Study On The Technology Of Mobile Location Management For LEO-Satellite Non-Terrestrial Networks

Low Earth Orbit(LEO)satellite communication system has emerged as a crucial component of global mobile communication systems for its short path length in hops,low transmission loss,worldwide coverable,and high robustness.Among many others,location management of mobile users plays an important role in the maintenance of network performance and quality of service.However,the relative high movement of satellites leads to fast switching between adjacent satellites or satellite beams,which brings great challenges into mobile location management.Additionally,for a mega number of users accessing and handing-over,the increase of signalling overhead and database load becomes a hot topic in the satellite technology for tracking and locating.This thesis focuses on the location management for LEO satellite communication systems to solve the overloaded issues of feeder link.Firstly,for frequent location update caused by the rapid movement of satellites,a location area division strategy based on the prediction of sub-satellite point trajectory is proposed.Considering various mobility patterns of users,location areas are combined to form a beam tracking area list(BTAL),which is the basic unit for location management of LEO satellite communication systems.Taking full advantage of the onboard processing ability of satellites,a three-level database model is employed to store location information in a distributed manner,and distinct processes of location update and paging are designed.Secondly,to balance the channel resource load and signalling overhead in LEO satellite communication systems,a mapping matrix is used to allocate BTALs dynamically.Four optimization problems are constructed using the minimisation of location update signalling overhead,the minimisation of paging signalling overhead,the minimisation of the weighted total overhead,and the trade-off overhead based on Nash bargaining solution as objective functions respectively.Finally,the optimization problems are modelled and solved using Matlab and a CVX toolbox.The results show that the dynamic BTAL management strategy based on Nash bargaining solution can not only achieve a trade-off point between the signalling overheads of location update and paging,but also be more adaptable for users with various mobility patterns.