An examining unit examines the radio wave environments on at least one of a plurality of frequency channels usable in communications. Based on a result of examination by the examining unit, a selector selects a frequency channel to be used for communications. While using the channel selected by the selector, an execution unit transmits signals from a plurality of antennas to a terminal apparatus and performs calibration on the plurality of antennas by receiving signals from the terminal apparatus via the plurality of antennas.