Mixed time and frequency domains equalization algorithm for ADSL systems

An asymmetric digital subscriber line system including a transmitted signal having a plurality of training symbols, comprising:

• a channel for receiving the transmitted signal;
• a target channel for receiving the transmitted signal;
• a first mixer coupled to the channel for receiving an output of the channel;
• a time-domain equalizer coupled to the first mixer to receive an output of the first mixer, the time-domain equalizer including a plurality of coefficients;
• a first modulator coupled to the time-domain equalizer to provide a first modulated signal;
• a channel estimator, coupled to the first modulator to receive the first modulated signal, providing an estimated channel to the target channel;
• and
• a second mixer, coupled to receive the output of the time-domain equalizer and an output of the target channel, providing an output to the time-domain equalizer.

A discrete multi-tone transceiver, comprising:

• a channel estimator for receiving a first modulated signal and a second modulated signal, including
• a first calculating means for estimating an effective channel in the frequency domain based on the first and second modulated signals,
• an inverse Fast Fourier Transform means coupled to the first calculating means for converting the effective channel to the time domain, and
• a rectangular windowing means coupled to the inverse Fast Fourier Transform means for providing a rectangular windowing function on the effective channel in the time domain to limit the estimated channel to v+1 samples.

A method for training a time-domain equalizer having at least one coefficient, comprising:

• receiving a first modulated signal in the frequency domain;
• receiving a second modulated signal in the frequency domain;
• estimating an effective channel in the frequency domain based on the first and second modulated signals;
• converting the effective channel to the time domain;
• and
• rectangular windowing of the effective channel in the time domain to limit the estimated channel to v+1 samples.