Minimum-Variance-Based Blind CFO Estimator for OTFS Systems in V2X Communications

This letter proposes a new low-complexity blind carrier frequency offset (CFO) estimator for orthogonal time frequency space (OTFS) systems in vehicle-to-everything (V2X) communications. The estimator leverages the statistical properties of the element-wise modulus vector of OTFS symbols in the delay-Doppler (DD) domain. It is shown that, under ideal CFO compensation, the variance of this vector reaches its minimum while the expectation reaches its maximum. Based on this finding, the objective function for CFO estimation is formulated. Moreover, to reduce complexity and meet the real-time requirement of V2X communications, the expectation of the objective function is approximated as its mean via the law of large numbers. Simulation results demonstrate that, for sufficient signal lengths, the proposed estimator achieves lower complexity while achieving higher estimation accuracy under low signal-to-noise ratio (SNR) conditions compared with existing estimators.