A maximum likelihood OFDM receiver with smoothed FFT-window for large multipath delay difference over the guard interval

This paper proposes a new maximum likelihood OFDM receiver for multipath fading environment with large delay spread. The large delay difference over the guard interval (GI) duration of the OFDM signal generally results in intersymbol interference (ISI) between temporally adjacent symbols and interchannel interference (ICI). Both of them spread over a large number of subcarriers. The new OFDM receiver consists of equalizers for both ISI and ICI and an accurate channel impulse response estimator. Furthermore, it introduces a temporal-window technique for the FFT-window in order to suppress the ICI, which is very effective for reducing the complexity of ICI equalization by maximum likelihood sequence estimator (MLSE). Computer simulation is conducted in order to verify the performance of the proposed OFDM receiver, and its effectiveness is shown.