Efficient estimation of carrier and sampling frequency offsets in OFDM systems

This work studies the problem of jointly estimating the carrier frequency offset (CFO) and sampling frequency offset (SFO) in orthogonal frequency-division multiplexing (OFDM) systems. Two scenarios are considered: known channel impulse response (CIR) and unknown CIR. It was shown in previous works that the exact joint maximum-likelihood estimate (MLE) of the CFO and the SFO requires a two-dimensional search. In this work, we present a new estimation method which uses the Taylor expansion of the MLE cost function, combined with the best linear unbiased estimator, to obtain an estimator which does not require such a search. Numerical simulations demonstrate that the new method approaches the corresponding Cramér-Rao bound for a wide range of signal-to-noise ratios, and have superior performance compared to all other existing methods for approximating the joint MLE solution, while maintaining a low computational complexity.