Research On Multi-User Detection Algorithm For 5G Oriented Uplink SCMA System

In recent years,the mobile Internet of Things technology is in a stage of rapid development,and traditional multiple access technology cannot support the access of massive terminal devices in the future.Sparse Code Multiple Access(SCMA)technology,as a multiple access solution in the 5th Generation mobile communication technology(5G),can adapt to the future mass connection scenario.In this thesis,the research on SCMA technology is carried out,and the optimization of multi-user detection complexity in SCMA is mainly optimized.The details are as follows:Aiming at the problems of high complexity and long delay of Message Passing Algorithm(MPA),a serial MPA algorithm based on node stability judgment is proposed.The algorithm uses a serially updated message delivery method to increase the stability of the resource node before and after the iteration,and decodes the codeword information that has reached the stability after the update in the node in advance.By reducing the number of iterations of some codeword information,the algorithm delay and complexity are reduced.Simulation results show that the information convergence speed and complexity performance of the proposed algorithm are better than the serial MPA algorithm.For the two problems of low error performance and high complexity of MPA detection algorithm based on spherical decoding(SD)under low SNR conditions.An MPA detection algorithm based on Optimization sphere decoding(OSD)is proposed.The algorithm uses a spherical decoding algorithm to filter the synthetic constellation points on the resource nodes,reducing the number of users superimposed on the resource nodes.By comparing the distribution law of the probability density function of synthetic constellation points under different signal-to-noise ratios,a scaling factor is designed,and scaling processing is added to the probability density function.Simulation results show that the error performance of the given algorithm are better than the SD-MPA algorithm.