Combining Circuit Switched (CS) and IP Multimedia Subsystem (IMS) services; Stage 3
The present document provides the technical realisation for the combination of Circuit Switched calls and IM sessions when using them simultaneously between the same two users.
The present document describes the use of CS and IM services in combination, using the existing procedures that have been defined for CS and IMS. It includes the necessary function as adding an IM session to an ongoing CS call, adding a CS call to an ongoing IM session, supplementary services as they relate to CSICS and supporting capability exchange.
The present document is applicable to UE and Application Servers providing for the combination of Circuit Switched calls and IM sessions.