Sensitivity Analysis And Verification Of Navigation Messages To Positioning Performance

With the increase of people's dependence on GPS,GPS security problem is more and more important.Therefore,it is necessary to analyze the influence of interference and deception on the positioning performance.In addition to using traditional broadband or narrowband interference signals,sending GPS spoofing signals with false navigation messages is also a common mode of interference.The latter is more deceptive and concealment,so it is difficult to be detected and has great impact on GPS security.Under such circumstances,this thesis classifies the navigation message parameters according to the sensitivity degree of the positioning performance,then focuses on monitoring and protecting the sensitive parameters,thus protecting the weak links of GPS effectively and improving the security of the system.To this end,this thesis analyzes the sensitivity of GPS navigation message to the positioning performance,and then verifies our analysis.Firstly,the positioning error is formulated which caused by the errors in different navigation messages parameters.Specifically,with the time message parameters and ephemeris parameters as the starting point,the nonlinear positioning equation is transformed and processed by using the first order linear approximation.Hence,the quantitative relationship between the parameter deviation and the positioning error can be derived.Then the sensitivity of the positioning performance to a message parameter is determined.Besides,the applicable condition of quantitative relation is obtained.Secondly,the correctness and validity of sensitivity analysis are verified from two aspects.On one hand,the error source whose message parameters are modified without the presence of real GPS signal is generated to verify the correctness and applicable conditions of the above-mentioned quantitative relationship.On the other hand,the deception signal source whose message parameters are modified in the presence of real GPS signals is constructed,and the receiver is traversed to track the false signal by utilizing the sliding of C/A code in generative spoofing jamming.Next,the positioning results are used to evaluate the value of sensitivity analysis.Ultimately,it provides support for the research of GPS security.