Low Complexity Blind Carrier Phase Recovery for Probabilistically Shaped QAM

We propose a novel two-stage blind carrier phase recovery scheme tailored for probabilistically shaped QAM. Our algorithm is based on modifying the classic Viterbi&Viterbi (V&V) and maximum likelihood (ML) phase estimators by optimizing the blind decisions over the received symbols taking into account the probability distribution of the received signal. Our technique improves the standard V&V + ML in all conditions and outperforms the state-of-the-art blind phase search (BPS) algorithm for a constellation entropy <= 4. At the same time our implementation preserves the low complexity of standard V&V + ML. This results in a remarkable reduction in complexity of up to a factor thirty compared to BPS.