Access And Handover Technologies For High Dynamic And Multi-user Terminals Scenes In Satellite Communication Systems

Because of the ability to achieve global coverage,unaffected by topographical terrain and severe natural disasters on the earth,wide available frequency bandwidth,fast network construction,low cost and so on,satellite communication systems play an important role,and obtain more and more attention.Therefore,researches on satellite communication systems are very important.Among those researches,access and handover technology is an important part.This dissertation studies the access and handover techniques in satellite communication systems for high dynamic and multi-user scenarios.This dissertation first studies the access and handover technology of satellite communication systems.For high dynamic and multi-user scenarios,the system model(including coverage model,mobile model and service model)is obtained.Then,based on the system model information,and considering the high dynamic and multi-user scenarios,we prioritize the users with different grades and propose a channel reservation strategy based on multiple priorities.The strategy determines the channel reservation threshold according to the ratio of different priority traffic to ensure that the service performance of the higher priority users is better than that of the lower priority users.Then,under the premise of multi-priority channel reservation strategy,the occupation and queuing rules are proposed.Users of different priorities can occupy or queue the channels to access according to the rules to improve access and handover performance.In addition,due to the limited capacity of the LEO satellite communication system,the channel allocation strategy of the LEO/GEO hybrid satellite communication system is considered.Finally,the proposed strategies are simulated.The simulation results show that the proposed strategies have different effects on different performance indicators with different priorities.In general,the high dynamic multi-user channel allocation strategy of the LEO/GEO hybrid satellite communication system performs better,and the performance indicators obtained by users with higher priority are better than those with lower priority.For the high-dynamic user scenario,by predicting whether the call is to handoff or not,a channel reservation strategy based on grey prediction is proposed.For those calls that have already accessed the system,we process the received signal power that change over the time.Using the classical GM(1,1)grey model,the received signal power at a future time can be predicted to obtain a prediction result of whether the call is to be switched.According to the prediction result of different calls,the number of calls that may need to be switched is counted.Then based on the number,we can dynamically reserve the channels.From the simulation results,the strategy has achieved overall performance improvement.There are various kinds of interferences that cannot be ignored in the actual communication systems.Considering the avoidance of the interfered channel,a spectrum map based access and handover technique is proposed,and the information related to spectrum map is used to allocate channels to the calls.Analyzing the spectrum map,according to the requirements of access and handover,the auxiliary information is extracted from the information of the spectrum map.With the auxiliary information,the access and handover processes are executed to complete the access and handover.This strategy can effectively avoid interference,so as to avoid the occurrence of a situation in which an already-accessed call is sent by the channel that has excessive interference.