Horizontal Advanced RAIM Performance Sensitivity to Mischaracterizations in Integrity Support Message Values

With the growing availability of navigation satellite constellations from more than one service provider, emergence of multi-constellation Global Navigation Satellite System (GNSS) makes it possible to develop Receiver Autonomous Integrity Monitoring (RAIM) capability with improved range measurement redundancy and accuracy. An emerging concept for receiver avionics that leverages the availability of multiple constellations, called Advanced RAIM (ARAIM), is being developed with a vision of not only providing worldwide approaches with vertical guidance, (Localizer Performance with Vertical Guidance, LPV-200, in particular) but it would also significantly expand Required Navigation Precision (RNP) operations availability worldwide. In the design of ARAIM, this improved capability stems mainly from introduction of an Integrity Support Message (ISM). The ISM is a periodically updated set of parameters that represent the statistical characterization of the core navigation constellation performance. This ISM is received by and utilized in the user avionics as a priori information in the ARAIM user algorithm. One critical issue is that when the statistical characterization of the core constellation performance is not accurate, ARAIM integrity performance may degrade. In our previous paper, we analyzed the sensitivity of Vertical ARAIM (V-ARAIM) performance to the ISM parameter deviations, leading to very interesting and important findings regarding ISM sensitivity. In our analysis, the term "deviation" is used to refer to an increase in the ISM values representative of actual core constellation performance relative to the broadcast ISM parameter values. In this paper, we extend the earlier analysis to Horizontal ARAIM (HARAIM). H-ARAIM requires a fault exclusion capability to meet the stricter RNP continuity requirements. The purpose of this paper is to see how the sensitivity characteristics of ARAIM to ISM deviation from actual values differ between H-ARAIM and V-ARAIM. The analysis in this paper, along with the analysis done previously for V-ARAIM, will help develop procedures that could be applied consistently and systematically to determine a set of "close-to-optimal" ISM parameter values to broadcast. This will facilitate global acceptance of an ISM update process.