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Implementing Resilient PNT in the Real World: How to Choose a Test Methodology

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As the IEEE prepares to introduce new resilience standards for PNT systems, our webinar offers insights on how PNT system posture and resilience could (and should) be tested at the RF and infrastructure levels.

The world is becoming more reliant on positioning, navigation and timing (PNT) systems. From the grandmaster clocks that control the flow of electricity through energy grids, to the navigation systems that guide container ships into port, many of the systems we often take for granted rely on precise location and timing data from global navigation satellite systems (GNSS).

Protecting those systems against threats is becoming ever more important, as the risks of not doing so become more apparent. In 2020, a commercial airliner narrowly avoided crashing into a mountain after its GPS navigation system was jammed by a nearby military exercise. A year earlier, the New York City Wireless Network (NYCWiN) was knocked out for several days after the city failed to patch GPS receiver firmware to handle a long-planned week rollover event.

Incidents like these (and many others) are behind a new effort to develop resilience standards for GNSS receivers and the systems that depend on them. The IEEE is in the process of developing the standards, building on a five-level resilience framework published in December 2020 by the U.S. Department of Homeland Security (DHS).

Resilient PNT standards are on their way, but testing won’t be easy

Once the standards are published, the task of measuring how well systems conform to them will fall to developers, integrators and end-users of PNT-dependent systems. That won’t be easy, not least because it requires security expertise in both the radio frequency (RF) and information technology (IT) domains.

Typically RF security (protecting radio equipment like GPS receivers against disruptive RF signals) and cybersecurity (protecting IT systems against malware and targeted hacker attacks) have been separate disciplines, carried out at different stages of the supply chain. Enterprise cybersecurity rarely extends to testing – or even thinking about – the GNSS chipsets embedded in timing clocks or vehicle fleets; they’re just assumed to be up to scratch for the job.

But, as we explain in the third and final webinar of our Implementing Resilient PNT in the Real World series, the vulnerabilities of PNT-dependent systems must increasingly be understood at both the subsystem (receiver) level and the system-of-systems level. That means drawing up a test methodology that encompasses both the RF and IT layers of the system.

Testing RF resilience: Considerations and methodologies

In the first of two presentations, Spirent Director of PNT Simulation Ajay Vemuru recaps the threats to PNT-based systems at the RF level – from frequency jamming to sophisticated spoofing attacks. He then set out the options for testing and measuring the resilience of GNSS chipsets and receiver modules in the face of such threats.

He looks at the relative merits of testing using live-sky signals, signal simulation and RF record and playback, and explains why testing for conformance to resilience standards is likely to require a combination of all three approaches. The presentation dives deeper into the use of RF signal simulation to enable repeatable lab testing of receiver resilience to threats including jamming, spoofing, multipath and GNSS system errors.

Finally, Ajay looks at the importance of testing at the system-of-systems level, particularly for developers and integrators of multi-sensor PNT systems like positioning engines for autonomous vehicles. The need to test each sensor independently is highlighted, as well as the need to test the performance of sensor fusion algorithms when one or more sensors is compromised.

Testing IT cybersecurity of PNT systems

In his presentation, Spirent PNT cybersecurity specialist Aleksander Gorkowienko provides some insights into the different types of bad actor who pose a threat to PNT systems, their motivations for trying to hack those systems, and the evolving methods used to do so.

He reviews the vulnerabilities inherent in the IT elements of a PNT-dependent system, from hardware and firmware to software applications and IT infrastructure, and outlines methodologies for assessing and assuring their resilience.

For those unfamiliar with current IT cybersecurity practices, he also includes an introduction to the latest evolution in PNT cybersecurity thinking as it moves from threat detection and response to a zero-trust, Defence in Depth approach.

Measuring the resilience of PNT systems in line with the emerging IEEE standards is likely to present challenges, even for the most experienced test teams. To that end, both Aleksander and Ajay outline how Spirent can help with testing the resilience of GNSS receivers and the wider PNT systems of which they are a key component.

Watch the full webinar: A Proposed Test Framework for Robust PNT

The whole Implementing Resilient PNT in the Real World webinar series is now available on demand, which includes:

  • The Challenges of Standardising PNT Resilience: Understanding the Reliance on PNT and an Outline of Key Vulnerabilities, presented by Guy Buesnel, PNT Security Technologist at Spirent, and Duke Buckner, Head of Strategy and Business Development at Microchip

  • Preparing for Compliance to PNT Resilience Standards: Conducting a Risk Assessment of Your Exposure to PNT Threats and Understanding the Impacts on Your Business, presented by Guy Buesnel and Dana Goward, President of the Resilient Navigation & Timing Foundation

  • A Proposed Test Framework for Robust PNT: Looking at the Equipment and Methodologies to Apply in the Lab, and Incorporating PNT into Your Cybersecurity Framework, presented by Ajay Vemuru and Aleksander Gorkowienko of Spirent

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Guy Buesnel
Guy Buesnel

CPhys, FRIN, Product Manager – GNSS Vulnerabilities

Guy has more than 16 years experience in working on Robust and Resilient Position Navigation and Timing, having started his career as a Systems Engineer involved in developing GPS Adaptive Antenna Systems for Military Users. Guy has been involved in GPS and GNSS Receiver System Design with the aim of designing a new generation of Rugged GNSS Receivers for use by Military and Commercial Aviation Users. Guy is a Chartered Physicist, a Member of the Institute of Physics and an Associate Fellow of the Royal Institute of Navigation