Advanced signal processors for interference cancellation in baseband receivers

• US 20060227908A1
• Filed: 08/15/2005
• Published: 10/12/2006
• Est. Priority Date: 04/07/2005
• Status: Active Grant

• Current Assignee: III Holdings 1, LLC
• Original Assignee: Rambus Inc.
• Inventors: Scharf, Louis L., Nagarajan, Vijay
• Granted Patent: US 7,787,572 B2
• Time in Patent Office: Days
• US Class Current: 375/346
• CPC Class Codes: H04B 1/1027 assessing signal quality or detecting noise/interference for the received signal
• CPC Class Codes: H04B 1/1081 Reduction of multipath noise by equalising H04B7/005
• CPC Class Codes: H04B 1/126 having multiple inputs, e.g. auxiliary antenna for receiving interfering signal aerials in general H01Q
• CPC Class Codes: H04B 1/7105 Joint detection techniques, e.g. linear detectors
• CPC Class Codes: H04B 1/7107 Subtractive interference cancellation
• 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 2001/1045 Adjacent-channel interference
• CPC Class Codes: H04B 2201/70719 CDMA2000
• CPC Class Codes: H04B 2201/70979 Fat finger issues in RAKE receivers
• CPC Class Codes: H04B 7/0678 using different spreading codes between antennas code allocation H04J13/16
• CPC Class Codes: H04B 7/0891 Space-time diversity rake receivers H04B1/7115; space-time decoding H04L1/0631
• CPC Class Codes: H04J 13/0022 PN, e.g. Kronecker
• CPC Class Codes: H04J 13/20 having an orthogonal variable spreading factor [OVSF]

Abstract

A multi-mode receiver includes a channel decomposition module (e.g., a Rake receiver) for separating a received signal into multipath components, an interference selector for selecting interfering paths and subchannels, a synthesizer for synthesizing interference signals from selected subchannel symbol estimates, and an interference canceller for cancelling selected interference in the received signal. At least one of the channel decomposition module, the synthesizer, and the interference canceller are configurable for processing multi-mode signals.

Claims

1. A multi-mode receiver, comprising:

a channel decomposition module configured for performing a decomposition of a communication channel into a plurality of channel components;

a baseband receiver comprising an upstream baseband processor and a downstream baseband processor; and

an interference canceller coupled between the upstream baseband processor and the downstream baseband processor;

wherein at least one of the channel decomposition module, the baseband receiver, and the interference cancellation system is configurable for processing multi-mode signals.

2. The receiver recited in claim 1, wherein the interference canceller comprises:

an interference selector coupled to the receive baseband processor and configured for selecting subchannels that are likely to contribute interference to at least one signal of interest, for producing at least one selected interference symbol;

a synthesizer configured to synthesize a synthesized interference signal from the at least one selected interference symbol;

a channel emulator configured to produce an estimated interference signal from the synthesized interference signal;

a second upstream baseband processor coupled to the channel emulator and configured for producing an estimated received interference signal from the estimated interference signal; and

a canceller configured for orthogonally or obliquely projecting a signal output from the baseband receiver onto a subspace that is orthogonal or oblique to a subspace of the estimated received interference signal.

3. The receiver recited in claim 2, wherein the synthesizer is configured for producing a linear combination of synthesized interference signals.

4. The receiver recited in claim 2, wherein the interference selector is configured to recursively determine subsets of channels that may be used in subtractions or in projections of increasing dimension.

5. The receiver recited in claim 1, wherein the interference canceller comprises a subtractive canceller.

6. The receiver recited in claim 1, wherein the baseband receiver further comprises a receiver filter matched to a transmit filter.

7. The receiver recited in claim 1, wherein the channel decomposition module includes a physical channel identification module configured to estimate a multipath profile.

8. The receiver recited in claim 1, wherein the multi-mode signals include at least one of a set of signals, including signals corresponding to multiple transmission protocols, signals corresponding to multiple variations of a particular transmission protocol, and signals corresponding to multiple receiver signal-processing techniques.

9. The receiver recited in claim 1, wherein the interference canceller is configured to process a sequence of estimated symbols.

10. The receiver recited in claim 1, wherein at least one of the synthesizer, the channel emulator, and the second upstream baseband processor is configured to synchronize the estimated received interference signal with the signal output from the baseband receiver.

11. The receiver recited in claim 1, wherein the channel decomposition module is configured to track signals that are identified as at least one of strong sources and strong multipath components.

12. The receiver recited in claim 1, wherein the baseband receiver comprises a Rake receiver and an equalizer, the baseband receiver being configured for selecting at least one of the Rake receiver and the equalizer for processing a received baseband signal.

13. The receiver recited in claim 1 configured to operate in at least one of a transmit-diversity system and a receive-diversity system.

14. The receiver recited in claim 1, wherein the interference canceller includes an interference-cancelled signal combiner.

15. The receiver recited in claim 14, wherein the interference-cancelled signal combiner is configured to combine the outputs over a plurality of subchannels and multipaths.

16. The receiver recited in claim 14, wherein the interference-cancelled signal combiner is configured to perform at least one of Maximal Ratio Combining, Equal Gain Combining, Minimum Mean Squared Error Combining, Minimum Variance Unbiased Combining, and Selection Combining.

17. The receiver recited in claim 1 configured to operate in at least one of a base station and a handset.

18. The receiver recited in claim 1 integrated in a chipset.

19. The receiver recited in claim 1, wherein at least one of the channel decomposition module, the baseband receiver, and the interference cancellation system is configurable for processing a plurality of signal types of a set of signals, the set including GSM signals, CDMA signals, W-CDMA signals, and OFDM signals.

20. The receiver recited in claim 1, wherein at least one of the channel decomposition module, the baseband receiver, and the interference cancellation system is configurable for processing a plurality of signal types of a set of signals, the set including CDMA signals, W-CDMA signals, and OFDM signals.

21. An interference cancellation system configurable to operate in a multi-mode receiver, comprising:

a means for performing decomposition of a communication channel into a plurality of channel components;

a means for performing baseband processing, comprising a means for performing upstream baseband processing and a means for performing downstream baseband processing; and

a means for cancelling interference;

wherein at least one of the means for performing decomposition, the means for performing baseband processing, and the means for cancelling interference is configurable for processing multi-mode signals.

22. The interference cancellation system recited in claim 21, wherein the means for cancelling interference further comprises:

a means for selecting subchannels that are likely to contribute interference to at least one signal of interest, for producing at least one selected interference symbol;

a means for synthesizing a synthesized interference signal from the at least one selected interference symbol;

a means for performing channel emulation to produce an estimated interference signal from the synthesized interference signal;

a second means for performing upstream baseband processing to produce an estimated received interference signal from the estimated interference signal; and

a means for orthogonally or obliquely projecting a signal output from the means for performing baseband processing onto an interference subspace of the estimated received interference signal.

23. The interference cancellation system recited in claim 22, wherein the means for synthesizing further comprises at least one means for compensating for multipath delay in a received baseband signal.

24. The interference cancellation system recited in claim 22, further comprising a means for producing a linear combination of synthesized interference signals.

25. The interference cancellation system recited in claim 22, wherein the means for orthogonally or obliquely projecting includes at least one of a means for performing orthogonal projection and a means for performing oblique projection.

26. The interference cancellation system recited in claim 22, wherein the means for selecting is configured to recursively determine subsets of channels that may be used in subtractions or in projections of increasing dimension.

27. The interference cancellation system recited in claim 22, wherein the means for synthesizing further comprises a means for imparting a delay to the at least one estimated interference signal in order to synchronize the at least one synthesized interference signal with a received baseband signal.

28. The interference cancellation system recited in claim 21, wherein the means for selecting includes a means for combining outputs from the means for cancelling.

29. The interference cancellation system recited in claim 28, wherein the means for combining outputs is configured to combine the outputs over a plurality of subchannels and multipaths.

30. The interference cancellation system recited in claim 28, wherein means for combining outputs is configured to perform at least one of Maximal Ratio Combining, Equal Gain Combining, Minimum Mean Squared Error Combining, Minimum Variance Unbiased Combining, and Selection Combining.

31. The interference cancellation system recited in claim 21, wherein the multi-mode signals include at least one of a set of signals, including signals corresponding to multiple transmission protocols, signals corresponding to multiple variations of a particular transmission protocol, and signals corresponding to multiple receiver signal-processing techniques.

32. The interference cancellation system recited in claim 21, wherein the means for cancelling interference is configured to process sequences of estimated symbols.

33. The interference cancellation system recited in claim 21 configured to operate in at least one of a transmit-diversity system and a receive-diversity system.

34. The interference cancellation system recited in claim 21, wherein the means for performing baseband processing comprises a means for performing Rake reception and a means for equalizing, the means for performing baseband processing being configured for selecting at least one of the means for performing Rake reception and the means for equalizing for processing a received baseband signal.

35. The interference cancellation system recited in claim 21, wherein at least one of the means for performing decomposition, the means for performing baseband processing, and the means for cancelling interference is configurable for processing a plurality of signal types of a set of signals, the set including GSM signals, CDMA signals, W-CDMA signals, and OFDM signals.

36. The interference cancellation system recited in claim 21, wherein at least one of the means for performing decomposition, the means for performing baseband processing, and the means for cancelling interference is configurable for processing a plurality of signal types of a set of signals, the set including CDMA signals, W-CDMA signals, and OFDM signals.

37. An interference cancellation method configurable to operate in a multi-mode receiver, comprising:

providing for decomposing a communication channel into a plurality of channel components;

providing for receiver baseband processing;

providing for interference cancellation; and

providing for adapting at least one of providing for decomposing, providing for receiver baseband processing, and providing for interference cancellation to process multi-mode signals.

38. The interference cancellation method recited in claim 37, wherein providing for interference cancellation comprises:

providing for selecting subchannels that are likely to contribute interference to at least one signal of interest, for producing at least one selected interference symbol,

providing for synthesizing at least one synthesized interference signal from the at least one selected interference symbol, and

providing for projecting out the at least one synthesized interference signal from a received baseband signal.

39. The interference cancellation method recited in claim 38, wherein providing for selecting subchannels includes recursively determining subsets of channels that may be used in subtractions or in projections of increasing dimension.

40. The interference cancellation method recited in claim 38, wherein providing for selecting subchannels includes tracking signals that are identified as at least one of strong sources and strong multipath components.

41. The interference cancellation method recited in claim 38, wherein providing for synthesizing further comprises processing the at least one synthesized interference signal to emulate predetermined channel distortions in the received baseband signal.

42. The interference cancellation method recited in claim 38, wherein providing for synthesizing includes imparting a delay to the at least one estimated interference signal in order to synchronize the at least one synthesized interference signal with the received baseband signal.

43. The interference cancellation method recited in claim 38, wherein providing for synthesizing includes imparting channel distortions onto the at least one synthesized interference signal.

44. The interference cancellation method recited in claim 38, wherein providing for projecting is configured to perform at least one of an orthogonal projection and an oblique projection.

45. The interference cancellation method recited in claim 38, further comprising providing for combining a plurality of the at least one synthesized interference signal for producing a linear combination of synthesized interference signals.

46. The interference cancellation method recited in claim 37, wherein providing for decomposing includes estimating a multipath profile.

47. The interference cancellation method recited in claim 37, wherein the multi-mode signals include at least one of a set of signals, including signals corresponding to multiple transmission protocols, signals corresponding to multiple variations of a particular transmission protocol, and signals corresponding to multiple receiver signal-processing techniques.

48. The interference cancellation method recited in claim 37 configured to operate in at least one of a transmit-diversity system and a receive-diversity system.

49. The interference cancellation method recited in claim 37, wherein providing for cancelling interference includes producing a projection operator or performing subtractive cancellation.

50. The interference cancellation method recited in claim 37, wherein providing for cancelling interference includes processing sequences of estimated symbols.

51. The interference cancellation method recited in claim 37, wherein providing for cancelling interference includes combining a plurality of interference-cancelled signals.

52. The interference cancellation method recited in claim 51, wherein combining includes combining the plurality of interference-cancelled signals over a plurality of subchannels and multipaths.

53. The interference cancellation method recited in claim 51, wherein combining includes at least one of Maximal Ratio Combining, Equal Gain Combining, Minimum Mean Squared Error Combining, Minimum Variance Unbiased Combining, and Selection Combining.

54. A digital computer system programmed to perform the method recited in claim 37.

55. A computer-readable medium storing a computer program implementing the method of claim 37.

56. A base station configured to perform the method of claim 37.

57. A handset configured to perform the method of claim 37.

58. A chipset configured to perform the method of claim 37.

59. The interference cancellation method recited in claim 37, wherein at least one of providing for decomposing, providing for receiver baseband processing, and providing for interference cancellation is configurable for processing a plurality of signal types of a set of signals, the set including GSM signals, CDMA signals, W-CDMA signals, and OFDM signals.

60. The interference cancellation method recited in claim 37, wherein at least one of providing for decomposing, providing for receiver baseband processing, and providing for interference cancellation is configurable for processing a plurality of signal types of a set of signals, the set including CDMA signals, W-CDMA signals, and OFDM signals.

61. A handset, comprising:

a channel decomposition module configured for performing a decomposition of a communication channel into a plurality of channel components;

a baseband receiver comprising an upstream baseband processor and a downstream baseband processor; and

an interference canceller coupled between the upstream baseband processor and the downstream baseband processor;

wherein at least one of the channel decomposition module, the baseband receiver, and the interference cancellation system is configurable for processing multi-mode signals.

62. The handset recited in claim 61, wherein the interference canceller comprises:

an interference selector coupled to the receive baseband processor and configured for selecting subchannels that are likely to contribute interference to at least one signal of interest, for producing at least one selected interference symbol;

a synthesizer configured to synthesize a synthesized interference signal from the at least one selected interference symbol;

a channel emulator configured to produce an estimated interference signal from the synthesized interference signal;

a second upstream baseband processor coupled to the channel emulator and configured for producing an estimated received interference signal from the estimated interference signal; and

a canceller configured for orthogonally or obliquely projecting a signal output from the baseband receiver onto a subspace that is orthogonal or oblique to a subspace of the estimated received interference signal.

63. The handset recited in claim 62, wherein the synthesizer is configured for producing a linear combination of synthesized interference signals.

64. The handset recited in claim 62, wherein the interference selector is configured to recursively determine subsets of channels that may be used in subtractions or in projections of increasing dimension.

65. The handset recited in claim 61, wherein the baseband receiver further comprises a combiner configured for combining a plurality of signal outputs from the baseband receiver.

66. The handset recited in claim 61, wherein the interference canceller comprises a subtractive canceller.

67. The handset recited in claim 61, wherein the channel decomposition module includes a physical channel identification module configured to estimate a multipath profile.

68. The handset recited in claim 61, wherein the multi-mode signals include at least one of a set of signals, including signals corresponding to multiple transmission protocols, signals corresponding to multiple variations of a particular transmission protocol, and signals corresponding to multiple receiver signal-processing techniques.

69. The handset recited in claim 61, wherein the interference canceller is configured to process a sequence of estimated symbols.

70. The handset recited in claim 61, wherein at least one of the synthesizer, the channel emulator, and the second upstream baseband processor is configured to synchronize the estimated received interference signal with the signal output from the baseband receiver.

71. The handset recited in claim 61, wherein the channel decomposition module is configured to track signals that are identified as at least one of strong sources and strong multipath components.

72. The handset recited in claim 61, wherein the baseband receiver comprises a Rake receiver and an equalizer, the baseband receiver being configured for selecting at least one of the Rake receiver and the equalizer for processing a received baseband signal.

73. The handset recited in claim 61 configured to operate in at least one of a transmit-diversity system and a receive-diversity system.

74. The handset recited in claim 61, wherein the interference canceller includes an interference-cancelled signal combiner.

75. The handset recited in claim 74, wherein the interference-cancelled signal combiner is configured to combine the outputs over a plurality of subchannels and multipaths.

76. The handset recited in claim 74, wherein the interference-cancelled signal combiner is configured to perform at least one of Maximal Ratio Combining, Equal Gain Combining, Minimum Mean Squared Error Combining, Minimum Variance Unbiased Combining, and Selection Combining.

77. The handset recited in claim 61, wherein at least one of the channel decomposition module, the baseband receiver, and the interference cancellation system is configurable for processing a plurality of signal types of a set of signals, the set including GSM signals, CDMA signals, W-CDMA signals, and OFDM signals.

78. The handset recited in claim 61, wherein at least one of the channel decomposition module, the baseband receiver, and the interference cancellation system is configurable for processing a plurality of signal types of a set of signals, the set including CDMA signals, W-CDMA signals, and OFDM signals.

79. A chipset, comprising:

a channel decomposition module configured for performing a decomposition of a communication channel into a plurality of channel components;

a baseband receiver comprising an upstream baseband processor and a downstream baseband processor; and

an interference canceller coupled between the upstream baseband processor and the downstream baseband processor;

wherein at least one of the channel decomposition module, the baseband receiver, and the interference cancellation system is configurable for processing multi-mode signals.

80. The chipset recited in claim 79, wherein the interference canceller comprises:

an interference selector coupled to the receive baseband processor and configured for selecting subchannels that are likely to contribute interference to at least one signal of interest, for producing at least one selected interference symbol;

a synthesizer configured to synthesize a synthesized interference signal from the at least one selected interference symbol;

a channel emulator configured to produce an estimated interference signal from the synthesized interference signal;

a second upstream baseband processor coupled to the channel emulator and configured for producing an estimated received interference signal from the estimated interference signal; and

a canceller configured for orthogonally or obliquely projecting a signal output from the baseband receiver onto a subspace that is orthogonal or oblique to a subspace of the estimated received interference signal.

81. The chipset recited in claim 80, wherein the synthesizer is configured for producing a linear combination of synthesized interference signals.

82. The chipset recited in claim 80, wherein the interference selector is configured to recursively determine subsets of channels that may be used in subtractions or in projections of increasing dimension.

83. The chipset recited in claim 79, wherein the baseband receiver further comprises a combiner configured for combining a plurality of signal outputs from the baseband receiver.

84. The chipset recited in claim 79, wherein the interference canceller comprises a subtractive canceller.

85. The chipset recited in claim 79, wherein the channel decomposition module includes a physical channel identification module configured to estimate a multipath profile.

86. The chipset recited in claim 79, wherein the multi-mode signals include at least one of a set of signals, including signals corresponding to multiple transmission protocols, signals corresponding to multiple variations of a particular transmission protocol, and signals corresponding to multiple receiver signal-processing techniques.

87. The chipset recited in claim 79, wherein the interference canceller is configured to process a sequence of estimated symbols.

88. The chipset recited in claim 79, wherein at least one of the synthesizer, the channel emulator, and the second upstream baseband processor is configured to synchronize the estimated received interference signal with the signal output from the baseband receiver.

89. The chipset recited in claim 79, wherein the channel decomposition module is configured to track signals that are identified as at least one of strong sources and strong multipath components.

90. The chipset recited in claim 79, wherein the baseband receiver comprises a Rake receiver and an equalizer, the baseband receiver being configured for selecting at least one of the Rake receiver and the equalizer for processing a received baseband signal.

91. The chipset recited in claim 79 configured to operate in at least one of a transmit-diversity system and a receive-diversity system.

92. The chipset recited in claim 79, wherein the interference canceller includes an interference-cancelled signal combiner.

93. The chipset recited in claim 92, wherein the interference-cancelled signal combiner is configured to combine the outputs over a plurality of subchannels and multipaths.

94. The chipset recited in claim 92, wherein the interference-cancelled signal combiner is configured to perform at least one of Maximal Ratio Combining, Equal Gain Combining, Minimum Mean Squared Error Combining, Minimum Variance Unbiased Combining, and Selection Combining.

95. The chipset recited in claim 79, wherein at least one of the channel decomposition module, the baseband receiver, and the interference cancellation system is configurable for processing a plurality of signal types of a set of signals, the set including GSM signals, CDMA signals, W-CDMA signals, and OFDM signals.

96. The chipset recited in claim 79, wherein at least one of the channel decomposition module, the baseband receiver, and the interference cancellation system is configurable for processing a plurality of signal types of a set of signals, the set including CDMA signals, W-CDMA signals, and OFDM signals.