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UMTSOptimizationQuestion&Answer

February1,2011

RadioNetwork

1.Whataretheoptimizationtoolsyouuse?

Drivetest,analysis,others?

2.AreSystemInformationBlocks(SIB)transmittedallthetime?

No,systeminformationblockismultiplexedwithsynchronizationchannel.Synchronizationchanneloccupiesthefirsttimeslot(TS)andSIBoccupiestheother9timeslots.

3.HowdoesUEcamp(synchronize)toaNodeB?

1.UEusestheprimarysynchronizationchannel(P-SCH)forslotalignment(TSsynchronization).

2.AfteraligningtoNodeBtimeslot,UEthenusessecondarysynchronizationchannel(S-SCH)toobtainframesynchronizationandscramblingcodegroupidentification.

3.UEthenusesscramblingcodeIDtoobtainCPICH,thuscampingtoaNodeB.

4.Whatcouldbethecauseofsofthandoverfailure?

*UEissue.*ResourceunavailableattargetNodeB.*InadequateSHOthresholddefined.oEtc.

5.Whatarethethreesetsinhandover?

The3setsinhandoverare:

*ActivesetthelistofcellswhichareinsofthandoverwithUE.*MonitoredsetthelistofcellsnotinactivesetbutRNChastoldUEtomonitor.oDetectedsetlistofcellsdetectedbytheUEbutnotconfiguredintheneighborlist.

6.WhatarethemajordifferencesbetweenGSMandUMTShandoverdecision?

GSM:

*Time-basedmobilemeasuresofRxLevandRxQualmobilesendsmeasurementre

porteverySACHperiod(480ms).oBSCinstructsmobiletohandoverbasedonthesereports.

UMTS:

*Event-triggeredreportingUEsendsameasurementreportonlyoncertaineventtriggers.oUEplaysmorepartinthehandoverdecision.

7.Whataretheevents1a,1b,1c,etc.?

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13.WhatisthetypicalUEtransmitpower?

Variesmostofthetimebelow0dBm.

14.HaveyourusedEricssonTEMS?Ifso:

*Doyouknowhowtocreatecommandsequence?*Whatarethecallsequencesyoutypicallyhave?CSlongcall,CSshortcall,PSDcall,etc.*WhatarethetypicalcommandsyouhaveforCSandPScall?*Doyouregularlystopandrestartanewlogfile?Whyandwhentostopandstartanewfile?*Howdoyoustopalogfile?Stopcommandsequencefirst,waitandmakesureallequipmentareinidlemodebeforestoplogging.

15.Didyouworkonneighborprioritization?

16.WhatisthetypicaleventsequenceofIRATHandoverfrom3Gto2G

*Event2denteringintocompressedmodemeasurementof2GcandidatesEvent3aVerificationof2GresourcesHandoverfromUTRANCommandfrom3GRNCtoUE

17.WhatarethepossiblecausesforanIRATFailure?

*Missing2Grelations*Nonavailabilityof2GResources*Poor2GCoverage*Missing3GRelations

18.WhatisPagingSuccessRatio?WhatisthetypicalPSRthatyouhaveseeninaUMTSnetwork?

*PSRPagingResponsestothePagingAttempts*About90%

19.WhatarethepossiblecausesforalowerPSR?

*Non-continuousRFCoverageUEgoinginandoutofcoverageareafrequently*VeryHighPeriodicLocationUpdateTimerKeepingUEsinVLRlongtimeafteritmovedoutofcoverage*LowerPagingChannelPower*AccessChannelParameterIssues*DelayedLocationUpdatewhencrossingtheLA/CNBoundaries

20.WhatarethepossiblecausesforaDropCallonaUMTSnetwork?

*PoorCoverage(DL/UL)*PilotPollution/PilotSpillover*MissingNeighbor

*SCCollisions*DelayedHandovers*Noresourceavailability(Congestion)forHandin*LossofSynchronization*FastFading*DelayedIRATTriggers*HardwareIssues*ExternalInterference

21.AUEisservedby2or3SCinAS.ItisidentifyingaSCfrom3rdtier,Str

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ongerandmeetsthecriteriaforEvent1aorEvent1c.ButSHOdidnothappenbecauseofmissingneighborrelations?Howdoyouoptimizethisissue?

*StudythePilotspilloverfromthe3rdTierSCandcontrolitscoverage*Evenaftercontrollingthecoverage,ifthespilloveristhere,Addtheneighbor.

22.AUEisservedby2SCinAS,aSCiscomingintoMonitoredSetandEvent1aistriggered.ButUEisnotreceivingActiveSetUpdatefromNodeBandthecalldrops.Whatcouldbepossiblecausesforthisdrop?

*DelayedHandover*LossofSynchronization*FastFading*PilotPollution/Spilloverissues

23.WhatisHardHandoverinUMTS?Whenwillithappen?

*HardHandoverinUMTSisabreakbeforemaketypeHandover*ItcanhappenintheinterRNCboundarieswherethereisnoIurlink.

24.WhatisthetypicalCallSetupTimefora3GUEto3GUECall?WhatarethepossibleRFrelatedcausesforadelayedCSTinthistypeofcall?

*6to9seconds*MultipleRRCAttempts(UEisonpoorcoverageneedmorethanAccessAttempt)*DelayedPageResponses*HighLoadonPagingand/orAccessChannel*Paging/AccessParameters

25.WhatisSoftHandoverOverhead?WhatisthetypicalvalueinUMTSnetwork?

*SoftHandoverOverheadiscalculatedintwoways.1)AverageActiveSetSizeTotalTraffic/PrimaryTraffic.2)Secondary/TotalTraffic*TypicalValuesarelike1.7(AvgActiveSetSize)or35%(Secondary/Total)

26.WhatwillhappentotheSoftHandoverOverheadwhenyouapplyOCNSonthenetwork?AndWhy?

*WithOCNS,theinterference(load)increases.ThisleadstoreductioninEc/IoofaPilot,whichreducesthepilotspillovers.ReductioninPilotSpilloverwillreducetheSoftHandoverOverhead.

27.WhatarethepossiblecausesforanAccessFailureinUMTS?

*MissingNeighbors*PoorCoverage*PilotPollution/Spillover

*PoorCellReselection*CoreNetworkIssues*Nonavailabilityofresources.AdmissionControldenies*HardwareIssues*ImproperRACHParameters*ExternalInterference

28.(FORERICSSONEXPERIENCED)WhatisRTWP?Whatisthesignificanceofit?

*ReceivedTotalWide-bandPower

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*ItgivestheTotalUplinkPower(Interference)levelreceivedatNodeB

29.(FORERICSSONEXPERIENCED)WhatistheSystemReferencePointatwhichallthePowerLevelsaremeasuredinEricssonNodeB?

*SystemRefPointforE///NodeBisattheoutputofTMA(BetweenTMAandAntenna)

30.Whatarethetypicalvaluesforreportingrange1aandreportingrange1b?

*3dBand5dBrespectively.

31.Whatwillbetheimpactwhenyouchangereportingrange1afrom3to4dBandtimetotrigger1a100to320ms,withoutchanginganyotherparameters?

*ReductioninnumberofEvent1a*DelayedEvent1atrigger*ReductioninAverageActiveSetSize*DelayinEvent1acouldincreaseDLinterference,whichcouldleadtoadropcallorincreaseinAveragePowerPerUser(reductionincellcapacity)

32.WhatisAdmissionControl?

*AdmissionControlisanalgorithmwhichcontrolstheResourceAllocationf

oranewcallandadditionalresourceallocationforanexistingcall.Incase,ifacellisheavilyaloadedandenoughresourcesintermsofpower,codesorCEsarenotavailable,admissioncontroldeniespermissionfortheadditionalresourcerequirement.

33.WhatisCongestionControl?

*CongestionControlmonitorsthedynamicutilizationofspecificcellresourcesandinsuresthatoverloadconditionsdonotoccur.Ifoverloadconditionsdooccur,CongestionControlwillimmediatelyrestrictAdmissionControlfromgrantingadditionalresources.Inaddition,CongestionControlwillattempttoresolvethecongestionbyeitherdownswitching,orterminatingexistingusers.Oncethecongestioniscorrected,thecongestionresolutionactionswillcease,a

ndAdmissionControlwillbeenabled.