16-QAM Probabilistic Constellation Shaping by Learning the Distribution of Transmitted Symbols from the Training Sequence. - A. Fallahpour; Fatemeh Alishahi; Amir Minoofar; Kaiheng Zou; Ahmed Almaiman; P. Liao; Huibin Zhou; Moshe Tur; Alan E. Willner (OFC, 2020)