Research On Sparse Code Multiple Access Detection Algorithm For 5G Grant-Free Scheduling

For the future 5G high-speed,low-latency and massive access services,traditional grant transmission mechanisms and multiple access technologies have been unable to solve.The grant-free transmission mechanism can effectively simplify the signaling process and has obvious advantages in reducing access delay.Meanwhile,the non-orthogonal multiple access technology that has emerged in recent years can effectively improve spectrum utilization and increase the number of user accesses.The more typical one is the Sparse Code Multiple Access(SCMA)technology.In this paper,the grant-free transmission mechanism and SCMA technology are studied separately,and the optimization solution is proposed.Finally,the two technologies are combined to form a sparse code division multiple access detection scheme for 5G grant-free scheduling.Meanwhile,combined with the simulation software,the performance and complexity analysis of the optimization scheme are given.The performance of the grant-free transmission receiver is mainly reflected in the missed detection rate and false alarm rate.This paper proposes an active user detection scheme based on frequency-selected channel gain information.Compared with the traditional scheme,this method introduces the Reactive Active UE Detection(RAUD)module,which can effectively analyze the frequency selection gain information of the channel and improve user status detection accuracy.Compared with the traditional scheme without RAUD module,the new scheme has lower missed detection rate and false alarm rate.The Markov Chain Monte Carlo(MCMC)algorithm has the advantage of low complexity compared with the Message Passing Algorithm(MPA),and is more suitable for solving the problem of excessive computational complexity of the SCMA receiver.In this paper,the MCMC algorithm is optimized from the perspective of serial and parallel.The Multi-dimensional Disturbance MCMC(MD-MCMC)algorithm based on multi-dimensional perturbation and the Different Initial Point MCMC(DIP-MCMC)algorithm based on Hamming distance initialization are proposed.Compared with the traditional MCMC algorithm,there is performance improvement.At the end of the paper,the grant-free transmission scheme proposed in this paper is combined with the improved MCMC algorithm to form a sparse code division multiple access transmission system based on the uplink free scheduling mechanism.