When a mobile device performs a handover from a first wireless base station to a second wireless base station, a base station controller sends a control message addressed to the second base station to notify the handover, to the first wireless base station via a wired line. The first wireless base station sends received control message to the second wireless base station using a pre-established wireless line. The wireless base stations exchange a control message to control the second wireless base station, a control message to control the mobile device, and user data of the mobile device and a communication partner, using the wireless line.