SYSTEM AND METHOD FOR CHANNEL STATE RELATED FEEDBACK IN MULTI-USER MULTIPLE-INPUT-MULTIPLE-OUTPUT SYSTEMS

• US 20110273977A1
• Filed: 05/04/2011
• Published: 11/10/2011
• Est. Priority Date: 05/04/2010
• Status: Active Grant

• Current Assignee: Celeno Communications, Ltd.
• Original Assignee: Celeno Communications, Ltd.
• Inventors: SHAPIRA, Nir, Shany, Yaron
• Granted Patent: US 8,934,328 B2
• Time in Patent Office: Days
• US Class Current: 370/208
• CPC Class Codes: H04B 7/0452 Multi-user MIMO systems
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0626 Channel coefficients, e.g. channel state information [CSI]
• CPC Class Codes: H04B 7/0658 Feedback reduction

Abstract

System and method for dimension reduction and for channel and interference condition feedback in a Multi-User Multiple-Input-Multiple-Output (MU MIMO) wireless communication systems. The method for dimension reduction includes determining a number of virtual antennas, v_k, for beamformees pertaining to a multi user (MU) transmission group, reducing the dimension of said matrix by selecting a sub-set of antennas or by Eigen mode selection and sending a reduced dimension candidate transmit beamforming matrix or an effective channel matrix to a beamformer. The method for channel and interference condition feedback Interference condition includes sending to a beamformee metric indicative of the interference level from other streams.

Claims

1. A method for dimension reduction, the method comprising:

sending a matrix related to channel sounding to a beamformer, said matrix has a dimension that is smaller than a maximum dimension.

2. The method of claim 1, wherein said matrix is a reduced dimension candidate transmit beamforming matrix, and wherein said maximum dimension is N_r×

min(n_k,N_r), where N_r is a number of antennas of said beamformer, and n_k is a number of antennas of said beamformee.

3. The method of claim 2, wherein said reduced dimension candidate transmit beamforming matrix is based on a V matrix from a Singular Value Decomposition (SVD) of a matrix selectable from a list comprising:

a channel matrix and an effective channel matrix.

4. The method of claim 3, wherein said reduced dimension candidate transmit beamforming matrix is sent together with a corresponding SNR vector which conveys per-stream SNR estimation.

5. The method of claim 1, wherein said matrix is an effective channel matrix, and wherein said maximum dimension is N_r×

n_k, where N_r is a number of antennas of said beamformer and n_k is a number of antennas of said beamformee.

6. The method of claim 1, further comprising:

receiving said reduced dimension value from said beamformer.

7. The method of claim 1, further comprising:

receiving said reduced dimension value from said beamformer as part of a sounding exchange.

8. The method of claim 1, further comprising:

reducing the dimension of said matrix by selecting a sub-set of antennas.

9. The method of claim 8, wherein said sub-set is selected according to Received Signal Strength Indicator (RSSI).

10. The method of claim 1, further comprising:

reducing the dimension of said matrix by Eigen mode selection.

11. The method of claim 1, further comprising:

obtaining a reduced dimension v_k;

obtaining channel matrix Ĥ

_k;

performing SVD of said channel matrix Ĥ

_k;

Ĥ

_k=UDV*;

composing a matrix Ũ

consisting of the v_k columns of U corresponding to largest singular values;

choosing a first stage RX beamforming matrix, B_k⁽¹⁾, to be a conjugate transpose of a matrix based on Ũ

; and

calculating said effective channel matrix by multiplying said channel matrix by said first stage RX beamforming matrix.

12. The method of claim 11, wherein B_k⁽¹⁾=Ũ

*.

13. The method of claim 1, further comprising:

deducing a final RX beamforming matrix from a MU transmission during reception of said transmission.

14. A method for dimension reduction, the method comprising:

determining a number of virtual antennas, v_k, for beamformees pertaining to at least one multi user (MU) transmission groups.

15. The method of claim 14, wherein said determining a number of virtual antennas, v_k, is done such that a total number of virtual antennas, summed on said beamformees, is not bigger than a number of beamformer antennas, N_r.

16. The method of claim 14, further comprising:

conveying said number of virtual antennas, v_k to said beamformees.

17. The method of claim 14, further comprising:

conveying said number of virtual antennas, v_k to said beamformees as part of a sounding exchange.

18. The method of claim 14, further comprising:

sounding said beamformees for matrices related to channel state information (CSI), wherein a dimension of said matrices is reduced to v_k.

19. The method of claim 18, further comprising:

designing TX beamforming matrix based on said matrices, using a TX beamforming matrix design method selectable from a list comprising;

zero forcing and block diagonalization.

20. The method of claim 18, wherein said matrices are reduced dimension candidate transmit beamforming matrices.

21. The method of claim 19, wherein said reduced dimension candidate transmit beamforming matrix is based on a V matrix from a Singular Value Decomposition (SVD) of a matrix selectable form a list comprising:

a channel matrix or an effective channel matrix.

22. The method of claim 21, wherein said reduced dimension candidate transmit beamforming matrix is sent together with a corresponding SNR vector which conveys per-stream SNR estimation.

23. The method of claim 18, wherein said matrices are an effective channel matrices.

24. The method of claim 14, further comprising:

assigning an initial number of virtual antennas to said beamformees; and

changing said number of virtual antennas during operation according to parameters selectable from a list comprising;

traffic buffer status, Received Signal Strength Indicator (RSSI), previous transmission rates and previous Modulation and Coding Schemes (MCSs), partial Channel State Information (CSI), full CSI and resulting overhead from sounding feedback.

25. The method of claim 14, further comprising:

selecting a subset of antennas for each of said beamformees;

conveying said subset to a corresponding beamformee; and

sounding said beamformees for a part of their channel matrix related to said subset of antennas.

26. The method of claim 14, when resolvable Long Training Fields (LTFs) are used, the method further comprising:

sounding full channels between said beamformer and said beamformees;

calculating reduced dimension effective channel matrices for said full channels; and

designing a TX beamforming matrix based on the reduced dimension effective channel matrices.