In one aspect of the present invention, a base station includes a reception unit configured to receive a call request or a paging response according to circuit switching from a mobile station; a packet switched communication state determination unit configured to determine a state of packet switched communication of the mobile station, when the call request or the paging response is received from the mobile station; and a circuit switching communication processing unit configured to establish a circuit switched bearer using a radio parameter for circuit switched communication, when no packet switched communication is performed in the mobile station.