Proposal of Doppler estimation method of using frequency channel response for OFDM systems

This paper proposes a new Doppler frequency spread estimation method based on the time autocorrelation function of channel frequency response (CFR) for OFDM systems. The feature of proposed method is to employ the least squares (LS) method between the zero order Bessel function approximated by the expansion of power series and the estimated time autocorrelation function of using CFR which is indispensable to the frequency domain equalization in the OFDM receiver. In the previously proposed method by the authors, the wider range of approximation for the Bessel function is required to achieve the accurate Doppler frequency estimation especially in the lower carrier-to-noise power ratio (CNR) which leads higher computation complexity for solving the LS equation. To solve this problem, this paper proposes a new Doppler estimation method of using an adaptive region selection method for the approximation of Bessel function based on the received CNR. This paper also proposes the estimation method of CNR to be used in the proposed Doppler estimation method. The proposed method can achieve the accurate estimation of noise power at the receiver even when the received signal includes larger inter-carrier interference (ICI) noise due to the higher Doppler frequency spread. The proposed Doppler frequency spread estimation methods in conjunction with the CNR estimation method can achieve the higher estimation accuracy even under the lower CNR with lower computation complexity. This paper presents various computer simulation results to demonstrate the effectiveness of proposed method.