Patent ID: 8014811

Claim:
A communication system, comprising: a transmission device; and a reception device, the transmission device comprising: modulation means for modulating transmission data by using any of a plurality of modulation schemes to generate a transmission signal; transmission means for sending the transmission signal generated by the modulation means; and transmission power decreasing means for decreasing transmission power used when the transmission means sends the transmission signal by a predetermined change amount, in a case where a communication rate is increased by changing the modulation scheme used by the modulation means; the reception device comprising reception means for receiving the transmission signal sent by the transmission means, wherein the communication system further comprises: received power information acquisition means for obtaining received power information indicating received power obtained when the transmission signal is received by the reception means; communication rate modification means for changing, in a predetermined case, the communication rate by changing the modulation scheme used by the modulation means; and communication rate increase limit means for limiting the communication rate to be increased by the communication rate modification means, according to received power required for the reception device to demodulate the transmission signal received by the reception means and according to the received power obtained when the reception means receives the transmission signal after the communication rate is changed by the communication rate modification means and predicted based on the received power information obtained by the received power information acquisition means and based on the change amount of the transmission power by the transmission power decreasing means.