Research On RAIM Availability Prediction Technology Of BDS

Receiver Autonomous Integrity Monitoring(RAIM)is an algorithm in the satellite navigation receiver,which checks the consistency of navigation solution results through redundant observation information of the satellite,so as to achieve the purpose of integrity monitoring.If RAIM is not available,the airborne equipment cannot guarantee the integrity of the positioning result,and the security of users will be threatened.Therefore,the availability of RAIM needs to be predicted to avoid users running at a time-space point where RAIM is not available.The basic theory and method of RAIM availability prediction are studied based on the application of BeiDou Navigation Satellite System in civil aviation.On the basis of theoretical research,the BeiDou RAIM availability prediction software is independently designed and developed to realize the RAIM availability prediction of airports,routes and regions.The main research content is divided into the following aspects:Firstly,the principle of pseudo-range positioning of BeiDou Navigation Satellite System is introduced in detail,and the pseudo-range observation equation is linearized.Two snapshot RAIM algorithms,least square residual method and parity vector method,are studied.The relationship between missed detection rate,false alarm rate,visible stars and detection threshold is analyzed,and the equivalence of two methods is proved.Secondly,the RAIM prediction technology is studied.Based on the traditional RAIM FD availability prediction,the prediction process including RAIM FD availability and RAIM FDE availability is given.The user location determination,satellite visibility prediction,and RAIM availability determination in the prediction algorithm are sequentially implemented according to the prediction process.Thirdly,the RAIM availability prediction simulation analysis is carried out.The SMBV100 A signal source is used to simulate satellite operation,and the accuracy of prediction results is verified by the receiver receiving data in real time.The effects of DOP values and with or without barometric altitude assistance on RAIM availability are simulated and analyzed.The availability of RAIM in the different scenarios is predicted andthe prediction results are analyzed.On the premise of satisfying RAIM availability,different satellite faults are simulated.Then the faults are detected and eliminated,and the positioning errors before and after fault elimination are compared and analyzed.Finally,the modules of BeiDou RAIM availability prediction software are introduced in detail,and the prediction results of the software are demonstrated by examples.