Research On Location Management Strategy In LEO Satellite Communication System

Low Earth Orbit(LEO)satellite communication system has become a research hotspot in the current mobile communication field due to its many advantages,such as low transmission delay,global coverage,low link loss,and good survivability.As a key technology in the field of mobile communication,location management technology has a profound impact on the performance of the system.With the increase in the number of mobile terminals and the diversification of business requirements,the impact of location management strategies on system load and location management database access load becomes more and more significant.How to effectively realize the location management of the system,reduce the total overhead of location management,and balance the overhead of location update and paging is the most important research topic in location management.This thesis mainly studies the location management strategies in the LEO satellite communication system.The main research work is as follows:1.Aiming at the problems of the huge construction cost of LEO satellite communication system,difficulty in changing after completion,and difficulty in evaluating location management strategies,an OPNET-based LEO satellite communication system location management simulation platform was built.First,design the LEO constellation model,build the overall network topology;then model each node and process model,select the appropriate module,state machine,communication link,etc.according to the function of the node,and design the execution process and code;finally,complete The key design in the location management simulation platform was developed,and the multi-beam antenna model,terminal mobile model,and call model were modeled.2.Aiming at the problem of high location management overhead in the current LEO satellite communication system,a location management strategy based on the dynamic location area of the terminal is proposed.First,a dynamic circular location area is designed.The location area is centered on the terminal's own location and the location update radius is used as the radius.When the mobile terminal leaves the location area or triggers a mandatory location update time,the terminal initiates a location update;,Derive the distance and azimuth angle between the terminal and the satellite through the terminal location information and satellite ephemeris information,combine the system multi-beam model to determine the paging satellite and spot beam;finally,evaluate different location updates for terminals with different mobile characteristics The impact of radius on location management overhead.The simulation results show that designing an appropriate update radius for the terminal can effectively reduce the location management overhead.3.Aiming at the problem of high paging overhead of multi-satellite selection strategy in LEO satellite communication system,a location management strategy based on terminal neighbor list is proposed.First,the multi-satellite selection strategy is adopted to allocate a suitable resident satellite for the terminal;then,this thesis designs a neighboring cell list based on the terminal elevation angle by predicting the change trend of the elevation angle between the terminal and the satellite over time,and combines it Used for location management;finally,the strategy is simulated.The simulation results show that compared with the multi-satellite selection strategy,this strategy can reduce the paging overhead and the total location management overhead.