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1、LTE 典型信令过程Software Architecture 3类NAS信令流程 1. 会话管理相关 2. 位置管理相关 3. 鉴权管理相关UEeNBMMESGWPGWRRC: RRC Connection setup complete NAS: Attach Request NAS:PDN connectivity requestS1AP: Initial UE messageAuthentication and NAS security procedureHSSS6a: Update Location requestS6a: Update Location answerS11: Crea
2、te bearer requestS5: Create bearer requestS5: Create bearer response S11: Create bearer responseS1AP: Initial Context setup requestNAS: Attach accept NAS: Activate Default EPS bearer requestNAS: Attach Request NAS:PDN connectivity requestRRC: RRCConnectionReconfigurationNAS: Attach accept NAS: Activ
3、ate Default EPS bearer requestRRC: RRCConReconfigCompleteS1AP: Initial Context setup responseRRC: UL information TransferNAS: Attach complete NAS: Activate Default EPS bearer acceptS1AP: Uplink NAS TransportNAS: Attach complete NAS: Activate Default EPS bearer acceptUE initiated Detach ProcedureUEeN
4、BMMESGWPGWHSSRRC: RRC Connection setup complete NAS: Detach requestS1AP: Initial UE messageNAS: Detach requestAuthentication and NAS security S11: Delete session request S5: Delete session requestS5: Delete session responseS11: Delete session responseS1AP: Downlink NAS transportNAS: Detach acceptRRC
5、: DLInformation transferNAS: Detach acceptRadio and S1 ReleaseS6a: TDelay purge timer expires S6a: Purge UE request S6a: Purge UE answer UE Triggered Service Request ProcedureInitial UE MessageNetwork Triggered Service RequestTAU procedureInter MME-TAU-message flowHandoverHandover Air InterfaceTYPES
6、 OF HANDOVER X2 Based Handover : without SGW change and with SGW change S1 Based Handover : with eNB, MME and SGW changeX2 Handover X2 is the interface between two eNBs and X2-AP is the protocols used for communication over it. The handover is directly performed between two eNodeBs. Handover takes p
7、lace when the eNB detects that UE can no longer be served by it because of the power constraints. The MME is only informed at the end of the handover procedure once the handover is successful The release of resources at the source side is directly triggered from the target eNB.RRC: Connection Reconf
8、iguration RequestRRC: Connection Reconfiguration CompleteUES-eNBT-eNBMMESGWRRC: Measurement Control X2AP: Handover RequestS11: Modify bearer requestS11: Modify bearer responseX2AP: SN Status TransferSyncUL Allocation + TA for UEUL Allocation RRC: Measurement Report Handover DecisionX2AP: Handover Re
9、sponseUE Detach from old cell and sync to new cellS1AP: Path Switch RequestS1AP: Path Switch Response X2AP: UE Context ReleaseEnd MarkerSwitch DL PathData ForwardingData ForwardingEnd MarkerFlush DL BufferS1 Handover This type of handover takes place when there is no X2 connectivity between source e
10、NB and target eNB. Both eNBs are served by different MMEs. SGWs can also be different. Source eNB is served by source MME and source SGW while target eNB is served by target MME and target SGW. Source and target MMEs can communicate over S10 interface. All the handover decisions are taking place on
11、S1 interface, its called as S1 based handover. UET-eNBS-MMET-MMET-SGWS10: Forward Relocation Request S11: Create Session RequestS11: Create Session ResponseS1AP: eNB Status TransferS1AP: Handover Required S1AP: Handover RequestUE Detach from old cell and sync to new cellS11: Modify Bearer RequestS1A
12、P: UE Context Release CommandS-eNBS-SGWPGWHandover DecisionS1AP: Handover Request AckS10: Forward Relocation ResponseS1AP: Handover CommandRRC: Connection ReconfigurationRRC: Connection Reconfiguration CompleteS1AP: Handover NotifyS11: Modify Bearer ResponseS5: Modify Bearer RequestS1AP: UE Context
13、Release CompleteS11: Delete Session RequestS11: Delete Session ResponseS1AP: MME Status TransferS10: Forward SRNS Context NotificationS10: Forward SRNS Context AckS10: Forward Relocation CompleteS10: Forward Relocation Complete AckS5: Modify Bearer Response开始 Before the UE can do anything, a Radio R
14、esource Control connection must be established. The RRC is a logical connection between the UE and E-UTRAN. There are two different RRC states: RRC IDLE RRC CONNECTEDRRC IDLE This state indicates that there is no signaling radio bearer is established i.e. no RRC connection is established. The UE is
15、considered RRC_IDLE once it obtains the center frequency, reads the timing information, syncs to the eNodeB, and is ready to receive system broadcast information. UE monitors a paging channel to detect incoming calls. UE can performs neighboring cell measurements and measurement reporting.RRC CONNEC
16、TED This state indicates that there is signaling radio bearer established i.e. RRC connection is established. Transfer of unicast data to/from an UE. The UE Monitors control channels associated with the shared data channel to determine if data is scheduled for it. The UE Provides channel quality and feedback information. The UE Perform neighboring cell measurements and measurement reporting. Radio Resource Control (RRC)
