Method and apparatus for multi-antenna transmission

• US 6,927,728 B2
• Filed: 03/13/2003
• Issued: 08/09/2005
• Est. Priority Date: 03/13/2003
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Zhuang, Xiangyang, Vook, Frederick W., Thomas, Timothy A.
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US10/387,727
• Publication Number:
  US 20040178954A1
• Time in Patent Office: 880 Days
• Field of Search: 342/377, 342/383, 375/347, 375/267
• US Class Current: 342/377
• CPC Class Codes: H04B 7/0417 Feedback systems
• CPC Class Codes: H04B 7/0617 for beam forming
• 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
• CPC Class Codes: H04B 7/066 Combined feedback for a number of channels, e.g. over several subcarriers like in orthogonal frequency division multiplexing [OFDM]
• CPC Class Codes: H04L 2025/03802 Signalling on the reverse channel
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/0248 Eigen-space methods
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 27/2626 Arrangements specific to the transmitter only
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 5/0044 allocation of payload

Abstract

In a multiple-input, multiple-output (MIMO) communication system, a method and apparatus for multi-antenna transmission. In accordance with the preferred embodiment of the present invention a reduced number of transmit weight matrices are fed back to the transmitter. Each transmit weight matrix is then applied to a plurality of subcarriers. Because each transmit weight matrix is applied to more than one subcarrier, the amount of weight matrixs being fed back to the transmitter is greatly reduced.

Claims

1. A method for multi-antenna transmission, the method comprising the steps of:

receiving a plurality of frequency subcarriers at a receiver, the plurality of frequency subcarriers being transmitted from a transmitter;

grouping the frequency subcarriers into a plurality of frequency subcarrier blocks, each frequency subcarrier block comprising a plurality K of frequency subcarriers; and

calculating for each frequency subcarrier block a single weighting matrix V_c, for use in a transmission of multi-antenna signal, wherein the single weighting matrix V_c is calculated based on a matrix channel frequency response between the transmitter and the receiver on the frequency subscriber block for which V_c is being calculated.

2. The method of claim 1 further comprising the step of:

transmitting the weighting matrices for the frequency subcarrier blocks to the transmitter.

3. The method of claim 1 wherein the step of calculating V_c comprises the step of choosing V_c to maximize:

$P_y=E<br><br>\left\{\frac{1}{K}<br><br>\underset{k=1}{\overset{K}{\sum <br><br>}}<br><br>Y^H<br><br>\left(k\right)<br><br>Y<br><br>\left(k\right)\right\}$

where

Y(k)=H(k)V_cs(k)+N(k),

H(k) is a matrix channel response between the transmitter and the receiver for a k^th subcarrier,

N(k) is received noise, and

E is an expectation operator.

4. The method of claim 1 wherein the step of calculating V_c comprises the step of choosing V_c to be a function of the eigenvectors of the quantity $R_{\mathrm{HK}}=\frac{1}{K}$

∑

k=1K⁢

HH⁡

(k)⁢

H⁡

(k)

where

H(k) is a matrix channel response between the transmitter and the receiver for a k^th subcarrier and Y(k)=H(k)V_cS(k)+N(k).

5. The method of claim 2 wherein the step of transmitting the weighting matrix to the transmitter comprises the step of transmitting the weighting matrix to the transmitter causing the transmitter to weight all frequency subcarriers within the frequency subcarrier block with the weighting matrix.

6. The method of claim 1 further comprising the steps of:

receiving, by the transmitter, the weighting matrix; and

weighting all frequency subcarriers within a frequency subcarrier block with the weighting matrix.

7. The method of claim 1 further comprising the steps of:

receiving by the transmitter, the weighting matrix for each frequency subcarrier block;

computing an interpolated transmit weight matrix for each frequency subcarrier based on the received weighting matrix for each of the frequency subcarrier blocks; and

weighting all frequency subcarriers with the interpolated transmit weight matrix.

8. The method of claim 1 wherein the step of receiving the plurality of frequency subcarriers comprises the step of receiving the plurality of frequency subcarriers within an Orthogonal Frequency Division Multiplexing (OFDM) communication system.

9. The method of claim 1 wherein the step of receiving the plurality of frequency subcarriers comprises the step of receiving a plurality of frequency subcarriers, each frequency subcarrier being transmitted on a differing frequency.

10. A method for multi-antenna transmission, the method comprising the steps of:

receiving a plurality of frequency subcarriers;

grouping the plurality of frequency subcarriers into a plurality of frequency subcarrier blocks, each frequency subcarrier block comprising a plurality K of frequency subcarriers;

calculating a single weighting matrix V_c for each of the plurality of frequency subcarrier blocks and for use in a transmission of a multi-antenna signal, wherein the single weighting matrix V_c is calculated based on a matrix channel frequency response between a transmitter and a receiver on the frequency subcarrier block for which V_c is being calculated; and

weighting all frequency subcarriers within the frequency subcarrier block with V_c.

11. The method of claim 10 wherein the step of calculating the single weighting matrix for the plurality of frequency subcarrier blocks comprises the step of choosing V_c to maximize:

$P_y=E<br><br>\left\{\frac{1}{K}<br><br>\underset{k=1}{\overset{K}{\sum <br><br>}}<br><br>Y^H<br><br>\left(k\right)<br><br>Y<br><br>\left(k\right)\right\}$

where

Y(k)=H(k)V_cs(k)+N(k),

H(k) is a matrix channel response between a transmitter and a receiver,

N(k) is received noise, and

E is an expectation operator.

12. The method of claim 10 wherein the step of calculating the single weighting matrix for each of the plurality of frequency subcarrier blocks comprises the step of choosing V_c to be the eigenvector corresponding to the largest eigenvalue of the quantity $R_{\mathrm{HK}}=\frac{1}{K}$

∑

k=1K⁢

HH⁡

(k)⁢

H⁡

(k)

where

H(k) is a matrix channel response between a transmitter and a receiver for a k^th subcarrier.

13. The method of claim 10 wherein the step of receiving the plurality of frequency subcarriers comprises the step of receiving the plurality of frequency subcarriers within an Orthogonal Frequency Division Multiplexing (OFDM) communication system.

14. The method of claim 10 wherein the step of receiving the plurality of frequency subcarriers comprises the step of receiving a plurality of frequency subcarriers, each frequency subcarrier being transmitted on a differing frequency.

15. The method of claim 10 wherein the step of weighting all frequency subcarriers comprises the steps of:

computing interpolated transmit weight matrices based on the set of weighting matrices Vc for each frequency subcarrier block; and

weighting all frequency subcarriers with the interpolated transmit weight matrices.

16. An apparatus comprising:

an adaptive weight controller, the adaptive weight controller having as an input, a plurality of frequency subcarriers and outputting a plurality of weighting matrices V_c, wherein;

a single weighting matrix is calculated for a frequency subcarrier block comprising a plurality K of frequency subcarriers, wherein the single weighting matrix is calculated based on a matrix channel frequency response between a transmitter and a receiver on the frequency subcarrier block; and

a transmitter adapted to transmit a multi-antenna signal that is formed based on the single weighting matrix V_c for each frequency subcarrier block.

17. The apparatus of claim 16 wherein the adaptive weight controller chooses V_c to maximize:

$P_y=E<br><br>\left\{\frac{1}{K}<br><br>\underset{k=1}{\overset{K}{\sum <br><br>}}<br><br>Y^H<br><br>\left(k\right)<br><br>Y<br><br>\left(k\right)\right\}$

where

Y(k)=H(k)V_cs(k)+N(k),

H(k) is a matrix channel response between the transmitter and the receiver on a k^th frequency subcarrier,

N(k) is received noise, and

E is an expectation operator.

18. The apparatus of claim 16 wherein the adaptive weight controller chooses V_c to be the eigenvector corresponding to the largest eigenvalue of the quantity $R_{\mathrm{HK}}=\frac{1}{K}$

∑

k=1K⁢

 

⁢

HH⁡

(k)⁢

H⁡

(k)

where

H(k) is a matrix channel response between a transmitter and a receiver for a k^th frequency subcarrier.

19. The apparatus of claim 16 wherein each of the plurality of frequency subcarriers are transmitted on a different frequency.