Reduced-Complexity Channel Estimation for OFDM Systems in Multipath Fast Time-Varying Channels

Abstract

Current 4G broadband wireless networks can compete the last mile broadband wireless access solution. Coherent orthogonal frequency division multiplexing (OFDM) channel estimation is the key technique used in 4G wireless networks. The Doppler frequency resulted from fast mobility environments will cause intercarrier interference (ICI) and degrade the performance of OFDM systems. Due to the severe ICI, channel estimation becomes a difficult task in higher mobility scenarios. Our aim is to propose a pilot-aided channel estimation method that is robust to fast time-varying multipath fading channels at high Doppler frequency with low computational complexity and pilot overheads. In this paper, the time duration of each estimate covers multiple consecutive OFDM symbols, named a ＂window.＂ A close-form of polynomial channel modeling has been derived. The proposed method is initialized to the least squares (LS) estimates of the channels corresponding to the time interval of the pilot symbols within the window. Then, the channel interpolation is performed in the entire window. The simulation results show that the new technique proposed here is robust to fast time-varying multipath channels, even when the normalized Doppler frequency shift is relatively high. In contrast with the state-of- the-art method, the proposed method can provide a significant reduction in computational complexity while offering comparable estimation accuracy.