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Leland Stanford Junior University

Atul Salvekar

John Matthew Cioffi

Carlos Aldana

Peter P Chow

Chaohuang Zeng

James Thomas Carlo

Louise Min Chuin Hoo

Methods, apparatus and systems for identifying crosstalk interference in xDSL systems are disclosed and are useful in a variety of xDSL systems to assist in the provisioning, maintenance and diagnosis of the xDSL system and in spectral management and assignments. Signal data are collected from a receiver, a primary transmitter and any crosstalk transmitters. The signal data are resampled, if necessary. A first estimate of the timing offset between the received signal and each crosstalk signal is then obtained by cross-correlating the received data with the transmitted crosstalk data. The first timing offset estimate is then used in connection with a least-squares estimation of the crosstalk response for the considered crosstalk data and a second estimate of the timing offset. The invention may be used at a third party site remote from the system transmitters and receivers. The crosstalk identification of the present invention can be used in dynamic spectrum management for DSL services and signals.

Crosstalk identification in xDSL systems

Methods and devices for adaptively changing a parameter (such as sub-carrier bit allocation and/or gain) in a multi-carrier communication signal are described. In a method aspect, a unit that determines a need for a change sends an express change request to a second unit. The change request identifies one or more specific sub-carrier carrier to be altered and a desired value for the parameter to be changed for each identified sub-carrier. The requesting unit then monitors the communication signal it receives to determine whether the requested change has been implemented. The determination of whether the requested change has been implemented is based at least in part upon an analysis of a portion of the received communication signal that was intended to be changed. In another aspect of the invention, the change request command includes a header, a control field, at least one sub-carrier identifier, at least one desired parameter value indicator, and an error field. The header identifies the command as a change request command. The control field includes a tone count that indicates the number of tones to be altered. Each sub-carrier identifier identifies a specific sub-carrier to be altered and each desired parameter value indicator identifies a desired parameter value for its associated sub-carrier. The error field permits the unit receiving the change request to detect whether there is an error in its interpretation of the change request command.

Express bit swapping in a multicarrier transmission system

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Stanford, CA, United States of America

Atul Salvekar