METHOD AND APPARATUS FOR ELIMINATING MULTI-USER INTERFERENCE IN MULTI-ANTENNA SYSTEM

• US 20100227562A1
• Filed: 03/04/2010
• Published: 09/09/2010
• Est. Priority Date: 03/04/2009
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: SHIM, Sei-Joon, Yun, Sang-Boh, Kim, Eun-Jung, Lee, Jae-Kon
• Granted Patent: US 8,467,729 B2
• Time in Patent Office: Days
• US Class Current: 455/63.100
• CPC Class Codes: H04B 7/0452 Multi-user MIMO systems
• CPC Class Codes: H04B 7/0665 Feed forward of transmit weights to the receiver
• CPC Class Codes: H04B 7/0862 receiver computing weights based on information from the transmitter
• CPC Class Codes: H04L 25/03891 Spatial equalizers MIMO diversity systems H04B7/0413
• CPC Class Codes: H04L 25/03993 Noise whitening
• CPC Class Codes: H04W 52/343 taking into account loading or congestion level
• CPC Class Codes: H04W 52/346 distributing total power among users or channels
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

A method and an apparatus are provided for eliminating multi-user interference in a multi-antenna system. In a BS, precoding vector information of at least one interfering user terminal interfering with a user terminal and information about a ratio of the transmission (TX) power of the user terminal to the total TX power of the BS are detected. A control signal including the detected information is transmitted to the user terminal.

Claims

1. A method, at a Base Station (BS), for eliminating multi-user interference in a multi-antenna system, comprising the steps of:

detecting precoding vector information of at least one interfering user terminal interfering with a user terminal and information about a ratio of a transmission (TX) power of the user terminal to a total TX power of the BS; and

transmitting a control signal comprising the precoding vector information and the information about the ratio to the user terminal.

2. The method of claim 1, wherein the at least one interfering user terminal uses the same subchannel as the user terminal.

3. The method of claim 1, wherein the control signal comprises an index of a table representing combinations of codebook indexes or a codebook index corresponding to a precoding matrix representing a precoding vector of the at least one interfering user terminal.

4. A method, at a user terminal, for eliminating multi-user interference in a multi-antenna system, comprising the steps of:

receiving a control signal comprising precoding vector information of at least one interfering user terminal and information about a ratio of a transmission (TX) power of the user terminal to a total TX power of a Base Station (BS) from the BS;

estimating an interference correlation matrix of the at least one interfering user terminal by using the precoding vector information and the information about the ratio in the control signal; and

whitening an interference of the at least one interfering user terminal by using the interference correlation matrix.

5. The method of claim 4, wherein the at least one interfering user terminal uses the same subchannel as the user terminal.

6. The method of claim 4, wherein the control signal comprises an index of a table representing combinations of codebook indexes or a codebook index corresponding to a precoding matrix representing a precoding vector of the at least one interfering user terminal.

7. The method of claim 4, wherein the interference correlation matrix is estimated using the following equation:

$\begin{array}{c}{R}_k=E<br><br>\left\{z_k<br><br>z_k^H\right\}\\ =P_d<br><br>\left(\frac{P_T}{P_d}-1+\frac{1}{\mathrm{\rho <br><br>}}\right)<br><br>H_k<br><br>{\tilde{M}}_k<br><br>{\tilde{M}}_k^H<br><br>H_k^H\end{array}$

where R_k denotes an interference correlation matrix of a user terminal k, E{} denotes an average operator, z_k denotes a downlink interference and noise by the at least one interfering user terminal, P_d denotes the TX power of the user terminal, P_T denotes the total TX power of the BS, ρ

denotes a power-to-noise ratio of the user terminal, H_k denotes a channel between the BS and the user terminal k, and {tilde over (M)}_k denotes the precoding matrix information of the at least one interfering user terminal for the user terminal k.

8. The method of claim 4, wherein whitening the interference of the at least one interfering user terminal comprises:

generating a reception (RX) matrix corresponding to a number of transport streams by using the interference correlation matrix; and

multiplying an RX signal by the RX matrix.

9. The method of claim 8, wherein, when there is a single transport stream, the RX matrix is generated using the following equation:

$W_k=\frac{{R_k^{-1}}^2<br><br>H_k<br><br>m_k}{{<br><br>{R_k^{-1}}^2<br><br>H_k<br><br>m_k<br><br>}_2}$

where W_k denotes the RX matrix for decoding, R_k denotes the interference correlation matrix, H_k denotes a channel between the BS and the user terminal k, and m_k denotes a precoding vector or matrix for the user terminal k.

10. The method of claim 8, wherein, when there are two or more transport streams, the RX matrix is generated using the following equation:

W_k=W_1,kW_2,k

W_1,k=R_k<sup>−

1 2</sup>, W_2,k=LSVD(R_zk<sup>−

1 2</sup>H_k)

where W_k denotes the RX matrix for decoding, W_1,k denotes a whitening filter, W_2,k denotes a filter maximizing a Signal-to-Noise Ratio (SNR) of an RX signal, R_k denotes the interference correlation matrix, LSVD(.) denotes left singular vectors corresponding to a number of transport streams among a left singular matrix obtained through Singular Value Decomposition (SVD), and H_k denotes a channel between the BS and the user terminal k.

11. An apparatus of a Base Station (BS) for eliminating multi-user interference in a multi-antenna system, comprising:

a controller for detecting precoding vector information of at least one interfering user terminal interfering with a user terminal and information about a ratio of a transmission (TX) power of the user terminal to a total TX power of the BS; and

a transmitter for transmitting a control signal comprising the precoding vector information and the information about the ratio to the user terminal.

12. The apparatus of claim 11, wherein the at least one interfering user terminal uses the same subchannel as the user terminal.

13. The apparatus of claim 11, wherein the control signal comprises an index of a table representing combinations of codebook indexes or a codebook index corresponding to a precoding matrix representing a precoding vector of the at least one interfering user terminal.

14. An apparatus of a user terminal for eliminating multi-user interference in a multi-antenna system, comprising:

a receiver for receiving a control signal comprising precoding vector information of at least one interfering user terminal and information about a ratio of a transmission (TX) power of the user terminal to a total TX power of a Base Station (BS) from the BS; and

a reception (RX) matrix applier for estimating an interference correlation matrix of the at least one interfering user terminal by using the precoding vector information and the information about the ratio in the control signal, and whitening an interference of the at least one interfering user terminal by using the interference correlation matrix.

15. The apparatus of claim 14, wherein the at least one interfering user terminal uses the same subchannel as the user terminal.

16. The apparatus of claim 14, wherein the control signal comprises an index of a table representing combinations of codebook indexes or a codebook index corresponding to a precoding matrix representing a precoding vector of the at least one interfering user terminal.

17. The apparatus of claim 14, wherein the interference correlation matrix is estimated using the following equation:

$\begin{array}{c}{R}_k=E<br><br>\left\{z_k<br><br>z_k^H\right\}\\ =P_d<br><br>\left(\frac{P_T}{P_d}-1+\frac{1}{\mathrm{\rho <br><br>}}\right)<br><br>H_k<br><br>{\tilde{M}}_k<br><br>{\tilde{M}}_k^H<br><br>H_k^H\end{array}$

where R_k denotes an interference correlation matrix of a user terminal k, E{} denotes an average operator, z_k denotes a downlink interference and noise by the at least one interfering user terminal, P_d denotes the TX power of the user terminal, P_T denotes the total TX power of the BS, ρ

denotes a power-to-noise ratio of the user terminal, H_k denotes a channel between the BS and the user terminal k, and {tilde over (M)}_k denotes the precoding matrix information of the at least one interfering user terminal for the user terminal k.

18. The apparatus of claim 14, wherein the RX matrix applier generates an RX matrix corresponding to a number of transport streams by using the interference correlation matrix, and multiplies an RX signal by the RX matrix.

19. The apparatus of claim 18, wherein, when there is a single transport stream, the RX matrix is generated using the following equation:

$W_k=\frac{{R_k^{-1}}^2<br><br>H_k<br><br>m_k}{{<br><br>{R_k^{-1}}^2<br><br>H_k<br><br>m_k<br><br>}_2}$

where W_k denotes the RX matrix for decoding, R_k denotes the interference correlation matrix, H_k denotes a channel between the BS and the user terminal k, and m_k denotes a precoding vector or matrix for the user terminal k.

20. The apparatus of claim 18, wherein, when there are two or more transport streams, the RX matrix is generated using the following equation:

W_k=W_1,kW_2,k

W_1,k=R_k<sup>−

1 2</sup>, W_2,k=LSVD(R_zk<sup>−

1 2</sup>H_k)

where W_k denotes the RX matrix for decoding, W_1,k denotes a whitening filter, W_2,k denotes a filter maximizing a Signal-to-Noise Ratio (SNR) of an RX signal, R_k denotes the interference correlation matrix, LSVD(.) denotes left singular vectors corresponding to a number of transport streams among a left singular matrix obtained through Singular Value Decomposition (SVD), and H_k denotes a channel between the BS and the user terminal k.