Question: In an MCPTT (Mission Critical Push To Talk) scenario, when a Floor Request message is received from a participant in a broadcast group call who is **not** the initiator, how does the IWF (Interworking Function) floor control server respond?
Option 1: Forward the Floor Request to the floor control server arbitration logic for evaluation.
Option 2: Send a Floor Grant message to upgrade the call to an emergency call if the participant has emergency privileges.
Option 3: Initiate a new SIP session to potentially upgrade the group call to a different type (e.g., from broadcast to emergency).
Option 4: Send a Floor Deny message with a Reject Cause value of #5 (Receive only) and optionally include a Reject Phrase.
Explanation: According to MCPTT media plane control interworking specifications, if the session is a broadcast group call and the associated floor participant is not the initiator, the IWF floor control server shall send a Floor Deny message. This message must include a specific Reject Cause value (#5, indicating 'Receive only') to inform the participant that they cannot take the floor in this context, thereby maintaining the integrity of the broadcast group call initiated by another party.