Conventionally, if the number of transmission antennas is greater than that of reception antennas, different signals simultaneously transmitted from the transmission antennas cannot be separated from one another at the receiving end, resulting in a significant degradation of received-signal quality. A transmitter and a receiver each have a plurality of antennas. The transmitter transmits a pilot signal. The receiver receives the pilot signal to calculate transmission-related information corresponding to the pilot signal, and then selects, based on this calculated information, a signal to be sent to and utilized by the transmitter. The receiver then informs the selected signal to the transmitter. The transmitter selects, from the informed signal, transmission antennas and uses them to transmit information signals, so that a signal separation can be easily performed at the receiving end.