Patent ID: 6028891
Filing Date: 2000-02-22
Classification: H04L

Abstract:
An asymmetric digital subscriber loop system, comprising:(a) a central office, comprising:a transmitter section for transmitting information to a remote terminal in a down-stream signal, such down-stream signal having a plurality of subchannels extending over an upper portion of a predetermined band of frequencies; and,a receiver section for receiving information from the remote terminal in an up-stream signal, such up-stream signal having a plurality of subchannels extending over a lower portion of the predetermined band of frequencies, such up-stream signal and down-stream signal passing through a communication medium;(b) the remote terminal, comprising:a transmitter section for transmitting information to the central office in the up-stream signal; and,a receiver section for receiving information from the transmitter section in the down-stream signal; and(c) wherein the transmitter section of the remote terminal includes:a modulator for distributing a sequence of digital data among the lower portion of the plurality of subchannels, such modulator producing a sequence of digital data at a data rate greater than, or equal to, twice the highest frequency in the lower portion of the predetermined band of frequencies, such modulator producing undesired images of the lower portion of the plurality of subchannels falling into the upper portion of the plurality of subchannels, such undesired images being noise in the upper portion of the plurality of subchannels;an interpolator for inserting interpolated digital data into the sequence of digital data produced by the modulator to produce a sequence of digital data at a rate greater than the rate of the digital data produced by the modulator, such interpolator reducing said undesired images of the lower portion of the plurality of subchannels falling in the upper portion of the plurality of subchannels produced by the modulator, such interpolator reducing said noise within the upper portion of the plurality of subchannels;a digital to analog converter for converting the sequence of digital data produced by the interpolator having the reduced noise within the upper portion of the plurality of subchannels into the up-stream signal.