Wireless communication unit, wireless communication system and method of communication

A wireless subscriber communication unit (300) is capable of communication on a direct mode communication system (200) employing a timing structure (100) that does not support private full-duplex communication. The wireless subscriber communication unit (300) comprises a signal-processing unit (308) having a private full-duplex call function (340) configured to recognise a request for a private full-duplex communication and, in response to such a recognition, modify the unit's use of the timing structure (400) to perform private full-duplex communication.