A base station, to which Orthogonal Frequency Division Multiplexing/Orthogonal Frequency Division Multiple Access is applied, communicates with a mobile terminal according to Time Division Duplex, in which a transmission frame includes a downlink subframe and an uplink subframe. The base station includes multiple antennas; a radio communications part configured to transmit the downlink subframe through a first one of the antennas and to receive an initial ranging code transmitted by the mobile terminal through a second one of the antennas during the transmission of the downlink subframe; and a ranging processing part configured to perform ranging based on the initial ranging code received by the radio communications part.