Feedforward Joint Clock and Phase Estimation Schemes for SOQPSK-Type Signals

Feedforward algorithms are investigated for estimating carrier phase and symbol timing in SOQPSK modulations. We begin showing that an SOQPSK signal with correlated data symbols is equivalent to a conventional CPM signal with independent data. Then, based on maximum likelihood criteria, we derive joint phase and timing synchronization schemes that are suitable for full digital implementation. The performance of the proposed algorithms is investigated by simulation and the results are compared with Cramer-Rao bounds. It turns out that the timing estimation accuracy is very close to the theoretical limits. Also, the proposed estimators largely outperform other synchronizers already known in literature with a comparable complexity.