Base station, mobile terminal, and communications method

A method of performing communications according to Time Division Duplex, to which method Orthogonal Frequency Division Multiplexing/Orthogonal Frequency Division Multiple Access is applied, wherein a transmission frame in Time Division Duplex includes a downlink subframe and an uplink subframe, the method comprising:

• (a) a base station transmitting the downlink subframe through a first one of first antennas thereof;
• (b) a mobile terminal receiving the downlink subframe through a first one of second antennas thereof;
• (c) the mobile terminal transmitting an initial ranging code through a second one of the second antennas thereof;
• (d) the base station receiving the initial ranging code transmitted by the mobile terminal through a second one of the first antennas thereof during the transmission of the downlink subframe;
• and
• (e) the base station performing ranging based on the initial ranging code received in said step (d).