移動(dòng)手機(jī)為啥讀取WCDMA信號(hào)-LTE案例

移動(dòng)手機(jī)為啥讀取WCDMA信號(hào)--LTE案例1.背景介紹4月26日中國(guó)移動(dòng)VOLTE例行測(cè)試中終端在LTE網(wǎng)絡(luò)先后發(fā)起業(yè)務(wù)和TAU請(qǐng)求；而在TAU拒絕回送BYE請(qǐng)求后，讀取WCDMA網(wǎng)絡(luò)消息顯示聯(lián)通3G圖標(biāo)；最后終端選擇駐留GSM網(wǎng)絡(luò)，繼續(xù)語(yǔ)音測(cè)試任務(wù)；中國(guó)移動(dòng)4G終端為什么會(huì)在業(yè)務(wù)測(cè)試中讀聯(lián)通3G網(wǎng)絡(luò)信息呢？讓我們對(duì)整個(gè)事件和信令消息，對(duì)照3GPP規(guī)范做一下回顧和分析；

圖表1.終端由LTE到GSM流程消息2.業(yè)務(wù)請(qǐng)求和TAU拒絕終端在(TAC:13643CELLID:9951513)小區(qū)于16:10:58.824和16:10:58.825發(fā)起業(yè)務(wù)請(qǐng)求(ServiceRequest）和TAU請(qǐng)求(圖2）；Log回放顯示:終端發(fā)起業(yè)務(wù)請(qǐng)求后，MAC層的RACH接入失?。▓D3）；而終端發(fā)起TAU請(qǐng)求時(shí)MAC層的RACH成功（圖4）；網(wǎng)絡(luò)TAU拒絕EMMCause=111Protocolerror,unspecified（圖5）；

圖表2.終端發(fā)起業(yè)務(wù)和TAU請(qǐng)求

圖表3.業(yè)務(wù)請(qǐng)求后RACH失敗

圖表4.TAU請(qǐng)求和RACH成功

圖表5.終端TAU被拒絕3.TAU請(qǐng)求和拒絕定義（3GPP24.301）5.5.3Trackingareaupdatingprocedure(S1modeonly)ThetrackingareaupdatingprocedureisalwaysinitiatedbytheUEandisusedforthefollowingpurposes:-

normaltrackingareaupdatingtoupdatetheregistrationoftheactualtrackingareaofaUEinthenetwork;.7

Abnormalcasesonthenetworkside

IftheTRACKINGAREAUPDATEREQUESTmessagehasbeenreceivedwithaprotocolerror,thenetworkshallreturnaTRACKINGAREAUPDATEREJECTmessagewithoneofthefollowingEMMcausevalues:

#96:invalidmandatoryinformationelementerror;

#99:informationelementnon-existentornotimplemented;

#100:

conditionalIEerror;or

#111:

protocolerror,unspecified.4.終端脫網(wǎng)后PLMN搜索16:11:08.083終端接收到服務(wù)小區(qū)（TAC13643eNodeB9951513SectorID3PCI498）信號(hào)良好（RSRP-97.68SINR10.30，下圖左）；而16:11:08.084服務(wù)小區(qū)無(wú)信號(hào)(下圖右)，判斷：底層鏈路中斷，終端脫網(wǎng)。

圖表6.網(wǎng)絡(luò)底層鏈路中斷前后16:11:08.084終端進(jìn)入(EMMREGISTEREDNOCELLAVAILABLE)

狀態(tài);NAS層啟動(dòng)(GMM_PLMN_SEARCH)網(wǎng)絡(luò)搜索流程;

圖表7.NAS層GMM觸發(fā)PLMN搜索TS24.301clause.5Ifthetrackingareaupdatingcannotbeacceptedbythenetwork,theMMEsendsaTRACKINGAREAUPDATEREJECTmessagetotheUEincludinganappropriateEMMcausevalue.UponreceivingtheTRACKINGAREAUPDATEREJECTmessage,theUEshallstoptimerT3430,stopanytransmissionofuserdata,andtakethefollowingactionsdependingontheEMMcausevaluereceived.

5.PLMN搜索協(xié)議規(guī)定TS23.122

3.5

Nosuitablecell(limitedservicestate)ThereareanumberofsituationsinwhichtheMSisunabletoobtainnormalservicefromaPLMN.Theseinclude:a)

FailuretofindasuitablecelloftheselectedPLMN;b)

NoSIMintheMS;c)

A"PLMNnotallowed"responsewhenanLRisreceived;d)

An"illegalMS"or"illegalME"responsewhenanLRisreceived(AnySIMintheMEisthenconsidered"invalid");e)

An"IMSIunknowninHLR"responsewhenanLRisreceived(AnySIMintheMEisthenconsidered"invalid"fornon-GPRSservices);f)

A"GPRSservicesnotallowed"responsewhenanLRofaGPRSMSattachedtoGPRSservicesonlyisreceived(ThecellselectionstateofGPRSMSsattachedtoGPRSandnon-GPRSdependsontheoutcomeofthelocationupdating),oran"EPSservicesnotallowed"responseisreceivedwhenanEPSattach,trackingareaupdateorservicerequestisperformed;org)

Powersavingmode(PSM)isactivated(see3GPP

TS

23.682

[27A]).(InautomaticPLMNselectionmode,itemsa,candfwouldnormallycauseanewPLMNselection,buteveninthiscase,thesituationmayarisewhennoPLMNsareavailableandallowableforuse).

3GPP36.304小區(qū)選擇和重選5.2

CellselectionandreselectionTheNAScancontroltheRAT(s)inwhichthecellselectionshouldbeperformed,forinstancebyindicatingRAT(s)associatedwiththeselectedPLMN,andbymaintainingalistofforbiddenregistrationarea(s)andalistofequivalentPLMNs.TheUEshallselectasuitablecellbasedonidlemodemeasurementsandcellselectioncriteria.Inordertospeedupthecellselectionprocess,storedinformationforseveralRATsmaybeavailableintheUE.Whencampedonacell,theUEshallregularlysearchforabettercellaccordingtothecellreselectioncriteria.Ifabettercellisfound,thatcellisselected.ThechangeofcellmayimplyachangeofRAT.Detailsonperformancerequirementsforcellreselectioncanbefoundin[10].圖表8

LTE終端網(wǎng)絡(luò)搜索流程圖6.UMTS網(wǎng)絡(luò)搜索根據(jù)3GPP36.304（5.2）16:11:16.069和16:11:23.683終端分別搜到TDSCDMA和WCDMA網(wǎng)絡(luò)：

圖表9終端對(duì)TD+WCDMA網(wǎng)絡(luò)搜索7.GSM重選駐留16:11:39.139搜索到GSM網(wǎng)絡(luò)，根據(jù)3GPP36.133重選到GSM網(wǎng)絡(luò)；

圖表10

終端搜索GSM網(wǎng)絡(luò)7.1小區(qū)重選（3GPP36.133）4.2

CellRe-selection4.2.1

IntroductionThecellreselectionprocedureallowstheUEtoselectamoresuitablecellandcamponit.WhentheUEisineitherCampedNormallystateorCampedonAnyCellstateonacell,theUEshallattempttodetect,synchronise,andmonitorintra-frequency,inter-frequencyandinter-RATcellsindicatedbytheservingcell.Forintra-frequencyandinter-frequencycellstheservingcellmaynotprovideexplicitneighbourlistbutcarrierfrequencyinformationandbandwidthinformationonly.UEmeasurementactivityisalsocontrolledbymeasurementrulesdefinedinTS36.304,allowingtheUEtolimititsmeasurementactivity.4.2.2

RequirementsTheUEshallsearcheverylayerofhigherpriorityatleasteveryThigher_priority_search=(60*Nlayers)secondswhentheUEisnotconfiguredwitheDRX_IDLEcycle,andatleasteveryThigher_priority_search=MAX(60*Nlayers,oneeDRX_IDLEcycle)whenUEisconfiguredwitheDRX_IDLEcycle,whereNlayersisthetotalnumberofconfiguredhigherpriorityE-UTRA,UTRAFDD,UTRATDD,CDMA20001xandHRPDcarrierfrequenciesandisadditionallyincreasedbyoneifoneormoregroupsofGSMfrequenciesisconfiguredasahigherpriority.16:12:20.849在GSM網(wǎng)絡(luò)LUA完成和駐留（LAC13888CELLID17131）小區(qū)。

圖表11

終端駐留GSM網(wǎng)絡(luò)8.GSM語(yǔ)音呼叫根據(jù)業(yè)務(wù)請(qǐng)求（測(cè)試計(jì)劃）在呼叫失敗后，終端于16:13.02