1. A method for determining a back-up frequency in a cognitive radio system comprising a first cognitive system, a second
cognitive system and an incumbent system, wherein the method comprises:
the first cognitive system obtaining, through a terminal, a back-up frequency, of the second cognitive system having overlap
coverage in a target area, in an overlap coverage area; and
the first cognitive system selecting at least one frequency from radio communication spectrum resources as a back-up frequency
in the target area according to the back-up frequency of the second cognitive system in the overlap coverage area.