Research On Multiple Access And Resource Allocation Technology Of Integrated Terrestrial-Satellite Networks

With the rapid development of global economy and the commercialization of the fifth generation(5G)mobile communication technology,Integrated Terrestrial-Satellite Network has become a hot research content in the field of communication in recent years.However,satellite networks have been facing many problems,such as large number of users,shortage of available resources,limited processing power.How to meet the resource scheduling requirements of multi-layer and multi-satellite collaboration,widearea distribution,and service diversification,how to meet the increasing massive data access requirements of the Internet of things,and how to improve the resource utilization of satellite-ground fusion networks have become the focus of research.At the physical layer,sparse code multiple access(SCMA)technology is used to solve the problem of massive user access.At present,the research on SCMA technology mainly focuses on the reduction of the complexity of the multi-user detection algorithm and the design of the SCMA system codebook.Aiming at the low-complexity multi-user detection method of SCMA,based on the traditional message passing algorithm(MPA),combined with the advantages of the serial scheduling MPA algorithm and the parallel scheduling MPA algorithm,the improved group of WVN-MPA is proposed.The simulation results show that the algorithm can further reduce the computational complexity based on the existing MPA algorithm.Besides,for the SCMA system codebook design,an improved TCM-Latin codebook design is proposed based on the existing SCMA codebook design scheme.The improved TCM-Latin codebook can design each user codebook through TCM subset division and Latin matrix characteristic mapping.The simulation results show that the proposed algorithm can overcome the defect of unstable system performance and further improve the system bit error rate performance.In addition,for higher-dimensional codebook design,the constraints related to symbol power and phase in multi-dimensional codewords are introduced to design the extended mother codebook,and thus the CBRGAM codebook with constant bit rate and VBR-GAM codebook with variable bit rate are designed.The simulation results show that the CBR-GAM codebook has good performance and low computational complexity,while the VBR-GAM codebook can be flexible and meet the needs of different services.In the network layer,in order to solve the problems of difficult resource management,complex scheduling and coordination in the satellite-ground network,a genetic algorithm is adopted.The algorithm takes the fitness maximizationas the optimization goal of resource allocation in the three-layer heterogeneous satellite network of low earth orbit,base stations and users.The global optimal solution is searched through the iterative process of genetic algorithm,so as to find the excellent individual which can provide the best fitness.Theoretical analysis and simulation results show that compared with the greedy algorithm of matching game,the proposed algorithm has lower computational complexity and can effectively improve the resource utilization of the entire system.