Improved ARAIM fault modes determination scheme based on feedback structure with probability accumulation

Abstract

Advanced receiver autonomous integrity monitoring (ARAIM), based on multi-constellation and dual-frequency, can provide vertical navigation in terminal approaches. The baseline ARAIM receiver algorithm is based on the multiple hypothesis solution separation (MHSS). The fault modes determination scheme, proposed in the ARAIM baseline algorithm, is a sequential structure and a core processing which can be summarized in three steps: calculating the maximum number of simultaneous faults, forming all subsets, and filtering the subsets. The fault modes determined by the maximum number of simultaneous faults are sufficient, but not necessary. A set of redundant fault modes is included, which reduces the ARAIM performance and increases the computation burden. The continuity risk is not considered in the filtering. We propose a new fault modes determination scheme based on feedback structure with probability accumulation. The number of fault modes in the baseline algorithm is defined subject to a given integrity risk requirement. In the proposed algorithm, the fault modes are directly determined subject to this parameter. The fault modes are accumulated in descending order of fault probability. The probability of not monitored risk obtained in probability accumulation is closer to the integrity risk requirement compared to the baseline method, and the number of fault modes is reduced noticeably. The continuity detection is added to the feedback structure to find the severe integrity risk in time. The fault modes, determined in the proposed scheme, are sufficient and necessary. The performance evaluation results under a GPS-Galileo dual-constellation situation for localizer precision vertical 200 (LPV-200) requirements show that the proposed scheme can improve the availability of ARAIM from 84.92 to 92.25%. An enhanced effective monitor threshold (EMT) mainly contributes to this improvement. Furthermore, the proposed scheme also shows positive superiority in calculation load. The reduction in fault modes can directly contribute to the alleviation of the receiver calculation burden, which saves nearly 40% computational time on a PC-based software-defined receiver.