A.17.1 Introduction

24.2373GPPIP Multimedia (IM) Core Network (CN) subsystem IP Multimedia Subsystem (IMS) service continuityRelease 17Stage 3TS

The signalling flows in the subclause demonstrate how sessions in alerting phase can be transferred from PS to CS using PS to CS SRVCC procedures. The following signalling flows are included:

– subclause A.17.2 shows an example of PS to CS SRVCC transfer where the incoming call is in alerting phase.

– subclause A.17.3 shows an example of PS to CS SRVCC transfer where the outgoing call is in alerting phase.

– subclause A.17.4 shows an example of PS to CS SRVCC transfer where the incoming call is in alerting phase, but the user answers the call in the PS domain prior to the completion of the network handover procedures and the UE retuning to the CS domain.

– subclause A.17.5 shows an example of PS to CS SRVCC transfer where the incoming call is in alerting phase, but the user answers the call in the PS domain prior to the completion of the network handover procedures but the handover to CS does not succeed.

– subclause A.17.6 shows an example of PS to CS SRVCC transfer where the outgoing call is in alerting phase and the UE has received several forked responses prior to the initiation of access transfer.