| With the growing demand for communication services,Low Earth Orbit Satellite Communication(LEO-SATCOM)system has become a hot research topic because of its wide coverage,short propagation delay,low path loss and rich resources.As the key technology of LEO-SATCOM System,satellite constellation design has a great impact on its coverage,deployment cost,network architecture,link transmission and service quality.Therefore,in this thesis,the capacity of LEO-SATCOM System is studied based on the number of users and satellite throughput respectively,and the satellite constellation is designed for different scenarios combined with different objective functions.The details are as follows:Firstly,a capacity-oriented LEO satellite constellation design scheme for emergency area coverage is proposed to solve the problem that the rapid demand of communication capacity in disaster area easily leads to the communication interruption of ground users.Firstly,the Satellite Communication Capacity(SCC)is defined based on the total number of satellites,satellite connection probability and data transmission rate,and the User Demand Capacity(UDC)is defined based on the population distribution,economic development and communication market size of the target area.Then,taking the satellite system capacity,design cost and coverage weight as the optimization objectives,and the comparison between SCC and UDC as the new limiting conditions,the optimization model is constructed combined with the conventional satellite optimization parameters.Finally,the constellation design scheme is compared with other LEO-SATCOM System.The simulation results show that the proposed satellite constellation design scheme can meet the local high-capacity requirements of disaster area,and the number of satellites and constellation design cost are less.Secondly,in view of the difficulties in satellite system capacity analysis caused by the rapid movement of satellites to the earth and the rapid growth of network services,a capacity oriented global coverage satellite constellation design scheme is proposed considering the interference factors of neighboring satellites.Firstly,the neighbor interference model in Leo satcom system is constructed,and the interference distance of adjacent star is transformed into the maximum visible distance between stars expressed by longitude latitude.Then,from the perspective of throughput,based on the satellite link type and transponder working system,the satellite system capacity is analyzed.After taking the coverage level as the optimization objective,three constellation design schemes with different weight proportions are obtained based on the linear weighting method.Finally,the constellation design scheme is simulated and compared with Iridium constellation.The simulation results show that all three satellite constellation design schemes can achieve the global coverage target well,and the number of satellites required is less. |
