Iterative joint synchronisation and turbo-decoding

We consider the problem of synchronisation (i.e. carrier phase and symbol timing recovery) and decoding in coded systems, especially turbo-coded systems. We introduce a new concept "a-priori probability aided estimation", where the log-likelihood ratio obtained from a MAP decoder (as used in turbo-decoding) is used to aid estimation in an iterative synchroniser/decoder. We illustrate this in detail with reference to carrier recovery in a turbo-coded BPSK system, and demonstrate a substantial performance advantage over conventional separate synchronisation and decoding.