The Telecom Protocols

SRVCC enables continuity of voice call anchored in IMS network, when UE changes its access network from packet based in eUTRAN to circuit based GERAN or UTRAN, without requiring the UE to have simultaneous access to both the radio network.   It accomplishes this by enhancing the MMEs, serving E-UTRAN and the 3GPP CS MSC serving GERAN/UTRAN such that when the UE is still anchored within the E-UTRAN network and triggers a measurement report indicating a need for handover (HO) to GERAN/UTRAN, the MSC can initiate IMS service continuity procedure towards the IMS domain in addition to preparing for a handover into its GERAN/UTRAN access, before the UE is directed to change its access network to GERAN/UTRAN.     The SRVCC feature requires the new Sv interface between MSC and MME. Sv Interface runs over UDP. Following messages are exchanged over Sv Interface:   - PS to CS Request - PS to CS Response - PS to CS Complete Notification - PS to CS ...

BICC Bearer establishment procedures: Four variants of BICC IP bearer set-up procedures are defined: -             Fast Forward -             Delayed Forward -             Fast Backward -             Delayed Backward  Those procedures differ on the way the bearer control information are exchanged, and on whether an APM (Connected) message shall be sent by the originating BICC node once the bearer is ready for use. -             Bearer control information exchanges : -             In Fast bearer setup (forward or backward) and in delayed forward bearer establishment procedures, the IP bearer establishment is done in the ...

Here is UMTS subscriber call flow with the core network. MS-A                                               MSC                                                      MS-B **************************************************************************************************** -------Initial_UE(CM_SERVICE_REQ) -->| ------------Dir_Trnx(AUTH_REQ)         <--| -------------Dir_Trnx(AUTH_RSP)         -->| ---------------SecurityModeCmd            <--| --------------SecurityModeComp           -->| -----Dir_Trnx(TMSI_RELOC_CMD)   <--| ----Dir_Trnx(TMSI_RELOC_COMP)  -->|   -------------...

Location Update Flow : ***********************************************************************  Mobile Station                                                                 MSC ************************************************************* ----------------------Initial_UE(CM_SERVICE_REQ)  -->| ---------------------------Dir_Trnx(AUTH_REQ)         <--| ---------------------------Dir_Trnx(AUTH_RSP)          -->| -----------------------------Cipher Mode Command     <--| -----------------------------Cipher Mode Complete      -->| ---------------------Dir_Trnx(TMSI_RELOC_CMD)   <--| ----------------------Dir_Trnx(LOCUPD_ACCEPT)    <--| ------------------------TMSI_RELOC_COMP     ...