Call set-up in a radio communication system with dynamic channel allocation

In a radio communication system having a number of base stations, each communicating with a plurality of subscriber terminals over separate traffic channels and each base station having access to each of said plurality of traffic channels, a method of selecting a traffic channel for completing call set-up of incoming and outgoing calls between a base station, a subscriber terminal and the Public Switched Telephone Network (PSTN), comprising the steps of:

• receiving, at said base station, an incoming call attempt from a subscriber or from the PSTN;
• scanning, at said base station, said plurality of traffic channels for the presence of radio power levels above a first specified threshold;
• measuring the power level of a scanned traffic channel;
• selecting from the scanned traffic channels, traffic channels with radio power levels below said first specified threshold;
• storing a list of selected traffic channels;
• sending to the subscriber terminal, along a signalling channel linking the base station and the subscriber terminal, the list of selected traffic channels;
• receiving the list at the subscriber terminal;
• scanning the traffic channels on the list;
• measuring the power level on each scanned traffic channel on said list;
• selecting from the scanned traffic channels of the list, traffic channels with radio power levels below a second specified threshold;
• storing the traffic channel selection at said subscriber terminal;
• sending, to the base station, along the signalling channel, the subscriber terminal's traffic channel selection, which provides an indication of the subscriber terminal's preferred traffic channel and redundant traffic channel to be selected if the preferred traffic channel becomes unusable;
• receiving the traffic channel selection at said base station;
• switching the base station and the subscriber terminal to the preferred traffic channel;
• and
• proceeding with call connection.