| Satellite communication has attracted great interest as a significant modern communication method. Early efforts on satellite communication system are most about Geostationary Earth Orbit(GEO) satellite. Compared with GEO satellite, Low Earth Orbit(LEO) satellite has numerous advantages, such as the capacity of providing global coverage and short delay. However, the routing algorithms for geoclimatic network can not be applied to satellite system directly because the topology changes quickly in the satellite system. Therefore, specialized and effective routing strategies have become one of the critical issues for the LEO satellite communication system with Inter_Satellite Link(ISL). Moreover, huge funds and long period are needed for the construction of satellite system, and it is difficult to change the structure after construction. Therefore, precise simulation is necessary before the implementation of LEO satellite system. This thesis will focus on the routing algorithm for satellite network.Chapter one is the preface. Firstly, the development of satellite communication system is introduced. Different routing strategies in LEO satellite system and multi-layer system are studied in this chapter. Meanwhile, this section illustrates switching techniques in brief. The framework of this thesis is shown at the end of this chapter.In chapter two, a LEO satellite system simulation model based on OPNET is built in order to estimate the performance of the routing protocol. STK is used to build the satellite constellation model first. After analyzing the characteristics of satellite system, we build a simulation environment by OPNET and introduce the function of each module in this chapter. Switching scheme and scheduling algorithm are also studied in this chapter. To verify the reliability of the platform, a few experiments have been conducted at the end of this chapter.A distributed logical location-based routing algorithm for LEO satellite network with ISL is studied in chapter three. Firstly, features of LEO satellite network architecture and theorem of DRA algorithm are introduced. Routing in the constellation network with phasing factor is given in this chapter. Subsequently, the model in OPNET is built and the performance of the algorithm is evaluated through simulation. Lastly, two typical routing algorithms are compared through simulation and analysis. The influence of different ISL data transfer rate and users with high data transfer rate is also analyzed.In chapter four, a survivable routing algorithm based on MEO&LEO double-layered satellite network is proposed. Satellite constellation design is discussed at the first part, including how to choose the height and type of satellite orbit. Inter-satellite link in double_layered satellite network is also studied in this chapter. The routing algorithm for MEO&LEO double-layered is proposed to solve the problems caused by network congestions and failed satellites. Some simulation results have gained through OPNET. The performace of single_layered and double_layered satellite networks are evaluated through simulation. The influence of orbital positon and inclination is also analyzed.Chapter 5 is the summarization of this thesis. |
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