Apparatus and methods for selective correlation timing in rake receivers

• US 6,683,924 B1
• Filed: 10/19/1999
• Issued: 01/27/2004
• Est. Priority Date: 10/19/1999
• Status: Expired due to Term

• Current Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Ottosson, Tony, Wang, Yi-Pin Eric, Bottomley, Gregory Edward
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): WILLIAMS, LAWRENCE B
• Application Number:
  US09/420,957
• Time in Patent Office: 1,561 Days
• Field of Search: 375/343, 375/208, 375/222, 375/355, 342/263, 342/357, 455/456
• US Class Current: 375/343
• CPC Class Codes: H04B 1/709 Correlator structure
• CPC Class Codes: H04B 1/7117 Selection, re-selection, allocation or re-allocation of paths to fingers, e.g. timing offset control of allocated fingers
• CPC Class Codes: H04B 1/712 Weighting of fingers for combining, e.g. amplitude control or phase rotation using an inner loop
• CPC Class Codes: H04B 2201/709727 GRAKE type RAKE receivers

Abstract

Correlation times for a RAKE receiver are determined from time differentials between multipath components of a received signal based on correlation metrics, preferably signal strength measurements, associated with the multipath components. According to various embodiments of the present invention, selection strategies are employed in which “desired signal collecting” and “interference collecting” correlation times may be selected using average optimal (AO) or instantaneous optimal (IO) selection criteria. These criteria may include, for example, thresholds for signal strengths associated with multipath components of a signal at the correlation times, where the signal strengths may include absolute or relative measures of signal power or signal to noise ratio. According to alternative embodiments, correlation times are selected using an inverse filter of an estimated channel response. Related apparatus is also described.

Claims

1. A method of processing a communications signal, the method comprising the steps of:

generating respective correlation metrics for respective ones of a plurality of multipath components of a first signal, a respective one of which has a respective time associated therewith; and

generating respective time-offset correlations of a second signal with a modulation sequence at respective correlation times determined from time differentials between the times associated with the plurality of multipath components based on the correlation metrics associated with the plurality of multipath components.

2. A method according to claim 1, wherein the first and second signals comprise the same signal.

3. A method according to claim 1:

wherein said step of generating respective correlation metrics comprises the step of processing the first signal to determine respective signal strengths of respective ones of the plurality of multipath components of the first signal; and

wherein said step of generating respective time-offset correlations of a second signal comprises the step of generating respective time-offset correlations of the second signal with the modulation sequence at correlation times determined from time differentials between times associated with the plurality of multipath components based on the determined signal strengths of the plurality of multipath components.

4. A method according to claim 3:

wherein said step of processing a first signal comprises the steps of;

correlating the first signal with the modulation sequence at respective ones of a set of first correlation times to generate respective first correlation outputs;

determining respective signal strengths for the first correlation outputs; and

determining a second correlation time based on the determined signal strengths for the first correlation outputs; and

wherein said step of generating respective time-offset correlations of a second signal comprises the step of generating respective time-offset correlations of the second signal with the modulation sequence at the first and second correlation times.

5. A method according to claim 4, wherein said step of correlating is preceded by the step of determining the set of first correlation times from the first signal.

6. A method according to claim 5, wherein said step of determining the set of first correlation times comprises the steps of:

correlating the first signal with the modulation sequence at respective ones of a plurality of correlation times to produce respective ones of a plurality of correlation outputs;

determining respective signal strengths of respective ones of the plurality of correlation outputs; and

determining the set of first correlation times from the plurality of correlation times based on the determined signal strengths of the plurality of correlation outputs.

7. A method according to claim 6, wherein said step of determining a second correlation time comprises the steps of:

determining one first correlation time of the set of first correlation times that has a signal strength meeting a predetermined criterion;

determining at least one time differential between the identified one first correlation time and at least one other first correlation time of the set of first correlation times; and

determining the second correlation time from the at least one time differential.

8. A method according to claim 6:

wherein said step of determining respective signal strengths of respective ones of the plurality of correlation outputs comprises the step of determining respective average signal strengths for respective ones of the plurality of correlation outputs;

wherein said step of determining a set of first correlation times comprises the step of selecting a set of L first correlation times τ

₀, . . . , τ

<sub>L−

1</sub> having corresponding determined average signal strengths greater than a first threshold, wherein τ

₀, . . . , τ

<sub>L−

1</sub> denotes a series of first correlation times representing increasing delays;

wherein said step of determining a second correlation time comprises the steps of;

selecting a subset of the set of L first correlation times having corresponding determined average signal strengths greater than a second threshold, the subset including M first correlation times {tilde over (τ

)}₀, . . . , {tilde over (τ

)}<sub>M−

1</sub> wherein {tilde over (τ

)}₀, . . . , {tilde over (τ

)}<sub>M−

1</sub> denotes a series of first correlation times representing increasing delays;

determining respective time differentials Δ

₁, . . . , Δ

<sub>M−

1</sub> between one first correlation time of the subset of M first correlation times having a greatest average signal strength and respective other first correlation times of the subset of M first correlation times, wherein Δ

₁, . . . , Δ

<sub>M−

1</sub> denotes a series of time differentials of increasing magnitude; and

determining at least one second correlation time {{circumflex over (τ

)}_i} in an order of preference beginning with a second correlation time {circumflex over (τ

)}₀ according to the relationship;

9. A method according to claim 6:

wherein said step of determining respective signal strengths of respective ones of the plurality of correlation outputs comprises the step of determining respective average signal strengths for respective ones of the plurality of correlation outputs;

wherein said step of determining a set of first correlation times comprises the step of selecting a set of L first correlation times τ

₀, . . . , τ

<sub>L−

1</sub> having corresponding determined average signal strengths greater than a first threshold, wherein τ

₀, . . . , τ

<sub>L−

1</sub> denotes a series of first correlation times representing increasing delays;

wherein said step of determining a second correlation time comprises the steps of;

selecting a subset of the set of L first correlation times having corresponding determined average signal strengths greater than a second threshold, the subset including M first correlation times {tilde over (τ

)}₀, . . . , {tilde over (τ

)}<sub>M−

1</sub>, wherein {tilde over (τ

)}₀, . . . , {tilde over (τ

)}<sub>M−

1</sub> denotes a series of correlation times representing increasing delays;

determining respective time differentials Δ

₁, Δ

₂, . . . , Δ

<sub>M−

1</sub> between one first correlation time of the subset of M first correlation times having a greatest average signal strength and respective other first correlation times of the subset of M first correlation times, wherein Δ

₁, Δ

₂, . . . , Δ

<sub>M−

1</sub> denotes a series of time differentials of increasing magnitude; and

determining at least one second correlation time {{circumflex over (τ

)}_i} in an order of preference beginning with a second correlation time {circumflex over (τ

)}₀ according to the relationship;

10. A method according to claim 6:

wherein said step of determining respective signal strengths of respective ones of the plurality of correlation outputs comprises the step of determining respective instantaneous signal strengths for respective ones of the plurality of correlation outputs;

wherein said step of determining a set of first correlation times comprises the step of selecting a set of L first correlation times {tilde over (τ

)}₀, . . . , {tilde over (τ

)}<sub>L−

1</sub> having corresponding determined instantaneous signal strengths exceeding a threshold, wherein {tilde over (τ

)}₀, . . . , {tilde over (τ

)}<sub>L−

1</sub> denotes a series of first correlation times having decreasing determined instantaneous signal strengths associated therewith; and

wherein said step of determining a second correlation time comprises the steps of;

determining respective time differentials Δ

₁, Δ

₂, . . . , Δ

<sub>M−

1</sub> between the first correlation time {tilde over (τ

)}₀ having a greatest determined instantaneous signal strength associated therewith and respective other first correlation times of the set of L first correlation times {tilde over (τ

)}₀, . . . , {tilde over (τ

)}<sub>L−

1</sub>, wherein Δ

₁, Δ

₂, . . . , Δ

<sub>M−

1</sub> denotes a series of time differentials for first correlation times having decreasing determined instantaneous signal strengths associated therewith; and

determining at least one second correlation time {circumflex over (τ

)}_i in an order of preference beginning with a second correlation time {circumflex over (τ

)}₀ according to the relationship;

11. A method according to claim 6:

wherein said step of determining respective signal strengths of respective ones of the plurality of correlation outputs comprises the step of determining respective instantaneous signal strengths for respective ones of the plurality of correlation outputs;

wherein said step of determining a set of first correlation times comprises the step of selecting a set of L first correlation times {tilde over (τ

)}₀, . . . , {tilde over (τ

)}<sub>L−

1</sub> having corresponding determined instantaneous signal strengths exceeding a threshold, wherein {tilde over (τ

)}₀, . . . , {tilde over (τ

)}<sub>L−

1</sub> denotes a series of correlation times having decreasing determined instantaneous signal strengths associated therewith; and

wherein said step of determining a second correlation time comprises the steps of;

determining respective time differentials Δ

₁, Δ

₂, . . . , Δ

<sub>M−

1</sub> between the first correlation time {circumflex over (τ

)}₀ having the greatest determined instantaneous signal strength and respective other first correlation times of the set of L first correlation times, wherein Δ

₁, Δ

₂, . . . , Δ

<sub>M−

1</sub> denotes a series of time differentials for correlation times having decreasing determined instantaneous signal strengths associated therewith; and

determining at least one second correlation time {{circumflex over (τ

)}_i} in an order of preference beginning with a second correlation time {circumflex over (τ

)}₀ according to the relationship;

12. A method according to claim 6:

wherein said step of determining respective signal strengths of respective ones of the plurality of correlation outputs comprises the step of determining respective average signal strengths for respective ones of the plurality of correlation outputs;

wherein said step of determining a set of first correlation times comprises the step of selecting a set of M first correlation times {tilde over (τ

)}₀, . . . , {tilde over (τ

)}<sub>M−

1</sub> having determined average signal strengths associated therewith that are greater than a threshold, wherein {tilde over (τ

)}₀, . . . , {tilde over (τ

)}<sub>M−

1</sub> denotes a series of correlation times having decreasing determined average signal strength associated therewith; and

wherein said step of determining a second correlation time comprises the steps of;

determining respective time differentials, Δ

₁, Δ

₂, . . . , Δ

<sub>M−

1</sub> between the first correlation time {tilde over (τ

)}₀ and respective other first correlation times of the subset of M first correlation times; and

determining at least one set of second correlation times {{circumflex over (τ

)}_i}, in an order of preference beginning with a set of second correlation times {{circumflex over (τ

)}}₁ according to the relationship;

13. A method according to claim 6, wherein said step of determining a set of first correlation times comprises the step of selecting correlation times of the plurality of correlation times having a corresponding determined signal strengths that meet a predetermined criterion.

14. A method according to claim 13, wherein said step of selecting comprises the step of selecting correlation times of the plurality of correlation times having corresponding determined signal strengths exceeding a predetermined threshold.

15. A method according to claim 6, wherein said step of determining respective signal strengths of respective ones of the plurality of correlation outputs comprises the step of determining one of absolute signal strengths or a relative signal strengths.

16. A method according to claim 15, wherein said step of determining respective signal strengths of respective ones of the plurality of correlation outputs comprises the step of determining one of normalized signal strengths or signal to noise ratios.

17. A method according to claim 6, wherein said step of determining respective signal strengths of respective ones of the plurality of correlation outputs comprises the step of determining one of average signal strengths or instantaneous signal strengths.

18. A method according to claim 4, wherein said step of determining respective signal strengths of the first correlation outputs comprises the step of determining one of absolute signal strengths or relative signal strengths of the first correlation outputs.

19. A method according to claim 4, wherein said step of determining respective signal strengths of the first correlation outputs comprises the step of determining one of normalized signal strengths or signal to noise ratios of the first correlation outputs.

20. A method according to claim 1:

wherein said step of generating respective correlation metrics comprises the steps of;

generating an estimated channel response from the first signal; and

determining an inverse filter of the estimated channel response, including respective ones of a plurality of inverse filter coefficients and respective delays associated therewith; and

wherein said step of generating respective time-offset correlations comprises the step of generating respective time-offset correlation of the second signal with the modulation sequence at respective correlation times selected from the plurality of delays based on the inverse filter coefficients.

21. A method according to claim 20:

wherein said step of generating an estimated channel response comprises the step of generating an instantaneous channel response estimate; and

wherein said step of determining an inverse filter comprises the step of determining the inverse filter from the instantaneous channel response estimate.

22. A method according to claim 20:

wherein said step of generating an estimated channel response comprises the step of generating an average channel response estimate; and

wherein said step of determining an inverse filter comprises the step of determining the inverse filter from the average channel response estimate.

23. A method according to claim 20, wherein said step of generating respective time-offset correlations of the second signal with the modulation sequence at respective correlation times selected from the plurality of delays comprises the step of generating respective time-offset correlations of the second signal with the modulation sequence at delays of the plurality of delays for which the corresponding inverse filter coefficient is greater than a predetermined threshold.

24. A method according to claim 1, further comprising the steps of:

generating an interference-compensated signal from the generated time-offset correlations of the second signal with the modulation sequence; and

recovering information from the interference-compensated signal.

25. A receiver, comprising:

a correlation timing determiner, responsive to a first signal, that generates respective correlation metrics for respective ones of a plurality of multipath components of the first signal, a respective one of which has a respective time associated therewith, and determines a set of correlation times from time differentials between the times associated with the plurality of multipath components based on the correlation metrics associated with the plurality of multipath components;

a correlation unit operatively associated with the correlation timing determiner and responsive to a second signal, that generates respective time-offset correlations of a second signal with a modulation sequence at respective correlation times of the selected set of correlation times; and

a combiner that combines the time-offset correlations of the second signal with the modulation sequence to produce an estimate of information represented by the second signal.

26. A receiver according to claim 25, wherein the first and second signals comprise the same signal.

27. A receiver according to claim 25, wherein the correlation timing determiner comprises:

a search correlation unit that generates respective correlation outputs for respective ones of the multipath components;

a signal strength determiner that determines respective signal strengths of respective ones of the plurality of multipath components of the first signal; and

a correlation time selector that selects the set of correlation times based on the determined signal strengths.

28. A receiver according to claim 27:

wherein the search correlation unit correlates the first signal with the modulation sequence at respective ones of a set of first correlation times to generate respective first correlation outputs;

wherein the signal strength determiner determines respective signal strengths for the first correlation outputs;

wherein the correlation time selector selects a second correlation time based on the determined signal strengths for the first correlation outputs; and

wherein the correlation unit generates respective time-offset correlations of the second signal with the modulation sequence at the first and second correlation times.

29. A receiver according to claim 28, wherein the correlation time selector comprises:

means for determining one first correlation time of the set of first correlation times that has a signal strength meeting a predetermined criterion;

means for determining at least one time differential between the identified one first correlation time and at least one other first correlation time of the set of first correlation times; and

means for determining the second correlation time from the at least one time differential.

30. A receiver according to claim 27, wherein the signal strength determiner determines one of absolute signal strengths or a relative signal strengths.

31. A receiver according to claim 30, wherein the signal strength determiner determines one of normalized signal strengths or signal to noise ratios.

32. A receiver according to claim 30, wherein the signal strength determiner determines one of average signal strengths or instantaneous signal strengths.

33. A receiver according to claim 25:

wherein the correlation timing determiner comprises;

means for generating an estimated channel response from the first signal; and

means for determining an inverse filter of the estimated channel response, including respective ones of a plurality of inverse filter coefficients and respective delays associated therewith; and

means for determining the set of correlation times at respective correlation times selected from the plurality of delays based on the inverse filter coefficients.

34. A receiver according to claim 25, wherein the combiner cancels interference with respect to a desired signal, and wherein the correlation timing determiner selects correlation times such that the correlation unit preferentially collects energy in the second signal associated with the desired signal and the interference.

35. A receiver, comprising:

means for generating respective correlation metrics for respective ones of a plurality of multipath components of a first signal; and

means, responsive to said means for generating respective correlation metrics, for generating respective time-offset correlations of a second signal with a modulation sequence at respective correlation times determined from time differentials between times associated with the plurality of multipath components based on the correlation metrics associated with the plurality of multipath components.

36. A receiver according to claim 35, wherein the first and second signals comprise the same signal.

37. A receiver according to claim 35:

wherein said means for generating respective correlation metrics comprises means for processing the first signal to determine respective signal strengths of respective ones of the plurality of multipath components of the first signal; and

wherein said means for generating respective time-offset correlations of a second signal comprises means for generating respective time-offset correlations of the second signal with the modulation sequence at correlation times determined from time differentials between times associated with the plurality of multipath components based on the determined signal strengths of the plurality of multipath components.

38. A receiver according to claim 37:

wherein said means for processing a first signal comprises;

means for correlating the first signal with the modulation sequence at respective ones of a set of first correlation times to generate respective first correlation outputs;

means for determining respective signal strengths for the first correlation outputs; and

means for determining a second correlation time based on the determined signal strengths for the first correlation outputs; and

wherein said means for generating respective time-offset correlations of a second signal comprises means for generating respective time-offset correlations of the second signal with the modulation sequence at the first and second correlation times.

39. A receiver according to claim 38, further comprising means for determining the set of first correlation times from the first signal.

40. A receiver according to claim 39, wherein said means for determining the set of first correlation times comprises:

means for correlating the first signal with the modulation sequence at respective ones of a plurality of correlation times to produce respective ones of a plurality of correlation outputs;

means for determining respective signal strengths of respective ones of the plurality of correlation outputs; and

means for determining the set of first correlation times from the plurality of correlation times based on the determined signal strengths of the plurality of correlation outputs.

41. A receiver according to claim 40, wherein said means for determining a second correlation time comprises:

means for determining one first correlation time of the set of first correlation times that has a signal strength meeting a predetermined criterion;

means for determining at least one time differential between the identified one first correlation time and at least one other first correlation time of the set of first correlation times; and

means for determining the second correlation time from the at least one time differential.

42. A receiver according to claim 40:

wherein said means for determining respective signal strengths of respective ones of the plurality of correlation outputs comprises means for determining respective average signal strengths for respective ones of the plurality of correlation outputs;

wherein said means for determining a set of first correlation times comprises means for selecting a set of L first correlation times τ

₀, . . . , τ

<sub>L−

1</sub> having corresponding determined average signal strengths greater than a first threshold, wherein τ

₀, . . . , τ

<sub>L−

1</sub> denotes a series of first correlation times representing increasing delays;

wherein said means for determining a second correlation time comprises;

means for selecting a subset of the set of L first correlation times having corresponding determined average signal strengths greater than a second threshold, the subset including M first correlation times {tilde over (τ

)}₀, . . . , {tilde over (τ

)}<sub>M−

1</sub>, wherein {tilde over (τ

)}₀, . . . , {tilde over (τ

)}<sub>M−

1</sub> denotes a series of first correlation times representing increasing delays;

means for determining respective time differentials Δ

₁, . . . , Δ

<sub>M−

1</sub> between one first correlation time of the subset of M first correlation times having a greatest average signal strength and respective other first correlation times of the subset of M first correlation times, wherein Δ

₁, . . . , Δ

<sub>M−

1</sub> denotes a series of time differentials of increasing magnitude; and

means for determining at least one second correlation time {{circumflex over (τ

)}_i} in an order of preference beginning with a second correlation time {circumflex over (τ

)}₀ according to the relationship;

43. A receiver according to claim 40:

wherein said means for determining respective signal strengths of respective ones of the plurality of correlation outputs comprises means for determining respective average signal strengths for respective ones of the plurality of correlation outputs;

wherein said means for determining a set of first correlation times comprises means for selecting a set of L first correlation times τ

₀, . . . , τ

<sub>L−

1</sub> having corresponding determined average signal strengths greater than a first threshold, wherein τ

₀, . . . , τ

<sub>L−

1</sub> denotes a series of first correlation times representing increasing delays;

wherein said means for determining a second correlation time comprises the steps of;

means for selecting a subset of the set of L first correlation times having corresponding determined average signal strengths greater than a second threshold, the subset including M first correlation times {tilde over (τ

)}₀, . . . , {tilde over (τ

)}<sub>M−

1</sub>, wherein {tilde over (τ

)}₀, . . . , {tilde over (τ

)}<sub>M−

1</sub> denotes a series of correlation times representing increasing delays;

means for determining respective time differentials Δ

₁, Δ

₂, . . . , Δ

<sub>M−

1</sub> between one first correlation time of the subset of M first correlation times having a greatest average signal strength and respective other first correlation times of the subset of M first correlation times, wherein Δ

₁, Δ

₂, . . . , Δ

<sub>M−

1</sub> denotes a series of time differentials of increasing magnitude; and

means for determining at least one second correlation time {{circumflex over (τ

)}_i} in an order of preference beginning with a second correlation time {circumflex over (τ

)}₀ according to the relationship;

44. A receiver according to claim 40:

wherein said means for determining respective signal strengths of respective ones of the plurality of correlation outputs comprises means for determining respective instantaneous signal strengths for respective ones of the plurality of correlation outputs;

wherein said means for determining a set of first correlation times comprises means for selecting a set of L first correlation times {tilde over (τ

)}₀, . . . , {tilde over (τ

)}<sub>L−

1</sub> having corresponding determined instantaneous signal strengths exceeding a threshold, wherein {tilde over (τ

)}₀, . . . , {tilde over (τ

)}<sub>L−

1</sub> denotes a series of first correlation times having decreasing determined instantaneous signal strengths associated therewith; and

wherein said means for determining a second correlation time comprises the steps of;

means for determining respective time differentials Δ

₁, Δ

₂, . . . , Δ

<sub>M−

1</sub> between the first correlation time {tilde over (τ

)}₀ having a greatest determined instantaneous signal strength associated therewith and respective other first correlation times of the set of L first correlation times {tilde over (τ

)}₀, . . . , {tilde over (τ

)}<sub>L−

1</sub>, wherein Δ

₁, Δ

₂, . . . , Δ

<sub>M−

1</sub> denotes a series of time differentials for first correlation times having decreasing determined instantaneous signal strengths associated therewith; and

means for determining at least one second correlation time {circumflex over (τ

)}_i in an order of preference beginning with a second correlation time {circumflex over (τ

)}₀ according to the relationship;

 

{{circumflex over (τ

)}₀, {circumflex over (τ

)}₁, . . . }={tilde over (τ

)}₀−

Δ

₁, {tilde over (τ

)}₀−

2Δ

₁, {tilde over (τ

)}₀−

3Δ

₁, . . . ; and

wherein said means for generating respective time-offset correlations of a second signal comprises means for generating respective time-offset correlations of the second signal with the modulation sequence at the L first correlation times and the determined at least one second correlation time.

45. A receiver according to claim 40:

wherein said means for determining respective signal strengths of respective ones of the plurality of correlation outputs comprises means for determining respective instantaneous signal strengths for respective ones of the plurality of correlation outputs;

wherein said means for determining a set of first correlation times comprises means for selecting a set of L first correlation times {tilde over (τ

)}₀, . . . , {tilde over (τ

)}<sub>L−

1</sub> having corresponding determined instantaneous signal strengths exceeding a threshold, wherein {tilde over (τ

)}₀, . . . , {tilde over (τ

)}<sub>L−

1</sub> denotes a series of correlation times having decreasing determined instantaneous signal strengths associated therewith; and

wherein said means for determining a second correlation time comprises the steps of;

means for determining respective time differentials Δ

₁, Δ

₂, . . . , Δ

<sub>M−

1</sub> between the first correlation time {tilde over (τ

)}₀ having the greatest determined instantaneous signal strength and respective other first correlation times of the set of L first correlation times, wherein Δ

₁, Δ

₂, . . . , Δ

<sub>M−

1</sub> denotes a series of time differentials for correlation times having decreasing determined instantaneous signal strengths associated therewith; and

means for determining at least one second correlation time {{circumflex over (τ

)}_i} in an order of preference beginning with a second correlation time {circumflex over (τ

)}₀ according to the relationship;

46. A receiver according to claim 40:

wherein said means for determining respective signal strengths of respective ones of the plurality of correlation outputs comprises means for determining respective average signal strengths for respective ones of the plurality of correlation outputs;

wherein said means for determining a set of first correlation times comprises means for selecting a set of M first correlation times {tilde over (τ

)}₀, . . . , {tilde over (τ

)}<sub>M−

1</sub> having determined average signal strengths associated therewith that are greater than a threshold, wherein {tilde over (τ

)}₀, . . . , {tilde over (τ

)}<sub>M−

1</sub> denotes a series of correlation times having decreasing determined average signal strength associated therewith; and

wherein said means for determining a second correlation time comprises;

means for determining respective time differentials Δ

₁, Δ

₂, . . . , Δ

<sub>M−

1</sub> between the first correlation time {tilde over (τ

)}₀ and respective other first correlation times of the subset of M first correlation times; and

means for determining at least one set of second correlation times {{circumflex over (τ

)}}_i, in an order of preference beginning with a set of second correlation times {{circumflex over (τ

)}}₁ according to the relationship;

47. A receiver according to claim 40, wherein said means for determining a set of first correlation times comprises means for selecting correlation times of the plurality of correlation times having a corresponding determined signal strengths that meet a predetermined criterion.

48. A receiver according to claim 47, wherein said means for selecting comprises means for selecting correlation times of the plurality of correlation times having corresponding determined signal strengths exceeding a predetermined threshold.

49. A receiver according to claim 40, wherein said means for determining respective signal strengths of respective ones of the plurality of correlation outputs comprises means for determining one of absolute signal strengths or a relative signal strengths.

50. A receiver according to claim 49, wherein said means for determining respective signal strengths of respective ones of the plurality of correlation outputs comprises means for determining one of normalized signal strengths or signal to noise ratios.

51. A receiver according to claim 40, wherein said means for determining respective signal strengths of respective ones of the plurality of correlation outputs comprises means for determining one of average signal strengths or instantaneous signal strengths.

52. A receiver according to claim 38, wherein said means for determining respective signal strengths of the first correlation outputs comprises means for determining one of absolute signal strengths or relative signal strengths of the first correlation outputs.

53. A receiver according to claim 52, wherein said means for determining respective signal strengths of the first correlation outputs comprises means for determining one of normalized signal strengths or signal to noise ratios of the first correlation outputs.

54. A receiver according to claim 35:

wherein said means for generating respective correlation metrics comprises;

means for generating an estimated channel response from the first signal; and

means for determining an inverse filter of the estimated channel response, including respective ones of a plurality of inverse filter coefficients and respective delays associated therewith; and

wherein said means for generating respective time-offset correlations comprises means for generating respective time-offset correlation of the second signal with the modulation sequence at respective correlation times selected from the plurality of delays based on the inverse filter coefficients.

55. A receiver according to claim 54:

wherein said means for generating an estimated channel response comprises means for generating an instantaneous channel response estimate; and

wherein said means for determining an inverse filter comprises means for determining the inverse filter from the instantaneous channel response estimate.

56. A receiver according to claim 54:

wherein said means for generating an estimated channel response comprises means for generating an average channel response estimate; and

wherein said means for determining an inverse filter comprises means for determining the inverse filter from the average channel response estimate.

57. A receiver according to claim 54, wherein said means for generating respective time-offset correlations of the second signal with the modulation sequence at respective correlation times selected from the plurality of delays comprises means for generating respective time-offset correlations of the second signal with the modulation sequence at delays of the plurality of delays for which the corresponding inverse filter coefficient is greater than a predetermined threshold.

58. A receiver according to claim 35, further comprising:

means for generating an interference-compensated signal from the generated time-offset correlations of the second signal with the modulation sequence; and

means for recovering information from the interference-compensated signal.