Research On Channel Assignment Strategy In LEO Satellite Mobile Communication System

Currently,the terrestrial wireless communication system has maturely developed,whose coverage rate is large in densely populated areas.While in distant seas,remote mountains or other sparsely populated areas,due to the lack of ground infrastructure,the customers cannot be served.However,the satellite mobile communication system can achieve full coverage of the earth's surface through a constellation constituted by a certain number of satellites.LEO satellite,characterized by its low propagation delay,low transmission power and suitability for small handheld terminal,is an important direction of the research of the satellite mobile communication.On-board resources are precious and limited,so it is needed to develop a reasonable channel assignment strategy,optimize the utilization of the channel resources and make different classes of users get appropriate service.We first study various schemes of channel reservation,and propose an updated version of fixed channel reservation(UFCR).This scheme in advance divides the channels in designated regions into two classes,reserved channels and common channels.By optimizing the order and class of the channels the handover calls access,the effects on the new calls are reduced as much as possible.The simulation shows that the UFCR scheme improves the performance of new call access,which is in accordance with the requirements of fairness,and improves the grade of service and channel utilization.Secondly,due to the fact that there are many kinds of business in actual communication system,this thesis studies the effect of multi-service on channel reservation strategy and proposes a priority-based multi-class traffic channel reservation scheme(PMCR).This scheme adopts multi-level channel access thresholds for new calls and handover calls of different priorities,thus enables high priority traffic to use more channels.The simulation shows that the introduction of priorities in the PMCR scheme effectively guarantees the new call performance and handover performance of high priority service.In this thesis,these proposed two schemes are firstly theoritically analyzed,and then various performance metrics are verified through the simulation,respectively.The result shows that the proposed schemes are both correct and feasible.Both of them have a certain value for the research of low earth orbit satellite mobile communication system.