A base station includes a receiver configured to receive data wirelessly transmitted from plural mobile stations which repeatedly transmit the data until a reception acknowledgement signal representing that the data has been received by the base station is received, a transmitter configured to wirelessly transmit data to the plural mobile stations, and a controller configured to assign a radio resource for data transmission to a mobile station of the plural mobile stations in accordance with a data transmission request received from the mobile station, make the receiver receive data from the mobile station in the assigned radio resource, when the receiver has received the data from the mobile station make the transmitter transmit the reception acknowledgement signal to the mobile station, and when the radio resource is reassigned in association with the wireless transmission of the reception acknowledgement signal make the transmitter retransmit the reception acknowledgement signal.