Design And Simulation Of BEIDOU Ground Augmentation System Integrity Algorithm

Precision approach and landing of aircraft is the most critical stage during flight, navigation system need to provide extremely high positioning accuracy, using the Big Dipper as a primary means of navigation in aircraft precision approach and landing is the future direction of navigation development. Since civil aviation navigation use Beidou standard positioning, it is difficult to meet in terms of performance positioning accuracy, continuity, integrity and availability, resulting in a variety of enhanced systems, including Wide Area Augmentation System, Local Area Augmentation System and ground-based augmentation system, Integrity means that when the navigation system occur any fault or error exceeding the allowable limits, the ability to issue a timely warning, it’s an important indicator of its overall navigation engineering simulation and test evaluation system, it’s used to analyse if the data provided by satellite navigation systems for navigation is available, typically require different judgment indicators. When it exceeds the set threshold, system alarms. The integrity of the abnormal situation is very low, it may happen or may not happen a few times a year, but very critical. Therefore, this paper researches the main key algorithms among Beidou system- integrity algorithm. Compass function for the overall architecture and performance requirements of the system, integrity will be described.In this paper, ground-based augmentation system, based on research using the Beidou satellite navigation system integrity monitoring and simulation, main contents and innovations are as follows:This paper studies five aspects of integrity algorithms, including:(1) Signal Quality Monitoring(SQM)part of the algorithm is improved in signal power monitor, change the method of setting the threshold, through a lot of statistics at different elevation, the result of SNR set threshold. In the code / carrier separation process, because the original code / carrier divergence monitoring algorithm used to improve the convergence speed is not satisfactory, where in order to improve the convergence rate, using a continuous time to replace the original set of constants.(2) Data Quality monitoring(DQM) is not using the original Star distinctly book to determine the location of satellites, users choose YE-TE method instead. This satellite ephemeris compared with the ephemeris broadcasted by the reference receiver the last time the satellite passed by the reference receiver, compared ephemeris data may be ephemeris data 1 hour ago.(3) Measurement Quality Monitoring(MQM)detect the carrier phase measurements and pseudo-range measurements are the same in the last several epochs, to detect anomalies or because the satellite clock reference transient faults caused by hopping receiver and other fast-changing errors.(4) Multiple Reference Consistency Check(MRCC) check to check each satellite correction in consistency among multiple receivers, excluding single receiver may cause a large difference BRANCH positive error exception.(5) Verify that tMessage Field Range Test(MFRT) pseudorange correction and correction rate consistent with the message format is valid.At the same time after a lot of experiments to determine the appropriate threshold, an appropriate threshold so that erroneous data will not be treated as an correct data processing, nor will correct erroneous data as data processing, reduce the incidence of integrity risk.For the first time compass the integrity in the aircraft approach and landing, improved accuracy of the approach and landing.By monitoring the integrity algorithm described above, reducing the integrity risk when aircraft approach the road, after a lot of sports car test, ver ify the integrity algorithm can reduce the risk, now we have begun to use this algorithm in Tianjin Airport.