Optimal management in GEO and LEO satellite communication systems

Abstract

In this thesis, we consider three problems concerning the efficient use of satellite communication networks. Geostationary orbit is considered as a kind of natural resource which must be shared with all nations. However, due to the rapid increase of the number of geostationary satellites, intersatellite interference problems limits the number of networks that may be accommodated along the geostationary orbit at a given level of technology. Therefore, the use of techniques to optimize satellite orbital positions has become necessary. In this study, the methods of optimization are presented. In applying optimization methods, we use an objective function which is related to the aggregate interference affecting each satellite networks. Fibonacci method and Simulated Annealing are applied. Simulation results indicate that our methods works well. Radio frequency spectrum is an another important natural resource. The use of this natural resource is optimized by employing multibeam antennas and SS/TDMA techniques. To provide global communications efficiently, SS/TDMA satellites are interconnected by ISLs, creating a satellite cluster. In this study, we present a heuristic algorithm, which is a very efficient and general one, for the traffic scheduling. The current satellite communication systems are almost all based on geostationary satellites. The major advantage of these systems is their unchanging position with respect to the earth surface, thus no control overhead is required to track the satellites. However, there are several drawbacks or implementation difficulties : the high cost of launching the satellites into the geostationary orbit, long intersatellite link distance, high on board power requirement and large propagation delays. LEO satellites can overcome these disadvantages. With this advantages of LEO satellites, personal communications via LEO satellites constellation (GMPCS : Global Mobile Personal Communications by Satellite) is welcomed. Satellite is...