Convergence Property Analysis for Multiuser Detection Schemes in SCMA Systems Based on EXIT Chart

Thanks to the sparse structure of sparse code multiple access (SCMA), a message passing algorithm (MPA) was proposed to efficiently approximate the optimum maximum a posteriori scheme. Based on a lack of theoretical analysis on the convergence property of parallel and serial strategies, in this paper, extrinsic information transfer (EXIT) is proposed to analyze the convergence property. First, the SCMA detector is divided into two parts: one function node decoder and one variable node decoder, and then, analyzing the decoders’ EXIT convergence property. Finally, by comparing the EXIT curve of the two kinds of algorithms, the number of iterations required to achieve convergence state is estimated. Simulation results validate the EXIT chart analysis.