An SINR estimating unit of a receiver apparatus measures first and second demodulated signals to calculate SINR (ratio of signal power to sum of interference power and noise power) for each signal sequence. A transmission parameter deciding unit decides, based on the SINR, a transmission parameter used by a transmitter apparatus for controlling the transmission for each signal sequence, and then feeds the decided transmission parameter back to the transmitter apparatus. First and second mapping units of the transmitter apparatus controls, based on the transmission parameters as fed back, the modulation level for each signal sequence.