A communication system includes sector units composing base stations, and mobile subscriber stations each being in sectors corresponding to the sector units. The mobile subscriber stations transmit channel estimation signals to the sector units corresponding to the sector and sector units corresponding to sectors contiguous to the sectors. A sector unit that corresponds to the sector forms, based on a channel estimation signal received from the mobile subscriber station in the sector corresponding to the sector unit and channel estimation signals received from the adjacent mobile subscriber stations in the sectors contiguous to the sector, a transmission beam that is directed to the mobile subscriber station but is not directed to the adjacent mobile subscriber stations to transmit data to the mobile subscriber station. By configuring the system in such a manner, interference from contiguous sectors can be avoided.