| With the rapid development of terrestrial wireless communication technologies,Internet of Things(Io T)has been widely applied in numerous areas.However,to realize the ultimate vision of Io T,i.e.‘All things in the world can be connected with each other.’,merely depending on terrestrial network is far from enough.Comparing to terrestrial ones,space-based satellite network has the feature of high and wide coverage so that it apparently has the advantages of providing Io T services in remote areas like ocean,aerial area,and other areas that cannot be coverd by terrestrial network.Hence,as the supplement and extension of terrestrial network,satellite network can offer powerful supports to realize the global seamless coverage of Io T.However,since exsited satellite systems are commonly designed for specific purposes,they have disadvantages such as lack of generality and extendibility.Besides,traditionally,satellite and terrestrial systems are developed and operated separately.All those matters above reveals that existed satellite networks cannot meet future Io T’s requirement of network flexibility.Therefore,it is an urge to start the researches in the field of space-terrestrial Io T network.Those researches can provide theoretical guidance and technical support for future space-terrestrial fusion development of Io T.This dissertation mainly addresses the global developing trends and application services requirements of Io T.Basing on the synthetic considerations of the features of space-terrestiral integrated Io T network such as structure complexity,application variety,massive access and resource limitation,researches of system architecuture,traffic model,multiple access,interference analysis and spectrum sharing have been conducted.Those researches aim on provide theoretical basement for future development of Chinese satellite Io T system.The main research contents of this dissertation are summarized as follows:(1)Traditionally,satellite and terrestrial communication system are developed and operated separately,which cannot meet the requirement of future Io T.Aiming at this problem,in this dissertation,a space-terrestrial integrated architecture for low earth orbit(LEO)satellite Io T has been proposed,which bases on the researches of space-terrestiral network integration,the advanced technologies used in 5th generation(5G),and the potential application requirements of satellite Io T.Meanwhile,considering of system resource cost and possible application scenarios,a high efficient and reliable communication procedure aiming at light control has been also proposed basing on the architecture.Last but not least,utilizing the space-terrestrial integrated design,we proposed a space-terrestrial cooperative networking mechanism with researches on space-terrestrial united access control structure and cluster-based cooperative transmission scheme.Via the aforementioned design,the architecture can provide good infrastructure for rational allocation and flexible distribution of system resources.(2)The future trend of LEO satellite Io T should be globalization and multi-domain application.Under this trend,the huge dynamic feature of LEO satellite constellation and inhomogeneous distribution of Io T traffic may cause negative effects on system performance.According to the potential application domains and traffic types,aiming at this problem,the dissertation proposed a stochastic variable parameter analysis-based global Io T traffic model.Basing on this model and combining with the satellite motion rule,we analyzed the traffic load of different nodes at different moments.By analyzing all nodes in the system,the influence that satellite Io T application distribution caused on system performance has been revealed,which can provide theoretical support for designing more rational system resource allocation scheme.(3)Under the global coverage and massive access scenario,user data collision will be an unavoidable problem that a single node in LEO satellite Io T system will face.Aiming at this problem and basing on the researches of random access(RA)technologies,the dissertation has proposed a collision-torlerated and quasi synchronous RA scheme,which considers the dynamic and power unbalance feature of LEO satellite.This scheme utilizes navigation information to realize quasi synchronous access and simplified receiver design.Meanwhile,using ring-separated power control scheme can raise system capture efficiency,which is theoretically analyzed in this dissertation.Finally,simulation results show that power control can efficiently raise the caputure performance and the proposed scheme has a significant improvement in system performance comparing to similar schemes under LEO Io T access scenario.(4)Under the circumstance of frequency shortage,as an important part of space information network(SIN),LEO satellite Io T system will cause and suffer from mutual inter-network and intra-network co-frequency interference,which will strongly influence whole network efficiency.Aiming at this problem,basing on the proposed architecture,the feasibility of network nodes is analyzed from dimensions of time,space,frequency and power.Combined with the motion law of satellites,an analysis model for jointly scheduling orbit and frequency is presented.Based on the analysis model,the co-frequency interference scenarios within satellite systems and between satellite and terrestrial systems are analyzed.Via deeply analyzing the potential interference scenarios,the interference levels that LEO Io T system suffered from satellite nodes and terrestrial systems have been revealed.After that,for one specific satellite-terrestrial frequency sharing scenario,a spectrum-sharing mechanism basing on optimized power control has been proposed,which can support future system frequency band allocation and spectrum sharing. |
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