PT - JOURNAL ARTICLE AU - Lo, Sherman AU - Chen, Yu-Hsuan TI - Automatic Dependent Surveillance-Broadcast (ADS-B) Universal Access Transceiver (UAT) transmissions for Alternative Positioning, Navigation, and Timing (APNT): Concept & practice AID - 10.1002/navi.424 DP - 2021 Jun 20 TA - NAVIGATION: Journal of the Institute of Navigation PG - 293--313 VI - 68 IP - 2 4099 - https://navi.ion.org/content/68/2/293.short 4100 - https://navi.ion.org/content/68/2/293.full SO - NAVIGATION2021 Jun 20; 68 AB - The vulnerability of Positioning, Navigation, and Timing (PNT) services derived from Global Navigation Satellite Systems (GNSS) makes having a resilient and accurate Alternative PNT (APNT) based on high-power terrestrial radio sources necessary. The L-band is very crowded spectral real estate with GNSS, Distance Measuring Equipment (DME) and Air Traffic Control Beacon System (ATCRBS) signals occupying the band from 900–1600 MHz. Thus, as getting new signal and spectrum for APNT would be difficult, we must leverage existing transmissions and infrastructure. The ∼660 Automatic Dependent Surveillance-Broadcast (ADS-B) ground stations in the United States represent significant infrastructure that can be leveraged for APNT. However, as ADS-B was designed for surveillance, it does not inherently possess features necessary to support APNT goals. This paper describes and demonstrates techniques for using ADSB Universal Access Transceiver (UAT) signals for PNT. We develop methods to use all ground UAT signals to provide robust, multi-frequency pseudoranges. We examine the ranging and positioning performance of the UAT signal on the ground and in flight, to demonstrate its ranging accuracy, and hence the timing and synchronization of the station. We demonstrate and analyze navigation using UAT signals, as well as the intra-system interference challenges of using multiple UAT stations.