LTE 切换信令流程文档格式.docx
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LTE 切换信令流程文档格式.docx
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TheseproceduresareusedtohandoveraUEfromasourceeNodeBtoatargeteNodeBusingtheX2referencepoint.IntheseprocedurestheMMEisunchanged.TwoproceduresaredefineddependingonwhethertheServingGWisunchangedorisrelocated.InadditiontotheX2referencepointbetweenthesourceandtargeteNodeB,theproceduresrelyonthepresenceofS1-MMEreferencepointbetweentheMMEandthesourceeNodeBaswellasbetweentheMMEandthetargeteNodeB.
ThehandoverpreparationandexecutionphasesareperformedasspecifiedinTS
36.300
[5].IfemergencybearerservicesareongoingfortheUEhandovertothetargeteNodeBisperformedindependentoftheHandoverRestrictionList.TheMMEchecks,aspartoftheTrackingAreaUpdateintheexecutionphase,ifthehandoveristoarestrictedareaandifsoMMEreleasesthenon-emergencybearersasspecifiedinclause
5.10.3.
IftheservingPLMNchangesduringX2-basedhandover,thesourceeNodeBshallindicatetothetargeteNodeB(intheHandoverRestrictionList)thePLMNselectedtobethenewServingPLMN.
WhentheUEreceivesthehandovercommanditwillremoveanyEPSbearersforwhichitdidnotreceivethecorrespondingEPSradiobearersinthetargetcell.Aspartofhandoverexecution,downlinkandoptionallyalsouplinkpacketsareforwardedfromthesourceeNodeBtothetargeteNodeB.WhentheUEhasarrivedtothetargeteNodeB,downlinkdataforwardedfromthesourceeNodeBcanbesenttoit.UplinkdatafromtheUEcanbedeliveredviathe(source)ServingGWtothePDNGWoroptionallyforwardedfromthesourceeNodeBtothetargeteNodeB.OnlythehandovercompletionphaseisaffectedbyapotentialchangeoftheServingGW,thehandoverpreparationandexecutionphasesareidentical.
IftheMMEreceivesarejectiontoaNASprocedure(e.g.dedicatedbearerestablishment/modification/release;
locationreportingcontrol;
NASmessagetransfer;
etc.)fromtheeNodeBwithanindicationthatanX2handoverisinprogress(seeTS
[5]),theMMEshallreattemptthesameNASprocedureeitherwhenthehandoveriscompleteorthehandoverisdeemedtohavefailed,exceptincaseofServingGWrelocation.ThefailureisknownbyexpiryofthetimerguardingtheNASprocedure.
IfduringthehandoverproceduretheMMEdetectsthattheServingGWneedsberelocated,theMMEshallrejectanyPDNGWinitiatedEPSbearer(s)requestreceivedsincehandoverprocedurestartedandshallincludeanindicationthattherequesthasbeentemporarilyrejectedduetohandoverprocedureinprogress.TherejectionisforwardedbytheServingGWtothePDNGW,withthesameindication.
UponreceptionofarejectionforanEPSbearer(s)PDNGWinitiatedprocedurewithanindicationthattherequesthasbeentemporarilyrejectedduetohandoverprocedureinprogress,thePDNGWstartalocallyconfiguredguardtimer.ThePDNGWshallre-attempt,uptoapre-configurednumberoftimes,wheneitheritdetectsthatthehandoveriscompletedorhasfailedusingmessagereceptionoratexpiryoftheguardtimer.
IftheMMEreceivesarejectiontoaUEContextModificationRequestmessagewithaCSFallbackindicatorfromtheeNodeBwithanindicationthatanX2handoverisinprogress,theMMEshallresendaUEContextModificationRequestmessagewithCSFallbackindicatortothetargeteNodeBwhenthehandoveriscompleteortothesourceeNBwhenthehandoverisdeemedtohavefailed.
1.1.2X2-basedhandoverwithoutServingGWrelocation
ThisprocedureisusedtohandoveraUEfromasourceeNodeBtoatargeteNodeBusingX2whentheMMEisunchangedanddecidesthattheServingGWisalsounchanged.ThepresenceofIPconnectivitybetweentheServingGWandthesourceeNodeB,aswellasbetweentheServingGWandthetargeteNodeBisassumed.
Figure1.1.2-1:
X2-basedhandoverwithoutServingGWrelocation
NOTE
1:
ForaPMIP-basedS5/S8,proceduresteps(A)aredefinedinTS
23.402
[2].
1.ThetargeteNodeBsendsaPathSwitchRequestmessagetoMMEtoinformthattheUEhaschangedcell,includingtheTAI+ECGIofthetargetcellandthelistofEPSbearerstobeswitched.IfthetargetcellisaCSGcell,thetargeteNodeBincludestheCSGIDofthetargetcellinPathSwitchRequestmessage.Ifthetargetcellisinhybridmode,itincludestheCSGIDofthetargetcellandCSGAccessModesetto"
hybrid"
inthePathSwitchRequestmessage.TheMMEdeterminestheCSGmembershipbasedontheCSGIDandCSGAccessModereceivedfromthetargeteNodeB.TheMMEupdatestheUserCSGinformationbasedontheCSGIDandCSGAccessModereceivedfromthetargeteNodeBandCSGmembershipifoneoftheparametershaschanged.
2:
X2handoverbetweenHeNBsispossiblewhenthehandoverisbetweenclosed/hybridaccessHeNBshavingthesameCSGIDorwhenthetargetHeNBisanopenaccessHeNB.
TheMMEdeterminesthattheServingGWcancontinuetoservetheUE
2.TheMMEsendsaModifyBearerRequest(eNodeBaddress(es)andTEIDsfordownlinkuserplanefortheacceptedEPSbearers,ISRActivated)messageperPDNconnectiontotheServingGWforeachPDNconnectionwherethedefaultbearerhasbeenacceptedbythetargeteNodeB.IfthePDNGWrequestedUE'
slocationinfo,theMMEalsoincludestheUserLocationInformationIEinthismessage.IftheUETimeZonehaschanged,theMMEincludestheUETimeZoneIEinthismessage.IftheServingNetworkhaschanged,theMMEincludesthenewServingNetworkIEinthismessage.IfISRwasactivatedbeforethisprocedure,MMEshouldmaintainISR.TheUEisinformedabouttheISRstatusintheTrackingAreaUpdateprocedure.IftheServingGWsupportsModifyAccessBearersRequestprocedureandifthereisnoneedfortheSGWtosendthesignallingtothePGW,theMMEmaysendModifyAccessBearersRequest(eNodeBaddress(es)andTEIDsfordownlinkuserplanefortheacceptedEPSbearers,ISRActivated)perUEtotheServingGWtooptimizethesignalling.
IfthePDNGWrequestedUE'
sUserCSGinformation(determinedfromtheUEcontext),theMMEincludestheUserCSGInformationIEinthismessageiftheUserCSGInformationhaschanged.
TheMMEusesthelistofEPSbearerstobeswitched,receivedinstep
1,todeterminewhetheranydedicatedEPSbearersintheUEcontexthavenotbeenacceptedbythetargeteNodeB.TheMMEreleasesthenon-accepteddedicatedbearersbytriggeringthebearerreleaseprocedureasspecifiedinclause
5.4.4.2.IftheServingGWreceivesaDLpacketforanon-acceptedbearer,theServingGWdropstheDLpacketanddoesnotsendaDownlinkDataNotificationtotheMME.
IfthedefaultbearerofaPDNconnectionhasnotbeenacceptedbythetargeteNodeBandtherearemultiplePDNconnectionsactive,theMMEshallconsiderallbearersofthatPDNconnectionasfailedandreleasethatPDNconnectionbytriggeringtheMMErequestedPDNdisconnectionprocedurespecifiedinclause
IfnoneofthedefaultEPSbearershavebeenacceptedbythetargeteNodeBorthereisaLIPAPDNconnectionthathasnotbeenreleased,theMMEshallactasspecifiedinstep
6.
3.IftheServingGWhasreceivedtheUserLocationInformationIEand/ortheUETimeZoneIEand/ortheServingNetworkIEand/orUserCSGInformationIEfromtheMMEinstep
2theServingGWinformsthePDNGW(s)aboutthisinformationthate.g.canbeusedforcharging,bysendingthemessageModifyBearerRequest(ServingGWAddressandTEID,UserLocationInformationIEand/orUETimeZoneIEand/orServingNetworkIEand/orUserCSGInformationIE)perPDNconnectiontothePDNGW(s)concerned.TheServingGWshallreturnaModifyBearerResponse(ServingGWaddressandTEIDforuplinktraffic)messagetotheMMEasaresponsetoaModifyBearerRequestmessage,oraModifyAccessBearersResponse(ServingGWaddressandTEIDforuplinktraffic)asaresponsetoaModifyAccessBearersRequestmessage.IftheServingGWcannotservetheMMERequestintheModifyAccessBearersRequestmessagewithoutS5/S8signallingorwithoutcorrespondingGxcsignallingwhenPMIPisusedovertheS5/S8interface,itshallrespondtotheMMEwithindicatingthatthemodificationsarenotlimitedtoS1-Ubearers,andtheMMEshallrepeatitsrequestusingModifyBearerRequestmessageperPDNconnection.
4.TheServingGWstartssendingdownlinkpacketstothetargeteNodeBusingthenewlyreceivedaddressandTEIDs.AModifyBearerResponsemessageissentbacktotheMME.
5.InordertoassistthereorderingfunctioninthetargeteNodeB,theServingGWshallsendoneormore"
endmarker"
packetsontheoldpathimmediatelyafterswitchingthepathasdefinedinTS
[5],clause
10.1.2.2.
6.TheMMEconfirmsthePathSwitchRequestmessagewiththePathSwitchRequestAckmessage.IftheUEAMBRischanged,e.g.alltheEPSbearerswhichareassociatedtothesameAPNarerejectedinthetargeteNodeB,theMMEshallprovidetheupdatedvalueofUEAMBRtothetargeteNodeBinthePathSwitchRequestAckmessage.
IfsomeEPSbearershavenotbeenswitchedsuccessfullyinthecorenetwork,theMMEshallindicateinthePathSwitchRequestAckmessagewhichbearersfailedtobeestablished(seemoredetailinTS
36.413
[36])andfordedicatedbearersinitiatethebearerreleaseprocedureasspecifiedinclause
5.4.4.2toreleasethecorenetworkresourcesofthefaileddedicatedEPSbearers.ThetargeteNodeBshalldeletethecorrespondingbearercontextswhenitisinformedthatbearershavenotbeenestablishedinthecorenetwork.
IfnoneofthedefaultEPSbearershavebeenswitchedsuccessfullyinthecorenetworkoriftheyhavenotbeenacceptedbythetargeteNodeBortheLIPAPDNconnectionhasnotbeenreleased,
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