A Fine Blind Frequency Offset Estimator for OFDM/OQAM Systems

Like other orthogonal frequency division multiplexing (OFDM) systems, OFDM systems based on offset quadrature amplitude modulation (OFDM/OQAM) are very sensitive to carrier frequency offset. In this paper, a new blind carrier frequency offset estimator is developed for OFDM/OQAM systems by exploiting the noncircularity of the received OFDM/OQAM signal. Since the received signal exhibits conjugate cyclic frequencies at twice the carrier frequency offset, the frequency estimator is designed by maximizing a cost function expressed in terms of the sample conjugate cyclocorrelations. The theoretical asymptotic (large sample) performance analysis of the proposed estimator is established. Computer simulations are presented to illustrate the performance of the estimator. It is shown that the proposed estimator is very accurate whenever it is well initialized. Therefore, the proposed estimator appears to be very well adapted for a tracking mode rather than for an acquisition mode.