Conexant Systems, Inc.

Rockwell International Corporation

Paradyne Corporation

Anthony A Tzouris

Kenneth David Ko

Jamal Haque

Edward S Zuranski

Shrenik P Patravali

Keith A Souders

Manuel I Rodriguez

P Michael Henderson

John S Walley

Steven A Gronemeyer

Joel D Peshkin

Raphael Rahamim

Ganning Yang

Yongbing Wan

Kenneth Scott Walley

Frederic M Stubbe

David O Anderton

Ismail I Eldumiati

Don L Harmer

Edward Arthur Thoenes

A digital subscriber line (DSL) communication system that utilizes the high frequency band of a standard telephone line does not require the use of a plain old telephone service (POTS) splitter in the resident's home, which provided isolation between the POTS frequency band (0 to 4 kHz) and the DSL frequency band. A digital subscriber line modem utilizes either constant envelope modulation or quadrature amplitude modulation for outputting DSL signals upstream to a central office. When a telephone in the resident's home is detected as being off-hook, then the constant envelope modulation is used by the DSL modem in order to lessen the intermodulation product distortion that results in audible noise heard by a user of the telephone. When the telephone is on-hook, then another type of modulation, such as QAM, is used to maximize the upstream data rate capability in the DSL frequency band, since any noise generated by the QAM is not a problem due to the non-use of the POTS frequency band.

Modulation switching for DSL signal transmission

A digital subscriber line communication system does not require the use of a plain old telephone service (POTS) splitter in the resident's home. Digital signal processing techniques are utilized to adapt to varying subscriber line conditions due to POTS telephone equipment. The digital signal processing techniques eliminate the need for a splitter by reducing susceptibility to distortion due to varying subscriber line characteristics. The digital subscriber line modem characterizes the subscriber line under a variety of conditions when the modem is in a non-idle mode. The digital subscriber line modem includes a control circuit which performs rapid retrain operation utilizing line characterization information.

Method of and apparatus for performing line characterization in a non-idle mode in a subscriber line communication system

A digital subscriber line communication system does not require the use of a plain old telephone service (POTS) splitter in the resident's home. Digital signal processing techniques are utilized to adapt to varying subscriber line conditions due to POTS telephone equipment. The digital signal processing techniques eliminate the need for a splitter by reducing susceptibility to distortion due to varying subscriber line characteristics. The digital subscriber line modem characterizes the subscriber line under a variety of conditions. The digital subscriber line modem includes a control circuit which performs rapid retrain operation utilizing line characterization information.

Method of and apparatus for performing line characterization in a subscriber line communication system

Disclosed is a circuit and method that eliminates the problem of voice echo created by the use of simultaneous voice and data (SVD) modems in a remote office application. In the instant invention, a voice signal originates in a remote office telephone and is modulated with a data signal and sent from a first SVD modem to a second SVD modem, where it is demodulated and then routed from the second SVD modem back into the switching network to a second telephone where a voice echo signal may be created by existing hybrid transformers. This echo signal will follow the return path of the voice signal to the second SVD modem where it is modulated with a data signal, sent back to the first SVD modem, demodulated, and then routed back to the remote telephone. The echo and voice signal is thus delayed by the modulation and demodulation of the voice and data signals in both SVD modems by a time period of greater than thirty-five milliseconds. The result is an intolerable and disruptive echo signal that is perceived by the person speaking in the remote which is eliminated by the introduction of voice echo cancellation in the circuit.

Voice echo cancellation for SVD modems

A digital subscriber line communication system does not require the use of a plain old telephone service (POTS) splitter in the resident's home. Digital signal-processing techniques are utilized to accommodate varying subscriber line conditions coming from POTS telephone equipment. The digital signal-processing techniques eliminate the need for a splitter by reducing susceptibility to distortion resulting from varying subscriber line characteristics. The digital subscriber line modem can utilize quadrature amplitude modulated (QAM) signals and frequency division multiplexing. The digital subscriber line modem includes a control circuit that implements an echo canceler and an analyzer to reduce near-end cross-talk noise. The analyzer performs spectral analysis to preemphasize or to predistort the transmitted signals in accordance with the cross-talk noise.

Digital subscriber line modem utilizing echo cancellation to reduce near-end cross-talk noise

A digital subscriber line (DSL) communication system that utilizes the high frequency band of a standard telephone line does not require the use of a plain old telephone service (POTS) splitter in the resident's home, which provided isolation between the POTS frequency band (0 to 4 kHz) and the DSL frequency band. Digital signal processing techniques are utilized to adapt to varying subscriber line conditions due to POTS telephone equipment. The digital signal processing techniques eliminate the need for a splitter by reducing susceptibility to distortion due to varying subscriber line characteristics. The digital subscriber line modem utilizes constant envelope modulated signals and frequency division multiplexing, where the constant envelope modulations lessens the intermodulation distortion products due to DSL signals that are transmitted by the modem and which may result in audible noise at the POTS telephone equipment due to non-linearities of the POTS telephone equipment.

Constant envelope modulation for splitterless DSL transmission

A digital subscriber line communication system does not require the use of a plain old telephone service (POTS) splitter in the resident's home. Digital signal processing is utilized to adapt to varying subscriber line conditions coming from POTS telephone equipment. The digital subscriber line modem includes a control circuit that utilizes a Reed-Solomon decoder and a synchronization error generator. The Reed-Solomon decoder provides a frame error signal, and the synchronization error generator responds to the frame error signal to generate a synchronization error signal. The synchronization error generator is configured as a leaking integrator to provide the synchronization error signal in response to a relatively large number of frame error signals occurring in a period of time. A resynchronization operation is performed in the modem in response to the synchronization error signal.

Communication system utilizing Reed-Solomon code to achieve auto frame

A digital subscriber line communication system does not require the use of a plain old telephone service (POTS) splitter in the resident's home. Digital signal processing techniques are utilized to adapt to varying subscriber line conditions due to POTS telephone equipment. The digital signal processing techniques eliminate the need for a splitter by reducing susceptibility to distortion due to varying subscriber line characteristics. The digital subscriber line modem utilizes quadrature amplitude modulated (QAM) signals and frequency division multiplexing. The digital subscriber line modem includes a control circuit which includes a rapid retrain circuit. The rapid retrain circuit can retrain the digital subscriber line modem in less than 0.5 seconds.

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Clearwater, FL, United States of America

Anthony A Tzouris