Method and apparatus for performing direct communication with at least one other user equipment

A mission critical push to talk (MCPTT) client device, comprising:

• a transceiver;
• and
• a controller configured to:
• transmit, via the transceiver, to at least one client device, a floor request message requesting permission to send media for an off-network group call,
• start a timer upon transmitting the floor request message,
• restart the timer in response the timer expiring before receiving a floor granted message in response to the floor request message,
• stop the timer in response to receiving the floor granted message before the timer expires,
• retransmit the floor request message each time the timer expires before receiving the floor granted message until a total number of transmissions of the floor request message reaches a predetermined number of times,
• transmit, via the transceiver, to the at least one client device, a floor taken message indicating that the permission to send is granted to the MCPTT client device after transmitting the floor request message the predetermined maximum number of times and the timer expires before receiving the floor granted message, and
• transmit, via the transceiver, first media data to the at least one client device after transmitting the floor taken message.

A method performed by a mission critical push to talk (MCPTT) client device, the method comprising:

• repeatedly receiving, from a first client device, a floor request message requesting permission to send media for an off-network group call, while the MCPTT client device does not transmit, to the first client device, a floor granted message in response to the floor request message,
• wherein the floor request message is transmitted from the first client device each time a timer expires at the first client device before the floor granted message is received by the first client device, until a total number of transmissions of the floor request message reaches a predetermined number of times,
• wherein the timer restarts in response to the timer expiring before the floor granted message is received by the first client device, and
• wherein the timer stops in response to the floor granted message being received by the first client device before the timer expires;
• receiving, from the first client device, a floor taken message indicating that the permission to send is granted to the first client device, wherein the floor taken message is transmitted from the first client device in case that the floor request message is repeatedly transmitted the predetermined number of times and the timer expires before receiving the floor granted message;
• identifying that the permission to send is granted to the first client device based on receiving the floor taken message;
• entering a no-permission state;
• and
• receiving, in the no-permission state, first media data from the first client device.

A mission critical push to talk (MCPTT) client device, comprising:

• a transceiver;
• and
• a controller configured to:
• repeatedly receive, via the transceiver, from a first client device, a floor request message requesting permission to send media for an off-network group call, while the MCPTT client device does not transmit, via the transceiver, to the first client device, a floor granted message in response to the floor request message,
• wherein the floor request message is transmitted from the first client device each time a timer expires at the first client device before the floor granted message is received by the first client device, until a total number of transmissions of the floor request message reaches a predetermined number of times,
• wherein the timer restarts in response to the timer expiring before the floor granted message is received by the first client device, and
• wherein the timer stops in response to the floor granted message being received by the first client device before the timer expires,
• receive, via the transceiver, from the first client device, a floor taken message indicating that the permission to send is granted to the first client device, wherein the floor taken message is transmitted from the first client device in case that the floor request message is repeatedly transmitted the predetermined number of times and the timer expires before receiving the floor granted message,
• identify that the permission to send, is granted to the first client device based on receiving the floor taken message,
• enter a no-permission state, and
• receive, via the transceiver, in the no-permission state, first media data from the first client device.