Communication system and a base station

PROBLEM TO BE SOLVED: To avoid depletion of C-RNTI numbers that should be paid out to terminals at the time of execution of CA.SOLUTION: A communication system includes a base station and a terminal. The base station comprises a first payout unit and a second payout unit. In the case where first communication using any one cell of all the cells of the base station is performed between the terminal and the base station, the first payout unit pays out a first identification number which is an identification number specific to each of all the cells from a prescribed number of identification numbers to identify terminals to the terminal. In the case where second communication simultaneously using two or more cells of all the cells is performed between the terminal and the base station, the second payout unit pays out a second identification number which is an identification number common to two or more cells from the prescribed number of identification numbers excluding the first identification numbers to the terminal. The terminal comprises a communication control unit. The communication control unit performs the first communication or the second communication using the first identification number or the second identification number paid out by the base station.