Özet:
Satellite networks are an attractive option to provide broadband telecommunication services to globally scattered users, due to their extensive geographic coverage, high bandwidth availability, inherent broadcast capabilities, etc. Satellites rotating in geostationary orbit (GEO) are very well suited for broadcast services, but they suffer from high free space attenuation and long delays. On the contrary non-geostationary (NGEO) systems consisting of Medium Earth Orbit (MEO) and Low Earth Orbit (LEO) satellites offer smaller latency, lower free space loss, and better re-use of available ground-space communication frequencies, hence they are more suitable for most applications (especially for those running in real-time). However, these advantages come with a price: Footprints of satellites at lower altitudes are smaller, and global coverage can be provided by higher number of satellites that are connected each other with inter-satellite links (ISL). Moreover, lower orbit satellites move with higher speeds relative to the Earth’s surface, resulting in high dynamic in the network topology. Dynamics of the satellite constellation constitute major challenge in providing efficient routing and quality of service (QoS) for rapidly-growing real-time multimedia services. On the other hand, regular NGEO satellite networks has some facilitating features like periodicity, predictability and having highly symmetric and regular topology. For efficient networking in NGEO satellite networks, all these features should be considered. In this thesis, we clarify features of satellite systems that differ them from their terrestrial counterparts and propose novel routing and network mobility management techniques in NGEO satellite networks. Firstly, we make use of geometrical properties of the network topology, and propose a priority-based adaptive routing (PAR) algorithm. Next, we focus on handling the mobility of network by utilizing satellites with Earth-fixed footprints, and extend a well-known mobility handling technique called Virtual Node (VN). We propose Multi-state Virtual Network (MSVN) topology that alleviates deficiencies of VN concept. We clarify potential advantages of MSVN by developing efficient handover mechanisms and beam management techniques in MSVN-based satellite systems. Finally, we investigate efficient integration of NGEO satellites with High Altitude Platforms (HAPs) via highcapacity free-space optical links for carrying dense and real-time multimedia traffic. Considering the mobility and resource limitations of satellites, we propose an efficient solution for the optimal link establishment problem between HAPs and satellites.
