Equalization of OFDM systems in time-varying channels using frequency domain redundancy

Time variations of doubly-selective channels lead to the loss of orthogonality among subcarriers, resulting in intercarrier interference (ICI) in orthogonal frequency division multiplexing (OFDM) systems. The one tap frequency equalizer is not applicable any more in this case. In this paper, we propose a frequency domain equalizer (FEQ) for OFDM systems in time varying channels using the existing redundancy in the frequency domain. We show that the equalizer matrix has a sparse structure, and thus a low computational complexity. Simulation results show that the proposed equalizer is capable of canceling ICI effectively with a low complexity.