Optical SCMA coding technique based on fully interleaved 3D codebook

In the paper, an optical Sparse code division multiple access (SCMA) coding technique based on fully interleaved 3D codebook is proposed. We design a completely interleaved 3D codebook, the projection of all constellation points in the joint constellation on the XY, XZ and YZ planes are all interleaved, which is beneficial for making the complexity of message passing algorithm (MPA) lower. We used 3D amplitude and phase modulation (3D-CAP) to modulate 3D-SCMA signal, and then transmitted the signal with 7-core fiber. The feasibility of 3D-SCMA is proved by experiments. Our proposed 3D-SCMA has the same resource block efficiency as traditional two-dimensional SCMA: 150%. Due to the larger Euclidean distance of the 3D joint constellation, 3D-SCMA has lower decoding complexity and better reception sensitivity. Compared with 2D-SCMA, the complexity of 3D-SCMA is 66.66% lower and the receiving sensitivity is 3.5 dBm higher, which indicates that it not only reduces the complexity of the MPA algorithm, but also reduces the energy consumption of the system and saves the transmission cost. In this paper, optical 3D-SCMA is proposed creatively, which is an effective improvement on the traditional optical 2D-SCMA. This research can be applied in the future access network. •Extend SCMA codebook design to three dimensions.•The MPA complexity is reduced by 66%.•The receiving sensitivity was increased by 3.5 dBm.