5.1.11 Charging support for IMS service continuity

32.2603GPPCharging managementIP Multimedia Subsystem (IMS) chargingRelease 17Telecommunication managementTS

The charging requirements for IMS service continuity using AS and ATCF are specified in TS 23.237 [216].

Inter-UE transfer provides the capability of transferring the communication sessions with multiple media across different UEs and is part of Service Continuity (SC) as described in TS 23.237 [216]. For inter-UE transfer shall an AS implement the role of an SCC AS according to TS 24.337 [218]. 

A complete session can be transferred from one UE to another with or without establishing a collaborative session as defined in TS 23.237 [216] and TS 24.337 [218]. The SCC AS is able to serve an inter-UE transfer request initiated by the target UE without the establishment of a collaborative session regardless of the access technology used by either of the involved UEs.

For a consistent representation of the various access transfers specified in TS 23.237 [216] and TS 24.337 [218] in offline and online charging of the AS and in offline charging of the ATCF the Access Transfer Type parameter provides information on the used access technologies, e.g. PS to CS, CS to PS, PS to PS or CS to CS. The Inter-UE Transfer parameter indicates whether the access transfer was done between two UEs provided by the SCC AS as defined in TS 24.337 [218]. These parameters together, show the type of access transfer in detail, and are reported together with UE identification (i.e. Subscriber Equipment Number and/or Instance Id), Access Network Information and potentially Additional Access Network Information and Cellular Network Information available along the session transfer procedure.

Subsequently, the Requested Party Address parameter holds addresses related to session transfer if available: For SIP transactions, the address of the party (Public User ID or Public Service ID) to whom the SIP transaction was originally posted. For PS to CS transfer, the Session Transfer Number for Single Radio Voice Call Continuity (STN-SR) as described in TS 23.237 [216]. For CS to PS transfer, the Session Transfer Identifier for CS to PS Single Radio Voice Call Continuity (STI-SR) as described in TS 23.237 [216].