Time-domain Equalizer Design for Discrete Mijltitone Systems

In Discrete Multitone (DMT) transceivers, a cyclic prefix of length y is inserted between transmitted symbols. If the channel impulse response is of length y + 1 or shorter, the intersymbol interference can be avoided. To reduce the inefficiency due to the use of a long cyclic prefix, the use of a time domain equalizer (TEQ) to shorten the effective channel impulse response has been the most popular equalization approach in DMT receivers. In this paper, we pose the TEQ design problem completely in the frequency domain by minimizing the least squares cost function defined in the frequency domain. We also show the connection between the frequency-domain least squares cost function and its time-domain counterpart for the TEQ design. Furthermore, we extend this frequency-domain least squares approach by incorporating noise suppression into the cost function and derive a new learning algorithm such that the channel impulse response can be shortened and noise and interference can be suppressed.