Push-to-talk telecommunications system utilizing an voice-over-ip network

A non-transitory, computer accessible memory medium storing program instructions for establishing an ad-hoc push-to-talk (PTT) call between users in a wireless communications network, wherein the program instructions are executable to cause a processor to:

• receive a first SIP INVITE request from a mobile communication device, the first SIP INVITE request comprising one or more addresses of one or more parties invited to participate in the PTT call, wherein the one or more addresses comprise a first address of a first party;
• forward the first SIP INVITE request to a distribution server;
• receive a second SIP INVITE request from the distribution server, wherein the second SIP INVITE request is responsive to the first SIP INVITE request, and wherein the second SIP INVITE request is addressed to the first party;
• forward the second SIP INVITE request to the first party;
• receive a first response message from the first party, wherein the first response message is responsive to the second SIP INVITE request;
• in response to the receiving the first response message, exchange messages with the distribution server and the mobile communication device to indicate to the mobile communication device that that at least one of the one or more parties invited to participate in the PTT call has accepted the invitation.

An apparatus for establishing an ad-hoc push-to-talk (PTT) call between users in a wireless communications network, the apparatus comprising:

• a network interface and a processor;
• wherein the network interface and the processor are configured to:
• receive a first SIP INVITE request from a mobile communication device, the first SIP INVITE request comprising one or more addresses of one or more parties invited to participate in the PTT call, wherein the one or more addresses comprise a first address of a first party;
• in response to the receiving the first SIP INVITE request, exchange invitation messages with the server and the first party, wherein at least one of the messages comprises an invitation to the first party to participate in the PTT call;
• receive a first response message from the first party, wherein the first response message is responsive to the invitation to the first party;
• in response to the receiving the first response message, exchange additional response messages with the server and the mobile communication device to indicate to the mobile communication device that that at least one of the one or more parties invited to participate in the PTT call has accepted the invitation.