Abstract: An original data signal is transmitted by a predetermined transmission power, the data signal distorted during transmission is received, and the received signal is output after being restored to the original data signal, the SNR for each subchannel is calculated and a higher power is allocated to a subchannel having a higher SNR and a lower power is allocated to a subchannel having a lower SNR. If the transmission power of each subchannel exceeds a maximum limit, the maximum limit is redetermined as the transmission power of the subchannels whose transmission power exceeds the maximum limit. Then, the transmission power of a subchannel whose SNR is negative is determined if the transmission power of each subchannel does not exceed the maximum limit or the above redetermination step is completed. Thereafter, the transmission power of each subchannel is controlled to the determined power.