Abstract: In a cellular mobile radio system a method of choosing at a mobile station an appropriate base station and time slot on a time division multiplexed radio channel for the purpose of call set up or handover, wherein each base station transmits in one time slot of a predetermined control radio channel and, at least once during a multiframe, in each communication radio channel time slot used by the base station for calls, roaming signals comprising information on identity of transmitting base station and communication radio channels available at transmitting base station, the mobile scanning the control and communication channels and when desirous of call set up or handover selecting a base station and a time slot on a communication channel, the mobile desirous of call set up or handover transmitting to the choosen base information on mobile identity and the choosen communication channel time slot.