System and Method for Improving the Robustness of Spatial Division Multiple Access Via Nulling

• US 20080039067A1
• Filed: 04/02/2007
• 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: Guo, Li, Jin, Hang
• Granted Patent: US 7,450,673 B2
• Time in Patent Office: Days
• US Class Current: 455/422.1
• CPC Class Codes: H01Q 3/2611 Means for null steering; Adaptive interference nulling
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0842 Weighted combining
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
• CPC Class Codes: H04B 7/0865 Independent weighting, i.e. weights based on own antenna reception parameters

Abstract

The present invention discloses a base transceiver station (BTS) equipped with a plurality of antennas for improving the robustness of spatial division multiple access via nullng. The BTS comprises of a first matrix module receiving a plurality of signals from one or more customer premises equipments (CPEs) through the plurality of antennas and producing correspondingly a first plurality of covariance matrices representing the plurality of signals, a second matrix module receiving the first plurality of covariance matrices and generating correspondingly a set of derivative spatial signature matrices representing the CPEs respectively, a third matrix module receiving the derivative spatial signature matrices and producing correspondingly a second plurality of covariance matrices representing interferences of the CPEs, and an eigenvector module generating a plurality of beamforming vectors for the CPEs from the plurality of derivative spatial signature matrices and the second plurality of covariance matrices.

Claims

1. A base transceiver station (BTS) equipped with a plurality of antennas, the BTS comprising:

a first matrix module receiving a plurality of signals from one or more customer premises equipments (CPEs) through the plurality of antennas and producing correspondingly a first plurality of covariance matrices representing the plurality of signals;

a second matrix module receiving the first plurality of covariance matrices and generating correspondingly a set of derivative spatial signature matrices representing the CPEs, respectively;

a third matrix module receiving the derivative spatial signature matrices and producing correspondingly a second plurality of covariance matrices representing interferences of the CPEs; and

an eigenvector module generating a plurality of beamforming vectors for the CPEs from the plurality of derivative spatial signature matrices and the second plurality of covariance matrices.

2. The BTS of claim 1 further comprising a memory module coupled to the first, second and third matrix modules and to the eigenvector module for storing and supplying the plurality of signals and the first and second plurality of covariance matrices.

3. The BTS of claim 1, wherein the first matrix module comprises:

a receiver module receiving the plurality of signals and forwarding the plurality of signals to the memory module; and

a covariance matrix module retrieving the plurality of signals from the memory module, producing the first plurality of covariance matrices and forwarding the first plurality of covariance matrices to the memory module.

4. The BTS of claim 1, wherein the second matrix module comprises:

a spatial signature module retrieving the first plurality of covariance matrices from the memory module and generating correspondingly a set of spatial signatures and forwarding the set of spatial signatures to the memory module; and

a derivative spatial signature matrix module retrieving the set of spatial signatures from the memory module and calculating correspondingly the set of derivative spatial signature matrices and forwarding the set of derivative spatial signature matrices to the memory module.

5. The BTS of claim 4, wherein the derivative spatial signature matrices are calculated based on the covariance matrix of receiving signals.

6. The BTS of claim 1, wherein the third matrix module produces one of the second plurality of covariance matrix for CPE k by retrieving one or more sets of derivative spatial signature matrices of the rest of the CPEs, sharing a communication channel, from the memory module and producing the covariance matrices of interference according to the following equation:

7. The BTS of claim 1, wherein the eigenvector module generates a beamforming weighting vector W^k of CPE k using the following eigenvalue matrix:

8. The BTS of claim 7, wherein W^k is the eigenvector corresponding to the largest eigenvalue of the matrix.

9. A base transceiver station (BTS) equipped with a plurality of antennas, the BTS comprising:

a first matrix module receiving a plurality of signals from one or more customer premises equipments (CPEs) through the plurality of antennas and producing correspondingly a first plurality of covariance matrices representing the plurality of signals;

a second matrix module receiving the first plurality of covariance matrices and generating correspondingly a set of derivative spatial signature matrices representing the CPEs respectively, wherein the second matrix module further comprises;

a transformation matrix module retrieving the first plurality of covariance matrices and generating correspondingly a set of transformation matrices, and

a derivative spatial signature matrix module calculating correspondingly the set of derivative spatial signature matrices from the set of transformation matrices;

a third matrix module receiving the derivative spatial signature matrices and producing correspondingly a second plurality of covariance matrices representing interferences of the CPEs; and

an eigenvector module generating a plurality of beamforming vectors for the CPEs from the plurality of derivative spatial signature matrices and the second plurality of covariance matrices.

10. The BTS of claim 9 further comprising a memory module coupled to the first, second and third matrix modules and to the eigenvector module for storing and supplying the plurality of signals and the first and second plurality of covariance matrices.

11. The BTS of claim 9, wherein the first matrix module comprises:

a receiver module receiving the plurality of signals and forwarding the plurality of signals to the memory module; and

a covariance matrix module retrieving the plurality of signals from the memory module, producing the first plurality of covariance matrices and forwarding the first plurality of covariance matrices to the memory module.

12. The BTS of claim 9, wherein the second matrix module produces a set of transformation matrices of one or more CPEs from a set of covariance matrices of receiving signals based on the following equations:

T_i=COV<sub>i−

1</sub>(COV_i)<sup>−

1</sup> and T_m=COV (COV_m)<sup>−

1</sup>, where iε

{1, . . . ,m−

1);

T_i is the i-th element of the set of transformation matrices;

COV_i is the i-th element;

COV is the last element of the set of covariance matrices of receiving signals.

13. The BTS of claim 9, wherein the derivative spatial signature matrix module calculates a set of derivative spatial signature matrices according to the following equation:

V_i=T_iCov, where iε

{1, . . . ,n) and n≦

m;

T_i is the i-th element of the set of transformation matrices;

COV is the last element of the set of covariance matrices of receiving signals.

14. The BTS of claim 9, wherein the third matrix module produces the covariance matrices of interference for CPE k according to the following equation:

15. The BTS of claim 9, wherein the eigenvector module generates a beamforming weighting vector W^k of CPE k using the following eigenvalue matrix:

16. A method to generate beamforming weighting vectors for spatial division multiple access (SDMA) via nulling, the method comprising:

generating a first plurality of covariance matrices from a plurality of signals of one or more customer premises equipments (CPEs) received by a plurality of antennas;

generating one or more sets of derivative spatial signature matrices of the CPEs from the first plurality of covariance matrices;

producing a second plurality of covariance matrices representing interferences of the CPEs from one or more sets of derivative spatial signature matrices; and

generating a plurality of beamforming vectors for the CPEs, respectively from the plurality of derivative spatial signature matrices and the second plurality of covariance matrix.

17. The method of claim 16, wherein the generating one or more sets of derivative spatial signature matrices comprises:

calculating one or more sets of spatial signatures of the CPEs from the first plurality of covariance matrix; and

generating the one or more sets of derivative spatial signature matrices of one or more CPEs from the one or more sets of spatial signatures.

18. The method of claim 16, wherein the second plurality of covariance matrices are produced according to the following equation:

19. The method of claim 16, wherein the plurality of beamforming weighting vectors are generated using the following eigenvalue matrix:

20. The method of claim 19, wherein each of the plurality of beamforming weighting vectors is an eigenvector corresponding to the largest eigenvalue of the equation.