Mobile communication system, radio base station, and mobile station

A mobile communication system having a mobile station configured to transmit an uplink signal to a radio base station by using a plurality of carriers having different carrier frequencies, comprising:

• a timer management circuitry configured to manage a Timing Advance (TA) timer corresponding to the plurality of carriers;
• and
• a state management circuitry configured to manage a state of each of the plurality of carriers, wherein
• the state management circuitry is configured to set the state of each of the plurality of carriers, whose TA timer has expired, to an asynchronous state, and
• the mobile station is configured to transmit a Random Access Channel (RACH) Preamble in the carrier, when the carrier specified by a Carrier Indicator Field (CIF), the CIF being transmitted via a Physical Downlink Control Channel (PDCCH) from the radio base station, is in an asynchronous state,
• wherein the mobile communication system is configured for the plurality of carriers having different carrier frequencies from the radio base station.