2019独角兽企业重金招聘Python工程师标准>>> 
一、在主叫未收到振铃消息前发生srvcc
UE在LTE下发起VOLTE电话，由于4G信号差，在响铃之前触发了SRVCC，怀疑该网络不support bsrvcc（响铃之前SRVCC），导致SRVCC失败，进一步导致Call自动挂断。
395304 01-18 11:59:21.108425 7448 7469 I VoLTE_Auto_Testing: [0][acct] event/recv/srvcc/start
395305 01-18 11:59:21.108516 7448 7469 I VoLTE UA: call_session_release_session_not_transferred_in_srvcc: release the session, call_id=[1] (vendor/mediatek/proprietary/frameworks/opt/volte/volte_ua/src/call/call.c:863)
395306 01-18 11:59:21.111770 7448 7469 I VoLTE_Auto_Testing: [0][call] msg/send/0/1/resp/480/request_id=596902168/conn_id=131073
395331 01-18 11:59:21.114558 7448 7469 I VoLTE UA: SRVCC: call [1] send 480_TEMP_UNAVAILABLE, res=[0] (vendor/mediatek/proprietary/frameworks/opt/volte/volte_ua/src/call/call.c:875)
395336 01-18 11:59:21.115375 7448 7469 I VoLTE_Auto_Testing: [0][call] event/send/0/1/ecpi/133/0/0/3/mode/0/cause/21/q850/0/pau/
395379 01-18 11:59:21.118427 7448 7469 I VoLTE_Auto_Testing: [0][call] event/srvcc_call_ctxt_transfer/0
1、从log看网络已经成功切换了，之后发了[IMSP_AT_I s23]AT+ESRVCCTFR=0
->0代表0通call从IMS切换到CS失败
This command is used for transferring IMS call table to CS domain.
After transfer successfully, modem will report Unsolicited Result Code +ESRVCCTFR:
If transfer fails, modem will report Unsolicited Result Code +ESRVCCTFR: 0
+ESRVCCTFR=
67249669, 11:59:20:666 2017/01/18, MOD_ERRC_MOB, , TRACE_PEER, [MS->NW] ERRC_MeasurementReport[13] eventB2 GSM ncell[60/0] rslt[-363][0] pcell[38950/28] rslt[-466][-30]
275966, 0, 67256774, 11:59:21:266 2017/01/18, MOD_ERRC_CONN, , TRACE_PEER, [NW->MS] ERRC_MobilityFromEUTRACommand(CSFB:[0],purpose:[MobilityFromEUTRACommand_r8_IEs_purpose_handover_selected],targetRAT:[Handover_targetRAT_Type_geran])
277501, 0, 67258573, 11:59:21:266 2017/01/18, MOD_RRM_TDD, , TRACE_PEER, [MS->NW] RR_HANDOVER_COMPLETE //srvcc切换到2G
2、从哪里check到srvcc失败？？
->从上面AT++ESRVCCTFR=0或者以下log都可以看出SRVCC失败（前面贵司贴的MD log只是接入网部分的成功，但并不是完整的SRVCC的切换，SRVCC还得考虑IMS域和CS域的call session transfer是否成功）
395305 01-18 11:59:21.108516 7448 7469 I VoLTE UA: call_session_release_session_not_transferred_in_srvcc: release the session, call_id=[1] (vendor/mediatek/proprietary/frameworks/opt/volte/volte_ua/src/call/call.c:863)
395306 01-18 11:59:21.111770 7448 7469 I VoLTE_Auto_Testing: [0][call] msg/send/0/1/resp/480/request_id=596902168/conn_id=131073
395331 01-18 11:59:21.114558 7448 7469 I VoLTE UA: SRVCC: call [1] send 480_TEMP_UNAVAILABLE, res=[0] (vendor/mediatek/proprietary/frameworks/opt/volte/volte_ua/src/call/call.c:875)
395336 01-18 11:59:21.115375 7448 7469 I VoLTE_Auto_Testing: [0][call] event/send/0/1/ecpi/133/0/0/3/mode/0/cause/21/q850/0/pau/
395379 01-18 11:59:21.118427 7448 7469 I VoLTE_Auto_Testing: [0][call] event/srvcc_call_ctxt_transfer/0
->终端不用上报SRVCC成功给网络，SRVCC是网络控制的。贵司可参考23.216先学习
☆一般来说如果网络支持bSRVCC会在网络给的invite或者183中的feature-caps中带有pre-alerting，请问您是在哪里进行的测试？目前来说中国移动的bSRVCC验证测试主要是春节后在杭州长沙两地进行。对比机测试是请您使用其他平台的手机，用相同的卡做振铃前的SRVCC测试,感谢您的配合。