Time-Varying Channel Complex Gains Estimation and ICI Suppression in OFDM Systems

In this paper, we present an iterative algorithm for channel complex gains estimation with inter-sub-carrier- interference (ICI) reduction in orthogonal-frequency-division- multiplexing downlink mobile communication systems using comb-type pilot. Assuming delays information, the time-variation of the multipath complex gains within one OFDM symbol are obtained by interpolating the symbol time-average values, which have been previously estimated with LS criteria. After that, the channel matrix is computed and the ICI is reduced by using successive interference suppression (SIS) in data symbol detection. The algorithm's performance is further enhanced by an iterative procedure, performing channel estimation and ICI suppression at each iteration. Mean Square Error theoretical analysis and simulation results show a significant performance improvement for high normalised Doppler spread (especially after the first iteration) in comparison to conventional methods.