To establish radio channels according to a DAMA scheme, FDM radio channels are divided into channel groups, each containing a predetermined number of neighboring channels. The base station includes group modems for FDM modem processing, on a basis of each channel group, into uplink baseband signals uplink radio signals received from source stations in uplink channel groups and downlink baseband signals into downlink radio signals sent to destination stations in downlink channel groups and a switching unit for switching the baseband signals from the uplink channel groups into the downlink channel groups according to the destination stations. Each terminal station includes a group modem for FDM modem processing en-bloc downlink channel group radio signals into downlink terminal baseband signals and uplink terminal baseband signals into uplink channel group radio signals and baseband processors for processing the downlink terminal baseband signals for supply to the communication terminals according to the neighboring channels of the downlink channel group and uplink baseband signals of the communication terminals into the uplink terminal baseband signals according to the neighboring channels of the uplink channel group.