Codebook selection for transmit beamforming

• US 8,442,138 B2
• Filed: 03/07/2008
• Issued: 05/14/2013
• Est. Priority Date: 03/07/2007
• Status: Active Grant

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell World Trade Limited (Marvell Technology Group Limited)
• Inventors: Zhang, Hongyuan, Nabar, Rohit U.
• Primary Examiner(s): Payne, David C.
• Assistant Examiner(s): Hassan, Sarah
• Application Number:
  US12/044,117
• Publication Number:
  US 20080219373A1
• Time in Patent Office: 1,894 Days
• Field of Search: 375/262, 375/211, 341/67
• US Class Current: 375/262
• CPC Class Codes: H04B 7/0417 Feedback systems
• CPC Class Codes: H04B 7/0634 Antenna weights or vector/matrix coefficients
• CPC Class Codes: H04B 7/0639 Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection

Abstract

A method select a codebook for transmit beamforming. The method constructs an estimated channel matrix based on a codebook, selects a channel submatrix from the estimated channel matrix, calculates a selection matrix from the channel submatrix; and assigns a steering matrix based on the selection matrix. There may be multiple codebooks and the method may construct an estimated channel matrix, select a channel submatrix, and calculate a selection matrix for each of the codebooks, then select an optimal codebook. The steering matrix is assigned based on the optimal codebook. The steering matrix may be used in steering a transmitted packet. The method may also calculate a post-MIMO equalizer signal-to-noise ratio for a data stream, based on the estimated channel matrix and the selected codebook. A related system is also disclosed. Other embodiments are provided, and each of the embodiments described herein can be used alone or in combination with one another.

Claims

1. A method for selecting a codebook, comprising:

receiving, by a beamformee, channel state information and a sounding spatial mapping matrix set to a codebook from a beamformer, the codebook used to assign a steering matrix for transmit beamforming;

constructing, using at least one controller, an estimated channel matrix based on the sounding spatial mapping matrix set to the codebook received from the beamformer, the sounding spatial mapping matrix being stored in a memory;

selecting, using the at least one controller, a channel submatrix from the estimated channel matrix;

calculating, using the at least one controller, a selection matrix from the channel submatrix; and

assigning, using the at least one controller, a steering matrix based on the selection matrix.

2. The method of claim 1, wherein:

the codebook comprises a plurality of codebooks;

constructing the estimated channel matrix comprises constructing the estimated channel matrix for each of the plurality of codebooks;

selecting the channel submatrix comprises selecting the channel submatrix for each of the plurality of codebooks;

calculating the selection matrix comprises calculating the selection matrix for each of the plurality of codebooks; and

assigning the steering matrix comprises;

selecting an optimal codebook based on a criterion from the plurality of codebooks; and

assigning the steering matrix based on the selection matrix corresponding to the optimal codebook.

3. The method of claim 1, further comprising transmitting a steered packet based on the assigned steering matrix.

4. The method of claim 1, further comprising:

setting the sounding spatial mapping matrix to the codebook for sending a sounding packet;

wherein constructing the estimated channel matrix comprises;

calculating an estimated composite channel matrix based on the codebook, wherein the estimated composite channel matrix is the multiplication of a channel matrix and the sounding spatial mapping matrix;

constructing the estimated composite channel matrix based on each of the other codebooks in the case that the codebook comprises a plurality of codebooks;

multiplying the existing estimated composite channel matrix with the transpose conjugate of the first codebook matrix applied as the sounding spatial mapping matrix;

multiplying the result with the currently considered codebook matrix.

5. The method of claim 1, wherein calculating the selection matrix comprises:

if using implicit transmit beamforming or explicit transmit beamforming with channel state information feedback, calculating the selection matrix at the beamformer;

if using explicit transmit beamforming with steering matrix feedback, calculating the selection matrix at the beamformee, and feeding back the selection matrix to the beamformer.

6. The method of claim 5, wherein if using explicit transmit beamforming with steering matrix feedback, and if the codebook contains only one codebook, the selection matrix fed back to the beamformer comprises 0 and 1 elements;

further wherein the feedback matrix is either in the form of a matrix with quantized elements with small number of quantization bit(s), or in the form of the indices numbers of the selected columns so that the beamformer, before assigning the steering matrix, can translate the indices numbers back to the selection matrix.

7. The method of claim 1, further comprising:

calculating a post-MEQ signal-to-noise ratio (SNR) for a data stream, based on the estimated channel matrix and the codebook;

selecting a modulation and coding scheme (MCS) based on the post-MEQ SNR;

generating a selection value corresponding to the selected MCS; and

applying the selected MCS to a steered packet.

8. The method of claim 7, wherein calculating the post-MEQ SNR comprises selecting a column of the estimated channel matrix with a largest norm.

9. The method of claim 7, wherein:

the data stream comprises a plurality of data streams;

calculating the post-MEQ SNR comprises calculating the post-MEQ SNR for each of the plurality of data streams; and

selecting the MCS comprises selecting the optimal MCS based on the post-MEQ SNR.

10. The method of claim 9, wherein calculating the post-MEQ SNR for each of the plurality of data streams comprises:

calculating a norm of each column of the estimated channel matrix;

projecting the column to a null space of space spanned by previous columns;

calculating a projection of each previous column to a null space of space spanned by remaining columns, if the post-MEQ SNR is directly used; and

storing the post-MEQ SNR for the data stream.

21. The method of claim 1, wherein receiving channel state information and the sounding spatial mapping matrix set to a codebook from a beamformer comprises receiving the channel state information multiplied by the codebook.

22. The method of claim 1, wherein receiving, by the beamformee, channel state information and the sounding spatial mapping matrix set to the codebook from the beamformer comprises receiving, by the beamformee, channel state information and the sounding spatial mapping matrix set to the codebook from the beamformer if using explicit beam forming, the method further comprises:

if using implicit transmit beamforming;

sending a sounding packet from the beamformee to beamformer;

calculating an estimated reverse link channel matrix based on the received sounding packet at the beamformer;

transposing the estimated reverse link channel matrix to form an estimated forward link channel matrix; and

calculating an estimated composite channel matrix by multiplying the estimated forward link channel matrix and the codebook matrix.

11. A codebook selection system, comprising:

a beamformee having at least one receiver that is configured to receive channel state information and a sounding spatial mapping matrix set to a codebook from a beamformer, the codebook used to assign a steering matrix for transmit beamforming;

at least one memory configured to store the codebook; and

one or more controllers in communication with the at least one memory, the one or more controllers configured to;

construct an estimated channel matrix based on the codebook received from the beamformer;

select a channel submatrix from the estimated channel matrix;

calculate a selection matrix from the channel submatrix; and

assign a steering matrix based on the selection matrix.

12. The system of claim 11, wherein:

the codebook comprises a plurality of codebooks;

the one or more controllers further configured to;

construct the estimated channel matrix for each of the plurality of codebooks;

select the channel submatrix for each of the plurality of codebooks;

calculate the selection matrix for each of the plurality of codebooks;

select an optimal codebook based on a criterion from the plurality of codebooks; and

assign the steering matrix based on the selection matrix corresponding to the optimal codebook.

13. The system of claim 11, further comprising a packet transmitter in communication with the one or more controllers, the packet transmitter configured to transmit a steered packet based on the assigned steering matrix.

14. The system of claim 11, wherein the one or more controllers is further configured to:

set the sounding spatial mapping matrix to the codebook for sending a sounding packet, and calculate an estimated composite channel matrix based on the codebook, wherein the estimated composite channel matrix is the multiplication of a channel matrix and the sounding spatial mapping matrix;

construct the estimated composite channel matrix based on each of the other codebooks in the case that the codebook comprises a plurality of codebooks;

multiply the existing estimated composite channel matrix with the transpose conjugate of the first codebook matrix applied as the sounding spatial mapping matrix; and

multiply the result with the currently considered codebook matrix.

15. The system of claim 11, wherein the one or more controllers is further configured to use one or a combination of:

a Shannon Capacity maximization algorithm, a maximum of weakest post processing signal-to-noise ratio algorithm, an incremental selection algorithm, a decremental selection algorithm, and a correlation of estimated channel matrix columns algorithm.

16. The system of claim 11, wherein the one or more controllers is further configured to:

if using implicit transmit beamforming or explicit transmit beamforming with channel state information feedback, calculate the selection matrix at the beamformer;

if using explicit transmit beamforming with steering matrix feedback, calculate the selection matrix at the beamformee, and feed back the selection matrix to the beamformer.

17. The system of claim 16, wherein if using explicit transmit beamforming with steering matrix feedback, and if the codebook contains only one codebook, the selection matrix fed back to the beamformer comprises 0 and 1 elements, wherein the feedback matrix is either in the form of a matrix with quantized elements with small number of quantization bit(s), or in the form of the indices numbers of the selected columns so that the beamformer, before assigning the steering matrix, can translate the indices numbers back to the selection matrix.

18. The system of claim 11, wherein the one or more controllers is further configured to:

calculate for a post-MEQ SNR for a data stream, based on the estimated channel matrix and the codebook;

select a MCS based on the post-MEQ SNR;

generate a selection value corresponding to the selected MCS; and

apply the selected MCS to a steered packet.

19. The system of claim 18, wherein:

the data stream comprises a plurality of data streams;

the one or more controllers is further configured to;

calculate the post-MEQ SNR for each of the plurality of data streams; and

select the optimal MCS based on the post MEQ SNR.

20. The system of claim 19, wherein the one or more controllers is further configured to:

calculate a norm of each column of the estimated channel matrix;

project the column to a null space of space spanned by previous columns;

calculate a projection of each previous column to a null space of space spanned by remaining columns, if the post-MEQ SNR is directly used; and

store the post-MEQ SNR for the data stream.

23. The system of claim 11, wherein the at least one receiver of the beamformee is configured to receive the channel state information and sounding spatial mapping index set to the codebook from the beamformer if using explicit transmit beamforming, and

if using implicit transmit beamforming, the beamformer comprises at least one receiver that is configured to receive a sounding packet from the beamformee;

and

wherein the one or more controllers are configured to;

calculate an estimated reverse link channel matrix based on the received sounding packet at the beamformer;

transpose an estimated reverse link channel matrix to form an estimated forward link channel matrix; and

calculate the estimated composite channel matrix by multiplying the estimated forward link channel matrix and the codebook matrix.

24. A method for selecting a codebook, comprising:

receiving, by a beamformee, channel state information multiplied by a codebook, the codebook used to assign a steering matrix for transmit beamforming;

constructing, using at least one controller, an estimated channel matrix based on the received channel state information multiplied by the codebook, the codebook being stored in a memory;

selecting, using the at least one controller, a channel submatrix from the estimated channel matrix;

calculating, using the at least one controller, a selection matrix from the channel submatrix; and

assigning, using the at least one controller, a steering matrix based on the selection matrix.