Location Management And User Access Leo Satellite Communications Technology Research

In the process of constructing global seamless communication system, LEO (Low Earth Orbit) satellite communication system will play an important role in the future, it is also the important part of future Personal Communication System (PCS), LEO satellite communication system has became a hotspot of the research in recent years.In LEO satellite communication system, due to the high speed satellite and the mobility of users, in order to found Mobile terminal(MT)and paging MT, LEO satellite networks must have positional information recorded, which has the function of location management. Location management technology includes location update and location paging, the way of performing location update of MT influences the costs of paging, so the effective location update strategy is crucial to the performance of the network. Moreover the number of satellite of LEO satellite communication system is far more than Geostationary Earth Orbit (GEO) satellite communication system, so the situation of multiple satellite-coverage exists in LEO satellite communication system, the MT must choose the access satellite when a call or handoff in the process of a call occurs, the algorithm of how to choose access satellite is essential to the quality of the LEO satellite communication. Therefore, this dissertation mainly studies location update technology of location management and subscriber access technology.In respect of location update technology, a location update strategy based time-distance for satellite communication system is proposed. In the proposed update strategy, the location update radius is dynamic adjusted according to the speed of users and the busy degree of traffic, especially when the mobile user is the main users and the burst traffic situation, the proposed location update strategy can effectively decrease the cost of location management, and improve the performance of LEO satellite communication network.In respect of subscriber access technology, a new scheme is proposed, the proposed scheme besides considering elevation and overlaid time, also considering satellite load balance. And the simulation results indicate that heavy-traffic area of our country is sensitive to elevation angle, we can reduce the rate of call-block and handoff-block by adjusting weight coefficient of satellite load, elevation angle and overlaid time according to different traffic-areas, the proposed algorithm has the meaning of practical application.In conclusion, modeling on LEO satellite communication system and the performance analysis are made, the simulation results indicates the proposed location update strategy based time-distance and subscriber access algorithm are effective for LEO satellite communication.