Research On Non-Geostationary Orbit Satellite Constellation Design And Inter-Satellite Link

With the rapid development of terrestrial wireless communication and Internet technologies in recent years, the network dimension and the number of users of these systems are increasing exponentially. As one of the most important modern communication technologies, satellite communication has achieved great progress during the past three decades. With the increasing demands for high mobility and quality of service (QoS) in broadband multimedia services, satellite communication networks adopting ATM and TCP/IP technologies are going to build a part of the future global mobile communication networks infrastructure. In this scenario, distinctions between satellite communication networks and terrestrial networks will cease to coexist in the universal mobile telecommunication system (UMTS), just like the convergence of the terrestrial fixed networks and the 3G mobile networks. Pervasive and ubiquitous information exchange is the primary purpose of creating an integrated UMTS. Mobility, QoS and global seamless coverage are the most important characteristics of UMTS. Satellite communications will play an important role in UMTS for their inherent advantages, such as wide area coverage, unique broadcast capability and no regional restrict. In practice, GEO satellite communication systems are incompetent to surppoting real-time multimedia services because of their intrinsic drawbacks. Hence, Non-geostationary orbit (NGEO) satellite communication system with lower transmission delay and attenuation becomes the one in focus. According to the peculiar techniques and development trends of the NGEO satellite communication systems, this dissertation mainly focuses on the NGEO satellite constellation design technologies and the characteristics of inter-satellite link (ISL), including global and regional coverage satellite constellation design, satellite constellation schemes study for NGEO tracking and data relay satellite system (TDRSS) and inter-layer inter-satellite link (ILISL) establishment strategies for two-tier LEO/MEO satellite networks.Chapter 1 is the preface. The development, status and perspective of the satellite communications and some key techniques of the mobile satellite communication networks are introduced concisely. The contents of this dissertation are also outlined. Chapter 2 outlines satellite constellation design. The theories behind the design of satellite constellation and some design considerations are presented. Two types of classical NGEO global coverage satellite constellation design methods, polar orbit constellation and inclined circular orbit constellation, are also briefly introduced.Chapter 3 studies the design of orthogonal circular orbit satellite constellation with global coverage. The precise constraint equation for polar constellation supporting coverage beyond specified latitude is derived. The relationship between the precise constraint equation and Beste's approximate constraint equation is analyzed and the applicable condition of Beste's approximate constraint equation is also indicated. The idea of orthogonal circular orbit satellite constellation, which is a combination of polar orbit constellation and equator orbit constellation, is proposed and the constellation parameter constraint equation is derived. Some orthogonal circular orbit constellation schemes are presented. By making a coverage performance comparison of orthogonal circular orbit constellation schemes with corresponding polar constellation schemes, the validity of orthogonal circular orbit satellite constellation is verified.Chapter 4 focuses on the design of regional coverage satellite system with common-track constellation. The characteristics of common-track constellation are studied thoroughly. A coded notation which can describe common-track constellation entirely is proposed and the restricted equivalent relationship to the Walker'sδconstellation is given. An optimization design method for implementing regional coverage satellite system with common-track constellation and and detail design steps are presented, and some optimal constellation schemes for China are obtained. Moreover, the parameters of these optimal constellations were adjusted again according to the time-varying traffic distribution density, which improved the consistency between the coverage performance of constellations and the traffic distribution density and hence improve the overall system coverage performance. Finally, the optimization design method for regional coverage common-track satellite constellation based on Genetic Algorithm Toolkit (GATOOL) of MATLAB is studied. Simulation results show that the parameter precision of these optimal constellations is improved while the computation time is reduced greatly. These results verify the efficiency of the GA in the task of satellite constellation design.The satellite constellation classes, which are suitable for MEO-TDRSS, are investigated in chapter 5. The limitations of GEO-TDRSS are analyzed systematically. The idea of MEO-TDRSS is proposed, the generic network architecture and traffic distribution characteristic of MEO relay satellite system are presented. These studies show that, to compare the performance of MEO-TDRSS entirely, the coverage performance for low-altitude celestial and for ground and inter-satellite link (ISL) implementation complexity are required to be analyzed. Take China as example, the coverage performance and intersatellite links properties of four constellation schemes with different constellation types are compared by simulations. Then, the appropriate satellite constellation types for the implementation of MEO-TDRSS are advised.Chapter 6 studies the ILISL establishment strategies for two-tier LEO/MEO satellite networks. Based on the in-depth investigation of these existing strategies, the inherent disadvantage of these existing strategies which decreases the topological stability of the two-tier satellite network is indicated. Then, three new ILISL establishment strategies based on the idea of convergent reconstruction are proposed to improve the topological stability of the two-tier satellite network by minimizing the number of topology reconfigurations. Numerical results show that these proposed strategies can substantially reduce the number of the network topology reconfigurations and hence improve the topological stability of the two-tier LEO/MEO satellite networks with acceptable cost of increased number of ILISL reconstructions and mean ILISL distance.Chapter 7 is the summarization of this dissertation, and indicates the contributions of our studies.