Research On Access Handover And Hybrid Routing For Terrestrial-satellite Integrated Networks

With the rapid advancement of global communication business and the“One Belt One Road”information infrastructure,it has become extremely important to pro-vide full-time,global coverage and high-speed communication services.The terrestrial-satellite integrated network(TSIN)will comprehensively utilize satellite and terrestrial network communication resources to achieve wide-area coverage and network intercon-nection,which has great significance for”one belt and one road”infrastructure and the development of 6G network.Due to the frequent handover and high transmis-sion delay caused by satellite-terrestrial link intermittent,topological time-varying and high-mobility satellite of TSIN,this thesis studies the access satellite handover,hybrid routing and non-orthogonal multiple access of TSIN for improving communication rate and transmission delay.Our research work is organized as follows:(1)To solve the problem of frequent handover and low handover success rate,a Qo E-driven access satellite handover mechanism is proposed to achieve the seamless communication of high-speed user terminals(UTs).Accordingly,to ensure the service duration,a spatial relationship coupling model is proposed to predict relative motion pattern between UT and satellites;To improve the effectiveness of handover,the han-dover probability expression of terrestrial terminal is given,then an available channel estimation model is developed based on the mobility pattern of adjacent satellites.Fi-nally,the selection of next service satellite is constructed as a multi-criteria problem,by using Qo E quantitative model,reinforcement learning is adopted to solve the opti-mization problem with the goal of maximizing UT~′s Qo E.The simulation results verify that the proposed method can achieve better handover times,handover success rate and end-to-end delay.(2)To solve the problem of link congestion and intermittent connection in the data transmission,a link state-aware terrestrial-satellite integrated network hybrid routing(TSHR)algorithm is proposed to achieve the effective management of transmission data and link resources.To characterize the data transmission process in time-varying topology of TSIN,a time-space topology graph is exploited to represent the relationship of link resources in time and space.Aiming at minimizing the end-to-end delay of network,a hybrid routing problem is modeled as an integer linear programming problem of link selection.To reduce the computational complexity in time-varying topology,by using the optimize design of time division,a time-space topology-based satellite routing selection problem model is proposed to obtain the optimal inter-satellite link connection planning for each time slot.According to the communication connection opportunity of satellite-ground link,a weighted bipartite graph model is constructed,and a hybrid routing algorithm based on link state awareness is proposed to obtain the optimal data transmission path.The simulation results demonstrate that under the congested terrestrial link,the proposed algorithm can effectively enhance the performance of data transmission delay,packet loss rate and throughput.(3)To solve the problem of interference and low resource utilization of ground terminal in TSIN,a dynamic divide grouping non orthogonal multiple access(NOMA)method is proposed to realize the user dynamic access under the limited spectrum resources.To solve the signal interference problem caused by the terrestrial-satellite integrated,an optimization model of joint user grouping,power control and resource allocation is constructed by using stochastic geometry theory.Aiming at the time-varying channel gain of satellite-terrestrial link,by constructing the relationship model between user elevation angle,beam angle and distance,a dynamic divide grouping algorithm is proposed to ensure the effective pairing of NOMA users.To obtain the optimal resource allocation,based on the designed optimal power control factor,a joint optimization algorithm of power allocation,beam channel and base station channel resource is proposed.Simulation results show that the proposed method can achieve higher throughput.