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US 6,647,070 B1Granted
Method and apparatus for combating impulse noise in digital communications channels
AssigneeTexas Instruments Incorporated
InventorsOfir Shalvi, Mordechai Segal, Zvi Reznic
Life of this patent
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Abstract
This invention is particularly useful as a system for digital communications over channels that suffer from impulse noise, and particularly over return cable TV channels, downstream cable TV channels, and digital subscriber loops (DSL) channels for high speed communications over twisted pair copper lines.
Claims8
A digital receiver, comprising:
- a demodulator for receiving an input data signal, down converting said signal, and sampling said signal to provide an input data stream,
- a smoother for receiving said input data stream, identifying data samples that are likely contaminated by impulse noise, and attenuating data samples likely contaminated by impulse noise,
- a filter and timing recovery portion for applying a square-root raised cosine filter to data samples output by said smoother and for determining the sample rate and sample clock phase,
- a filter for filtering the output from said filter and timing recovery portion having an impulse response sequence with a small peak to average ratio that attenuates the effect of impulse noise with a duration less than the duration of a symbol,
- an adaptive equalizer for receiving the output of said filter and compensating for carrier phase, undesired inter-symbol interference, and stationary noise components,
- a modified maximum likelihood sequence estimation (MLSE) decoder for applying a viterbi MLSE using a plurality of non-zero taps to determine a sequence of symbols in a data stream received from said adaptive equalizer, and
- a forward error correction (FEC) decoder that utilizes indications of samples contaminated with noise from said smoother to perform error correction on said data stream.
4 more elements
A method for detecting a noise impulse in a data stream, comprising:
- associating an indication with a data sample,
- comparing the absolute value of the amplitude of said data sample with a first preselected threshold value,
- setting said indicator to a first predetermined value if said amplitude is greater than said first preselected threshold value,
- comparing said amplitude to a second preselected threshold value if said amplitude is less than said first preselected threshold value,
- setting said indicator to a second predetermined value if said amplitude is greater than said second preselected threshold value, and
- setting said indicator to a third predetermined value if said amplitude is less than said second preselected threshold value.
3 more elements
A method for attenuating a noise impulse in a data stream, comprising:
- determining a residual error value for a data sample,
- comparing the absolute value of the amplitude of said residual error value with a first preselected threshold value,
- modifying the amplitude of said data sample to a first predetermined value if said amplitude is greater than said first preselected threshold value,
- comparing said amplitude to a second preselected threshold value if said amplitude is less than said first preselected threshold value, and
- modifying the amplitude of said data sample to a second predetermined value if said amplitude is greater than said second preselected threshold value.
2 more elements
Dependencies are inferred from the claim text.