Low Complexity Decoding Algorithm for Uplink SCMA Based on Aerial Spherical Decoding

As a new non-orthogonal multiple access technology for 5G massive machine type communication scenario, the sparse code (SCMA) has greatly improved spectrum efficiency due to high connection density. SCMA combines QAM (Quadrature Amplitude Modulation) modulation and spreading into codebook set obtain forming gain. The user binary bit data is directly mapped multi-dimensional codewords in transmitter. receiver uses message passing algorithm (MPA) multi-user detection achieve efficient decoding. However, MPA good solution SCMA, though its complexity limits application practical systems. In order reduce of MPA, this paper proposed low-complexity decoding based on serial spherical (SSD-MPA), which enhanced practicability system. SSD-MPA took account distribution characteristics Gaussian noise reliability constellation points, only updates trusted point messages nodes within radius. At same time, it used strategy speed up convergence rate. simulation results have shown that when radius sets properly, reduces by about 2/3 compared with original performance was almost lossless.