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1. Low CSSR Voice (1)Background info:RRC Establishment- RRC setup procedure, is the process that establishes the L3connectionbetween UE and RNC that is used for signalling traffic only.- After RNC

receives the RRC CONNECTION REQUEST, processes itand allocates relevant resources onL1, L2 and L3 of the air interface forthis signalling connection.- The RNC notifies the UEfor the prepared configuration with the RRCCONNECTION SETUP message.- TheUE reports its capabilities to the RNC with the RRC CONNECTIONSETUP COMPLETE.RAB Establishment- RAB setup procedure is the process that establishes thehigher-layer connection between UE and CN that is used totransfer the user data only (notsignalling).- When the RNC receives the RAB ASSIGNMENT REQUESTallocates thenecessary resources for the requested service,after successful call admission.Resources include Codes,CE, Power, Iub bandwidth.- Then the RB is setup which is theUTRAN part of the RAB.- Upon successful completion of the RB setup, the

RNCresponds to the CN with the RAB ASSIGNMET RESPONDmessage.

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10 Nokia Siemens Networks Presentation / Author / DateFor internal use1. Low CSSR Voice (2)

- RNC level formula:CS AMR Call Setup Success Rate(RNC)=(([VS.RRC.SuccConnEstab.OrgConv]+[VS.RRC.SuccConnEstab.TrmConv]+[VS.RRC.Su

ccConnEstab.Emg])/([VS.RRC.AttConnEstab.OrgConv]+[VS.RRC.AttConnEstab.TrmConv]+[VS.RRC.AttConnEstab.Emg]))*([VS.RAB.SucEstCSConv0.32.RNC]/[VS.RAB.AttEstCSConv0.32.RNC])*{100}

- Cell level formula:CS AMR Call Setup Success Rate(Cell)=(([RRC.SuccConnEstab.OgConvCall]+[RRC.SuccConnEstab.TmConvCall]+[RRC.SuccConnEstab.EmgCall])/([RRC.AttConnEstab.OrgConvCall]+[RRC.AttConnEstab.TmConvCall]+[RRC.AttConnEstab.EmgCall]))*([VS.RAB.SuccEstab.AMR]/[VS.RAB.AttEstab.AMR])*{100}Analysis process:1.Check which part of the CSSR KPI causes the low value: RRC setup, RAB setup or

both. The 2 distinctparts RRC Setup Success Rate and RAB Setup Success Rate thatare composing the CSSR can be usedfor this purpose.2.To check the above, check thecorresponding KPIs for RRC Setup Success Rate and AMR RAB SetupSuccessRate.3.Check the alarms for the serving NodeB and neighbouring sites in order toidentify any hardware faults.4.In case that RRC Setup is causing the low value, identifythe root cause of high RRC Setup failures byfollowing counters:Transmission problem: following counters indicate transmission issue on Iub interface;check relativealarms to identify faults on the transmission path or the transmissionboards of RNC/NodeB.-VS.RRC.Rej.RL.Fail: RRC establishment failures due to RLsetup failure.-VS.RRC.Rej.TNL.Fail: RRC establishment failures due to TNL (Transport

Network Layer) setup failure.

11 Nokia Siemens Networks Presentation / Author / DateFor internal use1. Low CSSR Voice (3)Radio resource congestion: following counters indicate lack of radio resources or Iubbandwidth. Check theAdmission Control thresholds. Take appropriate measuresto relieve congestion, e.g. activate LDR (LoadReshuffling), OLC (Overload Control)algorithms, and to increase capacity. Refer toHuawei 3G CapacityOptimisation

document in IMS [1] for more details on how to battle congestion and improve capacity.-VS.RRC.Rej.Power.Cong: RRC establishment failures due to power load congestion-VS.RRC.Rej.UL.CE.Cong: RRC establishment failures due to UL CE congestion-VS.RRC.Rej.DL.CE.Cong: RRC establishment failures due to DL CE congestion-VS.RRC.Rej.Code.Cong: RRC establishment failures due to code congestion-VS.RRC.Rej.ULIUBBandCong: RRC establishment failures due to UL Iub bandwidthcongestion-VS.RRC.Rej.DLIUBBandCong: RRC establishment failures due to DL Iub

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bandwidth congestion-VS.RRC.Rej.Other.Cong: RRC establishment failures due to othercongestion except from the previous 6reasonsRF problem: following counter indicate failure due to RF issue. Check coverage inthe failure points. Checkif most failures occur in cell border (most probably they

are). Check FACH power. Check DL interference inthe cell: is there a pilot pollutionissue? Check UL interference in the cell.-RRC.FailConnEstab.NoReply: RRCestablishment failures due to no reply from the UE during the RRCsetup flow.5.In casethat AMR RAB Setup is causing the low value, identify the root cause of high RABSetup failuresby following counters:Transmission problem: following counter indicate transmission issue on Iu-CS interface;check relativealarms.-VS.RAB.FailEstabCS.TNL: CS RAB establishment failures due toTNL problem.

[1] https://sharenet-ims.inside.nokiasiemensnetworks.com/Overview/D420188465