Doppler frequency spread estimation for OFDM systems in time-varying fading channel

In this paper, a new Doppler frequency spread estimation method based on the autocorrelation function of the estimated channel impulse response is proposed for OFDM systems in the time-varying channel. We propose a technique to separate the Doppler frequency spread in both slow and fast modes that correspond to vehicle speed. The feature of proposed method is to achieve the accurate Doppler frequency spread estimation in the low mode based on comparing and approximating the ideal autocorrelation function value with the estimated autocorrelation function at the same time index. In the fast mode, we apply the conventional Doppler frequency spread estimation based on the zero-crossing of the autocorrelation function. This paper presents various computer simulation results to verify the effectiveness of proposed Doppler frequency spread estimation method in the both of slow and fast mode condition.