基本原理优化交流培训

VoLTEFundamentalVoLTEIntroductionWhatisVoLTE?LTE(LongtermEvolution)aka4G,isthewirelesscommunicationsstandarddevelopedby3GPPstandardization,toofferhighspeedwithlowlatency.LTEispacket-switchednetworkonly.LTEnetworkarchitecturedoesnotincludethetraditional2G/3Gvoiceservices.VoiceoverLTEisthesolutiontoprovidetheVoiceservicecapabilitybasedonGSMAIR.92specification.-Realtimetraffic-QualityofService-InteroperabilitytoexistingCSvoicenetworkIPMultimediaSubsystem(IMS)enablesintegratedvoice,dataandmulti-mediaservicesinterworkingbetweendifferentaccessnetworks.IMSisbasedonSIPcallcontrolforcreating,modifying,andterminatingsessions.VoLTENetworkArchitectureOverviewCSCF（CallSessionControlFunction）：多媒体呼叫会话过程中的信令控制MGCF（MediaGatewayControlFunction）：执行IMS与CS域的互通；不同域间协议转换MGW（MediaGateway）：连接不同域的用户面；不同网络之间的编解码转换VoLTEBearerCombinationTheVoIPservicehasspecificbearercombinationrequirements：-QCI1dedicatedbearerforvoicecall.-QCI2dedicatedbearerforvideocall.-QCI5dedicatedbearerforSIPsignallingtotheIMS.-Defaultnon-GBRbearer(QCI8-9)fordatatransfer(always-on).QCIGuaranteePriorityDelaybudgetLossrateApplication1GBR2100ms1e-2VoIP2GBR4150ms1e-3Videocall3GBR5300ms1e-6Streaming4GBR350ms1e-3Realtimegaming5Non-GBR1100ms1e-6IMSsignalling6Non-GBR7100ms1e-3Interactivegaming7Non-GBR6300ms1e-6TCPprotocols:browsing,email,filedownload8Non-GBR8300ms1e-69Non-GBR9300ms1e-6VoLTESignalingOverviewSIPProtocolStack-TheSessionInitiationProtocol(SIP)isanapplication-layercontrol(signaling)protocolforcreating,modifying,andterminatingsessionswithoneormoreparticipantsdevelopedbyIETF–RFC3261.-SIPistransferredusingQCI5bearer.VoLTERegistration为什么要注册：-用户使用IMPU（IPMultimediaPublicIdentity）通信-建立用户当前的IP与其IMPU的对应关系-掌握用户当前的位置信息及业务能力-注册过程的鉴权与认证保证了网络的安全性什么时候注册：-用户开机、解除飞行模式、SiM卡丢失重读注意：-用户需注册上网络才能开始进行VoLTE注册，终端必须支持VoLTE功能，VoLTE注册伴随着网络注册支持VoLTE终端：

-HTCM8、Iphone6/6s、三星S6/note4、华为P7/MATE7、LGG3、SONYZ3等-商用终端需进行软件升级开启VoLTE功能VoLTERegistrationUEattachestothenetwork,thePGWassignsIPaddressandidentifiesP-CSCFtotheterminal.UEsendsRegistrationRequesttoS-CSCF(viaP-CSCF)inREGISTERmessage.S-CSCFperformsregistrationprocedureswithHSSandacquiresuserauthenticationinformationandsendsUEachallengein401Unauthorizedmessage.UEcalculatestheresponseandsendsittoS-CSCFinREGISTERmessage.AftertheauthenticationhassucceededtheS-CSCFdownloadsandstoresservicecontrolinformationfromHSSandS-CSCFnotifiestheterminalaboutcompletedregistrationwith200OKmessage.VoLTERegistration现阶段常见问题：

-终端侧未发起PDN连接请求-网络下发PDN连接拒绝已注册未注册VoLTECallFlowMOUEgeneratesanINVITErequest,whichissenttotheIMS.NotethatMOUEincludesQoSpreconditionsintheSDPwhichindicatesthatMOUEdoesnotwantMTUEtobealerteduntiltherearenetworkresourcesreservedinbothdirections.TheP-CSCFacknowledgestheINVITEtotheMOUEwith"100Trying”messageindicatingthatthecallsetupisinprogress.TheSIPmethodOPTIONSallowsaIMStoqueryanotherUEoraproxyserverastoitscapabilities.Thisallowsaclienttodiscoverinformationaboutthesupportedmethods,contenttypes,extensions,codecs,etc.With200OKmessageUEanswerswithitscapabilitiestoIMS.TheINVITEmessagereceivedbyMTUEincludesdeclarationforusingprecondition,typeofmedia,codectouseandtheprotocolfortransportingthemediaintheSDP.Moredetailreferto3GPP24228-5f07.2.3.1/7.4.3.1VoLTECallFlowWhenpreconditionmechanismissupportedP-CSCFwouldsend183SessionProgresstooriginatingUEwhichthencomparestheterminatingUEcapabilitieswithitsownanddeterminesthecodectobeused.OriginatingUEnotifiestheterminatingUEusingPRACKtheselectedcodec.200OKisreceivedfromterminatingUE.EPSBearerActivationfollowsforbothUEs.TheUPDATEmessagesindicatesthatpreconditiononMOUEsideismet.BothterminalsconfirmthesetupofbearerwithQoSaccordingto200OKmessageandterminatingUEstartringing.The180RingingmessageisinitiatedfromMTtoIMSandthenIMSforwardsthe‘Ringingmessage’toMOUE.OncebothUEsreceive200OK,theyACKitandtheSIPsessionisestablished-voicecommunicationstarts.Precondition对于双方的UE而言，建立PDP上下文的执行过程是相互独立的。这意味着在资源被成功预留之前，根本无法保证所协商的媒体会话是否可以建立起来。因此，Precondition作用主要是为了保证在确认本地和主叫方的资源预留都已成功之前，被叫方不应振铃,以最大程度减少被叫方振铃但接听电话又失败的情况若INVITERequest消息中携带Precondition字段，表明终端支持该功能。不支持Precondition功能的呼叫流程主叫被叫AMRFrameTypeModeIndicationModeRequestFramecontent(AMRmode,comfortnoise,orother)000AMR4,75kbit/s111AMR5,15kbit/s222AMR5,90kbit/s333AMR6,70kbit/s(PDC-EFR)444AMR7,40kbit/s(TDMA-EFR)555AMR7,95kbit/s666AMR10,2kbit/s777AMR12,2kbit/s(GSM-EFR)8--AMRSID9--GSM-EFRSID10--TDMA-EFRSID11--PDC-EFRSID12-14--Forfutureuse15--NoData(Notransmission/Noreception)FrameTypeIndexModeIndicationModeRequestFramecontent(AMR-WBmode,comfortnoise,orother)000AMR-WB6.60kbit/s111AMR-WB8.85kbit/s222AMR-WB12.65kbit/s333AMR-WB14.25kbit/s444AMR-WB15.85kbit/s555AMR-WB18.25kbit/s666AMR-WB19.85kbit/s777AMR-WB23.05kbit/s888AMR-WB23.85kbit/s9--AMR-WBSID(ComfortNoiseFrame)10-13--Forfutureuse14--speechlost15--NoData(Notransmission/Noreception)AMR=AdaptiveMulti-Rate，“自适应多速率编码”，主要用于移动设备的音频AMR又称为AMR-NB，抽样频率为8KHz，语音带宽范围为300－3400HzAMR-NB

共有16种编码方式，0-7对应8种不同的编码方式，8-15用于噪音或者保留用AMR-WB=AdaptiveMulti-rate-Wideband，“自适应多速率宽带编码”，抽样频率为16KHz，语音带宽范围为50－7000HzAMR-WB是一种同时被国际标准化组织ITU-T和3GPP采用的宽带语音编码标准，也称为G722.2标准AMR-NBAMR-WBMediaNegotiation媒体协商：主叫和被叫UE在会话的建立过程中需要对媒体的类型和编码方式达成一致，为此使用SDP请求和应答机制对媒体进行协商；双方所协商的媒体类型包括视频、音频、文本等；媒体协商过程：支持的语音编码类型VoLTEAudioCall主叫被叫支持Precondition功能的呼叫流程VoLTEVideoCall呼叫流程释放流程VoLTECallFlow现阶段遗留问题：-被叫VOLTE终端回落至GSM，但仍未接通（核心网尚未定位到原因）-终端强锁4G导致被叫VOLTE终端收到CSPaging或未收到寻呼消息VOLTEPerformanceMOS值：高清>OTT>标清；资源占用：高清≈标清<OTT；

QCI1<QCI9；端到端时延：高清≈标清<OTT；接入时延：VoLTE(2s)<GSM<CSFB；中移已确认采用高清语音MOS、PLR、Delay、下行RB数、下行MCS与SINR直接相关：当SINR低于15后，由于小区间切换、TM模式切换等原因，MOS值抖动频繁，略微呈现下降趋势；当SINR低于3后，MOS值开始大幅度下降，其他指标也开始出现不同程度恶化；SuggestionsforOptimizationinthefuture网格道路优化：VoLTE语音质量（MOS）与端到端PLR、delay直接相关，需更加注重以下几点：更少的小区间乒乓切换更少的TM模式切换避免SINR低于3dB的质差路段eSRVCCIntroductionWhatisSRVCC?SRVCC=SingleRadioVoiceCallContinuitySRVCCfunctionalityisstandardizedbythe3GPPandtheideabehindthisfeatureistohandoverongoingVoIPcallfromLTEtoanotherRATwithsimultaneouschangeofthedomainthatservestheconnection–fromPStolegacyCS3GPPR8/R9solution

eSRVCCNetworkarchitecture

eSRVCC架构在拜访网络中引入了接入侧的锚定点，锚定点包括两部分逻辑实体：-ATCF：AccessTransferControlFunctionality-ATGW：AccessTransferGatewayATCF在呼叫过程中及接入侧转换后始终参与在会话控制平面中，eSRVCC发生时，负责控制来自本地CS域新媒体通道的转换，无需更新远端呼叫分支，并控制ATGW对媒体面进行锚定，将本地媒体面切换到MGW上，其余媒体面保持不变。。3GPPR10solutioneSRVCCCallFlowUE(A-Party)CSCF

(B-Party)MMEeNBBSC/RNCIMSRegistration(SIP)IMSRegistration(SIP)DedicatedEPSBearerSetupforVoIPpacketsIMSVoiceCallSetup(SIP)MeasurementReports1.eNB:HODecision2.HandoverRequiredPS-BearerSplitting(notshown)3.PS-to-CSRequest(IMSI,Target-ID,STN-SR)theMSC-SreservesresourcesintheRANandalsoattheMGW8.PS-to-CSResponse9.HandoverCommand10.HandoverCommand12.HandoverComplete13.PS-to-CSComplete/Ack

19.SIPBYEATCFconfiguresATGWwithSDP=MGWwhichswitchesthebearerfrom

PDN-GE(LTE)totheMGW(CS)5.SIPInvite(STN-SR,SDP=MGW)SCC-AS

(A-Party)DeactivationofDedicatedEPSBearerforVoIPUE

(B-Party)I-/S-CSCF

(A-Party)MGWATCF/

ATGW

(A-Party)P-CSCF

(A-Party)theATCFisinthecallsetupandreservesresourcesattheAGW(anchorsthebearer)attheSIPSessionSetup6.SIP200OK7.SIPACK16.SIPInvite(withoutSDPupdate)17.SIP200OK18.SIPACKafteratimeout,theSCC-ASinitiatesthereleasethesourceaccesslegofthesession.DelayingtheSIPBYErequestenablestheUEtoaddGmcontrol(e.g.forvideo)andtoreusethedialogincaseofSRVCCcancellation.SincethereisnoSDPupdate,no

SIPRe-InviteissenttotheB-Party.PDN-GWNetworkAttachandDefaultEPSBearerSetupDedicatedEPSBearerSetupforVoIPpackets0.MMEreceivesSTN-SR

aspartoftheUserProfile.MediaPath(voice)4.HandoverRequest/Ack11.UEswitches

fromLTEto2G/3GMediaPath(voice)MSC-S15.MAPUpdate

Location

inHSS/HLRtheMMEinitiatesthereleaseoftheDedicatedEPSBearer.PCRF14.SessionTerminationIndication

(withPStoCShandoverindicator)TheUEwillreceivetheSIPBYEonlyiftheGm-interfaceisusedoverthe3GpacketbearerafterthePS-CSaccesstransferiscompleted.Moredetailreferto3GPP232166.2.2.1Case:issue19

终端表现：主叫上发INVITE-request后收到INVITE-trying，表面IMS已经收到INVITE-request并将其转发向被叫被叫始终没有收到网络侧paging消息，最终未接通或，10s后收到CS-paging开始进行CSFB如终端锁定LTEonlyIssue19和issue1终端现象完全一样issue19(pagingnoresponse终端未收到paging)Case:issue19

信令流程分析：S1ap消息跟踪MME已将s1paging下发到正确eNBEmil消息跟踪eNB已收到s1paging并将rrcpaging通过空口发向被叫UEUElog显示被叫终端未收到eNB下发的paging消息issue19(pagingnoresponse终端未收到pagingRrcpaging终端问题，已通过HTC终端补丁解决Case:issue1&issue19MMEpaging机制INTERNAL现网MMEpaging机制：第一次PSpaging后如未收到响应，每隔4s重复一次，共重复两次(间隔8s)；如仍未收到响应则通过SGs接口开始请求CSpaging。通常终端未收到PSpaging后会在10s-12s左右收到Cspaging开始进行CSFB。eSRVCCOptimizationCase现阶段遗留问题：-eSRVCC用户面中断时延大约为600ms，远高于中移300ms的要求-不支持VOLTE通话时重定向测控消除，小区覆盖边缘易出现重定向导致的VOLTE语音掉话，影响eSRVCC用户感知成功率SuggestionsforOptimizationinthefuture网格道路优化：VoLTE语音质量（MOS）与端到端PLR、delay直接相关，需更加注重以下几点：更少的小区间乒乓切换更少的TM模式切换避免SINR低于3dB的质差路段KPI指标：对于PS掉线率指标，现网中inactivitytimer设置为10s，与诺基亚掉线率新公式，掩盖了现网大量的无线问题，快速重建导致掉线不影响用户感知；但对于VOLTE语音，不切换或质差掉话直接影响客户感知，为避免大量的用户投诉，需注意以下几点：修改CIO等提升切换成功率的非常规方法不可行LTE系统内邻区与eSRVCC邻区维护纳入日常工作无线规划：考虑到福州站点故障率高的问题，更合理的邻区规划异常必要考虑到5%-10%的异系统切换，eSRVCC邻区中GSM工参需及时更新Appendix一阶段测试结果测试区域概述：测试区域共有站点数110个VoLTE基本功能测试版本RL35eSRVCC功能测试版本RL45基站版本LNT3.0_ENB_1304_251_03

LNT4.0_ENB_1311_455_01测试UEHTCM8测试软件CDS7.160BMOS盒惠捷朗基站版本

LNT4.0_ENB_1311_455_01测试UEHTCM8测试软件鼎立PilotPioneer9.2.1MOS盒鼎立MOS盒测试环境描述接通率掉话率测试场景标清高清接通率掉话率接通率掉话率道路遍历99.10%0.00%99.50%0.00%广场96.60%0.00%98.55%0.00%背街小巷100.00%0.00%97.00%0.00%居民楼92.86%2.50%87.01%1.50%Nokia:只考虑无线接通率大于99%，掉线率小于1%（未开启eSRVCC）

LTE接通成功率呼叫在LTE拨打的次数呼叫在LTE拨打成功的次数平均RSRP平均SINR平均接通时长室内定点-标清100%200200-121.90dbm-2.67db0.946s室内定点-高清100%200200-122.05dbm-2.33db0.699s室外定点-标清100%200