Call Reestablishment(RAN15.0 06)

WCDMA RAN

Call Reestablishment FeatureParameter Description

Issue 06Date 2015-08-30

HUAWEI TECHNOLOGIES CO., LTD.

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Issue 06 (2015-08-30) Huawei Proprietary and ConfidentialCopyright Huawei Technologies Co., Ltd.

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Contents

1 About This Document..................................................................................................................11.1 Scope..............................................................................................................................................................................11.2 Intended Audience..........................................................................................................................................................11.3 Change History...............................................................................................................................................................11.4 Differences Between Base Station Types.......................................................................................................................82 Overview.........................................................................................................................................92.1 Introduction....................................................................................................................................................................92.2 Benefits...........................................................................................................................................................................92.3 Architecture..................................................................................................................................................................93 Uplink RL Out of Synchronization..........................................................................................133.1 Uplink RL Out of Synchronization Detection..............................................................................................................133.1.1 Detection Principle....................................................................................................................................................133.1.2 Switches for Call Reestablishment Triggered by an RL Out-of-Synchronization Problem......................................143.2 Call Reestablishment....................................................................................................................................................173.2.1 Triggering..................................................................................................................................................................173.2.2 Implementation..........................................................................................................................................................193.2.3 CELL_DCH-to-CELL_PCH Reconfiguration and Reestablishment........................................................................214 SRB Reset......................................................................................................................................234.1 SRB Reset Detection....................................................................................................................................................234.1.1 Detection Principle....................................................................................................................................................234.1.2 Switches for Call Reestablishment Triggered by an SRB Reset...............................................................................234.2 Call Reestablishment....................................................................................................................................................254.2.1 Triggering..................................................................................................................................................................264.2.2 Implementation..........................................................................................................................................................265 TRB Reset......................................................................................................................................275.1 TRB Reset Detection....................................................................................................................................................275.1.1 Detection Principle....................................................................................................................................................275.1.2 Switches for Call Reestablishment Triggered by a TRB Reset.................................................................................275.2 Call Reestablishment....................................................................................................................................................285.2.1 Triggering..................................................................................................................................................................285.2.2 Implementation..........................................................................................................................................................28

WCDMA RANCall Reestablishment Feature Parameter Description Contents


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5.2.3 CELL_DCH-to-CELL_PCH Reconfiguration and Reestablishment........................................................................296 Air-Interface Process Timeout..................................................................................................306.1 Air-Interface Process Timeout Detection.....................................................................................................................306.1.1 Radio Bearer Setup Timeout.....................................................................................................................................306.1.2 Radio Bearer Release Timeout of PS Services..........................................................................................................346.1.3 Radio Bearer Reconfiguration Timeout....................................................................................................................386.1.4 Physical Channel Reconfiguration Timeout..............................................................................................................406.1.5 Security Mode Setup Timeout...................................................................................................................................416.2 Call Reestablishment....................................................................................................................................................437 Air-interface Process Overlap...................................................................................................447.1 Air-Interface Process Overlap Detection......................................................................................................................447.1.1 Radio Bearer Setup Overlap......................................................................................................................................447.1.2 Radio Bearer Release Overlap of PS Services..........................................................................................................467.1.3 Radio Bearer Reconfiguration Overlap.....................................................................................................................477.1.4 Physical Channel Reconfiguration Overlap..............................................................................................................477.1.5 Security Mode Setup Overlap....................................................................................................................................487.2 Call Reestablishment....................................................................................................................................................508 Related Features...........................................................................................................................519 Network Impact...........................................................................................................................5210 Engineering Guidelines...........................................................................................................5410.1 When to Use Call Reestablishment............................................................................................................................5410.2 Required Information.................................................................................................................................................5410.3 Planning......................................................................................................................................................................5510.4 Deployment................................................................................................................................................................5510.4.1 Requirements...........................................................................................................................................................5510.4.2 Data Preparation......................................................................................................................................................5610.4.3 Activation................................................................................................................................................................6210.4.4 Activation Observation............................................................................................................................................6810.4.5 Deactivation.............................................................................................................................................................6810.5 Performance Monitoring.............................................................................................................................................7310.6 Parameter Optimization..............................................................................................................................................7510.7 Troubleshooting..........................................................................................................................................................7511 Parameters...................................................................................................................................7612 Counters....................................................................................................................................18513 Glossary.....................................................................................................................................18614 Reference Documents.............................................................................................................187

WCDMA RANCall Reestablishment Feature Parameter Description Contents


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1 About This Document1.1 Scope

This document describes the WRFD-140103 Call Reestablishment, including its technicalprinciples, related features, network impact, and engineering guidelines.This document applies to the following NE types.

NE Type NE ModelRNC BSC6900, BSC6910NodeB Macro 3900 series macro base stations: BTS3900, BTS3900A,

BTS3900L, BTS3900AL, DBS3900, BTS3900C3800 series macro base stations: DBS3800, BTS3812E,BTS3812AE

Micro BTS3803E, BTS3902ELampSite DBS3900 LampSite

1.2 Intended AudienceThis document is intended for personnel who:l Need to understand the features described hereinl Work with Huawei products

1.3 Change HistoryThis section provides information about the changes in different document versions.There aretwo types of changes, which are defined as follows:

WCDMA RANCall Reestablishment Feature Parameter Description 1 About This Document


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l Feature changeChanges in features of a specific product version

l Editorial changeChanges in wording or addition of information that was not described in the earlier version

RAN15.0 06 (2015-08-30)This issue includes the following changes.

ChangeType

Change Description Parameter Change

Featurechange

None None

Editorialchange

l Added descriptions of RBreconfiguration for DCCC. For details,see 2.3 Architecture.

l Added counters in 9 Network Impactto indicate the impact of callreestablishment on CS user experience.

None


ChangeType


Featurechange

Added the CELL_DCH-to-CELL_PCHreconfiguration and reestablishmentfunction. For details, see the followingsections:l 3.2.3 CELL_DCH-to-CELL_PCH

Reconfiguration and Reestablishmentl 5.2.3 CELL_DCH-to-CELL_PCH

Reconfiguration and Reestablishmentl 10.4.3 Activation

AddedRESERVED_SWITCH_10_BIT19 to the RsvSwitch10(BSC6900,BSC6910)parameter.

Modified 7.2 Call Reestablishment.Editorialchange

Optimized descriptions in 10.5 PerformanceMonitoring.

None




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ChangeType

Change Description ParameterChange

Featurechange

None None

Editorialchange

Optimized descriptions in the following sections:l 3.2.2 Implementationl 10.2 Required Information

None

Optimized figures in 6 Air-Interface Process Timeout. None


ChangeType

Change Description ParameterChange

Featurechange

None None

Editorialchange

l Optimized descriptions in the following sections: 2.3Architecture, 3 Uplink RL Out ofSynchronization, 4 SRB Reset, 5 TRB Reset, and 6Air-Interface Process Timeout

l Optimized figures in this document.

None




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ChangeType


Featurechange

l For CS services, added the triggeringprocesses: security mode setup, radiobearer reconfiguration, and physicalchannel reconfiguration during a servingcell update; added the "air-interfaceprocess timeout" and "air-interfaceprocess overlap" causes to the process"physical channel reconfiguration forinter RNC-UE timer relationshipadjustment when a UE reports event 6Gor 6F."

l For PS services, added the triggeringprocess: security mode setup.For details, see Table 2-1.

None

Editorialchange

Added the description of callreestablishment triggered by radio bearerreconfiguration timeout during the dynamicchannel configuration control (DCCC)procedure. For details, see 6.1.3 RadioBearer Reconfiguration Timeout.

AddedRBRECFG_ENH_RL_REEST_SWITCH to thePROCESSSWITCH4(BSC6900,BSC6910)parameter.

Added the description of callreestablishment triggered by radio bearerreconfiguration timeout during proceduresother than DCCC. For details, see 6.1.3Radio Bearer Reconfiguration Timeout.

AddedNON_DCCC_RBRECFG_RL_REEST_SWITCH to theImprovementSwitch(BSC6900,BSC6910)parameter.

Added the description of callreestablishment triggered by physicalchannel reconfiguration timeout. Fordetails, see 6.1.4 Physical ChannelReconfiguration Timeout.

AddedRNCAP_PHYCHRECFG_ENH_RL_REEST_SWITCHto the PROCESSSWITCH4(BSC6900,BSC6910)parameter.

Added the description of callreestablishment triggered by security modesetup timeout. For details, see 6.1.5 SecurityMode Setup Timeout.

AddedSMC_RL_REEST_SWITCH to the ImprovementSwitch(BSC6900,BSC6910)parameter.



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ChangeType


Added the description of callreestablishment triggered when the UE doesnot acknowledge a Physical ChannelReconfiguration or a Security ModeCommand message. For details, see 7.1.4Physical Channel ReconfigurationOverlap and 7.1.5 Security Mode SetupOverlap.

None

Modified steps in 10.4.3 Activation and10.4.5 Deactivation based on the precedingfeature changes.

None

RAN15.0 01 (2013-04-28)This issue does not include any changes.

RAN15.0 Draft A (2013-01-30)Compared with Issue 02 (2012-07-20) of RAN14.0, Draft A (2013-01-30) of RAN15.0 includesthe following changes.

ChangeType


Featurechange

Added description of callreestablishment triggered by TRBreset. For details, see 5 TRB Reset.

AddedTRB_RESET_RL_REEST_SWITCH to the PROCESSSWITCH4(BSC6900,BSC6910) parameter.

Added description of callreestablishment triggered by air-interface process timeout. Fordetails, see 6 Air-Interface ProcessTimeout.

Added the following parameters:l RbRelRspTmr

(BSC6900,BSC6910)l PROCESSSWITCH4

(BSC6900,BSC6910):RB_REL_RL_REEST_SWITCH



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ChangeType


Added the following scenarios forcall reestablishment triggered by air-interface process overlap: The ACKmessage is received but the messageindicating the process is complete isnot received. The Radio BearerRelease message is sent to a UEprocessing PS services. For details,see 7.1 Air-Interface ProcessOverlap Detection.

Added the following parameters:l RbRelRspTmr

(BSC6900,BSC6910)l PROCESSSWITCH4

(BSC6900,BSC6910):RB_REL_RL_REEST_SWITCH

Added switches controlling callreestablishment triggered by thefollowing processes:l Inter-RAT handoverl Active set updatel Measurement controll RB setupl RB releasel Packet data unit (PDU sending

Added the following parameters:l PROCESSSWITCH4

(BSC6900,BSC6910):IRATHO_HOCANCEL_RL_REEST_SWITCH

l OptimizationSwitch(BSC6900,BSC6910):ASU_RL_RESET_SWITCH

l OptimizationSwitch(BSC6900,BSC6910):MC_RL_RESET_SWITCH

l PROCESSSWITCH4(BSC6900,BSC6910):RB_SETUP_ENHANCE_RL_REEST_SWITCH

l PROCESSSWITCH4(BSC6900,BSC6910):RB_REL_RL_REEST_SWITCH

l PROCESSSWITCH4(BSC6900,BSC6910):TRB_RESET_RL_REEST_SWITCH



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ChangeType


None l Changed RsvdPara1(BSC6900,BSC6910):RSVDBIT1_BIT24 toOptimizationSwitch(BSC6900,BSC6910):CS_RL_SETUP_SWITCH.

l Changed RsvdPara1(BSC6900,BSC6910):RSVDBIT1_BIT25 toOptimizationSwitch(BSC6900,BSC6910):PS_RL_SETUP_SWITCH.

l Changed ReservedSwitch1:RESERVED_SWITCH_1_BIT14 to OptimizationSwitch(BSC6900,BSC6910):RB_RECFG_RL_REEST_SWITCH.

l Changed RsvdPara1:RSVDBIT1_BIT23 toOptimizationSwitch(BSC6900,BSC6910):RLFAIL_RL_SETUP_SWITCH.

l Changed RsvdPara1(BSC6900,BSC6910):RSVDBIT1_BIT22 toOptimizationSwitch(BSC6900,BSC6910):SRB_RESET_RL_SETUP_SWITCH.

l Changed RsvdPara1(BSC6900,BSC6910):RSVDBIT1_BIT28 toOptimizationSwitch(BSC6900,BSC6910):RL_RESTORE_SWITCH.

l Changed RsvdPara2(BSC6900,BSC6910) toCSRLReEstCellUpdateTmr(BSC6900,BSC6910).

l Changed RsvdPara3(BSC6900,BSC6910) toPSRLReEstCellUpdateTmr(BSC6900,BSC6910).



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ChangeType


l Changed RsvdPara1(BSC6900,BSC6910):RSVDBIT1_BIT26 toOptimizationSwitch(BSC6900,BSC6910):UE_SRB_RESET_SWITCH.

Editorialchange

Added description of CMEconfiguration. For details, see 10.4Deployment.

None

1.4 Differences Between Base Station TypesFeature Support by Macro, Micro, and LampSite Base Stations

FeatureID

Description

Supported byController(Y/N/NA)

Supported byMacro(Y/N/NA)

Supported by Micro(Y/N/NA)

LampSite

BSC6900

BSC6910

BTS3803E

BTS3902E

WRFD-140103

CallReestablishment

Y Y Y Y Y Y

NOTE

Y indicates that a feature is supported; N indicates that a feature is not supported; NA indicates that an NE isnot involved, that is, a feature does not require the support of the NE.

The features described in this document are implemented in the same way on macro, micro, andLampSite base stations.



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2 Overview2.1 Introduction

Call reestablishment is a function by which radio links (RLs) are reestablished when a serviceinterruption or an access failure occurs in temporary coverage holes and in tunnels, elevators,and buildings that cause significant signal quality fluctuation.Call reestablishment can be initiated by a UE or the RAN.l Call reestablishment initiated by a UE: The UE sends a call reestablishment request to the

network to restore services upon detecting a downlink RL out-of-synchronization problemor a signaling radio bearer (SRB) reset.

l Call reestablishment initiated by the RAN: After the RAN detects a service interruption oran access failure (possibly due to a signaling radio bearer (SRB) reset or an uplink RL out-of-synchronization problem) before the UE does, the RAN stops the UE's downlink RLsets to enable the UE to detect downlink RL out-of-synchronization problem as soon aspossible. Upon detecting a downlink RL out-of-synchronization problem, the UE sends acall reestablishment request to the RAN to restore services.

This document describes only call reestablishment initiated by the RAN.

2.2 BenefitsCall reestablishment initiated by the RAN improves user experience.

2.3 ArchitectureCauses That Can Trigger Call Reestablishment

The causes that can trigger call reestablishment after a service interruption or an access failureare as follows:l RL out-of-synchronization probleml SRB reset

WCDMA RANCall Reestablishment Feature Parameter Description 2 Overview


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l PS TRB resetl Air interface process timeoutl Air interface process overlap

Processes That Can Trigger Call ReestablishmentThe preceding causes for service interruption or access failures mainly occur in the followingprocesses:l Soft handoverl Physical channel reconfiguration

Physical channel reconfiguration during hard handovers Physical channel reconfiguration for the starting of the compressed mode Physical channel reconfiguration during code tree reshuffling Physical channel reconfiguration during serving cell updates Physical channel reconfiguration for inter RNC-UE timer relationship adjustment when

a UE reports event 6G or 6F Physical channel reconfiguration during power adjustments for HSUPA channels

l Inter-RAT handoverl RB setupl RB releasel RB reconfiguration

DCCC RB reconfiguration consists of the following procedures: Hybrid automatic repeat request (HARQ) power offset (PO) reconfiguration Dynamic channel configuration control (DCCC) triggered by HSPA retry DCCC triggered by TTI switching DCCC triggered by HSPA+ feature removal after the RAB is released DCCC triggered by fallback from DC-HSUPA to SC-HSUPA DCCC triggered by channel fallback DCCC triggered by event 4A or 4B DCCC triggered by coverage-based channel switching from E-DCH to DCH Best effort (BE) service downspeeding triggered by load reshuffling DCCC triggered by feature fallback

l Measurement control command issuingl PS data transmissionl Security mode setupBefore releasing RLs due to any of the causes, the RAN detects the service interruption or accessfailure and initiates call reestablishment.

Mapping Between Service Types, Triggering Processes, and Triggering CausesTable 2-1 provides the mapping between service types, triggering processes, and triggeringcauses.



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Table 2-1 Mapping between service types, triggering processes, and triggering causesServiceType

TriggeringProcess

RL out-of-synchronizationproblem

SRBreset

PS TRBreset

Airinterfaceprocesstimeout

Airinterfaceprocessoverlap

CS/PS Soft handover Physicalchannelreconfiguration

Hardhandover

Compressedmodesetup

Codetreereshuffling

(onlyfor CSservices)


Servingcellupdate

Physicalchannelreconfigurationfor interRNC-UE timerrelationshipadjustment when aUEreportsevent 6Gor 6F



Inter-RAT handover RB setup RB reconfiguration Measurement controlcommand issuing



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ServiceType

TriggeringProcess

RL out-of-synchronizationproblem

SRBreset

PS TRBreset

Airinterfaceprocesstimeout

Airinterfaceprocessoverlap

Security mode setup PS Power adjustments

for HSUPA channels

PS data transmission RB release

NOTE

The cause "RL out-of-synchronization problem" can trigger call reestablishment in processes not listed inTable 2-1.The other causes can trigger call reestablishment only in processes listed in Table 2-1.After you select UE_DCH_CU_RL_REEST_SWITCH under the OptimizationSwitch7(BSC6900,BSC6910) parameter, the RNC performs call reestablishment after receiving a CELL UPDATEmessage from a UE with the cause value Radio Link Failure or RLC Unrecoverable Error as a response toone of the following messages delivered by the RNC:You are also advised to select the PSREL_DUETO_CSFAIL_OPTIMIZE_SWITCH check box underthe OptimizationSwitch(BSC6900,BSC6910) parameter to ensure the call drop rate benefits provided byturning on the UE_DCH_CU_RL_REEST_SWITCH.

Service/Process/Cause Switches of Call ReestablishmentCall reestablishment is controlled by the following switches:l Service switches

Service switches include a CS service switch and a PS service switch. Enable a serviceswitch before enabling a process or cause switch.

l Process switchesAll triggering processes listed in Table 2-1 except PS data transmission have a switch.

l Cause switchesAll causes except "Air interface process timeout" have a switch.

Call reestablishment can be triggered only when required switches are enabled.For details about service/process/cause switches of call reestablishment, see descriptions in thefollow-up chapters.



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3 Uplink RL Out of Synchronization3.1 Uplink RL Out of Synchronization Detection3.1.1 Detection Principle

The NodeB monitors uplink RL quality. If the number of "out-sync" indications received by theNodeB reaches the value of the NOUTSYNCIND(BSC6910,BSC6900) parameter, the NodeBstarts the TRlFailure(BSC6900,BSC6910) timer. How the detection process continues dependson the situation:l If the number of "in-sync" indications received by the NodeB reaches the value of the

NINSYNCIND(BSC6900,BSC6910) parameter before the TRlFailure(BSC6900,BSC6910) timer expires, the NodeB stops and resets the TRlFailure(BSC6900,BSC6910) timer.

l If the number of "in-sync" indications received by the NodeB does not reach the value ofthe NINSYNCIND(BSC6900,BSC6910) parameter before the TRlFailure(BSC6900,BSC6910) timer expires, the NodeB considers that an RL out-of-synchronization problem has occurred and identifies the RL set where the problem islocated. (An RL set contains all the RLs of a UE under a NodeB.)

NOTE

l The default value of NOUTSYNCIND(BSC6900,BSC6910) is 50 and NINSYNCIND(BSC6900,BSC6910) is 5.

l The higher the value of the NOUTSYNCIND(BSC6900,BSC6910) parameter, the harder it will be forRL out-of-synchronization problems to be triggered. The higher the value of the NINSYNCIND(BSC6900,BSC6910) parameter, the harder it will be for RLs to be synchronized. If either parameteris set to a high value, RLs may stay on the verge of RL out-of-synchronization problem for a long time,and user experience will be poor for both CS and PS services. Set NOUTSYNCIND(BSC6900,BSC6910) to a value smaller than the default one and NINSYNCIND(BSC6900,BSC6910) to a value higher than the default one. This way, RL out-of-synchronizationproblems are easily triggered for call reestablishment to improve user experience.

When a UE's uplink RL sets are all out of synchronization, the events that occur depend on thesituation:

WCDMA RANCall Reestablishment Feature Parameter Description 3 Uplink RL Out of Synchronization


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l When the call reestablishment function is not enabled, the call drops or the UE access finallyfails.

l When the call reestablishment function is enabled, the RNC activates a synchronizationtimer. If the NodeB does not detect uplink RL synchronization before the timer expires,call reestablishment is initiated.

Table 3-1 shows the mapping between services, OptimizationSwitch(BSC6900,BSC6910):RL_RESTORE_SWITCH switch status, and synchronization timers.

Table 3-1 Mapping between services, OptimizationSwitch:RL_RESTORE_SWITCH status,and synchronization timers

Service OptimizationSwitch(BSC6900,BSC6910):RL_RESTORE_SWITCHSwitch Status

Synchronization Timer

CS services Off RlRstrTmr(BSC6900,BSC6910)On T313(BSC6900,BSC6910)

PS services Any RlRstrTmr(BSC6900,BSC6910)

NOTE

l Enable the OptimizationSwitch(BSC6900,BSC6910):RL_RESTORE_SWITCH switch for CSservices so that uplink and downlink RLs are monitored by the same synchronization timer.

l When the OptimizationSwitch(BSC6900,BSC6910):RL_RESTORE_SWITCH switch is enabled,the synchronization timer used to initiate RL establishment is RlRstrTmr(BSC6900,BSC6910). TheT313(BSC6900,BSC6910) timer is used only when the UE's RL sets are all out of synchronization.

3.1.2 Switches for Call Reestablishment Triggered by an RL Out-of-Synchronization Problem

To enable the call reestablishment function triggered by an RL out-of-synchronization problem,enable the service, process, and cause switches listed in Table 3-2.

NOTE

Call reestablishment can be triggered by the RL out-of-synchronization problem, either in correspondingprocesses or not in corresponding processes. Therefore, when the process switches are not turned on, callreestablishment can be triggered by the RL out-of-synchronization problem, but cannot be triggered in thecorresponding processes.



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Table 3-2 Switches for call reestablishment triggered by an RL out-of-synchronization problemService Switch Process Switch Cause SwitchSwitch for CS services:CS_RL_SETUP_SWITCHunder the OptimizationS-witch(BSC6900,BSC6910)parameter

l Call reestablishmentduring an inter-RAThandover is controlled byIRATHO_HOCANCEL_RL_REEST_SWITCH under thePROCESSSWITCH4(BSC6900,BSC6910)parameter.

l Call reestablishmentduring a soft handover iscontrolled byASU_RL_RESET_SWITCH under theOptimizationSwitch(BSC6900,BSC6910)parameter.

l Call reestablishmentduring physical channelreconfiguration iscontrolled byPHY_RECFG_REEST_SWITCH under thePROCESSSWITCH4(BSC6900,BSC6910)parameter.

l Call reestablishmentduring RBreconfiguration in theDCCC procedure iscontrolled byRB_RECFG_RL_REEST_SWITCH under theOptimizationSwitch(BSC6900,BSC6910)parameter.

l Call reestablishmentduring RBreconfiguration inprocedures other thanDCCC is controlled byNON_DCCC_RBRECFG_RL_REEST_SWITCH under theImprovementSwitch

RLFAIL_RL_SETUP_SWITCH under theOptimizationSwitch(BSC6900,BSC6910)parameter



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Service Switch Process Switch Cause SwitchSwitch for PS services:PS_RL_SETUP_SWITCHunder the OptimizationS-

(BSC6900,BSC6910)parameter.

l Call reestablishmentduring security modesetup is controlled by theSMC_RL_REEST_SWITCH under theImprovementSwitch



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Service Switch Process Switch Cause Switchwitch(BSC6900,BSC6910)parameter

(BSC6900,BSC6910)parameter.

NOTE

l The switch for CS+PS combined services is the same as that for CS services.l When call reestablishment is triggered for CS+PS combined services, calls are reestablished for both

CS and PS services.

3.2 Call Reestablishment3.2.1 Triggering

Call reestablishment triggered by an uplink RL out-of-synchronization problem can beperformed under the same RNC or under different RNCs over the Iur interface.

Under the Same RNCAs mentioned in section 3.1 Uplink RL Out of Synchronization Detection, if the NodeB doesnot detect uplink RL synchronization before the RlRstrTmr(BSC6900,BSC6910) or T313(BSC6900,BSC6910) timer expires, the RNC sends to the NodeB the Radio Link ActivationCommand message containing the information element (IE) "deactivate." Upon receiving themessage, the NodeB stops downlink power transmission for the UE's RL sets. Then, the RNCstarts the timers for call reestablishment (CSRLReEstCellUpdateTmr(BSC6900,BSC6910)timer for CS services and PSRLReEstCellUpdateTmr(BSC6900,BSC6910) timer for PSservices).l If the RNC does not receive the Cell Update message from the UE before the timers expire,

the call drops or UE access fails.l If the RNC receives the Cell Update message from the UE before the timers expire, the

RNC stops the timers and initiates call reestablishment.Figure 3-1 shows the signaling procedure for call reestablishment triggered by an uplink RLout-of-synchronization problem under the same RNC.



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Figure 3-1 Call reestablishment triggered by an uplink RL out-of-synchronization problemunder the same RNC

Under Different RNCs over the Iur InterfaceCall reestablishment under different RNCs is controlled by thePROCESSSWITCH4(BSC6900,BSC6910):IUR_RL_REEST_SWITCH.Figure 3-2 shows the signaling procedure for call reestablishment triggered by an uplink RLfailure under different RNCs over the Iur interface.



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Figure 3-2 Call reestablishment triggered by an uplink RL out-of-synchronization problemunder different RNCs over the Iur interface

Call reestablishment triggered by an uplink RL out-of-synchronization problem under the sameRNC is similar to that triggered by an uplink RL out-of-synchronization problem under differentRNCs. The main differences between the two processes are as follows:l In the former process, the RNC sends the Radio Link Activation Command to the NodeB.l In the latter process, the SRNC sends the Radio Link Deletion Request message to the

DRNC, and upon receiving the Radio Link Deletion Response message from the NodeB,the DRNC waits for the UE's Cell Update message.

In Figure 3-2, NodeB (Cell A) is under the SRNC and NodeB (Cell B) is under the DRNC.Before the uplink RL out-of-synchronization problem, the UE has established an RL with eachNodeB. After the uplink RL out-of-synchronization problem, the UE attempts to establish a newRL only with NodeB (Cell B).

3.2.2 ImplementationFigure 3-3 shows how call establishment is implemented.



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Figure 3-3 Flowchart for call reestablishment

The call reestablishment process is implemented as follows:1. After the NodeB stops downlink power transmission for a UE's RLs, the UE starts the T313

(BSC6900,BSC6910) timer if the number of "out-sync" indications received consecutivelyfrom Layer 1 reaches the value of the N313(BSC6900,BSC6910) parameter.



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NOTE

The higher the value of the N313(BSC6900,BSC6910) parameter, the harder it will be for the UE todetect an RL out-of-synchronization problem and the longer the UE may stay on the verge of RLout-of-synchronization problem.

2. If the number of "in-sync" indications received consecutively from Layer 1 does not reachthe value of the N315(BSC6900,BSC6910) parameter before the T313(BSC6900,BSC6910) timer expires, the UE transmits the Cell Update message with thecause value "Radio Link Failure" to the RNC for call reestablishment. Meanwhile, the UEstarts the T302(BSC6900,BSC6910) timer as well as the T314(BSC6900,BSC6910) timerfor CS services or the T315(BSC6900,BSC6910) timer for PS services.

3. If the UE does not receive the Cell Update Confirm message from the RAN side after theT302(BSC6900,BSC6910) timer expires, the UE retransmits the Cell Update message untilthe T314(BSC6900,BSC6910)/T315(BSC6900,BSC6910) timer expires: (The number ofretransmissions is determined by the value of the T302(BSC6900,BSC6910) parameter.)

l If faulty RLs are restored before T314(BSC6900,BSC6910)/T315(BSC6900,BSC6910)expires, the call reestablishment is successful. Interrupted services are restored or UE accesssucceeds.

l If faulty RLs are not restored before T314(BSC6900,BSC6910)/T315(BSC6900,BSC6910) expires, the call reestablishment fails. Services are released or UEaccess fails.

NOTE

Set the T313(BSC6900,BSC6910), N313(BSC6900,BSC6910), N315(BSC6900,BSC6910), and T314(BSC6900,BSC6910) parameters so that UEs can quickly detect RL out-of-synchronization problem.Set the timer for RAB assignment on the CN side during call reestablishment to a value greater than theRB setup response timer (RbSetupRspTmr(BSC6900,BSC6910)) plus the timerCSRLReEstCellUpdateTmr(BSC6900,BSC6910) (for CS services) or PSRLReEstCellUpdateTmr(BSC6900,BSC6910) (for PS services).Set the security mode response timer on the CN side to a value greater than the security mode timer(RRCSECRTMODECMPTMR(BSC6900,BSC6910)) plus the timer T314(BSC6900,BSC6910) on theRNC side.Set the timer for a response to the Relocation Command message that is sent by the CN during inter-RAThandovers to a value greater than the call reestablishment timer.l For CS services, set the timer to a value greater than CSRLReEstCellUpdateTmr

(BSC6900,BSC6910).l For PS services, set the timer to a value greater than PSRLReEstCellUpdateTmr

(BSC6900,BSC6910).

3.2.3 CELL_DCH-to-CELL_PCH Reconfiguration andReestablishment

When both the switch for triggering call reestablishment upon an RL out-of-synchronizationproblem and the switch (RsvSwitch10(BSC6900,BSC6910):RESERVED_SWITCH_10_BIT19) for triggering a CELL_DCH-to-CELL_PCH (D2P)reconfiguration and reestablishment procedure upon an RL out-of-synchronization problem areturned on and the following conditions are met for a fast-dormancy UE performing a single PSservice, a D2P state transition instead of a call reestablishment process is triggered for the UE.l The network side receives the RADIO LINK FAILURE INDICATION message from the

NodeB.



21

l Synchronization times out.After a UE who has only one radio link receives a RADIO LINK FAILURE INDICATIONmessage, it waits for recovery of the radio link's synchronization. The timer used in thiscase is specified by bits 24 to 31 of the RsvU32Para4(BSC6900,BSC6910) parameter inthe RNC MML command SET UALGORSVPARA.After a UE who has multiple radio links receives a RADIO LINK FAILURE INDICATIONmessage, it waits for recovery of the radio links' synchronization. The timer used in thiscase is specified by the value of the RlRstrTmr(BSC6900,BSC6910)parameter in the RNCMML command SET USTATETIMER.

l The best cell is under the SRNC and there is no CS signaling.The UE transits to the common channel. Then, according to the traffic volume, it transits to adedicated channel to finish the call reestablishment. If an SRB resets during the D2P statetransition, the call reestablishment is performed in the same way as that performed during anSRB reset.If there is data in the RLC buffer after the D2P state transition is successful, you can run theRNC MML command SET UALGORSVPARA with RESERVED_SWITCH_5_BIT13under RsvSwitch5(BSC6900,BSC6910) set to 0 and run the RNC MML command SETURRCTRLSWITCH with F2P_DATATRANS_OPTIMIZE_SWITCH underPROCESSSWITCH4(BSC6900,BSC6910) set to 1 to send paging messages to the UE again.CELL_DCH-to-CELL_PCH reconfiguration and reestablishment is not triggered for thefollowing blacklisted UEs:l UEs for which FD_TAC_FORCE_D2F_SWITCH is set to 1l UEs for which PCH_DISABLED_SWITCH is set to 1l UEs for which SPECUSER_EFACH_DISABLED_SWITCH is set to 1l UEs for which SPECUSER_ERACH_DISABLED_SWITCH is set to 1l UEs for which RESERVED_SWITCH_BIT1 under RsvSwitch(BSC6900,BSC6910) is

set to 1



22

4 SRB Reset4.1 SRB Reset Detection

4.1.1 Detection PrincipleThe RNC sends a message in acknowledged mode (AM) to a UE. However, the RNC does notreceive an ACK message from the UE before the number of SRB RLC PDU retransmissionsreaches the value of the NoDiscardMaxDAT(BSC6900,BSC6910) parameter. If theAMRlcDiscardMode(BSC6900,BSC6910) parameter is set to NO_DISCARD, the RNCtriggers an SRB reset and sends the Reset PDU message to the UE to reestablish RLC entitieson both sides. Then one of the following occurs:l If the call reestablishment function is not enabled, the RNC sends the Iu Release Request

message to the core network.l If the call reestablishment function is enabled, call reestablishment is triggered.

4.1.2 Switches for Call Reestablishment Triggered by an SRB ResetTo enable the call reestablishment function triggered by an SRB reset, enable the service,process, and cause switches listed in Table 4-1.

Table 4-1 Switches for call reestablishment triggered by an SRB resetService Switch Process Switch Cause SwitchSwitch for CS services:CS_RL_SETUP_SWITCHunder the OptimizationS-witch(BSC6900,BSC6910)parameter

l Call reestablishment during aninter-RAT handover is controlledbyIRATHO_HOCANCEL_RL_REEST_SWITCH under thePROCESSSWITCH4(BSC6900,BSC6910)parameter.

OptimizationSwitch(BSC6900,BSC6910):SRB_RESET_RL_SETUP_SWITCH

WCDMA RANCall Reestablishment Feature Parameter Description 4 SRB Reset


23

Service Switch Process Switch Cause SwitchSwitch for PS services:PS_RL_SETUP_SWITCHunder the OptimizationS-

l Call reestablishment during asoft handover is controlled byASU_RL_RESET_SWITCHunder the OptimizationSwitch(BSC6900,BSC6910)parameter.

l Call reestablishment duringmeasurement control iscontrolled byMC_RL_RESET_SWITCHunder the OptimizationSwitch(BSC6900,BSC6910)parameter.

l Call reestablishment duringphysical channel reconfigurationis controlled byPHY_RECFG_REEST_SWITCH under thePROCESSSWITCH4(BSC6900,BSC6910)parameter.

l Call reestablishment during RBsetup is jointly controlled byRB_SETUP_RL_REEST_SWITCH andRB_SETUP_ENHANCE_RL_REEST_SWITCH under thePROCESSSWITCH4(BSC6900,BSC6910)parameter.

l Call reestablishment during RBrelease is controlled byRB_REL_RL_REEST_SWITCH under thePROCESSSWITCH4(BSC6900,BSC6910)parameter. (This switch appliesto a single PS service orcombined services that includePS services.)

l Call reestablishment during RBreconfiguration in the DCCCprocedure is controlled byRB_RECFG_RL_REEST_SWITCH under theOptimizationSwitch(BSC6900,BSC6910)



24

Service Switch Process Switch Cause Switchwitch(BSC6900,BSC6910)parameter

parameter. (This switch appliesto a single PS service orcombined services that includePS services.)

l Call reestablishment during RBreconfiguration in proceduresother than DCCC is controlled byNON_DCCC_RBRECFG_RL_REEST_SWITCH under theImprovementSwitch(BSC6900,BSC6910)parameter.

l Call reestablishment duringsecurity mode setup is controlledby theSMC_RL_REEST_SWITCHunder the ImprovementSwitch(BSC6900,BSC6910)parameter.

NOTE


CS and PS services.

After you enable the process switch, change the length of the process timer so that callreestablishment is more likely to be triggered by an SRB reset. The following table lists themapping between processes and timers.

Table 4-2 Mapping between processes and timersProcess TimerSoft handover HoAsuTmr(BSC6900,BSC6910)Physical channel reconfiguration HoPhychRecfgTmr(BSC6900,BSC6910)RB reconfiguration RbRecfgRspTmr(BSC6900,BSC6910)RB setup RbSetupRspTmr(BSC6900,BSC6910)

4.2 Call Reestablishment



25

4.2.1 TriggeringFigure 4-1 shows the signaling procedure for call reestablishment triggered by an SRB reset.

Figure 4-1 Call reestablishment triggered by an SRB reset

4.2.2 ImplementationExcept that the trigger cause is different, the process of call reestablishment triggered by an SRBreset is the same as that triggered by an RL out-of-synchronization problem. For details, see3.2.2 Implementation.



26

5 TRB Reset5.1 TRB Reset Detection5.1.1 Detection Principle

The RNC sends an AM PDU to a UE initiating PS services in the CELL_DCH state. If the RNCdoes not receive a response from the UE, a TRB reset is triggered. Then one of the followingoccurs:l If the call reestablishment function is not enabled, the RNC sends the Iu Release Request

message to the core network and the UE's PS services are interrupted.l If the call reestablishment function is enabled, the RNC does not send the Iu Release

Request message to the core network and call reestablishment is triggered. After the callreestablishment, the UE is still in the CELL_DCH state.

5.1.2 Switches for Call Reestablishment Triggered by a TRB ResetTo enable the call reestablishment function in this scenario, enable the service and processswitches listed in Table 5-1.

Table 5-1 Switches for call reestablishment triggered by a TRB resetService Switch Process Switch Cause SwitchThe PS service is controlled byOptimizationSwitch(BSC6900,BSC6910):PS_RL_SETUP_SWITCH.

None PROCESSSWITCH4(BSC6900,BSC6910):TRB_RESET_RL_REEST_SWITCH

NOTE

Call reestablishment triggered by a TRB reset applies only to a single PS service of a UE in the CELL_DCHstate.

WCDMA RANCall Reestablishment Feature Parameter Description 5 TRB Reset


27

5.2 Call Reestablishment5.2.1 Triggering

Figure 5-1 shows the signaling procedure for call reestablishment triggered by a TRB reset.

Figure 5-1 Call reestablishment triggered by a TRB reset

5.2.2 ImplementationExcept that the trigger cause is different, the process of call reestablishment triggered by a TRBreset is the same as that triggered by an RL out-of-synchronization problem. For details, seesection 3.2.2 Implementation.



28

5.2.3 CELL_DCH-to-CELL_PCH Reconfiguration andReestablishment

The D2P reconfiguration and reestablishment procedure triggered for a fast-dormancy UEperforming a single PS service due to a TRB reset is the same as the same procedure triggeredby an RL failure, except that the triggering cause is different. For details, see 3.2.3 CELL_DCH-to-CELL_PCH Reconfiguration and Reestablishment.



29

6 Air-Interface Process Timeout6.1 Air-Interface Process Timeout Detection6.1.1 Radio Bearer Setup Timeout

Radio bearer setup timeout occurs in the following scenarios:l Scenario 1: The RNC sends the Radio Bearer Setup message to a UE but does not receive

an ACK message.l Scenario 2: The RNC sends the Radio Bearer Setup message to a UE and receives an ACK

message. However, the RNC does not receive the Radio Bearer Setup Complete messagefrom the UE.

Scenario 1The RNC sends the Radio Bearer Setup message to a UE but does not receive an ACK messagebefore the RbSetupRspTmr(BSC6900,BSC6910) timer expires. The radio Bearer Setup failsand either of the following occurs:l If the call reestablishment function is not enabled, the RAN requests the UE to release the

Iu interface resources and the call drops.l If the call reestablishment function is enabled, the RNC does not request the UE to release

the Iu interface resources but initiates call reestablishment.In this scenario, the call reestablishment function is controlled by the service switch and processswitch, as described in Table 6-1.

WCDMA RANCall Reestablishment Feature Parameter Description 6 Air-Interface Process Timeout


30

Table 6-1 Switches for call reestablishment triggered by radio bearer setup timeout in scenario1

Service Switch Process Switch CauseSwitch

The CS service is controlled byOptimizationSwitch(BSC6900,BSC6910):CS_RL_SETUP_SWITCH.

The RB setup is controlled byPROCESSSWITCH4(BSC6900,BSC6910):RB_SETUP_RL_REEST_SWITCH.

None

The PS service is controlled byOptimizationSwitch(BSC6900,BSC6910):PS_RL_SETUP_SWITCH.

NOTE

l The service switch for CS+PS combined services is the same as that for CS services.l When call reestablishment is triggered for CS+PS combined services, calls are reestablished for both

CS and PS services.

Figure 6-1 shows the signaling procedure for call reestablishment triggered by radio bearer setuptimeout in scenario 1.



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Figure 6-1 Call reestablishment triggered by radio bearer setup timeout in scenario 1

Scenario 2The RNC sends the Radio Bearer Setup message to a UE and receives an ACK message.However, the RNC does not receive the Radio Bearer Setup Complete message from the UEbefore the RbSetupRspTmr(BSC6900,BSC6910) timer expires. Then either of the followingoccurs:l If the call reestablishment function is not enabled, the RNC sends the Iu Release Request

message to the core network and the call drops.l If the call reestablishment function is enabled, the RNC does not send the Iu Release

Request message to the core network but initiates call reestablishment.In this scenario, the call reestablishment function is controlled by the service switch and processswitch, as described in Table 6-2.



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Table 6-2 Switches for call reestablishment triggered by radio bearer setup timeout in scenario2


The CS service is controlled byOptimizationSwitch(BSC6900,BSC6910):CS_RL_SETUP_SWITCH.

RB setup is controlled byPROCESSSWITCH4(BSC6900,BSC6910):RB_SETUP_RL_REEST_SWITCH and PROCESSSWITCH4(BSC6900,BSC6910):RB_SETUP_ENHANCE_RL_REEST_SWITCH.

None

The PS service is controlled byOptimizationSwitch(BSC6900,BSC6910):PS_RL_SETUP_SWITCH.

NOTE


CS and PS services.

In this scenario, the call reestablishment function is controlled by the service switch and processswitch, as described in Figure 6-2.



33

Figure 6-2 Call reestablishment triggered by radio bearer setup timeout in scenario 2

6.1.2 Radio Bearer Release Timeout of PS ServicesRadio bearer release timeout occurs in the following scenarios:l Scenario 1: The RNC sends the Radio Bearer Release message to a UE but does not receive

an ACK message.l Scenario 2: The RNC sends the Radio Bearer Release message to a UE and receives an

ACK message. However, the RNC does not receive the Radio Bearer Release Completemessage from the UE.

NOTE

All the radio bearer releases mentioned in this section are releases of PS services



34

Scenario 1The RNC sends the Radio Bearer Release message to a UE but does not receive an ACK messagebefore the RbRelRspTmr(BSC6900,BSC6910) timer expires. Then either of the followingoccurs:l If the call reestablishment function is not enabled, the RNC sends the Iu Release Request


Request message to the core network and call reestablishment is triggered.To enable the call reestablishment function triggered by radio bearer release timeout, enable theservice and process switches listed in Table 6-3.

Table 6-3 Switches for call reestablishment triggered by radio bearer release timeout in scenario1

Service Switch Process Switch Cause SwitchThe CS service is controlledby OptimizationSwitch(BSC6900,BSC6910):CS_RL_SETUP_SWITCH.

RB release is controlled byPROCESSSWITCH4(BSC6900,BSC6910):RB_REL_RL_REEST_SWITCH.

None

NOTE

l The call reestablishment function triggered by radio bearer release timeout applies only to CS+PScombined services.

l When call reestablishment is triggered for CS+PS combined services, calls are reestablished only forCS service.

Figure 6-3 shows the signaling procedure for call reestablishment triggered by radio bearerrelease timeout in scenario 1.



35

Figure 6-3 Call reestablishment triggered by radio bearer release timeout in scenario 1

Scenario 2The RNC sends the Radio Bearer Release message to a UE and receives an ACK message.However, the RNC does not receive the Radio Bearer Release Complete message from the UEbefore the RbRelRspTmr(BSC6900,BSC6910) timer expires. Then either of the followingoccurs:l If the call reestablishment function is not enabled, the RNC sends the Iu Release Request


Request message to the core network and call reestablishment is triggered.To enable the call reestablishment function in this scenario, enable the service and processswitches listed in Table 6-4.



36

Table 6-4 Switches for call reestablishment triggered by radio bearer release timeout in scenario2



None

NOTEl The call reestablishment function triggered by radio bearer release timeout applies only to CS+PS

combined services.l When call reestablishment is triggered for CS+PS combined services, calls are reestablished for both

CS and PS services.Figure 6-4 shows the signaling procedure for call reestablishment triggered by radio bearerrelease timeout in scenario 2.

Figure 6-4 Call reestablishment triggered by radio bearer release timeout in scenario 2



37

6.1.3 Radio Bearer Reconfiguration TimeoutAfter sending a Radio Bear Reconfiguration message to a UE, the RNC starts a timer whoselength is determined by the RbRecfgRspTmr(BSC6910,BSC6900) parameter. If the RNC doesnot receive a Radio Bearer Reconfiguration Complete message from the UE before the timerexpires, radio bearer reconfiguration timeout occurs. Then either of the following occurs:l If the call reestablishment function is not enabled, the RNC sends an Iu Release Request

message to the core network and the call drops.l If the call reestablishment function is enabled, the RNC does not send an Iu Release Request

message to the core network but initiates call reestablishment.To enable the call reestablishment function in this scenario, enable the service and processswitches listed in Table 6-5.

Table 6-5 Switches for call reestablishment triggered by radio bearer reconfigurationtimeout

Service Service Switch Process Switch CauseSwitch

CSservices

CS_RL_SETUP_SWITCH underOptimizationS-witch(BSC6900,BSC6910)

TheRBRECFG_ENH_RL_REEST_SWITCH under the PROCESSSWITCH4(BSC6900,BSC6910) parameter andtheRB_RECFG_RL_REEST_SWITCH under the OptimizationSwitch(BSC6900,BSC6910) parametercontrol whether call reestablishmentcan be triggered by the timeout of radiobearer reconfiguration in the DCCCprocedure. Call reestablishment can betriggered by the timeout of radio bearerreconfiguration in the DCCCprocedure only when these twoswitches are enabled.TheNON_DCCC_RBRECFG_RL_REEST_SWITCH under theImprovementSwitch(BSC6900,BSC6910) parametercontrols whether call reestablishmentcan be triggered by the timeout of radiobearer reconfiguration in proceduresother than DCCC.

None

PSservices

PS_RL_SETUP_SWITCH underOptimizationS-witch(BSC6900,BSC6910)

NOTE

When call reestablishment is triggered for CS+PS combined services, calls are reestablished for bothCS and PS services.



38

Figure 6-5 shows the signaling procedure for call reestablishment triggered by radio bearerreconfiguration timeout.

Figure 6-5 Call reestablishment triggered by radio bearer reconfiguration timeout

If a call reestablishment procedure is triggered after an RB procedure (RAB setup,reconfiguration, or release) fails, the response message may not be received, causing afailure in configuration of TRB encryption. As a result, the user-plane transmission fails. TRB in acknowledged mode

For a TRB in acknowledged mode, the user plane transmission may fail after the callreestablishment is complete if the call reestablishment is triggered by timeout of a RABsetup, reconfiguration, or release procedure. To prevent the user-plane transmissionfailure in this scenario, select RB_RLREEST_AM_TRB_RLC_REEST_SWITCHunder the OptimizationSwitch4(BSC6900,BSC6910) parameter in the MML commandSET URRCTRLSWITCH. TRB in unacknowledged mode

For a TRB in unacknowledged mode, the user plane transmission may fail after the callreestablishment is complete if the call reestablishment is triggered by timeout of a RABsetup procedure. To prevent the user-plane transmission failure in this scenario, select



39

RB_SETUP_UM_TRB_RLREEST_ADJUD_OPT_SWITCH under theOptimizationSwitch4(BSC6900,BSC6910) parameter in the MML command SETURRCTRLSWITCH. After you select this switch, if an RB Setup Complete messageis not received, the TRB cannot be encrypted. Therefore, the RAB setup procedure ends,and the call reestablishment procedure will not be triggered.

6.1.4 Physical Channel Reconfiguration TimeoutAfter sending a Physical Channel Reconfiguration message to a UE, the RNC starts a timerwhich is determined by the HoPhychRecfgTmr(BSC6900,BSC6910) parameter. If the RNCdoes not receive a Physical Channel Reconfiguration Complete message from the UE before thetimer expires, physical channel reconfiguration times out. Then either of the following occurs:l If the call reestablishment function is not enabled, the RNC sends an Iu Release Request



Table 6-6 Switches for call reestablishment triggered by physical channel reconfigurationtimeout


Switch for CS services:CS_RL_SETUP_SWITCH under theOptimizationSwitch(BSC6900,BSC6910)parameter

PHY_RECFG_REEST_SWITCH andPHYCHRECFG_ENH_RL_REEST_SWITCHunder the PROCESSSWITCH4(BSC6900,BSC6910) parameterCall reestablishment can be triggered by physicalchannel reconfiguration timeout only when both theswitches are turned on.

None

Switch for PS services:PS_RL_SETUP_SWITCH under theOptimizationSwitch(BSC6900,BSC6910)parameter

NOTE

When call reestablishment is triggered for CS+PS combined services, both CS and PS services arereestablished.

Figure 6-6 shows the signaling procedure for call reestablishment triggered by physical channelreconfiguration timeout.



40

Figure 6-6 Call reestablishment triggered by physical channel reconfiguration timeout

6.1.5 Security Mode Setup TimeoutAfter sending a Security Mode Command message to a UE, the RNC starts a timer whose lengthis determined by the RRCSECRTMODECMPTMR(BSC6900,BSC6910) parameter. If theRNC does not receive a Security Mode Complete message from the UE before the timer expires,security mode setup timeout occurs. Then either of the following occurs:l If the call reestablishment function is not enabled, the RNC sends an Iu Release Request





41

Table 6-7 Switches for call reestablishment triggered by security mode setup timeoutService Switch Process Switch Cause

SwitchCS_RL_SETUP_SWITCH under OptimizationS-witch(BSC6900,BSC6910)

The SMC_RL_REEST_SWITCH underthe ImprovementSwitch(BSC6900,BSC6910) parameter controlswhether call reestablishment can betriggered by security mode setup timeout.

None

PS_RL_SETUP_SWITCH under OptimizationS-witch(BSC6900,BSC6910)

NOTE

Call reestablishment triggered by security mode setup timeout applies to scenarios where a UE hasset up a single service or combined services but the UE experiences a security mode setup failurewhen attempting to set up another service.

Figure 6-7 shows the signaling procedure for call reestablishment triggered by securitymode setup timeout.



42

Figure 6-7 Call reestablishment triggered by security mode setup timeout

6.2 Call ReestablishmentExcept that the trigger cause is different, the process of call reestablishment triggered by air-interface process timeout is the same as that triggered by an RL out-of-synchronization problem.For details, see 3.2.2 Implementation.



43

7 Air-interface Process Overlap7.1 Air-Interface Process Overlap Detection

The RNC sends a message to a UE, the RlRstrTmr(BSC6900,BSC6910) or T313(BSC6900,BSC6910) timer expires and an RL ut-of-synchronization problem occurs. For detailsabout whether to use the RlRstrTmr(BSC6900,BSC6910) or T313(BSC6900,BSC6910) timer,see 3.1 Uplink RL Out of Synchronization Detection.The RNC initiates call reestablishment if the UE does not acknowledge the following messagesor the UE does not send the complete message to the RNC for the following message:l Radio Bearer Setupl Radio Bearer Release (for a PS service)l Radio Bearer Reconfigurationl Physical Channel Reconfigurationl Security Mode CommandThe signaling procedures are similar to those of air-interface process timeout. For details, see6.1 Air-Interface Process Timeout Detection.To enable the call reestablishment function in this scenario, enable the service, process, andcause switches.

7.1.1 Radio Bearer Setup OverlapScenario 1: No Acknowledgement Message

Table 7-1 lists the switches for call reestablishment triggered when the RNC does not receivethe ACK of the Radio Bearer Setup message from the UE.

WCDMA RANCall Reestablishment Feature Parameter Description 7 Air-interface Process Overlap


44

Table 7-1 Switches for call reestablishment triggered by air-interface process overlap in scenario1 (ACK of the Radio Bearer Setup message is not received.)


The RB setup is controlled byPROCESSSWITCH4(BSC6900,BSC6910):RB_SETUP_RL_REEST_SWITCH.

OptimizationSwitch(BSC6900,BSC6910):RLFAIL_RL_SETUP_SWITCH

The PS service is controlledby OptimizationSwitch(BSC6900,BSC6910):PS_RL_SETUP_SWITCH.

NOTE


CS and PS services.

Scenario 2: No Complete Message after the ACK messageTable 7-2 lists the switches for call reestablishment triggered when the RNC receives the ACKof the Radio Bearer Setup message but not the Radio Bearer Setup Complete message from theUE.

Table 7-2 Switches for call reestablishment triggered by air-interface process overlap in scenario2 (ACK of the Radio Bearer Setup message is received.)


RB setup is controlled byPROCESSSWITCH4(BSC6900,BSC6910):RB_SETUP_RL_REEST_SWITCH andPROCESSSWITCH4(BSC6900,BSC6910):RB_SETUP_ENHANCE_RL_REEST_SWITCH.


The PS service is controlledbyOptimizationSwitch(BSC6900,BSC6910):PS_RL_SETUP_SWITCH.

NOTE


CS and PS services.



45

7.1.2 Radio Bearer Release Overlap of PS ServicesScenario 1: No Acknowledgement Message

Table 7-3 lists the switches for call reestablishment triggered when the RNC does not receivethe ACK of the Radio Bearer Release message from the UE. This call reestablishment appliesonly to CS+PS combined services.

Table 7-3 Switches for call reestablishment triggered by air-interface process overlap in scenario1 (ACK of the Radio Bearer Release message is not received.)

Service Switch Process Switch Cause SwitchThe CS service iscontrolled byOptimizationSwitch(BSC6900,BSC6910):CS_RL_SETUP_SWITCH.



NOTE


CS and PS services.

Scenario 2: No Complete Message after the ACK messageTable 7-4 lists the switches for call reestablishment triggered when the RNC receives the ACKof the Radio Bearer Release message but not the Radio Bearer Release Complete message fromthe UE. This call reestablishment applies only to CS+PS combined services.

Table 7-4 Switches for call reestablishment triggered by air-interface process overlap in scenario2 (ACK of the Radio Bearer Release message is received.)


RB release is controlledbyPROCESSSWITCH4(BSC6900,BSC6910):RB_REL_RL_REEST_SWITCH.


NOTE


CS and PS services.



46

7.1.3 Radio Bearer Reconfiguration OverlapTable 7-5 lists the switches for call reestablishment triggered when the RNC does not receivethe ACK of the Radio Bearer Reconfiguration message from the UE for a single PS service.

Table 7-5 Switches for call reestablishment triggered by air-interface process overlap in scenario1 (ACK of the Radio Bearer Reconfiguration message for a single PS service is not received.)

Service Switch Process Switch Cause SwitchThe PS service is controlledby OptimizationSwitch(BSC6900,BSC6910):PS_RL_SETUP_SWITCH.

RB reconfiguration iscontrolled byOptimizationSwitch(BSC6900,BSC6910):RB_RECFG_RL_REEST_SWITCH.


Table 7-6 lists the switches for call reestablishment triggered when the RNC does not receivethe ACK of the Radio Bearer Reconfiguration message for CS+PS combined services.

Table 7-6 Switches for call reestablishment triggered by air-interface process overlap in scenario1 (ACK of the Radio Bearer Reconfiguration message for CS+PS combined services is notreceived.)


RB reconfiguration iscontrolled byOptimizationSwitch(BSC6900,BSC6910):RB_RECFG_RL_REEST_SWITCH.


NOTE


CS and PS services.

7.1.4 Physical Channel Reconfiguration OverlapTable 7-7 lists the switches for call reestablishment triggered when the UE does not send theRNC a Physical Channel Reconfiguration Complete message for a single PS service.



47

Table 7-7 Switches for call reestablishment triggered when the UE does not send a PhysicalChannel Reconfiguration Complete message to the RNC for a single PS service

Service Switch Process Switch Cause SwitchSwitch for PS services:PS_RL_SETUP_SWITCHunder the OptimizationS-witch(BSC6900,BSC6910)parameter

Call reestablishment duringphysical channelreconfiguration is controlledbyPHY_RECFG_REEST_SWITCH under thePROCESSSWITCH4(BSC6900,BSC6910)parameter.


Table 7-8 lists the switches for call reestablishment triggered when the UE does not send theRNC a Physical Channel Reconfiguration Complete message for CS+PS combined services.

Table 7-8 Switches for call reestablishment triggered when the UE does not send a PhysicalChannel Reconfiguration Complete message to the RNC for CS+PS combined services

Service Switch Process Switch Cause SwitchSwitch for CS services:CS_RL_SETUP_SWITCHunder the OptimizationS-witch(BSC6900,BSC6910)parameter

Call reestablishment duringphysical channelreconfiguration is controlledbyPHY_RECFG_REEST_SWITCH under thePROCESSSWITCH4(BSC6900,BSC6910)parameter.


NOTE


CS and PS services.

7.1.5 Security Mode Setup OverlapTable 7-9 lists the switches for call reestablishment triggered when the UE does not send theRNC a Security Mode Complete message. These switches apply to scenarios where the UE hasset up a PS service and attempts to set up a new service.



48

Table 7-9 Switches for call reestablishment triggered when the UE does not send the RNC aSecurity Mode Complete message

Service Service Switch Process Switch Cause SwitchPS services PS_RL_SETUP_S

WITCH underOptimizationSwitch(BSC6900,BSC6910)

TheSMC_RL_REEST_SWITCH under theImprovementSwitch(BSC6900,BSC6910) parameter controlswhether callreestablishment canbe triggered whensecurity mode setupoverlaps cell update.

RLFAIL_RL_SETUP_SWITCH underOptimizationSwitch(BSC6900,BSC6910)

NOTE


CS and PS services.

Table 7-10 lists the switches for call reestablishment triggered when the UE does not send theRNC a Security Mode Complete message. These switches apply to scenarios where the UE hasset up a CS service and attempts to set up a new service.

Table 7-10 Switches for call reestablishment triggered when the UE does not send the RNC aSecurity Mode Complete message

Service Service Switch Process Switch Cause SwitchCS services CS_RL_SETUP_S

WITCH underOptimizationSwitch(BSC6900,BSC6910)

TheSMC_RL_REEST_SWITCH under theImprovementSwitch(BSC6900,BSC6910) parameter controlswhether callreestablishment canbe triggered whensecurity mode setupoverlaps cell update.


NOTE


CS and PS services.



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7.2 Call ReestablishmentExcept that the trigger cause is different, the process of call reestablishment triggered by air-interface process overlap is the same as that triggered by an RL out-of-synchronization problem.For details, see 3.2.2 Implementation.When receiving an SRNS CONTEXT REQUEST message during a call reestablishmentprocedure, the RNC performs as follows:l If RESERVED_SWITCH_10_BIT12 under RsvSwitch10(BSC6900,BSC6910) in the

MML command SET UALGORSVPARA is set to 1, the RNC stops the callreestablishment process and sends an SRNS CONTEXT RESPONSE message to the CN.Then, the RNC waits for the IU RELEASE COMMAND message from the CN. Thesubsequent process is as follows: If RESERVED_SWITCH_10_BIT11 under RsvSwitch10(BSC6900,BSC6910) in

the MML command SET UALGORSVPARA is set to 1 and the RNC has not receivedthe IU RELEASE COMMAND message after the timer expires, the RNC sends an IURELEASE REQUEST message to the CN with the cause value "Normal Release" andperforms a normal release. If RESERVED_SWITCH_10_BIT11 under RsvSwitch10(BSC6900,BSC6910) in

the MML command SET UALGORSVPARA is set to 0 and the RNC has not receivedthe IU RELEASE COMMAND message after the timer expires, the RNC sends an IURELEASE REQUEST message to the CN with the cause value "TRELOCoverallexpiry" and performs an abnormal release.

l If RESERVED_SWITCH_10_BIT12 under RsvSwitch10(BSC6900,BSC6910) in theMML command SET UALGORSVPARA is set to 0, the RNC ignores the SRNSCONTEXT REQUEST message and continues to wait for the cell update message fromthe UE and finish the call reestablishment process.



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8 Related FeaturesPrerequisite Features

None

Mutually Exclusive FeaturesNone

Impacted FeaturesNone

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9 Network ImpactSystem Capacity

No impact.

Network PerformanceWhen the call reestablishment function is enabled in scenarios with weak coverage or significantsignal fluctuation, calls will be reestablished for UEs with service interruptions or access failuresthat are caused by link failures or control/user plane faults. As a result, the call drop rate decreasesand the UE access success rate increases. The exact gains depend on the coverage of the livenetwork.When a UE service is interrupted or the UE access fails, channel element (CE), code resources,and power resources are released for the UE. After call reestablishment succeeds, the releasedresources are re-occupied by the UE.The call reestablishment function affects end user experience. This function generally affectsCS user experience with more occurrences of mute voice and garbled noise, which can beobserved by the following counters:l VS.AMRNB.ULSilent.OccurNum(BSC6900,BSC6910)l VS.AMRNB.DLSilent.OccurNum(BSC6900,BSC6910)l VS.AMRWB.ULSilent.OccurNum(BSC6900,BSC6910)l VS.AMRWB.DLSilent.OccurNum(BSC6900,BSC6910)l VS.AMRNB.ULGarbledVoice.OccurNum(BSC6900,BSC6910)l VS.AMRWB.ULGarbledVoice.OccurNum(BSC6900,BSC6910)l VS.AMRNB.DLGarbledVoice.OccurNum(BSC6900,BSC6910)l VS.AMRWB.DLGarbledVoice.OccurNum(BSC6900,BSC6910)The call reestablishment function slightly affects non-real-time PS user experience.When the call reestablishment function is enabled for the inter-RAT handover, the values of theKPIs IRATHO.AttOutCS(BSC6900,BSC6910) and IRATHO.AttOutPSUTRAN(BSC6900,BSC6910) will increase and the handover success rate also increases because inter-RAT handovers are initiated again after call reestablishment is complete.

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After the D2P reconfiguration and reestablishment algorithm is enabled, D2P state transitionattempts and successful D2P state transitions increase. Meanwhile, call drops or second RRCconnection setup attempts during CELL_DCH-to-CELL_PCH state transitions increase. Thatis, the values of the following counters increase:

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10 Engineering Guidelines10.1 When to Use Call Reestablishment

Use call reestablishment in temporary coverage holes and in tunnels, elevators, and buildingsthat cause significant radio signal fluctuation.

10.2 Required InformationBefore you enable this function, collect the following information:l Scenario information for call drops or access failures

Causes of call drops or access failures and the number and proportion of times that UEsare involved in the processes performed over the air interfaceThe following formulas are used to calculate the percentage of RABs that are released dueto any of the five causes (RL out of synchronization, SRB reset, PS TRB reset, air interfaceprocess timeout, and air interface process overlapping) that may trigger call reestablishmentto all RABs that are abnormally released: For CS RAB releases, the following formula is used: (VS.RAB.AbnormRel.CS.RF

(BSC6900,BSC6910)/VS.RAB.AbnormRel.CS(BSC6900,BSC6910)) x 100%,where the VS.RAB.AbnormRel.CS.RF(BSC6900,BSC6910) counter indicates thenumber of CS RABs that are released due to the causes that may trigger callreestablishment and the VS.RAB.AbnormRel.CS(BSC6900,BSC6910) counterindicates the total number of abnormally released CS RABs. For PS RAB releases, the following formula is used: (VS.RAB.AbnormRel.PS.RF

(BSC6900,BSC6910)/VS.RAB.AbnormRel.PS(BSC6900,BSC6910)) x 100%,where the VS.RAB.AbnormRel.PS.RF(BSC6900,BSC6910) counter indicates thenumber of PS RABs that are released due to the causes that may trigger callreestablishment and the VS.RAB.AbnormRel.PS(BSC6900,BSC6910) counterindicates the total number of abnormally released PS RABs.

If the calculation result of either of the preceding formulas is greater than 30%, the CallReestablishment feature is recommended.

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NOTE

To enable call reestablishment due to different trigger causes, processes, or service types, differentswitches need to be turned on. When the calculation result of the formula for CS or PS services isgreater than 30%, it is recommended that all corresponding switches for CS or PS services be turnedon.

Call Reestablishment(RAN15.0 06)

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