Blind Symbol Timing Estimation for OFDM/OQAM Systems

In this correspondence, we consider the problem of blind symbol timing (ST) estimation for pulse-shaping orthogonal frequency division multiplexing (OFDM) systems based on offset quadrature amplitude modulation (OQAM). In particular, under the assumption of low signal-to-noise ratio, the joint maximum-likelihood (ML) phase offset and ST estimator for additive white Gaussian noise (AWGN) channel is derived. Since the phase estimate is in closed form, the ST estimate requires a one-dimensional maximization procedure with respect to a continuous parameter. Specifically, the ST estimate depends on both the unconjugate and the conjugate correlation function of the transmitted OFDM/OQAM signal and exploits the cyclostationarity of the OFDM/OQAM signal that is related to the bandwidth of the considered pulse-shaping filter. In particular, for the adopted pulse-shaping filter the OFDM/OQAM signal results to be stationary with respect to its unconjugate correlation function and, then, the ML cost function depends only on the conjugate correlation function. The performance of the proposed ML estimator is assessed via computer simulations both in AWGN and multipath channel.