82BSSPAR Handover Control and Adjacencies.docx

82BSSPAR Handover Control and Adjacencies.docx

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82BSSPARHandoverControlandAdjacencies

BSSPAR

HandoverControl&Adjacencies

TrainingDocument

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Contents

1ModuleObjectives5

2IntroductiontotheHandoverProcess6

3HandoverDecisions7

4HandoverTimers9

5TargetCellEvaluationProcess11

5.1DecisionAlgorithms12

5.2C/IBasedHandoverCandidateEvaluation14

6RadioResourceHandovers16

6.1PowerBudgetHandover17

6.2UmbrellaHandover20

6.3CombinedUmbrellaandPowerBudget24

6.3.1FastMovingMS（FMMS）HandlingInMacroCell27

6.3.2MSSpeedDetectionandVariableWindowSize27

6.4HandoverduetoQualityorSignalLevel32

6.4.1HandoverduetoQuality32

6.4.2HandoverduetoSignalLevel35

6.5HandoverDuetoInterference37

7ImperativeHandovers39

7.1MS–BTSDistance40

7.2RapidFieldDropandEnhancedRapidFieldDrop41

7.2.1ChainedAdjacentCellsInRapidFieldDrop42

7.2.2Turn-Around-CornerMS43

8TrafficReasonHandovers48

8.1MSC-ControlledTrafficReasonHandover48

8.2BSCInitiatedTrafficReasonHandover（AdvancedMultilayerHandling）49

8.2.1InteractionswithotherFeatures51

9Loadcontrolbetweenlayers:

AdvancedMultilayerHandling（AMH）52

9.1IUOLoadControl52

9.2Multilayer（DualBand/MicroCellular）NetworkLoadControl53

9.3ParametersInvolvedinAMHfeatureactivation53

10DirectAccesstoDesiredLayer/Band（DADL/B）55

10.1DADL/Binteractionswithotherfeatures56

11HandoverParameterList58

12AdjacentCellParameterList64

13PracticalExamplesofHandovers68

14HandoverControlExercise69

15HandoverExercise70

16KeyLearningPoints71

17ReviewQuestions78

1ModuleObjectives

Attheendofthismodule,theparticipantwillbeableto:

∙Listtentypesofhandovers,intheorderinwhichtheyareprioritised.

∙Statetheparametersdefiningtheminimumintervalsbetweenhandovers,andbetweenhandoverattempts.

∙Discussthetargetcellevaluationprocess.

∙Explaintheparametersassociatedwithpowerbudgethandovers.

∙Nametheparametersusedtocontrolumbrellahandovers.

∙ListtheparametersassociatedwithMSspeeddetectionandhandovers.

∙Discussthemechanismandparametersforhandoverduetosignallevelorquality.

∙Statethevarioustypesofimperativehandoversandtheirassociatedparameters.

∙ExplaintheAdvancedMultilayerHandling（AMH）conceptandparameters.

2IntroductiontotheHandoverProcess

HandoverdecisionsaremadebyRadioResourceManagementintheBSC.

TheyarebasedontheDL&ULmeasurementresultsreportedbytheMS&BTS,whicharethenprocessedaccordingtoparametersettingsforeachcell,andthenprocessedbytheHandoverControlAlgorithm,producingadecision.Targetcellevaluationisalsopartofthehandoverprocess.Handoversaretriggeredbythresholdcomparison,orbyperiodiccomparison.

Whyarehandoversneeded?

1.Callcontinuity:

toensureacallcanbemaintainedasanMSmovesingeographicallocation,fromthecoverageareaofonecelltoanother.

2.Callquality-toensurethatifanMSmovesintoanareaofpoorqualityorpoorcoverage,thecallcanbemovedfromtheservingcelltoaneighbouringcell（withbetterquality）withoutdroppingthecall.

3.TrafficReasons-toensurethatthetrafficwithinthenetworkisoptimallydistributedbetweenthedifferentlayersorbandsofanetwork.

3HandoverDecisions

Therearenumerouscausesforahandoverdecisiontobemade,basedoncomparisonsofmeasurementswiththresholds.TheHOthresholdcomparisonincludestheevaluationoftheuplinkanddownlinklevel,quality,andinterference.Othercriteriaalsoconsideredare:

MS-BSdistanceevaluation,theevaluationofarapidfielddrop,thedetectionofafastorslow-movingMS,thedetectionofaturn-around-cornerMS,powerbudgetevaluation,andumbrellahandoverevaluation.

Figure1HandoverCauses

Iftwoormorecriteriaforahandoverarepresentsimultaneously,theirorderofpriorityisasfollows:

1.Interference（uplinkordownlink）

2.Uplinkquality

3.Downlinkquality

4.Uplinklevel

5.Downlinklevel

6.MS-BSdistance（maximumorminimum）

7.Turn-around-cornerMS

8.Rapidfielddrop

9.Fast/Slow-movingMS

10.Bettercell（PowerbudgetorUmbrella）

11.PCduetoLowerqualitythresholds（uplinkanddownlink）

12.PCduetoLowerlevelthresholds（uplinkanddownlink）

13.PCduetoUpperqualitythresholds（uplinkanddownlink）

14.PCduetoUpperlevelthresholds（uplinkanddownlink）.

Whentwoormoreoftheaboveindicatedcriteria（from1.to9.）arepresentsimultaneously,forexampleUplinkqualityandUplinklevel,theBSCperformstargetcellevaluation,onlyaccordingtothecriterionwhichhasthehighestpriority.So,outofUplinkqualityandUplinklevel,thatwouldbeUplinkquality.Ifnoadjacentcellisgoodenoughforahandovercausedbythiscriterion,thentheBSCproceedstothenextHOthresholdcomparison（10.Bettercell）,andthentothePCthresholdcomparisons（11.to14.）.

4HandoverTimers

TheBSCnormallycontrolstheintervalsbetweenhandoversandhandoverattemptsbytheuseofthefollowingparameters:

minIntBetweenHoReq（MIH）（HOC）（ZEHO）（0..31s）（5s）,and

minIntBetweenUnsuccHoAttempt（MIU）（HOC）（ZEHO）（0..31s）（3s）

Thefirstparameter（MIH）preventsrepetitivehandoversforthesameMS,byusingatimerthatsetstheminimumintervalbetweenhandoversrelatedtothesameconnection.

Thelatterparameter（MIU）definestheminimumtimethattheMSmustwaitafterahandoverattemptfails,beforeitcantryahandoverattemptagain.

TheMMLdefaultvaluesare（5s）and（3s）asnotedabove,andtherecommendedvaluesfortheseparametersarethesameasthedefaults.

ThemeasurementaveragingandtheHOThresholdcomparisondonotstopduringtheseintervals,althoughhandoversarenotpossible.

Figure2HandoverTimers

Figure3HandoverFailureTimer

Figure4GuardPeriodforback-handover

5TargetCellEvaluationProcess

TargetcellevaluationismadeinRadioResourceManagementintheBSC.

Thepurposeoftheprocessistofindthebesttargetcelltosatisfythecauseforthehandover.

Evaluationofthepreferredlistoftargetcellsisbasedon:

1.theradiolinkmeasurements

2.thresholdcomparison

3.theprioritylevelsoftheneighbouringcells

4.theloadofthoseneighbouringcellswhichbelongtothesameBSCastheservingcell

5.RXlevelcomparison–ifitisneeded

Tobeonthetargetcellcandidatelist,theneighbouringcellsmust,ofcourse,bedefinedasAdjacenciesintheoutgoingdirectionfromtheservingcell.TheBTSsendsthelistofbestcandidatestotheBSC.FirsttheBSCdefinesandselectsthosecellswhichmeettherequirementsfortheradiolinkproperties.

RRManagementcanhandleupto32ofthebestcandidatesfortargetcellevaluation.

Theloadsofthetrafficchannelsinthesecandidatecellsarecheckedbytheparameter:

btsLoadThreshold（BLT）（BTS）（ZEQO）（0..100%）（70%）

Ifoneofthesecandidatecellsisalready"overloaded",（thatisloadedabovethethreshold,whichisasoftlimit）,thentheprioritythathasalreadybeensetforthatcellbytheparameter:

hoLevPriority（PRI）（ADJC）（ZEAO）（0..7）（3）

isdecreasedbythevalueoftheparameter:

hoLoadFactor（OF）（ADJC）（ZEAO）（0..7）

（1）

Aftertheloadcheckofeachcandidate,acomparisonbetweenprioritiesofeachcandidatecellismade,andthecandidatewiththehighestprioritywillbeselectedasatargetcell.Iftherearemanycellswithequallyhighpriorities,thecellwiththebestreceivedsignalstrengthwillbeselected.

Note:

ParameterOFmustNOTbesettobegreaterthanPRI.

WiththeBLTparameter,wedefinewhichproportionofreservedorunavailablechannels,inallchannels,isacceptable.BLTisoneofthekeyparametersusedinthehandovercontrolprocess.Ifthisthresholdisexceeded,theBTS（=cell,=sector）isconsideredtobe"