LTE切换优化专题-参数功能和优化思路

内容：参数功能及设置、切换原理、信令流程、优化案例等。1LTE切换原理1.1Intra-eNodeB切换触发事件：A3事件（同频切换），A5事件（异频切换）当UE从当前所处的服务小区切换到同一eNodeB下的另一小区时，会发生Intra-eNodeB切换。基于X2接口的切换触发事件：A3事件（同频切换），A5事件（异频切换）当两个eNodeB之间存在X2接口时，UE从当前所驻留的服务小区切换到另一eNodeB时，可采用基于X2接口的切换。基于S1接口的切换触发事件：A3事件（同频切换），A5事件（异频切换）当两个eNodeB之间不存在X2接口，或X2接口不可用时，UE从当前所驻留的服务小区切换到另一eNodeB时，可采用基于S1接口的切换。1.1.1LTE到3G的切换实现LTE到3G的切换首先需要满足几个前提：1.网络侧，LTE系统和3G系统均支持LTE到3G的PS切换2.UE侧，UE需要支持LTE到3G的PS切换，UE的FeatureGroupIndicatorbit位8和bit位22数值必须为1。LTE到3G切换的流程概述：1.LTE基站如果收到UE上报的A2测量报告，发现LTE的覆盖较差。2.LTE基站通过RRC重配置消息对UE配置B2事件的测量的相关参数。3.LTE基站收到B2事件的测量报告后，通过MobilityFromEutranCommand通知UE发起到3G的切换。4.LTE基站收到UE上发的MobilityToUtranComplete，切换成功。主要的LTERRC空口信令：UE上报B2测量报告：MeasurementReportUE在LTE小区收到往3G切换命令：MobilityFromEutranCommandUE向LTE小区反馈到3G切换成功：MobilityToUtranComplete具体的切换信令流程如下：1．切换准备信令流程（3GPP23.401）UESourceeNodeBTargetRNCSourceMMETargetSGSNServingGWHSS1.HandoverInitiation2.HandoverRequired3.ForwardRelocationRequest5.RelocationRequest5a.RelocationRequestAcknowledge8.CreateIndirectDataForwardingTunnelRequest7.ForwardRelocationResponsePDNGW8a.CreateIndirectDataForwardingTunnelResponseUplinkandDownlinkUserPlanePDUsTargetServingGW4.CreateSessionRequest4a.CreateSessionResponse6.CreateIndirectDataForwardingTunnelRequest6a.CreateIndirectDataForwardingTunnelResponse2．切换执行信令流程（3GPP23.401）UESourceeNodeBTargetRNCSourceMMETargetSGSNServingGWHSSPDNGWUplinkandDownlinkUserPlanePDUs1.HandoverCommand2.HOfromE-UTRANCommand-Sendingofuplinkdatapossible4.UTRANIuAccessProcedures5.RelocationComplete6.ForwardRelocationComplete6a.ForwardRelocationCompleteAcknowledge7.ModifyBearerRequest8a.ModifyBearerResponse9.ModifyBearerResponseUplinkandDownlinkUserPlanePDUs(ViaTargetSGSNifDirectTunnelisnotused)4a.HandovertoUTRANCompleteDownlinkUserPlanePDUsIfDirectForwardingappliesIfIndirectForwardingapplies.TargetServingGW(A)8.ModifyBearerRequestViaTargetSGSNincaseDirectTunnelisnotused10.RouteingAreaUpdateprocedure11.DeleteSessionRequest(B)11a.DeleteSessionResponse11b.ReleaseResourcesForServingGWrelocationSteps7,8and9,andthefollowingUserPlanepath,willbehandledbyTargetServingGW12.DeleteIndirectDataForwardingTunnel1.1.2LTE到2G的切换LTE到2G的具体切换信令流程：1.切换准备信令流程（3GPP23.401）UESourceeNodeBTargetBSSSourceMMETargetSGSNServingGWHSS1.HandoverInitiation2.HandoverRequired3.ForwardRelocationRequest5.PSHandoverRequest5a.PSHandoverRequestAcknowledge8.CreateIndirectDataForwardingTunnelRequest7.ForwardRelocationResponsePDNGW8a.CreateIndirectDataForwardingTunnelResponseUplinkandDownlinkUserPlanePDUsTargetServingGW4.CreateSessionRequest4a.CreateSessionResponse6.CreateIndirectDataForwardingTunnelRequest6a.CreateIndirectDataForwardingTunnelResponse2.切换执行信令流程（3GPP23.401）UESourceeNodeBTargetBSSSourceMMETargetSGSNServingGWHSSPDNGWUplinkandDownlinkUserPlanePDUs1.HandoverCommand2.HOfromE-UTRANCommandSendingofuplinkdatapossible4.GERANA/GbAccessProcedures5.XIDResponse6.PSHandoverComplete8.ForwardRelocationCompleteNotification8a.ForwardRelocationCompleteAcknowledge9.ModifyBearerRequest11.ModifyBearerResponseUplinkandDownlinkUserPlanePDUs7.XIDResponse12.XIDNegotiationforLLCADM12a.SABMUAexchangere-establishmentandXIDnegotiationforLLCABM)DownlinkUserPlanePDUsOnlyif”DirectForwarding”appliesTargetServingGWForServingGWrelocationSteps9,10and11,andthefollowingUserPlanepath,willbehandledbyTargetServingGW(A)10.ModifyBearerRequest10a.ModifyBearerResponse13.RouteingAreaUpdateprocedure14b.ReleaseResource14.DeleteSessionRequest(B)14a.DeleteSessionResponseOnlyif”IndirectForwarding”applies1.1.33G到LTE的切换3G到LTE的具体切换信令流程：1.切换准备信令流程（3GPP23.401）UESourceRNCTargeteNodeBSourceSGSNTargetMMEServingGWHSS1.HandoverInitiation2.RelocationRequired3.ForwardRelocationRequest5.HandoverRequest5a.HandoverRequestAcknowledge8.CreateIndirectDataForwardingTunnelRequest7.ForwardRelocationResponsePDNGW8a.CreateIndirectDataForwardingTunnelResponseUplinkandDownlinkUserPlanePDUs(viaSourceSGSNincaseDirectTunnelisnotused)6.CreateIndirectDataForwardingTunnelRequest6a.CreateIndirectDataForwardingTunnelResponseTargetServingGW4.CreateSessionRequest4a.CreateSessionResponse2.切换执行信令流程（3GPP23.401）UESourceRNCTargeteNodeBSourceSGSNTargetMMEServingGWHSSPDNGWUplinkandDownlinkUserPlanePDUs(viaSourceSGSNifDirectTunnelisnotused)1.RelocationCommand2.HOfromUTRANCommand4.E-UTRANAccessProcedures5.HOtoE-UTRANComplete6.HandoverNotify7.ForwardRelocationCompleteNotification7a.ForwardRelocationCompleteAcknowledge8.ModifyBearerRequest9a.ModifyBearerResponse10.ModifyBearerResponseUplinkandDownlinkUserPlanePDUsDownlinkPayloadUserPlanePDUs(viaSourceSGSNifDirectTunnelisnotused)IfDirectForwardingappliesIfIndirectForwardingappliesTargetServingGWForServingGWrelocationSteps8,9and10,andthefollowingUserPlanepath,willbehandledbyTargetServingGW(A)9.ModifyBearerRequest11.TrackingAreaUpdateprocedure12.DeleteSessionRequest(B)12a.DeleteSessionResponse12b.IuReleaseProcedureSendingofuplinkdatapossible13.DeleteBearerViaSourceSGSNincaseDirectTunnelisnotused1.1.42G到LTE的切换2G到LTE的具体切换信令流程：1.切换准备信令流程（3GPP23.401）UESourceBSSTargeteNodeBSourceSGSNTargetMMEServingGWHSS1.HandoverIni