Methods for estimation and interference suppression for signal processing

• US 20110292974A1
• Filed: 08/08/2011
• Published: 12/01/2011
• Est. Priority Date: 09/23/2002
• Status: Active Grant

• Current Assignee: III Holdings 1, LLC (Intellectual Ventures LLC)
• Original Assignee: Rambus Inc.
• Inventors: Lamba, Gagandeep Singh, Narayan, Anand P., McCloud, Michael, Guess, Tommy
• Granted Patent: US 8,457,263 B2
• Time in Patent Office: Days
• US Class Current: 375/148
• CPC Class Codes: H04B 1/7097 Interference-related aspects
• CPC Class Codes: H04B 1/7107 Subtractive interference cancellation
• CPC Class Codes: H04B 1/71072 Successive interference cancellation
• CPC Class Codes: H04B 1/71075 Parallel interference cancellation
• CPC Class Codes: H04B 1/7115 Constructive combining of multi-path signals, i.e. RAKE receivers
• 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 15/00 Suppression or limitation of noise or interference by means associated with receiver H04B1/10
• CPC Class Codes: H04B 2001/71077 Partial interference cancellation
• CPC Class Codes: H04B 2201/709718 Determine interference
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04J 13/0048 Walsh
• CPC Class Codes: H04L 43/08 Monitoring or testing based on specific metrics, e.g. QoS, energy consumption or environmental parameters
• CPC Class Codes: H04W 24/08 Testing, supervising or monitoring using real traffic

Abstract

A receiver in a CDMA system comprises a front end processor that generates a combined signal per source. A symbol estimator processes the combined signal to produce symbol estimates. An S-Matrix Generation module refines these symbol estimates based on the sub channel symbol estimates. An interference canceller is configured for cancelling interference from at least one of the plurality of received signals for producing at least one interference-cancelled signal.

Claims

1. A receiver comprising a processor configured for:

receiving a combined signal, the combined signal comprising fewer than all available signal paths and sectors;

processing the combined signal to produce one or more symbol estimates;

operating on the one or more symbol estimates to generate one or more symbol quality estimates based on the one or more symbol estimates; and

combining the one or more symbol estimates with the one or more symbol quality estimates for at least one of a plurality of user subchannels.

2. The receiver recited in claim 1, further comprising a post-processing module configured for generating at least one interference vector.

3. The receiver in claim 1, further comprising an interference suppressor module configured for suppressing interference from at least one received signal from at least one of the available signal paths and sectors for producing at least one interference-suppressed signal.

4. The receiver recited in claim 1, wherein the combined signal is received from a front end comprising a plurality of fingers and a finger combiner.

5. The receiver recited in claim 4, wherein plurality of fingers comprises a single finger configured for processing multipaths in a Time Division Multiplex mode.

6. The receiver recited in claim 1, wherein the combined signal is received from a Rake receiver.

7. The receiver recited in claim 1, wherein the combined signal is received from an equalizer.

8. The receiver recited in claim 4, wherein the processor is further configured to output a global pseudo-noise (PN) sequence and alignments of PN sequences of each of the plurality of fingers with respect to the global PN sequence.

9. The receiver recited in claim 4, wherein the finger combiner is configured to weight at least one of the plurality of received signals.

10. The receiver recited in claim 3, further comprising a control unit configured to produce a routing decision based on estimated signal quality for each interference-suppressed signal and estimated signal quality from at least one received signal from at least one of the available signal paths and sectors.

11. The receiver recited in claim 1, further comprising:

a demultiplexer configured to separate data/preamble chips, Mac chips, and pilot chips;

a data/preamble discriminator to distinguish between data and preamble chips; and

a Walsh decover block configured to produce the decovered data.

12. The receiver recited in claim 1, further comprising at least one filter configured for filtering at least one of the symbol estimates.

13. The receiver recited in claim 1, wherein the processor further is configured for deriving an average signal strength over at least one of time and different Walsh codes.

14. The receiver recited in claim 3, wherein the interference suppressor is configured for performing at least one of a projection and a subtraction.

15. The receiver recited in claim 3, further comprising a control unit configured to adapt the interference suppressor for each channel depending on operating conditions.

16. The receiver recited in claim 1, wherein the processor is further configured for generating at least one weight based on at least one of the symbol estimates.

17. The receiver recited in claim 1, wherein the processor is further configured to use a Fast Hadamard Transform to compute the symbol estimates.

18. The receiver recited in claim 1, wherein the processor is further configured to use a Fast Fourier Transform to compute the symbol estimates.

19. The receiver recited in claim 1, wherein the processor is further configured to compute an SINR of at least one of the plurality of user subchannels.

20. The receiver recited in claim 1, wherein the processor is further configured to calculate a noise power based on one or more known pilot bits.

21. The receiver recited in claim 1, wherein the processor is further configured to use estimates of at least one of the plurality of user subchannels and one or more noise power estimates to compute an interference power.

22. The receiver recited in claim 1, where the processor and an interference suppressor are coupled serially from one source to another.

23. The receiver recited in claim 1, where the processor and an interference suppressor are coupled in parallel for a plurality of sources.

24. A reception method comprising:

receiving a combined signal, the combined signal derived from one or more received signals received from a plurality of fingers, the plurality of signals comprising fewer than all available signal paths and sectors for use in producing a combined signal;

processing the combined signal to produce one or more symbol estimates;

operating on the one or more symbol estimates to generate one or more symbol quality estimates; and

combining the said one or more symbol estimates with the one or more symbol quality estimates for at least one of a plurality of user subchannels.

25. The method recited in claim 24, further comprising generating at least one interference vector.

26. The method recited in claim 24, further comprising suppressing interference from at least one received signal to produce at least one interference-suppressed signal.

27. The method recited in claim 24, wherein the combined signal is derived using a single finger configured for processing multipaths in a Time Division Multiplex mode.

28. The method recited in claim 24, wherein the combined signal is derived by a Rake receiver.

29. The method recited in claim 24, wherein the combined signal is derived by an equalizer.

30. The method recited in claim 24, wherein the combined signal is derived at least in part by producing a global pseudo-noise (PN) sequence and alignments of PN sequences of each of the plurality of fingers with respect to the global PN sequence.

31. The method recited in claim 24, wherein the combined signal is derived at least in part by weighting at least one received signal.

32. The method recited in claim 24, further comprising producing a routing decision based on estimated signal quality for each interference-suppressed signal and estimated signal quality from at least one received signal.

33. The method recited in claim 24, wherein processing the combined signal to produce symbol estimates further comprises:

separating data/preamble chips, Mac chips, and pilot chips;

distinguishing between data and preamble chips; and

performing Walsh decovering to produce the decovered data.

34. The method recited in claim 24, further comprising filtering at least one of the symbol estimates.

35. The method recited in claim 24, further comprising deriving an average signal strength over at least one of time and a plurality of Walsh codes.

36. The method recited in claim 26, wherein suppressing comprises performing at least a projection operation or a subtraction.

37. The method recited in claim 26, further comprising adapting suppression for each channel depending on operating conditions.

38. The method recited in claim 24, wherein operating on the symbol estimates to generate symbol quality estimates comprises generating at least one weight based on one or more of the symbol estimates.

39. The method recited in claim 24, wherein processing the combined signal to produce symbol estimates comprises using a Fast Hadamard Transform to compute the symbol estimates.

40. The method recited in claim 24, wherein processing the combined signal to produce symbol estimates comprises using a Fast Fourier Transform to compute the symbol estimates.

41. The method recited in claim 24, wherein operating on the symbol estimates to generate symbol quality estimates comprises computing an SINR of at least one of the plurality of user subchannels.

42. The method recited in claim 24, wherein operating on the symbol estimates to generate symbol quality estimates comprises using knowledge of one or more known pilot bits to calculate a noise power.

43. The method recited in claim 24, wherein operating on the symbol estimates to generate symbol quality estimates comprises using estimates of a plurality of subchannels and one or more noise power estimates to compute an interference power.

44. The method of claim 26, wherein suppressing interference is performed serially from one source to another.

45. The method of claim 26, where suppressing interference is performed in parallel for a plurality of sources.

46. A handset configured to perform the method recited in claim 24.

47. A chipset configured to perform the method recited in claim 24.

48. A digital computer system programmed to perform the method recited in claim 24.

49. A computer-readable medium storing a computer program implementing the method of claim 24.

50. A base station configured to perform the method of claim 24.

51. A system for determining user power and background noise power in multiple-access communication comprising:

a processor configured for

tracking one or more active base stations;

estimating powers of one or more base station pilots; and

estimating one or more multipath channels from the one or more base stations to one or more mobile stations; and

an estimation module configured for

relating unknown user and noise powers to estimates of at least one output power from at least one of a RAKE receiver and an equalizer and statistical quantities that depend on the estimated channels; and

calculating estimates of at least one user power and the background noise power.

52. The power estimator in claim 51, wherein the processor receives signals from a plurality of receive antennas.

53. The power estimator in claim 51, wherein the processor is further configured to operate with surrogate user sequences in networks that use multilevel codes.

54. The power estimator in claim 51, wherein the estimation module uses statistical quantities that are estimated using time-averaging.

55. The power estimator in claim 51, wherein the processor is further configured to provide the estimates of the one or more base station pilot powers to the estimation module and wherein the estimation module is further configured to use the estimates of the one or more base station pilot powers as the final estimates of one or more subchannels.

56. The power estimator in claim 51, wherein the estimation module is further configured to use the estimates of the base station pilot powers from the processor temporarily to append additional equations when setting up the constrained optimization problem which when solved will provide improved estimates of those pilot powers.

57. A method for power estimation comprising:

tracking one or more active base stations;

estimating power of one or more base station pilots;

estimating one or more multipath channels from the one or more base stations to one or more mobile station;

estimating the unknown user and noise powers from estimates of at least one output power for at least one of a RAKE receiver and an equalizer and statistical quantities that depend on the estimated channels; and

estimating at least one user power and the background noise power.

58. The method recited in claim 57, wherein the step of tracking comprises receiving signals from a plurality of receive antennas.

59. The method recited in claim 57, further comprising operating with surrogate user sequences in networks that use multilevel codes.

60. The method recited in claim 57, wherein the statistical quantities are estimated using time-averaging.

61. The method recited in claim 57, further comprising using the estimates of one or more base station pilot powers from the processor as the final estimates of corresponding subchannels.

62. The method recited in claim 57, wherein estimation uses the estimates of the base station pilot powers from the processor temporarily to append additional equations when setting up the constrained optimization problem which when solved will provide improved estimates of those pilot powers.

63. The method recited in claim 57, further comprising providing the estimates to a multi user receiver.

64. A handset configured to perform the method recited in claim 57.

65. A chipset configured to perform the method recited in claim 57.

66. A digital computer system programmed to perform the method recited in claim 57.

67. A computer-readable medium storing a computer program implementing the method of claim 57.

68. A base station configured to perform the method of claim 57.

69. A user-channel quality estimator comprising:

a processor configured for

calculating an effective receive filter;

calculating a desired user'"'"'s instantaneous output power; and

calculating one or more instantaneous powers of interference, wherein the one or more instantaneous powers of interference comprise one or more of background noise, inter-symbol interference, intra-cell interference and inter-cell interference.

70. The user-channel quality estimator of claim 69, wherein the processor is further configured for determining the channel quality by:

averaging one or more output powers of one or more desired users to produce an average output power;

averaging one or more instantaneous interference powers to produce an average instantaneous power of interference; and

evaluating the ratio of the average output power to the average instantaneous power of interference.

71. The user-channel quality estimator of claim 69, where the channel quality is measured by averaging the ratio of instantaneous user-of-interest power divided by the instantaneous interference power.

72. The user-channel quality estimator of claim 69, further comprising measuring channel quality by evaluating a function of ratios of the desired user'"'"'s instantaneous output power divided by the instantaneous power of interference over multiple symbol instants.

73. The user-channel quality estimator of claim 72, wherein the function estimates the average symbol error rate of one of a known signaling constellation or an assumed signaling constellation.

74. The user-channel quality estimator of claim 72, where the function estimates the maximum average data-rate that could be reliably transmitted to the desired user from its serving base station.

75. A method for estimating user-channel quality comprising:

configuring a processor to

calculate an effective receive filter;

calculate instantaneous user-of-interest power; and

calculate at least one instantaneous interference power, wherein the at least one instantaneous interference power comprises one or more of background noise, inter-symbol interference, intra-cell interference and inter-cell interference.

76. The method recited in claim 75, wherein the processor is further configured for:

averaging the instantaneous user-of-interest power;

averaging the instantaneous interference power; and

evaluating the ratio of instantaneous user-of-interest power to instantaneous interference power.

77. The method recited in claim 75, wherein the processor is further configured for averaging the ratio of instantaneous user-of-interest power divided by the instantaneous interference power.

78. The method recited in claim 75, wherein the processor is further configured for evaluating a function of ratios of instantaneous user-of-interest power divided by instantaneous interference power over multiple symbol instants.

79. The method recited in claim 78, wherein the function estimates the average symbol error rate of least one of a known signaling constellation or an assumed signaling constellation.

80. The method recited in claim 78, wherein the function estimates the maximum average data-rate that could be reliably transmitted to a user-of-interest from its serving base station.