원래 이름 기록: SoftBank Corp.

It is provided of a communication system capable of suppressing a fluctuation in a reception power of a known signal from a base station due to an attitude change of a radio relay apparatus, and performing an appropriate gain control of a power amplifier of the radio relay apparatus based on the reception power of the known signal, in case that the base station uses a plurality of linear polarization antennas for wireless communication with the radio relay apparatus. The base station comprises an antenna apparatus that has a plurality of linear polarization antennas capable of transmitting and receiving radio waves with different angles of linear polarization planes from each other when performing a feeder-link communication with the radio relay apparatus, and a base-station processing section or an externally-attached phase control apparatus for controlling a phase difference between plural transmission signals supplied to the plurality of the linear polarization antennas, so that a combined polarization of radio waves of the known signal transmitted from the antenna apparatus to the radio relay apparatus becomes a circular polarization or an elliptical polarization, with respect to a predetermined time slot for transmitting to the radio relay apparatus a specific known signal usable for gain control of a power amplifier of the radio relay apparatus.