Abstract: Time required before PoC communication starts, in the case where a communication channel on the destination side has not been established, is shortened, and convenience of users is enhanced. A request for establishing a communication channel used for PoC communication is sent from a terminal TA. Immediately after receiving this request, call processing for establishing a communication channel to a terminal TC other than the terminal TA is started. In parallel with this call processing, processing after sending a response to the request is performed. Thereby, response to a communication channel connection request, SIP Registration processing and Invitation processing on the originating side and the processing on the destination side are performed in parallel, so that connection time can be shortened, and PoC communication can be started early.

Abstract: Subject to user's setting in PoC group communication, the user address of that user is set to non notification against other users. In case of starting PoC group communication, a PoC subscriber selects non notification subjects and transmits a PoC session commencement request. At that time, the caller sets his own address and/or address/addresses of all or a part of users to non notification. On a user designated as a non notification subject due to the caller's setting, PoC terminal apparatuses in receipt of a PoC session commencement request or PoC communication service controlling apparatuses undergo non notification setting processing. On a called party not selected as non notification subject users, if he/she sets his/her own user address to non notification in advance, likewise non notification processing is implemented. Even after a PoC session is established, each user can set his/her own user address to non notification and non notification service complying with user's intention is providable.