A base station for wireless communication with a mobile station using a plurality of cells configured to be grouped so as to comprise a plurality of groups of cells. The base station includes: circuitry configured to transmit a first control signal having a first field and a second field, the first field including information indicating an amount of adjustment for the mobile station to use to adjust a transmission timing of the mobile station with one or more cells, and the second field being configured to store second information identifying the one or more cells among the plurality of groups of cells, and transmit a second control signal having a third field configured to include a unique identifier of one or more of the plurality of cells, according to which the second information set in the second field of the first control signal is applied to the mobile station.