3 Definitions and abbreviations

23.2793GPPCombining Circuit Switched (CS) and IP Multimedia Subsystem (IMS) servicesRelease 17Stage 2TS

3.1 Definitions

For the purposes of the present document, the terms and definitions given in TR 21.905 [1] and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905 [1].

CSI session: a multimedia session that uses the CS domain to transport all or some media components (typically, voice) and the IMS/PS domain to transport the other media components. A CSI session can be created either by establishing first a CS call and subsequently a concurrent IMS session(s), or by establishing first an IMS session(s) and subsequently a concurrent CS call. From the user point of view, a CSI session is conceived as a single multimedia session.

Multimedia IMS session: a multimedia session that uses only the IMS/PS domain to transport both real-time and non-real-time media components.

CSI origination: the case when a UE initiates a CS call and subsequently adds an IMS session(s), or vice versa, addressed towards the same user.

CSI termination: the case when a call to a UE is terminated in the CS domain (e.g. for real-time component), while an IMS session(s) from the same originating user and towards the same UE is terminated in the IMS/PS domain.

IMS origination: the case when a UE initiates an IMS session(s) and the CS domain is not involved in the originating part of the session(s).

IMS termination: the case when an IMS session(s) is terminated in the IMS/PS domain and the CS domain is not involved in the terminating part of the session(s).

3.2 Abbreviations

For the purposes of the present document, the following abbreviations apply:

AS Application Server

CSI Combination of CS and IMS services

DTM Dual Transfer Mode

IAM Initial Address Message

CON Connect Message

MRFC Media Resource Function; Control part

MRFP Media Resource Function; Physical Part

MSRP Message Session Relay Protocol

RAT Radio Access Technology

RTP Real-time Transfer Protocol