3com Corporation

Tim Murphy

Martin Staszak

Richard G Williams

Vlad Mitlin

Richard G C Williams

Lloyd Sarsoza

A method, and apparatus implementing the method, encodes bits to be transmitted over a channel. The channel may be a single carrier or a multi-carrier channel. Bits are encoded based on a constellation that has a self-similarity property and also has an improved bit error rate. The constellation was iteratively generated using a mirroring technique. In addition, a method, and apparatus, implementing the method, decodes bits that were received from a channel. The bits are decoded for a constellation that has a self-similarity property and that was generated using the mirroring technique.

Method and apparatus for improving error control properties for encoding and decoding data

A digital subscriber line network allows a plurality of remote modems to communicate without interfering with the communication to the central office. Each symbol of a superframe is converted to a tone vector, and the tone vectors are integrated over a plurality of superframes. The tone vectors of the data symbols are random, and tend to cancel each other out. The tone vector of the synchronization symbol remains constant among the plurality of superframes, and the sum of these tone vectors over a plurality of superframes becomes large. By identifying the largest integrated tone vectors, the network may identify the position of the synchronization symbol. The modems may then align using the position of the synchronization symbol.

Superframe alignment to a pre-existing ADSL data exchange

A method for reducing noise from a non-linear device, such as a telephone, that shares a customer loop with a splitterless Asymmetric Digital Subscriber Line modem. The non-linearity of the device can cause some of the upstream signal to bleed into the downstream signal band. The modem examines the downstream band when it is transmitting fast retrain signals. By comparing the power in the band to a previous value when the modem transmitted upstream at a higher power level, the modem may determine whether to cut back its transmitted power to lessen the noise in the downstream band. In this manner, the method may allow optimal downstream data transfer regardless of what non-linear device shares the customer loop with the ADSL modem.

Method for reducing noise from a non-linear device that shares a customer loop with an asymmetric digital subscriber line modem

A method for optimizing downstream data transfer in a telephone from a splitterless asymmetric digital subscriber line modem. The modem examines the power spectrum of fast retrain signals both when the telephone is on-hook and off-hook. By comparing the power in the spectra, the modem may determine whether to cut back its transmitted power to lessen the noise in the downstream channel. In this manner, a customer may simultaneously use the telephone and the modem on the same telephone loop.

Method for optimizing downstream data transfer in an asymmetric digital subscriber line modem

The present invention includes alternative methods for selecting forward error correction parameters to be used in multi channel communications. Method embodying aspects of the present invention may include acquiring signal to noise ratio data for a set of communications channels, counting, estimating or identifying channels to carry data, computing an average signal to noise ratio for channels used and selecting set(s) of FEC parameters. It may predicting net SNR gains and storing these predictions as splines or in interpolation tables. This invention is specifically applicable to Reed-Solomon encoding for FEC and selecting the Reed-Solomon parameters S and R/S. Symbol sets, represented by S may consist of dmt symbols or of data carried by multiple channels in one transmission interval. The computations for selecting parameters may include adjusting the average signal to noise ratio by a safety margin. The selected sets of parameters may be chosen from sets identified by a sending terminal and may be forwarded from a receiving terminal to a sending terminal.

Method of selecting initialization parameters for multi-channel data communication with forward error correction

A method for reducing audible noise in a telephone from a splitterless asymmetric digital subscriber line modem. The modem examines the shape of the power spectrum of fast retrain signals both when the telephone is on-hook and off-hook. By comparing the spectra, in particular the slopes of the spectra, the modem may determine the quality of the telephone that shares the telephone loop with the modem. The modem cuts back its transmitted power depending on the quality of the telephone by an amount that suppresses the audible noise in the telephone. In this manner, a customer may simultaneously use the telephone and the modem on the same telephone loop.

Method for reducing noise from an asymmetric digital subscriber line modem

A method for recovering from an excessive power cutback in a splitterless asymmetric digital subscriber line modem. The modem may apply a power cutback to enable simultaneous use of the modem and a telephone. The modem determines if the modem's power after the cutback is sufficient to support data communication with the central office. If the power is insufficient, the modem gradually reduces the power cutback, checks the sufficiency of the power again, and repeats this cycle. The modem repeats the cycle until the modem attains an acceptable transmit power where the power requirements for data transfer and noise reduction are balanced.

Method for asymmetric digital subscriber line modem recovery from insufficient transmit power

A method for rapid noise reduction from a splitterless ADSL modem. The modem stores a value for the power level of its transmitter in a table along with transmission characteristics of the telephone loop. The stored value for its power level is the power level that was previously successful with the transmission characteristics in achieving the Showtime data transfer mode. When the modem measures similar transmission characteristics of the telephone loop, such as a slope of the frequency response of the loop, a power level that would suppress downstream noise, or the dc voltage of the loop, the modem searches the table for matching transmission characteristics. If the table contains a table entry that matches these measured transmission to characteristics, the modem restores the stored transmitter power of the modem. In this manner, the modem may rapidly achieve Showtime because it is restoring a transmitter power level that was previously successful under the same condition of the telephone loop.

Method for rapid noise reduction from an asymmetric digital subscriber line modem

A system and method for converting data between a multi-bit time division multiplexed (TDM) bus and a faster single-bit TDM bus, wherein each TDM bus communicates data by means of frames, each frame comprising a fixed number of slots and each slot comprising a fixed number of bits, the system comprising digital circuitry for establishing a clock rate R.sub.SB for the faster single-bit TDM bus that has the following relationship to a clock rate R.sub.MB for the multi-bit TDM bus: R.sub.SB =R.sub.MB *((slots per frame)*(bits per slot)+1).div.(slots per frame).

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Ramona, CA, United States of America

Tim Murphy