Research On Frequency Compatibility For Large-Scale Low-Orbit Satellite Constellations

With the rapid development of commercial aerospace and the reduc-tion of satellite launch costs,large-scale low earth orbit(LEO)satellite constellations have been paid more and more attention.Frequency is a pre-requisite for the normal operation of communication satellites.To ensure the smooth development of large-scale LEO constellations,it is urgent to study the frequency compatibility for large-scale LEO constellations.Based on the system characteristics of large LEO constellations,geo-stationary satellite orbit(GSO)satellite communication systems,and 5G millimeter wave communication systems,this thesis takes the frequency compatibility evaluation between systems as the starting point.The effi-cient analysis of interference factors,effective mitigation of harmful inter-ference and multi-dimensional description of dynamic interference are studied.The main research contents are summarized as follows:1.The interference factors between large-scale LEO constellations and GSO satellite communication systems is studied.In view of the large number of satellites of large-scale LEO constellations and the high com-plexity of interference analysis between systems,the dual-precision inter-ference analysis method based on spatial location probability is applied to study the influence of the LEO earth station deployment models and the geographic locations of the GSO earth station on interference.The simula-tion results show that the geographic location of the GSO earth station has a greater influence on the interference,and when the GSO earth station is placed near the equator,the harmful interference will occur.2.The interference mitigation between large-scale LEO constellations and GSO satellite communication systems is studied.Aiming at the severe interference near the equator,an interference mitigation algorithm based on Q-Learning dynamic allocation of satellite beams is proposed.The al-gorithm explores and learns the satellite beam allocation scheme,and ob-tains the final satellite beam allocation scheme based on the learning expe-rience data iteratively.Simulation results show that the proposed algorithm has a significant performance improvement in minimizing the performance loss of LEO satellite constellation compared with the power control based interference mitigation algorithm in the case of strong harmful interference.3.The interference evaluation between large-scale LEO constellations and 5G millimeter wave systems is studied.Different from the static inter-ference scenario between the GSO satellite communication system and the 5G millimeter wave systems,the interference between the large-scale LEO constellations and the 5G millimeter wave systems is difficult and dynamic,so that the traditional static interference evaluation method and evaluation dicators will no longer apply.To resolve this problem,a dynamic interfer-ence analysis framework is proposed firstly.Then,on the basis of analyzing the applicability,the interference characteristics between systems are re-fined.In terming of time-space and the overall system,the interference evaluation indicators are defined and evaluated,such as the probability of harmful interference,system availability and single beam throughput.Fi-nally,simulation performance analysis is performed based on the proposed interference evaluation indicators.