Research On Key Techniques Of Broadband Satellite Networks

Satellite communication systems have long been one of the hallmarks of advanced nmunications technology, with their remarkable and distinctive ability to link most of the ulated areas of the Earth. The latter half of the 1990s has seen a resurgence of interest in adband satellite data networks. Thanks to both the rapid deployment of the Internet and ances in satellite technology, the market for broadband satellite services is poised for stantial growth in the coming decade.Broadband satellite networks are also named next generation satellite networks. Current nmunications satellite systems (bent-pipe type) have generally been designed to provide er voice or data transaction (low data rate) services through small terminals, or trunking gh data rate, or broadband) services through large terminals. However, technological ances are enabling next generation satellite systems that combine broadband data rates h small terminals, thereby providing more affordable "last-mile" network access to home 1 small business users worldwide. In particular, two types of broadband satellite systems under development: high-power high-capacity satellites deployed at traditional stationary (GEO) orbits, and large constellations of satellites deployed at much lower O) orbits.In this dissertation, we research four key techniques of broadband satellite networks, and ordingly obtain some practical results. We hope that these researches of the dissertation provide some useful outcomes for reference to our future national broadband satellite works.This dissertation has four contributions as follows:In network layer, we first present a novel network topology named SpiderWeb pological Network (SWTN). Then we propose a connectionless-oriented packet routing orithm for polar orbit LEO satellite constellation network based on the SWTN. The routing orithm minimizes the propagation delay between source and destination. The algorithm is tributed, i.e., the choice of the next hop in routing is based upon the packet in each LEO ellite at the current moment (time slice). The algorithm incurs no overhead since satellites not exchange any topology information. When packets encounter congestions or link ures, the algorithm resorts to a suboptimal path. Instead of basing on on-board routing le, the algorithm is based on on-board calculation. The next hop routing is obtained using y one subtraction of bits, and satellites need not save any on-board routing tables. This ting algorithm is more practical and simple, which holds for both the small constellationand the big constellations with either simple or complicated structure of ISLs, either phasing=0° or phasing≠0°.In transport layer, we firstly discuss the performance analysis of TCP for broadband satellite networks. Then we present two unsolved problems of current TCP: the unfair allocation problem of the network bandwidth resource because of different round-trip times (RTT) and strongly bursty traffic in a large bandwidth-delay product network. We propos an improved scheme: TCP-DiffServ. TCP-DiffServ is capable of active differentiated service, and TCP packets are sent in not burst but regular over an entire round-trip time. Simulation results show that TCP-DiffServ effectively enhances the overall efficiency and robustness of the networks.In network resource scheduling, we propose a novel scheduling strategy for broadband multimedia satellite networks. It is composed of the ground local scheduler and On-board global scheduler. Because most of the complexity that is added to the satellite network is confined to the ground segment, the scheduling strategy minimally affects the design of the On-board Processing (OBP). Simulation shows that it is a highly efficient scheduling strategy which not only reduces the end-to-end delays endured by the best effort connections but also minimizes the degradation of VBR and ABR connections with increased frame utilization performance.Based patents, we bring forward a new system of high capacity and broadband VSAT communication satellite network. A kind of on-board rela...