Pilot-symbol assisted carrier synchronization: Cramer-Rao bound and synchronization performance

This contribution considers the joint estimation of the carrier phase and the frequency offset from a noisy linearly modulated burst signal containing random data symbols (DS) as well as known pilot symbols (PS). The corresponding Cramer-Rao lower bound (CRB) is derived. This bound indicates that it is potentially more accurate to estimate carrier phase and frequency from such a 'hybrid' burst than from a burst without PS or from the limited number of PS only. The new bound is compared with the performance of new and existing carrier synchronizers. We present the iterative soft-Decision-Directed (sDD) estimator with combined data-aided/non-data-aided (DA/NDA) initialization, which performs closely to the CRB, and provides a large improvement over the classical NDA estimator at low and moderate signal-to-noise ratio (SNR).