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3.2.1,ofthestrongestRFchannelsindescendingorderofreceivedsignalleveltoseewhichareBCCHcarriers.（IfnoBCCHcarriershaveyetbeenfound,searchingwillcontinueuntilatleastoneBCCHcarrierisfound.）.ThefirstBCCHcarrierfoundwhichisfromasuitablecellandonwhichthereisanormalpriorityindicationistakenandthatcelliscampedon.Ifatleastthenumber,giveninsubclause 

3.2.1,ofthestrongestRFchannelshavebeentriedandtheonlysuitablecellsfoundhavelowpriorityindicationtheMSshallcamponthestrongestofthesecells.

a）通常的小区选择-这里MS事先并不知道哪些RF信道是BCCH载频，

b）Storedlistcellselection（optional）（"

Storedlistcellselection"

state）HeretheMShasalistoftheBCCHcarriersusedbythePLMN.（ThislistmaybederivedbytheMSfrominformationgatheredduringpreviousselectionsofthePLMN）.TheBCCHcarriersinthelistaresearchedindescendingorderofreceivedsignallevel,andthefirstBCCHcarrierfoundwhichisfromasuitablecellandonwhichthereisanormalpriorityindicationistaken,andthatcelliscampedon.IfanMSdecodesBCCHdatafromacelloftheselectedPLMNbutisunabletocamponthatcell,theBAofthatcellshallbeexaminedandanyBCCHcarriersintheBAwhicharenotinthelistofBCCHcarrierstobesearchedshallbeaddedtothelist.IfalltheseBCCHcarriershavebeentriedandtheonlysuitablecellsfoundhavelowpriorityindication,theMSshallcamponthestrongestofthesecells.

Ifnosuitablecellisfoundusingmethodb）,methoda）isthentried.

WhilecampedonacelloftheselectedPLMN（"

campednormally"

）,theMSmayneedtoselectadifferentcell（"

normalcellreselection"

state）.Thefollowingeventstriggeracellreselection:

i）ThepathlosscriterionparameterC1（seesubclause 

3.6）indicatesthatthepathlosstothecellhasbecometoohigh;

ii）Thereisadownlinksignallingfailure（subclause 

3.6）;

iii）Thecellcampedon（currentservingcell）hasbecomebarred;

iv）Thereisabettercell（intermsofthepathlosscriterionC2）inthesameregistrationarea,oramuchbettercellinanotherregistrationareaoftheselectedPLMN（usingtheCRHparameter,subclause 

3.4）;

v）Arandomaccessattemptisstillunsuccessfulafter"

Maxretrans"

repetitions;

"

beingaparameterbroadcastoncontrolchannel.

AGPRSMSinReadystateappliestheREADY_STATECELLRESELECTIONHYSTERESIStogetherwiththepathlosscriterionwhenreselectingthecellwithintheregistrationarea.TheGPRSMSinReadystateshallinformthenetworkaboutcellreselectionwithintheregistrationareabythecellupdateprocedure.ThenetworkmaycontrolcellreselectionofaGPRSMSinReadystate（GSM03.64）.

InsteadoftheparameterC2,aGPRSMSappliesthecorrespondingGPRSparameterifprovided.IfthisGPRSparameterisprovidedthecellshallalsobroadcastalistBA（GPRS）indicatingBCCHcarrierstobemonitoredbyGPRSMSsforcellre-selectionpurpose.

TheMSwillthenreselectanewcellinordertofulfiltheprocessgoal（seesubclause 

4.1）.

Beforecampingonthecellafterreselection,theMSshallattempttodecodethefullsetofsysteminformation.TheMSshallcheckthattheparametersaffectingcellreselectionareunchanged.IfachangeisdetectedtheMSshallcheckifthecellreselectioncriterionisstillvalidusingthechangedparameters.Ifthecellselectioncriteriaarestillvalid,theMSshallcamponthecell.Iftheyarenotstillvalid,theMSshallrepeatthisprocessforthecellwiththenexthighestvalueofC2orcorrespondingGPRSparameter,respectively.

OncetheMShasretunedtothechosencell,itshallmonitoritspagingsubgroup（ifknown）forthatcell.IftheMSandthecellsupportgrouporbroadcastcalls,itshallalsomonitorthenotificationchannel.AGPRSMSshallmonitortherelevantGPRScontrolchannel（s）.IftheMSreceivesapagebeforehavingdecodedtherelevantsysteminformationforthenewcell,theMSshallstorethepageandrespond,ifpermitted,oncetherelevantsysteminformationhasbeendecoded.Ifnotpermitted,nopageresponseshallbemade.

WhentheMSleavesidlemodeandenters"

connectedmode"

（e.g.,tomakeacall）,onreturntoidlemodeattheendofthecall,acellmustbechosen（"

choosecell"

state）assoonaspossiblee.g.,toallowanewcalltobemadeassoonaspossible.ThechosencellwillnotnecessarilybethesamecellastheMSwascampedonwhenthecallstartede.g.,iftheMSmovedasignificantdistancewhilethecallwasinprogress.TwocasesaredistinguishedinGSM 

05.08,forwhichthealgorithmisslightlydifferent:

a）NormalcaseThecallisterminated,eitherbecausetheuser（ornetwork）hasterminatedthecall,orbecausearadiolinkfailurehasoccurredandcallreestablishmentisnotbeingattempted.

b）CallreestablishmentAradiolinkfailurehasoccurredandacallreestablishmentisbeingattempted.（TheMSreturnstoidlemodetostartthecallreestablishmentattemptandneedstoselectanewcellonwhichtomaketheattemptassoonaspossibleinordertominimizetheinterruptiontothecall）.

Ifnosuitablecellisfoundbyeitherthestoredlistcellselection,normalcellreselection,orchoosecelltasks（allofwhichusealimitedsearch）,thenormalcellselectiontask（whichsearchesallRFchannelsforasuitablecell）isentered.

Ifnosuitablecellisfoundbythenormalcellselectiontask,orifthereisnoSIMintheMS,theMSattemptstofindan"

acceptablecell"

onwhichitmaycampsothatemergencycallsmaybemade（"

anycellselection"

state）.TheMSignoresthePLMNinformationwhenselectinganacceptablecell,andnoattemptatlocationregistrationismade.ThistaskisalsoenteredifanLRrejectisreceivedwithoneofthefollowingcausevalues:

IMSIunknowninHLR"

（onlyfornon-GPRSMSasthisimpactsonlythenon-GPRSupdatestate,MSscapableofGPRSandnon-GPRSservicestakeacellselectionstateaccordingtotheoutcomeoftheroutingareaupdate）;

IllegalMS"

;

illegalME"

PLMNnotallowed"

（However,thiswilltriggeranewPLMNselectioniftheMSisinautomaticmode）;

-"

GPRSnotallowed“（onlyforMScapableofGPRSonly,wherethiswilltriggeranewPLMNselectioniftheMSisinautomaticmode;

MSscapableofGPRSandnon-GPRSservicestakeacellselectionstateaccordingtotheoutcomeoflocationupdatingas"

GPRSnotallowed“hasonlyimpactontheGPRSupdatestatus）.

Ifanacceptablecellisfound,theMScampsonit（"

Campedonanycell"

state）.Ifoneofthecellreselectiontriggerevents（i）to（v）aboveoccurs,theMSattemptstofindanewacceptablecelltocampon（"

anycellreselection"

state）butusingazerodBvalueofCRH.Ifnoacceptablecellcanbefound,the"

taskisreentered.

Ifwhilecampedonanacceptablecell,anemergencycalloriginationismade,theMSentersaconnectedmodeandattheendofthecall,choosesanacceptablecell（"

chooseanycell"

state）sothatitisreadyforthenextemergencycallorigination.

Inallcases,ifanewPLMNisselected,theMSsearchesforasuitablecellofthatPLMN.However,iftheMShasrecentlysearchedthestrongestRFchannelswhileapreviousPLMNwasselected,itmayalreadyhaveinformationaboutotherPLMNs.

TheusermayrequestasearchofRFchannelstodeterminewhichPLMNsareavailable.ThissearchshallbedoneinsuchawayastominimizeinterruptionstotheMS'

smonitoringofitspagingsubchannel.

0508v620

6Idlemodetasks

6.1Introduction

Whilstinidlemode,anMSshallimplementthecellselectionandreselectionproceduresdescribedinGSM 

03.22.Theseproceduresmakeuseofmeasurementsandsubproceduresdescribedinthisclause.

TheproceduresensurethattheMSiscampedonacellfromwhichitcanreliablydecodedownlinkdataandwithwhichithasahighprobabilityofcommunicationsontheuplink.OncetheMSiscampedonacell,accesstothenetworkisallowed.

ThisclausemakesuseoftermsdefinedinGSM 

03.22.

TheMSshallnotusethediscontinuousreception（DRX）modeofoperation（i.e.poweringitselfdownwhenitisnotexpectingpagingmessagesfromthenetwork）whileperformingthecellselectionalgorithmdefinedinGSM 

03.22.Howeveruseofpoweringdownispermittedatallothertimesinidlemode.

Forthepurposeofcellselectionandreselection,theMSshallbecapableofdetectingandsynchronizingtoaBCCHcarrierandreadtheBCCHdataatreferencesensitivitylevelandreferenceinterferencelevelsasspecifiedinGSM 

05.05.AnMSinidlemodeshallalwaysfulfiltheperformancerequirementspecifiedinGSM 

05.05atlevelsdowntoreferencesensitivitylevelorreferenceinterferencelevel.Theallowederrorrates（seeGSM 

05.05）mightimpactthecellselectionandreselectionprocedure,e.g.triggercellreselection.Moreover,oneconsequenceoftheallowederrorratesisthatinthecaseofnofrequencyhoppingandaTU3（TU1.5forDCS 

1 

800）propagationprofileitcannotbeexpectedthatanMSwillrespondtopagingunlessthereceivedlevelis2dBhigherthanthespecifiedreferencelevel.

Forthepurposesofcellselectionandreselection,theMSisrequiredtomaintainanaverageofreceivedsignalstrengthsforallmonitoredfrequencies.Thesequantitiestermedthe"

receivelevelaverages"

shallbeunweightedaveragesofth