Orthogonalization and directional filtering

• US 7,260,506 B2
• Filed: 10/06/2004
• Issued: 08/21/2007
• Est. Priority Date: 11/19/2001
• Status: Expired due to Fees

• Current Assignee: III Holdings 1, LLC
• Original Assignee: TensorComm, Inc. (Rambus Inc.)
• Inventors: Thomas, John K., Narayan, Anand P., Olson, Eric B.
• Primary Examiner(s): Tsai, Carol S. W.
• Application Number:
  US10/959,618
• Publication Number:
  US 20050075845A1
• Time in Patent Office: 1,049 Days
• Field of Search: 702/189, 702/190, 702/131, 702/193, 702/194, 702/195, 702/196, 375/148, 375/144, 375/346
• US Class Current: 702/189
• CPC Class Codes: G01S 19/21 Interference related issues ; Issues related to cross-correlation, spoofing or other methods of denial of service
• CPC Class Codes: H04B 1/7105 Joint detection techniques, e.g. linear detectors
• CPC Class Codes: H04B 2201/70715 with application-specific features

Abstract

Systems and methods are provided for directionally filtering signals by projecting a received signal onto a subspace substantially orthogonal to selected interfering signals. The received signal typically comprises at least one signal of interest, at least one selected interfering signal, and noise. The received signal may further comprise other signals, including non-selected interfering signals. The projection of the received signal results in substantially no contribution from the selected interference signals on the signal of interest. For example, substantially no residual energy of the selected interference signals remains as an influence on the signal of interest. In one embodiment, a system generates a converted matrix having a substantially orthogonal set of vectors. Each vector may represent one or more selected interfering signals. The vectors may comprise code characteristics of the selected interfering signals. A directional filter uses the matrix to perform the projection. As such, the filter may be configured to selectively “filter out” the interfering signals by suppressing the effects of the signals based on their code characteristics.

Claims

1. A system configured for processing a received signal comprising a signal of interest and at least one interferer, the system comprising:

a matrix generator configured for generating a matrix having a plurality of vectors, wherein each of the plurality of vectors comprises elements from the at least one interferer; and

a matrix converter communicatively coupled to the matrix generator, wherein the matrix converter is configured for generating a substantially orthogonal vector set from the plurality of vectors to convert the matrix for producing a converted matrix and for computing a portion of a cancellation operator from the converted matrix, the cancellation operator configurable for operating on the received signal to produce an interference-cancelled signal having a reduced contribution from the at least one interferer.

2. The system of claim 1, wherein the portion of the cancellation operator computed by the matrix converter comprises the form:

(U^TU)<sup>−

1</sup>,

wherein U is the converted said matrix and U^T is a transpose of the converted said matrix.

3. The system of claim 2, wherein the cancellation operator comprises the form:

P_U^⊥

=I−

U(U^TU)<sup>−

1</sup>U^T,

wherein P_{U ⊥}

is the cancellation operator and I is an identity matrix.

4. The system of claim 1, wherein the matrix converter comprises a comparator configured for selecting at least one of the plurality of vectors having vector-derived values within the portion of the cancellation operator exceeding a threshold value, the matrix converter producing a plurality of selected vectors, wherein the matrix converter is further configured for generating the substantially orthogonal vector set from the plurality of selected vectors.

5. The system of claim 1, wherein the substantially orthogonal vector set is generated according to the form:

${\underset{\_}{u}}_n={\underset{\_}{s}}_n-\underset{j=1}{\overset{n-1}{\sum <br><br>}}<br><br>{{\underset{\_}{u}}_j<br><br>\left({\underset{\_}{u}}_j^T<br><br>{\underset{\_}{u}}_j\right)}^{-1}<br><br>{\underset{\_}{u}}_j^T<br><br>{\underset{\_}{s}}_n,$

wherein n is an integer greater than 1, s is a vector of the matrix and u is an orthogonalized vector of the converted matrix.

6. The system of claim 5, wherein the matrix generator comprises a storage unit configured for storing computed values of u_j^Tu_j.

7. The system of claim 5, wherein the computed values of u_j^Tu_j are used to generate values of the portion of the cancellation operator according to:

σ

_j=(u_j^Tu_j)<sup>−

1</sup>,

wherein σ

_j is one of the values of the portion of cancellation operator and wherein the storage unit is further configured for storing computed values of σ

_j.

8. The system of claim 7, wherein the values of σ

_j are compared to a threshold to determine use of the vectors u_j in construction of the converted matrix.

9. A processing engine adapted for use in a receiver configured for processing a received signal comprising a signal of interest and at least one interferer, the processing engine comprising:

a matrix generator configured for generating a matrix having a plurality of vectors, wherein each of the plurality of vectors comprises elements from the at least one interferer;

a matrix converter communicatively coupled to the matrix generator, wherein the matrix converter is configured for generating a substantially orthogonal vector set from the plurality of vectors to generate a converted matrix and for computing a portion of a cancellation operator from the converted matrix; and

a processor configured for processing the portion of the cancellation operator to generate the cancellation operator, the cancellation operator configurable for operating on the received signal to produce an interference-cancelled signal having a reduced contribution from the at least one interferer.

10. The processing engine of claim 9, wherein the portion of the cancellation operator computed by the matrix converter comprises the form:

(U^TU)<sup>−

1</sup>,

wherein U is the converted matrix and U^T is a transpose of the converted matrix.

11. The processing engine of claim 10, wherein the cancellation operator comprises the form:

P_U^⊥

=I−

U(U^TU)<sup>−

1</sup>U^T,

wherein P_U^⊥

is the cancellation operator and I is an identity matrix.

12. The processing engine of claim 9, further comprising an applicator configured for applying the cancellation operator to an input signal to substantially cancel the at least one interferer.

13. The processing engine of claim 9, wherein the matrix converter comprises a comparator configured for selecting at least one vector having vector-derived values within the portion of the cancellation operator exceeding a threshold value, the comparator producing a plurality of selected vectors, wherein the matrix converter is further configured for generating the substantially orthogonal vector set from said plurality of vectors.

14. The processing engine of claim 9, wherein the substantially orthogonal vector set is generated according to the form:

${\underset{\_}{u}}_n={\underset{\_}{s}}_n-\underset{j=1}{\overset{n-1}{\sum <br><br>}}<br><br>{{\underset{\_}{u}}_j<br><br>\left({\underset{\_}{u}}_j^T<br><br>{\underset{\_}{u}}_j\right)}^{-1}<br><br>{\underset{\_}{u}}_j^T<br><br>{\underset{\_}{s}}_n,$

wherein n is an integer greater than 1, s is a vector of the matrix and u is an orthogonalized vector of the converted matrix, and wherein the matrix is an interference matrix S.

15. The processing engine of claim 14, wherein the matrix generator comprises a storage unit configured for storing computed values of u_j^Tu_j.

16. The processing engine of claim 14, wherein the computed values of u_jTu_j are used to generate values of the portion of the cancellation operator according to:

σ

_j=(u_j^Tu_j)<sup>−

1</sup>,

wherein σ

_j is one of the values of the portion of cancellation operator and wherein the matrix generator comprises a storage unit configured for storing computed values of σ

_j.

17. The processing engine of claim 16, wherein the values of σ

_j are compared to a threshold to determine use of the vectors U_j in construction of the converted matrix.

18. The processing engine of claim 9, wherein the receiver is configurable with at least one of a base station and a handset.

19. A method for processing a received signal, comprising:

providing for generating a plurality of vectors such that each of the plurality of vectors comprises elements from one or more interferers in the received signal;

providing for generating a substantially orthogonal vector set from the plurality of vectors;

providing for computing a portion of a cancellation operator in response to generating the substantially orthogonal vector set; and

providing for using the portion of the cancellation operator to compute the cancellation operator, the cancellation operator configurable for operating on the received signal to produce an interference-cancelled signal having a reduced contribution from the one or more interferers.

20. The method of claim 19, further comprising providing for substantially canceling the one or more interferers using the cancellation operator.

21. The method of claim 20, wherein providing for substantially canceling comprises providing for applying the cancellation operator to an input signal to substantially cancel the one or more interferers comprised therewith.

22. The method of claim 19, wherein providing for computing comprises providing for computing the portion of the cancellation operator according to the form:

(U^TU)<sup>−

1</sup>,

wherein U is a matrix comprising the substantially orthogonal vector set of said plurality of vectors and U^T is a transpose of the matrix.

23. The method of claim 22, further comprising providing for computing the cancellation operator according to the form:

P_U^⊥

=I−

U(U^TU)<sup>−

1</sup>U^T,

wherein P_U^⊥

is the cancellation operator and I is an identity matrix.

24. The method of claim 19, further comprising providing for detecting vector-derived values exceeding a threshold value within the portion of the cancellation operator.

25. The method of claim 24, further comprising providing for selecting at least one of the plurality of vectors having vector-derived values that exceed the threshold value for producing a plurality of selected vectors, and providing for generating the substantially orthogonal vector set from said plurality of selected vectors.

26. The method of claim 19, wherein providing for generating the substantially orthogonal vector set comprises providing for generating a vector u_n by removing components of a vector s_n that lie in a direction of vectors u₁, . . . , u_n-1, wherein n is an integer greater than 1.

27. The method of claim 26, wherein providing for generating the substantially orthogonal vector set comprises providing for generating the substantially orthogonal vector set according to the form:

${\underset{\_}{u}}_n={\underset{\_}{s}}_n-\underset{j=1}{\overset{n-1}{\sum <br><br>}}<br><br>{{\underset{\_}{u}}_j<br><br>\left({\underset{\_}{u}}_j^T<br><br>{\underset{\_}{u}}_j\right)}^{-1}<br><br>{\underset{\_}{u}}_j^T<br><br>{\underset{\_}{s}}_n,$

wherein s is a vector of the plurality of the vectors and u is a vector of the substantially orthogonal vector set.

28. The method of claim 27, further comprising providing for storing computed values of u_j^Tu_j.

29. The method of claim 27, further comprising:

providing for computing the values of σ

wherein computed values of σ

comprise the form σ

_j=(u_j^Tu_j)<sup>−

1</sup>, wherein σ

_j is one of the values of the portion of the cancellation operator; and

providing for storing the computed values of σ

.

30. The method of claim 29, further comprising providing for comparing the values of σ

_j to a threshold value to determine use of the vectors u_j in construction of the portion of the cancellation operator.

61. A digital computer system programmed to perform the method of claim 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 49, 50, 51, or 54.

62. A computer-readable medium storing a computer program implementing the method of claim 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 49, 50, 51, or 54.

31. A system configured for processing a received signal comprising a signal of interest and at least one interferer, the system comprising:

means for generating a plurality of vectors such that each of the plurality of vectors comprises elements from the at least one interferer;

means for generating a substantially orthogonal vector set from the plurality of vectors;

means for generating a matrix from said substantially orthogonal vector set;

means for computing a portion of a cancellation operator in response to generating the substantially orthogonal vector set; and

means for using the portion of the cancellation operator to compute the cancellation operator, the cancellation operator configurable for operating on the received signal to produce an interference-cancelled signal having a reduced contribution from the at least one interferer.

32. The system of claim 31, further comprising means for substantially canceling the at least one interferer using the cancellation operator.

33. The system of claim 32, wherein the means for substantially canceling comprises means for applying the cancellation operator to an input signal to substantially cancel the at least one interferer comprised therewith.

34. The system of claim 31, wherein the means for computing comprises means for computing the portion of the cancellation operator according to the form:

(U^TU)<sup>−

1</sup>,

wherein U is a matrix comprising the substantially orthogonal vector set and U^T is a transpose of the matrix.

35. The system of claim 34, further comprising means for computing the cancellation operator according to the form:

P_U^⊥

=I−

U(U^TU)<sup>−

1</sup>U^T,

wherein P_U^⊥

is the cancellation operator and I is an identity matrix.

36. The system of claim 31, further comprising means for detecting vector-derived values exceeding a threshold value while computing the portion of the cancellation operator.

37. The system of claim 36, further comprising means for selecting a plurality of the plurality of vectors having vector-derived values that exceed the threshold value for producing a plurality of selected vectors, and means for generating the substantially orthogonal vector set from said plurality of selected vectors.

38. The system of claim 37, wherein the vector-derived values comprise the form σ

_j=(u_j^Tu_j)<sup>−

1</sup>, wherein σ

_j is one of the values of the portion of the cancellation operator and wherein u_j is one vector of the orthogonal vector set.

39. The system of claim 38, wherein the values of σ

_j are compared to the threshold value to determine use of the vectors u_j in construction of the portion of the cancellation operator.

40. The system of claim 31, wherein the means for generating the substantially orthogonal vector set comprises means for generating a vector u_n by removing components of a vector s_n that lie in a direction of vectors u₁, . . . , u_n-1, wherein n is an integer greater than 1.

41. The system of claim 40, wherein the means for generating the substantially orthogonal vector set comprises means for generating the substantially orthogonal vector set according to the form:

${\underset{\_}{u}}_n={\underset{\_}{s}}_n-\underset{j=1}{\overset{n-1}{\sum <br><br>}}<br><br>{{\underset{\_}{u}}_j<br><br>\left({\underset{\_}{u}}_j^T<br><br>{\underset{\_}{u}}_j\right)}^{-1}<br><br>{\underset{\_}{u}}_j^T<br><br>{\underset{\_}{s}}_n,$

wherein s is a vector of the plurality of the vectors and u is a vector of the substantially orthogonal vector set.

42. The system of claim 41, further comprising means for storing computed values of u_j^Tu_j.

43. The system of claim 41, further comprising means for storing computed values of σ

_j, wherein σ

_j=(u_j^Tu_j)^{31 1}.

44. A system configured for processing a received signal comprising a signal of interest and at least one interfering signal, the system comprising:

a matrix having a substantially orthogonal vector set comprising a plurality of vectors, the substantially orthogonal vector set being generated according to the form;

${\underset{\_}{u}}_n={\underset{\_}{s}}_n-\underset{j=1}{\overset{n-1}{\sum <br><br>}}<br><br>{{\underset{\_}{u}}_j<br><br>\left({\underset{\_}{u}}_j^T<br><br>{\underset{\_}{u}}_j\right)}^{-1}<br><br>{\underset{\_}{u}}_j^T<br><br>{\underset{\_}{s}}_n,$

wherein n is an integer greater than 1, s is a vector of the matrix and u is an orthogonalized vector of the converted said matrix, wherein each vector of the substantially orthogonal vector set represents the at least one interfering signal; and

a directional filter configured for using the matrix to project a the received signal onto a subspace substantially orthogonal to the substantially orthogonal vector set for producing an interference-cancelled signal having a reduced contribution of the at least one interfering signal.

45. The system of claim 44, further comprising a matrix converter configured for computing a portion of a cancellation operator according to the form:

(U^TU)<sup>−

1</sup>,

wherein U is the matrix and U^T is a transpose of the matrix.

46. The system of claim 45, wherein the cancellation operator comprises the form:

P_U^⊥

=I−

U(U^TU)<sup>−

1</sup>U^T,

wherein P_U^⊥

is the cancellation operator and I is an identity matrix.

47. The system of claim 44, wherein the matrix generator comprises a storage unit configured for storing computed values of U_j^Tu_j.

48. The system of claim 44, wherein the computed values of u_j^Tu_j are used to generate values of the portion of the cancellation operator according to:

σ

_j=(u_j^Tu_j),

wherein σ

_j is one of the values of the portion of the cancellation operator and wherein the matrix generator comprises a storage unit configured for storing computed values of σ

_j.

57. The receiver of claim 45, wherein the cancellation operator comprises the form:

P_U^⊥

=I−

U(U^TU)<sup>−

1</sup>U^T,

wherein P_U^⊥

is the cancellation operator and I is an identity matrix.

49. A method for cancelling at least one interfering signal in a received signal, comprising:

providing for generating a substantially orthogonal set of vectors according to the form;

${\underset{\_}{u}}_n={\underset{\_}{s}}_n-\underset{j=1}{\overset{n-1}{\sum <br><br>}}<br><br>{{\underset{\_}{u}}_j<br><br>\left({\underset{\_}{u}}_j^T<br><br>{\underset{\_}{u}}_j\right)}^{-1}<br><br>{\underset{\_}{u}}_j^T<br><br>{\underset{\_}{s}}_n,$

wherein n is an integer greater than 1, s is a vector of the substantially orthogonal matrix and u is an orthogonalized vector, wherein each vector of the substantially orthogonal set of vectors represents the at least one interfering signal;

providing for generating a substantially orthogonal matrix from the substantially orthogonal set of vectors;

providing for generating a cancellation operator from the substantially orthogonal matrix; and

providing for directionally filtering the interfering signals by projecting the received signal onto a subspace substantially orthogonal to the at least one interfering signal for producing an interference-cancelled signal having substantially no contribution of the at least one interfering in that subspace.

50. The method of claim 49, further comprising providing for computing a portion of a cancellation operator according to the form:

(U^TU)<sup>−

1</sup>,

wherein U is the substantially orthogonal matrix and U^T is a transpose of the substantially orthogonal matrix.

51. The method of claim 50, further comprising providing for computing the cancellation operator according to the form:

P_U^⊥

=I−

U(U^TU)<sup>−

1</sup>U^T,

wherein P_U^⊥

is the cancellation operator and I is an identity matrix.

52. The method of claim 49, further comprising providing for storing computed values of u_j^Tu_j.

53. The method of claim 49, further comprising:

providing for generating values of the portion of the cancellation operator from u_j^Tu_jaccording to;

σ

_j=(u_j^Tu_j)<sup>−

1</sup>,

wherein σ

_j is one of the values of the portion of the cancellation operator; and

providing for storing computed values of σ

_j.

54. The method of claim 53, further comprising providing for comparing the values of σ

_j to a threshold to determine use of the vectors u_j in construction of a converted matrix.

55. A receiver, comprising:

an antenna configured for receiving a radio signal, wherein the radio signal comprises a selected signal and one or more interfering signals;

an analog to digital converter configured for converting the radio signal to a digital signal;

a processing engine configured for substantially canceling said one or more interfering signals in the digital signal, the processing engine comprising

a matrix generator configured for generating a matrix having a plurality of vectors, wherein each of the plurality of vectors comprises elements from at least one of said one or more interfering signals,

a matrix converter communicatively coupled to the matrix generator, wherein the matrix converter is configured for generating a substantially orthogonal vector set from the plurality of vectors to convert the matrix to produce a converted matrix and for computing a portion of a cancellation operator from the converted matrix,

a processor configured for generating the cancellation operator from the converted matrix and the portion of the cancellation operator, and

an applicator configured for applying the cancellation operator to the digital signal to substantially cancel said one or more interfering signals and to generate an interference-canceled signal; and

receiver circuitry communicatively coupled to the processing engine and configured for the processing the interference-canceled signal.

56. The receiver of claim 55, further comprising a matrix converter configured for computing a portion of a cancellation operator according to the form:

(U^TU)<sup>−

1</sup>,

wherein U is the matrix and U^T is a transpose of the matrix.

58. The receiver of claim 55, wherein the substantially orthogonal vector set is generated according to the form:

${\underset{\_}{u}}_n={\underset{\_}{s}}_n-\underset{j=1}{\overset{n-1}{\sum <br><br>}}<br><br>{{\underset{\_}{u}}_j<br><br>\left({\underset{\_}{u}}_j^T<br><br>{\underset{\_}{u}}_j\right)}^{-1}<br><br>{\underset{\_}{u}}_j^T<br><br>{\underset{\_}{s}}_n,$

wherein n is an integer greater than 1, s is a vector of the matrix and u is an orthogonalized vector of the converted said matrix.

59. The receiver of claim 58, wherein the matrix generator comprises a storage unit configured for storing computed values of u_j^Tu_j.

60. The receiver of claim 58, wherein the computed values of u_j^Tu_j are used to generate values of the portion of the cancellation operator according to:

σ

_j=(u_j^Tu_j),

wherein σ

_j is one of the values of the portion of the cancellation operator and wherein the matrix generator comprises a storage unit configured for storing computed values of σ

_j.