Synchronization Algorithms for FBMC Systems

Filter bank multicarrier (FBMC) systems, such as FMT and OFDM/OQAM systems, can provide reduced sensitivity to narrowband interference, high flexibility to allocate group of subchannels to different users and a high spectral containment. On the other hand, as all the multicarrier modulation schemes, one of their major drawbacks is their sensitivity to CFO and symbol timing errors. In this thesis the problem of CFO and symbol timing synchronization is examined and new data-aided and blind estimation techniques are proposed. Specifically, it is presented a new joint symbol timing and CFO synchronization algorithm based on the LS approach. Moreover, the joint ML phase offset, CFO and symbol timing estimator for a multiple access OFDM/OQAM system is considered. It is also proposed a closed-form CFO estimator based on the best linear unbiased estimation principle for FMT systems. Blind CFO estimators based on the ML principle for low SNR are also considered and, moreover, a closed-form CFO synchronization algorithm based on the LS method is derived. Finally, it is also proposed, under the assumption of low SNR, the joint ML symbol timing and phase offset estimator

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

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