Theory And Application Of SCMA Multi-User Detection

The scientific and technological progress of modern society will inevitably require the continuous development and iteration of communication technology,which will bring about massive data transmission and massive data traffic interaction.The development of communication systems must be able to meet the needs of technological development.For example,compared with the fourth-generation mobile communication system,the advantages of the currently operating 5G communication lie not only in the order of magnitude improvement in the spectral efficiency of the system,but also in the ability to meet a large number of user access and low-latency performance.At the same time,the user link density of 5G compared with 4G communication system must also be an order of magnitude difference.Sparse code multiple access(SCMA)technology as a non-orthogonal multiple access technology(Non-Orthogonal Multiple Access,NOMA),SCAM introduces sparse code The code domain distinguishes users,combines low-density spread spectrum(Low-Density-Signature,LDS)and high-dimensional quadrature amplitude modulation technology,and then adjusts and selects the most suitable codebook through appropriate operating factors.Different codebooks are transmitted,that is,due to the sparsity of the codebooks,the resource allocation of users is more effective,so the spectrum utilization effect is better,and the biggest advantage of Quadrature Amplitude Modulation(QAM)is that it can be zoomed out.The distance between the constellation points ensures that it is more conducive to the anti-interference between the demodulator and the user in the case of limited resources.This paper introduces the technical background of NOMA and OMA,elaborates the advantages and disadvantages of these two technologies in the next generation wireless communication technology,introduces the research status of NOMA technology,and introduces the various multi-user detection algorithms of the SCMA system.Improvement methods and research hotspots.This paper briefly describes the development history and advantages of the SCMA system,introduces the mapping process of the system codebook,the factor graph and factor matrix,and the conditions that the factor graph should meet under the condition of regular and irregular conditions,and introduces the codebook design of the system.and mapping matrix and constellation design,as well as the formula principle of MAP algorithm and algorithm,then simulate and analyze the traditional multi-user detection algorithm in SCMA system,introduce the background of the algorithm,formula principle,algorithm advantages and disadvantages,performance simulation and analysis.Iterative performance curve analysis.This paper proposes an improved method based on the traditional detection algorithm.Before each iteration of the previous algorithm,a threshold value is judged,and the threshold value reflects the similarity of the results of the previous and current iterations of each algorithm iteration.When the set threshold is reached,it can be considered that the performance requirements of this iteration are met,and the previous iteration information is used to abandon the current iteration process to achieve the purpose of reducing complexity.Through the reasonable selection of the similarity threshold,it is possible to choose between different algorithm complexity and performance in different application scenarios.The article compares the performance of the MPA algorithm Max-Log-MPA algorithm and the BER-SNR performance simulation of the SD-MPA algorithm under different similarity thresholds,as well as the BER and iteration times curve,and compares the three algorithms under the same parameters to verify the feasibility of the similarity threshold algorithm.