RECEIVER, COMMUNICATION SYSTEM, AND METHOD IMPLEMENTED BY COMPUTER FOR ENABLING BOTH ANALOG AND DIGITAL BEAMFORMING IN COMMUNICATION SYSTEM

• US 20200136691A1
• Filed: 05/10/2018
• Published: 04/30/2020
• Est. Priority Date: 05/17/2017
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: LI, Qianrui
• Granted Patent: US 11,152,984 B2
• Time in Patent Office: Days
• CPC Class Codes: H04B 7/0417 Feedback systems
• CPC Class Codes: H04B 7/0478 Special codebook structures directed to feedback optimisation
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0634 Antenna weights or vector/matrix coefficients
• CPC Class Codes: H04L 25/0248 Eigen-space methods
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 27/2644 with oversampling

Abstract

A method for enabling hybrid beamforming in a communication system including a transmitter being able to serve a plurality of receivers, wherein a frequency band comprises at least one subcarrier, wherein each receiver is associated to a set Cprec,k of analog precoiling codewords, said method comprising: —for each receiver, computing (202) an analog precoding matrix FRF k associated to said receiver; said computation (202) comprising: /a/ for each subcarrier, performing (202a) a Singular Value Decomposition, SVD, on a channel matrix associated to said receiver and to said each subcarrier; /b/ for each subcarrier, determining a first decomposition matrix Vk(1) based on the relative SVD; /c/ determining (303) an analog precoding codeword which optimizes a first function g1(Vk(1), . . . , Vk(L), F) of Vk(1), . . . , Vk(L) and F, for a plurality of F E Cprec,k, wherein L denotes a number of subcarriers.

Claims

1-15. -15. (canceled)

16. A method implemented by a computer for maximizing a sum rate of a communication system, said communication system enabling both analog and digital beamforming, said communication system including a transmitter being able to serve a plurality of receivers,

wherein each receiver among the plurality of receivers is associated to a relative set _prec,k of analog precoding codewords, wherein _prec,k is the set of analog precoding codewords associated to the k^th receiver,

said method comprising:

for each receiver among the plurality of receivers, computing, at said receiver, an analog precoding matrix F_RF,k associated to said receiver,

wherein F_RF,k is the analog precoding matrix associated to the k^th receiver; and

using at least one computed analog precoding matrix for processing at least one signal to transmit from the transmitter to at least one receiver;

wherein the computation of the analog precoding matrix associated to a receiver among the plurality of receivers comprises;

 

/a/ performing a Singular Value Decomposition, SVD, on a channel matrix associated to said receiver;

 

/b/ determining a first decomposition matrix V_k based on the relative SVD;

characterized in that the computation of the analog precoding matrix associated to a receiver among the plurality of receivers further comprises;

 

/c/ determining an analog precoding codeword which maximizes a first function g₁(V_k, F)=λ

_min(V_k^HFF^HV_k) of V_k and F, for a plurality of F∈

_prec,k,

where;

A^H denotes a conjugate transpose matrix of a matrix A; and

λ

_min(A) denotes a minimal eigenvalue of a matrix A.

18. The method according to claim 16, wherein each receiver among the plurality of receivers is associated to a relative set _comb,k of analog combining codewords,

wherein, for each receiver among the plurality of receivers and for each subcarrier among the plurality of subcarriers, a second decomposition matrix Ū

_k(l) is determined, based on the relative SVD performed in step /a/;

the method further comprising, for each receiver among the plurality of receivers;

computing, at said receiver, an analog combining matrix W_RF,k associated to said receiver, said computation including;

determining an analog combining codeword which optimizes a second function g₂(Ū

_k(1), . . . , Ū

_k(L), W) of Ū

_k(1), . . . , Ū

_k(L) and W, for a plurality of W∈

═

_comb,k.

20. The method according to claim 18, wherein the second function is:

21. The method according to claim 18, wherein the number of subcarriers is equal to 1,

wherein each analog precoding codeword F is chosen among a set of columns of a predetermined matrix having a number of rows equal to a number of antennas of the transmitter and a number of columns greater or equal than L_rk, said matrix being a Discrete Fourier Transform, DFT, matrix or a matrix obtained by re-normalizing a sub-matrix extracted from a DFT matrix,

and wherein the second function g₂(Ū

_k, W) is given by;

22. The method according to claim 18, wherein the number of subcarriers is equal to 1, and wherein the second function g₂(U_k, W) is given by:

g₂(Ū

_k, W)=λ

_min(Ū

_k^HWW^HŪ

_k)

where;

A^H denotes a conjugate transpose matrix of a matrix A; and

λ

_min(A) denotes a minimal eigenvalue of a matrix A.

and wherein the optimization of the second function is a maximization.

23. The method according to claim 18, wherein an analog combining codeword W is a column of a predetermined matrix having a number of rows equal to a number of antennas of the transmitter and a number of columns greater or equal than L_rk, said matrix being relative to Discrete Fourier Transform, DFT, matrix;

wherein, in step /c/ the second function g₂(Ū

_k, W) is a function of;

24. The method according to claim 18, the method further comprising:

for each receiver among the plurality of receivers, receiving, at the transmitter, an estimation of an equivalent user channel between the transmitter and said each receiver;

recursively computing, at the transmitter;

a first set of digital combining matrices, each digital combining matrix of said first set being associated to a receiver among the plurality of receivers, based on the received estimation of the equivalent user channel and on the computed analog combining matrices; and

a second set of digital precoding matrices, each digital precoding matrix of said second set being associated to a receiver among the plurality of receivers, based on the received estimation of the equivalent user channel and at least one digital combining matrix among the first set;

wherein the recursive computation includes;

/d/ For each receiver k among the plurality of K receivers,

Calculate;

28. A computer program product, comprising instructions for performing the method as claimed in claim 16, when run by a processor.

17. A method implemented by a computer for maximizing a sum rate of a communication system, said communication system enabling both analog and digital beamforming, said communication system including a transmitter being able to serve a plurality of receivers,

wherein each receiver among the plurality of receivers is associated to a relative set _prec,k of analog precoding codewords, wherein _prec,k is the set of analog precoding codewords associated to the k^th receiver,

wherein each analog precoding codeword F is a column of a predetermined matrix having a number of rows equal to a number of antennas of the transmitter and a number of columns greater or equal than L_rk, said matrix being a Discrete Fourier Transform, DFT, matrix or a matrix obtained by re-normalizing a sub-matrix extracted from a DFT matrix;

said method comprising;

for each receiver among the plurality of receivers, computing, at said receiver, an analog precoding matrix F_RF,k associated to said receiver, wherein F_RF,k is the analog precoding matrix associated to the k^th receiver; and

using at least one computed analog precoding matrix for processing at least one signal to transmit from the transmitter to at least one receiver;

wherein the computation of the analog precoding matrix associated to a receiver among the plurality of receivers comprises;

 

/a/ performing a Singular Value Decomposition, SVD, on a channel matrix associated to said receiver;

 

/b/ determining a first decomposition matrix V_k based on the relative SVD;

characterized in that the computation of the analog precoding matrix associated to a receiver among the plurality of receivers further comprises;

 

/c/ determining an analog precoding codeword which maximizes a first function g₁(V_k, F) of V_k and F, said first function being function of;

19. The method according to claim 17, wherein each receiver among the plurality of receivers is associated to a relative set _comb,k of analog combining codewords,

wherein, for each receiver among the plurality of receivers and for each subcarrier among the plurality of subcarriers, a second decomposition matrix Ū

_k(l) is determined, based on the relative SVD performed in step /a/;

the method further comprising, for each receiver among the plurality of receivers;

computing, at said receiver, an analog combining matrix W_RF,k associated to said receiver, said computation including;

determining an analog combining codeword which optimizes a second function g₂(Ū

_k(1), . . . , Ū

_k(L), W) of Ū

_k(1), . . . , Ū

_k(L) and W, for a plurality of W∈

_comb,k.

29. A computer program product, comprising instructions for performing the method as claimed in claim 17, when run by a processor.

25. A receiver configured to receive data from a transmitter able to serve a plurality of receivers, in a communication system enabling both analog and digital beamforming,

said receiver being associated to a set _prec,k of analog precoding codewords,

said receiver comprising a circuit for maximizing a sum rate of the communication system, said maximization including a computation of an analog precoding matrix F_RF,k,

wherein the computation of the analog precoding matrix comprises:

 

/a/ performing a Singular Value Decomposition, SVD, on a channel matrix;

 

/b/ determining a first decomposition matrix V_k based on said SVD; and

characterized in that the computation of the analog precoding matrix associated to a receiver among the plurality of receivers further comprises;

 

/c/ determining an analog precoding codeword which maximizes a first function g₁(V_k, F)=λ

_min(V_k^HFF^HV_k) of V_k and F, for a plurality of F∈

_prec,k,

where;

A^H denotes a conjugate transpose matrix of a matrix A; and

λ

_min(A) denotes a minimal eigenvalue of a matrix A.

26. The receiver according to claim 25, said receiver being further associated to a relative set _comb,k of analog combining codewords,

wherein for each subcarrier among the plurality of subcarriers, a second decomposition matrix Ū

_k(l) is determined, based on said SVD;

said receiver further comprising a circuit for computing an analog combining matrix W_RF,k, said computation including;

determining an analog combining codeword which optimizes a second function g₂(Ū

_k(1), . . . , Ū

_k(L), W) of Ū

_k(1), . . . , Ū

_k(1), . . . , Ū

_k(L) and W, for a plurality of W∈

_comb,k.

27. A communication system enabling both analog and digital beamforming, said system comprising a transmitter being able to serve a plurality of receivers, wherein each receiver is as claimed in claim 25.