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PNT Protection through Interference Monitoring and Robust Backups to GNSS

Central to civil infrastructure (e.g., transportation, communications) is the problem of robust and secure position, navigation and timing (PNT). This is especially true of urban environments, which offer more challenges, such as interference and multipath, when compared to open-sky conditions. As the only positioning system that currently offers absolutely-referenced meter-level accuracy with global coverage, the Global Navigation Satellite System (GNSS) will no doubt play a significant role in civil infrastructure going forward. For example, if strengthened against jamming and spoofing, carrier-phase-differential GNSS (CDGNSS), coupled with low-cost inertial sensing, will be nearly sufficient for position, velocity, and timing (PVT) needs of urban air mobility (UAM). But nearly sufficient is insufficient: it is not enough for a UAM PVT solution to offer decimeter-accurate positioning with 99% availability, or even 99.9% availability. UAM will demand that its navigation systems offer dm-accurate positioning with integrity risk on the order of 10e-7 for a meter-level alert limit and availability with several more 9s than 99.9% This proposal’s work in PNT protection is best viewed as part of a comprehensive navigation and timing solution concept called deep-layered navigation (DLN) in which synergistic but independent navigation systems are layered to increase accuracy and robustness. DLN is the navigation analog of the “defense in depth” concept in information security, where multiple layers of security controls and checkpoints are emplaced throughout a system such that even when some layers are breached, security is maintained. Likewise, in the safety-of-life UAM navigation context, multiple layers of navigation and timing systems, all interoperable and mutually-reinforcing but substantially independent, are an essential defense against the whims of Mother Nature and the foibles of human nature. At DLN's core sits redundant inertial navigation, which is virtually impervious to radio frequency (RF) interference, poor weather, signal blockage, and data ambiguity. The outermost layer---the default navigation system and first line of defense---is a specialized variant of inertially-aided CDGNSS, recently developed in the UT Radionavigation Laboratory that has been substantially secured against spoofing and substantially hardened against the multipath and signal blockage conditions of the urban ground vehicle environment, which can be considered a worst-case realization of the urban air vehicle environment. But despite its coupling with inertial sensing, the technique developed in the UT RNL cannot tolerate extended GNSS outages. A secondary source of absolute PVT is required to bound the growth of position errors. Fusion of GNSS and signals of opportunity (SoPs) has been explored by the CARMEN+ team with promising results. For a safety-of-life application like UAM, SoPs will be viewed less favorably than a dedicated system such as GNSS. But SoP availability, ample bandwidth, and strong received power nonetheless make them an appealing component of any deep-layered navigation and timing strategy. Compared to terrestrially-sources SoPs, SoPs from LEO mega-constellations such as SpaceX's Starlink, Amazon's Kuiper, and OneWeb enjoy the advantage of vastly broader---indeed, nearly global---coverage. The downlink signals from these constellations are also carried on higher frequencies (Ku-band for Starlink and OneWeb; Ka-band for Kuiper), whose short wavelengths permit use of small phased-array receiver antennas capable of forming narrow (few degrees) beams toward their serving satellites. Narrow beamforming makes such systems naturally resilient to radio interference. The research team proposes to develop novel signal capture, processing, and estimation techniques that will enable extraction of navigation and timing measurements from broadband mega-LEO signals of opportunity. The research team envisions broadband LEO-based PNT as a novel and useful component in a comprehensive deep-layered navigation and timing system for civil transportation and infrastructure. GNSS receivers in Low Earth Orbit (LEO) are a proven asset for detecting, classifying, and geolocating terrestrial GNSS interference that can be a danger to civil aviation, maritime, or ground vehicle traffic. Emitter geolocation from LEO offers worldwide coverage with a frequent refresh rate, making it possible to maintain a common operating picture of terrestrial sources of interference. The research team proposes to further develop and demonstrate techniques whereby GNSS interference signals captured by a single satellite or by multiple satellites can be used to characterize and geolocate the signals’ source. The research team will pursue single-satellite, multi-satellite-indirect, and multi- satellite-direct techniques to obtain geolocation solutions optimized for context and performance. The research team's focus in this next year will be on single-satellite geolocation solutions.

Language

  • English

Project

  • Status: Active
  • Funding: $285000
  • Contract Numbers:

    69A3552348327

  • Sponsor Organizations:

    Office of the Assistant Secretary for Research and Technology

    University Transportation Centers Program
    Department of Transportation
    Washington, DC  United States  20590
  • Managing Organizations:

    Center for Automated Vehicle Research with Multimodal Assured Navigation

    Ohio State University
    Columbus, OH  United States  43210
  • Project Managers:

    Kline, Robin

  • Performing Organizations:

    University of Texas at Austin

    Austin, TX  United States  78712
  • Principal Investigators:

    Humphreys, Todd

  • Start Date: 20240801
  • Expected Completion Date: 20250831
  • Actual Completion Date: 0
  • USDOT Program: University Transportation Centers

Subject/Index Terms

Filing Info

  • Accession Number: 01937757
  • Record Type: Research project
  • Source Agency: Center for Automated Vehicle Research with Multimodal Assured Navigation
  • Contract Numbers: 69A3552348327
  • Files: UTC, RIP
  • Created Date: Nov 21 2024 5:26PM