BDS Integrity Monitoring And Availability Assessment

With the rapid development of GNSS(Global Navigation Satellite System) and gradual depth theoretical study, the basic properties of navigation and positioning service have been greatly improved, GNSS applications also will be widened. China has independently developed the BDS(Bei Dou Navigation Satellite System) which has started to provide service for the Asia-Pacific region December 27, 2012. Users want navigation information while integrity and availability is guaranteed, so in order to enhance the core competiveness in the future market, the establishment of integrity monitoring frame and availability evaluation criterion has become essential. Based on this background, from the system, user, space signal integrity monitoring to service availability is analyzed. The main research work as follows:(1) For BDS users care about integrity monitoring is available and minimum detectable ability, in this paper, the Asia-Pacific simulation grid data(spatial variation) and four BDS tracking station data Asia-Pacific region uniformly distributed(temporal variation), based on quality control theory, integrity availability of the constellation and MDE(Minimal Detectable Effect) on the analysis. The results show that: either spatial variation or temporal variation, the integrity monitoring algorithm of NPA(Non Precision Approach) phase is available in the Asia-Pacific region(except marginal corner area individual sessions). From the spatial variation analysis, the average MDE is 1.796 m, from the temporal variation analysis, the average MDE is superior to 6m. The HPL(Horizontal Protection Level) of receiver autonomous integrity monitoring is applied to assess the location boundary. The results show that: the HPL can meet the NPA phase integrity requirement in the Asia-Pacific region.(2) In view of BDS space signal error can satisfy user requirement, this paper from URE(User Range Error)and SISMA(Signal-In-Space Monitoring Accuracy)to evaluate space signal error. The results show that: the average URE of BDS within 5m which can meet the demand of real-time navigation users. For space navigation signal accuracy of monitoring information is reliable, in this paper, using the Asia-Pacific regional monitoring network to evaluate SISMA, the results show that: the BDS satellite passing over the Asia-Pacific region could satisfy the SISMA requirement of SOL(Safety-Of-Life Service), reliability of 100%(except C12 97.92%).(3) For BDS space satellite signal on a single satellite failure affect the availability and service availability meets the needs of users. In this paper, the three kinds of BDS satellite fault on single satellite availability is analyzed, the results show that: the inherent reliability of satellite availability decreases 2.66%, the impact of orbital maneuver on single satellite availability is smaller than the single event upset(recovery time 12 h, 24h) and the combined effect of three kinds failure is bigger than unilateral factor. In this paper, considering the accuracy and integrity availability, the model of weighted assessment availability is used to evaluate BDS service availability. The results show that: BDS availability above 95% in the Asia-Pacific region(except marginal corner area), can meet the user requirement. After BDS GEO satellite orbit maneuver occurs, it will result in the BDS availability of the Asia-Pacific region with varying degree of decline.