System and method for establishing first-to-answer call in mission critical push to talk communication

A mission critical push to talk (MCPTT) server comprising:

• a communication unit;
• and
• a controller coupled with the communication unit and configured to:
• receive, from an MCPTT originating client, a first MCPTT first-to-answer call request message,
• identify at least one MCPTT user to transmit a second MCPTT first-to-answer call request message based on the first MCPTT first-to-answer call request message,
• transmit, to at least one MCPTT recipient client of the at least one MCPTT user, the second MCPTT first-to-answer call request message,
• receive, from a first MCPTT recipient client among the at least one MCPTT recipient client, a first MCPTT first-to-answer call response message, and
• transmit, to a second MCPTT recipient client among the at least one MCPTT recipient client, an MCPTT first-to-answer call cancel request message.

A method performed by a terminal for a mission critical push to talk (MCPTT) service in a communication system, the method comprising:

• receiving, from an MCPTT server, an MCPTT first-to-answer call request message of an MCPTT originating client;
• transmitting, to the MCPTT server, an MCPTT first-to-answer call response message in response to the MCPTT first-to-answer call request message;
• and
• receiving, from the MCPTT server, an MCPTT first-to-answer call cancel request message.

A terminal for a mission critical push to talk (MCPTT) service in a communication system, the terminal comprising:

• a transceiver;
• and
• a controller coupled with the transceiver and configured to:
• receive, from an MCPTT server, an MCPTT first-to-answer call request message of an MCPTT originating client,
• transmit, to the MCPTT server, an MCPTT first-to-answer call response message in response to the MCPTT first-to-answer call request message, and
• receive, from the MCPTT server, an MCPTT first-to-answer call cancel request message.