Research On Monitoring And Assessment Of Satellite Navigation System Performance

The Intense competition in the GNSS application has made the performance of satellitenavigation system become the key in the application competition of the satellite navigationsystem. The research on the GNSS performance monitoring and assessment methods will notonly promote satellite navigation system performance indicators, evaluation methods andperformance system，improve and upgrade the performance of satellite navigation systems，enhance the interoperability of GNSS open services，but also provide a reference for theconstruction of BeiDou system. Main contributions include the following:1. The main performance framework including basic performance and high-dimensionalperformance as the main factors was given，and the satellite navigation system performanceframe was described. The Parallel Progression Model used to describe the relationship betweenRNP indicators is presented, which provided important theoretical basis for the assessmentmethods of the RNP indicators, and also provided important theoretical basis for the conceptssuch as the continuity of the accuracy, the availability of the accuracy, the continuity of theintegrity, the availability of the integrity.2. In the aspect of accuracy assessment model, through the study of UERE decompositionbasis, UERE level model considering such signal type, frequency, user environment factors andso on was presented, which provided important framework for the UERE budget allocation. Onthe basis of this, in the case of the GPS, the contribution of the space section, control section, andother precision improvement measures as well as the user segment on UERE was analyzedrespectively, for the UERE budget providing specific quantitative basis. One kind of UEREcomputation method based on the IGS data was proposed, and the UERE characteristics wereverified using the measured data.3. From the perspective of mathematics and the measurement, the GDOP minimum valuewas studied, and the conclusion shown that the smaller the GDOP is, the more uniform satellitedistribution in the constellation is. Two metrics to evaluate constellation space layout uniformitywas constructed based on the above conclusion: instantaneous constellation geometry qualityfactor and the average geometry quality factor, and their feasibilities were verified. Analysis onthe change characteristics of DOP sampling in the time and space domain were made, theoptimal space granularity and the optimal time granularity were studied. One kind of accuracyassessment model in the constrained conditions was presented, and the tests shown that azimuthdistribution density of visual satellite and the latitudes of the observation points have closerelationship.4. The basic mechanism to realize the integrity of GPS was put forward, and the future development trend of GNSS integrity was summed up. On the basis of the differentimplementation mechanisms, the GNSS integrity was decomposed of SIS integrity and systemintegrity with the corresponding levels, providing a reference frame for the integrity research.Considering the several of fault monitoring and response mechanisms of the GPS integrity,integrity fault monitoring and reaction mechanism involving the user section, control section andthe space segment, need to consider as a whole. Based on Galileo integrity concept and therealization principle, the SISA, SISMA and the alarm mechanism algorithm were studied, andthe SISMA parameter sensitivity experiment was analyzed. the WUL algorithm is improvedbased on the geometric model. Compared with the existing similar algorithms, the algorithmgiven in this paper was theoretically simple and reliable.5. GNSS continuity level framework including SIS continuity and service continuity wasput forward, and the basic assessment model of GNSS continuity was derived based on thereliability theory, which provided a theoretical basis for GNSS continuity evaluation. SIScontinuity fault model and its features were studied. The basic assessment model of GNSScontinuity based on the reliability was carried out with the GPS data, and the results shown theproposed continuity assessment model is effective and feasible. The service continuityassessment method was studied. The continuity fault judgment and statistical methods of theaccuracy was given, so was the continuity fault judgment and statistical methods of the integrity.Considering the concept of GNSS continuity, fault level analysis, assessment methods and theGPS typical continuity event analysis, the continuity fault monitoring mechanism was putsforward for GNSS continuity monitoring.6. GNSS availability level framework including SIS availability and service availability wasput forward, and different levels fault factors of the availability were analyzed. The research onSIS availability evaluation was carried out based on the satellite fault patterns and backupstrategy. The research on the typical faults of navigation satellites laid the foundation for thefollow-up of SIS fault research. Based on analyzing the fault model of navigation satellite andconstellation backup strategy, the calculation method of availability of single satellite wasdeduced by means of the reliability principle. Based on the single satellite availability model,considering the constellation backup strategy, the constellation dynamic model based on Markovchain was put forward. Taking GPS for instance, the parameter sensitivity analysis on theconstellation state probability development within a certain period of time was carried out, on theinitial conditions of both with the single satellite availability and without.7. The interrelationship between the compatibility and interoperability and its application indifferent PNT service stages were analyzed technically. The hierarchy system of compatibilityand interoperability from SIS level to the service level was put forward. GNSS information interoperability was studied from the current realization mechanisms of GNSS spaceinteroperability and time interoperability. And the GNSS constellation interoperability concept,influence, and interoperability measurement method were studied. Taking GPS and Galileosystem as an example, the performance between single constellation system and interoperabilityconstellation system were compared. The GNSS interoperability navigation performanceimprovement was quantified using simulation method, and the results shown that theinteroperability between GNSS could greatly improve such positioning performance as accuracyand integrity.8. The performance assessment model of GNSS monitoring station was put forward, whichassessed single station coverage and inter-stations overlapping coverage. In the case of GPS, theoverall coverage performance of different monitoring station networks was analyzed, so were thedifferent schemes differences. The results further validated that the proposed GNSS monitoringnetwork evaluation methods were scientific and effective. In order to evaluate the influence ofmonitoring stations on the entire net, the influence factor and risk factor used to assessment theeffection of single station upon the whole coverage performance. The tests and analysis on thefault sensitivity of single and double monitoring stations further validated the assessmentmethods of GNSS monitoring station performance. Based on the above results and conclusionsof monitoring stations coverage performance and fault sensitivity analysis, combined with thefunction and construction cost of monitoring station network, a kind of monitoring stationnetwork design and layout method under multiple constraint conditions was given, with itsprinciple diagram.