Low-Complexity Equalisation Methods for OFDM Systems in Doubly Selective Channels

Time-selective channels in orthogonal frequency division multiplexing (OFDM) systems introduce intercarrier interference (ICI) which destroys the orthogonality among the subcarriers. Equalisation techniques are needed to mitigate ICI, requiring high computational complexity for large values of Doppler spread. In this paper, we propose low-complexity equalisation methods that result in 75% savings in computations over some of the conventional methods. The savings are achieved without any loss in performance. One of the methods is to apply the one-tap equaliser on selected subcarriers to detect the corresponding symbols. We develop a criterion to determine the eligible subcarriers.