Design And Simulation Of Mobile Handover In Satellite-Terrestrial Integrated Networks Based On 5G

In recent years,the explosive growth of various services has promoted the innovation and development of 5G mobile communication networks,but it is difficult to meet the requirements of global services using only terrestrial infrastructure.Satellite communication system has the advantage of full coverage,and the close interaction with terrestrial network forms Satellite-Terrestrial Integrated Networks(STIN),which can solve the problem that current mobile communication system cannot cover remote areas.However,the high speed movement of LEO satellites and frequent handover of user terminals pose challenges to the efficiency of beam management and inter-satellite management.To this end,this thesis explores the terminal handover mechanism in 5Gbased satellite-ground converged networks,as follows.1.To address the problems of complex beam handover signaling and low terminal applicability,beam handover management in 5G is studied,and a 5G-based beam handover scheme for low-orbiting satellites is proposed.In order to provide better access to the beam for handover terminals,a multi-service adaptive dynamic reserved channel strategy is proposed,i.e.,two thresholds are set for new call users and handover users,and protected channels are dynamically reserved according to the beam handover blocking rate,and new call users borrow protected channels with a certain probability according to the channel occupation to improve the channel utilization.2.To address the existing problem of large inter-star handover delay,an inter-star pre-switching scheme based on the Xn interface of 5G is proposed.By collecting the reference signal received power value in a period of time by the terminal and predicting the next moment power value by using linear regression equation,the switching application is reported in advance by the improved switching judgment event,thus reducing the interplanetary handover waiting delay and improving the handover success rate.For the problems of handover frequency and load balancing in the star-ground scenario,the four attributes of signal reception quality,elevation angle,service time and satellite load are considered comprehensively to form a multi-attribute decision problem,and the best target satellite is solved by fuzzy hierarchy method to improve the switching efficiency.3.Develop a simulation platform for LEO handover system based on handware-inthe-loop simulation software EXata.Firstly,we build the Globalstar satellite constellation by STK,and then we design and simulate the modules of beam handover and intersatellite handover scheme in EXata,which mainly includes three parts: terminal side,satellite side and 5GC.The test results show that the beam handover strategy improves the success rate of new and handover users,and the inter-satellite pre-switching scheme can reduce the handover delay by 21% compared with the Xn handover scheme,and the inter-satellite handover algorithm outperforms the traditional handover strategy in terms of comprehensive performance.