Interference cancellation in adjoint operators for communication receivers

• US 20060153283A1
• Filed: 01/13/2005
• Published: 07/13/2006
• Est. Priority Date: 01/13/2005
• Status: Abandoned Application

• Current Assignee: Rambus Inc.
• Original Assignee: Rambus Inc.
• Inventors: Scharf, Louis L., Shattil, Steve J.
• Application Number:
  US11/035,141
• Publication Number:
  US 20060153283A1
• Time in Patent Office: Days
• US Class Current: 375/148
• CPC Class Codes: H04B 1/7107 Subtractive interference cancellation
• CPC Class Codes: H04L 2025/03414 Multicarrier

Abstract

A receiver in a wireless communication system comprises a reverse transform configured to produce a vector of baseband signal values, and a projection canceller configured to project the vector of baseband signal values onto at least one subspace that is substantially orthogonal to an interference subspace. The reverse transform may be adjoint to a forward transform employed by at least one transmitter in the wireless communication system. The combination of interference cancellation with one or more receiver operations may be a substantially adjoint operation relative to one or more transmitter operators and channel-propagation effects. The reverse transform may include a Fourier transform, a wavelet transform, or any other well known invertible transforms. Reverse transforms may include spread-spectrum multiple-access coding and may be implemented in systems configured to perform single-input, multiple output or multiple-input, multiple-output operations. Interference components may be selected in a projection canceller relative to predetermined ratios of interference in the received signal.

Claims

1. An apparatus adapted to receive a plurality of transmitted signals, comprising:

a. a reverse transform configured to produce a vector of baseband signal values, and

b. a projection canceller coupled to said reverse transform, said projection canceller configured to project the vector of baseband signal values onto at least one subspace that is substantially orthogonal to an interference subspace.

2. The apparatus recited in claim 1 further comprising an interference selector coupled to said projection canceller, said interference selector configured to select at least one interference component to include in the interference subspace.

3. The apparatus recited in claim 2 wherein said interference selector is configured to employ at least one of an analytically determined interference distribution and a measured interference distribution when selecting the at least one interference component.

4. The apparatus recited in claim 2 wherein said interference selector is configured to select the at least one interference component based on at least one of known channel measurements and known spreading codes.

5. The apparatus recited in claim 2 wherein said interference selector is configured to select the at least one interference component to optimize at least one signal-quality parameter of at least one received signal.

6. The apparatus recited in claim 5 wherein said interference selector is configured to select the at least one interference component as part of an iterative process for optimizing the at least one signal-quality parameter of the at least one received signal.

7. The apparatus recited in claim 2 wherein said interference selector is configured to select the at least one interference component to optimize at least one complexity/performance trade-off.

8. The apparatus recited in claim 2 wherein said interference selector is configured to select the at least one interference component relative to its correlation with at least one desired signal.

9. The apparatus recited in claim 2 wherein said interference selector is configured to select the at least one interference component with respect to at least one predetermined delay threshold.

10. The apparatus recited in claim 1 wherein the reverse transform includes at least one of a Fourier transform, a wavelet transform, a Walsh transform, and a Hankel transform.

11. The apparatus recited in claim 1 wherein the reverse transform includes at least one of a block transform, a sliding transform, a passband filter bank, and a quadrature-mirror filter bank.

12. The apparatus recited in claim 1 wherein the reverse transform includes an antenna array.

13. The apparatus recited in claim 12 wherein the antenna array includes at least one of a set of antennas including a plurality of spatially separated antennas and a plurality of differently polarized antennas.

14. The apparatus recited in claim 12 wherein the antenna array includes at least one of a plurality of filter banks and a plurality of Rake receivers.

15. The apparatus recited in claim 1 wherein the reverse transform includes at least one of an equalizer and a matched filter.

16. The apparatus recited in claim 1 wherein the reverse transform comprises a despreading operator.

17. The apparatus recited in claim 16 wherein the despreading operator is adapted to decode at least one of a set of spreading codes, including Hadamard-Walsh codes, complex codes derived from DFT coefficients, Frank-Zadoff codes, and Chu sequences.

18. The apparatus recited in claim 1 wherein the reverse transform comprises a square-matrix operator.

19. The apparatus recited in claim 1 wherein the reverse transform is adapted to recover transmitted data symbols mapped onto at least one signal subspace, including a code subspace, a frequency subspace, a path-diversity subspace, a wavelet subspace, and a polarization subspace.

20. The apparatus recited in claim 1 wherein the reverse transform comprises a synthesis operator represented by a polyphase matrix.

21. The apparatus recited in claim 1 wherein the reverse transform comprises a plurality of orthogonal basis functions.

22. The apparatus recited in claim 1 wherein at least one of the reverse transform and the projection canceller is adaptable to changing channel conditions.

23. The apparatus recited in claim 1 wherein the reverse transform and the projection canceller are implemented via an enhanced reverse-transform operator.

24. The apparatus recited in claim 1 wherein the projection canceller is configured to produce at least one projection operator having a form expressed by at least one of P_s^⊥

=I−

S(S^TS)<sup>−

1</sup>S^T and P_s^⊥

=I−

S(S^HS)<sup>−

1</sup>S^H, where P_s^⊥

is a projection operator, I is an identity matrix, S is an interference matrix, S^T is a transpose of the interference matrix, and S^H is a conjugate transpose of the interference matrix.

25. The apparatus recited in claim 24 wherein the projection operator includes one or more regularisation parameters.

26. The apparatus recited in claim 24 wherein the projection operator is configured to optimize at least one received signal parameter.

27. The apparatus recited in claim 24 wherein the projection operator is adaptable to at least one of changes in the number of basis functions and changes in the basis function length.

28. The apparatus recited in claim 24 wherein the projection operator is configured to orthogonalize a plurality of column vectors in the interference matrix S.

29. The apparatus recited in claim 24 wherein the projection operator is configured to generate the interference matrix S from a linear combination of interference vector subspaces.

30. The apparatus recited in claim 1 wherein the plurality of transmitted signals includes at least one of a set of signals, including cdmaOne, cdma2000, 1xRTT, cdma 1xEV-DO, cdma 1xEV-DV, cdma2000 3x, WCDMA, Broadband CDMA, UMTS, GPS, OFDM, MC-CDMA, Spread-OFDM, HSDPA, and frequency-hopped signals.

31. A handset adapted to receive a plurality of transmitted signals, comprising:

a. a reverse transform configured to produce a vector of baseband signal values, and

b. a projection canceller coupled to said reverse transform, said projection canceller configured to project the vector of baseband signal values onto at least one subspace that is substantially orthogonal to an interference subspace.

32. The handset recited in claim 31 further comprising an interference selector coupled to said projection canceller, said interference selector configured to select at least one interference component to include in the interference subspace.

33. The handset recited in claim 32 wherein said interference selector is configured to employ at least one of an analytically determined interference distribution and a measured interference distribution when selecting the at least one interference component.

34. The handset recited in claim 32 wherein said interference selector is configured to select the at least one interference component based on at least one of known channel measurements and known spreading codes.

35. The handset recited in claim 32 wherein said interference selector is configured to select the at least one interference component to optimize at least one signal-quality parameter of at least one received signal.

36. The handset recited in claim 35 wherein said interference selector is configured to select the at least one interference component as part of an iterative process for optimizing the at least one signal-quality parameter of the at least one received signal.

37. The handset recited in claim 32 wherein said interference selector is configured to select the at least one interference component to optimize at least one complexity/performance trade-off.

38. The handset recited in claim 32 wherein said interference selector is configured to select the at least one interference component relative to its correlation with at least one desired signal.

39. The handset recited in claim 32 wherein said interference selector is configured to select the at least one interference component with respect to at least one predetermined delay threshold.

40. The handset recited in claim 31 wherein the reverse transform includes at least one of a Fourier transform, a wavelet transform, a Walsh transform, and a Hankel transform.

41. The handset recited in claim 31 wherein the reverse transform includes at least one of a block transform, a sliding transform, a passband filter bank, and a quadrature-mirror filter bank.

42. The handset recited in claim 31 wherein the reverse transform includes an antenna array.

43. The handset recited in claim 42 wherein the antenna array includes at least one of a set of antennas including a plurality of spatially separated antennas and a plurality of differently polarized antennas.

44. The handset recited in claim 42 wherein the antenna array includes at least one of a plurality of filter banks and a plurality of Rake receivers.

45. The handset recited in claim 31 wherein the reverse transform includes at least one of an equalizer and a matched filter.

46. The handset recited in claim 31 wherein the reverse transform comprises a despreading operator.

47. The handset recited in claim 46 wherein the despreading operator is adapted to decode at least one of a set of spreading codes, including Hadamard-Walsh codes, complex codes derived from DFT coefficients, Frank-Zadoff codes, and Chu sequences.

48. The handset recited in claim 31 wherein the reverse transform comprises a square-matrix operator.

49. The handset recited in claim 31 wherein the reverse transform is adapted to recover transmitted data symbols mapped onto at least one signal subspace, including a code subspace, a frequency subspace, a path-diversity subspace, a wavelet subspace, and a polarization subspace.

50. The handset recited in claim 31 wherein the reverse transform comprises a synthesis operator represented by a polyphase matrix.

51. The handset recited in claim 31 wherein the reverse transform comprises a plurality of orthogonal basis functions.

52. The handset recited in claim 31 wherein at least one of the reverse transform and the projection canceller is adaptable to changing channel conditions.

53. The handset recited in claim 31 wherein the reverse transform and the projection canceller are implemented via an enhanced reverse-transform operator.

54. The handset recited in claim 31 wherein the projection canceller is configured to produce at least one projection operator having a form expressed by at least one of P_s^⊥

=I−

S(S^TS)<sup>−

1</sup>S^T and P_s^⊥

=I−

S(S^HS)<sup>−

1</sup>S^H, where P_s^⊥

is a projection operator, I is an identity matrix, S is an interference matrix, S^T is a transpose of the interference matrix, and S^H is a conjugate transpose of the interference matrix.

55. The handset recited in claim 54 wherein the projection operator includes one or more regularisation parameters.

56. The handset recited in claim 54 wherein the projection operator is configured to optimize at least one received signal parameter.

57. The handset recited in claim 54 wherein the projection operator is adaptable to at least one of changes in the number of basis functions and changes in the basis function length.

58. The handset recited in claim 54 wherein the projection operator is configured to orthogonalize a plurality of column vectors in the interference matrix S.

59. The handset recited in claim 54 wherein the projection operator is configured to generate the interference matrix S from a linear combination of interference vector subspaces.

60. The handset recited in claim 31 wherein the plurality of transmitted signals includes at least one of a set of signals, including cdmaOne, cdma2000, 1xRTT, cdma 1xEV-DO, cdma 1xEV-DV, cdma2000 3x, WCDMA, Broadband CDMA, UMTS, GPS, OFDM, MC-CDMA, Spread-OFDM, HSDPA, and frequency-hopped signals.

61. A communication system comprising:

a. a transmitter configured to couple at least one transmit signal into a communication channel, and

b. a receiver configured to couple the at least one transmit signal from the communication channel to produce at least one received signal, the receiver comprising;

i. a reverse transform configured to process the at least one received signal to produce a vector of baseband signal values, and

ii. a projection canceller coupled to said reverse transform, said projection canceller configured to project the vector of baseband signal values onto at least one subspace that is substantially orthogonal to an interference subspace.

62. The communication system recited in claim 61 wherein the transmitter is configured to map a plurality of data symbols onto at least one signal subspace.

63. The communication system recited in claim 61 wherein the transmitter includes a forward transform.

64. The communication system recited in claim 63 wherein the forward transform is configured to employ precoding.

65. The communication system recited in claim 63 wherein the forward transform is configured to employ at least one set of spreading codes, including orthogonal and non-orthogonal spreading codes.

66. The communication system recited in claim 63 wherein the forward transform is configured to employ spreading.

67. The communication system recited in claim 63 wherein the forward transform is configured to structure interference in the at least one received signal.

68. The communication system recited in claim 63 wherein the forward transform is further configured to employ diversity to decorrelate highly correlated signal spaces.

69. The communication system recited in claim 63 wherein the forward transform and the reverse transform are configured to employ biorthogonal bases.

70. The communication system recited in claim 63 wherein the forward transform is operable in a first signal space and the reverse transform is operable in a second signal space wherein the second signal space is different from the first signal space.

71. The communication system recited in claim 63 wherein the forward transform is adapted to produce a multicarrier signal, wherein the at least one transmit signal comprises the multicarrier signal.

72. The communication system recited in claim 71 wherein the forward transform is configured to provide the multicarrier signal with at least one of frequency interleaving and frequency hopping.

73. The communication system recited in claim 71 wherein the forward transform is configured to provide the multicarrier signal with at least one spreading code.

74. The communication system recited in claim 73 wherein the forward transform is configured to provide the at least one spreading code with at least one of a set of complex weights, including pulse-shaping coefficients, spectral-smoothing functions, and PAPR-reduction codes.

75. The communication system recited in claim 63 wherein the at least one transmit signal comprises a plurality of transmit signals and the forward transform is configured to provide each of a plurality of transmit signals with linearly independent spreading gains.

76. The communication system recited in claim 63 wherein the at least one transmit signal comprises a plurality of transmit signals and the forward transform is configured to condition the communication channel to impart linearly independent channel distortions to the plurality of transmit signals.

77. The communication system recited in claim 61 wherein the transmitter further comprises an interference-structuring module configured to distribute interference across at least one signal subspace in a predetermined manner.

78. The communication system recited in claim 77 wherein the interference-structuring module is configured to perform at least one of spreading-code selection, precoding, frequency interleaving, array processing, and polarization division multiplexing.

79. The communication system recited in claim 77 further comprising a communicative coupling between the interference-structuring module and the projection canceller.

80. A method for processing a composite signal comprising at least one signal of interest, the method comprising the steps of:

(a) providing for performing a reverse transform on the composite signal to produce a plurality of baseband signal portions; and

(b) providing for projecting a signal space corresponding to the plurality of baseband signal portions onto a signal space substantially orthogonal to an interference signal space for canceling interference from the at least one signal of interest.

81. The method recited in claim 80 wherein providing for projecting a signal space comprises providing for interference selection for selecting at least one interference component to include in the interference signal space.

82. The method recited in claim 81 wherein providing for interference selection includes employing at least one of an analytically determined interference distribution and a measured interference distribution for selecting the at least one interference component.

83. The method recited in claim 81 wherein providing for interference selection includes selecting the at least one interference component based on at least one of known channel measurements and known transmit spreading codes.

84. The method recited in claim 81 wherein providing for interference selection includes selecting the at least one interference component to improve at least one signal-quality parameter of at least one received signal.

85. The method recited in claim 84 wherein providing for interference selection is part of an iterative process to improve the at least one signal-quality parameter of at least one received signal.

86. The method recited in claim 81 wherein providing for interference selection includes selecting the at least one interference component to provide at least one predetermined complexity/performance trade-off.

87. The method recited in claim 81 wherein providing for interference selection includes selecting the at least one interference component relative to its correlation with the at least one signal of interest.

88. The method recited in claim 81 wherein providing for interference selection includes selecting the at least one interference component relative to at least one predetermined delay threshold.

89. The method recited in claim 80 wherein providing for performing the reverse transform includes performing at least one of a Fourier transform, a wavelet transform, a Walsh transform, and a Hankel transform.

90. The method recited in claim 80 wherein providing for performing the reverse transform includes performing at least one of a block transform, a sliding transform, a passband filtering operation, and a quadrature-mirror filtering operation.

91. The method recited in claim 80 wherein providing for performing the reverse transform includes receiving the composite signal with an antenna array.

94. The method recited in claim 80 wherein providing for performing the reverse transform includes at least one of equalizing and matched filtering the composite signal.

95. The method recited in claim 80 wherein providing for performing the reverse transform comprises providing for applying a despreading operator.

96. The method recited in claim 95 wherein providing for applying the despreading operator includes decoding at least one of a set of spreading codes, including Hadamard-Walsh codes, complex codes derived from DFT coefficients, Frank-Zadoff codes, and Chu sequences.

97. The method recited in claim 80 wherein providing for performing the reverse transform comprises providing for applying a square-matrix operator.

98. The method recited in claim 80 wherein providing for performing the reverse transform includes recovering transmitted data symbols mapped onto at least one signal subspace, including a code subspace, a frequency subspace, a path-diversity subspace, a wavelet sub space, and a polarization sub sp ace.

99. The method recited in claim 80 wherein providing for performing the reverse transform comprises performing a synthesis operation represented by a polyphase matrix.

100. The method recited in claim 80 wherein providing for performing the reverse transform comprises employing an operator having a plurality of orthogonal basis functions.

101. The method recited in claim 80 wherein at least one of providing for performing the reverse transform and providing for projecting a signal space is adapted to changing channel conditions.

102. The method recited in claim 80 wherein providing for performing the reverse transform and providing for projecting a signal space are implemented via providing for an enhanced reverse-transform operation.

103. The method recited in claim 80 wherein providing for projecting a signal space includes producing at least one projection operator having a form comprising at least one of P_s^⊥

=I−

S(S^TS)<sup>−

1</sup>S^T and P_s^⊥

=I−

S(S^HS)<sup>−

1</sup>S^H, where P_s^⊥

is a projection operator, I is an identity matrix, S is an interference matrix, S^T is a transpose of the interference matrix, and S^H is a conjugate transpose of the interference matrix.

104. The method recited in claim 103 wherein the projection operator includes one or more regularisation parameters.

105. The method recited in claim 103 wherein providing for projecting a signal space includes configuring the projection operator to optimize at least one received signal parameter.

106. The method recited in claim 103 wherein providing for projecting a signal space includes adapting the projection operator to at least one of changes in the number of basis functions and changes in the basis function length.

107. The method recited in claim 103 wherein providing for projecting a signal space includes orthogonalizing a plurality of column vectors in the interference matrix S.

108. The method recited in claim 103 wherein providing for projecting a signal space includes generating the interference matrix S from a linear combination of interference vector subspaces.

109. The method recited in claim 80 wherein the composite signal includes at least one of a set of signals, including cdmaOne, cdma2000, 1xRTT, cdma 1xEV-DO, cdma 1xEV-DV, cdma2000 3x, WCDMA, Broadband CDMA, UMTS, GPS, OFDM, MC-CDMA, Spread-OFDM, HSDPA, and frequency-hopped signals.

141. A digital computer system programmed to perform the method recited in claim 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, or 140.

142. A computer-readable medium storing a computer program implementing the method of claim 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, or 140.

92. The method recited in claim 92 wherein the antenna array includes at least one of a set of antennas including a plurality of spatially separated antennas and a plurality of differently polarized antennas.

93. The method recited in claim 93 wherein the antenna array further includes at least one of a plurality of filter banks and a plurality of Rake receivers.

110. A method for decomposing a composite signal comprising a plurality of signals of interest, the method comprising:

(a) providing for performing a reverse transform on the composite signal to produce a plurality of baseband signal portions; and

(b) for at least one of the plurality of signals of interest, providing for projecting a signal space corresponding to the plurality of baseband signal portions onto a signal space substantially orthogonal to an interference signal space, the interference space not including the at least one of the plurality of signals of interest.

111. The method recited in claim 110 wherein the composite signal includes at least one interfering signal that is not one of the plurality of signals of interest, and providing for projecting a signal space includes projecting a signal space corresponding to the plurality of baseband signal portions onto a signal space substantially orthogonal to the interference signal space, the interference space including at least one of the at least one interfering signal that is not one of the plurality of signals of interest.

112. The method recited in claim 110 wherein providing for projecting a signal space comprises providing for interference selection for selecting at least one interference component to include in the interference signal space.

113. The method recited in claim 112 wherein providing for interference selection includes employing at least one of an analytically determined interference distribution and a measured interference distribution for selecting the at least one interference component.

114. The method recited in claim 112 wherein providing for interference selection includes selecting the at least one interference component based on at least one of known channel measurements and known transmit spreading codes.

115. The method recited in claim 112 wherein providing for interference selection includes selecting the at least one interference component to improve at least one signal-quality parameter of at least one received signal.

117. The method recited in claim 112 wherein providing for interference selection includes selecting the at least one interference component to improve at least one complexity/performance trade-off metric.

118. The method recited in claim 112 wherein providing for interference selection includes selecting the at least one interference component relative to its correlation with at least one of the plurality of signals of interest.

119. The method recited in claim 112 wherein providing for interference selection includes selecting the at least one interference component relative to at least one predetermined delay threshold.

120. The method recited in claim 110 wherein providing for performing the reverse transform includes performing at least one of a Fourier transform, a wavelet transform, a Walsh transform, and a Hankel transform.

121. The method recited in claim 110 wherein providing for performing the reverse transform includes performing at least one of a block transform, a sliding transform, a passband filtering operation, and a quadrature-mirror filtering operation.

122. The method recited in claim 110 wherein providing for performing the reverse transform includes receiving the composite signal with an antenna array.

123. The method recited in claim 122 wherein the antenna array includes at least one of a set of antennas including a plurality of spatially separated antennas and a plurality of differently polarized antennas.

124. The method recited in claim 122 wherein the antenna array further includes at least one of a plurality of filter banks and a plurality of Rake receivers.

125. The method recited in claim 110 wherein providing for performing the reverse transform includes at least one of equalizing and matched filtering the composite signal.

126. The method recited in claim 110 wherein providing for performing the reverse transform comprises providing for applying a despreading operator.

127. The method recited in claim 126 wherein providing for applying the despreading operator includes decoding at least one of a set of spreading codes, including Hadamard-Walsh codes, complex codes derived from DFT coefficients, Frank-Zadoff codes, and Chu sequences.

128. The method recited in claim 110 wherein providing for performing the reverse transform comprises providing for applying a square-matrix operator.

129. The method recited in claim 110 wherein providing for performing the reverse transform includes recovering transmitted data symbols mapped onto at least one signal subspace, including a code subspace, a frequency subspace, a path-diversity subspace, a wavelet subspace, and a polarization subspace.

130. The method recited in claim 110 wherein providing for performing the reverse transform comprises performing a synthesis operation represented by a polyphase matrix.

131. The method recited in claim 110 wherein providing for performing the reverse transform comprises employing an operator having a plurality of orthogonal basis functions.

132. The method recited in claim 110 wherein at least one of providing for performing the reverse transform and providing for projecting a signal space is adapted to changing channel conditions.

133. The method recited in claim 110 wherein providing for performing the reverse transform and providing for projecting a signal space are implemented via providing for an enhanced reverse-transform operation.

134. The method recited in claim 110 wherein providing for projecting a signal space includes producing at least one projection operator having a form expressed by at least one of P_s^⊥

=I−

S(S^TS)<sup>−

1</sup>S^T and P_s^⊥

=I−

S(S^HS)<sup>−

1</sup>S^H, where P_s^⊥

is a projection operator, I is an identity matrix, S is an interference matrix, S^T is a transpose of the interference matrix, and S^H is a conjugate transpose of the interference matrix.

135. The method recited in claim 134 wherein the projection operator includes one or more regularisation parameters.

136. The method recited in claim 134 wherein providing for projecting a signal space includes configuring the projection operator to optimize at least one received signal parameter.

137. The method recited in claim 134 wherein providing for projecting a signal space includes adapting the projection operator to at least one of changes in the number of basis functions and changes in the basis function length.

138. The method recited in claim 134 wherein providing for projecting a signal space includes orthogonalizing a plurality of column vectors in the interference matrix S.

139. The method recited in claim 134 wherein providing for projecting a signal space includes generating the interference matrix S from a linear combination of interference vector subspaces.

140. The method recited in claim 110 wherein the composite signal includes at least one of a set of signals, including cdmaOne, cdma2000, 1xRTT, cdma 1xEV-DO, cdma 1xEV-DV, cdma2000 3x, WCDMA, Broadband CDMA, UMTS, GPS, OFDM, MC-CDMA, Spread-OFDM, HSDPA, and frequency-hopped signals.

116. The method recited in claim 116 wherein providing for interference selection is part of an iterative process of selecting the at least one interference component to improve the at least one signal-quality parameter, providing for updating at least one of the plurality of signals of interest, and providing for determining if at least one predetermined confidence measure is satisfied.