Patent ID: 8204004

Claim:
A frequency channel assignment system comprising a plurality of radio communications systems which use a common frequency band in a common geographical area, and a controller, the controller comprising: a system characteristics information management function configured to manage system characteristics information showing characteristics of frequency channels in the radio communications systems, the system characteristics information including, for each frequency channel, an allowable amount of interference on the frequency channel; a frequency channel assignment function configured to assign the frequency channels to each of the radio communications systems, based on the system characteristics information and channel status information showing status of the frequency channels, so as to avoid inter-system interference, the channel status information including, for each frequency channel, an interference measurement of the frequency channel; the controller determining, within a range of the common frequency band and based on the system characteristics information and the channel status information: a first occupied use frequency band which includes first frequency channels available only to a first radio communications system, a second occupied use frequency band which includes second frequency channels available only to a second radio communications system, and an overlapping use frequency band which includes third frequency channels available to the first and second radio communications system; and the frequency channel assignment function, when the first occupied use frequency band is lower than the second occupied use frequency band, prioritizes a frequency channel of a low frequency band in the first radio communication system and prioritizes a frequency channel of a high frequency band in the second radio communication system.