Covariance-Fitting-Based Blind Carrier Frequency Offset Estimation Method for OFDM Systems

Abstract

In this paper, a new unsupervised carrier frequency offset (CFO) estimation method is proposed for orthogonal frequency division multiplexing (OFDM) systems using constant modulus constellations. Under the assumption that the channel variation is slow within two adjacent OFDM symbols, the influence of the channel on corresponding subcarriers of the two OFDM symbols will be the same. Utilizing this feature, a robust cost function is formulated based on covariance fitting criterion between two nearby OFDM symbols, and the CFO is estimated by minimizing this objective function. The mean square error (MSE) and bit error rate (BER) performance of the proposed covariance-fitting-based CFO estimation method is compared with that of the prominent conventional estimation schemes under noisy multipath channels with high delay spreads and Doppler spreads. The effect of channel length on the performance of the proposed estimator is also investigated. Based on Monte Carlo simulations, it is shown that the proposed method is robust under different channel conditions and provides more accurate CFO estimates.