EUROPEAN WIRELESS CONFERENCE 1 OFDM Channel Parameters Estimation used for ICI Reduction in time-varying Multipath Channels

Abstract — In this paper, we present an improved channel matrix estimation algorithm for orthogonal- frequency-division-multiplexing downlink mobile communication systems using comb-type pilot. The channel matrix, which contains the channel frequency response and the coefficients of inter-sub-carrier-interference (ICI), is estimated using parametric multipath chan-nel model. In the algorithm, we assume the delays are time-invariant over several symbols. With delays information, the multipath complex gains time average over the effective duration of each OFDM symbol are estimated using LS or LMMSE criteria. After that, the time-variation of the multipath complex gains within one OFDM symbol are obtained by using low-pass interpolation. Hence, the channel matrix can be calculated and the ICI can be reduced. The simulation results show that the proposed method, with less number of pilots and without suppression of interference, gives a good performance over LS and LMMSE estimators with low-pass interpolation and becomes better with starting interference suppression. Index Terms — OFDM, ICI, SIS, channel estimation, time-varying channels