Apparatus and method for selecting effective channel in a multi-user MIMO system

• US 20070253508A1
• Filed: 04/19/2007
• Published: 11/01/2007
• Est. Priority Date: 04/19/2006
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Zhou, Yong-Xing, Kim, Sung-Jin, Li, JianJun, Kim, Ho-Jin
• Granted Patent: US 7,894,505 B2
• Time in Patent Office: Days
• US Class Current: 375/267
• CPC Class Codes: H04B 7/0626 Channel coefficients, e.g. channel state information [CSI]
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication

Abstract

An apparatus and method for selecting an effective channel in a multi-user MIMO system are provided, in which a receiver receives pilot signals from a transmitter, determines channel information indicating an antenna offering the best quality among a plurality of antennas using the pilot signals, and generates feedback information with the channel information, and the transmitter receives feedback information from a plurality of receivers, generates a channel matrix using the feedback information, and transmits data simultaneously to the plurality of receivers using the channel matrix.

Claims

1. A multi-user Multiple-Input Multiple-Output (MIMO) system comprising:

a receiver for receiving pilot signals from a transmitter, determining channel information indicating an antenna among a plurality of antennas using the pilot signals, and generating feedback information with the channel information; and

the transmitter for receiving feedback information from a plurality of receivers, generating a channel matrix using the feedback information, and transmitting data simultaneously to the plurality of receivers using the channel matrix.

2. The multi-user MIMO system of claim 1, wherein the channel information extracted from the pilot signals is calculated by obtaining decomposed channel information by SVD(Singular Value Decompositon) and multiplying the decomposed channel information by the channel matrix.

3. The multi-user MIMO system of claim 1, wherein the feedback information includes a Hermitian matrix having channel information

4. The multi-user MIMO system of claim 1, wherein the transmitter calculates backward filter information B^H_block forward filter information F^H_block and a scaling factor β

^H_block for each of the receivers using the channel information received from each receiver.

5. The multi-user MIMO system of claim 4, wherein the transmitter sends the scaling factor to each receiver.

6. The multi-user MIMO system of claim 4, wherein the backward filter information B^H_block is a unit lower triangular matrix and the transmitter controls the power of transmission data using the backward filter information B^H_block.

7. The multi-user MIMO system of claim 4, wherein the transmitter calculates the forward filter information F^H_block by F^H_block=β

^H_blockH^H_effP^T_blockL<sup>−

H</sup>_blockD<sup>−

1</sup>_block in which D_block is a diagonal matrix and the transmitter calculates the scaling factor β

^H_block for the each receiver to satisfy transmit power.

8. The multi-user MIMO system of claim 4, wherein the scaling factor β

^H_block represents the modulo level of a modulo operation performed in the transmitter.

9. A channel selection method in a multi-user Multiple-Input Multiple-Output (MIMO) system, comprising:

receiving pilot signals through a plurality of antennas from a transmitter and measuring the channel information with respect to the plurality of antennas using the pilot signals by each of a plurality of receivers;

sending feedback information with channel information indicating the channel information measurement to the transmitter by each receiver;

receiving the feedback information from the plurality of receivers and generating a channel matrix using the feedback information by the transmitter; and

transmitting data simultaneously to the plurality of receivers using the channel matrix.

10. The channel selection method of claim 9, wherein the channel information extracted from the pilot signal is calculated by obtaining decomposed channel information by the SVD and multiplying the decomposed channel information by the channel matrix.

11. The channel selection method of claim 9, wherein the channel matrix generation comprises generating the channel matrix including backward filter information B^H_block, forward filter information F^H_block, and a scaling factor β

^H_block, the backward filter information B^H_block, the forward filter information F^H_block, and the scaling factor β

^H_block being calculated for the each receiver using the feedback information received from the each receiver.

12. The channel selection method of claim 11, further comprising sending the scaling factor to each receiver.

13. An apparatus of a receiver for extracting channel information in a multi-user Multiple-Input Multiple-Output (MIMO) system, comprising:

a receive beamformer for, upon receipt of different signals through a plurality of antennas, determining channel information indicating channel information using the received signals and sending the channel information to a transmitter; and

a multiplier for, upon receipt of a scaling factor from the transmitter, multiplying an input signal by the inverse of the scaling factor.

14. The apparatus of claim 13, wherein the scaling factor represents the modulo level of a modulo operation performed in the transmitter.

15. The apparatus of claim 13, wherein the channel information extracted from the pilot signal is calculated by obtaining decomposed channel information by the SVD and multiplying the decomposed channel information by the channel matrix.

16. The apparatus of claim 13, wherein the signals include pilot signals.

17. A method of a receiver for extracting channel information in a multi-user Multiple-Input Multiple-Output (MIMO) system, comprising:

receiving signals through a plurality of antennas;

determining channel information indicating channel information using the received signals; and

sending the channel information to a transmitter.

18. The method of claim 17, wherein the channel information extracted from the pilot signal is calculated by obtaining decomposed channel information by the SVD and multiplying the decomposed channel information by the channel matrix.

19. An apparatus of a transmitter for selecting a channel in a multi-user Multiple-Input Multiple-Output (MIMO) system, comprising:

an extractor for, upon receipt of channel information from a plurality of receivers, extracting filter information from the channel information;

a Tomlinson-Harashima Precoding (THP) part for controlling the power of data using the filter information; and

a beamforming part for controlling beamforming for a plurality of antennas using the filter information in order to simultaneously transmit the power-controlled data to the plurality of receivers.

20. The apparatus of claim 19, wherein the THP part comprises:

a permutation matrix portion for ordering an input signal;

a backward filter for filtering the ordered signal; and

a modulo operator for controlling the power of the signal increased by the backward filter.

21. The apparatus of claim 19, wherein the channel information extracted from the pilot signal is calculated by obtaining decomposed channel information by the SVD and multiplying the decomposed channel information by the channel matrix.

22. The apparatus of claim 19, wherein the filter information includes backward filter information B^H_block forward filter information F^H_block, and a scaling factor β

^H_block.

23. The apparatus of claim 22, wherein the backward filter information B^H_block is unit lower triangular and the THP part controls the power of the data using the backward filter information B^H_block.

24. The apparatus of claim 22, wherein the extractor calculates the forward filter information F^H_block by F^H_block=β

^H_blockH^H_effP^T_blockL<sup>−

H</sup>_blockD<sup>−

1</sup>_block in which D_block is a diagonal matrix and calculates the scaling factor β

^H_block to satisfy transmit power.

25. The apparatus of claim 22, wherein the scaling factor β

^H_block represents the modulo level of a modulo operation performed in the transmitter.

26. A method of a transmitter for selecting a channel in a multi-user Multiple-Input Multiple-Output (MIMO) system, comprising:

extracting, upon receipt of channel information from a plurality of receivers, filter information from the channel information;

controlling the power of data using the filter information; and

controlling beamforming for a plurality of antennas using the filter information in order to simultaneously transmit the power-controlled data to the plurality of receivers.

27. The method of claim 26, wherein the channel information represents the channel state of an antenna among antennas of each of the receivers, including a Hermitian matrix H_eff having channel information and a channel noise.

28. The method of claim 26, wherein the filter information includes backward filter information B^H_block, forward filter information F^H_block, and a scaling factor β

^H_block.

29. The method of claim 28, wherein the backward filter information B^H_block is unit lower triangular and the power control comprises controlling the power of the data using the backward filter information B^H_block.

30. The method of claim 28, wherein the extraction comprises calculating the forward filter information F^H_block by F^H_block=β

^H_blockH^H_effP^T_blockL<sup>−

H</sup>_blockD<sup>−

1</sup>_block in which D_block is a diagonal matrix and calculating the scaling factor β

^H_block to satisfy transmit power.

31. The method of claim 28, wherein the beamforming control comprises controlling the beamforming for the plurality of antennas using the forward filter information F^H_block.

32. A computer-readable recording medium storing a program for selecting a channel in a multi-user Multiple-Input Multiple-Output (MIMO) system, comprising:

a first set of instructions for receiving pilot signals through a plurality of antennas from a transmitter and measuring the channel information with respect to the plurality of antennas using the pilot signals by each of a plurality of receivers;

a second set of instructions for sending feedback information with channel information indicating the channel information measurement to the transmitter by each receiver;

a third set of instructions for receiving the feedback information from the plurality of receivers and generating a channel matrix using the feedback information by the transmitter; and

a fourth set of instructions for transmitting data simultaneously to the plurality of receivers using the channel matrix.

33. A computer-readable recording medium storing a program for extracting channel information in a multi-user Multiple-Input Multiple-Output (MIMO) system, comprising:

a first set of instructions for receiving unique signals through a plurality of antennas;

a second set of instructions for determining channel information indicating channel information using the received signals; and

a third set of instructions for sending the channel information to a transmitter.

34. A computer-readable recording medium storing a program for selecting a channel in a multi-user Multiple-Input Multiple-Output (MIMO) system, comprising:

a first set of instructions for extracting, upon receipt of channel information from a plurality of receivers, filter information from the channel information;

a second set of instructions for controlling the power of data using the filter information; and

a third set of instructions for controlling beamforming for a plurality of antennas using the filter information in order to simultaneously transmit the power-controlled data to the plurality of receivers.