A Beam Search-Based Channel Allocation Method for Interference Mitigation of NGSO Satellites with Multi-Beam Antennas  
[PERSON]  
1 School of Aerospace Engineering, Tsinghua University, Beijing 100084, China;  
1 hj:[EMAIL_ADDRESS]  
[PERSON]  
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[PERSON]  
1 School of Aerospace Engineering, Tsinghua University, Beijing 100084, China;  
1 hj:[EMAIL_ADDRESS]  
Footnote 1: email: {liren2 [PERSON]_Xuesen_Laboratory of Space Technology, China Academy of Space Technology, Beijing 100094, China;  
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Footnote 2: email: {liren2 Qian_Xuesen_Laboratory of Space Technology, China Academy of Space Technology, Beijing 100094, China;  
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Footnote 3: email: {liren2 [PERSON]_Xuesen_Laboratory of Space Technology, China Academy of Space Technology, Beijing  
(Iridium, Globalstar, etc. ), due to the low cost of manufacturing and launching, the NGSO constellations now designed are typically made up of thousands of satellites. With deeper worldwide participation in the exploration of the application of NGSO communication satellites, it is predicted that, by the year 2029, there will be nearly 57,000 satellites orbiting in low Earth orbit, over 80 percent of which will belong to the USA. Compared with traditional GSO satellites used for communication, large NGSO satellite communication constellations possess four competitive edges. The first is global seamless coverage areas [15]. It is not suitable to traditionally build the internet for most spaces on the land, on the ocean, and in the sky, whereas the satellite communication systems can achieve seamless coverage easily. The second is low transmission latency [16]: for many commercial customers, there exists a long transmission delay when the information is transmitted worldwide. The transmission speed through optical fiber cable is two-thirds that of light in vacuum, thus tens of milliseconds of time delay can be avoided by transmission from satellites above. The third is low expense: compared with constructing communication infrastructure for 5G stations and undersea optical fiber cable, reusable launching rockets that can send tens of satellites into space at once and low-priced satellite manufacturing costs embody apparent advantages. The last is Broadband [17]: technologies such as utilization of high frequency and frequency reuse allow higher communication capacity. Nevertheless, with the coexistence of multiple GSO and NGSO satellite communication systems, more and more sophisticated potential interference would occur. To ensure the quality of service of different systems, interference analysis and avoidance have become crucial in the construction of NGSO satellite communication systems. Rapid augmentation of NGSO communication satellites makes the requirement for spectrum resources utilized by them rather urgent. As a consequence, countries around the world are positively studying NGSO satellite communication technologies to take a share in spectrum resources. After all, by the end of this decade, the communication spectrum and orbit resources will have become much scarcer than ever before [18]. In this context, according to certain rules, researchers have put forward many solutions. High throughput satellite (HTS) is currently one of the research highlights in satellite communication to improve spectrum efficiency, which is formerly put forward by American consulting company Northern Sky Research. In comparison with traditional communication satellites, the HTS is equipped with multi-beam antennas which would significantly improve the total capacity of satellites with identical spectrum resources. Other than that, spectrum sharing is currently recognized as one of the crucial technologies to enhance the utilization efficiency of frequency bands. However, it probably results in co-frequency interference between different communication systems [19].