Information processing apparatus, transmission-side apparatus and method

1. An information processing apparatus comprising a controller configured to, when signals are simultaneously received from K transmission-side apparatuses (K: a positive integer) by a receiving antenna, and repetition of repeatedly and successively transmitting the same signal N times (N: a positive integer) is performed by the K transmission-side apparatuses:

divide the K transmission-side apparatuses into G groups (G: a positive integer; 1<G≤K);

in order to obtain a transmitted reference signal x(k,n) transmitted from a transmission-side apparatus k (k=1, . . . , K) included among the K transmission-side apparatuses by the n-th (n=1, . . . , N) reference signal transmission in the repetition, acquire a phase rotation amount φ(g,n) that is a phase rotation amount given to a transmitted reference signal x(k) and that is assigned to a group g (g=1, . . . , G) to which the transmission-side apparatus k belongs so that received reference signals from transmission-side apparatuses not belonging to the group g are cancelled when giving a phase rotation amount opposite to the phase rotation amount φ(g,n) to a received reference signal r(n) that is received by the receiving antenna by the n-th reference signal transmission in the repetition and that includes a transmitted reference signal from each of the K transmission-side apparatuses and adding the first to N-th received reference signals in the repetition, and

transmit a phase sequence Φg={φ(g,1), . . . , Φ(g,N)} that includes the phase rotation amount φ(g,n) for the group g for each of the first to N-th transmissions, to the transmission-side apparatus k.

2. The information processing apparatus according to claim 1 , wherein the controller acquires the phase rotation amount φ(g,n) such that a phase sequence Φg1 and a phase sequence Φg2 are orthogonal to each other in all of combinations of two groups g1 and g2 (g1=1, . . . , G; g2=1, . . . , G; g1≠g2) among the G groups.

3. The information processing apparatus according to claim 1 , wherein the controller generates the G groups based on ascending order of propagation losses from the K transmission-side apparatuses, descending order of received signal powers or ascending order of signal-to-noise ratios.

4. The information processing apparatus according to claim 1 , wherein the controller

newly acquires the phase rotation amount φ(g,n) when detecting change in the number of the transmission-side apparatuses configured to simultaneously receive signals, change in members of the K transmission-side apparatuses or change in order of magnitudes of received signal powers from the K transmission-side apparatuses, and

transmits a phase sequence Φg that includes the newly acquired phase rotation amount φ(g,n) for the group g for each of the first to N-th transmissions, to the transmission-side apparatus k (k=1, . . . , K).

5. The information processing apparatus according to claim 1 , wherein

the controller

acquires, by giving the phase rotation amount opposite to the phase rotation amount φ(g,n) for the group g (g=1, . . . , G) to the received reference signal r(n) and adding the first to N-th received reference signals in the repetition to cancel received reference signals from transmission-side apparatuses not belonging to the group g, a received reference signal r(g) (g=1, . . . , G) of the group g that includes received reference signals from one or more transmission-side apparatuses belonging to the group g; and

performs communication channel estimation based on the received reference signal r(g) (g=1, . . . , G).

6. The information processing apparatus according to claim 5 , wherein

the controller

acquires a data signal d by adding data signals d(n) corresponding to the N times in the repetition, each of the data signals d(n) transmitted from the K transmission-side apparatuses by the n-th data signal transmission in the repetition, received by the receiving antenna, and including a data signal d(k,n) from the transmission-side apparatus k (k=1, . . . , K); and

separates a data signal d(k) received from the transmission-side apparatus k, from the data signal d using a result of the communication channel estimation.

7. The information processing apparatus according to claim 5 , wherein the controller simultaneously receives signals from the K transmission-side apparatuses by M receiving antennas (M: a positive integer), and, when each of the K transmission-side apparatuses performs the repetition, executes the communication channel estimation for each receiving antenna.

8. A transmission-side apparatus comprising:

at least one transmitting antenna; and

a controller configured to, when the transmission-side apparatus transmits a signal simultaneously with other K-1 transmission-side apparatuses (K: a positive integer), and each of the transmission-side apparatus and the other K-1 transmission-side apparatuses performs repetition of repeatedly and successively transmitting the same signal N times (N: a positive integer):

receive a phase sequence Φg={φ(g,1), . . . , φ(g,N)} that includes a phase rotation amount φ(g,n) given to a transmitted reference signal x(s) (s indicates the apparatus itself) from a reception-side apparatus, the phase sequence Φg={φ(g,1), . . . , φ(g,N)} being assigned to a group g (g: an integer from 1 to G) to which the transmission-side apparatus itself belongs, among G groups into which K transmission-side apparatuses including the other K-1 transmission-side apparatuses and the apparatus itself are divided, in the n-th (n=1, . . . , N) reference signal transmission in the repetition;

acquire a transmitted reference signal x(s,n) by giving a phase rotation amount φ(g,n) to the transmitted reference signal x(s) in the n-th reference signal transmission in the repetition; and

transmit the transmitted reference signal x(s,n) from the at least one transmitting antenna.

9. The transmission-side apparatus according to claim 8 , wherein the phase rotation amount φ(g,n) is acquired so that received reference signals from transmission-side apparatuses not belonging to the group g are cancelled when a phase rotation amount opposite to the phase rotation amount φ(g,n) is given to a received reference signal r(n) that is received by a receiving antenna by the n-th reference signal transmission in the repetition and that includes a transmitted reference signal from each of the K transmission-side apparatuses, and the first to N-th received reference signals in the repetition are added.

10. The transmission-side apparatus according to claim 9 , wherein the phase rotation amount φ(g,n) is acquired such that a phase sequence Φg1 and a phase sequence Φg2 are orthogonal to each other in all of combinations of two groups g1 and g2 (g1=1, . . . , G; g2=1, . . . , G; g1≠g2) among the G groups.

11. The transmission-side apparatus according to claim 9 , wherein the G groups are generated based on ascending order of propagation losses from the K transmission-side apparatuses, descending order of received signal powers or ascending order of signal-to-noise ratios.

12. The transmission-side apparatus according to claim 9 , wherein

when change in the number of the transmission-side apparatuses configured to simultaneously receive signals, change in members of the K transmission-side apparatuses, or change in order of magnitudes of received signal powers from the K transmission-side apparatuses is detected, the phase rotation amount φ(g,n) is newly acquired; and

the controller receives a phase sequence Φg={φ(g,1), . . . , φ(g,N)} assigned to the group g (g: an integer from 1 to G) to which the transmission-side apparatus itself belongs, from the reception-side apparatus, the phase sequence Φg being acquired from the newly acquired phase rotation amount φ(g,n).

13. The transmission-side apparatus according to claim 9 , wherein the reception-side apparatus

acquires, by giving the phase rotation amount opposite to the phase rotation amount φ(g,n) for the group g (g=1, . . . , G) to the received reference signal r(n) and adding the first to N-th received reference signals in the repetition to cancel received reference signals from transmission-side apparatuses not belonging to the group g, a received reference signal r(g) (g=1, . . . , G) of the group g that includes received reference signals from one or more transmission-side apparatuses belonging to the group g, and

performs communication channel estimation based on the received reference signal r(g) (g=1, . . . , G).

14. A method executed by a computer comprising:

when signals are simultaneously received from K transmission-side apparatuses (K: a positive integer) by a receiving antenna, and repetition of repeatedly and successively transmitting the same signal N times (N: a positive integer) is performed by the K transmission-side apparatuses,

dividing the K transmission-side apparatuses into G groups (G: a positive integer; 1<G≤K),

acquiring, in order to obtain a transmitted reference signal x(k,n) transmitted from a transmission-side apparatus k (k=1, . . . , K) included among the K transmission-side apparatuses by the n-th (n=1, . . . , N) reference signal transmission in the repetition, a phase rotation amount φ(g,n) that is a phase rotation amount given to a transmitted reference signal x(k) and that is assigned to a group g (g=1, . . . , G) to which the transmission-side apparatus k belongs so that received reference signals from transmission-side apparatuses not belonging to the group g are cancelled when giving a phase rotation amount opposite to the phase rotation amount φ(g,n) to a received reference signal r(n) that is received by the receiving antenna by the n-th reference signal transmission in the repetition and that includes a transmitted reference signal from each of the K transmission-side apparatuses and adding the first to N-th received reference signals in the repetition, and

transmitting a phase sequence Φg={φ(g,1), . . . , Φ(g,N)} that includes the phase rotation amount φ(g,n) for the group g for each of the first to N-th transmissions, to the transmission-side apparatus k.

15. The method according to claim 14 , wherein the computer acquires the phase rotation amount φ(g,n) such that a phase sequence Φg1 and a phase sequence Φg2 are orthogonal to each other in all of combinations of two groups g1 and g2 (g1=1, . . . , G; g2=1, . . . , G; g1≠g2) among the G groups.

16. The method according to claim 14 , wherein the computer generates the G groups based on ascending order of propagation losses from the K transmission-side apparatuses, descending order of received signal powers, or ascending order of signal-to-noise ratios.

17. The method according to claim 14 , wherein the computer

newly acquires the phase rotation amount φ(g,n) when detecting change in the number of the transmission-side apparatuses configured to simultaneously receive signals, change in members of the K transmission-side apparatuses or change in order of magnitudes of received signal powers from the K transmission-side apparatuses, and

transmits a phase sequence Φg that includes the newly acquired phase rotation amount φ(g,n) for the group g for each of the first to N-th transmissions, to the transmission-side apparatus k (k=1, . . . , K).

18. The method according to claim 14 , further comprising:

acquiring, by giving the phase rotation amount opposite to the phase rotation amount φ(g,n) for the group g (g=1, . . . , G) to the received reference signal r(n) and adding the first to N-th received reference signals in the repetition to cancel received reference signals from transmission-side apparatuses not belonging to the group g, a received reference signal r(g) (g=1, . . . , G) of the group g that includes received reference signals from one or more transmission-side apparatuses belonging to the group g, and

performing communication channel estimation based on the received reference signal r(g) (g=1, . . . , G).

19. The method according to claim 18 , further comprising:

acquiring a data signal d by adding data signals d(n) corresponding to the N times in the repetition, each of the data signals d(n) transmitted from the K transmission-side apparatuses by the n-th data signal transmission in the repetition, received by the receiving antenna, and including a data signal d(k,n) from the transmission-side apparatus k (k=1, . . . , K), and

separating a data signal d(k) received from the transmission-side apparatus k, from the data signal d using a result of the communication channel estimation.

20. The method according to claim 18 , wherein the computer simultaneously receives signals from the K transmission-side apparatuses by M receiving antennas (M: a positive integer), and, when each of the K transmission-side apparatuses performs the repetition, executes the communication channel estimation for each receiving antenna.