Digital cellular telecommunications system (Phase 2+) (GSM); Universal Mobile Telecommunications System (UMTS); LTE; IP Multimedia (IM) session handling; IM call model; Stage 2 (V15.0.0; 3GPP TS 23.218 version 15.0.0 Release 15)
The present document specifies the IP Multimedia (IM) Call Model for handling of an IP multimedia session origination and termination for an IP Multimedia subscriber. The present document includes interactions between an Application Server and IP multimedia sessions. The IP Multimedia (IM) Subsystem stage 2 is specified in 3GPP TS 23.228 [3].