A MOBILE STATION FOR A PLURALITY OF COMMUNICATION CARRIERS

The present invention is a mobile communication system having a mobile station UE, in which CA is performed, configured to transmit an uplink data signal to a radio base station eNB, by using a plurality of "Component Carriers" having different carrier frequencies, and the mobile communication system includes TA timer management units 13 and 23 configured to manage the TA timer corresponding to the plurality of "Component Carriers"; and state management units 14 and 24 configured to manage the state of the plurality of "Component Carriers", and the state management units 14 and 24 are configured to set the state of a "Component Carrier", whose TA timer has expired, to an asynchronous state.