a radio communication system includes a plurality of base stations and a plurality of mobile stations belonging to the service areas covered by the radio zones respectively formed by the base stations and performs data communication by polling . each base station includes a transmission output control section for controlling the transmission output of a polling signal to sequentially form a plurality of radio zones having different coverages , a section for receiving responses from the plurality of mobile stations to a plurality of polling signals having different transmission outputs and determining the position of each of the mobile stations in a specific one of the plurality of radio zones .