Fast Terminal Switching Strategy Of Low-orbit Satellite Communication Systems And Simulation Technology

As an important way of communication, satellite communication is playing an important role in today's communication world. LEO satellite communication system is the direction of future satellite communication because of the short propagation delay and the low power consumption. At present, most terminals in satellite communication systems are slow-moving terminals of which the velocity is below several kilometers per hour, for example, portable-phones, mobile-phones, etc. But with the development of technology, the tendency of globalization and some special service needs long distance space communication. Then fast-moving terminals are needed. For example, the aircrafts between continents, spacecraft, military aircrafts, missiles. The LEO satellite networks, which can cover wide areas, are used to best satisfy the fast-moving terminals. In order to communicate with these fast-moving terminals, manipulate their states and send control command to them in time, maximum communication time, minimum non-communication time and minimum delay are considered. The delay contains both the delay of transmitting state information from the terminal to the console and the delay of transmitting control information from the console to the terminal. The terminals move fast between covering areas and handover from one area to another. When a terminal is covered by more than one satellite, choosing a reasonable satellite to access is directly related to the above performance.Chapter 1 is the preface, which concisely introduces the development, status and perspective of the satellite communication, and the arrangement of this dissertation.In Chapter 2, a LEO communication system supporting fast-moving terminals is studied. Based on this system, two handover algorithms are proposed: the maximum covered-time algorithm and the shortest-path-first algorithm in the case of GLOBALSTAR and Iridium. In order to find out their different effects on the system capability in different environment, the two handover algorithms are calculated and compared through simulation and analysis.In satellite communication systems, some special users which are usually fast-moving terminals may need to be supported as well as the common users sometimes. Since the two types of users exist, the communication performances for both of them should be considered. In Chapter 3, a novel channel reservation algorithm is proposed for this case. The theoretic analysis and simulation results show that the handover performances of the special users are improved by this algorithm.In Chapter 4, the modeling method of multiple-beam antenna in satellite communication is proposed and the impacts on the handover performances of the multiple-beam antennas with different pattern are compared. Simultaneity, The modeling method of multiple-beam antenna and wireless pipeline in OPNET are presented.The dissertation is summarized in the last chapter.