Section: 5.2.4 Call establishment for SRVCC or vSRVCC 5.2.4.1 General
Content: Before call establishment for SRVCC or vSRVCC can be initiated in the mobile station, the MM connection must be established by the network. At PS to CS domain change from S1 mode or Iu mode due to SRVCC handover or vSRVCC handover (see 3GPP TS 23.216[ Single Radio Voice Call Continuity (SRVCC); Stage 2 ]  [126]), the RR sublayer in the MS indicates to the MM layer if a voice only SRVCC handover or a voice and video SRVCC handover was completed successfully. At reception of this indication, the MS that supports SRVCC or vSRVCC shall establish an MM connection as specified in subclause 4.5.1.8 and either proceeds with subclause 5.2.4.2 if the indication is that voice only SRVCC was completed successfully or proceeds with subclause 5.2.4.2a if the indication is that voice and video SRVCC was completed successfully. At 5G-SRVCC handover from NG-RAN to UTRAN (see 3GPP TS 23.216[ Single Radio Voice Call Continuity (SRVCC); Stage 2 ]  [126]), the RR sublayer in the MS indicates to the MM layer if 5G-SRVCC handover from NG-RAN to UTRAN was completed successfully. At reception of this indication, the MS that supports 5G-SRVCC handover from NG-RAN to UTRAN shall establish an MM connection as specified in subclause 4.5.1.8 and proceeds with subclause 5.2.4.2 if the indication is that 5G-SRVCC handover from NG-RAN to UTRAN was completed successfully.