Patent ID: 8180387

Claim:
A system for establishing a Push to Talk Over Cellular (PoC) group session in a PoC system, comprising: a PoC extensible markup language Document Management Server (XDMS); and a PoC server, wherein the PoC XDMS receives Invitation Reservation Service (IRS)-related information from a PoC terminal, the IRS-related information defining a session initialization condition, the PoC XDMS transmits an IRS IDentification (ID) for identifying the IRS-related information to the PoC terminal, and the PoC server performs session initialization by using the IRS ID when an IRS request message is received from the PoC terminal, and wherein the IRS-related information comprises a presence information type for session initialization of an invited PoC client, a session request triggering condition, and an expiration time of IRS request.