Ststem, mobile apparatus and method for providing the information of a multimedia poc session clinent in poc system

A multimedia PoC(PTT over Cellular) session participant information service method in a PoC system, a terminal device, and a system are provided to enable a conference server to automatically notify of supportable media types of clients participating in a session, thereby reducing an excessive signaling burden between the server and the PoC clients. A transmission PoC client(630) transmits a session invite message for requesting at least more than one receiving PoC client to participate in a session to a PoC server(650). The PoC server delivers the invite message to the receiving PoC clients, and establishes a multimedia PoC session between the PoC server and the transmission PoC client as a response message is first received from one of the receiving PoC clients(600). The PoC server transmits a message which contains session participation information included in a response message received after the first response message to the PoC clients participating in the session(602-606).