METHOD AND APPARATUS FOR LINEAR PRECODING IN MULTI-USER MULTIPLE-INPUT MULTIPLE-OUTPUT SYSTEM

• US 20140185700A1
• Filed: 03/06/2014
• Published: 07/03/2014
• Est. Priority Date: 09/06/2011
• Status: Abandoned Application

• Current Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Inventors: Dong, Mingjie, Cheng, Yao, Li, Sheng, Roemer, Florian, Zhang, Jianshu, Haardt, Martin
• Application Number:
  US14/198,899
• Publication Number:
  US 20140185700A1
• Time in Patent Office: Days
• US Class Current: 375/267
• CPC Class Codes: H04B 7/0452 Multi-user MIMO systems
• CPC Class Codes: H04B 7/0456 Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
• CPC Class Codes: H04B 7/0634 Antenna weights or vector/matrix coefficients
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

The present invention relates to the field of communications technologies and discloses a method and an apparatus for linear precoding in a multi-user multiple-input multiple-output system, which can reduce computational complexity, improve system efficiency, and enhance system robustness by using a linear precoding technology in the case of imperfect CSI. According to the solutions provided in embodiments of the present invention, a first matrix is determined according to channel information of the system; an equivalent-channel matrix is acquired according to the first matrix; the equivalent-channel matrix is decomposed, and a second matrix is obtained through computation; a precoding matrix is obtained according to the first matrix and the second matrix, so that a power balance is achieved between spatial streams of each user after two signals to be concurrently transmitted are processed by using the precoding matrix.

Claims

1. A method for linear precoding in a multi-user multiple-input multiple-output system, the method comprising:

determining a first matrix according to channel information of the system, wherein the first matrix is used to cancel or suppress multi-user interference;

acquiring an equivalent-channel matrix according to the first matrix, wherein the equivalent-channel matrix is used to indicate channel information of the system after interference is canceled;

decomposing the equivalent-channel matrix, and obtaining a second matrix through computation, wherein diagonal elements of matrix blocks corresponding to each user in the second matrix are equal and the second matrix is used to optimize system performance; and

obtaining a precoding matrix according to the first matrix and the second matrix, so that a power balance is achieved between spatial streams of each user after at least two signals to be concurrently transmitted are processed by using the precoding matrix.

2. The method for linear precoding in a multi-user multiple-input multiple-output system according to claim 1, wherein determining a first matrix according to channel information of the system comprises:

determining, according to the channel information of the system, the first matrix by using a linear closed-loop precoding technology.

3. The method for linear precoding in a multi-user multiple-input multiple-output system according to claim 2, wherein decomposing the equivalent-channel matrix and obtaining a second matrix through computation comprise:

decomposing an equivalent-channel matrix of an i^th user according to H_eq,i=Q_iR_iP_i^H, so that diagonal elements in the equivalent-channel matrix of the i^th user are equal, and obtaining through computation that F_i=P_i, wherein H_eq,i refers to the equivalent-channel matrix of the i^th user, Q_i refers to a column orthogonal matrix, R_i refers to an upper triangular matrix, P_i refers to a block diagonal matrix, and Q^HQ=P^HP=I_L, wherein L refers to a rank of a channel matrix H, I refers to a unit matrix, and F_i refers to a second matrix of the i^th user; and

obtaining F_b according to the method for obtaining F_i, wherein F_b refers to the second matrix.

4. The method for linear precoding in a multi-user multiple-input multiple-output system according to claim 3, wherein decomposing the equivalent-channel matrix and obtaining a second matrix through computation comprise:

computing a power allocation matrix based on a preset matrix, wherein diagonal elements of matrix blocks corresponding to each user in the preset matrix are diagonal elements in the R_i;

decomposing, based on a preset diagonal matrix, the equivalent-channel matrix of the i^th user according to H_{eq, i}=Q_iR_iP_i^H, so that diagonal elements in the equivalent-channel matrix of the i^th user are equal, and obtaining through computation that F_i=P_i, wherein diagonal elements of the preset diagonal matrix are the same as those of the R_i and G refers to the power allocation matrix; and

obtaining F_b according to the method for obtaining F_i, wherein F_b refers to the second matrix.

5. The method for linear precoding in a multi-user multiple-input multiple-output system according to claim 4, wherein computing a power allocation matrix based on a preset matrix comprises:

computing the power allocation matrix according to

6. The method for linear precoding in a multi-user multiple-input multiple-output system according to claim 1, wherein obtaining a precoding matrix according to the first matrix and the second matrix comprises:

obtaining the precoding matrix according to F=β

F_aF_b, wherein F refers to the precoding matrix, β

refers to a power control factor, F_a refers to the first matrix, and F_b refers to the second matrix.

7. An apparatus for linear precoding in a multi-user multiple-input multiple-output system, the apparatus comprising:

a determining unit, configured to determine a first matrix according to channel information of the system, wherein the first matrix is used to cancel or suppress multi-user interference;

a first acquiring unit, configured to acquire an equivalent-channel matrix according to the first matrix, wherein the equivalent-channel matrix is used to indicate channel information of the system after interference is canceled;

a computing unit, configured to decompose the equivalent-channel matrix and obtain a second matrix through computation, wherein diagonal elements of matrix blocks corresponding to each user in the second matrix are equal and the second matrix is used to optimize system performance; and

a second acquiring unit, configured to obtain a precoding matrix according to the first matrix and the second matrix, so that a power balance is achieved between spatial streams of each user after at least two signals to be concurrently transmitted are processed by using the precoding matrix.

8. The apparatus for linear precoding in a multi-user multiple-input multiple-output system according to claim 7, wherein the determining unit is configured to:

determine, according to the channel information of the system, the first matrix by using a linear closed-loop precoding technology.

9. The apparatus for linear precoding in a multi-user multiple-input multiple-output system according to claim 8, wherein the computing unit comprises:

a first computing module, configured to decompose an equivalent-channel matrix of an i^th user according to H_eq,i=Q_iR_iP_i^H, so that diagonal elements in the equivalent-channel matrix of the i^th user are equal, and obtain through computation that F_i=P_i, wherein H_eq,i refers to the equivalent-channel matrix of the i^th user, Q_i refers to a column orthogonal matrix, R_i refers to an upper triangular matrix, P_i refers to a block diagonal matrix, and Q^HQ=P^HP=I_L, wherein L refers to a rank of a channel matrix H, I refers to a unit matrix, and F_i refers to a second matrix of the i^th user, and

the first computing module is further configured to obtain F_b according to the method for obtaining F_i, wherein F_b refers to the second matrix.

10. The apparatus for linear precoding in a multi-user multiple-input multiple-output system according to claim 9, wherein the computing unit comprises:

a second computing module, configured to compute a power allocation matrix based on a preset matrix, wherein diagonal elements of matrix blocks corresponding to each user in the preset matrix are elements in the diagonal matrix R_i; and

a third computing module, configured to decompose, based on a preset diagonal matrix, the equivalent-channel matrix of the i^th user according to H_eq,i=Q_iR_iP_i^H, so that diagonal elements in the equivalent-channel matrix of the i^th user are equal, and obtain through computation that F_i=P_iG, wherein diagonal elements of the preset diagonal matrix are the same as those of the R_i and G refers to the power allocation matrix, and

the third computing module is further configured to obtain F_b according to the method for obtaining F_i, wherein F_b refers to the second matrix.

11. The apparatus for linear precoding in a multi-user multiple-input multiple-output system according to claim 10, wherein the second computing module is configured to:

compute the power allocation matrix according to

12. The apparatus for linear precoding in a multi-user multiple-input multiple-output system according to claim 7, wherein the second acquiring unit is configured to:

obtain the precoding matrix according to F=β

F_aF_b, wherein F refers to the precoding matrix, β

refers to a power control factor, F_a refers to the first matrix, and F_b refers to the second matrix.