Analysis of Advanced RAIM Performance Degradation Caused by Integrity Support Message Parameter Errors and Neglecting Nominal Bias Errors

Advanced Receiver Autonomous Integrity Monitoring (ARAIM) has recently emerged as a promising candidate for future Global Navigation Satellite Systems (GNSS) that has the potential to achieve worldwide Localizer Performance with Vertical Guidance approach operations capability with a decision height as low as 200 ft (LPV- 200). A major challenge to enabling ARAIM service is the definition and provision of the ARAIM Integrity Support Message (ISM) that provides statistical characterization of the core GNSS constellations as a priori information to the airborne ARAIM algorithm. This paper presents the results of an analysis of the continuity and integrity, specifically the false alert probability (Pfa) and the probability of hazardous misleading information (Pr{HMI}), of the ARAIM algorithm as a result of core GNSS constellation performance deviation from the performance reflected in broadcast ISM parameter values. A brief summary of the key elements of the current baseline ARAIM algorithm is described to facilitate the presentation of the results of the analysis. This baseline algorithm was developed by the EU-US Cooperative Satellite Navigation Working Group C (WG-C) ARAIM Technical Subgroup (TSG). The analysis shows that both the continuity and integrity degrades with the deviation of true ISM values (i.e., values reflecting actual constellation performance) from the broadcast ISM values. This paper also investigates the sensitivity of Pfa depending on how the ranging signal bias errors in nominal conditions are characterized. The underlying causes of high sensitivity are investigated and explained. Uncovering these underlying causes points to potential solutions that fine-tune the baseline ARAIM algorithm to overcome the high Pfa. A summary of the analysis results and proposed future work are provided at the end of the paper.