Correlation shaping multi-signature receiver

• US 20020141481A1
• Filed: 06/25/2001
• Published: 10/03/2002
• Est. Priority Date: 02/20/2001
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Oppenheim, Alan V., Eldar, Yonina C.
• Granted Patent: US 7,636,403 B2
• Time in Patent Office: Days
• US Class Current: 375/143
• CPC Class Codes: H04B 1/7093 Matched filter type
• CPC Class Codes: H04B 1/7097 Interference-related aspects
• CPC Class Codes: H04B 2001/70935 using a bank of matched fileters, e.g. Fast Hadamard Transform

Abstract

A receiver for and method of processing received signals comprising a linear combination of a plurality of signature signals having undergone some distortion. The receiver is comprised of a bank of correlators for receiving the signals, and a correlation shaper operating on a vector output from the bank of correlators. The bank of correlators may comprise a matched filter receiver or a decorrelator receiver. Optionally, a bank of detectors may operate on the vector output of the correlation shaper.

Claims

1. A receiver comprising:

a bank of correlators for receiving a signal that is a linear combination of a set of signature signals that has undergone some distortion; and

a correlation shaper operating on a vector output from the bank of correlators.

2. The receiver of claim 1, wherein the bank of correlators is a decorrelator receiver.

3. The receiver of claim 1, wherein the bank of correlators is a matched filter receiver.

4. The receiver of claim 1, wherein the correlation shaper is a whitening transformation.

5. The receiver of claim 4, wherein the whitening transformation is determined by minimizing the mean squared error between the vector output from the bank of correlators and an output vector from the correlation shaper.

6. The receiver of claim 1, wherein the correlation shaper is comprised of a transformation, the transformation being determined by minimizing the mean squared error between the vector output from the bank of correlators and an output vector of the correlation shaper.

7. The receiver of claim 1, wherein the correlation shaper is chosen so that a covariance matrix of an output vector of the correlation shaper has the property that the second and subsequent rows are permutations of the first row.

8. The receiver of claim 7, wherein the correlation shaper is also chosen by minimizing the mean squared error between the vector output from the bank of correlators and the output vector from the correlation shaper.

9. The receiver of claim 1, wherein the correlation shaper is a subspace whitening transformation.

10. The receiver of claim 9, wherein the subspace whitening transformation is determined by minimizing the mean squared error between the vector output from the bank of correlators and an output vector from the correlation shaper.

11. The receiver of claim 6, wherein the transformation is performed on a subspace.

12. The receiver of claim 1, wherein the correlation shaper is chosen so that a covariance matrix of a representation of an output vector from the correlation shaper in the space in which it lies has the property that the second and subsequent rows are permutations of the first row.

13.he. The receiver of claim 12, wherein the correlation shaper is determined by minimizing the mean squared error between the vector output from the bank of correlators and the output vector from the correlation shaper.

14.he. The receiver of claim 1, wherein the bank of correlators cross-correlates the received signal with a set of orthogonal signals.

15. The receiver of claim 14, wherein the set of orthogonal signals is determined by minimizing the least-squares error between the set of orthogonal signals and the set of signature signals.

16. The receiver of claim 14, wherein the set of orthogonal signals is determined by minimizing the least-squares error between the set of orthogonal signals and a set of decorrelator signals.

17. The receiver of claim 1, wherein the bank of correlators cross-correlates the received signal with a set of geometrically uniform signals.

18. The receiver of claim 17, wherein the set of geometrically uniform signals is determined by minimizing the least-squares error between the set of geometrically uniform signals and the set of signature signals.

19. The receiver of claim 17, wherein the set of geometrically uniform signals is determined by minimizing the least-squares error between the set of geometrically uniform signals and a set of decorrelator signals.

20. The receiver of claim 1, wherein the bank of correlators cross-correlates the received signal with a set of projected orthogonal signals.

21. The receiver of claim 20, wherein the set of projected orthogonal signals is determined by minimizing the least-squares error between the set of projected orthogonal signals and the set of signature signals.

22. The receiver of claim 20, wherein the set of projected orthogonal signals is determined by minimizing the least-squares error between the set of projected orthogonal signals and a set of decorrelator signals.

23. The receiver of claim 1, wherein the bank of correlators cross-correlates the received signal with a set of projected geometrically uniform signals.

24. The receiver of claim 23, wherein the set of projected geometrically uniform signals is determined by minimizing the least-squares error between the set of projected geometrically uniform signals and the set of signature signals.

25. The receiver of claim 23, wherein the set of projected geometrically uniform signals is determined by minimizing the least-squares error between the set of projected geometrically uniform signals and a set of decorrelator signals.

26. The receiver of claim 1, further comprising a bank of detectors operating on the output from the correlation shaper.

28. The method of claim 27, wherein shaping the correlation of the vector output further comprises the step of performing a whitening transformation on the vector output.

29. The method of claim 28, wherein performing the whitening transformation further comprises the step of minimizing the mean squared error between the vector output and an output vector from the whitening transformation.

30. The method of claim 27, wherein shaping the correlation of the vector output further comprises the step of performing a transformation on the vector output, wherein the transformation is determined by minimizing the mean squared error between the vector output and an output vector of the transformation.

31. The method of claim 27, wherein shaping the correlation of the vector output further comprises the step of performing a transformation of the vector output such that the covariance matrix of the vector output of the transformation has the property that the second and each subsequent row is a permutation of the first.

32. The method of claim 31, wherein performing the transformation further comprises the step of minimizing the mean squared error between the vector output and the output vector from the transformation.

33. The method of claim 27, wherein shaping the correlation of the vector output further comprises the step of performing a subspace whitening transformation on the vector output.

34. The method of claim 33, wherein performing the subspace whitening transformation further comprises the step of minimizing the mean squared error between the vector output and an output vector from the subspace whitening transformation.

35. The method of claim 27, wherein shaping the correlation of the vector output further comprises the step of performing a transformation of the vector output such that the covariance matrix of the representation of the output vector of the transformation on the space in which it lies has the property that the second and each subsequent row is a permutation of the first.

36. The method of claim 35, wherein performing the transformation further comprises the step of minimizing the mean squared error between the vector output and the output vector from the transformation.

37. The method of claim 27, wherein shaping the correlation of the vector output further comprises the step of cross-correlating the received signals with a set of orthogonal signals.

38. The method of claim 37, further comprising the step of minimizing the least-squares error between the signature signals and the set of orthogonal signals.

39. The method of claim 37, further comprising the step of minimizing the least-squares error between the set of orthogonal signals and a set of decorrelator signals.

40. The method of claim 27, wherein shaping the correlation of the vector output further comprises the step of cross-correlating the received signal with a set of geometrically uniform signals.

41. The method of claim 40, further comprising the step of minimizing the least-squares error between the signature signals and the set of geometrically uniform signals.

42. The method of claim 40, further comprising the step of minimizing the least-squares error between the set of geometrically uniform signals and a set of decorrelator signals.

43. The method of claim 27, wherein shaping the correlation of the vector output further comprises the step of shaping the correlation of the vector output on a subspace by cross-correlating the received signals with a set of projected orthogonal signals.

44. The method of claim 43, further comprising the step of minimizing the least-squares error between the set of projected orthogonal signals and the signature signals.

45. The method of claim 43, further comprising the step of minimizing the least-squares error between the projected orthogonal signals and a set of decorrelator signals.

46. The method of claim 27, wherein shaping the correlation of the vector output further comprises the step of shaping the correlation of the vector output on a subspace by cross-correlating the received signal with a set of projected geometrically uniform signals.

47. The method of claim 46, further comprising the step of minimizing the least-squares error between the projected geometrically uniform signals and the signature signals.

48. The method of claim 46, further comprising the step of minimizing the least-squares error between the projected geometrically uniform signals and a set of decorrelator signals.

27. A method for processing signals in a multi-signature system comprising the steps of:

receiving a signal that is a linear combination of a set of signature signals that has undergone some distortion;

processing the received signal to obtain a vector output; and

shaping the correlation of the vector output.