Noncoherent decoder-assisted frame synchronization for packet transmission

We propose a noncoherent, decoder-assisted (NDA) frame synchronizer, a two-stage synchronization scheme based on the list-synchronization principle, for the serially concatenated coded differential modulation (SCCD) system in the packet transmission. For the first stage, we derive a suitable noncoherent, maximum likelihood (SNML) rule, more effective for the noncoherent decoder´s operating region of smaller channel phase changes, to provide a reliable list of potential frame starting positions. For the second stage, we propose a hybrid sync method by exploiting the combined sign difference ratio (SDR) and sync word Log-likelihood ratio (SW LLR) information to obtain more reliable final decisions and reduce computational complexity. Performance and complexity of the proposed scheme are evaluated under constant and time-varying phase changes in the AWGN channel via Monte Carlo simulation.