A frequency-domain eigenfilter approach for equalization in discrete multitone systems

The discrete multitone (DMT) modulation has been chosen as the industry standard for asymmetrical digital subscriber loop (ADSL) modems and is also a candidate scheme for very-high-speed digital subscriber line (VDSL) systems. The DMT system works on the condition that the length of the channel response is not longer than that of the guard band known as cyclic prefix to avoid intersymbol interference (ISI). A time-domain equalizer (TEQ) is utilized in the DMT system to shorten the effective channel impulse response such that the data rate loss due to the use of cyclic prefix is reduced. In this paper, we propose a new frequency-domain eigenfilter approach to train the TEQ. Simulation results indicate that this algorithm can effectively shorten the channel response. Furthermore, we show that this frequency-domain eigenfilter method provides different TEQ solutions by computing the eigenvectors corresponding to several smallest eigenvalues of a performance matrix.