Call set-up and spectrum sharing in radio communication on systems with dynamic channel allocation

In a radio communication system operating within a specified radio spectrum and having a number of base stations, each communicating with a plurality of subscriber terminals over separate radio channels and each base station having access to each of said plurality of radio channels, a method of selecting a radio 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), said base stations being located in geographical regions wherein varying portions of the radio spectrum in each of said geographical regions are reserved for fixed radio transmission services, the method comprising the steps of:

• identifying the range of frequencies which is reserved for said fixed radio transmission services in a said base station's geographical region;
• selecting for allocation, from a plurality of radio channels covering the radio spectrum, those radio channels that lie outside of the reserved range of frequencies for said base station`s geographical region;
• registering, at each of said base stations, signalling and radio traffic channels that can be allocated;
• receiving at a said base station, an incoming call attempt from a subscriber or from the PSTN;
• scanning, at the said base station, said radio traffic channels that can be allocated at the said base station 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 terminals, the list stored at said base station;
• receiving the list of selected channels at the subscriber terminal;
• scanning at the subscriber terminal the traffic channels on said list for the presence of radio power levels above a second specified threshold;
• measuring at the subscriber terminal the power level on a scanned traffic channel on said list;
• selecting at the subscriber terminal from the scanned traffic channels of the list, traffic channels with radio power levels below said second specified threshold;
• storing the selected traffic channels at said subscriber terminal;
• sending, to the said base station, along the signalling channel, a traffic channel selection comprised of a first preferred traffic channel and a second redundant traffic channel;
• receiving the traffic channel selection at the said base station;
• switching the said base station and the subscriber terminal to the preferred traffic channel;
• and
• proceeding with call connection.