SYSTEM AND METHOD FOR IMPROVING THE ROBUSTNESS OF SPATIAL DIVISION MULTIPLE ACCESS VIA NULLING

US 20090004988A1
Filed: 09/10/2008
Published: 01/01/2009
Est. Priority Date: 08/10/2006
Status: Active Grant

First Claim

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1. An apparatus comprising:

a plurality of antennas;

a receiver coupled to the plurality of antennas, wherein the receiver is configured to generate a plurality of receive signals associated with transmissions from a plurality of remote devices that are detected by the plurality of antennas;

at least one processor module that is configured to;

produce a plurality of first covariance matrices from the plurality of receive signals;

generate a plurality of derivative spatial signature matrices for the plurality of remote devices from the plurality of first covariance matrices;

produce a plurality of second covariance matrices from the derivative spatial signature matrices, wherein the plurality of second covariance matrices represent interference associated with the plurality of remote devices; and

generate a plurality of beamforming vectors each for a respective one of the remote devices from the plurality of derivative spatial signature matrices and the plurality of second covariance matrices.

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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 nulling. 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.

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16 Claims

1. An apparatus comprising:
- a plurality of antennas;
  
  a receiver coupled to the plurality of antennas, wherein the receiver is configured to generate a plurality of receive signals associated with transmissions from a plurality of remote devices that are detected by the plurality of antennas;
  
  at least one processor module that is configured to;
  
  produce a plurality of first covariance matrices from the plurality of receive signals;
  
  generate a plurality of derivative spatial signature matrices for the plurality of remote devices from the plurality of first covariance matrices;
  
  produce a plurality of second covariance matrices from the derivative spatial signature matrices, wherein the plurality of second covariance matrices represent interference associated with the plurality of remote devices; and
  
  generate a plurality of beamforming vectors each for a respective one of the remote devices from the plurality of derivative spatial signature matrices and the plurality of second covariance matrices.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
- - 2. The apparatus of claim 1, wherein the at least one processor module is configured to produce one second covariance matrices for a particular remote device k by computing:
    - $\sum_{j = 1, j \neq k}^{L} (\frac{1}{s^{j}} \sum_{i = 1}^{s^{j}} R_{i}^{j} R_{i}^{j^{H}}),$ where R_i^jis the derivative spatial signature matrix for remote device j, R_i^j^Hthe conjugate transpose of matrix R_i^j, L represents a number of remote devices sharing a communication channel, and S^jis the number of derivative spatial signature matrices for remote device j.
  - 3. The apparatus of claim 2, wherein the at least one processor module is configured to generate a beamforming vector W^kfor remote device k using the following eigenvalue matrix:
    - ${(\sum_{j = 1, j \neq k}^{L} (\frac{1}{s^{j}} \sum_{i = 1}^{s^{j}} R_{i}^{j} R_{i}^{j^{H}}) + σ_{n}^{2} I)}^{- 1} (\sum_{i = 1}^{s^{k}} R_{i}^{k} R_{i}^{k^{H}})),$ wherein the beamforming vector W^kis the eigenvector corresponding to the largest eigenvalue of the eigenvalue matrix.
  - 4. The apparatus of claim 1, wherein the at least one processor module is further configured to generate a plurality of transformation matrices from the first plurality of covariance matrices, and wherein the processor generates the derivative spatial signature matrices based further on the plurality of transformation matrices.
  - 5. The apparatus of claim 4, wherein the at least one processor module is further configured to generate a plurality of transformation matrices for one or more remote devices from a plurality of the plurality of first covariance matrices associated with received signals according to the following equations:
    - T_i=COV_i+1(COV_i)^−
      
      1and T_m=COV(COV_m)^−
      
      1, where iε
      
      {1, L, m−
      
      1);
      
      T_iis the i-th element of the plurality of transformation matrices;
      
      COV_iis the i-th element, COV is the last element of the plurality of first covariance matrices.
  - 6. The apparatus of claim 5, wherein the at least one processor module is configured to calculate the plurality of derivative spatial signature matrices according to the following equations:
    - V_i=T_iCov, where iε
      
      {1, . . . , n) and n≦
      
      m, T_iis the i-th element of the set of transformation matrices; and
      
      COV is the last element of the plurality of first covariance matrices.
  - 7. The apparatus of claim 6, wherein the at least one processor module is configured to compute second covariance matrices for remote device k according to the following equation:
    - $\sum_{j = 1, j \neq k}^{L} \sum_{i = 1}^{n} R_{i}^{j},$ where iε
      
      {1, . . . , n), R_i^jis the i-th element of the plurality of derivative spatial signature matrices of remote device j and L represents the number of remote devices sharing a communication channel.
  - 8. The apparatus of claim 7, wherein the at least one processor module generates a beamforming vector W^kfor remote device k using the following eigenvalue matrix:
    - ${[\sum_{j = 1, j \neq k}^{L} \frac{1}{m} (\sum_{i = 1}^{m} R_{i}^{j}) + σ_{n}^{2} I]}^{- 1} (\sum_{i = 1}^{m} R_{i}^{k}) .$

9. A method comprising:
- receiving at a plurality of antennas of a first device signals associated with transmissions from a plurality of remote devices;
  
  computing a plurality of first covariance matrices from the plurality of receive signals;
  
  generating a plurality of derivative spatial signature matrices for the plurality of remote devices from plurality of first covariance matrices;
  
  producing a plurality of second covariance matrices from the derivative spatial signature matrices, wherein the plurality of second covariance matrices represent interference associated with the plurality of remote devices; and
  
  generating a plurality of beamforming vectors each for a respective one of the remote devices from the plurality of derivative spatial signature matrices and the plurality of second covariance matrices.
- View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
- - 10. The method of claim 9, wherein producing the plurality of second covariance matrices comprises producing one second covariance matrix for a particular remote device k by computing $\sum$
    - j = 1 , j ≠
      
      k L 
      
      
      
      ( 1 s j 
      
      ∑
      
      i = 1 s j 
      
      
      
      R i j 
      
      R i j H ) , where R_i^jis the derivative spatial signature matrix for remote device j, R_i^j^His the conjugate transpose of matrix R_i^j, L represents a number of remote devices sharing a communication channel, and S^jis the number of derivative spatial signature matrices for remote device j.
  - 11. The apparatus of claim 10, wherein generating the plurality of beamforming vectors comprises generating a beamforming vector W^kfor remote device k using the following eigenvalue matrix:
    - ${(\sum_{j = 1, j \neq k}^{L} (\frac{1}{s^{j}} \sum_{i = 1}^{s^{j}} R_{i}^{j} R_{i}^{j^{H}}) + σ_{n}^{2} I)}^{- 1} (\sum_{i = 1}^{s^{k}} R_{i}^{k} R_{i}^{k^{H}})),$ wherein the beamforming vector W^kis the eigenvector corresponding to the largest eigenvalue of the eigenvalue matrix.
  - 12. The method of claim 9, and further comprising generating a plurality of transformation matrices from the first plurality of covariance matrices, and wherein the derivative spatial signature matrices are generated based further on the plurality of transformation matrices.
  - 13. The method of claim 12, wherein generating the plurality of transformation matrices comprises generating a plurality of transformation matrices for one or more remote devices from a plurality of the plurality of first covariance matrices associated with received signals according to the following equations:
    - T_i=COV_i+1(COV_i)^−
      
      1and T_m=COV(COV_m)^−
      
      1, where iε
      
      {1, L, m−
      
      1);
      
      T_iis the i-th element of the plurality of transformation matrices;
      
      COV_iis the i-th element;
      
      COV is the last element of the plurality of first covariance matrices.
  - 14. The method of claim 13, wherein generating the plurality of derivative spatial signature matrices comprises is made according to the following equations:
    - V_i=T_iCov, where iε
      
      {1, . . . , n) and n≦
      
      m;
      
      T_iis the i-th element of the set of transformation matrices; and
      
      COV is the last element of the plurality of first covariance matrices.
  - 15. The method of claim 14, wherein generating the plurality of second covariance matrices comprises computing second covariance matrices for remote device k according to the following equation:
    - $\sum_{j = 1, j \neq k}^{L} \sum_{i = 1}^{n} R_{i}^{j},$ where iε
      
      {1, . . . , n), R_i^jis the i-th element of the plurality of derivative spatial signature matrices of remote device j and L represents the number of remote devices sharing a communication channel.
  - 16. The method of claim 15, wherein generating the plurality of beamforming vectors comprises generating a beamforming vector W^kfor remote device k using the following eigenvalue matrix:
    - ${[\sum_{j = 1, j \neq k}^{L} \frac{1}{m} (\sum_{i = 1}^{m} R_{i}^{j}) + σ_{n}^{2} I]}^{- 1} (\sum_{i = 1}^{m} R_{i}^{k}) .$

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Current Assignee
Cisco Technology, Inc. (Cisco Systems, Inc.)
Original Assignee
Cisco Technology, Inc. (Cisco Systems, Inc.)
Inventors
Guo, Li, Jin, Hang

Granted Patent

US 7,801,239 B2
Time in Patent Office

Days
Field of Search
US Class Current

455/272
CPC Class Codes

H01Q 3/2611   Means for null steering; Ad...

H04B 7/0617   for beam forming

H04B 7/0842   Weighted combining

H04B 7/086   using weights depending on ...

H04B 7/0865   Independent weighting, i.e....

SYSTEM AND METHOD FOR IMPROVING THE ROBUSTNESS OF SPATIAL DIVISION MULTIPLE ACCESS VIA NULLING

First Claim

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SYSTEM AND METHOD FOR IMPROVING THE ROBUSTNESS OF SPATIAL DIVISION MULTIPLE ACCESS VIA NULLING

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16 Claims

Specification

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