空闲模式.docx

空闲模式.docx

《空闲模式.docx》由会员分享，可在线阅读，更多相关《空闲模式.docx（27页珍藏版）》请在冰豆网上搜索。

空闲模式

1Introduction

没有分配到专用信道的移动台即是“空闲模式的移动台”，本功能的目的是让处于空闲模式的移动台能够接入系统，并通过网络中的其它定位算法延伸至其它系统。

当移动台一开机，便立即尝试接入PLMN网络，可以人工、自动来进行网络的选择，移动台将搜寻并选择一个已选择的PLMN网络中的小区，然后锁定到一个控制信道并接收由PLMN网络所提供的有效服务。

这和对小区的选择便称为Campingon。

当一个移动台一直处于空模式时，它将一直试图去Campingon一个最好的小区（依信号强度算法）

空闲模式下的动作是由移动台来控制的，也可以通过在BCCH信道上接收到的参数来执行控制。

空闲模式下的控制参数都由小区中的BCCH来传送。

2背境

当一个移动台开机后且不进入任何呼叫操作，则它一直处于这样一个状态：

不断选择最好的小区去Camp。

读取信息并寄存LAI，以便系统知道如何建立呼叫路由。

总之：

空闲模式的核心是PLMN网络选择机制，小区选择与重选算法，位置更新过程。

其唯一目的是确保移动台能登寻到一个通信成功机会最大的小区。

3实现

3.1接入系统时的最强信号强度

当移动台接入系统时总是试图获得最强信号。

这便是空闲模式下的小区选择与重选，这些算法将激活移动台去选择最合适去登录。

最基本是信号强度。

一个小区是否合适于登录，将要满足一定的算法，4.3.2,中详述，aresatisfied.Campingonthe

mostsuitablecellprovidestheMSwithahighprobabilityofgood

communicationwiththesystem.

Thecellselectionandreselectionalgorithmsaregovernedbyparameter

settings.Usingtheseparametersanoperatorcan,onapercellbasis,makea

specificcellmoreorlessattractivetocamponfortheMS.Thismakesit

possiblefortheoperatortoachievesimilarbehaviourforMSsinidlemodeas

inactivemode.Well-designedparametersettingsforcellselectionand

reselectioninidlemode,willmaketheMScamponthecellthatitalsowould

havechosenifithadbeeninactivemode.

3.2Controlofthepagingload

InidlemodetheMSwillnotifythenetworkwheneveritchangeslocationarea

bythelocationupdatingprocedure.Thus,thenetworkwillbekeptupdated

concerningwhichlocationareatheMSispresentlyin.Whenthesystem

receivesanincomingcallitknowsinwhichlocationareaitshouldpagethe

MS,anddoesnotneedtopageitthroughoutthewholenetwork.Thisreduces

theloadonthesystem.IftheMSdoesnotrespondonthefirstpaging,thenthe

networkcandoasecondpaging.Differentpagingstrategiesaredescribedin

section4.7.2.

TheMScanalso,periodicallyandwhenpoweredonoroff,notifythenetwork

ofitspresentstatusbythelocationupdatingprocedure,seesection4.5.3and

section4.5.4.Thispreventsthenetworkfromdoingunnecessarypagingsof

MSsthathavebeenpoweredofforleftthecoveragearea.Thiswould

otherwisecauseunnecessaryloadonthesystem.

3.3空闲模式下的低功率消耗

空闲模式下，移动台间隔性地监视由当前小区专送的系统信息并测量相邻小区以决定是否要启动小区的变化，然而大部分是间下移动台处

Sleep模式?

因而节省功率，当然也可以通过不连续接收来实现（DRX）。

4技术介绍与工程指南

4.1总则

空闲模式下的MS不断测量当前小区与相邻小区的BCCH载波以选择登录，必要时寄存LAI以进行位置更新。

登录小区的目的是：

1.激活MS去接收PLMN系统信息,

2.以便在RACH上接入网络

3.另外PLMN也知道MS当前的LA，（除非移动台进入限制服务状态section4.4.3）因而当来话知道如何寻呼MS。

空闲模式下移动台工作分四个过程：

1、PLMNselection,

2、Cellselection,

3、Cellreselection,

4、Locationupdating.

图1示：

4.2PLMNselection

4.2.1总则

当移动台开机或脱离一个盲区后，它便试图去选择并登寻注册的PLMN。

如果没有注册的PLMN或者注册的PLMN不存在，它将试图去选另一个PLMN（手动或自动）

.IfthereisnoregisteredPLMN,oriftheregisteredPLMNisunavailabletheMSwilltrytoselecttoanotherPLMNeitherautomaticallyormanuallydependingonitsoperatingmode,seesections4.2.2and4.2.3.TheMSnormallyoperatesonitshomePLMN.However,anotherPLMNmaybeselectedif,forexample,theMSlosescoverage.TheMSwill

registerona

PLMNiftheMSfindsasuitablecelltocamponandifalocationupdating

requestisaccepted.RegistrationhastobesuccessfulinorderfortheMStobe

abletoaccessthatnetwork.However,itdoesnotneedtoperformlocation

updatingifitisinthesamelocationareabelongingtothesamePLMNasit

wasbeforeitenteredtheinactivestate.

TheMScanselectandregisteronanotherPLMNofitshomecountrythanits

homePLMNifnationalroamingispermitted.However,theMSwillthendo

periodicalattemptstoreturntoitshomePLMN.

TherearetwomodesforPLMNselection;automaticandmanual.The

automaticmodeutilisesalistofPLMNsinanorderofprioritywhereasthe

manualmodeleavesthedecisiontotheuserandonlyindicateswhichPLMNs

thatareavailable.

4.2.2Automaticmode

Inautomaticmode,theMSwillselectPLMNifavailableandallowable,inthe

followingorderifnoregisteredPLMNexistorisavailable:

1）homePLMN,

2）eachPLMNthathavebeenstoredintheSubscriberIdentityModule（SIM）

inpriorityorder,

3）otherPLMNswithreceivedsignallevelabove-85dBminrandomorder,

4）allotherPLMNsinorderofdecreasingsignalstrength.

4.2.3Manualmode

Inmanualmode,theMSwillfirsttrytoselecttheregisteredPLMNorhome

PLMNifnoregisteredPLMNexist.Ifthisregistrationfailsoriftheuserhave

initiatedaPLMNreselectiontheMSwillindicatetotheuserallavailable

PLMNs.TheusercanthenselectadesiredPLMNwhichcausestheMSto

initiatearegistrationonthisPLMN.IftheselectedPLMNisnotallowable,an

indicationtotheusertoselectanotherPLMNwillbemade.

TheusercanatanytimerequesttheMStoinitiatereselectionandregistration

ontoanalternativeavailablePLMN.Thisisdoneeitherusingautomaticor

manualmode,dependingonthemodeselectedbytheuser.

4.3Cellselection

4.3.1General

Thecellselectionalgorithmtriestofindthemostsuitablecelloftheselected

PLMNaccordingtovariousrequirements.Ifnosuitablecellisfoundandall

availableandallowablePLMNshavebeentried,theMSwilltrytocampona

cellirrespectiveofPLMNidentityandenteralimitedservicestateenablingit

tomakeonlyemergencycallsifnecessary.IftheMSlosescoverageitwill

returntothePLMNselectionstateandselectanotherPLMN.

Twodifferentstrategiescanbeusedduringcellselection;normalcellselection

orstoredlistcellselection.StoredlistcellselectionutilisesastoredBCCH

Allocation（BA）listtospeedupthecellselectionprocedurewhereasnormal

cellselectionisperformedwhennosuchlistisavailable.

4.3.2Algorithm

Normalcellselection

Duringnormalcellselection,theMSwilltrytoselectthemostsuitablecellto

campon.

Acellisconsideredsuitableif:

?

itbelongstotheselectedPLMN,

?

itisnotbarred（whenacellisbarreditwillnotbecampedonbyanMSinidlemodebutanactiveMScanperformhandovertoit）,

?

itdoesnotbelongtoalocationareawhichisinthelistofForbidden

locationareasfornationalroaming_1,

?

thecellselectioncriterionisfulfilled.

WhentheMShasnoinformationonwhichBCCHcarriersthatareusedinthenetwork,itwillsearchall124RFchannelsintheGSM900system,or374forDCS1800,takemeasurementsamplesofreceivedRFsignalstrengthandcalculatethereceivedaveragelevelforeach.TheaveragingisbasedonatleastfivesamplesperRFcarrierspreadevenlyovera3to5secondperiod.

TheMSthentunestothecarrierwiththehighestaveragesignalstrengthlevel

anddetermineswhetherthiscarrierisaBCCHcarrierbysearchingforthe

frequencycorrectionburstsentontheFrequencyCorrectionChannel（FCCH）.

IfitisaBCCHcarrier,thentheMStunestothatcarriertoreadthe

SynchronisationChannel（SCH）fortheBSICparameter,andtheBCCHforthe

systeminformationmessages,forexampletheBAlist.Ifthedatais

successfullydecodedandthecellissuitable,theMScampsonitandperforms

allregistrationsnecessary.Ifatleastthe30strongestGSM900or40strongest

DCS1800RFchannelshavebeentriedandnosuitablecellswerefound,the

MSwillselectanotherPLMNaccordingtothePLMNselectionprocedureand

searchforsuitablecellsthere.Formultibandoperation,RFchannelsfromboth

frequencybandsareevaluatedduringcellselection,seeref.1.

Cellscanhavetwolevelsofpriority;normalandlow.Suitablecellsthatareof

lowpriorityareonlycampedoniftherearenoothersuitablecellsofnormal

1OnlyvalidformobilessupportingGSMphase2.NationalroamingmaybeallowedonlytocertainlocationareasofaanotherPLMNthanthehome

PLMN.Thoselocationareasthatareforbiddenwill,afteranattempttodoalocationupdatinghasfailed,bestoredintheSIMasforbiddenlocationarea

fornationalroaming.ThislistwillbeclearedwhenthemobileispoweredoffortheSIMisremoved.

priority.ApriorityofacelliscontrolledbytheCellBarQualifyparameter,

CBQ1,inconjunctionwiththeCellBarAccess,CB,parameter,seetable1.

Table1BehaviouroftheMSfordifferentcombinationsofCBQandCB.

2/1551-FCU101201UenRevB1996-11-079（IftheMSfindsacellthatispartoftheselectedPLMNbutnotsuitable,the

MSwillusetheBAlistobtainedfromthatcellandsubsequentlyonlysearch

thoseBCCHcarriers.Thiswillspeeduptheproceduretosomeextent.

TheBAlistisdefinedbytheMBCCHNOparameter.ItindicatestotheMS

thefrequenciesthatmustbemonitoredandmeasuredbothinidleandactive

mode.Itispossibletodefineseparatelistsforidleandactivemodeas

describedinDoubleBA-lists,ref.2.Thepresentdocumentonlyconsidersthe

idleBAlist.TheBAlistissenttotheMS,inidlemode,inthesystem

informationmessagesontheBCCH.Upto32BCCHcarrierscanbedefined

byspecifyingtheirARFCNusingtheMBCCHNOparameter.

Storedlistcellselection

TheMSmayincludeoptionalstorageoftheBAlistwhenitispoweredoff.

ThisinformationisstoredintheSIM.Forexample,theMSmaystoretheBA

listinusebythePLMNselectedwhentheMSwaslastactiveintheGSMor

DCSnetwork.

IfanMSincludesastoredBAlistoftheselectedPLMN,itwillperformthe

samemeasurementsasfornormalcellselectionexceptthatonlytheBCCH

carriersinthelistwillbescanned.TheBAlistforagivenPLMNstoredinthe

MSwillberesetandupdatedwhenevertheMSretrievesnewBCCHdatafrom

thatPLMN.Ifastoredlistcellselectionisnotsuccessful,thennormalcell

selectiontakesplace.

Cellselectioncriterion

Whileinidlemode,theMScontinuouslycalculatesthecellselectionquantity,

C12.ThecellselectioncriterionissatisfiedifC1>0.

ThequantityC1isc