Channel Estimation and ICI Cancellation for OFDM Systems in Doubly-Selective Channels

In orthogonal frequency division multiplexing (OFDM) systems, time- and frequency-selective (or doubly-selective) fading leads to the loss of subcarrier orthogonality and the occurrence of inter-carrier interference (ICI), which increases an irreducible error floor in proportional to the normalized Doppler frequency offset. Channel estimation (CE) in rapidly time-varying multi-path scenarios is critical for ICI cancellation and coherent demodulation. In this paper, we introduce an iterative CE scheme to estimate time-varying channel parameters and a low-complexity equalization method to cancel ICI and detect data. The proposed CE technique performs an initial CE based on a piece-wise linear model. Then ICI is reconstructed and cancelled from the received signals. Estimating channel again by using signals of less interference, refined CE can be obtained. Meanwhile, a low-complexity equalizer is proposed to further improve BER performance. Finally, simulation results show good performance of the proposed CE method in doubly-selective fading channels.