A reception-side apparatus comprising: M receive antennas (ANT-B); and a control unit configured to execute a first process of acquiring a first signal received from a first transmission-side apparatus which is one of N transmission-side apparatuses from among signals simultaneously received from the N transmission-side apparatuses by receive diversity processing, and acquiring first data by demodulating and decoding the first signal, wherein in the first process, the control unit is configured to: acquire all patterns of a combination of the first signal, second signals, and third signals by classifying the signals from the N transmission-side apparatuses into the first signal being from the first transmission-side apparatus, the second signals being from M-1 transmission-side apparatuses to be cancelled by the receive diversity processing, and the third signals being from N-M transmission-side apparatuses not to be cancelled by the receive diversity processing if the number N of the transmission-side apparatuses is larger than the number M of the receive antennas (ANT-B); acquire, for each of all the patterns, power of the first signal and power of the second signals based on a weight used for the receive diversity processing for each pattern and acquire power of the third signals from channel estimates; acquire a power ratio of the power of the first signal relative to total power of the second and third signals; and determine such a combination that the power ratio after the receive diversity processing is the largest, as a combination of signals for which the receive diversity processing is to be executed to perform demodulation. M receive antennas (ANT-B); and a control unit configured to execute a first process of acquiring a first signal received from a first transmission-side apparatus which is one of N transmission-side apparatuses from among signals simultaneously received from the N transmission-side apparatuses by receive diversity processing, and acquiring first data by demodulating and decoding the first signal, wherein in the first process, the control unit is configured to: acquire all patterns of a combination of the first signal, second signals, and third signals by classifying the signals from the N transmission-side apparatuses into the first signal being from the first transmission-side apparatus, the second signals being from M-1 transmission-side apparatuses to be cancelled by the receive diversity processing, and the third signals being from N-M transmission-side apparatuses not to be cancelled by the receive diversity processing if the number N of the transmission-side apparatuses is larger than the number M of the receive antennas (ANT-B); acquire, for each of all the patterns, power of the first signal and power of the second signals based on a weight used for the receive diversity processing for each pattern and acquire power of the third signals from channel estimates; acquire a power ratio of the power of the first signal relative to total power of the second and third signals; and determine such a combination that the power ratio after the receive diversity processing is the largest, as a combination of signals for which the receive diversity processing is to be executed to perform demodulation. acquire all patterns of a combination of the first signal, second signals, and third signals by classifying the signals from the N transmission-side apparatuses into the first signal being from the first transmission-side apparatus, the second signals being from M-1 transmission-side apparatuses to be cancelled by the receive diversity processing, and the third signals being from N-M transmission-side apparatuses not to be cancelled by the receive diversity processing if the number N of the transmission-side apparatuses is larger than the number M of the receive antennas (ANT-B); acquire, for each of all the patterns, power of the first signal and power of the second signals based on a weight used for the receive diversity processing for each pattern and acquire power of the third signals from channel estimates; acquire a power ratio of the power of the first signal relative to total power of the second and third signals; and determine such a combination that the power ratio after the receive diversity processing is the largest, as a combination of signals for which the receive diversity processing is to be executed to perform demodulation.