Research On Capacity Analysis And Access Control Strategy Of Non-geostationary Orbit Satellite Communication System

Radio Resource Management(RRM)is an important issue of satellite communication system.Aiming at improving resource use efficiency,communication quality and system capacity,RRM includes channel allocation,access and handover control,capacity analysis under fading channel,power control etc.In this thesis,we emphasize on capacity of satellite communication system and access control strategy under large scale satellite constellation communication system.System capacity falls into two parts,capacity of satellite multi-beam under fading channel and capacity of satellite networks.Firstly,in CDMA satellite system,multiple access interference is analyzed in detail based on satellite muti-beam model.Relation between the ratio of signal to interference and capacity of per beam is simulated under perfect power control.Then the effect of shadow fading and multi-path fading on the power of signal is theoretically analyzed and mathematically deduced under imperfect power control.Independent of coding and modulation method,this thesis focuses on the capacity calculation method of satellite under Lutz channel model,which makes the model more applicable.By comparison,the difference between real capacity and theoretical capacity of satellite is obtained,which offers reference to satellite beam design and power allocation.Secondly,aiming to calculate the system capacity of a given satellite constellation,this thesis proposes a time-varying traffic model based on varying traffic with varying time zone and focuses on a MEO(Medium Earth Orbit)satellite constellation with global coverage.Using a shortest path routing algorithm and load balanced routing algorithm,we analyze the system capacity and distribution of traffic on each Inter-satellite Link(ISL)in different time slices and investigates the effect of ISL capacity on the system capacity.The time-varying traffic model makes analysis more reliable.The difference of system capacity and load on ISL under two models is pointed out via comparison with equal traffic model.Application of time slices reduces complexity of calculation.Finally,the necessity of research on satellite access control strategy in multi-satellite covered area is pointed out according to the analysis of coverage characteristics of large scale satellite constellation communication system.Based on OneWeb satellite constellation,this thesis simulates satellite access strategies of the shortest distance(same as largest elevation),maximum coverage time and maximum available channel.The simulation results in a better choice on strategy of maximum available channel in terms of performance indices of average access waiting time,handover failure rate and channel utilization,which indicates channel resource is the key fact for satellite access control strategy.According to channel fading principle,probability based regional shadow fading model is proposed.For better communication quality under fading channel,elevation based satellite access control strategy is proposed under comprehensive consideration of distance and coverage time.In view of the importance of channel resource under large scale satellite constellation communication system,channel and load based satellite access control strategy is proposed.With the probability based regional shadow fading model,this thesis simulates satellite access control strategies of the shortest distance(same as largest elevation),maximum coverage time and maximum available channel,elevation based satellite access control strategy and channel and load based satellite access control strategy.The simulation result verifies the efficiency of elevation based satellite access control strategy and channel and load based satellite access control strategy.