Method and system for improving robustness of interference nulling for antenna arrays

• US 20080039146A1
• Filed: 01/18/2007
• Published: 02/14/2008
• Est. Priority Date: 08/10/2006
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Navini Networks, Inc. (Cisco Systems, Inc.)
• Inventors: Jin, Hang
• Granted Patent: US 8,000,418 B2
• Time in Patent Office: Days
• US Class Current: 455/562.1
• CPC Class Codes: H01Q 1/246 specially adapted for base stations
• CPC Class Codes: H01Q 3/2617 Array of identical elements

Abstract

The present invention discloses a method and system for improving the robustness of interference nulling for antenna arrays in a wireless communication network. The method is comprised of generating a first interference spatial signature from an interference signal matrix received by the antenna array, deriving a second interference spatial signature from the first interference spatial signature, calculating a covariance matrix from the second interference spatial signature, and generating a beamforming weighting vector from the covariance matrix.

Claims

1. A method for generating a beamforming weighting vector in a wireless communication network with an antenna array, the method comprising:

generating a first interference spatial signature from an interference signal matrix received by the antenna array;

deriving a second interference spatial signature from the first interference spatial signature;

calculating a covariance matrix from the second interference spatial signature; and

generating the beamforming weighting vector from the covariance matrix.

2. A method of claim 1, wherein the deriving the second interference spatial signature further comprising:

generating two or more second vectors, each of which is a difference between two consecutive first vectors of the interference signal matrix;

calculating two or more norms of the two or more second vectors and an interference spatial signature norm, which is the average of the norms;

generating at least one set of two or more third vectors of interference derivative spatial signatures by employing vector operations and forming a first matrix of two or more third vectors which meet the following criteria;

the norm of each third vector equals one;

the norm of the difference between each third vector and one of the first vectors equals the interference spatial signature norm; and

the third vectors are most evenly spread over the two-dimensional space.

3. The method of claim 2, wherein a set of the second vectors has one fewer element than a set of the first vectors.

4. The method of claim 2, wherein one of the first vectors is the last interference spatial signature calculated by a base transceiver station (BTS).

5. The method of claim 2, the set of third vectors that are most evenly spread over the two-dimensional space has the maximum Euclidian distance between each vector and the rest in the set, which is calculated according to the following equation:

6. A method for generating a beamforming weighting vector in a wireless communication network with an antenna array, the method comprising:

calculating two or more first vectors, which is the interference spatial signatures of a customer'"'"'s premises equipment;

generating two or more first matrices, each of which is an interference transformation matrix of a set of two first vectors and is the product of one of the first vector and the conjugate-transpose of the second vector;

generating two or more second vectors of interference derivative spatial signatures by applying the two or more first matrices to one of the first vectors and forming a second matrix of the two or more second vectors; and

creating a third matrix, which is the interference covariance matrix of the second matrix, and a beamforming weighting vector that widens the nulling angle of an antenna beam pattern.

7. The method of claim 6, wherein the two or more first vectors are interference spatial signatures calculated from receiving signals over time.

8. The method of claim 6, wherein one of the first vectors is the last interference spatial signature calculated by a base transceiver station.

9. The method of claim 6, wherein each of the two or more first matrices is the product of two consecutive vectors.

10. A wireless communication network system comprising:

a receiver module with a plurality of antennas to collect signals from a customer premises equipment (CPE) over time;

a first vector operation module configured to calculate one or more interference spatial signatures of the CPE to form a first plurality of vectors;

a memory module to collect the first plurality of vectors;

a second vector operation module to calculate one or more interference derivative spatial signatures from the two or more of the first plurality of vectors to form a second plurality of vectors; and

a signal processing module to form a first matrix of interference spatial signatures by using the second plurality of vectors and to compute a third vector,

wherein a predetermined antenna beam pattern is generated from the third vector by the signal processing module.

11. The system of claim 10, wherein the second vector operation module generates the two or more second vectors, each vector in the second plurality of vectors is a difference between two consecutive vectors of the first plurality of vectors.

12. The system of claim 10, wherein the second vector operation module is further configured to calculates a first plurality of norms from the second plurality of vectors, and computes an interference spatial signature norm from the average of the first plurality of norms.

13. The system of claim 10, wherein the third vector is a beamforming weighting vector.