Location Management Technology For The Low-orbit Satellite Communication Systems

The satellite mobile communication 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. Moreover, they will be very important in the future Personal Communication Systems (PCS).LEO satellite communication system is an important part of the future global personal communication infrastructures. An important aspect of the LEO satellite system is to manage the location of both users and satellites. Many system signal flows such as database updates and queries are required to accomplish such a task. There are two basic operations that are elemental to track mobile users: update and paging. Associated with each one of these operations there is a certain cost. For instance, frequent updates cause high power consumption at the mobile units and heavy load in the network, increasing one cost leads to a decrease in the other one. Finding a trade-off between the two problems is important. In this dissertaion, schemes on location management for LEO satellite network are proposed.In chapter 2, schemes on location area design for LEO satellite communication systems are studied.Traditional fixed location area is optimized, and the optimum value for location area is computed through simulations. A dynamic location area design scheme based on user's mobility is proposed, and it is useful for systems with all kinds of users.In chapter 3, schemes on location update for LEO satellite communication systems are studied. A timer and movement based location update strategy is proposed. Location update frequency is decreased without increasing the paging cost; as a result, the total cost of location management is decreased.In chapter 4, schemes on location paging for LEO satellite communication systems are studied. Since the paging costs are associated with bandwidth utilization and the delay bounds influence call setup time, the paging costs and delay bounds are considered. Based on satellite mobility model, a new paging scheme under delay bounds is proposed. Simulations are done to compare the new scheme with some other paging schemes on paging delay and paging costs.In chapter 5, schemes on database management for LEO satellite communication systems are studied.An Onboard VLR Database Management method is proposed for LEO Satellite Systems and simulation results show that it can reduce the cost of location management greatly with little influence on call set up delay.The dissertation is summarized in the last chapter. Finally, the future research work is pointed out.