An Pilot-Assisted Channel Estimation Method for OFDM Systems in Time-Varying Channels

Orthogonal frequency division multiplexing (OFDM) systems encounter performance degradations due to the time varying (TV) channels in wireless environments. As delay spread increases, symbol duration should also increase, and then OFDM systems become more susceptible to time-variations. Time-variations introduce inter-carrier interference (ICI), which must be mitigated to improve the performance in high delay and Doppler spread environments. In this paper, we propose a method to estimate the TV channel. The method is designed for the comb pilot pattern. It performs a multi- symbol processing of the LS estimate over the pilot sub- carriers to detect the active paths of the channel and uses a piece-wise linear model to approximate the time-variations characteristic of each active path during each OFDM symbol to mitigate ICI. Theoretical analysis and simulation result show performance improvement in high delay and Doppler spread environments.