Reduced Subset Analysis for Multi-Constellation ARAIM

Advanced Receiver Autonomous Integrity Monitoring (ARAIM) seeks to exploit the large number of ranging signals provided by the multiplicity of Global Navigation Satellite System (GNSS) core constellations. Including more satellites increases the number of potential fault modes and the number of subset solutions that need to be evaluated by the receiver. In this paper we describe methods for reducing the total number of subsets to be evaluated. This approach neglects many of the less likely scenarios and uses subsets that exclude entire constellations to evaluate other multiple satellite fault scenarios. We further specify which subsets to evaluate given certain ranges for the probability satellite and constellation fault modes. By specifying a reduced number of overall evaluations, and the conditions that separate using one set of subsets versus another, we can dramatically simplify the overall user airborne algorithm. This approach reduces the computational load for each given set of satellite and constellation fault probabilities.