Optimum Symbol Synchronization

Abstract

Although most closed-loop synchronizers employ maximum likelihood estimators for symbol value decisions, in general, their symbol timing estimates are not optimum. It would seem only natural that an optimum timing estimator would choose interval partitions based on maximizing the observed sample signal-to-noise ratio. The symbol synchronizer described below achieves optimum performance when decisions on present symbol values are based on current and previously-received symbol samples. This procedure attempts to reestablish the interval independence criterion, thereby reducing timing estimator variance. The realization presented is motivated by an open-loop maximum a posteriori (MAP) structure analysis.