Apparatus, method and system for correlated noise reduction in a trellis coded environment
First Claim
1. An apparatus for correlated noise reduction, the apparatus comprising:
- a trellis decoder, the trellis decoder operative to provide decoded data and a trellis error signal, the trellis error signal formed as a decision error of a selected previous state of a selected trellis path;
a linear feedforward equalizer, the linear feedforward equalizer having as input a received data signal, the linear feedforward equalizer operatively coupled to the trellis decoder for adaptation to the trellis error signal to modify a first plurality of equalization coefficients a(n); and
a noise predictor, the noise predictor operatively coupled to the linear feedforward equalizer to provide an input to the trellis decoder, the noise predictor having as input a tentative error signal, the tentative error signal formed as a difference between a tentative symbol decision by the trellis decoder and a delayed received data signal subsequent to equalization, the noise predictor operatively coupled to the trellis decoder for adaptation to the trellis error signal to modify a plurality of correlated noise reduction coefficients c(n).
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Abstract
An apparatus, method and system are provided for correlated noise reduction, in a trellis decoding environment, such as second generation HDSL, in which crosstalk impairments may be significant. The preferred embodiments provide equalization and correlated noise reduction, utilizing a training period to generate corresponding coefficients, and utilizing two different training error signals. In addition, the apparatus method and system also provide continued and adaptive correlated noise reduction during data transmission, utilizing two additional error signals, a trellis error signal and a tentative error signal. The trellis error signal is a decision error of a selected previous state of a selected trellis path, in which the selected trellis path has a smallest cumulative error of a plurality of trellis paths, and the selected previous state is preferably the immediately previous state. The tentative error signal is formed as a difference between a delayed, tentative symbol decision and a delayed received data signal subsequent to equalization, in which the delay is preferably one symbol time. The various embodiments may be utilized with trellis encoding, with or without data precoding.
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Citations
49 Claims
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1. An apparatus for correlated noise reduction, the apparatus comprising:
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a trellis decoder, the trellis decoder operative to provide decoded data and a trellis error signal, the trellis error signal formed as a decision error of a selected previous state of a selected trellis path;
a linear feedforward equalizer, the linear feedforward equalizer having as input a received data signal, the linear feedforward equalizer operatively coupled to the trellis decoder for adaptation to the trellis error signal to modify a first plurality of equalization coefficients a(n); and
a noise predictor, the noise predictor operatively coupled to the linear feedforward equalizer to provide an input to the trellis decoder, the noise predictor having as input a tentative error signal, the tentative error signal formed as a difference between a tentative symbol decision by the trellis decoder and a delayed received data signal subsequent to equalization, the noise predictor operatively coupled to the trellis decoder for adaptation to the trellis error signal to modify a plurality of correlated noise reduction coefficients c(n). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An apparatus for correlated noise reduction, the apparatus having a training mode and having a data mode, the apparatus operative during training mode to receive a training signal from a transmitter and operative during data mode to receive a data signal from the transmitter, the apparatus comprising:
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a trellis decoder, the trellis decoder having a symbol decider operative during the training mode to provide a symbol decision and a first training error signal, the first training error signal formed as a difference between the symbol decision and a received training signal subsequent to equalization and correlated noise reduction, the trellis decoder operative during the data mode to provide decoded data and a trellis error signal, the trellis error signal formed as a decision error of a selected previous state of a selected trellis path;
a linear feedforward equalizer, the linear feedforward equalizer having as input the received training signal during the training mode and a received data signal during data mode, the linear feedforward equalizer operatively coupled to the trellis decoder for adaptation to the first training error signal during training mode to provide a first plurality of coefficients a(n) for equalization and for adaptation to the trellis error signal during data mode to modify the first plurality of coefficients a(n) for adaptive equalization;
a training mode adaptive distortion and correlated noise canceller operative during training mode, an output of the training mode adaptive distortion and correlated noise canceller operatively coupled to an output of the linear feedforward equalizer to provide an input to the symbol decider of the trellis decoder, the training mode adaptive distortion and correlated noise canceller having as input a second training error signal, the second training error signal formed as a difference between the symbol decision and the received training signal subsequent to equalization, the training mode adaptive distortion and correlated noise canceller operatively coupled to the trellis decoder for adaptation to the first training error signal to provide a second plurality of coefficients b(n) for equalization and a third plurality of coefficients c(n) for correlated noise reduction; and
a data mode adaptive correlated noise canceller operative during data mode, an output of the data mode adaptive correlated noise canceller operatively coupled to a filter output of the linear feedforward equalizer to provide an input to the trellis decoder, the data mode adaptive correlated noise canceller having as input a tentative error signal, the tentative error signal formed as a difference between a tentative symbol decision and a delayed received data signal subsequent to equalization, the data mode adaptive correlated noise canceller operatively coupled to the trellis decoder for adaptation to the trellis error signal during data mode to modify the third plurality of coefficients c(n) for adaptive correlated noise reduction. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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21. A method of correlated noise reduction, the method comprising:
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(a) receiving a data signal to form a received data signal;
(b) determining a trellis error signal as a decision error of a selected previous state of a selected trellis path;
(c) equalizing a received data signal utilizing a first plurality of equalization coefficients a(n) to form an equalized data signal and modifying the first plurality of equalization coefficients a(n) in response to the trellis error signal;
(d) determining a tentative error signal as a difference between a tentative symbol decision and a delayed equalized data signal;
(e) reducing correlated noise in the equalized data signal utilizing a plurality of correlated noise reduction coefficients c(n) and modifying the plurality of correlated noise reduction coefficients c(n) in response to the trellis error signal and with input of the tentative error signal. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29)
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30. An apparatus for correlated noise reduction, the apparatus comprising:
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means for receiving a data signal to form a received data signal;
means for determining a trellis error signal as a decision error of a selected previous state of a selected trellis path;
means for equalizing a received data signal utilizing a first plurality of equalization coefficients a(n) to form an equalized data signal and modifying the first plurality of equalization coefficients a(n) in response to the trellis error signal;
means for determining a tentative error signal as a difference between a tentative symbol decision and a delayed equalized data signal;
means for reducing correlated noise in the equalized data signal utilizing a plurality of correlated noise reduction coefficients c(n) and modifying the plurality of correlated noise reduction coefficients c(n) in response to the trellis error signal and with input of the tentative error signal. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37, 38)
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39. A system for reduction of correlated noise during data transmission, the system comprising:
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a transmitter, the transmitter operative to transmit a training signal and to transmit a data signal; and
a receiver couplable to the transmitter via a communication channel, the receiver further comprising;
a trellis decoder, the trellis decoder operative to provide decoded data and a trellis error signal, the trellis error signal formed as a decision error of a selected previous state of a selected trellis path;
a linear feedforward equalizer, the linear feedforward equalizer having as input a received data signal, the linear feedforward equalizer operatively coupled to the trellis decoder for adaptation to the trellis error signal to modify a first plurality of equalization coefficients a(n); and
a noise predictor, the noise predictor operatively coupled to the linear feedforward equalizer to provide an input to the trellis decoder, the noise predictor having as input a tentative error signal, the tentative error signal formed as a difference between a tentative symbol decision by the trellis decoder and a delayed received data signal subsequent to equalization, the noise predictor operatively coupled to the trellis decoder for adaptation to the trellis error signal to modify a plurality of correlated noise reduction coefficients c(n). - View Dependent Claims (40, 41, 42, 43, 44, 45, 46, 47, 48)
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49. An apparatus for correlated noise reduction, the apparatus having a training mode and having a data mode, the apparatus operative during training mode to receive a training signal from a transmitter and operative during data mode to receive a data signal from the transmitter, the apparatus comprising:
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a trellis decoder, the trellis decoder having a symbol decider operative during the training mode to provide a symbol decision and a first training error signal, the first training error signal formed as a difference between the symbol decision and a received training signal subsequent to equalization and correlated noise reduction, the trellis decoder operative during the data mode to provide decoded data and a trellis error signal, the trellis error signal being a decision error of an immediately previous state of a selected trellis path of a plurality of trellis paths, the selected trellis path having a smallest cumulative error of the plurality of trellis paths;
a linear feedforward equalizer, the linear feedforward equalizer having as input the received training signal during the training mode and a received data signal during data mode, the linear feedforward equalizer operatively coupled to the trellis decoder for adaptation to the first training error signal during training mode to provide a first plurality of equalization coefficients a(n) and for adaptation to the trellis error signal during data mode to modify the first plurality of equalization coefficients a(n) for adaptive equalization, a decision feedback adaptive filter operatively coupled to an output of the linear feedforward equalizer and operatively coupled to the symbol decider for input of the symbol decision, for adaptation to the first training error signal and to provide a second plurality of equalization coefficients b(n) for data transmission precoding;
a noise predictor, the noise predictor operatively coupled to combined output of the linear feedforward equalizer and the decision feedback adaptive filter to provide an input to the trellis decoder, the noise predictor, having as input a second training error signal during training mode, the second training error signal formed as a difference between the symbol decision and the received training signal subsequent to equalization, the noise predictor operatively coupled to the trellis decoder for adaptation to the first training error signal during training mode to provide a plurality of correlated noise reduction coefficients c(n) for data transmission precoding, the noise predictor further having as input a tentative error signal during data mode, the tentative error signal formed as a difference between a tentative symbol decision and a delayed received data signal subsequent to equalization, the tentative symbol decision and the delayed received data signal subsequent to equalization having one symbol time delay, the noise predictor further operatively coupled to the trellis decoder for adaptation to the trellis error signal during data mode to initially reset the plurality of correlated noise reduction coefficients c(n) to zero and to subsequently modify the plurality of correlated noise reduction coefficients c(n) for adaptive correlated noise reduction; and
a processor operatively coupled to the decision feedback adaptive filter and to the noise predictor, wherein the processor, when operative, is configured to determine a plurality of precoding coefficients t(n) as equal to a sum of the second plurality of equalization coefficients b(n) plus the plurality of correlated noise reduction coefficients c(n) plus the result of a convolution of the second plurality of equalization coefficients b(n) with the plurality of correlated noise reduction coefficients c(n)(t(n)=b(n)+c(n)+B(n)*c(n)), and wherein the processor is further configured to transfer the plurality of precoding coefficients t(n) to the transmitter for precoding of data for transmission.
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Specification