A flexible iterative log-mpa detector for uplink scma systems

. The development of the communications industry is changing with each passing day. At present, 5G research work is in full swing. In the SCMA (Sparse Code Multiple Access) system, this paper proposes a flexible iterative logarithmic domain message passing algorithm(FI-Log-MPA) aiming at the traditional logarithmic domain message passing algorithm to magnify the number of iterations in the codeword decision process, which results in a waste of running resources. The algorithm determines whether to perform subsequent iterations by adding a link to determine the convergence rate of the codeword during the update process of the variable node. If the codeword convergence rate is lower than a preset threshold, the iteration is stopped, otherwise the iteration is continued. Based on the principle of the optimization algorithm, we built a SCMA and NOMA (Non-Orthogonal Multiple Access) simulation platform to verify that the algorithm can effectively reduce the number of iterations. Although there is a loss in bit error rate and throughput performance, it remains at the same order of magnitude. In general, the complexity is reduced, and the decoding performance is optimized.