ZTE - Fast Return to LTE

Fast Return to LTE Feature Guide

Fast Return to LTE

Fast Return to LTE Version V1.00

Date

2015/08/03

Author

Feng Hong

Reviewer

Wang Juntao

Notes

Compared with UR13, add section 3.2, 3.3 and 3.6, update section 6.2~6.4 Deleted reserved parameter GREspare1

V1.10

2015/11/19

Liu Fulei

Wang Juntao

2 bit14, added URncInfo.csmtIdentifySw ch 1.

Chapter 3.1.1: Add “CSFB Identified by RRC Connection Requests Is Categorized as CS Service ”

V1.20

2016/02/19

Liu Fulei

Wang Juntao

2.

Add “3.1.7 Special Scenario that C SFB Users are Forbidden to Fast

Return to LTE”. 3.

Add 3.1.8 Supplementary Services Forbidden to Fast Return to LTE

© 2016 ZTE Corporation. All rights reserved. ZTE CONFIDENTIAL: This document contains proprietary information of ZTE and is not to be disclosed or used without the prior written permission of ZTE. Due to update and improvement of ZTE products and technologies, information in this document is subjected to change without notice.

ZTE Confidential Proprietary

1

Fast Return to LTE

Fast Return to LTE Version V1.00

Date

2015/08/03

Author

Feng Hong

Reviewer

Wang Juntao

Notes

Compared with UR13, add section 3.2, 3.3 and 3.6, update section 6.2~6.4 Deleted reserved parameter GREspare1

V1.10

2015/11/19

Liu Fulei

Wang Juntao

2 bit14, added URncInfo.csmtIdentifySw ch 1.

Chapter 3.1.1: Add “CSFB Identified by RRC Connection Requests Is Categorized as CS Service ”

V1.20

2016/02/19

Liu Fulei

Wang Juntao

2.

Add “3.1.7 Special Scenario that C SFB Users are Forbidden to Fast

Return to LTE”. 3.

Add 3.1.8 Supplementary Services Forbidden to Fast Return to LTE

© 2016 ZTE Corporation. All rights reserved. ZTE CONFIDENTIAL: This document contains proprietary information of ZTE and is not to be disclosed or used without the prior written permission of ZTE. Due to update and improvement of ZTE products and technologies, information in this document is subjected to change without notice.


1

Fast Return to LTE

TABLE OF CONTENTS 1

Feature Attribute ............................................................................................... 6

2 2.1 2.1.1

Overview Overview ................................. ................................................. ................................. .................................. .................................. ......................... ........ 6 Feature Introduction ............................................................................................. 6 ZWF21-03-111 Fast Return to LTE ...................................................................... 6

2.1.2 2.1.3 2.2 2.3

ZWF21-03-112 Packet Packet Service Fast Return to LTE for Inactive Mode ................. ................ . 7 ZWF21-03-113 Packet Service Fast Return to LTE for Active Mode .................. ........ ............ .. 8 License License Control Control ................................. ................................................. .................................. .................................. ................................. ................. 8 Correlation With Other Features .......................................................................... 8

3 3.1 3.1.1 3.1.2 3.1.3 3.1.4

Technical Description ....................................................................................... 9 ZWF21-03-111 Fast Return to LTE ...................................................................... 9 Identification of of CSFB Users and SRVCC Users.................. ......... ................... ................... .................. ........... .. 10 EUTRAN Supporting Judgement ....................................................................... 11 Fast Return in PS Handover Mode .................................................................... 11 Fast Return in Redirection Mode based on Measurement .................. ......... ................... ................ ...... 15

3.1.5 3.1.6 3.1.7 3.1.8 3.2

Fast Return in Redirection Mode without without Measurement .................. ......... .................. ................... .......... 19 Fast Return Strategy of IUR ............................................................................... 26 Special Scenario that CSFB Users are Forbidden to Fast Return to LTE ........... ......... .. 27 Supplementary Supplementary Services Forbidden to Fast Return to LTE ................... ......... ................... .............. ..... 27 ZWF21-03-112 Packet Packet Service Fast Return to LTE for Inactive Mode ............... 28

3.2.1 3.2.2 3.3 3.3.1 3.3.2

Strategy without Dedicated Priority .................................................................... Strategy with Dedicated Priority ......................................................................... ZWF21-03-113 Packet Service Fast Return to LTE for Active Mode .................. ........ .......... Strategy without Dedicated Priority .................................................................... Strategy with Dedicated Priority .........................................................................

3.4 3.4.1 3.4.2 3.5 3.5.1 3.5.2

Penalty strategy ................................................................................................. 32 Penalty Mechanism Principle ............................................................................. 32 Penalty on UE Flag ............................................................................................ 33 EUTRAN Frequency Priority .............................................................................. 33 Frequency Priority Configuration ........................................................................ 33 Frequency Priority Strategy in Handover/Redirection Handover/Redirection ................... ......... ................... .................. ............. .... 34

3.5.3 3.6

Relationship with Dedicated Priority ................................................................... 35 Optimization of Redirection to LTE Strategy for Only PS Signaling .................. ......... ........... .. 35

4 4.1

Paramete Parameters rs................................ ................................................. .................................. .................................. .................................. .................... ... 36 ZWF21-03-111 Fast Return to LTE .................................................................... 36

4.2 4.3 4.4

ZWF21-03-112 Packet Packet Service Fast Return to LTE for Inactive Mode ............... 42 ZWF21-03-113 Packet Service Fast Return to LTE f or Active Mode .................. ........ .......... 43 EUTRAN Frequency Priority .............................................................................. 44


28 28 29 29 30

2

Fast Return to LTE

5 5.1 5.1.1 5.1.2

Related Counters and Alarms ........................................................................ 47 Related Counters ............................................................................................... 47 ZWF21-03-111 Fast Return to LTE .................................................................... 47 ZWF21-03-112 Packet Service Fast Return to LTE for Inactive Mode ............... 47

5.1.3 5.2

ZWF21-03-113 Packet Service Fast Return to LTE for Active Mode .................. 48 Related Alarms .................................................................................................. 48

6 6.1 6.2 6.2.1

Engineering Guide .......................................................................................... 48 Application Scenario .......................................................................................... 48 Feature Activation Procedure ............................................................................. 49 Fast Return to LTE............................................................................................. 49

6.2.2 6.2.3 6.2.4 6.3

Packet Service Fast Return to LTE for Inactive Mode ........................................ 59 Packet Service Fast Return to LTE for Active Mode ........................................... 60 EUTRAN Frequency Priority .............................................................................. 61 Feature Validation Procedure ............................................................................ 63

6.3.1 6.3.2 6.3.3 6.3.4 6.4 6.5

Fast Return to LTE for CSFB ............................................................................. 63 Pack Service Fast Return to LTE for Inactive Mode ........................................... 64 Packet Service Fast Return to LTE for Active Mode ........................................... 65 Fast Return to LTE with Dedicated Priority for CSFB ......................................... 65 Feature Deactivation Procedure......................................................................... 66 Impact on the Network ....................................................................................... 67

6.5.1 6.5.2 6.5.3

ZWF21-03-111 Fast Return to LTE .................................................................... 67 ZWF21-03-112 Packet Service Fast Return to LTE for Inactive Mode ............... 67 ZWF21-03-113 Packet Service Fast Return to LTE for Active Mode .................. 68

7

Abbreviation .................................................................................................... 68

8

Reference Document....................................................................................... 69


3

Fast Return to LTE

FIGURES Figure 6-1

Parameters configuration interface 1 ................................................................49

Figure 6-2


Figure 6-3


Figure 6-4


Figure 6-5


Figure 6-6


Figure 6-7


Figure 6-8


Figure 6-9


Figure 6-10

Parameters configuration interface 10 ............................................................54

Figure 6-11


Figure 6-12


Figure 6-13


Figure 6-14


Figure 6-15


Figure 6-16


Figure 6-17


Figure 6-18


Figure 6-19


Figure 6-20


Figure 6-21


TABLES Table 2-1

License Control List ............................................................................................ 8

Table 5-1

Counter List .......................................................................................................47

Table 6-1

Feature Validation Procedure 1..........................................................................63

Table 6-2



4

Fast Return to LTE

Table 6-3


Table 6-4


Table 6-5

RNC Parameter List ...........................................................................................66


5

Fast Return to LTE

1

Feature Attribute BSC/RNC version: [ZXWR RNC V3.14.10.14/ZXUR 9000 V4.14.10.14] BTS/Node B version: [ZXSDR V4.14.10] Attribute: [Optional] Involved NEs: NE Name

Related or Not

MS/UE

-

BTS/Node B

-

BSC/RNC

√

iTC

-

MSC

-

MGW

-

SGSN

-

GGSN

-

HLR

-

Special Requirement

“√”: involved “-”: not involved

2

Overview

2.1

Feature Introduction

2.1.1

ZWF21-03-111 Fast Return to LTE The LTE network without IMS element cannot provide voice service for the UE. The UE needs to establish the voice service after being transferred to the 3G network through the CSFB method. During the voice service release, if there is no any other service, the UE returns to the idle state after releasing the RRC connection, reads the UTRAN broadcast information, and probably needs another location area update. After that, the UE


6

Fast Return to LTE

performs cell selection/reselection estimation, and returns to the LTE network under the control of the E-UTRAN cell reselection parameter. ZTE RAN fill s the “Redirect info” information in the RRC release message of the voice service, and the UE searches the LTE neighboring cell of the specific frequency without reading the UTRAN cell broadcast and location area update procedures, reducing the time cost by the UE to return to the LTE network. The data service of a UMTS/LTE dual mode terminal is possibly kept in the UMTS network. For example, PS data is ongoing after CS call is released for a CS fallback user, or a data service is transferred from LTE to UMTS at th e edge of LTE coverage. The data service is kept in the UMTS network in a long period when the data traffic is always active. This is not acceptable by both the operator and the subscriber. LTE network is new deployed and taken as a more advanced network. The operator prefers to utilize LTE network as much as possible. And the subscriber also wishes to experience service in it. To avoid the subscriber staying in UMTS network f or a long period, ZTE RAN triggers the subscriber to switch to LTE network when it is in the coverage of E-UTRAN cell.

2.1.2

ZWF21-03-112 Packet Service Fast Return to LTE for Inactive Mode If a 4G subscriber initials only PS data in 3G, when the data transmission is inactive, normally 3G RAN switches it to Cell PCH/URA PCH or IDLE. In the control of cell reselection parameters broadcast in 3G cell, the subscriber camps in LTE finally. However, some procedure such as reading the whole 3G cell system information, search LTE cells one by one indicated in SIB19 of 3G cell are required. With the feature, 3G RAN releases RRC connection of the subscriber and redirects it to LTE. It makes the terminal searching LTE target directly. It accelerates the subscriber back to LTE.

If the feature “ZWF27-02-002 User Dedicated Frequency Priority” is switched off, 3G RAN redirects or hand over the UE to LTE according to neighbor relation. Otherwise the UE is redirected or handover to LTE only when LTE is the highest priority according to the mapping of SPID to dedicated frequency priority. And the LTE frequency is provided to UE according the priority in dedicated frequency priority configuration.


7

Fast Return to LTE

2.1.3

ZWF21-03-113 Packet Service Fast Return to LTE for Active Mode If a 4G subscriber establish PS data in 3G, he may stay in 3G in a long period when watching video or serving as a Wifi hotspot. With the feature, ZTE RAN identifies such subscriber and redirects him/her to LTE network.

If the feature “ZWF27-02-002 User De dicated Frequency Priority” is switched off, 3G RAN redirects or hand over the UE to LTE according to neighbor relation. Otherwise the UE is redirected or handover to LTE only when LTE is the highest priority according to the mapping of SPID to dedicated frequency priority. And the LTE frequency is provided to UE according the priority in dedicated frequency priority configuration.

2.2

License Control This feature is under license control. It must have authorization on the OMC or LMT before the configuration of the feature.

Table 2-1

License Control List

Feature ID

ZWF21-03-111

ZWF21-03-112

Feature Name

Service

Return

to

LTE

ZWF21-03-113

Service

Return

to

Active Mode

2.3

LTE

rol Item

NE

LTE

Fast for

Inactive Mode Packet

Configured

Fast Return to

Fast Return to LTE Packet

License Cont

Fast for

Fast Return to LTE

Fast Return to LTE

Unit

RNC

RNC

RNC

RNC

RNC

RNC

Correlation With Other Features 1. Required Features ZWF21-03-101 CS Fallback from LTE Support ZWF21-03-120 SR-VCC


8

Fast Return to LTE

2. Mutually Exclusive Features None 3. Affected Features None

3

Technical Description

3.1

ZWF21-03-111 Fast Return to LTE When the UTRAN and EUTRAN are jointly deployed, the UE in EUTRAN can be handed over to the UTRAN through the CSFB or SRVCC. To provide these UEs better service experience, the UTRAN transfers these UEs to the EUTRAN through PS handover or redirection. The application scenario is described as follows: 

The UE in the LTE cell initiates a voice call. Due to CSFB, the UE can be handed over from LTE to UMTS. When the CS call of the UE is released in the UMTS network, the RNC performs the fast return to LTE strategy.



The UE establishes PS service in EUTRAN, and initiates a CS call. The UE is handed over from LTE to UMTS due to CSFB. When the CS call of the UE is released in UMTS, the RNC performs the fast return to LTE strategy.



The UE establishes a VoLTE service in EUTRAN. If the signaling quality of the UE is getting worse, the SRVCC from LTE to UMTS is triggered. When the CS call of the UE is released in UMTS, the RNC performs the fast return to LTE strategy.



The UE establishes a VoLTE service and a PS service in EUTRAN. If the signaling quality of the UE is getting worse, the SRVCC from LTE to UMTS is triggered. When the CS call of the UE is released in UMTS, the RNC performs the fast return to LTE strategy.


9

Fast Return to LTE



When the PS service channel switching from CELL_DCH to CELL_FACH for a UE is triggered in UMTS, the RNC performs the fast return to LTE strategy.

This document describes the fast return to LTE strategy that is applicable to t he following scenarios:

3.1.1



Fast return in PS Handover mode



Fast return in redirection mode based on measurement



Fast return in redirection mode without measurement

Identification of CSFB Users and SRVCC Users If any of the following conditions is satisfied, the UE shall be identified as a CSFB UE. 1.

The “CSFB Indication” is carried in the RRC Connection Request message, or

2.

Neither the “CSFB Indication” nor the “Pre-redirection info”(3GPP R9.4) is carried in the RRC Connection Request message, the time difference between the RRC Connection Request message and first RAB Assignment Request message for a CS service is not greater than URncInfo.csfbIdentifyTimer , or

3.

The “CSFB Information” is carried in “Source RNC to Target RNC Transparent

Container” of the Relocation Request message , or 4.

The RNC receives a IU RELEASE COMMAND message with IE “End of CSFB” (3GPP R10.4), or

5.

“CSMO” is carried in the NAS message “ CM SERVICE REQUEST” analyzed by the RNC, or

6.

“CSMO” is carried in the NAS message “ LOCATION UPDATING REQUEST” analyzed by the RNC, or

7.

“CSMT” is carried in the NAS message “LOCATION UPDATING REQUEST” analyzed by the RNC.


10

Fast Return to LTE

If CSFB is identified by RRC Connection Requests and the Establishment Cause is

not any of “Originating Conversational Call , Terminating Conversational Call,

Emergency Call” , then the Establishment Cause of CSFB is modified as Originating Conversational Call.

If the following conditions are satisfied, the UE shall be identified as a SRVCC UE.

3.1.2

1.

ULogicalRnc.rncSrvccSw is set to “On”;

2.

The UE is relocated from the EUTRAN to UMTS and includes a CS service.

EUTRAN Supporting Judgement EUTRAN service handover IE is not “ Handover to EUTRAN shall not be performed ”,

1.

it indicates that handover or redirection to LTE is allowed. 2.

3.1.2.1

UE Capability supports LTE.

Identification of UE Capability and Special Handling For the relocation from other RNCs to the l ocal RNC, UE capability is only acquired in the way that RNC sends the UE CAPABILIT Y ENQUIRY message. When the RNC identifies the CSFB Information IE in the Relocation Request message, and does not acquire UE capability, if the switch URncInfo.ueLteCapJugSw is “1: On”, the UE is taken for supporting

LTE

(Support

of

E-UTRA

FDD/TDD).

Otherwise,

the

switch

URncInfo.ueLteCapJugSw is “0: Off”, the UE is not taken for supporting LTE.

3.1.3

Fast Return in PS Handover Mode Whether enabling the dedicated priority functionality affects the judgment on triggering fast return to LTE. See the details in the following chapters.

3.1.3.1

Strategy without Dedicated Priority



CSFB


11

Fast Return to LTE

1.

The process of the PS Service when a CS service is released for Multi-RAB Service After the UE is handed over from EUTRAN to UTRAN due to CSFB, if the CS service is released for Multi-RAB, and if the following conditions are met, the

EUTRAN’s compressed mode is activated, and the inter -RAT measurement for the EUTRAN is configured. After the measurement reports are received, the PS handover procedure is performed and the UE is handed over to EUTRAN. i.

The EUTRAN neighboring cells exist.

ii.

The UE supports the PS handover from UMTS to EUTRAN.

iii.

URncInfo.cheEutraCapiSw is “Off”. Or URncInfo.cheEutraCapiSw is “On” and the UE E-UTRA Capability IE is obtained.

iv.

URncFunction.fastRetEUtranSwch is “On”.

v.

UCelInfoFDD.csfbMulSrv2LteSw

is

“Handover

judgment

Based

on

Measurement”. vi.

URncInfo.csfbPsHo2LteMode is “PS handover”.



SRVCC

1.

The process of the PS Service when a CS service is released for Multi-RAB Service After the UE is handed over from EUTRAN to UTRAN due to SRVCC, if the CS service is released for Multi-RAB, and if the following conditions are satisfied, the

EUTRAN’s compressed mode is activated, and the inter -RAT measurement for the EUTRAN is configured. After measurement reports are received, the PS handover procedure is performed and the UE is handed over to the EUTRAN. i.


ii.


iii.



12

Fast Return to LTE

iv.


v.

UCelInfoFDD.srvccMulSrv2LteSw

is “Handover judgment Based on

Measurement”. vi.

URncInfo.srvccPsHo2LteMode is “PS handover”.

Note: 1.

UCelInfoFDD.simCompUserNum is used to control the number of users activating compressed mode for fast return to EUTRAN based on measurement, to avoid affecting system performance. If the current number of the UEs

to be activated

with compressed mode due to fast return to EUTRAN in the cell is not less than UCelInfoFDD.simCompUserNum, the compressed mode for the UEs due to fast return to EUTAN will not be activated. Otherwise, the compressed mode for the UEs due to fast return to EUTAN will be activated. 2.

If the compressed mode is activated due to fast return to EUTRAN, the timer URncInfo.psHoLteMeasTimer is enabled. When the timer expires, if Event (3C) of the UE is not reported, the RNC determines whether the compressed mode of the UE is deactivated based on the current signal quality.

3.1.3.2

Strategy with Dedicated Priority When

user

dedicated

frequency

priority(ULogicalRnc.dePriRncSwch

and

UExtCelInfoFDD.dePriSwch) is on, the related strategy is as follows: 

CSFB

1.

The process of the PS Service when a CS service is released for Multi-RAB Service After the UE is handed over from EUTRAN to UTRAN due to CSFB, if the CS service is released for Multi-RAB, and if the following conditions are met, the

EUTRAN’s compressed mode is activated, and the inter -RAT measurement for the EUTRAN is configured. After the measurement reports are received, the PS handover procedure is performed and the UE is handed over to EUTRAN. i.

The UE supporting EUTRAN neighboring cells exist.


13

Fast Return to LTE

ii.


iii.


iv.


v.


is

“Handover

judgment

Based

on

Measurement”. vi.

URncInfo.csfbPsHo2LteMode is “PS handover”.

vii.

The highest priority of EUTRAN frequencies is higher than the highest priority of UTRAN frequencies. The frequency and priority acquires from MO_UDePri,

and the detailed strategy and parameters refer to “ZTE UMTS User Dedicated Frequency Priority Feature Guide”.



SRVCC

1.

The process of the PS Service when a CS service is released for Multi-RAB Service After the UE is handed over from EUTRAN to UTRAN due to SRVCC, if the CS service is released for Multi-RAB, and if the following conditions are satisfied, the

EUTRAN’s compressed mode is activated, and the inter -RAT measurement for the EUTRAN is configured. After measurement reports are received, the PS handover procedure is performed and the UE is handed over to the EUTRAN. i.


ii.


iii.


iv.


v.


is

“Handover

judgment

Based

on

Measurement”.


14

Fast Return to LTE

vi.

URncInfo.srvccPsHo2LteMode is “PS handover”.

vii.



3.1.4

Fast Return in Redirection Mode based on Measurement Whether enabling the dedicated priority functionality affects the judgment on triggering fast return to LTE and the frequency filling criteria in IE “Redirection Info”. See the details in the following chapters.

3.1.4.1

Strategy without Dedicated Priority 

CSFB

1.

The process of the PS Service when a CS service is released for Multi-RAB Service After the UE is handed over from EUTRAN to UTRAN due to CSFB, if the CS service is released for Multi-RAB, and if the following conditions are satisfied, the EUTRAN compressed mode is activated, and the inter-RAT measurement for the EUTRAN is configured. After the measurement reports are received, the Redirection procedure is performed, and downlink central frequency information of the EUTRAN cell whose quality meets inter-RAT measurement event is filled in the Redirection info of the RRC Connection Release message. Then the UE is redirected to EUTRAN. i.


ii.


iii.


is

“Handover

judgment

Based

on

Measurement”. iv.

URncInfo.csfbPsHo2LteMode is “Redirection”, the UE supports the EUTRAN measurement; or URncInfo.csfbPsHo2LteMode is “PS handover”, the UE does


15

Fast Return to LTE

not support the PS handover from UMTS to EUTRAN but supports the EUTRAN measurement.



SRVCC

1.

The process of the PS Service when the CS service is released for Multi-RAB Service After the UE is handed over from EUTRAN to UTRAN due to SRVCC, if the C S service is released for Multi-RAB, and if the following conditions are satisfied, the RNC activates the EUTRAN compressed mode, and configures the inter-RAT measurement. After the measurement reports are received, the RNC performs the Redirection procedure, and fills downlink central frequency information of the EUTRAN cell whose quality meets inter-RAT measurement event in the Redirection info of the RRC Connection Release message. Then the UE is redirected to EUTRAN. i.

The EUTRAN neighboring cells exist;

ii.

URncFunction.fastRetEUtranSwch is “On”;

iii.



Measurement”; iv.

URncInfo.srvccPsHo2LteMode is “Redirection”, the UE supports the EUTRAN measurement; or URncInfo.srvccPsHo2LteMode is “PS handover”, the UE does not support PS handover to EUTRAN but the EUTRAN measurement.

Note: 1.

UCelInfoFDD.simCompUserNum is used to control the number of users to be activated with compressed mode for fast return to EUTRAN based on measurement to avoid affecting system performance. If the current number of the UEs who has been activated compressed mode due to fast return to EUTRAN is not less than UCelInfoFDD.simCompUserNum, the compressed mode for the UEs due to fast return to EUTAN will not be activated. Otherwise, the compressed mode for the UEs due to fast return to EUTAN will be activated.


16

Fast Return to LTE

2.

If the compressed mode is activated due to fast return to EUTRAN, the timer URncInfo.psHoLteMeasTimer is is initialized. When the timer expires, if Event (3C) of the UE is not reported, the RNC will judge whether the compressed mode of the UE is deactivated based on the current signal quality.

3.1.4.2


user

dedicated

frequency

priority (ULogicalRnc.dePriRncSwch priority(

and

UExtCelInfoFDD.dePriSwch)) is on, the related strategy is as follows: UExtCelInfoFDD.dePriSwch 

CSFB

1.

The process of the PS Service when a CS service is released for Multi-RAB Service After the UE is handed over from EUTRAN to UTRAN due to CSFB, if the CS service is released for Multi-RAB, and if the following conditions are satisfied, the EUTRAN compressed mode is activated, and the inter-RAT measurement for the EUTRAN is configured. After the measurement reports are received, the Redirection procedure is performed, and frequency satisfying the conditions is filled in the Redirection info of the RRC Connection Release message. Then the UE is redirected to EUTRAN. i.


ii.


iii.


is

“Handover

judgment

Based

on

Measurement”. iv.

URncInfo.csfbPsHo2LteMode is “Redirection”, the UE supports the EUTRAN measurement; or URncInfo.csfbPsHo2LteMode is “PS handover”, the UE does not support the PS handover from UMTS to EUTRAN but supports the EUTRAN measurement.

v.




17

Fast Return to LTE



SRVCC

1.

The process of the PS Service when the CS service is released for Multi-RAB Service After the UE is handed over from EUTRAN to UTRAN due to SRVCC, if the CS service is released for Multi-RAB, and if the following conditions are satisfied, the RNC activates the EUTRAN compressed mode, and configures the inter-RAT measurement. After the measurement reports are received, the RNC performs the Redirection procedure, and fills downlink central frequency information of the EUTRAN cell who meets “Redirection Condition” in the Redirection info of the RRC Connection Release message. Then the UE is redirected to EUTRAN. i.


ii.

URncFunction.fastRetEUtranSwch is “On”;

iii.



Measurement”; iv.

URncInfo.srvccPsHo2LteMode is “Redirection”, the UE supports the EUTRAN measurement; or URncInfo.srvccPsHo2LteMode is “PS handover”, the UE does not support PS handover to EUTRAN but the EUTRAN measurement.

v.


and the detailed strategy and parameters refer to “ZTE UMTS User Dedicated Frequency Priority Feature Guide”. Note: Definition of frequency satisfying the conditions: Frequency set1 consists of UE reporting EUTRAN frequency, and frequency set2 consists of EUTRAN frequency configured in MO_UDePri. If frequency set1 and set2 have common frequency, then it adds this frequency to frequency set3. And the RNC fills the frequency in set3 with highest dedicated priority in


18

Fast Return to LTE

RRC Connection Release. If several frequency have the same highest dedicated priority, then RNC fills 4 FDD frequencies and 4 TDD frequencies at most.

3.1.5

Fast Return in Redirection Mode without Measurement Whether enabling the dedicated priority functionality affects the judgment on triggering fast return to LTE and the frequency filling criteria in IE “Redirection Info”. See the details in the following chapters.

3.1.5.1

Strategy without Dedicated Priority 

CSFB

1.

The process of the PS Service when the CS service is released for Multi-RAB Service After the UE is handed over from EUTRAN to UTRAN due to CSFB, if the CS service is released for Multi-RAB, and if the following conditions are satisfied, the EUTRAN cell downlink central frequency information is filled in the Redirection info of the RRC Connection Release message. Then the UE is redirected to EUTRAN. i.


ii.


iii.


is

“Handover

judgment

Based

on

Measurement”. The UE neither supports the PS handover from UMTS to EUTRAN nor the EUTRAN measurement, but only supports EUTRAN (Support

of

E-UTRA

FDD/TDD).

Alternatively,

UCelInfoFDD.csfbMulSrv2LteSw is “Redirection without Measurement”, the UE supports EUTRAN (Support of E-UTRA FDD/TDD). 2.

The process of only CS Service After the UE is handed over from EUTRAN to UTRAN due to CSFB, if the CS service is released for Single-RAB, and if the following conditions are satisfied, the EUTRAN cell downlink central frequency information is filled in the Redirection info of the RRC Connection Release message. Then the UE is redirected to EUTRAN.


19

Fast Return to LTE

3.

i.


ii.

The UE supports the EUTRAN (Support of E-UTRA FDD/TDD).

iii.


iv.

UtranCellFDD.csfbCsRel2LteSw is “On”.

CS Service Establishment Failure

After the UE is handed over from EUTRAN to UTRAN due to CSFB, if the IU Release Command message of CS domain is received, and if the following conditions are satisfied, the EUTRAN cell downlink central frequency information is filled in the Redirection info of the RRC Connection Release message. Then the UE is redirected to EUTRAN.

-

PS services exist i.


ii.


iii.


is

“Handover

Judgment

Based

on


of

E-UTRA

FDD/TDD).

Alternatively,

UCelInfoFDD.csfbMulSrv2LteSw is “Redirection without Measurement”, the UE supports EUTRAN (Support of E-UTRA FDD/TDD).

-

PS services do not exist i.


ii.


iii.


iv.



20

Fast Return to LTE



SRVCC

1.

The process of the PS Service when the CS service is released for Multi-RAB Service After the UE is handed over from EUTRAN to UTRAN due to SRVCC, if the CS service is released for Multi-RAB, and if the following conditions are satisfied, the EUTRAN cell downlink central frequency information is filled in the Redirection info of the RRC Connection Release message. Then the UE is redirected to EUTRAN. i.


ii.


iii.


is

“Handover

judgment

Based

on

Measurement”, and the UE neither supports PS handovers to EUTRAN nor the EUTRAN measurement, and the UE only supports EUTRAN (Support of E-UTRA FDD/TDD). OR UCelInfoFDD.srvccMulSrv2LteSw is “Redirection

without Measurement”, and the UE supports EUTRAN (Support of E-UTRA FDD/TDD). 2.

The process of only CS Service After the UE is handed over from EUTRAN to UTRAN due to SRVCC, if the CS service is released for Single-RAB, and if the following conditions are satisfied, the

EUTRAN cell’s downlink central frequency information is filled in the Redirection info of the RRC Connection Release message. Then the UE is redirected to EUTRAN.



i.


ii.

The UE supports EUTRAN (Support of E-UTRA FDD/TDD).

iii.


iv.

UtranCellFDD.srvccCsRel2LteSw is “On”.

The process of channel switching from CELL_DCH to CELL_FACH


21

Fast Return to LTE

If the PS service channel switching from CELL_DCH to CELL_FACH is triggered in UMTS, and if the following conditions are satisfied, the EUTRAN cell downlink central frequency information is filled in the Redirection info of the RRC Connection Release message. Then the UE is redirected to EUTRAN. i.


ii.


iii.


iv.

UCelInfoFDD.dch2FachRetLteSw is “On”.

Note: 1.

When the condition of fast return to LTE is fulfilled, the RNC acquires UE supporting frequencies from EUTRAN neighboring relation, then fills 4 FDD and 4 TDD frequencies in RRC Connection Release.

3.1.5.2


user

dedicated

frequency

priority

(ULogicalRnc.dePriRncSwch

and

UExtCelInfoFDD.dePriSwch) is on, the related strategy is as follows: 

CSFB

1.

The process of the PS Service when the CS service is released for Multi-RAB Service After the UE is handed over from EUTRAN to UTRAN due to CSFB, if the CS service is released for Multi-RAB, and if the following conditions are satisfied, the EUTRAN cell downlink central frequency information is filled in the Redirection info of the RRC Connection Release message. Then the UE is redirected to EUTRAN. i.


ii.



22

Fast Return to LTE

iii.


is

“Handover

Judgment

Based

on


of

E-UTRA

FDD/TDD).

Alternatively,

UCelInfoFDD.csfbMulSrv2LteSw is “Redirection without Measurement”, the UE supports EUTRAN (Support of E-UTRA FDD/TDD). iv.


and the detailed strategy and parameters refer to “ZTE UMTS User Dedicated Frequency Priority Feature Guide”. 2.

The process of only CS Service After the UE is handed over from EUTRAN to UTRAN due to CSFB, if the CS service is released for Single-RAB, and if the following conditions are satisfied, the EUTRAN cell downlink central frequency information is filled in the Redirection info of the RRC Connection Release message. Then the UE is redirected to EUTRAN. i.


ii.


iii.


iv.


v.


and the detailed strategy and parameters refer to “ZTE UMTS User Dedicated Frequency Priority Feature Guide”. 3.

CS Service Establishment Failure

After the UE is handed over from EUTRAN to UTRAN due to CSFB, if the IU Release Command message of CS domain is received, and if the following conditions are satisfied, the EUTRAN cell downlink central frequency information is filled in the Redirection info of the RRC Connection Release message. Then the UE is redirected to EUTRAN.


23

Fast Return to LTE

PS services exist

-

i.


i.


ii.


is

“Handover

Judgment

Based

on


of

E-UTRA

FDD/TDD).

Alternatively,

UCelInfoFDD.csfbMulSrv2LteSw is “Redirection without Measurement”, the UE supports EUTRAN (Support of E-UTRA FDD/TDD). iii.


and the detailed strategy and parameters refer to “ZTE UMTS User Dedicated Frequency Priority Feature Guide”. PS services do not exist

-

ii.


i.


ii.


iii.


iv.





SRVCC

1.

The process of the PS Service when the CS service is released for Multi-RAB Service


24

Fast Return to LTE

After the UE is handed over from EUTRAN to UTRAN due to SRVCC, if the CS service is released for Multi-RAB, and if the following conditions are satisfied, the EUTRAN cell downlink central frequency information is filled in the Redirection info of the RRC Connection Release message. Then the UE is redirected to EUTRAN. i.


ii.


iii.


is

“Handover

judgment

Based

on

Measurement”, and the UE neither supports PS handovers to EUTRAN nor the EUTRAN measurement, and the UE only supports EUTRAN (Support of E-UTRA FDD/TDD). OR UCelInfoFDD.srvccMulSrv2LteSw is “Redirection without Measur ement”, and the UE supports EUTRAN (Support of E -UTRA FDD/TDD). iv.

The highest priority of EUTRAN frequencies is higher than the highest priority of UTRAN frequencies. The frequency and priority acquires from MO_UDePri, and the detailed strategy and parameters refer to “ZTE UMTS User Dedicated

Frequency Priority Feature Guide”. 2.

The process of only CS Service After the UE is handed over from EUTRAN to UTRAN due to SRVCC, if the CS service is released for Single-RAB, and if the following conditions are satisfied, the

EUTRAN cell’s downlink central frequency information is filled in the Redirection info of the RRC Connection Release message. Then the UE is redirected to EUTRAN. i.


ii.


iii.


iv.

UtranCellFDD.srvccCsRel2LteSw is “On”.

v.



25

Fast Return to LTE

and the detailed strategy and parameters refer to “ZTE UMTS User Dedicated Frequency Priority Feature Guide”. 

The process of channel switching from CELL_DCH to CELL_FACH If the PS service channel switching from CELL_DCH to CELL_FACH is triggered in UMTS, and if the following conditions are satisfied, the EUTRAN cell downlink central frequency information is filled in the Redirection info of the RRC Connection Release message. Then the UE is redirected to EUTRAN. i.


ii.


iii.


iv.

UCelInfoFDD.dch2FachRetLteSw is “On”.

v.


and the detailed strategy and parameters refer to “ZTE UMTS User Dedicated Frequency Priority Feature Guide”. Note: 1.

When the condiftion of fast return to LTE is fulfilled, the RNC acquires UE supporting frequencies from MO_UDePri, then fills 4 FDD and 4 TDD frequencies in RRC Connection Release.

3.1.6

Fast Return Strategy of IUR 

Support Fast Return in Redirection Mode via Iur When the SRNC has no radio links and the EUTRAN neighboring cells exist, the SRNC saves the frequency information of EUTRAN neighboring cells returned by the DRNC, and the frequency information of EUTRAN neighboring cells that are the combination of those returned by the DRNC and configured by the SRNC are filled in the Redirection info of the RRC Connection Release message if the redirection conditions are satisfied.


26

Fast Return to LTE

Currently, only redirection mode is supported. 

Support CSFB Indicator via Iur When the SRNC sends the Relocation Request message to the DRNC, if the UE is identified as a CSFB user, the SRNC needs to fill “CSFB” in CSFB Information of the Source to Target Transparent Container to enable the target SRNC to identify the CSFB user and apply the Fast Return to EUTRAN function after the relocation procedure ends.

3.1.7

Special Scenario that CSFB Users are Forbidden to Fast Return to LTE For a CSFB terminated user, after location update, the CS RAB is not assigned but IU connection is released due to CN parameter configuration problem. The UE will return to LTE according to the current strategy, which leads to call failure. Therefore, this function is introduced, fast return to LTE is forbidden in this scenario, to increase the success rate of call setup and improve user experience.

This function is controlled by the parameter URncInfo.csmtIdentifySwch. When URncInfo.csmtIdentifySwch is set to 0, before a CSFB user releasing CS IU connection performs fast return to LTE, the following co nditions need to be judged, if they are both met, fast return to LTE is forbidden, otherwise, fast return to LTE is performed.

3.1.8



CSMT IE is carried in LOCATION UPDATING REQUEST message.



CS RAB has not been established.

Supplementary Services Forbidden to Fast Return to LTE When UE with Supplementary Services performs fast return to LTE during RRC connection release, UE is abnormal during LTE TAU procedure. In this case, this feature is introduced to forbid UE with Supplementary Services fast return to LTE during RRC connection release to improve user experience. This function is controlled by the parameter URncFunction.gresPara56 bit17 When this

parameter is set as “on”, if RNC identifies UE with Supplementary Services through NAS


27

Fast Return to LTE

and this UE satisfies all criteria of fast return to LTE by redirection mode, then this UE is forbidden to fast return to LTE. Otherwise, this UE is allowed to fast return to LTE .

3.2

ZWF21-03-112 Packet Service Fast Return to LT E for Inactive Mode Whether enabling the dedicated priority functionality affects the judgment on triggering fast return to LTE. See the details in the following chapters.

3.2.1

Strategy without Dedicated Priority When the PS service of the UE in the UTRAN network migrates from other states to URA_PCH/CELL_PCH or IDLE, including CELL_DCH -> CELL_PCH/URA_PCH, CELL_DCH -> IDLE, CELL_FACH -> CELL_PCH/URA_PCH, and CELL_FACH -> IDLE, perform the Redirection flow as long as the following four conditions are met. Fill in the downlink central frequency information in Redirection info of RRC Connection Release. And the UE returns to the EUTRAN network.

3.2.2

1.

There are EUTRAN neighboring cells;

2.

The UE is capable of “Support of E-UTRA FDD/TDD ”;

3.

URncFunction.fastRetEUtranSwch is “on”;

4.

UExtCelInfoFDD.pchIdleRetLteSw is “on”.

Strategy with Dedicated Priority When both ULogicalRnc.dePriRncSwch and UExtCelInfoFDD.dePriSwch are enabled, the processing is described below. When the PS service of the UE in the UTRAN network migrates from other states to URA_PCH/CELL_PCH or IDLE, including CELL_DCH -> CELL_PCH/URA_PCH, CELL_DCH -> IDLE, CELL_FACH -> CELL_PCH/URA_PCH, and CELL_FACH -> IDLE,


28

Fast Return to LTE

perform the Redirection flow as long as the following four conditions are met. Fill in the downlink central frequency information in Redirection info of RRC Connection Release. And the UE returns to the EUTRAN network. 1.

The UE is capable of “Support of E-UTRA FDD/TDD”;

2.

URncFunction.fastRetEUtranSwch is “on”;

3.

UExtCelInfoFDD.pchIdleRetLteSw is “on”;

4.

The highest priority of EUTRAN frequencies is higher than the highest priority of UTRAN frequencies.

Note: When the UE meets the conditions of fast return to LTE, the RNC acquires UE supporting frequencies from MO_UDePri. Excluding the frequency which the UE does not support, fill in the LTE frequency in the RRC Connection Release message according to the dedicated priority from the highest to the lowest. Fill in at most four frequencies for FDD and TDD respectively.

3.3

ZWF21-03-113 Packet Service Fast Return to LT E for Active Mode For the PS service in CELL_DCH, the RNC actively triggers fast return to LTE to improve

user’s experience. Whether enabling the dedicated priority functionality affects the judgment on triggering fast return to LTE. See the details in the following chapters.

3.3.1

Strategy without Dedicated Priority For the PS service in CELL_DCH, the RNC actively triggers fast return to LTE, which is controlled

by

UExtCelInfoFDD.dchPsBldRedLteSw.

When

URncFunction.fastRetEUtranSwch is “on”,


29

Fast Return to LTE

When establishing the PS service, if UExtCelInfoFDD.dchPsBldRedLteSw is enabled and the UE supports LTE, start the timer PSOnUMTSTimer. 

If the “penalty on UE” flag is “false”, the timer PSOnUMTSTimer is taken from the best cell’s parameter UExtCelInfoFDD.bldRedLteT1Short ;



If the “penalty on UE” flag is “true”, the timer PSOnUMTSTimer is taken from the best cell’s parameter UExtCelInfoFDD.bldRedLteT1Long ;



For description of “penalty on UE” flag, please refer to chapter 3.4.

When the timer PSOnUMTSTimer is up, the “penalty on UE” flag is set to be “false”. If the following conditions are met, release the RRC connection and make the UE fast return to LTE. 1.

The parameter UExtCelInfoFDD.dchPsBldRedLteSw of the best cell is “ on”;

2.

In CELL_DCH mode, only PS service through Iu interface is available;

3.

There are EUTRAN neighboring cells.

Otherwise, restart PSOnUMTSTimer. Note: 1.

Keep the timer if the best cell has changed before the timer is up;

2.

When the UE moves across the RNC, take the parameters of the cell to which the last link on SRNC belongs as long as there are no links on SRNC;

3.

When the UE meets the conditions of fast return to LTE, find the EUTRAN frequencies of which the UE is capable from the existing EUTRAN neighboring cells. In the Redirection of the RRC Connection Release message, fill in at most four EUTRAN FDD frequencies and four EUTRAN TDD frequencies.

3.3.2

Strategy with Dedicated Priority When both ULogicalRnc.dePriRncSwch and UExtCelInfoFDD.dePriSwch are enabled, and URncFunction.fastRetEUtranSwch is “on”, the processing is described below.


30

Fast Return to LTE

For the PS service in CELL_DCH, the RNC actively triggers fast return to LTE, which is controlled by UExtCelInfoFDD.dchPsBldRedLteSw. When establishing the PS service, if UExtCelInfoFDD.dchPsBldRedLteSw is enabled and the UE supports LTE, start the timer PSOnUMTSTimer.

If the “penalty on UE” flag is “false”, the timer PSOnUMTSTimer is taken from the



best cell’s parameter UExtCelInfoFDD.bldRedLteT1Short ; If the “penalty on UE” flag is “true”, the timer PSOnUMTSTimer is taken from the



best cell’s parameter UExtCelInfoFDD.bldRedLteT1Long ; For description of “penalty on UE” flag, please refer to chapter 3.4.



When the timer PSOnUMTSTimer is up, the “penalty on UE” flag is set to be “false”. If the following conditions are met, release the RRC connection and make the UE fast return to LTE. 1.

The parameter UExtCelInfoFDD.dchPsBldRedLteSw of the best cell is “ on”;

2.

In CELL_DCH mode, only PS service through Iu interface is available;

3.

There are EUTRAN neighboring cells;

4.

The highest priority of EUTRAN frequencies higher than the highest priority among UTRAN frequencies.

Otherwise, restart PSOnUMTSTimer. Note: 1.

Keep the timer if the best cell has changed before the timer is up;

2.

When the UE moves across the RNC, take the parameters of the cell to which the last link on SRNC belongs as long as there are no links on SRNC;

3.

When the UE meets the conditions of fast return to LTE, the RNC acquires UE supporting frequencies from MO_UDePri. Excluding the frequency points which the UE does not support, fill in the LTE frequencies in the RRC Connection Release message according to the dedicated priority from the highest to the lowest. Fill in at most four frequencies for FDD and TDD respectively.


31

Fast Return to LTE

3.4

Penalty strategy

3.4.1

Penalty Mechanism Principle To avoid UE’s ping-pong redirection between UTRAN and LTE in the LTE poorly covered districts, the penalty mechanism is applied. That is, when RNC initiates the fast return to LTE, the timer blindRedLteT2 is enabled. Before it expires, if RNC receives UE’s RRC connection request again, the LTE is considered to fail to provide the service to the UE, then the UE is punished. During the penalty period (PSOnUMTSTimer), RNC does not perform the Fast Return to LTE for the UE. The feature is controlled by UExtCelInfoFDD.blindRedPenSw . The following scenarios suit the Fast Return to LTE without measurement redirection. 

PS Service when the CS service is released for Multi-RAB Service (including CS service establishment failure)



Fast return to LTE in data service inactivated mode



Fast return to LTE in data service activated mode

1.

For “Fast return to LTE in data service activated mode”, please refer to chapter 3.3;

2.

Following lists how to handle other scenarios. -

When establishing PS service, if UExtCelInfoFDD.dchPsBldRedLteSw is enabled and the UE supports LTE, and the “penalty on UE” flag is “True”, activate the timer PSOnUMTSTimer. The PSOnUMTSTimer is obtained from

the best service cell’s parameter UExtCelInfoFDD.bldRedLteT1Long. During the penalty period, if the above scenario satisfies the conditions of UE fast return to LTE and the “penalty on UE” flag is “True”, no fast return to LTE is performed. -

When PSOnUMTSTimer expires, set the “penalty on UE” flag to “False”. Restart the PSOnUMTSTimer, whose value is obtained from the best service

cell’s parameter UExtCelInfoFDD.bldRedLteT1Short..


32

Fast Return to LTE

3.4.2

Penalty on UE Flag The “penalty on UE” flag indicates the UE that initiates RRC connection request again after original Fast Return to LTE. The default value is False. In the above mentioned scenario, when the RNC executes RRC connection release and Fast Return to LTE, enable the timer UExtCelInfoFDD.blindRedLteT2.. 

If the UE’s timer does not expire, -

Terminate the timer after receiving UE’s non -CSFB RRC connection request, and set the “penalty on UE” flag to True.

-

Terminate the timer after receiving UE’s CSFB RRC connection request, and set the “penalty on UE” flag to False.



If the UE’s timer expires, -

Set the punished UE flag to “False” if not receiving UE’s RRC connection request.

3.5

EUTRAN Frequency Priority If the EUTRAN network has multiple frequencies, when UE is handed over or redirected from UTRAN to EUTRAN, RNC hands over or redirects UE to the preset highest priority EUTRAN frequency. The feature is controlled by UExtCelInfoFDD.prioBsdHoRedi4ESw.

3.5.1

Frequency Priority Configuration Configure the frequency priority according to the following parameters.

EUTRAN

neighboring

cell’s

frequency

number

is

indicated

by

UUtranCellFDD.eutraFreqNum. EUTRAN frequency is indicated by dlEARFCN

is

the

number

UUtranCellFDD.dlEARFCN. Among group,

dimension

is

indicated

which, by

UUtranCellFDD.eutraFreqNum.


33

Fast Return to LTE

EUTRAN frequency priority is indicated by UUtranCellFDD.frePrio4EHoRedi. Note: EUTRAN frequency requires frequency configured by EUTRAN neighboring cell configuration (MO UEUtranRelation) to perform configuration.

3.5.2

Frequency Priority Strategy in Handover/Redirection During the handover/redirection from UMTS to EUTRAN, the following strategies can be achieved according to the configured frequency priorities. 

Measurement based handover/redirection i.

After receiving the measurement report, sequence the cells by the frequency priority.

ii.

If performing handover, select the cell at the highest frequency priority to initiate the handover.

iii.

If the redirection is executed, fill in the frequency at the highest priority level in Inter-RAT info of Release Info under RRC Connection Release. If several frequency priority levels are the same, fill in all of them. FDD and TDD can be filled in up to 4 respectively.



Redirection without measurement i.

For the EUTRAN neighboring cell frequency list maintained in the network side, sequence them by the frequency priority order.

ii.

If the RRC Connection Reject redirection is executed, fill in the Inter-RAT info by the frequency priority levels from high to low of Redirection Info. FDD and TDD can be filled in up to 4 respectively.

iii.

If the RRC Connection Reject redirection is executed, fill in the frequency at the highest priority level in Inter-RAT info of Redirection Info. If several frequency priority levels are the same, fill in all of them. FDD and TDD can be filled in up to 4 respectively.


34

Fast Return to LTE

Note: 1.

1 For executing handover or redirection decision, see ZTE UMTS Handover with LTE Feature Guide.

2.

For executing RRC Connection Reject or RRC Connection Release redirection decision, see ZTE UMTS RRC Connection Redirect Feature Guide .

3.5.3

Relationship with Dedicated Priority For RRC connection redirection triggered by the congestion or load control and the Fast return to LTE based redirection scenarios, if the dedicated priority is enabled and the corresponding priority information is configured, this feature is not executed. Among which, 1.

For the RRC connection redirection triggered by the forced release of services that congestion and load control trigger, see ZTE UMTS RRC Connection Redirect Feature Guide.

2.

For the Fast return to LTE based redirection, see ZTE UMTS Fast Return to LTE Feature Guide.

3.

For the dedicated priority configuration, see ZTE UMTS User Dedicated Frequency Priority Feature Guide.

3.6

Optimization of Redirection to LTE Strategy for Only PS Signaling For a UE forbidden to access the LTE due to EUTRAN service handover attribute, the UE can be redirected to LTE when it has onl y PS signaling, and the access failure in LT E occurs. To avoid this kind of failure, the RNC should determine the EUTRAN service handover attribute of PS services which the UE had established. When the redirection to LTE is triggered to a UE which has only PS signaling and no PS services,


35

Fast Return to LTE



If the EUTRAN service handover attribute (“Handover to E-UTRAN shall not be performed”) is carried by one of PS services which the UE had established, the UE with only PS signaling is not permitted to redirect to LTE.



If the EUTRAN service handover attribute is not carried by any of PS services which the UE had established, or no PS services had been established, the UE with only PS signaling is permitted to redirect to LTE.

4

Parameters

4.1

ZWF21-03-111 Fast Return to LTE Managed

Logic

Object

Name

Parameter Description

Value Range

Unit

Default Value

Recom mende d Value

This parameter is a global switch that enables or disables fast return of UE to the EUTRAN. When this switch is turned on, the RNC in a network with both UMTS and EUTRAN deployed can instruct a UE to fast return URncFunc tion.fastR etEUtranS wch

RNC

to the EUTRAN upon a CS

Switch of

release after the UE is handed

Fast Return over from the EUTRAN to the to

UTRAN due to CSFB or

E-UTRAN

SRVCC.

0:Off 1:On

BYTE

0:Off

1:On

When this switch is turned off, the RNC in a network with both UMTS and EUTRAN deployed will not instruct a UE to fast return to the EUTRAN upon a CS release after the UE is handed over from the EUTRAN to the UTRAN due to CSFB or


36

Fast Return to LTE

Managed

Logic

Object

Name

Value


Unit

Range

Default Value

Recom mende d Value

SRVCC. 0: Off 1:

The parameter indicates Switch of PS Service Fast Return UCelInfoF to EUTRAN DD.csfbM when CS is ulSrv2Lte released for Sw

EUTRAN CSFB Multi-RAB Service

Handov

whether EUTRAN measurement and compressed mode are initialized to hand over the PS service to EUTRAN as soon as possible or redirect it to EUTRAN without measurement after the CS service is released for multi-RAB with CSFB from

er udgme nt

2:

Based

Redirec

on Measur

N/A

0: Off

tion without

ement

Measur

2:

ement

Redirect

EUTRAN, so that better EUTRAN services are provided for UEs that support EUTRAN.

ion without Measur ement

PS Handover Mode when URncInfo. CS is csfbPsHo released for 2LteMode EUTRAN CSFB Multi-RAB

This parameter indicates the

0: PS

mode of PS handover from

Handov

UTRAN to EUTRAN. PS

er

handover or redirection can be 1: adopted based on UE

Redirect

capability.

ion

0: PS N/A

1:

Handov Redirec er

tion

s

10

10

N/A

Off

1: On

Service when pre-redirection information is not indicated in URncInfo.

Timer for

RRC connection Request,

if

CSFB the time between RRC csfbIdentif Identificatio connection Request and CS yTimer n RAB establish is not greater

0..6553 5

than the parameter, the service is indicated CSFB. UtranCell Switch of

This parameter indicates cell

FDD.csfb Fast Return switch of fast return to CsRel2Lte to EUTRAN EUTRAN for CS service. If the


0: Off 1: On

37

Fast Return to LTE

Managed

Logic

Object

Name

Sw


when

switch is On, when CS is

EUTRAN

released, frequency of

Value

Unit

Range

Default Value

Recom mende d Value

CSFB CS is EUTRAN is filled in redirection released

IE. This parameter indicates the number of users with

UCelInfoF

User

compressed mode activated

Number

for the balance strategy based

with

on measurement. When a new

Compresse user accesses and

d Mode DD.simCo Activation mpUserN for Balance um Strategy Based On

measurement balance requirements are satisfied, if the number of current users in

0..255, step 1

N/A

16

16

s

6

6

N/A

0: Off

1: On

compressed mode is not less than this parameter,

Measureme compressed mode will not be nt

activated, compressed mode will be activated after rab assignment procedure. This parameter indicates timer of deactivate compressed mode for Fast Return to

Timer of URncInfo. psHoLteM easTimer

EUTRAN.If compressed mode

Deactivate is initialized due to fast return Compresse to EUTRAN, the timer

(1..255)

d Mode for activates. When the timer

s, step

Fast Return expired, if event (3C) doesn’ t 1s to EUTRAN report, RNC will judge whether compressed mode is deactivate or not based on c urrent signal quality. Switch of

When single ps service is

UCelInfoF Fast Return transfer from CELL_DCH to DD.dch2F to EUTRAN CELL_FACH, the parameter

0: Off

achRetLte for PS Only indicates whether fast return to 1: On Sw

when UE

EUTRAN will be performed. If

RRC Status the parameter is On,


RNC will

38

Fast Return to LTE

Managed

Logic

Object

Name


Value Range

Unit

Default Value

Recom mende d Value

Transferrin initial RRC connection release g from

and fill EUTRAN cells'

CELL_DCH frequency. to CELL_FAC H This parameter is the switch of checking the UE E-UTRA Switch of URncInfo . checking cheEutraC the UE apiSw

E-UTRA Capability

Capability before initiating the PS handover procedure from UMTS to LTE. The parameter 0: Off is On, check that whether UE

1: On

N/A

0: Off

1: On

reports the UE E-UTRA Capability, if reports, the PS handover procedure is permitted, else not. The parameter indicates

ULogicalR RNC nc.rncSrvc SRVCC cSw

Switch

whether RNC supports the SRVCC function of

0: Off

TE->UTRAN to provide

1: On

N/A

0: Off

1: On

continuity of voice services between LTE and UTRAN. 0: Off

Switch of PS Service Fast Return UCelInfoF to EUTRAN DD.srvcc when CS is MulSrv2Lt released for eSw

EUTRAN SRVCC Multi-RAB Service

The parameter indicates

1:

whether EUTRAN

Handov

measurement and compressed er mode are initialized to hand

udgme

over the PS service to

nt

EUTRAN as soon as possible Based or redirect it to EUTRAN

on

N/A

0: Off

0: Off

without measurement after the Measur CS service is released for

ement

multi-RAB with SRVCC from

2:

EUTRAN, so that better

Redirect

EUTRAN services are provided ion for UEs that support EUTRAN. without Measur


39

Fast Return to LTE

Managed

Logic

Object

Name

Value


Range

Unit

Default Value

Recom mende d Value

ement PS Handover URncInfo. srvccPsH o2LteMod e

Mode when CS is released for EUTRAN SRVCC Multi-RAB

This parameter indicates the

0: PS

mode of PS handover from

Handov

UTRAN to EUTRAN. PS

er

handover or redirection can be 1: adopted based on UE

Redirect

capability.

ion

0: PS N/A

0: PS

Handov Handov er

er

N/A

0: Off

0: Off

N/A

0: Off

0: Off

N/A

0: Off

0: Off

Service Switch of UtranCell FDD.srvcc CsRel2Lte Sw

This parameter indicates cell

Fast Return switch of fast return to to EUTRAN EUTRAN for CS service.If the when

switch is On, when CS is

EUTRAN

released, frequency of

0: Off 1: On

SRVCC CS EUTRAN is filled in redirection is released IE. This parameter indicates whether a CSFB user is forbidden to fast return to LTE. When this parameter is set to 1, a CSFB user is not forbidden to fast return to LTE. When this

URncInfo. csmtIdenti fySwch

CSMT IE

parameter is set to 0, if a CSFB

for CSFB

user is a called user which

0: Off

Identificatio having the location updating n Switch

1: On

(CSMT IE is carried in LOCATION UPDATING REQUEST message), and have not established any CS RAB, this user is forbidden to fast return to LTE, otherwise, not forbidden.

URncInfo. ueLteCap JugSw


UE LTE

This

parameter

Capability

disables

UE

Judgement determination Switch

enables

or

capability 0: Off when

the 1: On

capability of the UE is not

40

Fast Return to LTE

Managed

Logic

Object

Name

Value


Unit

Range

Default Value

Recom mende d Value

obtained. 0: The UE does not support the LTE capability. 1: If the "CSFB Information" IE is contained in a Relocation Request capability

message, of

considered

the

as

the UE

is

"Support

of

E-UTRA FDD/TDD". The parameter is the switch of UExtCelIn Dedicated foFDD.de priority PriSwch

Switch

dedicated priority. When this function is on, it could make 0: Off expected UE camp on some 1: On

N/A

0: Off

0: Off

N/A

0:off

0:off

N/A

0: Off

1: On

10

10

frequency when UEs leave CELL_DCH.

The

it could make

parameter camp

expected UE

on some frequency

is the RNC when UEs leave CELL_DCH. ULogicalR switch of

0:off

nc.dePriR dedicated ncSwch

1:on

priority. When this function is on This parameter is Blind Fast

UExtCelIn Blind Fast

Return to LTE penalty Switch.

foFDD.blin Return to

When this parameter is on, 0: Off

dRedPen LTE penalty there is a penalty mechanism 1: On Sw

Switch

for PS Blind Fast Return to LTE. This

parameter

is

Blind

redirection to LTE Timer 2. UExtCelIn Blind

when UE is Blind Fast Return

foFDD.blin redirection to LTE, this timer starts. If RNC dRedLteT to LTE

recerives

2

connection request before this

Timer 2

a

UE's

RRC

(1..1800 )s, step s 1s

timer expires, LTE coverage would be considered to be bad


41

Fast Return to LTE

Managed

Logic

Object

Name


Value Range

Unit

Default Value

Recom mende d Value

and not to provide service for this

UE;

otherwise,

LTE

coverage would be consedered to be good. bit17:

Switch

of

Forbid

Supplementary Services fast return

to

lte

during

RRC

connection release URncFunc tion.gresP ara56

Global Reserved Parameter 56

If this parameter is set as "1:On":

Supplementary

Services cannot fast return to lte

during

RRC

connection

0: Off 1: On

N/A

0: Off

1: On

release If this parameter is set as "0:off":

Supplementary

Services can fast return to lte during RRC connection release

4.2

ZWF21-03-112 Packet Service Fast Return to LT E for Inactive Mode Managed

Logic

Object

Name Switch of Fast Return to EUTRAN for PS

UExtCelIn when UE foFDD.pc RRC Status hIdleRetLt Transferrin eSw

g to PCH/IDLE (CELL_PC H/URA_PC H/idle)



Value Range

Unit

Default Value

Recom mende d Value

This parameter indicates whether fast return to EUTRAN is performed when a PS service is transferred to PCH/IDLE (CELL_PCH/URA_PCH/idle). If this parameter is set to On, the

0:Off 1:On

BYTE

0:Off

1:On

RNC initiates RRC connection release and fills EUTRAN frequency information in the redirection field.

42

Fast Return to LTE

4.3

ZWF21-03-113 Packet Service Fast Return to LT E for Active Mode Managed

Logic

Object

Name

UExtCelIn foFDD.dc hPsBldRe dLteSw

PS in CELL_DCH Blind Fast Return to LTE Switch


Value

Unit

Range

Default Value

Recom mende d Value

This parameter is PS in CELL_DCH Blind Fast Return to LTE Switch. When PS stays 0:Off in CELL_DCH, RNC will trigger 1:On

BYTE

0:Off

1:On

s

10

10

s

600

600

UE fast returns to LTE, without measurement. This parameter is Blind redirection to LTE Timer 1 Short. Regards to PS in

UExtCelIn foFDD.bld RedLteT1 Short

Blind redirection to LTE Timer 1 (Short)

CELL_DCH Blind Fast Return to LTE, if RNC does not

(1..6553

recerive a UE's RRC

5)s,

connection request before

step 1s

blindRedLteT2 expires, LTE coverage would be considered good, and set a short timer(bldRedLteT1Short) for UE. This parameter is Blind redirection to LTE Timer 1 Long. Afer UE Blind Fast Returns to LTE, if RNC

UExtCelIn foFDD.bld RedLteT1 Long

Blind redirection to LTE Timer 1 (Long)

recerives a UE's RRC connection request before

(1..6553

blindRedLteT2 expires, LTE

5)s,

coverage would be considered step 1s bad and not to provide service for UE, and a long timer(bldRedLteT1Long) is set for UE. UE could not fast return to LTE before bldRedLteT1Long expires.


43

Fast Return to LTE

4.4

EUTRAN Frequency Priority Managed

Logic

Parameter

Object

Name

Description

Value Range

Unit

Default Value

Recom mende d Value

This parameter indicates whether to consider the frequency priority of neighbor cells in Switch of Considering Frequency UExtCelIn Priority in foFDD.pri UMTS->EoBsdHoR UTRAN edi4ESw Inter-RAT Handover or Redirection

E-UTRAN inter-RAT handover or redirection. The parameter is "On", the neighbor cell with the highest frequency priority is taken as the

0:Off 1:On

BYTE

0:Off

1:On

N/A

-

-

-

-

target cell for handover or redirection. The parameter is "Off", the frequency priority is not considered in E-UTRAN inter-RAT handover or redirection. This parameter indicates the number

Number of of neighbor EUTRAN UUtranCel EUTRAN

centre frequencies.

lFDD.eutr Centre

The number of

0..16

aFreqNum Frequencie frequencies and its s

priorities are configured according to this parameter.

Downlink

The parameter

Band 1: 0-599,

UUtranCel E-UTRAN

indicates the downlink Band 2:

lFDD.dlEA Absolute

E-UTRAN Absolute

600-1199, Band N/A

RFCN

Radio Frequency

3: 1200-1949,

Radio

Frequency Channel Number


Band 4:

44

Fast Return to LTE

Managed

Logic

Parameter

Object

Name

Description

Channel

(EARFCN).

Number for dlEARFCN and Indicating

Unit

Value

Recom mende d Value

1950-2399, Band 5: 2400-2649,

frePrio4EHoRedi are Band 6:

Frequency used in pairs, and Priority

Value Range

Default

2650-2749, Band

there is a one-to-one 7: 2750-3449, correspondence

Band 8:

between each

3450-3799, Band

frequency in

9: 3800-4149,

dlEARFCN and its

Band 10:

priority in

4150-4749, Band

frePrio4EHoRedi.

11: 4750-4949, Band 12:

F_DL = F_DL_low +

5010-5179, Band

0.1 * (N_DL –

13: 5180-5279,

N_Offs-Dl), where

Band 14:

F_DL is center carrier 5280-5379, Band frequency, F_DL_low 17: 5730-5849, is dl lowest carrier

Band 18:

frequency, N_DL is

5850-5999, Band

DlEARFCN,

19: 6000-6149,

N_Offs-Dl is carrier

Band 20:

frequency offset

6150-6449, Band

indicated by band

21: 6450-6599,

indicator.

Band 22:

DBS_FP_MAX_NUM 6600-7399, Band _EUTRAN_FREQ is 23: 7500-7699, the maximum number Band 24: of neighbor EUTRAN 7700-8039, Band centre frequencies,

25: 8040-8689,

the value is 16.

Band 26: 8690-9039, Band 27: 9040-9209, Band 28: 9210-9659, Band 29: 9660-9769, Band 33: 36000-36199, Band 34:


45

Fast Return to LTE

Managed

Logic

Parameter

Object

Name

Description

Value Range

Unit

Default Value

Recom mende d Value

36200-36349, Band 35: 36350-36949, Band 36: 36950-37549, Band 37: 37550-37749, Band 38: 37750-38249, Band 39: 38250-38649, Band 40: 38650-39649, Band 41: 39650-41589, Band 42: 41590-43589, Band 43: 43590-45589, Band 44: 45590-46589 This parameter indicates the frequency priority of neighbor cells in E-UTRAN inter-RAT Frequency handover or UUtranCel

Priority for redirection.The lowest

E-UTRAN lFDD.frePr Inter-RAT io4EHoRe Handover di or

priority is 0, and the highest priority is 2.

(0..2)

N/A

-

-

dlEARFCN and frePrio4EHoRedi are

Redirection used in pairs, and there is a one-to-one correspondence between each frequency in dlEARFCN and its


46

Fast Return to LTE

Managed

Logic

Parameter

Object

Name

Description

Value Range

Unit

Default Value

Recom mende d Value

priority in frePrio4EHoRedi. DBS_FP_MAX_NUM _EUTRAN_FREQ is the maximum number of neighbor EUTRAN centre frequencies, the value is 16.

5

Related Counters and Alarms

5.1

Related Counters

5.1.1

ZWF21-03-111 Fast Return to LTE

Table 5-1

Counter List

Counter ID 312106776

314087002

5.1.2

Name Number of attempted relocation preparation for outgoing PS inter-RAT handovers(Utran to EUtran) Number of RRC connection release for redirection to LTE,cause by fast return

ZWF21-03-112 Packet Service Fast Return to LTE for Inactive Mode

Table 5-2

Counter List


314087002


Name

Number of attempted relocation preparation for outgoing PS inter-RAT handovers(Utran to EUtran) Number of RRC connection release for redirection to LTE,cause by fast return

47

Fast Return to LTE

5.1.3

ZWF21-03-113 Packet Service Fast Return to LTE for Active Mode

Table 5-3

Counter List


314087002

5.2

Name Number of attempted relocation preparation for outgoing PS inter-RAT handovers(Utran to EUtran) Number of RRC connection release for redirection to LTE,cause by fast return

Related Alarms This feature has no related alarm.

6

Engineering Guide

6.1

Application Scenario This feature is applied to the UTRAN and EUTRAN association scenario. Different sub-functions are suit for different scenes. When the UMTS and EUTRAN are jointly deployed, the UE in EUTRAN is handed over to UTRAN owing to CSFB, SRVCC. To make these UEs get better service experience, the UTRAN side will return them to EUTRAN by mode of PS HO or Redirection. 1.

When the function of IMS is not supported in LTE, the fast return to LTE for the CSFB service can be applied to all the scenes to guarantee the voice call establishment successfully.

2.

For the SRVCC service, because the triggering conditions from LTE to UMTS are based on the signaling quality or load congestion in general, this function is always set to off to avoid the ping-pong reselection/handover between UMTS and LTE.

3.

For the PS service from CELL_DCH to CELL_FACH or CELL_DCH/CELL_FACH to URA_PCH/CELL_PCH/IDLE,


The

Ping-Pong

reselection/handover

may

be

48

Fast Return to LTE

happened without LTE quality judgment. The function should be avoided to be activated in the area which is poor coverage by LTE, otherwise the KPI and service performance will be influenced. 4.

For priority function, the RNC handovers or redirects the users to specific frequency, so as to control load distribute in multi frequency layers scene

5.

For the PS service in CELL_FACH, the RNC triggers fast return to LTE based on

the UEs’ measurement report as soon as possible, so as to control load distribute in multi- frequency scene. 6.

For the PS service in CELL_DCH, the RNC actively triggers fast return to LTE to improve users experience.

6.2

Feature Activation Procedure

6.2.1

Fast Return to LTE The purpose of this chapter is just to guide the reader how to find the GUI location of the parameters which are related to the deployment of this feature. The values indicated by the captures possibly are not the real value to configure. Please refer to the last column of table in chapter 4.1 for the practical configuration value. In the configuration resource tree window, open the [Modify Area->Managed Element->

UMTS Logical Function Configuration] interface and set the parameter “ RNC Switch of Fast Return to E-UTRAN ”, as shown in Figure 6-1

Figure 6-1


Parameters configuration interface 1

49

Fast Return to LTE

In the configuration resource tree window, open the [Modify Area->Managed Element-> UMTS Logical Function Configuration->UTRAN Cell->Extended Info of UTRAN Cell]

interface and set the parameter “Switch of PS Service Fast Return to EUTRAN when CS is released for EUTRAN CSFB Multi- RAB Service”, as shown in Figure 6-2.

Figure 6-2


In the configuration resource tree window, open the [Modify Area->Managed Element-> UMTS Logical Function Configuration->Extended Info of RNC] interface and set the

parameter “PS Handover Mode when CS is released for EUTRAN CSFB Multi-RAB Service”, “Timer of Deactivate Compressed Mode for Fast Return to EUTRAN”, “Timer

for CSFB Identification(s)”, as shown in Figure 6-3 Figure 6-3



50

Fast Return to LTE

In the configuration resource tree window, open the [Modify Area->Managed Element-> UMTS Logical Function Configuration->UTRAN Cell] interface and set the parameter

“Switch of Fast Return to EUTRAN when EUTRAN CSFB CS is released”, as shown in Figure 6-4

Figure 6-4



interface and set the parameter “User Number with Compressed Mode Activation for Balance Strategy Based On Measurement”,as shown in Figure 6-5.


51

Fast Return to LTE

Figure 6-5



interface and set the parameter “ Switch of Fast Return to EUTRAN for PS Only when UE RRC Status Transferring from CELL_DCH to CELL_FACH ”, as shown in Figure 6-6

Figure 6-6



52

Fast Return to LTE


parameter “Switch of checking the UE E -UTRA Capability”,as shown in Figure 6-7 Figure 6-7


In the configuration resource tree window, open the [Modify Area->Managed Element-> UMTS Logical Function Configuration->PLMN Relating Configuration->Logic RNC Configuration] interface and set the parameter “RNC SRVCC Switch”, as shown in Figure 6-8

Figure 6-8



interface and set the parameter “Switch of PS Service Fast Return to EUTRAN when CS is released for EUTRAN SRVCC Multi- RAB Service”, as shown in Figure 6-9.


53

Fast Return to LTE

Figure 6-9



parameter “PS Handover Mode when CS is released for EUTRAN SRVCC Multi-RAB Service”,as shown in Figure 6-10

Figure 6-10


In the configuration resource tree window, open the [Modify Area->Managed Element-> UMTS Logical Function Configuration-> UTRAN Cell] interface and set the parameter

“Switch of Fast Return to EUT RAN when EUTRAN SRVCC CS is released ”, as shown in Figure 6-11


54

Fast Return to LTE

Figure 6-11


In the configuration resource tree window, open the [Modify Area->Managed Element-> UMTS Logical Function Configuration-> PLMN Relating Configuration-> Logic RNC Configuration] interface and set the parameter “Dedicated priority RNC Switch ”, as shown in Figure 6-12

Figure 6-12



55

Fast Return to LTE

In the configuration resource tree window, open the [Modify Area->Managed Element-> UMTS Logical Function Configuration-> UTRAN Cell->Extended Information 2 of UT RAN Cell] interface and set the parameter “Dedicated priority Switch ”, as shown in Figure 6-13

Figure 6-13


In the configuration resource tree window, open the [Modify Area->Managed Element-> UMTS Logical Function Configuration->Extended info of RNC] interface and set the

parameter “Switch of acquiring SPID based on IMEI ”, as shown in Figure 6-14.


56

Fast Return to LTE

Figure 6-14


In the configuration resource tree window, open the [Modify Area->Managed Element-> UMTS Logical Function Configuration->Global Information Configuration->SPID and PriGroup relationship Profile->SPID and PriGroup relationship] interface and set the

parameter “SPID Index”,as shown in Figure 6-15 Figure 6-15



57

Fast Return to LTE

In the configuration resource tree window, open the [Modify Area->Managed Element-> UMTS Logical Function Configuration->Service Configuration->RAN Priority When UE in Dedicated State ] interface and set the parameter “ Priority Group ID ”, as shown in Figure 6-16

Figure 6-16


In the configuration resource tree window, open the [Modify Area->Managed Element-> UMTS Logical Function Configuration->Service Configuration->Imei TAC List for SPID]

interface and set the parameter “SPID configured by RNC ”, “Length of IMEI TAC”,”Imei TAC”, as shown in Figure 6-17


58

Fast Return to LTE

Figure 6-17

6.2.2


Packet Service Fast Return to LTE for Inactive Mode

The purpose of this chapter is just to guide the reader how to find the GUI location of the parameters which are related to the deployment of this feature. The values indicated by the captures possibly are not the real value to configure. Please refer to the last column of table in chapter 4.2 for the practical configuration value. In the configuration resource tree window, open the [Modify Area->Managed Element-> UMTS Logical Function Configuration-> UTRAN Cell-> Extended Information 2 of

UTRAN Cell] interface and set the parameter “ Switch of Fast Return to EUTRAN for PS when UE RRC Status Transferring to PCH/IDLE(CELL_PCH/URA_PCH/idle)” , as shown in Figure 6-18


59

Fast Return to LTE

Figure 6-18

6.2.3


Packet Service Fast Return to LTE for Active Mode The purpose of this chapter is just to guide the reader how to find the GUI location of the parameters which are related to the deployment of this feature. The values indicated by the captures possibly are not the real value to configure. Please refer to the last column of table in chapter 4.3 for the practical configuration value. In the configuration resource tree window, open the [Modify Area->Managed Element-> UMTS Logical Function Configuration-> UTRAN Cell-> Extended Information 2 of

UTRAN Cell] interface and set the parameter “ PS in CELL-DCH Blind Fast Return to LTE Switch”,”Blind redirection to LTE Timer 1(Short)” , ”Blind redirection to LTE Timer

1(Long)”, as shown in Figure 6-19


60

Fast Return to LTE

Figure 6-19

6.2.4


EUTRAN Frequency Priority In the configuration resource tree window, open the [Modify Area->Managed Element-> UMTS Logical Function Configuration-> UTRAN Cell-> Extended Information 2 of

UTRAN Cell] interface and set the parameter “ Switch of Considering Frequency Priority in UMTS->E-UTRAN Inter- RAT Handover or Redirection”, as shown in as shown in Figure 6-20


61

Fast Return to LTE

Figure 6-20


In the configuration resource tree window, open the [Modify Area->Managed Element-> UMTS Logical Function Configuration-> UTRAN Cell] interface and set the parameter

“Number of EUTRAN Centre Frequencies ”,” Downlink E-UTRAN Absolute Radio Frequency Channel Number for Indicating Frequency Priority ”, ” Frequency Priority for E-UTRAN Inter-RAT Handover or Redirection ”, as shown in Figure 6-21


62

Fast Return to LTE

Figure 6-21


6.3

Feature Validation Procedure

6.3.1

Fast Return to LTE for CSFB

Table 6-1

Feature Validation Procedure 1

Test Item

Fast Return to LTE 1.

WCDMA and LTE system is ready.

2.

Cell1 supports HSUPA, HSDPA and DCH, Cell1 belongs to RNC1/NodeB1. Cell2 belongs to eNodeB1.

3.

Configure Cell1 with Cell2 adjacent cells with different

Preconditions coverage. 4.

Configure RNC support Fast Return to LTE function

5.

UE1 with R8 or higher versions supports both of UMTS and LTE and camps on EUTRAN Cell2 in Idle mode.


63

Fast Return to LTE

Test Item


UE1 makes a CS call to PSTN in EUTRAN cell2.

2.

ENodeB triggers the CSFB service from the Cell2 to Cell1, the

Test Steps CS service establishes on UTRAN Cell1.

Anticipative

3.

Release the CS call and then UE1 fast return to LTE.

1.

In step3, UE1 performs the fast return to EUTRAN Cell2

Result

6.3.2

successfully.

Pack Service Fast Return to LTE for Inactive Mode

Table 6-2


Test Item



2.


3. Preconditions

Configure Cell1 and Cell2 as adjacent cells with different coverage.

4.

Configure RNC support Fast Return to LTE function for inactive mode..

5.

UE1 with R8 or higher versions supports both of UMTS and LTE and camps on UTRAN Cell1 in Idle mode.

1.

UE1 makes a PS service in UTRAN cell1 and start FTP downloading. The service establish in CELL_DCH status.

Test Steps

2.

Stop FTP downloading, UE1 meets the channel status changes from CELL_DCH to inactive mode.

Anticipative Result


3.

UE1 fast return to Cell2..

1.

In step3, UE1 performs the fast return to EUTRAN Cell2 before changes to idle status.

64

Fast Return to LTE

6.3.3

Packet Service Fast Return to LTE for Active Mode

Table 6-3


Test Item



2.


3. Preconditions

Configure Cell1 and Cell2 as adjacent cells with different coverage.

4.

Configure RNC support Fast Return to LTE function in CELL_DCH mode.

5.

UE1 with R8 or higher versions supports both of UMTS and LTE and camps on UTRAN Cell1 in Idle mode.

1.

UE1 makes a PS service in UTRAN cell1, the service establish in CELL_DCH status.

Test Steps 2.

When UE1 stays in UMTS Cell1 and satisfies a certain threshold, UE1 fast return to Cell2.

1. Anticipative Result

In step2, RNC send “RRCConnectionRelease” message with frequency of Cell2 and UE1 performs the fast return to EUTRAN Cell2 successfully.

6.3.4

Fast Return to LTE with Dedicated Priority for CSFB

Table 6-4


Test Item


Fast Return to LTE

65

Fast Return to LTE

Test Item



2.


3. Preconditions

Configure Cell1 with dedicated frequency priority and Configure RNC support dedicated priority function.

4.

Configure RNC support Fast Return to LTE function.

5. UE1 with R8 or higher versions supports both of UMTS and LTE and camps on EUTRAN Cell2. 1.

UE1 makes a CS call to PSTN or another UE in EUTRAN cell2.

2.

ENodeB triggers the CSFB service from the Cell2 to Cell1, the

Test Steps

CS service establishes on UTRAN Cell1 3.

Release the CS call and then UE1 fast return to LTE by dedicated priority.

Anticipative Result

6.4

1.

In step3, UE1 performs the fast return to EUTRAN Cell2 successfully.

Feature Deactivation Procedure Table 6-5

RNC Parameter List

Managed Object. logic name

GUI Name

URncFunction.fastRetE

RNC Switch of Fast Return

UtranSwch

to E-UTRAN

Default

Deactivation

Value

Value

OFF

OFF

OFF

OFF

OFF

OFF

Switch of PS Service Fast UCelInfoFDD.csfbMulSr

Return to EUTRAN when

v2LteSw

CS is released for EUTRAN CSFB Multi-RAB Service

UtranCellFDD.csfbCsRe l2LteSw


Switch of Fast Return to EUTRAN when EUTRAN CSFB CS is released

66

Fast Return to LTE

Managed Object. logic

GUI Name

name

Default

Deactivation

Value

Value

Switch of Fast Return to UCelInfoFDD.dch2Fach RetLteSw

EUTRAN for PS Only when UE RRC Status

OFF

OFF

OFF

OFF

OFF

OFF

Transferring from CELL_DCH to CELL_FACH Switch of Fast Return to EUTRAN for PS when UE

UExtCelInfoFDD.pchIdle

RRC Status Transferring to

RetLteSw

PCH/IDLE (CELL_PCH/URA_PCH/idl e)

UExtCelInfoFDD.

PS in CELL_DCH Blind

dchPsBldRedLteSw

Fast Return to LTE Switch

For the above parameters’ description and configuration, please refer to chapter 6.2.

6.5

Impact on the Network

6.5.1

ZWF21-03-111 Fast Return to LTE 

Advantages of this feature: Because the UEs supporting LTE will be handed over to LTE as far as possible, the number of the attempted handover and redirection will be increased, and the users experience will be improved.



Disadvantages of this feature: None

6.5.2

ZWF21-03-112 Packet Service Fast Return to LTE for Inactive Mode 

Advantages of this feature:


67

Fast Return to LTE

Because the UEs supporting LTE will be handed over to LTE as far as possible, the number of the attempted handover and redirection will be increased, and the users experience will be improved. 

Disadvantages of this feature: None

6.5.3

ZWF21-03-113 Packet Service Fast Return to LTE for Active Mode 

Advantages of this feature: Because the UEs supporting LTE will be handed over to LTE as far as possible, the number of the attempted handover and redirection will be increased, and the users experience will be improved.



7

Disadvantages of this feature:

Abbreviation Abbreviation

Full Name rd

3GPP

3 Generation Partnership Project

CS

Circuit Switch

CSFB

Circuit Switched Fallback

EUTRAN

Evolved Universal Terrestrial Radio Access Network

KPI

Key Performance Indicator

LTE

Long Term Evolution

PS

Packet Switch

RNC

Radio Network Controller

SRNC

Serving Radio Network Controller

SRVCC

Single Radio Voice Call Continuity

UMTS

Universal Mobile Telecommunications System

UTRAN

Universal Terrestrial Radio Access Network


68

ZTE - Fast Return to LTE

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