Resilient Timekeeping for Critical Infrastructure

John Fischer

Abstract:	GNSS provides excellent time accuracy for synchronizing many commercial applications – datacenters, communication networks, power and process control operations, and more. However, when these applications are part of critical infrastructures, which many are, then the susceptibilities of GNSS to jamming and spoofing can undermine the operation. Resiliency is needed. This presentation will describe several ways that GNSS timing systems can be made more resilient for critical infrastructure. Specifically: 1. Interference Detection and Mitigation (IDM) techniques – analyzing the received GNSS signal can offer great insight into whether the signal is legitimate or not. The Dept. of Homeland Security has issued guidelines for protective measures for GPS receivers used in critical infrastructure, but additional methods are possible when all the GNSS constellations are considered. Also, advanced filtering techniques can eliminate some of the popular low-cost jamming signals in use today. 2. Anti-jam antennas – the best way to combat jamming and spoofing is not to allow the bad energy into the receiver in the first place. Directional, tracking and null steering antennas are available to block several types of jammers and spoofers but can become more costly as you add more protection. A cost-performance comparison will be shown along with real-world test results. 3. Augmentation with alternative signals such as Satellite Time and Location (STL) from Low Earth Orbit (LEO) constellations – though less accurate than GNSS, these much stronger signals provide a high level of interference and jamming protection. Moreover, the strong encryption protection is impervious to spoofing. These signals can be used in conjunction with GNSS to authenticate location (i.e., guarantee GNSS is not getting spoofed), as well as alone during periods of GNSS spoofing or denial. STL signals are available worldwide today. 4. Next Generation Receivers – multi-frequency, multi-constellation receivers are becoming more affordable for widespread commercial use. Some are beginning to offer machine learning techniques and advanced signal processing to further eliminate noise, multipath and interference. In addition, new services such as Open Service Navigation Message Authentication (OS-NMA) within Galileo will be operational in 2021. This will enhance protection against spoofing for any critical application. The state of the industry will be presented in this paper as it exists today and projected out into the next few years.
Published in:	Proceedings of the 51st Annual Precise Time and Time Interval Systems and Applications Meeting January 21 - 24, 2020 Hyatt Regency Mission Bay San Diego, California
Pages:	234 - 240
Cite this article:	Fischer, John, "Resilient Timekeeping for Critical Infrastructure," Proceedings of the 51st Annual Precise Time and Time Interval Systems and Applications Meeting, San Diego, California, January 2020, pp. 234-240. https://doi.org/10.33012/2020.17303
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