Analysis And Avoidance Method Of Co-frequency Interference Between Large Scale Non-geostationary Internet Satellite Constellations

Large-scale non-geostationary orbit(NGSO)satellite system has the characteristics of low transmission delay,global coverage,etc.,which has become the focus of research this year.However,a large number of NGSO satellite systems are deployed on a large scale,which leads to the shortage of frequency and orbit resources.NGSO satellite systems will cause serious co-frequency interference.The existing interference analysis and interference avoidance methods are mainly proposed between geostationary orbit(GSO)satellites and between GSO and NGSO satellites systems.In terms of largescale and highly dynamic inter-system interference of NGSO,there are problems such as lack of reasonable modeling,complex calculation and difficulty in accurately describing interference feature.In view of the above problems,the characteristics of intersystem interference scenarios,interference evaluation methods and airspace interference avoidance methods of NGSO constellation are studied.Firstly,considering the large number of satellites,time-varying relative positions and flexible beam characteristics of the future large-scale NGSO constellation system,in this paper,the frequency,beam and orbit characteristics of the existing typical large-scale NGSO constellation are sorted out to obtain three typical interference scenarios: interference scenarios between feed links,interference scenarios between user links,and interference scenarios between feeder and user links.Furthermore,the characteristics and similarities of interference in different scenes are analyzed.In order to analyze the interference severity of large-scale NGSO constellation systems,based on the classical interference analysis index stipulated by International Telecommunications Union(ITU),The degree of interference between two typical NGSO satellite constellations,One Web and Starlink,was evaluated.Through simulation analysis,different NGSO constellation systems will cause very serious interference to other systems with the same frequency and even cause long time communication interruption.At the same time,the influence of simulation step size,ground station isolation distance and latitude location modeling parameters on the results is simulated and analyzed,which provides guidance for constellation design and ground station layout in the future.Finally,for the serious co-frequency interference between NGSO constellation systems,traditional interference avoidance methods have great limitations in the face of global coverage and high dynamic characteristics.Based on the development trend of phased array flexible beam control,an interference avoidance method using spatial processing is proposed.Aiming at the fatal main lobe interference avoidance problem,the method turns main lobe interference into side lobe interference by switching the beam of earth station to other satellites within the visual range.Then it uses adaptive beamforming method of side lobe null broadening to suppress side lobe interference in high dynamic environment.The interference scenario between One Web and Starlink constellations is used for simulation.The results turn out that the proposed method can effectively reduce the interference between NGSO constellations and improve the link quality.