For the purposes of the present document, the terms and definitions given in
TR 21.905 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.
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).
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