A Simplified Soft-demapping Scheme for Probabilistic Constellation Shaping
Yinhua Jia, Liangming Wu, Changlong Xu, Wei Liu, Hao Xu, Tom Richardson · 2024
Probabilistic constellation shaping (PCS) improves the spectral efficiency by adjusting the probability distribution of the transmitted symbols to match the channel characteristics. The conventional log-Maximum A Posteriori (log-MAP) algorithm can work for demodulation of PCS system by taking into account the probability of each constellation point. However, the conventional max-log-MAP algorithm cannot be applied directly. In this paper, a simplified soft-demapping scheme is proposed based on the max-log-MAP algorithm for the PCS system. The proposed scheme has a lower complexity than the log-MAP algorithm with acceptable performance loss. In addition, the distribution mismatch between transmitter and receiver is evaluated. The results show that four distributions are adequate for PCS-64 and PCS-256 to cover a wide range of signal-to-noise ratios.