Abstract: A receiver for receiving an incoming signal over a communication medium includes an echo canceller, which is adapted to receive an outgoing signal transmitted over the communication medium, and to process the outgoing signal using a set of variable processing coefficients in order to generate an echo cancellation signal. A summer combines the incoming signal with the echo cancellation signal so as to generate an echo-cancelled signal. An equalizer applies an equalization operation to the echo-cancelled signal so as to generate an equalized signal. A residual echo cancellation circuit processes the equalized signal so as to adaptively update the variable processing coefficients of the echo canceller.

Abstract: A method for transmitting data includes arranging a predetermined quantity of the data together with one or more overhead bytes in an overhead frame and dividing the overhead frame into equal segments, each of the segments including a number of bits that is not an integer multiple of eight. Each of the segments is encoded as a symbol for transmission over a communication channel.

Abstract: A method and an apparatus for multitone modulation to transmit at least two packets of data, each comprising a plurality of symbols, to provide inter-packet interleaving. The method utilizes a plurality of tones of different frequencies to transmit the data symbols of the two packets. Transmission of successive data symbols of a first data packet and of a second data packet are delayed over time, such that during at least one symbol period the tones are transmitting at least one first packet data symbol and at least one second packet data symbol. A further embodiment comprises a method for multitone modulation to transmit at least two packets of data which utilizes a plurality of modulation codes to transmit the data symbols of the two packets. The modulation codes comprise a set of orthogonal modulation codes, or the data can be modulated in accordance with CDMA modulation.

Abstract: A method of calculating echo-canceling (EC) coefficients to be used by an echo cancellation filter in a communication modem, the communication modem having a Fast Fourier Transform (FFT) serial to parallel interface, the method including the steps of transmitting a first signal including a wide-band cyclic sequence, generating an echo signal based on the first signal and a plurality of EC coefficients, receiving a second signal including a wide-band cyclic sequence, subtracting the echo-canceled signal from the second signal to produce an echo-cancelled signal, transforming the echo-cancelled signal via the FFT serial to parallel interface to produce a transformed echo-cancelled signal, and calculating the plurality of EC coefficients based on the transformed echo-cancelled signal.

Abstract: A system for detecting and correcting impulse noise present on an input data signal includes an impulse detector module receiving an input data signal and producing as output an correction enable signal indicating when an impulse correction is required. An impulse corrector module receives the input data signal and a correction enable signal and produces a corrected data signal, e.g., having the impulse canceled or blanked, as output. A reliability estimator and selector module receives the corrected data signal and the input data signal and selects as output the input signal which is more reliable. In one embodiment, the impulse detector includes first and second complementary impulse detectors, the outputs of which are analyzed by an enable and correction module to produce an impulse detection signal with improved accuracy. Preferably, the enable and correction module also indicates the most appropriate type of impulse correction in accordance with the detection signals from the complementary detectors.

Abstract: A receiver for receiving an incoming signal over a communication medium includes an echo canceller, which is adapted to receive an outgoing signal transmitted over the communication medium, and to process the outgoing signal using a set of variable processing coefficients in order to generate an echo cancellation signal. A summer combines the incoming signal with the echo cancellation signal so as to generate an echo-cancelled signal. An equalizer applies an equalization operation to the echo-cancelled signal so as to generate an equalized signal. A residual echo cancellation circuit processes the equalized signal so as to adaptively update the variable processing coefficients of the echo canceller.

Abstract: Impulsive noise is detected for each discrete multi-tone (DMT) symbol. If impulsive noise is detected, all bytes, which belong to the associated DMT symbol are tagged by “erasure bits”. After interleaving, Reed-Solomon decoding is initially performed without erasures. If the decoding fails, it is performed again, this time with erasures. Reed-Solomon decoders report failure with relatively high certainty, and thus, if the first stage (decoding without erasures) includes failure or errors due to impulsive noise, the second stage of decoding is performed again with erasures.

Abstract: An encoding/framing scheme for multitone modulation over impulsive channels which allows efficient operation in multipoint to point channels which are affected by ingress (narrowband noise) and impulsive (burst) interference. The coding is achieved using a concatenated approach, with the inner code being Trellis Coded Modulation (TCM), using, for example, convolutional coding, and the outer code being a Reed Solomon (RS) code. Two dimensional interleaving is performed, with one dimension being time, and the other dimension being frequency (tones or sub-channels). The TCM coding provided by the present invention is quite effective in dealing with impulse noise effects. The interleaving may be applied in two levels. According to one embodiment, user data is RS encoded, and a portion of the RS encoded data is interleaved and filled along columns for transmission using a multitone transmission system.

Abstract: Presented is a method and system for interleaving or de-interleaving a datastream of codewords divided into indexed symbols including the step of allocating an electronic memory into a predetermined number of FIFOs equal to the desired depth (D) of the interleave operation.

Abstract: An encoding/framing scheme for multitone modulation over impulsive channels which allows efficient operation in multipoint to point channels which are affected by ingress (narrowband noise) and impulsive (burst) interference. The coding is achieved using a concatenated approach, with the inner code being Trellis Coded Modulation (TCM), using, for example, convolutional coding, and the outer code being a Reed Solomon (RS) code. Two dimensional interleaving is performed, with one dimension being time, and the other dimension being frequency (tones or sub-channels). The TCM coding provided by the present invention is quite effective in dealing with impulse noise effects. The interleaving may be applied in two levels. According to one embodiment, user data is RS encoded, and a portion of the RS encoded data is interleaved and filled along columns for transmission using a multitone transmission system.

Abstract: A method and apparatus for extending the dynamic range of an integer or fixed-point Fast Fourier Transform (“FFT”) system that may be used in communications devices such as ADSL modems. The disclosed FFT system utilizes a shift control module to increase the effective dynamic range of the FFT implementation by selectively choosing at least one stage of an FFT butterfly implementation in which the outputs of the butterfly stage are not divided to otherwise avoid overflow problems.

Abstract: A method for use in data communications equipment for improving convergence of a hybrid decision feedback apparatus including an adaptive feed-forward equalizer and an adaptive decision feedback equalizer. An independent error predictor component is used for better convergence and then is eliminated by converting, using z-transformations, the adaptive feed forward equalizer and adaptive decision feedback equalizer to an equivalent feed forward equalizer and an equivalent decision feedback equalizer, respectively, in which the error predictor is embedded or incorporated therein. The smaller system with a reduced number of FFE-DFE coefficients has a faster convergence rate.

Abstract: A system for detecting and correcting impulse noise present on an input data signal includes an impulse detector module receiving an input data signal and producing as output an correction enable signal indicating when an impulse correction is required. An impulse corrector module receives the input data signal and a correction enable signal and produces a corrected data signal, e.g., having the impulse canceled or blanked, as output. A reliability estimator and selector module receives the corrected data signal and the input data signal and selects as output the input signal which is more reliable. In one embodiment, the impulse detector includes first and second complementary impulse detectors, the outputs of which are analyzed by an enable and correction module to produce an impulse detection signal with improved accuracy. Preferably, the enable and correction module also indicates the most appropriate type of impulse correction in accordance with the detection signals from the complementary detectors.

Abstract: A system and method is presented for reducing the power consumed by a line driver driving a signal to be transmitted through a communications media. The preferred method includes the steps of: (1) delaying the signal; (2) determining whether the signal has reached a predetermined threshold value; (3) increasing power supplied to the line driver in response to an indication from the determining step that the threshold has been reached; and (4) delivering the delayed signal to the line driver. The preferred system includes: (1) a digital signal processor; (2) a line driver; (3) a digital delay line disposed between the digital signal processor and the line driver; and (4) a power regulator disposed between the threshold detector and the line driver. The system and method, while applicable to many communications formats, is particularly applicable to communications methods transmitting signals having a relatively large dynamic range, such as xDSL communications techniques.