Precaution Notice for WCDMA RNC The Message Queue Usage Increases When the RL Reestablishment, MBDR, or AMR Anti-Static Function Is Enabled on the RNC

Precaution Notice for WCDMA RNC The Message Queue Usage Increases When the RL Reestablishment, MBDR, or AMR Anti-Static Function Is Enabled on the RNC

SeverityMajorUrgency UrgentProducts InvolvedBSC6900/BSC6910

Release Date2014-05-05

Versions InvolvedAll RAN14.0 versions between V900R014C00SPC500 (included) and V900R014C00SPH562 (excluded)All RAN15.0 versions between V900R015C00SPC500 (included) and V900R015C00SPC529 (excluded)All RAN15.0 versions between V100R015C00SPC100 (included) and V100R015C00SPC529 (excluded)V900R013 and V900R012 are not involved.

Application Scope

Preventive RequirementNotification

[Problem Description]The problem occurs in the following scenarios: 1. The radio link reestablishment function is enabled during Security Mode procedure, RB Setup procedure, or RB Release procedure. Check the settings of the SET URRCTRLSWITCH command. Confirm that the radio link (RL) reestablishment function is enabled. If any bit under URRCTRLSWITCH is set to 1, the associated RL reestablishment function is enabled.

SET URRCTRLSWITCH: ImprovementSwitch =SMC_RL_REEST_SWITCH-1 (for RAN15.0)orSET URRCTRLSWITCH: PROCESSSWITCH4 =RB_SETUP_RL_REEST_SWITCH-1 (for RAN14.0 and RAN15.0)orSET URRCTRLSWITCH:PROCESSSWITCH4=RB_REL_RL_REEST_SWITCH-1 (for RAN15.0)2. The measurement-based directed retry (MBDR) function is enabled.Check the settings of the ADD UCELLMBDRINTERFREQ or ADD UCELLMBDRINTERRAT commands. Confirm that the MBDR function is enabled. If any bit under UCELLMBDRINTERFREQ is set to 1, the MBDR function is enabled.

XX in "CellId=XX" indicates the cell ID.ADD UCELLMBDRINTERFREQ:CellId=XX, InterFreqActiveType=CSAMR_INTERFREQ-1orADD UCELLMBDRINTERFREQ:CellId=XX, InterFreqActiveType=CSNONAMR_INTERFREQ-1orADD UCELLMBDRINTERFREQ:CellId=XX, InterFreqActiveType=PSR99_INTERFREQ-1orADD UCELLMBDRINTERFREQ:CellId=XX, InterFreqActiveType=PSHSPA_INTERFREQ-1orADD UCELLMBDRINTERRAT: CellId=XX, InterRatActiveType=CSAMR_INTERRAT-1

If the previous commands fail to be searched, the MBDR function is not enabled.3. The AMR anti-static function is enabled (using the DRD function through two steps).Run the SET UCORRMALGOSWITCH command to turn on one of the following two switches.

CMP_UU_AMR_DRD_HHO_COMPAT_SWITCH-1: This parameter specifies whether to enable DRD for AMR services through two steps. When a UE whose signaling is set up on the DCH runs only AMR services through the DRD procedure and the switch is turned on, two steps in the DRD procedure are: the UE is first inter-frequency blind handed over to a target cell and then sets up AMR services in the target cell. When the switch is turned off, the DRD procedure is initiated in only one step. Specifically, the UE directly sets up AMR services in the target cell.

CMP_UU_AMR_DRD_HHO_COMPAT_ENH_SWITCH-1: This parameter specifies whether to enable the enhanced AMR anti-static function. If a UE is to set up a single AMR service in the scenario where the SRB over HSPA function is enabled or in the scenario where PS services have been set up (the UE is in the CELL_DCH state) through the DRD procedure, and the switch is turned on, two steps in the DRD procedure are: the UE is first inter-frequency blind handed over to a target cell and then sets up a single AMR service in the target cell. When the switch is turned off, the DRD procedure is initiated in only one step. Specifically, the UE directly sets up a single AMR service in the target cell.

When all the preceding configuration conditions are met, the RNC does not release the received CN messages during the link reestablishment, MBDR process or DRD two-step procedure, thereby continuously consuming message queue resources. The problem is identified using the following methods: 4. Observe the long-term (at least one month) change trend of the message queue usage. The message queue usage keeps increasing in some subsystems of the RNC whose configuration meets the previous descriptions. Specifically, if values of VS.XPU.MSGLOAD.MAX and VS.XPU.MSGLOAD.MEAN keep increasing even during off-peak hours, the problem is identified. If the following condition applies, perform the recovery measures.

VS.XPU.MSGLOAD.MAX >=Min(RESAUDITCTHD, PAGECTHD, HANDOVERCTHD, IURULCTHD, CBSCTHD, CELLURACTHD, ACCTHD, IURGCTHD, DCCCMSGTHD)-5

The parameters are sub-parameters in the SET FCMSGQTHD:BRDCLASS=XPU command.5. EVT-22835 flow control triggered by the high message queue usage is recorded in alarm logs. [Root Causes]

The RNC does not release the received CN messages (for example, in the Security Mode procedure) due to internal processing exceptions during any of the following processes:

RL reestablishment in Security Mode procedure RL reestablishment in RB Setup procedure RL reestablishment in RB Release procedure MBDR process DRD two-step procedure[Impacts and Risks]Impact 1: When the message queue usage exceeds flow control thresholds for paging messages or RRC connection setup request messages, the paging messages or RRC connection setup request messages are discarded due to flow control. Impact 2: When the message queue usage exceeds the flow control threshold for audit messages, the audit messages are discarded due to flow control.

[Workarounds]

Perform the following operations: 6. Turn off SMC_RL_REEST_SWITCH in the SET URRCTRLSWITCH command. SET URRCTRLSWITCH: ImprovementSwitch=SMC_RL_REEST_SWITCH-0 (for RAN15.0)Risks: When the RNC is waiting for a UE's response in security mode, the RL reestablishment for the UE will fail if the RNC detects a timeout or signaling radio bearer (SRB) reset or if the NodeB reports that all RLs for the UE are out of synchronization. 7. Turn off RB_SETUP_RL_REEST_SWITCH in the SET URRCTRLSWITCH command.

SET URRCTRLSWITCH: PROCESSSWITCH4=RB_SETUP_RL_REEST_SWITCH-0 (for RAN14.0 and RAN15.0)Risks: The RNC is waiting for a UE's response during a radio bearer (RB) setup CELL_DCH-to-CELL_DCH (D2D) procedure: The RNC does not reestablish an RL for the UE if the RNC detects an SRB reset at layer 2 or all uplink RLs for the UE are out of synchronization upon expiration of the RL Restore timer. The RNC does not perform a cell update if the RNC receives a CELL UPDATE message with a cause value of RL FAILURE, RLC UNRECOVERABLE ERROR, or REENTERED SERVICE AREA8. Turn off RB_REL_RL_REEST_SWITCH in the SET URRCTRLSWITCH command.

SET URRCTRLSWITCH:PROCESSSWITCH4=RB_REL_RL_REEST_SWITCH-0 (for RAN15.0)Risks: In the CS+PS combined service scenario, the RNC does not reestablish an RL for the UE during a PS RB release procedure under the following conditions: The RNC detects an SRB reset at layer 2 or all uplink RLs for the UE are out of synchronization upon expiration of the RL Restore timer or UE has no response to RNC after RNC sends UE a RADIO BEARER RELEASE message. 9. Disable the MBDR function. MOD UCELLMBDRINTERFREQ:CellId=XX, InterFreqActiveType=CSAMR_INTERFREQ-0& CSNONAMR_INTERFREQ-0& PSR99_INTERFREQ-0& PSHSPA_INTERFREQ-0MOD UCELLMBDRINTERRAT: CellId=XX, InterRatActiveType=CSAMR_INTERRAT-0;(For RAN14.0 and RAN15.0)

10. Disable the AMR anti-static function (using the DRD function through two steps).

SET UCORRMALGOSWITCH:CmpSwitch=CMP_UU_AMR_DRD_HHO_COMPAT_SWITCH-0;SET UCORRMALGOSWITCH:CmpSwitch2=CMP_UU_AMR_DRD_HHO_COMPAT_ENH_SWITCH-0;(RAN14.0 and RAN15.0)Risks: The two switches are turned on to prevent the AMR static problem. If the two switches are turned off, the DRD procedure is initiated in only one step, thereby causing the AMR static problem and decreasing the RAB setup success rate. Therefore, do not turn off the two switches. [Recovery Measures]

11. Perform the workarounds.

12. Switch over the board of the subsystem with the high message queue usage by running the following command:

SWP BRD: SRN=XX, SN=XX[Solutions]

For problems caused by security link reestablishment, upgrade the RNC to V900R015C00SPC529. For RAN14.0Upgrade the RNC to V900R014C00SPH562.2015-01-30Huawei confidential. No spreading without permission.Page 1 of 4