Blind full-range frequency offset estimation for differential OFDM

This paper proposes a novel blind carrier frequency offset (CFO) estimator for differential OFDM. By separating the normalized CFO into integral and fractional parts, our CFO estimation is carried out in two successive stages. In the first stage, we take advantage of differential coding and the finiteness of signal constellation to derive a channel-independent cost function whose minimization leads to an accurate estimate of the fractional part. It is proved that under certain mild assumptions, the identifiability of the fractional part can be guaranteed with probability one. After compensating the fractional part, the second stage estimates the remaining integral part with the aid of a judiciously designed initial block of differential coding. Combining these two stages, the proposed estimator is shown capable of offering full-range CFO estimation without relying on any training or virtual subcarriers. Another salient feature of the proposed estimator is that accurate CFO estimation can be achieved with two received data blocks only, making it very attractive especially for short-burst communications. The merits of our CFO estimator have been confirmed by theoretical analysis as well as corroborating simulations.