Research On Mobility Management And Design Of Simulation Platform For LEO Satellite Communication

The low Earth orbit(LEO)satellite communication system has attracted more and more attention because of its small size,low cost,mass production,and low transmission delay.At present,the mobility management technologies of LEO satellite communication systems mostly stay in the theoretical stage,which cannot meet the actual operational requirements,and it also lacks a simulation platform with complete system.Therefore,in this thesis,the author conducted in-depth researchs and implements of the mobility management and simulation platform in LEO satellite communication.The main research work is as follows:Aiming at the current lack of LEO satellite mobility management simulation platform,a LEO satellite communication simulation platform is designed and implemented based on OPNET.First,by analyzing the functional requirements of the simulation platform,this thesis proposes the overall architecture of the simulation platform,including functional entity modules,satellite attribute modules,network management modules,satellite operation modules and analysis modules.Then,the node functions of User Equipment(UE),LEO satellites,Mobile Switch Center(MSC),and Network Control Center(NCC),with modeling the node model and process model are designed.Then,the author researches the multi-beam antenna model of the satellite and implements the model,and simulates the antennal model by deploying mobile ground nodes to receive satellite signals.The results verify that the coverage and gain of the satellite multi-beam antenna can meet the design requirements.Finally,a system scenario is built to test various functions of the simulation platform.The results show that the satellite simulation platform can simulate the mobility management process of the LEO communication mobility management system,and can output various indicators such as handover success rate,handover times,throughput and so on.Aiming at the handover management of the LEO satellite communication system,two satellite handover schemes are proposed in this thesis.First,this thesis analysis the handover phase of LEO satellite communication system,including handover measurement,handover decision,handover preparation and handover execution.Then,a hard handover scheme based on signal strength measurement is proposed and designed,including three parts: cross-beam user handover in a single satellite,cross-satellite user handover,and user reset when handover fails.Then,this thesis analyzes the unique reverse seams problem of LEO satellites.Aiming at the long handover time and low success rate between satellite reverse seams,a handover scheme between satellite reverse seams is proposed by replace part of the NCC's function in UE node to reduce inter-satellite links.Finally,this thesis simulates and compares the two handover schemes through the built LEO satellite communication simulation platform.The simulation results show that the reverse seams handover scheme has lower handover time and higher success rate.