LTE-X2接口原理介绍

LTE协议原理课程目标：了解LTE协议架构了解LTE系统帧结构了解LTE系统各层功能i目录第1章缩略语...............................................................................................................................................11.1LTE整体架构.....................................................................................................................................1第2章X2AP功能.......................................................................................................................................32.1X2AP功能..........................................................................................................................................3第3章X2AP进程.......................................................................................................................................53.1基本过程............................................................................................................................................53.2基本移动性过程................................................................................................................................63.2.1切换准备..................................................................................................................................63.2.2切换未成功操作......................................................................................................................83.2.3SN状态传输.............................................................................................................................93.2.4UE上下文释放.......................................................................................................................103.2.5切换取消................................................................................................................................113.3全局进程..........................................................................................................................................123.3.1负载标示................................................................................................................................123.3.2错误指示................................................................................................................................133.3.3X2口配置...............................................................................................................................143.3.4重置........................................................................................................................................163.3.5ENB更新配置........................................................................................................................173.3.6资源状态上报初始化............................................................................................................203.3.7资源状态上报........................................................................................................................221第1章缩略语知识点LTE缩略语1.1LTE整体架构为了便于说明，本文使用如下缩写词。DLDownlinkEARFCNE-UTRAAbsoluteRadioFrequencyChannelNumbereNBE-UTRANNodeBEPElementaryProcedureEPCEvolvedPacketCoreE-RABE-UTRANRadioAccessBearerE-UTRANEvolvedUTRANGUMMEIGloballyUniqueMMEIdentifierHFNHyperFrameNumberIEInformationElementMMEMobilityManagementEntityPDCPPacketDataConvergenceProtocolPLMNPublicLandMobileNetworkS-GWServingGatewaySNSequenceNumberTACTrackingAreaCodeUEUserEquipmentULUplink3第2章X2AP功能知识点移动性管理负载管理X2接口管理2.1X2AP功能X2AP协议提供如下功能：●移动性管理。此功能允许eNB将对特定UE的承载转移到另一个eNB上。用户平面数据前向传输，状态传输以及UE文本发布功能都是移动性管理的一部分。●负载管理。此功能允许eNB互相通知资源状态，过载以及传输负载。●X2复位。此功能用于重置X2接口。●配置X2。此功能用于为eNB交换必要数据，以便于配置X2接口以及执行X2的复位。●eNB配置更新。此功能允许更新两个eNB需求的应用层数据，以保证X2接口上的正确交互。上述功能与X2EP之间的对应关系见下表。表2.1-1X2AP功能与X2APEP的对应关系FunctionElementaryProcedure(s)MobilityManagementa)HandoverPreparationb)SNStatusTransferc)UEContextReleased)HandoverCancelLoadManagementa)LoadIndicationb)ResourceStatusReportingInitiationc)ResourceStatusReportingReportingofGeneralErrorSituationsErrorIndicationLTE协议原理4FunctionElementaryProcedure(s)ResettingtheX2ResetSettinguptheX2X2SetupeNBConfigurationUpdateeNBConfigurationUpdate5第3章X2AP进程知识点基本过程移动性过程全局进程3.1基本过程在下表中，所有的EP都被分为类型1和类型2两种EP。表3.1-1类型1基本过程ElementaryProcedureInitiatingMessageSuccessfulOutcomeUnsuccessfulOutcomeResponsemessageResponsemessageHandoverPreparationHANDOVERREQUESTHANDOVERREQUESTACKNOWLEDGEHANDOVERPREPARATIONFAILUREResetRESETREQUESTRESETRESPONSEX2SetupX2SETUPREQUESTX2SETUPRESPONSEX2SETUPFAILUREeNBConfigurationUpdateENBCONFIGURATIONUPDATEENBCONFIGURATIONUPDATEACKNOWLEDGEENBCONFIGURATIONUPDATEFAILUREResourceStatusReportingInitiationRESOURCESTATUSREQUESTRESOURCESTATUSRESPONSERESOURCESTATUSFAILURE表3.1-2类型2基本过程ElementaryProcedureInitiatingMessageLoadIndicationLOADINFORMATIONHandoverCancelHANDOVERCANCELSNStatusTransferSNSTATUSTRANSFERUEContextReleaseUECONTEXTRELEASEResourceStatusReportingRESOURCESTATUSUPDATEErrorIndicationERRORINDICATIONLTE协议原理63.2基本移动性过程3.2.1切换准备●综述此进程用于在eNB端建立必要的资源，用于即将开始的切换。此进程使用UE相关的信令。●成功操作sourceeNBHANDOVERREQUESTHANDOVERREQUESTACKNOWLEDGEtargeteNB图3.2-1切换准备，成功运行源eNB通过发送HANDOVERREQUEST消息到目的eNB来完成进程的初始化。当源eNB发送HANDOVERREQUEST消息时，应该启动计时器TRELOCprep。根据Alloca