基于GPS的地基增强系统机载端完好性算法研究

针对地基增强系统（GBAS）非完好性事件的极端性，开展GBAS完好性算法研究，给出H0和H1假设下的机载端保护级计算方法，并分析GBAS中引起“虚警”和“漏警”两类非完好性事件的主要误差源。实验结果表明，机载端伪距经过差分校正后其位置精度优于1 m，可用性大于99.999 9%，满足CAT Ⅰ精密进近着陆导航需求。同时，进行非完好性事件仿真验证的结果表明，卫星几何分布和电离层风暴是引起“虚警”和“漏警”的主要误差源，未来CAT Ⅲ GBAS需将单星座扩展为包括北斗在内的多星座，将单频升级为双频，其中多星座可以优化卫星的几何布局，双频可以消除电离层风暴的影响。

Research on Airborne Integrity Algorithm for Ground BasedAugmentation System Based on GPS

In view of the extremes of the non-integrity events of the ground based augmentation system(GBAS), we study the integrity algorithm of GBAS. We give the calculation method of airborne protection level under H0 and H1 assumptions, and analyze the influences of the main error sources of two kinds of non-integrity events, false alarm and missed alarm. We carry out verification experiments, and the experimental results show that the accuracy of the position solution of the airborne terminal after differential correction is better than 1 meter, and its availability is greater than 99.999 9%, which meets the requirements of class Ⅰ precision approach and landing navigation. At the same time, we carry out simulations of non-integrity events, and the results show that the geometric distribution of satellite and ionospheric storm are the main error sources of false and missed alarms. In the future, class Ⅲ GBAS needs to expand the single constellation to multiple constellations including Beidou, and upgrade the single frequency to dual frequency. Among them, multiple constellations can optimize the geometric layout of satellites and dual frequency can eliminate the ionospheric storm impact.