Radio resources are saved. The base station 101 determines a possibility of transmitting data to the terminal 102, and transmits the indicator indicating the possibility of transmitting the data to the terminal 102. The terminal 102 generates a mode request message for determining a coding rate and a modulation system at the base station 101, and sets a transmission frequency of the mode request message based on the indicator transmitted from the base station 101. Accordingly, the mode request message is transmitted from the terminal 102 to the base station 101 at the determined transmission frequency.