Research On Access Control Strategy In GEO/LEO Satellite Mobile Communication System

Satellite mobile communication can realize the communication between mobile users who are on the ground, in the air or on the sea and the communication between mobile users and fixed users. It is the combination of mobile communication technology and satellite communication technology. Despite the rapid development of terrestrial mobile communications technologies, terrestrial mobile communications system is limited due to the natural environment, economic costs and technology, so it is difficult to achieve global coverage communication. As an important part of global mobile communication, satellite mobile communication can provide excellent communication services for emergency rescue, ocean users and global coverage communication which have broad prospects of development.Since Low Earth Orbit (LEO) satellites revolve around the earth at high speed compared to the movement of mobile users, users will handover between the beams of satellites, so in order to reduce the users’ call dropping probability and new call blocking probability and guarantee the quality of service, satellite communication system must adopt channel allocation strategy which should be more reasonable compared with the ground mobile communication system. With the development of satellite communication technology, multi-satellites network is a trend of satellite communication system. Users will be covered by different orbit satellites in multi-satellites network, so users could choose to access different satellite network. For LEO satellite mobile communication system, a new channel allocation strategy is proposed for multimedia communication. Based on this discussion, users’access control strategy is researched on Geostationary Earth Orbit (GEO) and Low Earth Orbit multi-satellites network. The main work is as follows:Channel status-based reservation strategy is proposed for multi service LEO satellite mobile communication system. In the stage of hangover management, the system will check the resource utilization of next cell and set different channel reservation time for users, so resource utilization is improved and users’handover can be guaranteed. In the stage of reservation request, if there is no idle channel resource, reservation request will be added to the queue until channel resource is available. Considering the characteristics of different services, channel resource of some services can be occupied by other services so as to ensure the system performance. Simulation results show that channel status-based reservation strategy improves the grade of service and is suitable as a channel allocation strategy for multi service LEO satellite mobile communication system.Direct access strategy and protected access strategy are proposed for GEO/LEO multi-satellites network. In the direct access strategy, users will access to the LEO satellite first. If there is no channel resource available in LEO satellite, some of the users can access to the GEO satellite. In the protected access strategy, a user should check the resource utilization of GEO and LEO satellite cell before handover to new cell. Then system determines which satellite the user will access to. Simulation results show that protected access strategy can make full use of GEO satellite channel resource. When the traffic is low, protected access strategy provides low call blocking probability while guaranteeing high resource utilization.