CALL SET-UP IN A RADIO COMMUNICATION SYSTEM

摘要

A method of call set-up on a radio communication system offering trunked-mode communication (7-10) and direct-mode communication (11). The method includes the steps of: requesting on a trunked signalling channel (10), by a first communication unit (6), a conventional traffic channel (11) for communicating with a second communication unit (5); and re-tuning (45) the first communication unit (6) and second communication unit (5) to the conventional traffic channel (11) to enter into a direct-mode call. The packet data protocol supported by the given trunked system is used to set up calls on conventional channels. The packet data signalling protocol then ensures reliable call set up.