Reception-side apparatus and radio communication method

1. A reception-side apparatus comprising:

M receive antennas; and

a processor 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 processor is configured to:

acquire all patterns of a combination acquired by classifying the signals from the N transmission-side apparatuses into the first signal from the first transmission-side apparatus, second signals from M-1 transmission-side apparatuses to be cancelled by the receive diversity processing and third signals 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;

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.

2. The reception-side apparatus according to claim 1 , wherein

if the number N of transmission-side apparatuses is larger than the number M of receive antennas in the first process,

the processor is configured to acquire receive power of a signal from each of the transmission-side apparatuses; and

reduce the number of acquired patterns by acquiring all the patterns of the combination for signals from N′ transmission-side apparatuses left after excluding a predetermined number of transmission-side apparatuses from the N transmission-side apparatuses based on the receive power of the signal from each of the transmission-side apparatuses.

3. The reception-side apparatus according to claim 2 , wherein

the processor is configured to identify the signals transmitted from the N′ transmission-side apparatuses by excluding the predetermined number of lower transmission-side apparatuses the receive power of which is small from the N transmission-side apparatuses.

4. The reception-side apparatus according to claim 2 , wherein

the processor is configured to identify the signals from the N′ transmission-side apparatuses by excluding such transmission-side apparatuses that a value acquired by multiplying the receive power by a constant k (k>1) is smaller than the largest receive power from the N transmission-side apparatuses.

5. The reception-side apparatus according to claim 1 , wherein

the receive diversity processing is minimum mean square error (MMSE) diversity; and

for each of all the patterns, the processor is configured to determine the weight of MMSE using power of the third signals of each pattern as a part of interference power.

6. The reception-side apparatus according to claim 1 , wherein

the processor is further configured to execute:

a second process of generating a signal arriving from the first transmission-side apparatus before the receive diversity processing being performed, based on the first signal or the first data;

a third process of extracting signals left after excluding the generated signal arriving from the first transmission-side apparatus from the received signals; and

sequentially repeating, for the extracted signals, the first to third processes with one of N-1 transmission-side apparatuses left after excluding the first transmission-side apparatus from the N transmission-side apparatuses newly as a first transmission-side apparatus.

7. The reception-side apparatus according to claim 6 , wherein

the processor is configured to permit communication with the reception-side apparatus by a plurality of transmission-side apparatuses without assigning radio resources when a communication request to the reception-side apparatus occurs, determine the N transmission-side apparatuses among the plurality of transmission-side apparatuses based on a received reference signal, and repeat the first to third processes when signals are simultaneously received from the N transmission-side apparatuses.

8. A radio communication method executed by a reception-side apparatus provided with M receive antennas, comprising:

executing 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 reception-side apparatus is configured to:

acquire all patterns of a combination acquired by classifying the signals from the N transmission-side apparatuses into the first signal from the first transmission-side apparatus, second signals from M-1 transmission-side apparatuses to be cancelled by the receive diversity processing and third signals 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;

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.

9. The radio communication method according to claim 8 , wherein

if the number N of transmission-side apparatuses is larger than the number M of receive antennas in the first process, the reception-side apparatus is configured to:

acquire receive power of a signal from each of the transmission-side apparatuses; and

reduce the number of acquired patterns by acquiring all the patterns of the combination for signals from N′ transmission-side apparatuses left after excluding a predetermined number of transmission-side apparatuses from the N transmission-side apparatuses based on the receive power of the signal from each of the transmission-side apparatuses.

10. The radio communication method according to claim 9 , wherein

the reception-side apparatus is configured to identify the signals from the N′ transmission-side apparatuses by excluding the predetermined number of lower transmission-side apparatuses the receive power of which is small from the N transmission-side apparatuses.

11. The radio communication method according to claim 9 , wherein

the reception-side apparatus is configured to identify the signals from the N′ transmission-side apparatuses by excluding such transmission-side apparatuses that a value acquired by multiplying the receive power by a constant k (k>1) is smaller than the largest receive power from the N transmission-side apparatuses.

12. The radio communication method according to claim 8 , wherein

the receive diversity processing is minimum mean square error (MMSE) diversity; and

the reception-side apparatus is configured to determine, for each of all the patterns, the weight of MMSE using power of the third signals of each pattern as a part of interference power.

13. The radio communication method according to claim 8 , further comprising:

executing a second process of generating a signal arriving from the first transmission-side apparatus before the receive diversity processing being performed, based on the first signal or the first data;

executing a third process of extracting signals left after excluding the generated signal arriving from the first transmission-side apparatus from the received signals; and

sequentially repeating, for the extracted signals, the first to third processes with one of N-1 transmission-side apparatuses left after excluding the first transmission-side apparatus from the N transmission-side apparatuses newly as a first transmission-side apparatus.

14. The radio communication method according to claim 13 , wherein the reception-side apparatus is configured to:

permit communication with the reception-side apparatus by a plurality of transmission-side apparatuses without assigning radio resources when a communication request to the reception-side apparatus occurs, determine the N transmission-side apparatuses among the plurality of transmission-side apparatuses based on a received reference signal, and repeat the first to third processes when signals are simultaneously received from the N transmission-side apparatuses.