Time domain equalizer for ADSL

A method for equalizing data transferred over a digital subscriber loop (DSL) modem data telecommunication channel having a frequency response utilizing a discrete multi-tone (DMT) signaling protocol wherein each frame is comprised of the inverse fast Fourier transform (IFFT) of a number of data samples;

• the response from the channel being given by h, the equalizer being given by w, and effective channel overall response being given by b=h*w;
• the method comprising the steps of:
• providing a sequence of training data y;
• receiving said training data sequence y through the channel;
• performing a fast Fourier transform (FFT) on the received training data y to obtain fast Fourier transformed data Y of said training data y;
• providing a training sequence X;
• dividing fast Fourier transformed data Y by said training sequence X to obtain an estimate H of the frequency response of the channel;
• then performing an IFFT on said estimate H of the frequency response of the channel a multiple number of times to obtain plural IFFT of plural said estimates h of the channel response;
• averaging said plural estimates to provide an improved estimate of the channel response h;
• defining an initial estimate of an equalizer w;
• filtering the averaged h using w;
• updating w using a least mean squared (lms) algorithm, with an error equal to the output of the filter and input equal to h;
• continuing filtering and updating w for the whole length of said averaged h;
• and
• repeating the foregoing steps commencing with the step of defining w using each new value of w until the lms converges.