Advanced RAIM Performance Sensitivity to Deviation of ISM Parameter Values

Abstract

The Advanced Receiver Autonomous Integrity Monitoring (ARAIM) concept based on dual-frequency multiconstellation (DFMC) Global Navigation Satellite System (GNSS) has the potential to support LPV-200 approach (localizer approach with vertical guidance with a decision height as low as 200 ft) without the need for barometric vertical guidance. The ARAIM Technical Subgroup (TSG) created by the leadership of the EU-US Cooperative Working Group (WG)-C has performed a feasibility study of ARAIM and concluded that ARAIM has the potential to achieve significant operational benefits worldwide. However, the TSG also identified challenges that must be resolved before enabling ARAIM services. One major challenge to enabling ARAIM service is determining the parameter values in Integrity Support Messages (ISMs) broadcast to user equipment. ISM is used to periodically update statistical characterization of the core GNSS constellation performance as a priori information to the airborne ARAIM algorithms. This issue has been initially addressed in the authors’ previous paper; this paper extends and builds upon that analysis. The ISM selection process requires a compromise based on solid analyses. If the ISM parameter values are not conservative enough, ARAIM may fail to detect hazardously misleading information (HMI) with the required probability; if they are too conservative, ARAIM would not achieve as high availability and coverage as it could. Moreover, Constellation Service Providers (CSPs) and Air Navigation Service Providers (ANSPs) may have opposing views in selection of ISM parameter values. While CSPs may insist on broadcasting ISM values that are not fully supported by service history or have not yet been fully validated, ANSPs may not readily accept such values. For this reason, it is important to develop an objective process to determine these parameters. As the first step toward the goal of developing systematic procedures to resolve the issue, this paper analyzes the sensitivity of ARAIM performance to the deviation of each of the broadcast ISM parameter values from the values representing the actual core constellation performance.