Evaluation of APNT systems to support PBN operations in lieu of GNSS over Indian air space

At present airborne navigation is primarily dependent on GNSS to enable Performance Based Navigation (PBN) services, both Area Navigation (RNAV) and Required Navigation Performance (RNP), to aviation users on a global scale. However, due to the apparent increase in the disruption of GNSS signals in the airspace due to radio frequency interference (RFI), in the event of loss of GNSS, this dependency may lead to inefficient use of airspace and potentially lead to service degradation. Thus, making the sole reliance on GNSS untenable highlighting the need for RNP services based on terrestrial sources. A key aspect of making PBN resilient to RFI and other GNSS threats is to evaluate the current capability and drive modernization of Alternate Positioning, Navigation and Timing (APNT) systems to support seamless RNP operations. Improvements in PNT integration with other aircraft systems and enhancements in RFI situational awareness provided to operators/flight crews are essential to fully exploit the capabilities provided by resilient GNSS augmented with APNT systems. This paper recommends technologies for Civil Aviation Authorities to consider, to make PBN services more resilient to GNSS RFI and other threats over the Indian Airspace. The analysis here considers diverse, viable PNT alternatives to GNSS for Conventional Air Transport (CAT). The paper proposes performance criteria to evaluate the existing terrestrial radio navigation systems currently deployed in the Indian airspace, thereby providing a means to determine their ability to support seamless RNAV/RNP operations with or without GNSS.