Defining performance limits for turbo-code assisted synchronization in DVB-S systems

The operating Es/No of the European Digital Video Broadcasting over Satellite (DVB-S) system can be reduced by utilizing turbo codes, although this reduces the performance of both carrier and symbol synchronizers. While maximum likelihood decision directed (ML-DD) feedback algorithms for both carrier and symbol synchronization can be shown to approach the Cramer-Rao bound (CRB), at reasonable Es/No, at low Es/No incorrect decisions reduce their performance. If improved decisions are made available to the algorithms then even at low Es/No the CRB can be approached. By utilizing a turbo code to provide improved symbol estimates tracking performance can be improved. In a practical system, however, there is an unavoidable delay caused by the decoder, which reduces tracking performance. This paper is concerned with examining the tradeoff between improved decisions and unavoidable delay. Limits are shown for performance and interleaver size to make this approach to the synchronization problem practical