Research On Optical Inter-satellite Link Assignment Method For Navigation System

In possession of an independent satellite navigation system is a top priority for a country's economic development and national defense construction.The development of the intersatellite links(ISLs)becomes an important direction for navigation systems.Optical communication links with higher communication capacity and faster transmission rates are more capable of meeting the needs of future navigation system.Considering the current situation that China is unable to deploy ground stations on a global scale,this paper mainly focuses on the optical inter-satellite link scenario of the navigation constellation network,and studies the ISL assignment method.This paper proposes a ISLs assignment algorithm that takes the distribution of access traffic into consideration,based on the ability of satellites to forward user traffic in the covered area,considering the impact of regional economic level and population density on user traffic,the model of ISLs access traffic forwarding volume was established.On this basis,a link assignment algorithm that satisfies the communication and ranging requirements of the navigation system was implemented,the priority was given to the overseas satellites covering the areas with dense access traffic distribution.Communication requirements are based on minimizing the communication delay,and the Position Dilution Of Precision(PDOP)is used to evaluate the system ranging performance.In order to measure the proposed ISLs assignment algorithm,this paper uses satellite orbit generation tool to build a constellation scenario,and compares the performance between the static link assignment and the dynamic link assignment method with MATLAB.The static link assignment can reduce the number of link switches,so the topology is more stable,but the system communication and ranging performance is not as good as the dynamic assignment method.Finally,considering that the optical ISLs may fail during work time,which may cause some problems of network reliability,by artificially setting 20% link failure in four extreme and two random failure scenarios for simulation.The simulation result shows that with the increase of the number of links under failure status,the delay performance will deteriorate to some extent,but the overall communication service ability of the system will not be affected,so as to verify the reliability of the network.