1 TRX 2

TSL 12

EDGE TRX 3 BTS 2, SEGMENT 2

BCF

TRX 4

EDGE TRX 5 BTS 3, SEGMENT 3 TRX 6

TSL 13

DAP 1 6 X 64k

TSL 18

TSL 24

TSIG5

TSIG6

TSIG3

TSIG4

TSIG1

Figure 1

OMU

Signalling

TSIG2

An example of T1 allocation

In the BSC there can be two different GPRS/EDGE territory types: 1. GPRS territory with the following coding schemes:

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Overview of Dynamic Abis


• CS1 and CS2 packet data channels, no DAP required • CS1 - CS4 packet data channels, DAP required 2. EGPRS territory with the following coding schemes: • MCS1 - MCS9 and CS1 - CS2, DAP required • MCS1 - MCS9 and CS1 - CS4, DAP required

f Sharing the EGPRS dynamic Abis pool (EDAP) between several cabinets may damage the transceiver or transmission unit (TRU) hardware. One EDAP resource should not be shared between several base control function (BCF) cabinets. Benefits of Dynamic Abis Dynamic Abis saves up to 60 per cent of the Abis transmission expansion cost, since it allows Abis dimensioning to be performed closer to the average data rates instead of at peak rates. This also applies to the reduced number of 2M BSC interfaces needed. Related topics Descriptions • • • • •

BSS20089: Extended Dynamic Allocation BSS9006: GPRS System Feature Description BSS10091: EDGE System Feature Description BSS20094: Extended Cell for GPRS/EDGE BSS21228: Downlink Dual Carrier Feature Description

Instructions • • •

Abis EDGE Dimensioning Testing and activating BSS10083: EGPRS Dynamic Abis Pool Handling

Reference • • • •

8

ES - Abis Interface Configuration 1 Traffic Measurement 76 Dynamic Abis Measurement BSS Radio Network Parameter Dictionary

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System impact of Dynamic Abis

2 System impact of Dynamic Abis The system impact of BSS10045: Dynamic Abis is specified in the sections below. Dynamic Abis is always required with EGPRS, Coding Schemes CS-3 and CS-4, Extended Cell for GPRS/EDGE, and Downlink Dual Carrier.

2.1

Requirements Hardware requirements Network element

Hardware/firmware required

BSC

Packet control unit (PCU) plug-in units

BTS

Flexi EDGE BTS, Flexi Multiradio BTS, UltraSite EDGE BTS, MetroSite EDGE BTS, and/or BTS plus

TCSM

No requirements

SGSN

No requirements

Table 1

Required additional or alternative hardware or firmware

Software requirements Network element

Software release required

BSC

S15

Flexi EDGE BTS

EX4

Flexi Multiradio BTS EXM4 UltraSite EDGE BTS

CX8.0

MetroSite EDGE BTS

CXM8.0

BTS plus

BRG2

Talk-family BTS

Not supported

MSC/HLR

No requirements

SGSN

SG8.0

NetAct

OSS5.2 CD set3

Table 2

Required software

Frequency band support The BSC supports Dynamic Abis on the following frequency bands: • • • •

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GSM GSM GSM GSM

800 900 1800 1900

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2.2


Restrictions Only Flexi EDGE BTSs, Flexi Multiradio BTS, UltraSite EDGE BTSs, and MetroSite EDGE BTSs are able to use Dynamic Abis allocation. Furthermore, only EDGE-capable TRXs (EDGE TRXs) are capable of using shared EGPRS dynamic Abis pool (EDAP) resources. PCUPCM allocation restrictions • • •

One EDAP cannot be divided to separate packet control unit pulse code modulations (PCUPCMs). digital signal processor (DSP) HW restriction: one PCUPCM timeslot (TSL) (64 kbit/s = 4 x 16 kbit/s sub-timeslots (SUB-TSLs) must be handled in one DSP core. The system does not allow an EDAP area to overlap with another EDAP area or with GPRS/EDGE channels on PCMs.

Internal PCU1 restrictions •

•

•

•

• •

•

Not more than 204 EDAP channels can be configured in one PCU1. This is because there must also be space for at least one EGPRS channel for every four EDAP channels (51 EGPRS channels + 204 EDAP channels = 255 Abis channels). In one logical PCU1 there are 16 DSP cores identified by even or odd indexes. In a PCU1, one DSP core can handle only one EDAP, but one EDAP can be shared by several DSP cores. The DSP cores sharing an EDAP must be either even-indexed or odd-indexed DSP cores. Therefore the maximum number of DSP cores per one EDAP is eight. In the PCU1s, one DSP core can handle 0 to 20 channels (16 kbit/s), including active EDAP channels, EGPRS channels, and GPRS channels. The maximum number of 16 kbit/s channels per PCU is 256. A DSP core attached to EDAP can handle 16 radio timeslots, so four slave channels are needed to reach the maximum number of channels. A GPRS-dedicated DSP core can handle 20 GPRS master channels because slave channel reservation is not needed. All EGPRS channels of one EDGE TRX must be handled in the DSP core which handles the related EDAP. If an EDAP is handled in several DSP cores, the EGPRS channels of one EDGE TRX can be divided to several DSP cores in a PCU1. In the uplink direction, the PCU1 allocates uplink EDAP resources for the highest CS/MCS granted for an MS during the TBF's lifetime. In PCU1 there is one synchronisation master channel (SMCH) for every EDAP. Because of DSP restrictions, the SMCH must be allocated on PCUPCM0. To ensure that each EDAP has SMCH candidates on PCUPCM0, the PCU1 reserves a number of sub-timeslots from PCUPCM0 exclusively for each EDAP, that is, for the EGPRS on the TRXs attached to the EDAP. PCU and PCU-S can handle 128 radio timeslots. This issue should be taken into account in PCU dimensioning.

Internal PCU2-D and PCU2-U restrictions •

•

10

In one logical PCU2-D or PCU2-U there are eight DSP cores. In a PCU2-D or PCU2U, one DSP core can handle two EDAPs, but one EDAP can be shared by several DSP cores. In the PCU2-D or PCU2-U, one DSP core can handle 0 to 40 channels (16 kbit/s), including active EDAP channels, EGPRS channels, and GPRS channels. The


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• •

maximum number of 16 kbit/s channels per PCU2-D or PCU2-U is 256. Note that the maximum number of EGPRS channels and GPRS channels is 32 per DSP core. To reach 40 channels there have to be at least eight EDAP channels. All EGPRS channels of one EDGE TRX must be handled in the single DSP core which handles the related EDAP. In PCU2-D or PCU2-U, there is one SMCH for each EDAP in every DSP. The PCU2D or PCU2-U can allocate the SMCHs to both PCUPCMs 0 and 1.

Internal PCU2-E restrictions •

•

•

In the PCU2-E, one DSP core can handle up to 212 channels (16kbit/s), including active EDAP channels, EGPRS channels, and GPRS channels. The maximum number of Abis channels per PCU2-E is 512 in BSC3i 660, BSC3i 1000, and BSC3i 2000. In Flexi BSC, the maximum number of Abis channels per PCU2-E is 1024. Not more than 816 EDAP channels can be configured in one PCU2-E. This is because there must also be space for at least one EGPRS channel for every four EDAP channels (204 EGPRS channels + 816 EDAP channels = 1020 Abis channels). One EDAP cannot be divided between several DSPs but one DSP can have a maximum of 10 EDAPs.

Common restrictions for both PCU1 and PCU2 •

•

•

2.3

EDAP resource usage in a PCU dynamically reserves the DSP resources in the PCU. When EGPRS and GPRS calls (TBFs) in EGPRS territory use EDAP resources, allocation of the new packet switch (PSW) radio timeslots to the PCU may fail due to the current EDAP and DSP resource load. When new PSW radio timeslots are added/upgraded to the PCU, the PCU DSP resource capacity used for the EDAPs decreases. This may lead to a situation where the desired CS/modulation and coding scheme (MCS) cannot be assigned to the TBFs. In downlink direction, the TBFs can adjust the downlink data according to limited Dynamic Abis capacity. In uplink direction, the PCU DSP resource load situation may cause a situation in which the uplink transmission turns cannot be assigned for the MSS, for example if adequate uplink Dynamic Abis resources cannot be allocated. The EDAP size itself also limits the CS/MCS usage for both downlink and uplink TBFs.

Impact on transmission More transmission capacity is needed because Dynamic Abis splits Abis E1/T1 transmission lines into: • •

2.4

permanent 16 kbit/s sub-timeslots for signalling, voice, and data Dynamic Abis Pools (DAP) for radio timeslots that require more than 16 kbit/s transmission capacity from Abis

Impact on BSS performance OMU signalling No impact.

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TRX signalling No impact. Impact on BSC units BSC unit

Impact

OMU

No impact

MCMU

No impact

BCSU

No impact

PCU

You can create a maximum of 16 DAPs in one PCU1, PCU2-D, or PCU2-U. In case of PCU2-E, the maximum number of EDAPs is 60 in BSC3i 660, BSC3i 1000, BSC3i 2000, and Flexi BSC. There can be a maximum of 256 channels (including dedicated GPRS + default GPRS + EDAP channels) in one PCU1, PCU2-D, or PCU2-U, of which 204 can be EDAP channels. The maximum number of channels is 512 in PCU2-E in BSC3i 660, BSC3i 1000, and BSC3i 2000. In Flexi BSC, the maximum number of channels is 1024.

Table 3

Impact of Dynamic Abis on BSC units

Impact on BTS units No impact.

2.5

User interface BSC MMI The following command groups and MML commands are used to handle dynamic Abis pool: •

Abis Interface Configuration: ESE, ESM, ESG, ESI

In addition, the MML command ERM (Transceiver Handling) is used to modify transceiver (TRX) parameters, including the DAP parameter. For more information on the command groups and MML commands, see MML commands. BTS MMI Dynamic Abis cannot be managed with BTS MMI. BSC parameters Dynamic Abis Pool (DAP) radio network object parameters • • • •

12

BCSU ID (BCSU) circuit (CRCT) new first time slot (NFT) new last time slot (NLT)


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• • • •

packet service entity identifier (PSEI) PCU index (PCU) pool identification (ID) pool size (SIZE)

Transceiver (TRX) radio network object parameters • •

TRX(s) connected to pool(s) (TRXS) dynamic abis pool ID (DAP)

For more information, see BSS Radio Network Parameter Dictionary. Alarms The following listed alarms can be generated in connection with Dynamic Abis: Alarm Type

This alarm is set when...

3068 EGPRS DYNAMIC ABIS POOL FAILURE

• • •

3273 GPRS/EDGE TERRITORY FAILURE

BSC cannot attach DAP circuits to EDAP (all successfully connected DAP circuits are attached to EDAP) BSC cannot connect one DAP circuit to EDAP because of connection failure EDAP configuration update or an EDAP modification to PCU fails The PCU capacity (for example, PCU DSP resource load for ongoing EGPRS calls using EDAP resources) may limit the EGPRS and GPRS RR procedures. It is possible that new GPRS traffic channels (TCHs) cannot be added to the PCU. Therefore, territory upgrades fail either partly or completely.

GPRS/EDGE territory size in the BTS is below the limit specified by the BTS-specific radio network parameter default GPRS capacity (CDEF). The BSC has not been able to add more radio channels to the territory within informing delay. The BSC's ability to transfer GPRS/EDGE traffic in the BTS has been reduced or totally prevented. For more information, see Problems with territory operations in Handling Common Problem Situations in BSC.

3483 PCU RESTARTED

PCU Hot restart is initiated and cancelled after restart is completed. During the DAP operation, the PCU Hot restart is performed to the PCU, where the DAP is connected

For more information, see Failure printouts (2000-3999). For an overview, see Overview of Dynamic Abis. Measurements and counters The following measurements and counters are related to Dynamic Abis: 1 Traffic Measurement Traffic Measurement includes counters, for example, for partially successful and failed territory upgrade requests. 76 Dynamic Abis Measurement

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The purpose of Dynamic Abis Measurement is to help you to monitor and control the use of EDAPs and to give you a better possibility to configure and optimise, for example, the EDAP sizes. There are separate counters for both uplink and downlink measurements. Name

Number

TOTAL PCM SUBTSLS IN EDAP

076000

AVERAGE DL EDAP USAGE

076001

AVERAGE UL EDAP USAGE

076002

AVERAGE EDAP USAGE DEN

076003

PEAK DL EDAP USAGE

076004

PEAK UL EDAP USAGE

076005

UL TBFS WITHOUT EDAP RES

076006

DL TBFS WITHOUT EDAP RES

076007

DL TBFS WITH INADEQUATE EDAP RES

076008

UL EDAP ALLOCATION REQUESTS

076009

DL EDAP ALLOCATION REQUESTS

076010

TOT NBR OF PCM STS IN EDAP UL

076017

DYNAMIC ABIS DENOM UL

076018

UL MCS LIMITED BY PCU

076019

DL MCS LIMITED BY PCU

076020

Table 4

Counters of Dynamic Abis Measurement

For more information, see 1 Traffic Measurement and 76 Dynamic Abis Measurement.

2.6

Impact on Network Switching Subsystem (NSS) No impact.

2.7

Impact on NetAct products NetAct Administrator No impact. NetAct Monitor NetAct Monitor can be used to monitor all alarms related to Dynamic Abis. For a list of the alarms, see section Alarms. NetAct Optimizer No impact. NetAct Planner You may have to take Dynamic Abis into consideration in TRX dimensioning.

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NetAct Configurator NetAct Configurator can be used to configure the radio network parameters related to Dynamic Abis. For more information, see BSS RNW Parameters and Implementing Parameter Plans in Nokia Siemens Networks NetAct Product Documentation. For a list of the radio network parameters, see section BSC parameters. NetAct Reporter NetAct Reporter can be used to view and create reports from measurements related to Dynamic Abis. For a list of the measurements, see section Measurements and counters. NetAct Tracing No impact.

2.8

Impact on mobile stations GPRS/EDGE-capable mobile stations are required.

2.9

Impact on interfaces Impact on radio interface No impact. Impact on Abis interface • •

Abis Telecom interface No impact. Abis O&M interface Dynamic pool info IE has been added to the following Abis O&M messages: • BTS_CONF_DATA • AC_BSC_CIRCUITS_ALLOCATED

Impact on A interface No impact. Impact on Gb interface No impact.

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Technical description of Dynamic Abis


3 Technical description of Dynamic Abis 3.1

Capacity-related parameters of Dynamic Abis Dynamic Abis pool (DAP) is a continuous block of 64 kbit/s timeslots reserved from external pulse code modulation line (ET-PCM). The maximum size of one DAP in a packet control unit (PCU) is 24 timeslots but the BTSs, with the exception of Flexi EDGE BTS, limit the usable size into 12 timeslots. The maximum number of all DAPs in one PCU is 51 timeslots in PCU1, PCU2-D, and PCU2-U. The maximum number of DAPs in one PCU is 204 timeslots in PCU2-E in Flexi BSC. In BSC3i 1000 and BSC3i 2000, the maximum number of DAPs is 102 timeslots in PCU2-E. There can be a maximum of 16 DAPs per PCU in PCU1, PCU2-D, and PCU2-U. The maximum number of DAPs per PCU is 60 in PCU2-E in BSC3i 660, BSC3i 1000, BSC3i 2000, and Flexi BSC. Table Maximum number of DAPs lists the maximum number of DAPs in different BSC variants. The value range of DAP identifier is from 1 to 1800. BSC variant

Number of DAPs

BSCi

128

BSC2i

256

BSC3i 660

384

BSC3i 1000

800

BSC3i 2000

1600

Flexi BSC

1800

Table 5

Maximum number of DAPs

The theoretical maximum number of transceivers (TRXs) per DAP is 20. However, since TRXs using DAP resources must be allocated to the same Abis external pulse code modulation (ET-PCM) line with EGPRS dynamic Abis pool (EDAP), the maximum TRX count for a DAP is 12 in the ETSI environment and 8 in the ANSI environment. The capacity of a specific EDAP depends on: • • • •

the total number of EDAPs in the PCU the EDAP size the number of EDGE TRXs and EGPRS channels/packet data channels (PDCHs) connected to the EDAP the modulation and coding schemes (MCS) used in data transmission.

The MCSs that are used are selected by the PCU based on the radio link quality measurements and link adaptation algorithms. Operator parameters for initial MCSs are also taken into account when selecting an MCS for data transmission. However, Dynamic Abis capacity (EDAP size and available PCU digital signal processor (DSP) resources) also affects MCS usage and because of this, Dynamic Abis and PCU capacity limitations are also taken into account in MCS selection. Dynamic Abis counters monitor EDAP usage and Dynamic Abis limitations. You may have to consider the following actions if the Dynamic Abis counters indicate problems in Dynamic Abis usage:

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•

• • •

increasing EDAP size This may help, for example, in cases where the EDAP counters indicate that temporary block flows (TBFs) are left without requested EDAP resources, EDAP peak usage is 100%, EDAP average usage is high, but EDAP resource limitations are not caused by the lack of PCU resources. decreasing the number of EDGE TRXs and/or EGPRS channels attached to EDAP sharing the load between PCUs, that is moving EDAP(s) and/or GPRS channels from one PCU to another changing the radio network (RNW) configuration and EDAP configuration so that PCU1 dedicates DSP resources for GPRS usage For more information, see section Dynamic Abis pool in a PCU. The last three actions may help, for example, in cases where the EDAP counters indicate that TBFs are left without requested EDAP resources and EDAP resource limitations are caused by the lack of PCU resources.

Note that the EDAP size is the same for both downlink and uplink directions. It is not possible to set different EDAP sizes for downlink and uplink directions.

3.2

Abis L1 frames In Nokia Siemens Networks GPRS/EDGE implementation, PCU frames (based on transcoding and rate adaptation unit (TRAU) frames in circuit switched (CS) traffic) are used to carry the packet switched (PS) traffic over the Abis interface. One PCU frame uses a 16 kbit/s sub-timeslot. There are the following PCU frame types: • •

• • •

PCU data frame is used when TRX is not in EDGE mode and is able to carry CS-1 and CS-2 PCU master data frame is used when TRX is in EDGE mode and carries CS-1 or MCS-1 on its own and CS2...CS-4 and MCS-2...MCS-9 with the help of slave frame(s) PCU slave data frame(s) is used to carry additional data that does not fit in PCU master data frames PCU random access frame is used only in uplink direction to carry access burst information PCU synchronisation frame is used after territory upgrade for synchronising PCU with BTS radio timeslots

Master and slave channels with different coding schemes PCU slave data frames are transferred in the EDAP area and they are always associated with the PCU master data frames transferred in the permanent 16 kbit/s subtimeslots. The following table displays the number of 16 kbit/s sub-timeslots required by different coding schemes.

CS/MCS

Need for master (M) and slave (S) channels

CS-1

M

CS-2

M+S

Table 6

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Coding schemes and need for master and slave channels on Abis.


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CS/MCS

Need for master (M) and slave (S) channels

CS-3

M+S

CS-4

M+S

MCS-1

M

MCS-2

M+S

MCS-3

M+S

MCS-4

M+S

MCS-5

M+S

MCS-6

M+ 2*S

MCS-7

M+ 3*S

MCS-8

M+ 4*S

MCS-9

M+ 4*S

Table 6

Coding schemes and need for master and slave channels on Abis. (Cont.)

The MS may use a lower coding scheme (CS)/modulation and coding scheme (MCS) for uplink data transmission than the CS/MCS for which uplink EDAP resources have been reserved.

3.3

GPRS temporary block flow (TBF) In the BSC, there can be separate territories for GPRS and EGPRS. In GPRS load situations or when a GPRS territory does not exist, it is possible that GPRS traffic (GPRS TBFs) uses EGPRS territory. When a GPRS TBF is via GPRS territory (via a non-EDGE TRX), the CS-2 coding scheme needs only 16 kbit/s from Abis. When a GPRS TBF is via CS-3 and CS-4 capable GPRS territory or via EGPRS territory (via an EDGE TRX), the CS-2 coding scheme needs a 16 kbit/s master Abis channel and one 16 kbit/s slave channel from the EDAP. This is because the EDGE TRX uses different PCU frame formats. Coding Schemes CS-3 and CS-4 always uses EDAP. If a 16 kbit/s slave channel for a GPRS TBF cannot be found, for example, because of EDAP load situations, the coding schemes CS-2 - CS-4 cannot be used. In the uplink direction, the MS's transmission turn may have to be rejected. In the downlink direction, CS-1 may be used instead of CS-2 - CS-4 in certain cases. Applicable counters are updated. For more information, see BSS9006: GPRS System Feature Description and BSS10091: EDGE System Feature Description.

3.4

EGPRS temporary block flow (TBF) The GPRS RR procedures apply to EGPRS as well. The difference is that the EGPRS needs more than 16 kbit/s Abis transmission capacity. The master Abis channel is always linked to a packet data traffic channel (PDTCH). The rest of the required Abis transmission is allocated from the EDAP in 16-64 kbit/s blocks, depending on the coding scheme (MCS) used. The Dynamic Abis resource information and coding scheme is

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transmitted to the BTS by in-band signalling in the PCU master data frame transferred on the master Abis channel. If enough 16 kbit/s slave channels for the coding scheme (MCS) used by the EGPRS TBF cannot be found because of the EDAP load situation, the desired coding scheme cannot be used. In the uplink direction, the MS's transmission turn may have to be rejected. In the downlink direction, a lower coding scheme may be used instead of the desired coding scheme in certain cases. Applicable counters are updated.

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Functionality of Dynamic Abis


4 Functionality of Dynamic Abis 4.1

Dynamic Abis pool management Dynamic Abis is mandatory when EGPRS, Coding Schemes CS-3 and CS-4, Extended Cell for GPRS/EDGE, or Downlink Dual Carrier support in the BSC and in the Packet Control Unit (PCU) is enabled. If Dynamic Abis is used, you must define the pool to be used by the Transceiver (TRX). It must be located on the same Abis external PCM circuit (ET-PCM) as the TRX channel (TRXSIG) and the fixed traffic timeslots. Activating dynamic Abis pool for GPRS/EDGE use You can allocate common transmission resources for EDGE-capable TRXs from the Abis ET-PCM. This common resource is called the Dynamic Abis Pool (DAP) and it is comprised of consecutive Abis ET-PCM timeslots. There can be several DAPs in one Abis ET-PCM but normally only one is needed. The DAP has to be created before the EDGE TRXs that use the DAP are created to the Abis ET-PCM. If you want to change the TRX's usage of Dynamic Abis, a DAP can be attached or detached from the TRX. When a DAP is created, the BSC reserves the corresponding block of timeslots from the Packet Control Unit Pulse Code Modulation (PCUPCM) line. These PCUPCM circuits are needed when DAP circuits are connected to EGPRS use. Following the DAP creation, the BSC updates the database for DAP configuration and then initiate the PCU Hot restart in PCU. During the PCU Hot restart process, the BSC turns off the GPRS traffic from all segments configured to the PCU, releases all EDAP connections from the PCUPCM and then restarts the PCU. After the completion of PCU restart, BSC reconnects all EDAPs again to PCUPCM and turns on the GPRS traffic in all segments configured to the PCU. This short interruption ensures that the BSC can find a block of free timeslots from the PCUPCM, as all EDAPs are consecutively connected in PCUPCM and there are no free timeslots (TSLs) between the EDAPs. PCU Hot restart also ensures the optimized PCU Digital Signal Processor (DSP) resource usage for each EDAP connected to the PCU. If Packet Control Unit (PCU2) Pooling is in use and the DAP is created for a Packet Service Entity (PSE), this kind of interruption in the GPRS traffic takes place in the PCU where the PCU selection algorithm attaches the DAP. For instructions on how to handle dynamic Abis pools in the BSC, see Dynamic Abis Pool Handling. Dynamic Abis pool modification You can change the size of the DAP by adding Abis ET-PCM timeslots to the DAP, or by removing Abis ET-PCM timeslots from the DAP. However, such changes must first be performed on the BTS side. The integrity of the DAP is kept up in the modification operations. This means that new Abis ET-PCM timeslots are added to either upper or lower edge of the DAP and Abis ET-PCM timeslots are removed from either upper or lower edge of the DAP. When new Abis ET-PCM timeslots are added to the DAP, the BSC reserves a corresponding block of timeslots from the PCUPCM. These PCUPCM circuits are needed when DAP circuits are connected to EGPRS use. When the DAP is modified, the BSC updates the database for DAP configuration and then initiate the PCU Hot restart in PCU. During the PCU Hot restart process, the BSC turns off the GPRS traffic from all segments configured to the PCU, releases all EDAP connections from the PCUPCM and then restarts the PCU. After the completion of PCU restart, BSC reconnects all

20

Id:0900d805807410c8 Confidential

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EDAPs again to PCUPCM and turns on the GPRS traffic in all segments configured to the PCU. This short interruption ensures that the BSC can find a block of free timeslots from the PCUPCM, as all EDAPs are consecutively connected in PCUPCM and there are no free timeslots (TSLs) between the EDAPs. PCU Hot restart also ensures the optimized PCU DSP resource usage for each EDAP connected to the PCU. You can also change the controlling PCU of the DAP. When the DAP's PCU is changed, the BSC initiates the hot restart for both the old and new PCU and then upgrades these same traffic channels to packet switched use again. This short interruption ensures optimized PCU DSP resource usage for each DAP connected to those PCUs. If there are one or more TRXs attached to that pool, the packet switched channels of the segments of the TRXs are upgraded to the new PCU. If Packet Control Unit (PCU2) Pooling is in use, the controlling PCU of the DAP can be changed also during PSE reallocation. For operating instructions on how to handle dynamic Abis pools in the BSC, see Dynamic Abis Pool Handling. Dynamic Abis pool deletion You can delete a DAP when there are no TRXs attached to it. The BSC releases all resources reserved for the DAP when it is deleted. Following the DAP deletion, the BSC updates the database for DAP configuration and then initiate the PCU Hot restart in PCU. During the PCU Hot restart process, the BSC turns off the GPRS traffic from all segments configured to the PCU, releases all EDAP connections from the PCUPCM and then restarts the PCU. After the completion of PCU restart, BSC reconnects all EDAPs again to PCUPCM and turns on the GPRS traffic in all segments configured to the PCU. This short interruption ensures that the BSC can find a block of free timeslots from the PCUPCM, as all EDAPs are consecutively connected in PCUPCM and there are no free timeslots (TSLs) between the EDAPs. PCU Hot restart also ensures the optimized PCU DSP resource usage for each EDAP connected to the PCU. For operating instructions on how to handle dynamic Abis pools in the BSC, see Dynamic Abis Pool Handling. Dynamic Abis pool circuit routings Circuit routings are needed for Abis ET-PCM circuits to use Dynamic Abis in the BSC. The BSC makes these routings automatically when a DAP is created, modified, or deleted. The BSC adds Abis ET-PCM circuits to a circuit group called ET-PCM at the same time as the Abis ET-PCM circuits are added to the DAP. This prevents other use of these Abis ET-PCM circuits while they belong to the DAP. The ET-PCM circuit group is shared by all DAP circuits. The BSC also has a specific circuit group for every DAP. These DAP circuit groups are called DAPxxxx, where 'xxxx' indicates the dynamic Abis pool number with four digits. The DAP circuit group is specially designed for Dynamic Abis and it enables hunting and connection methods required by Dynamic Abis. The BSC adds DAP circuits to the DAP circuit group as one-bit wide circuits which are in ascending order according to timeslots and sub-timeslots. The BSC changes the states of these circuits from BA to WO at the same time as the circuits are added to the circuit group.

g

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Removing Dynamic Abis Pool (DAP) routings causes malfunction of the dynamic Abis. Do not change DAP routings manually even if it is possible with MML commands provided by the DX 200 Platform.


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4.2


EGPRS dynamic Abis pool connections The procedure where Dynamic Abis Pool (DAP) circuits are connected to EGPRS use is called the EGPRS dynamic Abis pool (EDAP) upgrade procedure and the procedure where DAP circuits are removed from EGPRS use is called the EDAP downgrade procedure. If GPRS service is provided with an EDGE TRX, EDAP circuits may also be used for GPRS. In the EDAP upgrade and downgrade, the BSC downgrades all packet switched traffic channels from the PCU and then upgrades these same traffic channels to packet switched use again. This short interruption ensures optimized PCU DSP resource usage for each DAP connected to the PCU. EGPRS dynamic Abis pool upgrade The BSC performs the EDAP upgrade procedure, when: 1. 2. 3. 4. 5. 6.

DAP is created new circuits are added to a DAP switchover is made for the Base Station Controller Signalling Unit (BCSU) BCSU is restarted PSE is reallocated (Packet Control Unit (PCU2) Pooling) PCU is restarted

The upgrade procedures for PCU1 and PCU2 are different. •

•

PCU1 There are two phases in the EDAP upgrade procedure for PCU1. In the first phase the BSC makes connections between Abis ET-PCM circuits and packet control unit pulse code modulation (PCUPCM) circuits. In the second phase the BSC attaches DAP circuits to EDAP by informing the PCU1 about mappings between the Abis ETPCM circuits and the PCUPCM circuits. The BSC searches for a continuous block of free timeslots for the EDAP starting from the end of the second PCUPCM and continuing from the end of the first PCUPCM. The search is stopped when a free block is found or the area reserved for the EDAP-dedicated timeslots is reached. The EDAP is then connected to the free place found in the PCUPCM. PCU2 At the start-up phase, the BSC searches for a free place for EDAP from the ETPCMs and PCUPCMs and informs the PCU2 about EDAP count and sizes. After all EDAP resources have been assigned to the PCU2, the BSC sends the EDAP information messages for all EDAPs to the PCU2. These messages contains the ETPCM mappings and suggestions for PCUPCM mappings. When the PCU2 receives the messages, it starts to perform reverse PCUPCM resource allocation algorithm. This algorithm is used by the PCU2 to search for the best place for EDAP from the PCUPCM. The PCU2 can accept or reject the suggested PCUPCM mapping. If the PCU2 accepts the suggestion for EDAP, it responds to the EDAP information message with the same PCUPCM mappings. If the PCU2 finds a better place for EDAP, it responds with the new PCUPCM mappings. When the BSC receives the response, it makes the connection between the ET-PCM and PCUPCM circuits assigned to EDAP.

EGPRS Dynamic Abis Pool downgrade The BSC starts the EDAP downgrade procedure, when: 1. DAP is deleted

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2. 3. 4. 5. 6.

circuits are removed from a DAP switchover is made for the Base Station Controller Signalling Unit (BCSU) BCSU is restarted PSE is reallocated (Packet Control Unit (PCU2) Pooling) PCU is restarted

The downgrade procedures for PCU1 and PCU2 are different: •

•

PCU1 There are two phases in the EDAP downgrade procedure. In the first phase the BSC detaches DAP circuits from the EDAP by informing the PCU about changed mappings between Abis ET-PCM circuits and PCUPCM circuits. In the second phase the BSC releases connections between the Abis ET-PCM circuits and the PCUPCM circuits. PCU2 As in the upgrade procedure, PCU2 also uses the reverse PCUPCM allocation algorithm in the EDAP downgrade. This ensures that the EDAP area in the PCUPCM is as consecutive as possible, because removing PCUPCM timeslots from the beginning of the EDAP could lead to PCUPCM fragmentation.

PCU restart When the PCU is restarted, the BSC releases all EDAP connections related to the PCU. After the PCU becomes operational again, the BSC runs an upgrade procedure for each EDAP controlled by the PCU. The PCU shares the DSP resources optimally for all the EDAPs when the PCU is restarted. BCSU restart When the BCSU is restarted, the BSC releases all EDAP connections related to the BCSU. After the PCU becomes operational again, the BSC runs an upgrade procedure for each EDAP controlled by the PCU. The PCU shares the DSP resources optimally for all the EDAPs when the BCSU is restarted. BCSU switchover If a switchover is made for the BCSU, the BSC releases all EDAP connections related to the old BCSU and then starts an upgrade procedure to recover the EDAP connections in the new BCSU. The PCU shares the DSP resources optimally for all the EDAPs in the BCSU switchover.

4.3

Dynamic Abis pool in a PCU A PCU shares DSP resources optimally for EDAPs when a new dynamic Abis pool is created or an existing pool is deleted or modified. The DSP resources are also shared after PCU restart, BCSU restart or switchover. The PCU shares all (working) DSP cores between all EDAPs connected to the PCU by using a PCU internal algorithm. The PCU DSP resources for an individual EDAP depends on the total number of EDAPs for the PCU and on EDAP-specific properties (EDAP size and attached default EGPRS channel count). Since there are some differences between PCU1 and PCU2 in the DSP allocation for EDAPs algorithm, the description is divided into two parts.

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PCU1 First PCU1 calculates the ideal DSP core count for each EDAP by using equation 1 (which is the same for PCU1 and PCU2). IdealDSPcoreCountForEDAP=

EDAPsizeIn16kbit/sChs + DefaultEGPRSchs 20

Figure 2

Equation 1

where • • •

EDAPsizeIn16kbit/sChs is the EDAP size in 16 kbit/s PCM sub-timeslots (SUBTSLs) DefaultEGPRSchs is the sum of the default EGPRS channels of all the TRXs (BTSs) attached to the EDAP 20 is in the case of PCU1 the channel handling capacity of a single DSP core in 16 kbit/s Abis channels and in the case of PCU2 the channel handling capacity of a half DSP core in 16 kbit/s Abis channels

The result of the ideal DSP core count calculation is rounded up. If the result of the algorithm that calculates the ideal DSP core counts for each EDAP indicates that all available DSP cores are not needed for EDAPs, the PCU1 may dedicate DSP cores also for GPRS channels, that is for the radio timeslots of TRXs not attached to any EDAP. The PCU1 calculates the maximum number of GPRS-dedicated DSP cores by using the equation 2. DSP_need_for_GPRS =

Figure 3

def_gprs_tchs_no_dap ch_capacity_dsp_core

Equation 2

where • •

def_gprs_tchs_no_dap is the number of default GPRS channels connected to a PCU (default channels of the TRXs that are not attached to any EDAP) ch_capacity_dsp_core is the 16 kbit/s channel handling capacity of a single DSP core

The result of the equation 2 is rounded down. For each EDAP, the PCU1 calculates the EDAP DSP load based on the ideal DSP core count for that EDAP. For EDAP DSP load calculation, the PCU is using equation 3 (which is the same for PCU1 and PCU2). DSP_EDAPload=

EDAPsizeIn16kbit/sChs + DefaultEGPRSchs IdealDSPcoreCountForEDAPs

Figure 4

Equation 3

If the sum of ideal DSP core counts for all EDAPs in the PCU1 differs from the available DSP core count, the PCU1 adjusts the DSP resources for each EDAP according to the available DSP core count as follows: •

24

If the sum of ideal DSP core counts for all the EDAPs in PCU1 is less than the available DSP core count, the PCU1 dedicates DSP cores for GPRS as mentioned above, and if there are still unassigned DSP cores after GPRS dedication, the extra DSP cores are allocated to the EDAPs, starting from the EDAP with the highest DSP EDAP load.


DN0431625



•

If the sum of ideal DSP core counts for all the EDAPs in PCU1 is more than the available DSP core count, the PCU1 decreases the DSP core count for the EDAPs that have the lowest DSP EDAP loads until the sum of allocated DSP core counts equals the available DSP cores. However, each EDAP gets at least one DSP core. The PCU1 tries to minimize the relative effect with more than one EDAP with the same DSP EDAP load, as the PCU1 decreases the highest DSP core count first.

Sometimes the parity of DSP indexing limits the optimal sharing of DSP resources to the EDAPs. In such cases, the PCU1 tries to minimize the relative effect. The PCU DSP resources assigned to an EDAP may limit the usage of EDAP resources and PCU capacity for new GPRS channels. Special configurations for algorithm: • • •

If there are no EDAPs defined for a PCU, all DSPs are dedicated for GPRS. If there is only one EDAP for the PCU, one DSP group (even or odd) is for the EDAP and the others are dedicated for GPRS (PCU1 only). If there are 16 EDAPs for the PCU, all DSPs must be used for the EDAPs and there are no GPRS dedicated DSPs.

Only GPRS channels are allowed to GPRS-dedicated DSPs. Both GPRS and EGPRS channels are allowed to a DSP assigned for EDAPs. PCU2-D and PCU2-U You should take the following differences between PCU2-D/U and PCU1 into account when the DSP allocation for EDAPs algorithm is examined: •

• •

PCU2-D/U has only eight DSP cores whereas PCU1 has 16 DSP cores. Based on this difference, a single DSP core of a PCU2-D/U has to handle a maximum of two different EDAPs. This also means that the PCU2-D/U calculates and allocates the halves of the DSP cores. In PCU2-D/U, the DSP is not divided into even and odd DSP groups. This enables a more flexible DSP allocation for EDAPs. PCU2-D/U does not dedicate any DSPs to the GPRS use, that is the GPRS dedicated DSP core concept does not exist in PCU2-D/U.

PCU2-D/U begins the DSP allocation for EDAPs by calculating the DSP count for EDAPs. Equation 4 is used for calculation when a TRX from at least one BTS that has Downlink Dual Carrier activated is attached to the EDAP. (4* edap_size) + edap_tch_count dsp_need_for_edap i = MAX

logical_ch_per_edap_per_dsp 2 * edap_dldc_bts_count + (edap_bts_count - edap_dldc_bts_count) / 2

Figure 5

Equation 4

where • • •

DN0431625

edap_size is the size of EDAP in 64 kbit/s PCM timeslots edap_tch_count is the sum of the default EGPRS channels of all the TRXs (BTSs) attached to the EDAP logical_ch_per_edap_per_dsp is the half of the amount of the channels in single DSP core (one DSP core can handle up to two EDAPs) logical_ch_per_edap_per_dsp = 20


25


• •


edap_dldc_bts_count is the sum of the BTS associates with EDAP (Downlink Dual Carrier enabled) edap_bts_count is the sum of the BTS associates with EDAP

The result of the equation 4 is rounded up. Nokia Siemens Networks recommends that the minimum size of the default territory should be 4 or 13 timeslots. When the PS territory size is 13 (PS territory is accommodated on 2 TRX and territory size is at least 5 on both the TRXs), Downlink Dual Carrier service is immediately available. Equation 5 is used for calculation when the TRXs that are attached to the EDAP are from BTSs that have Downlink Dual Carrier deactivated. dsp_need_for_edap i =

(4* edap_size) + edap_tch_count logical_ch_per_edap_per_dsp

Figure 6

Equation 5

where •

logical_ch_per_edap_per_dsp = 20

The result of the equation 5 is rounded up. Nokia Siemens Networks recommends 4 as the size of the PS territory, if Downlink Dual Carrier is not used. If the result of the ideal DSP count for all EDAPs differs from the available DSP core count, the PCU2-D/U proceeds by calculating the EDAP DSP load for each EDAP by using equation 6. This equation is used when a TRX from at least one BTS that has Downlink Dual Carrier activated is attached to the EDAP. Otherwise the PCU2-D/U allocates the DSPs for EDAP according to DSP need. 100 * ((4* edap_size) + edap_tch_count) dsp_need_for_edap i dsp_payload_for_edap i = MAX

100 * ((4* edap_size) + edap_dldc_bts_count * 13 + (edap_bts_count - edap_dldc_bts_count) * 4) dsp_need_for_edap i

Figure 7

Equation 6

where • • • • •

edap_size is the size of EDAP in 64 kbit/s PCM timeslots edap_tch_count is the sum of the default EGPRS channels of all the TRXs (BTSs) attached to the EDAP dsp_need_for_edaps is the result of the equation 4 edap_dldc_bts_count is the sum of the BTS associates with EDAP (Downlink Dual Carrier enabled) edap_bts_count is the sum of the BTS associates with EDAP

The result of the equation 6 is rounded up. Nokia Siemens Networks recommends at least 4 as the size of the PS territory. When the PS territory size is 13 (PS territory is accommodated on 2 TRX and territory size is at least 5 on both the TRXs), Downlink Dual Carrier service is immediately available. Equation 7 is used for calculation when the TRXs that are attached to the EDAP are from BTSs that have Downlink Dual Carrier deactivated.

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dsp_payload_for_edap i =

100 * ((4* edap_size) + edap_tch_count) dsp_need_for_edap i

Figure 8

Equation 7

The result of the equation 7 is rounded up. Nokia Siemens Networks recommends 4 as the size of the PS territory, if Downlink Dual Carrier is not used. After PCU2-D/U has calculated EDAP DSP load for each EDAP, it adjusts the DSP resources for each EDAP according to the available DSP core count as follows: •

•

If the sum of the ideal DSP core count for all EDAPs in the PCU2-D/U is less than the available halves of the DSP cores, the PCU2-D/U allocates the extra halves of the DSP cores for EDAPs, starting from the EDAP with the highest DSP EDAP load. If the sum of the ideal DSP core count for all EDAPs in the PCU2-D/U is more than the count of the available halves of the DSP cores, the PCU2-D/U decreases the DSP core count for the EDAPs that have the lowest DSP EDAP loads until the sum of allocated DSP core counts equals the available DSP cores. However, each EDAP gets at least one half of the DSP core. The PCU2-D/U tries to minimize the relative effect with more than one EDAP with the same DSP EDAP load, as the PCU2-D/U decreases the highest DSP core count first.

Special configurations for the algorithm: • •

If there are no EDAPs defined for a PCU, none of the DSPs are allocated to EDAPs. If there are 16 EDAPs defined for a PCU, all EDAPs have only one half of a DSP core.

You should note that there is no fixed boundary for EDAPs in the DSP resources when a single DSP core handles two different EDAPs at a time. PCU2-E PCU2- E shares DSP resources optimally for EDAPs when a new dynamic Abis pool is created or an existing pool is deleted or modified. The DSP resources are also shared after a PCU restart, BCSU restart or a switchover. However, the DSP resource allocation for EDAPs with PCU2-E is different from other PCU variants, because with PCU2E the DSPs are not allocated to EDAPs but the EDAPs are allocated to the DSPs. This difference originates from the fact that in PCU2-E one EDAP cannot be shared between multiple DSPs but one DSP can have multiple EDAPs to handle. At the initial stage of the DSP allocation, the PCU2-E calculates a payload value for each EDAP. This payload value indicates how much the EDAP increases the payload for the DSP. The used equation for calculation depends on whether Downlink Dual Carrier is enabled in some BTS that is attached with the EDAP. For more information, see BSS21228: Downlink Dual Carrier Feature Description. Equation 8 is used if the dldc_bts_range_count field is not zero for the DAP (Downlink Dual Carrier enabled): 100 * ((4* edap_size) + edap_tch_count) dsp_payload_for_edap i = MAX

Figure 9

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100 * ((4* edap_size) + edap_dldc_bts_count * 13 + (edap_bts_count - edap_dldc_bts_count) * 4)

Equation 8


27



where • • • •

edap_size is the size of EDAP in 64 kbit/s PCM timeslots edap_tch_count is the sum of the default EGPRS channels of all the TRXs (BTSs) attached to the EDAP edap_dldc_bts_count is the sum of the BTS attached with the EDAP (Downlink Dual Carrier enabled) edap_bts_count is the sum of the BTS attached with the EDAP

Nokia Siemens Networks recommends that the minimum size of the default territory should be 4 or 13 timeslots. When the PS territory size is 13 (PS territory is accommodated on 2 TRX and territory size is at least 5 on both the TRXs), Downlink Dual Carrier service is immediately available. Equation 9 is used if the dldc_bts_range_count field is zero for the EDAP (Downlink Dual Carrier disabled): dsp_payload_for_edap i = 100 * ((4* edap_size) + edap_tch_count)

Figure 10

Equation 9

where • •

edap_size is the size of the EDAP in 64 kbit/s PCM timeslots edap_tch_count is the sum of the default EGPRS channels of all the TRXs (BTSs) attached to the EDAP

Nokia Siemens Networks recommends 4 as the size of the PS territory, if Downlink Dual Carrier is not used. After the PCU2-E has calculated the payload for every EDAP, it begins to allocate the EDAPs to DSPs. The target is to allocate all EDAPs to DSPs so that the sum of payload that one DSP carries is even for all DSPs. Special configuration for the algorithm: •

28

When a PCU2-E has less than six EDAPs configured, the DSPs that have no EDAP are dedicated to the GPRS use. Only GPRS channels can be connected to the GPRS dedicated DSP.


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Nokia - Dynamic Abis Pool

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