Continuity and availability in Dual-Frequency Multi-Constellation ARAIM

Future multi-constellation global navigation satellite systems (GNSS) will provide a greatly increased number of redundant ranging signals, which can improve integrity monitoring capability using receiver autonomous integrity monitoring (RAIM). Advanced RAIM (ARAIM) aims at providing localizer precision with vertical guidance down to 200 feet altitude (LPV-200) for worldwide aircraft landing navigation. This paper assesses the need of exclusion for continuity and availability in future dual- Frequency, multi-constellation ARAIM. The first part of the paper is a three-part analysis of the need of fault- exclusion at the aircraft for continuity. First, an interpretation of 'average sense' continuity is given, which is specified but not fully defined by the International Civil Aviation Organization (ICAO). Second, a critical satellite analysis is carried out to show that, for future multi-constellation GNSS, the impact of unscheduled satellite outages is small as compared to other sources of loss of continuity. Third, the paper shows that fault-exclusion at the aircraft is not required to meet the LPV-200 continuity risk requirement using dual- constellation GPS/Galileo ARAIM. The second part of the paper addresses the need of airborne exclusion for availability. Without airborne exclusion, ARAIM service outages due to fault detection can potentially last for one hour or longer. Such periods of continuous outage are highly undesirable. In response, fault exclusion methods can help reduce service outage periods at the cost of increased integrity risk due wrong exclusions. In this paper, availability is evaluated using ARAIM detection- Only as compared to using ARAIM detection-and- exclusion. Results indicate that outage duration can be significantly reduced without substantial decrease in overall integrity performance.