Zero-forcing frequency domain equalization for DMT systems with insufficient guard interval

A generalized discrete multitone (GDMT) scheme, that not only uses the guard interval, but also redundancy in the frequency domain for equalization, has been introduced recently (Trautmann, S. and Fliege, N.J., IEEE Commun. Letters, vol.6, no.1, p.34-6, 2002; IEEE J. on Selected Areas of Commun., vol.20, no.5, p.987-96, 2002; Karp, T. et al., Proc. IEEE Int. Conf. on Commun., p.1646-50, 2002). Instead of assigning all redundancy in the time domain, it allows taking advantage of unused subcarriers to remove ISI and ICI. We calculate the signal-to-noise ratio for each subcarrier for the zero-forcing equalizer proposed in Karp et al. From there, we derive a new adaptive loading algorithm that optimally chooses the length of the guard interval and the position of unused subcarriers. The cost function applied for the adaptive loading algorithm is the achievable data rate at a fixed error probability.