Trellis-Coded OAM-QAM Union Modulation with Single-Point Receiver

Union modulation scheme is proposed and analyzed based on trellis-coded modulation, orbital angular momentum (OAM), and quadrature amplitude modulation (QAM). Specifically, source data symbols are mapped to a 3-D constellation diagram consisting of OAM modes and QAM constellation. Moreover, the constellation point is jointly detected by an OAM single-point detector and a pruned Viterbi decoder at the receiver. Compared with standalone modulation schemes, larger Euclidean distance with lower bit error rate (BER) and lower complexity can be obtained. Furthermore, the simulation results show that the single-point detection is more robust than the phase-gradient detection at a large receiving distance.