LTE系统概述及全网信令流程

0LTE系统全网信令流程IntroductionAsanewwirelessmobilecommunicationtechnology,LTE(LongTermEvolution)provideallkindsofservicesthroughnetworkaccessprocedures.SowhenyouaretryingtounderstandtheLTEtechnology,thenetworkaccessprocedureisjustintheclosefrontofyoureyes.ThisdocumentistryingtodescribethegeneralprocedurehandlingsamongthenetworkelementsunderLTEnetworkarchitecture,bywayofshowingyoutheprocedurehandlingsinfigures.Fromthesefigures,youwillgetanoverviewoftheLTEgeneralprocedures,suchas:“TheSystemInformationHandling”,“TheRandomAccessProcedure”,“TheAttachProcedure”,“TheTAUProcedure”,“TheHandoverProcedure”,etc.Thefirstseveralfiguresshowtheintroductionofprotocollayerstacksamongnetworkelements,suchas:protocollayerstacks“betweenUE-MME”,“betweenUE-PDNGW”,etc.Fromtheseprotocollayerstacksintroduction,youwilllearnthepeer-to-peerprotocollayersamongseveralrelatednetworkelements,itwillhelpyoutounderstandLTEprocedures’workingmechanismstuff.Andafter,beginsthedescriptionoftheLTEgeneralprocedure,inanorderfrom“Systeminformationhandling”to“ANRMeasurementprocedure”,withthe“accessprocedure”,“handoverprocedure”,“inter-RAToperationprocedure”,……,inthemiddle.Fromtheseprocedurefiguresdescription,youcangetthedeepdetailsoftheLTEnetworkaccessprocedure,anditwillfinallydirectyoutofoundawhole-system-viewofLTEarchitecture.ThisdocumentissuitablefortheguyswhowanttoknowtheLTEgeneralprocedure,oruseitasareferencebook.2009-11-061AbbreviationsMMEMobilityManagementEntityUEUserEquipmentMSMobileStationeNodeBevolvedNodeBGWGateWayPCRFPolicyandChargingRulesFuctionH-PCRFHome-PCRFV-PCRFVisited-PCRFHSSHomeSubscriberServerEIREquipmentIdentityRegisterUTRANUniversalTerrestrialRadioAccessNetworkE-UTRANevolvedUTRANGERANGSM/EDGERadioAccessNetworkPLMNPublicLandMobileNetworkHPLMNHomePLMNVPLMNVisitedPLMNHLRHomeLocationRegisterVLRVisitorLocationRegisterCBCCellBroadcastCentreOMCOperationandMaintenanceCenterBSCBaseStationControlerBTSBaseTransceiverStationBSSBaseStationSubsystemCNCoreNetworkMSC/SGSNMobile-servicesSwitchingCentre/ServingGPRSSupportNodeInter-RATRadioAccessTechnologyMBMSMediaBroadcastandMulticastSystemMCEMulti-cell/multicastCoordinationEntityRNCRadioNetworkControler2NetworkelementsfunctionseNodeBfunctions:-Headercompressionanduserplaneciphering;-MMEselectionwhennorouteingtoanMMEcanbedeterminedfromtheinformationprovidedbytheUE;-ULbearerlevelrateenforcementbasedonUE-AMBRandMBRviameansofuplinkscheduling(e.g.bylimitingtheamountofULresourcesgrantedperUEovertime);-DLbearerlevelrateenforcementbasedonUE-AMBR;-ULandDLbearerleveladmissioncontrol;-Transportlevelpacketmarkingintheuplink,e.g.settingtheDiffServCodePoint,basedontheQCIoftheassociatedEPSbearer.MMEfunctions:-NASsignalling;-NASsignallingsecurity;-InterCNnodesignallingformobilitybetween3GPPaccessnetworks(terminatingS3);-UEReachabilityinECM-IDLEstate(includingcontrolandexecutionofpagingretransmission);-TrackingArealistmanagement;-PDNGWandServingGWselection;-MMEselectionforhandoverswithMMEchange;-SGSNselectionforhandoversto2Gor3G3GPPaccessnetworks;-Roaming(S6atowardshomeHSS);-Authentication;-Authorization;-Bearermanagementfunctionsincludingdedicatedbearerestablishment;-LawfulInterceptionofsignallingtraffic;-Warningmessagetransferfunction(includingselectionofappropriateeNB);-UEReachabilityprocedures.SGSNfunctions:-InterEPCnodesignallingformobilitybetween2G/3GandE-UTRAN3GPPaccessnetworks;-PDNandServingGWselection:theselectionofS-GW/P-GWbytheSGSNisasspecifiedfortheMME;-MMEselectionforhandoverstoE-UTRAN3GPPaccessnetwork.3NetworkelementsfunctionsServingGWfunctions:-thelocalMobilityAnchorpointforinter-eNodeBhandover;-sendingofoneormoreendmarkertothesourceeNodeB,sourceSGSNorsourceRNCimmediatelyafterswitchingthepathduringinter-eNodeBandinter-RAThandover,especiallytoassistthereorderingfunctionineNodeB.-Mobilityanchoringforinter-3GPPmobility(terminatingS4andrelayingthetrafficbetween2G/3GsystemandPDNGW);-ECM-IDLEmodedownlinkpacketbufferingandinitiationofnetworktriggeredservicerequestprocedure;-LawfulInterception;-Packetrouteingandforwarding;-Transportlevelpacketmarkingintheuplinkandthedownlink,e.g.settingtheDiffServCodePoint,basedontheQCIoftheassociatedEPSbearer;-Accountingforinter-operatorcharging.ForGTP-basedS5/S8,theServingGWgeneratesaccountingdataperUEandbearer;-InterfacingOFCSaccordingtochargingprinciplesandthroughreferencepointsspecifiedinTS32.240[51].PDNGWfunctions:-Per-userbasedpacketfiltering(bye.g.deeppacketinspection);-LawfulInterception;-UEIPaddressallocation;-Transportlevelpacketmarkingintheuplinkanddownlink,e.g.settingtheDiffServCodePoint,basedontheQCIoftheassociatedEPSbearer;-Accountingforinter-operatorcharging;-ULandDLservicelevelchargingasdefinedinTS23.203[6](e.g.basedonSDFsdefinedbythePCRF,orbasedondeeppacketinspectiondefinedbylocalpolicy);-InterfacingOFCSthroughaccordingtochargingprinciplesandthroughreferencepointsspecifiedinTS32.240[51].-ULandDLservicelevelgatingcontrolasdefinedinTS23.203[6];-ULandDLservicelevelrateenforcementasdefinedinTS23.203[6](e.g.byratepolicing/shapingperSDF);-ULandDLrateenforcementbasedonAP