Frequency domain equalization of DMT/OFDM systems with insufficient guard interval

We propose a new, generalized approach for equalization of discrete multi-tone (DMT) systems, which not only uses redundancy in the time domain by adding a guard interval, but also takes advantage of existing or intentionally placed redundancy in the frequency domain. For this purpose, we replace the one tap frequency equalizer in the DMT receiver by a block equalizer and derive sufficient conditions for zero forcing equalization, i.e. perfect removal of intersymbol and intercarrier interference. We show that the equalizer matrix is sparse, thus resulting in a low computational complexity. Furthermore, the equalization approach allows one to trade off the guard interval in the time domain for unused subcarriers in the frequency domain.