小区选择重选

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1、0322：4.5CellselectionprocessWheneveraPLMNisselected,theMSattemptstofindasuitablecellofthatPLMNtocampon.Twomethodsofsearchingforasuitablecellarepossible:当选择好PLMN后，MS将试图寻找该PLMN中一个合适的小区作为主服务小区。有两种方法：a)Normalcellselection("Normalcellselection"state)HeretheMShasnopriorknowledgeofwhichRFchannels

2、areBCCHcarriers.Itsearchesatleastthenumber,giveninsubclause 3.2.1,ofthestrongestRFchannelsindescendingorderofreceivedsignalleveltoseewhichareBCCHcarriers.(IfnoBCCHcarriershaveyetbeenfound,searchingwillcontinueuntilatleastoneBCCHcarrierisfound.).ThefirstBCCHcarrierfoundwhichisfromasuitablece

3、llandonwhichthereisanormalpriorityindicationistakenandthatcelliscampedon.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)Storedlis

4、tcellselection(optional)("Storedlistcellselection"state)HeretheMShasalistoftheBCCHcarriersusedbythePLMN.(ThislistmaybederivedbytheMSfrominformationgatheredduringpreviousselectionsofthePLMN).TheBCCHcarriersinthelistaresearchedindescendingorderofreceivedsignallevel,andthefirstBCCHcarrierfoun

5、dwhichisfromasuitablecellandonwhichthereisanormalpriorityindicationistaken,andthatcelliscampedon.IfanMSdecodesBCCHdatafromacelloftheselectedPLMNbutisunabletocamponthatcell,theBAofthatcellshallbeexaminedandanyBCCHcarriersintheBAwhicharenotinthelistofBCCHcarrierstobesearchedshallbeaddedtothel

6、ist.IfalltheseBCCHcarriershavebeentriedandtheonlysuitablecellsfoundhavelowpriorityindication,theMSshallcamponthestrongestofthesecells.Ifnosuitablecellisfoundusingmethodb),methoda)isthentried.WhilecampedonacelloftheselectedPLMN("campednormally"),theMSmayneedtoselectadifferentcell("normalcell

7、reselection"state).Thefollowingeventstriggeracellreselection:i)ThepathlosscriterionparameterC1(seesubclause 3.6)indicatesthatthepathlosstothecellhasbecometoohigh;ii)Thereisadownlinksignallingfailure(subclause 3.6);iii)Thecellcampedon(currentservingcell)h