Patent ID: 7853278

Claim:
A PoC (Push-to-talk over Cellular) communication control server for a PoC communication in accordance with SIP (Session Initiation Protocol), the PoC server comprising: receiving means for receiving a single connection request, from a first communication terminal, for establishing a communication channel to be used for the PoC communication, with a second communication terminal which is a member or with a plurality of communication terminals which is a group, including the second communication terminal, the single connection request including information that allows the first communication terminal to establish the communication channel with the communication control server and also including information that allows the second communication terminal or the plurality of communication terminals including the second communication terminal to establish the communication channel or the communication channels with the communication control server; and call processing means for extracting the information from the single connection request and performing call processing for establishing the communication channel between the communication control server and the second communication terminal or the communication channels between the communication control server and the plurality of communication terminals including the second communication terminal, immediately after the single connection request is received by the receiving means; wherein processing including: sending a response to the single connection request; performing a SIP registration process of the first communication terminal; and receiving an INVITE message from the first communication terminal is performed, in parallel with the call processing.