The Leo System Call Processing Beam Positioning Algorithm

Satellite communication is an essential branch of modern spatial techniques. It can realize the radio communication between the mobile terminals by using the satellite repeater which acts as relay. Among the satellite mobile communication systems, the LEO-MSS's (Low Earth Orbit Mobile Satellite Systems) possess the wide development space due to their global seamless coverage, much shorter transmission delays, less power requirement for the user terminals and strong ability in anti-ruin.The modern US military satellite communication system could be classified into three categories: the wideband system, the protected system and the narrowband system. The wideband system focuses on the traffic capacity; the protected system puts emphasis on jamming immunity, the ability of concealment and destruction resisting capacity against nuclear weapons; while the narrow band system is designed to support those subscribers in a mobile or adverse condition, who need voice or low speed communication. Iridium System and Globalstar play an essential role in military communication, which belongs to the narrow system and supports voice services, data services, etc.On the basis of the narrow system, the improved call processing spot beam determination algorithm using spherical triangles is introduced along with several formulae being deducted. Also an optimized updating radius is suggested based on experiments to balance the overhead of Location Updating (LU) and Location Paging (LP). The results are shorter single paging time, more efficient paging and hand-off process.In chapter 2, the LEO system call processing spot beam determination ST algorithm is proposed with the combination of terrestrial mobile communication research and the features of satellite communication. In addition, STK simulations demonstrate the effectiveness of the algorithm.In chapter 3, the analysis of the two factors affecting the ST algorithm is made. And a user mobile model is introduced, which adopts dynamic distance-based updating method. Its movement distance obeys index distribution, whereas its movement direction obeys uniform distribution.In chapter 4, hand-off schemes for LEO satellite communication systems are studied. With the help of the ST algorithm, the hand-off schemes can further reduce the signaling overhead.The dissertation is summarized in the last chapter. Finally, the future research work is pointed out.