A REC device of a base station includes a switch instructing unit and an extension signal processor. The switch instructing unit monitors the state of the REC device, and based on a result of the monitoring, determines switching from the REC device to an extension REC device. When the switching is determined, the extension signal processor acquires a signal transmitted from the extension REC device, and requests the switching from the extension REC device. The extension REC device includes an extension signal processor and a digital processor. The extension signal processor receives the switch request from the extension signal processor of the REC device. In response to the received switch request, the digital processor sets the parameters of the REC device in the extension REC device, and establishes a link to a RE.