Digital cellular telecommunications system (Phase 2+); Universal Mobile Telecommunications System (UMTS); LTE; Communication Waiting (CW) using IP Multimedia (IM) Core Network (CN) subsystem; Protocol Specification (V12.1.0; 3GPP TS 24.615 version 12.1.0
The present document specifies the stage 3@ Protocol Description of the Communication Waiting (CW) service@ based on stage 1 and stage 2 of the ISDN call waiting supplementary services. It provides the protocol details in the IP Multimedia (IM) Core Network (CN) subsystem based on the Session Initiation Protocol (SIP) and the Session Description Protocol (SDP). The Communication Waiting (CW) service enables a user to be informed@ that very limited resources are available for an incoming communication. The user then has the choice of accepting@ rejecting or ignoring the waiting call (as per basic call procedures). The present document is applicable to User Equipment (UE) and Application Servers (AS) which are intended to support the CW supplementary service.