Close-to-optimum joint carrier and symbol synchronization for trellis-coded two-dimensional modulation schemes

The authors deal with joint carrier and symbol synchronization of trellis-coded two-dimensional (in-phase and quadrature) modulation schemes. The linearized tracking performance of a decision-aided maximum-likelihood-oriented synchronizer is evaluated. For trellis codes yielding uncorrelated channel symbols the tracking performance is shown to be essentially code-independent and very close to the theoretical optimum. Sufficient conditions on trellis codes for delivering uncorrelated channel symbols are derived, and many interesting trellis codes proposed in the literature are shown to fulfil these conditions.<>