In this paper, we propose a novel equalization method for OFDM systems without guard interval (GI). The performance of GI-free OFDM system is usually limited by inter-symbol interference (ISI) and inter-carrier interference (ICI). The proposed method is to firstly detect the tail part of transmitted OFDM symbol, then eliminate the ISI and ICI to recover the whole symbol. We find that the tail part can be obtained free of ISI and ICI, after frequency domain equalization of a proper channel, where proper means that the channel inverse is or can be approximated as FIR filter with suitable length. Since a minimum phase channel is usually proper, we also incorporate a time-domain equalizer to convert non-minimum phase channel into minimum-phase. The validity of the proposed method is confirmed by simulations.
