Techniques to Provide Resilient Alternative Positioning, Navigation, and Timing (APNT) Using Automatic Dependent Surveillance - Broadcast (ADS-B) Ground Stations

Sherman Lo, Yu Hsuan Chen, Per Enge, Mitch Narins

Peer Reviewed

Abstract:	The United States Federal Aviation Administration (FAA) Alternative Positioning, Navigation, and Timing (APNT) program is examining the use of existing FAA terrestrial infrastructure to provide navigation capable of continuing US National Airspace System (NAS) operations should Global Navigation Satellite System (GNSS) position, navigation, and timing (PNT) services be unavailable. The approximately 700 automatic dependent surveillance broadcast (ADS-B) ground stations in the United States, these ground stations represents a key existing infrastructure that can be leveraged to deliver APNT. However, ADS-B was not designed to provide high accuracy/high integrity navigation services – it was designed to provide surveillance to air traffic control (ATC) automation systems to support the safe separation of aircraft and advisory services to pilots. As a result, ADS-B transmissions do not inherently possess features, such as ranging or integrity, necessary to support APNT navigation requirements. This paper describes and analyzes some possible means for aircraft to use ADS-B ground station signals for precise positioning or ranging to support area navigation (RNAV) and potentially required navigation performance (RNP). The paper first provides background on the United States (US) APNT and ADS-B programs. It examines how ADS-B signals can support APNT by either providing positioning directly or by providing ranging. The benefits and drawbacks to using position reports versus ranging from the ground is discussed. The body of this paper examines the two ADS-B protocols implemented in the US: Universal Access Transceiver (UAT) and Mode S Extended Squitter (ES) and how each could be modified to support pseudo and/or true ranging. Additionally, the paper explore ranging based on the combined use of signals from both protocols and how leveraging each protocol’s unique features could help overcome some of the limitations of using a single protocol alone.
Published in:	Proceedings of the 2015 International Technical Meeting of The Institute of Navigation January 26 - 28, 2015 Laguna Cliffs Marriott Dana Point, California
Pages:	71 - 83
Cite this article:	Lo, Sherman, Chen, Yu Hsuan, Enge, Per, Narins, Mitch, "Techniques to Provide Resilient Alternative Positioning, Navigation, and Timing (APNT) Using Automatic Dependent Surveillance - Broadcast (ADS-B) Ground Stations," Proceedings of the 2015 International Technical Meeting of The Institute of Navigation, Dana Point, California, January 2015, pp. 71-83.
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