Effects of Time Synchronization on OFDM Systems Over Time-Varying Channels

In this paper we refine a previously proposed model of time-varying OFDM systems, by taking into account the effects of non-ideal time synchronization. The considered non-ideal time synchronization includes the positioning of the receiver discrete Fourier transform (DFT) window and a cyclic shift of the input data. In OFDM systems with time-invariant channel, these two operations are equivalent. However, in the presence of a time-varying channel, OFDM suffers from intercarrier interference (ICI) which is differently affected by the positioning and the cyclic shift. We investigate the different effects and propose a refinement of the ICI modelling so that it holds also in the presence of non-ideal time synchronization. We verify the proposed refinement by testing a previously proposed ICI cancellation algorithm in the presence of non-ideal time synchronization