Multi-hiberarchy Based Availbility Analysis Method For Global Navigation Satellite System

Global Navigation Stellite System(GNSS) as a major temporal and spatial infrastructure of human society, like the navigation function of the human brain, affects all aspects of human activities. With the requirements of precision, time and the use of various environmental for navigation applications is more and more high, high availability has become one of the most important indicators of the design and construction for GNSS. At the same time, four GNSS in the world will be gradually built, availability analysis has become the major method for avoid the risk in compatible positioning of them. It will bring two benefits to study the whole availability analysis for GNSS: 1)this work will evaluate existing GNSS’s capabilities to meet the demand, and promote its improvement and optimization, and 2) this work will support the design of the GNSS and its branch system.The dissertation focuses on addressing how to analysis the whole availability for GNSS base on the reliability of the components of GNSS. A concept system of the whole availability for GNSS is systematic proposed, and it solves the related theory, method and technology of multi-hierarchy mapping of availability for GNSS. The main reaserch work and innovations of the dissertation are as follows:(1) The dissertation proposes a framework of multi-hierarchy mapping for availability based on error transfering process for the whole availability for GNSS. Through analyzing the difficulties of analysis the whole availability for GNSS base on the reliability of the components of GNSS, the dissertation study the the basic working process of GNSS, and proposes the hierarchy concept system of availability for GNSS based on flow process for the signal and information of navigation, and for the first time systematic and comprehensive characterizes the concept of availability for GNSS, which is composed of the system-availability, the link-availability and the service-availability. Based the concept system and the transfering process of the User Equivalent Range Error(UERE) in the flow process for the signal and information of navigation, the dissertation proposes a method framework for multi-hierarchy mapping analysis of availability for GNSS, and the availability can be divided into navigation system resource layer, navigation link layer and navigation user service layer in the framework. And the dissertation bulilds the relation model between each layer and defines availability analysis model for each layer.(2) The dissertation establishes the availability analysis model for the single navstar based on the theory of Continuous-Time Markov Chain(CTMC) and Semi-Markov Process(SMP).For the life cycle and the repair time of the keyload compoents of the navstar obeys exponential distribution, through analyzing the characteristics of the CTMC modeling, the dissertation studies the analysis process of instantaneous availability based on CTMC, establishes a general analysis model of navstar availability based on CTMC, and verify with the calculation of the availability of single component of navstar. For the life cycle and the repair time of the keyload compoents do not strictly obey the exponential distribution, the dissertation studies the reduced-modeling based on SMP, and bulids a solution method for availability analysis model for the single navstar. Lastly, the dissertation studies the attribute weight index of the satellite, and establishes the availability analysis model for the GNSS constellation based on the capacity measure.(3)In order to establish the relationship between system-availability and service-availability, the dissertation proposes an mapping method for link-availability based on Age Of Data(AOD). Baesd on the solving principle of the GNSS and influence factors of system faults, the dissertation studies the main influence factors of the UERE. For the view of the ground network, the dissertation proposes the key index of the info-availability,which includes completeness, accuracy, timeliness of the navigation information, and bulids the availability analysis model of the information based on GNSS AOD, and quantifies the mapping relationship between information availability and AOD. Lastly, according to the healthy and coverage of the navigation signal, the dissertation bulids the linear relationship model between AOD and User Range Error(URE), and proposes the the model of UERE error budget based on AOD, and verify the rationality of the model by GALILEO’s data.(4)For the service-availability, the dissertation bulids the service availability analysis model based on Weighted Dilution of Precision(WDOP). Through analyzing the DOP algorithm with uniform constellation, the dissertation studies the weighted DOP algorithm for mixed constellation, and according to the temporal and spatial accuracy of simulation analysis, bulids the principle which the regional grid precision is in [5°,9°], time resolution is at least 60 seconds, then establishes the availability model of accuracy based on WDOP for the local regional constellation. Through analyzing the index of the integrity for GNSS, the dissertation studies the RAIM algorithm for multi-GNSS and process for fault judgment and recognition of multi-fault satellite, and establishes integrity availability analysis model based on RAIM for multi-GNSS. Finally, the dissertation detailed studies the continuity model for GNSS and establishes availability model of continuity based on WDOP for the local regional constellation.(5) Based on the above research and the availability analysis models, the dissertation discusses the simulation model framework based on Simulation Model Portability Standard 2.0(SMP2.0), developes a model system of navigation field for availability analysis, design and implementation the simulation prototype system for availability analysis of GNSS. Finally, focuses on addressing the navstar backup strategy for the local regional constellation, the dissertation tests its strategy based on the simulated availability, and verify the feasibility of the method.