An iterative channel estimator for fast-varying channels using successive OFDM symbols

This paper deals with pilot-based channel estimation for fast varying channels in Orthogonal Frequency Division Multiplexing (OFDM) systems. Due to the variation of the channel during one OFDM symbol, one-tap channel estimation and the corresponding equalization is no longer the optimum solution and such a variation results in inter-carrier interference (ICI). One of the possible approaches to predict this interfering effect is to use basis expansion model (BEM) with which the variation of the channel can be approximated successfully. However, as the pure BEM does not solve completely the problem, we investigate the estimation problem using decision feedback to enhance the performance. In particular, we propose a simple algorithm based on using two successive OFDM symbols to filter channel coefficients and improve not only the convergence of pure decision feedback based estimation but also the system performance. Simulation results based on Jake´s channel model with a high Doppler spread and a practical high data rate system sustain our claims.