A.5.1 Introduction

24.2063GPPStage 3TSVoice call continuity between Circuit Switched (CS) and IP Multimedia Subsystem (IMS)

The signalling flows for call termination demonstrate how a terminating call to a VCC UE is anchored for the purposes of a future domain transfer. The following signalling flows are included:

– subclause A.5.2 shows a terminating call arriving at the IM CN subsystem, where incoming call routeing has directed the call to the IM CN subsystem for anchoring and subsequent delivery of the call to the terminating VCC UE;

– subclause A.5.3 shows a terminating call arriving at the IM CN subsystem, where incoming call routeing has directed the call to the IM CN subsystem for anchoring, but subsequently rerouted the call back to the CS domain for delivery to the terminating VCC UE;

– subclause A.5.4 shows a terminating call arriving at the CS domain, where CAMEL has been used to redirect the call to the IM CN subsystem for anchoring and subsequent delivery to the terminating VCC UE;

– subclause A.5.5 shows a terminating call arriving at the CS domain, getting routed to, and anchored at the IM CN subsystem, and subsequently routed back to the CS domain for delivery to the terminating VCC UE. The call routeing from the CS domain to the IM CN subsystem for anchoring is by the HSS(HLR), through internal network implementation, obtaining the IMRN for routeing to the IM CN subsystem;

– subclause A.5.6 shows a terminating call arriving at the IM CN subsystem, where incoming call routeing has directed the call to the IM CN subsystem for anchoring, but delivery to the terminating VCC UE in the IM CN subsystem has failed, and redelivery is made to the VCC UE in the CS domain;

– subclause A.5.7 shows a terminating call arriving at the CS domain, getting routed to, and anchored at the IM CN subsystem, and subsequently routed back to the CS domain for delivery to the terminating VCC UE, but delivery fails and redelivery is made to the VCC UE using the IM CN subsystem; and

– subclause A.5.8 shows a terminating call arriving at the CS domain, where CAMEL is used but for which the anchoring is denied; the call is continued and delivered in the CS domain.