To register current codec types of a mobile station with a network side, the mobile station 11 notifies, when it conducts the location registration or a mobile user replaces his or her old mobile station, a visitor location switching system 5, which is associated with the current location of the mobile station, of the codec types supported by the mobile station 11 using a mobile communication control signal between the mobile station and the mobile network. Receiving the notification, the visitor location switching system 5 enters the update of the codec types into a location register 41 in a memory home station that controls the mobile network 2. The codec types can be thus registered into the mobile network 2 using the mobile communication control signal. Since the mobile network 2 can always acquire the latest codec types for the mobile station, the discrepancy is canceled between the codecs the mobile station supports and the codecs the network registers.