Patent ID: 8213952

Claim:
A communication system comprising: a main communication unit; a subcommunication unit configured to perform wireless communications with the main communication unit by using a plurality of first wireless channels, each of the plurality of first wireless channels indicating a respective band of a plurality of bands into which a predetermined frequency band is divided; and an external communication unit configured to perform wireless communications with the main communication unit by using a plurality of second wireless channels, each of the plurality of second wireless channels including a plurality of continuous first wireless channels in the predetermined frequency band, wherein the subcommunication unit comprises: a state detection unit configured to detect an electric field strength of a part or all of the plurality of second wireless channels, and wherein the main communication unit comprises: a memory; a central processing unit configured to operate as: a state acquisition unit connected to the state detection unit, via the wireless communications using the plurality of first wireless channels, and connected to the memory, wherein the state acquisition unit is configured to acquire the electric field strength of the part or all of the plurality of second wireless channels detected by the state detection unit and to store the electric field strength of the part or all of the plurality of second wireless channels in the memory; and a selection unit connected to the memory, wherein the selection unit is configured to select a predetermined number of the first wireless channels that generate reduced radio interference during the wireless communications performed between the main communication unit and the subcommunication unit from the plurality of first wireless channels based on the electric field strength of a part or all of the plurality of second wireless channels acquired and stored in the memory by the state acquisition unit and to store the selected predetermined number of the first wireless channels in the memory; and a digital cordless communication control unit configured to operate as: a channel determination unit connected to the memory, wherein the channel determination unit is configured to determine one of the predetermined number of the first wireless channels selected and stored in the memory by the selection unit every first period; and a first wireless communication unit configured to perform wireless communications with the subcommunication unit using the one of the predetermined number of the first wireless channels determined by the channel determination unit.