Frequency Sharing And Interference Suppression For Multi-satellite Systems

With the development of 5G and 6G,the number of users are increasing and communication data rates are becoming larger.When the terrestrial mobile communication system can no longer meet the requirements,it is necessary for the satellite communication system to increase the communication capacity.At the same time,if the terrain conditions are harsh and the traffic in these areas is rare,it needs the satellite communication system to widen the communication coverage area because the base stations are too expensive to establish for little service.In addition,in order to enhance the confidentiality and anti-interception of military communications,the structure design of satellite communication systems is also particularly important.In order to satisfy the above requirements,large scale low-earth-orbit satellite constellations already becomes a trend.As the number of satellites increases,time,space and spectrum resources become more and more crowded.As many countries are competing for spectrum resources,the rational use of spectrum resources is extremely significant.Due to the limited spectrum resources,it is inevitable to face the problems of same frequency interference.In addition to the co-chanel interference within the same satellite system,the interference also occurs when different satellite systems are close in space and time,so this problem has become the focus in recent years.This dissertation studies the problem of reducing the same frequency interference between geostationary earth orbit(GEO)satellite systems and non-geostationary earth orbit(non-geostationary orbit,NGEO)satellite systems.This dissertation analyzes the interference scenes of GEO satellite system and NGEO satellite system working in the same frequency band,and respectively establishes the mathematical model of interference for feed links and user links.Simulation analysis is performed through STK to provide support for verifying the performance of interference suppression technologies.There are many techniques to suppress the same frequency interference between the GEO satellite system and the NGEO satellite system.This dissertation considers the interference problem of the NGEO satellite system to the GEO satellite system and supresses the interference.Power control can suppress to a certain degree.Although power control technology is mature in the same system,there are still co-chanel interference problems to be solved when it is used in multi-satellite systems.In this dissertation,the traditional centralized power control and distributed power control are utilized to solve the problems of same frequency interference between different satellite systems,and a new adaptive power control scheme is proposed.The simulation of the user's down-link shows that the centralized adaptive power control technology has better performance,but it needs the control center to control the NEO satellite system.In addition to the traditional power control,game theory based power control is another new idea.According to the existing Koskie-Gajic algorithm,a new utility function is established in this dissertation,and two algorithms are proposed to realize power control according to the two power iterations.Through simulation comparison,the performance of adaptive power control algorithm 2 based on game theory is better than distributed adaptive power control,but lower than centralized adaptive power control.