A study on session setup for group communications in push-to-talk over cellular using rich presence

The IMS-based, half-duplex push-to-talk over cellular (PoC) service provides a cost-efficient, interactive, and global-reach service for group and individual communications. The media types for PoC users can be voice, video, images, and text messages. Presence service is widely used and is often bundled with PoC and instant messaging (IM) to indicate other users´ availability and willingness of communications. In this paper, we investigate the session setup procedure for the PoC group communications within OMA PoC infrastructure and propose a method to optimize the initiation of a PoC prearranged group session using rich presence information. With this method, the SIP signaling traffic and session delay are significantly reduced.