CSFB主被叫信令流程介绍

UE是否具有GERAN/UTRAN重定向能力，通知给eNodeB及MME
MME代替UE向MSS执行LU过程。 如果LU过程成功，SGs的状态为SGs-ASSOCIATED。为用户建立了SGs关联，就是在VLR中存储了 用户的MME地址，同时也在MME中保存了用户的VLR的地址。 如在联合注册过程中，MSS给用户分配了新的TMSI，却未收到SGsAP-TMSI-REALLOCATIONCOMPLETE，不影响该用户SGs的状态。CS Paging时用IMSI代替TMSI。 如果UE驻留在GERAN/UTRAN时，MSS通过A/Iu正在Paging该UE。此时UE发起联合注册，MSS会 停止Paging，给MME返回SGsAP-LOCATION-UPDATE-ACCEPT 。 LU过程不成功，MSS发SGsAP-LOCATION-UPDATE-REJECT给MME。VLR将该用户的SGs状态置为 SGs-NULL。在下一次联合注册成功之前，所有的CSFB被叫被拒绝。
Location Update in CS domain
SecurityModeCommand UE CapabilityEnquiry SecurityModeComplete UE CapabilityInformation
InitialContextSetupRequest+ Attach Accept (combined EPS/IMSI attach,TAI,GUTI,LAI,TMSI,)+ ActivateDefault EPS Bearer Context Request(QCI,APN,PDN ADDRESS,QOS,APN-AMBR)
Attach Complete
如果在Attach Accept 包含新的TMSI
SGsAP-TMSI-REALLOCATION-COMPLETE
ActivateDefault EPS Bearer Context Accept
如果UE支持CSFB功能，会发起附着类型”Combined EPS/IMSI Attach”的附着请求。如果不支持 CSFB功能，附着类型为”EPS Attach”。
S6a-Update Location Request (MME name, IMSI) S6a-Update Location Accept(NAM =PACKET_AND_CIRCUIT) Modify Bearer Request Modify Bearer Response
TAI- LAI MSC/VLR
RRC Connection Reconfiguration+ Attach Accept(combined EPS/IMSI attach,TAI,GUTI,LAI,TMSI)
RRC Connection Reconfiguration Complete
InitialContextSetupResponse UE CapabilityInformationIndication
RRC连接建立
RRCConnectionSetupComplete+ExtendedServiceRequest (MO CS fallback,M-TMSI) ExtendedServiceRequest InitialContextSetupRequest(CS Fallback Required) InitialContextSetupResponse RRCConnectionRelease UEContextReleaseRequest(CS fallback triggered)
单卡双待手机
2 G
BTS/ NODEB
BSC/ RNC
MSS HLR
SIM 4 G
eNodeB
MME
仅在4G网络注册 进行主被叫时回落到GSM/TDS网络，结束后再返回4G网络。 接续时延稍长
CSFB手机
联合EPS/IMSI附着流程
UE eNB MME S/P-GW MSC/VLR HSS
主叫在2/3G，CSFB被叫在4G
UE
Um
BTS
A-bis
BSC
A
MSS/VLR
C
SGs
HLR/HSS
S6a LTE-Uu S1-MME
UE
eNodeB
MME
主叫路由 被叫路由
CSFB-MT(UE:ECM-IDLE)
MSS SGsAP-PAGING-REQUEST (IMSI,MME Name, CS CALL Indicator, TMSI,new LAI, Global CN-ID) MME
Random Access Sequence
RRC Connection Setup Request RRC Connection Request RRC Connection Setup Complete Attach request (Combined EPS/IMSI attach, GUTI,UE capacity,TAI,LAI)
如果MSS/VLR收到Detach Request或从A/Iu发起的LU，则将用户数据中的MME FQDN删除。在下一次联合TAU或联合注册之前， VLR不再通过SGS接口进行Paging。
联合注册流程 联合跟踪区更新流程 CSFB主被叫流程
CSFB主叫在4G，被叫在2/3G
UE
Um
BTS
A-bis
BSC
A
MSS/VLR
C
SGs
HLR/HSS
S6a LTE-Uu S1-MME
UE
eNodeB
MME
被叫路由 主叫路由
CSFB主叫流程
UE eNB MME MSS
Random Access Sequence
RRCConnectionSetupRequest RRCConnectionSetup
RRC连接建立
Stop Paging
SGsAP-SERVICE-REQUEST (IMSI,CS CALL INDICATOR, TAI,ECGI, UE ECM MODE:ECM-IDLE)
S1AP-InitialUEMessage+Extended service request (MT CS fallback,M-TMSI,CSFB response:Accept,ECGI,TAI) S1AP-InitialContextSetupRequest (cs-fallback-required,LAI) S1AP-InitialContextSetupResponse
CSFB-MO回落至2/3G后
UE BTS BSC MSS
Camp on BTS
System Infromation Type 3 (LAC = xxxx)
Location Update Request (Follow-on Request,CSMO Flag) Location Update Accept
RRC 连接 建立
如果NAM=ONLY_PACKET， MME不再向MSS发起 LU流程，直接给UE回送 TAU Accept
Tracking Area Update (TAU) Request (Active Flag: No Bearerestablished Req, InitialUEmessage + Combined TA/LA Update, TAU Request GUTI,UE capacity,TAI,LAI)
IMSI mod 1024
eNB
UE
S1AP-Paging (UEIdentityIndexValue : '1101101110'B, s-TMSI,cnDomain:cs,TAI )
Paging (s-TMSI,cnDomain:cs)
Random Access Sequence
RRCConnectionSetupRequest RRCConnectionSetup RRCConnectionSetupComplete+ExtendedServiceRequest (MT CS fallback,M-TMSI,CSFB response:Accept)
回落前后LAC有变化
CM Service Request(CSMO) CM Service Accept
。 。 。
在CSFB流程中，如果在2/3G网络中需要重新发起位置更 新，手机终端需要在位置更新请求消息中加入CSMO标 志，提示当前信令连接可以同时服务于后续的呼叫接续；
当MSC收到终端发起的位置更新请求时，MSC需要检查 请求消息中是CSMO标志： •MSS会更新相应的统计计数器。
RRC 连接 建立
如果NAM=ONLY_PACKET， MME不再向MSS发起 LU流程，直接给UE回送 TAU Accept
InitialUEmessage + AttachRequest+ PDN connectivity Request Identity request/response
S6a-Update Location Request (MME name, IMSI) S6a-Update Location Accept (NAM =PACKET_AND_CIRCUIT) Create Session req (IMSI, MSISDN, QoS, APN) Create Session resp (PDN add, TEID-C, TEID-U, EBI)
csfallback基本信令介绍2015may26郑州?联合注册流程?csfb主被叫流程?联合跟踪区更新流程sim2g4gbtsbscmssenodebmmebtsnodebbscrncmssenodebmmesim2g4ghlrhlr单卡双待手机csfb手机?在23g及4g网络同时注册?数据业务用4g网络?语音业务用23g网络接续时延短?23g与lte无需互操作?仅在4g网络注册?进行主被叫时回落到gsmtds网络结束后再返回4g网络
VLR 存储 MME FQDN
如果在SGsAP-Update Location Accept 包含新的TMSI
SGsAP-TMSI-REALLOCATION-COMPLETE
UEContextReleaseCommand (Normal Release) RRC Connection Release UEContextReleaseComplete
CS Fallback基本信令介绍
2015.May.26 郑州
联合注卡双待与CSFB手机的注册
2 G
BTS
BSC
MSS HLR
SIM 4 G
eNodeB
MME

在2/3G及4G网络同时注册 数据业务用4G网络 语音业务用2/3G网络，接续时延短 2/3G与LTE无需互操作
主叫流程中 没有任何 SGs接口信 令消息
Return to 2G
UEContextReleaseCommand(CS fallback triggered) UEContextReleaseComplete
Redirect consists of 3 phases: – Redirection decision phase (generation trigger for redirect) – Selection of redirect target based on UE capabilities and redirect priorities – Redirect execution
SGsAP-Update Location Request (LAI，IMSI, MME address)
TAI- LAI MSC/VLR
SecurityModeCommand SecurityModeComplete
SGsAP-Update Location Accept (VLR Num, TMSI)
联合注册流程 联合跟踪区更新流程 CSFB主被叫流程
联合TAU流程
UE eNB MME S/P-GW MSC/VLR HSS
Random Access Sequence
RRC Connection Setup Request RRC Connection Request RRC Connection Setup Complete
SGsAP-LOCATION-UPDATE-REQUEST (LAI，IMSI, MME FQDN)
Location Update in CS domain
SGsA-LOCATION UPDATE ACCEPT(VLR Num, TMSI)
TAU Accept (Combined TA/LA Updated,T3412,TAI,GUTI,LAI,TMSI) TAU Accept (Combined TA/LA Updated,T3412,TAI,GUTI,LAI,TMSI) TAU Complete