Turbo Synchronization for Serially Concatenated CPM

By approximating continuous phase modulated (CPM) signals with a small set of nonsymmetric nonorthogonal exponential functions, we have previously proposed a data-aided time and phase synchronizer that works well for all CPM schemes [1]. This paper extends this non-iterative data-aided synchronizer to its iterative decision-directed counterpart, for serially concatenated CPM systems. To prevent false locks in synchronization process, a preamble and pilot symbols are used in combination with the decision-directed technique. Simulation results show that the proposed turbo synchronizer is robust in acquiring and tracking both time-invariant and time-variant timing and phase errors at low signal-to-noise-ratios.