| Intersatellite link technology is the main development direction of global navigation satellite system in the future.The inter-satellite link can not only provide the observation value of inter-satellite ranging for autonomous navigation,but also undertake the tasks of communication and data exchange.Under the established constellation geometry network structure,the inter-satellite link topology defines the link building relationship and link building time between satellites,and the change of link stability,real-time data and autonomous navigation accuracy will be affected.It is still an urgent problem to design link pairs between satellites to ensure the delay of smaller links and the number of observations.This paper takes BDS-3 system as the research object,uses NSGA-Ⅱ algorithm and TOPSIS comprehensive evaluation to optimize the topology of inter-satellite link,and decides the optimal inter-satellite link scheme in different application scenarios.The main research contents and achievements are as follows:(1)The working principle of intersatellite link in BDS-3 constellation is analyzed,and the constellation configuration adopted by BDS-3 system is a hybrid constellation model consisting of 30 satellites,which consists of 24 earth medium circular orbit satellites(MEO),3 geostationary orbit satellites(GEO)and 3 geosynchronous orbit inclined satellites(IGSO)in the air.Considering that BDS-3 satellite builds a link in complex space,the working system of inter-satellite link is determined as time division multiple access mode,and the Ka band narrow beam phased array antenna is used to achieve the inter-satellite bidirectional ranging.In narrow-beam ranging,the transmitting star can establish an intersatellite link with only one satellite at a time.(2)When designing constellation network architecture based on BDS-3 system,the requirements of high-speed inter-satellite communication and high-precision time and distance measurement should be simultaneously met.Aiming at the inter-satellite networking structure and the inter-satellite link narrow-beam communication system,this paper analyzes the restriction conditions for any two satellites in BDS-3constellation to establish a successful link,and establishes three constraint submodels:antenna visibility,inter-satellite geometric visibility and distance.(3)Establish the intelligent optimization design process of the entire inter-satellite link configuration.The decision variables affecting the intersatellite link configuration were determined and the population initialization was completed.The sub-model of inter-satellite link network optimization index,weighted PDOP value,total number of satellite communication routes and total satellite load were established,and the optimization objective function values were calculated respectively.NSGA-Ⅱ algorithm was used to solve the inter-satellite link configuration by non-dominated sorting,crowding calculation and elite selection strategy.(4)Parameters are constantly optimized to achieve the optimal configuration of BDS-3 intersatellite link.8 intersatellite links in a single time slot and 12 intersatellite links in a single time slot were studied.Simulation analysis was carried out under different population sizes,genetic operator probability,threshold convergence and non-full constellation conditions respectively.The results show that: under the condition of 12 inter-satellite links in a single time gap,population size of 400,crossover probability of 0.1,mutation probability of 0.9,inter-satellite link configuration presents an optimal solution set.The optimal inter-satellite link topology scheme in different scenarios is determined subjectively and objectively by TOPSIS. |
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