Non-Biased Linear Approximation Method of CIR for ICI Mitigation in High Mobility OFDM System

In orthogonal frequency division multiplexing (OFDM) system, the property of the channel impulse response (CIR) is generally assumed to be time-invariant in one OFDM symbol. However, the assumption is proved wrong in mobile environments, thus leading to inter-carrier interference (ICI) by Doppler spread. A typical solution for this problem is a piece-wise linear approximation to estimate channel time-variations in pilot-aided OFDM mobile systems. Unfortunately, the solution causes biased linear approximation error, which yields the poor performance in the receiver. In this paper, we propose novel non-biased linear approximation of CIR in OFDM mobile systems to mitigate ICI. Theoretical analysis and simulation show that the proposal satisfies the required correlation characteristics without a series of assumptions and outperforms the previous methods in terms of channel estimation.