Method and apparatus for reduced rank channel estimation in a communications system

• US 6,907,270 B1
• Filed: 10/23/2000
• Issued: 06/14/2005
• Est. Priority Date: 10/23/2000
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Blanz, Josef J.
• Primary Examiner(s): Hudspeth, David
• Assistant Examiner(s): NGUYEN, DAVID Q
• Application Number:
  US09/694,432
• Time in Patent Office: 1,695 Days
• Field of Search: 455/562, 455/67.1, 342/360, 342/455, 342/445, 342/412, 342/442, 342/434, 342/124, 342/222.1, 342/383, 320/210, 320/242, 320/281, 320/329, 375/341
• US Class Current: 455/562.1
• CPC Class Codes: H04B 7/10 Polarisation diversity; Directional diversity
• CPC Class Codes: H04L 25/0248 Eigen-space methods

Abstract

A method and apparatus for estimating a communication channel in a wireless communication system having multiple transmitter antennas using reduced rank estimation. The method exploits redundant and/or a priori knowledge within a system to simplify the estimation calculations. In one embodiment, a covariance matrix is calculated and analyzed to determine if the channel parameters may be reduced for channel estimation. If not, all parameters are used, otherwise a reduced rank matrix is used for the calculation.

Claims

1. A wireless communication apparatus, comprising:

a correlator operative to estimate a covariance matrix representing a link with a transmitter based on signals received from the transmitter;

a rank analysis unit coupled to the correlator and operative to estimate a rank of the covariance matrix; and

a channel estimation unit coupled to the rank analysis unit and operative to generate a reduced rank channel estimate.

2. The apparatus of claim 1, wherein the covariance matrix represents a plurality of impulse responses between the apparatus and the transmitter.

3. The apparatus of claim 1, wherein the correlator is operative to determine a correlation of at least two channels.

4. The apparatus of claim 3, wherein the rank analysis unit is operative to determine an eigenvalue corresponding to the covariance matrix.

5. The apparatus of claim 4, wherein the rank analysis unit is operative to compare the estimated rank of the covariance matrix to a predetermined full value.

8. An apparatus as in claim 1, wherein the correlator is operative to estimate delays in signals received.

9. An apparatus as in claim 1, wherein the rank analysis unit is operative to compare the rank of the covariance matrix to a maximum rank.

10. An apparatus as in claim 9, wherein if the rank of the covariance matrix is less than the maximum rank, the channel estimation means is operative to generate a full rank channel estimate.

11. A method as in claim 3, further comprising:

determining if the rank of the covariance matrix is less than a maximum rank; and

if the rank is less then N×

M performing an extraction of a subspace of the matrix.

12. A method as in claim 11, wherein estimating a covariance matrix comprises:

determining a matrix describing parametric relations of the link.

13. A method as in claim 12, further comprising:

deriving channel impulse responses for each channel based on the extracted subspace of the matrix; and

demodulating a received signal using the channel impulse responses.

6. A wireless communication apparatus, comprising:

a correlator means operative to estimate a covariance matrix representing a link with a transmitter based on signals received from the transmitter;

a rank analysis means coupled to the correlator means and operative to estimate the rank of the covariance matrix; and

a channel estimation means coupled to the rank analysis means and operative to generate a reduced rank channel estimate.

7. A method in a wireless communication system, comprising:

estimating a covariance matrix representing a link with a transmitter based on signals received from the transmitter;

estimating a rank of the covariance matrix; and

generating a reduced rank channel estimate.

14. A wireless communication apparatus, comprising:

means for estimating a covariance matrix representing a link with a transmitter based on signals received from the transmitter;

means for estimating a rank of the covariance matrix; and

means for generating a reduced rank channel estimate.

15. A wireless communication apparatus as in claim 14, further comprising:

means for determining if the rank of the covariance matrix is less than a maximum rank; and

means for performing an extraction of a subspace of the matrix if the rank is less then the maximum rank.

16. A wireless communication apparatus as in claim 15, wherein the means for estimating a covariance matrix comprises:

means for determining a matrix describing parametric relations of the link.

17. A wireless communication apparatus as in claim 16, further comprising:

means for deriving channel impulse responses for each channel based on the extracted subspace of the matrix; and

means for demodulating a received signal using the channel impulse responses.