Push to Talk Over Cellular (PoC)

Push to talk over Cellular is a two-way form of communication that allows users to engage in immediate communication with one or more users. The POC service is similar to a "walkie-talkie" service in the way that by pressing a button, a talk session with an individual user or a broadcast to a group of participants is initiated. Receiving participants hear the senders voice either without any action on their part (auto-answer mode), or may be notified and have to accept the call before listening to the senders voice. In addition, the PoC service supports two-modes of PoC session establishment: the Pre-established session mode and the on-demand session mode. The communication is half duplex meaning that only one person can talk at a time and all other participants here the speech. The permission for talk right granting is controlled via a floor control mechanism. The PoC service typically supports:

• PoC session, which is the basic capability to set up voice communications between two users.
• 1-to-many PoC sessions, which is the capability to enable voice communication among many PoC participants/subscribers in an ad-hoc or pre-defined group manner.
• Instant Personal Alerts, which is the capability to inform about the calling user's wish to communicate and to request the invited user to call-back.

The OMA PoC Working Group is working on technical specifications for interoperable PoC products. The current OMA PoCv1.0 Release specifications are using ▲SIP for session management and ▲RTP/▲RTCP for voice packet transport.