Conexant Systems, Inc.

Mindspeed Technologies, Inc.

Rockwell Science Center, Inc.

Thomas C Liau

Jason Brent

Wei Kang Tsai

Keith T Chu

Zhenyu Zhou

Wei K Tsai

A communication system is provided for transferring data through a digital switching network. The communication system includes a client modem, a linecard in communication with the client modem over a local loop, and a linecard modem interfacing with the linecard and the digital switching network. The client modem modulates client data to generate modulated client data for transmission to the linecard over the local loop, and the linecard modem receives the modulated client data from the linecard and demodulates the modulated client data to generate the client data for transmission through the digital switching network. Further, the linecard modem modulates network data from the digital switching network to generate modulated network data for transmission to the client modem over the local loop, and the client modem receives and demodulates the modulated network data to generate the network data.

Communication model for linecard modems

An apparatus and method for minimizing nonlinear distortions in computer system communications where the upstream signal from a client modem to a server modem is periodically sampled, the samples being utilized by a non-linear decision feedback equalizer to periodically produce sets of equalizer coefficients. The equalizer coefficients are sent via an independent communication channel downstream to the client modem to continuously update distortion-minimizing adjustments to the client modem's upstream output. The samples are taken periodically in order to update the non-linear decision feedback equalizer so that it can provide appropriate equalizer coefficients for the changing characteristics of the upstream signal. The method includes identifying, by a first communication system, nonlinear equalization parameters to be used by a second communication system to minimize nonlinear distortions on a primary communication channel. The method also includes transmitting, by the first communication system, the nonlinear equalization parameters to the second communication system by a secondary communication channel. In addition, the method includes receiving, by the second communication system, the nonlinear equalization parameters from the first communication system. Finally, the method includes utilizing, by the second communication system, the nonlinear equalization parameters to minimize nonlinear distortion on the primary communication channel.

Non-linear equalization for the upstream data connection of 56K PCM modems

An initialization procedure for a digital modem system treats the presence of ADPCM as if it were a digital impairment such that the modem system can utilize effective compensation techniques to address the ADPCM. The modem system initially determines whether the current communication channel is a fully digital channel. Next, the modem system determines whether the channel includes any ADPCM elements. If ADPCM is detected, then a digital impairment learning routine is performed to obtain the ADPCM compression characteristics and data rate. The digital impairment learning routine may use a single probing sequence to obtain the ADPCM characteristics while identifying any concurrent digital impairments such as RBS, digital pads, and encoding law conversions. Once the digital channel is characterized, the modem system may condition its transmitters and receivers in an appropriate manner to obtain an increased data rate.

Method and apparatus for detecting and determining characteristics of a digital channel in a data communication system

An echo canceler for calculating an echo impulse response during a training sequence, wherein a sequence of data samples is selected such that a full rank data correlation matrix comprised of such data samples is diagonal at the Nth iteration. The echo canceler estimates the echo impulse response based on such data samples and an echo generated during the training sequence using a normalized least means square algorithm, wherein the length of the data sequence to sound the echo channel is N. This normalized LMS algorithm, wherein the data sequence is specifically selected, converges toward an echo impulse response much faster than standard LMS algorithms, while having a computational complexity comparable to that of the standard LMS algorithm.

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Irvine, CA, United States of America

Thomas C Liau