Tips and Tricks to Finding GNSS Jammers – A Field Story

Darren McCarthy, Logan Scott, Alex Tkatch

Abstract:	GNSS Jammers and Personal Privacy Devices (PPDs) pose a significant threat to our continued reliance on GNSS signals. The use of these illegal devices has been documented in high profile cases, but how prevalent is the use of such devices and what signals to these devices emit? Quantifying the potential threats can help assess the risk to GNSS receivers, but the collection of the RF signal is necessary to understand the impact to the receiver design. If a database of expected threat signals existed, GNSS receivers could be designed to improve their immunity. Reducing the susceptibility of GNSS receivers requires knowledge of how these PPD devices operate and where they can be expected. With the current proliferation and availability of PPD devices on the internet and illegal channels, it is also important to continue to reassess real-world threats as PPD devices evolve to avoid detection and tracking. While the operation of such devices is illegal, one method to collect signals is to finding them in the field and record the signals. Capturing events in the field and replaying them back in the lab with duplicated results can be the first step to building a database of signal threats that can ultimately improve GNSS receiver designs. The methodology used for this field study was to outfit equipment in a mobile platform. A high-fidelity monitoring receiver was used to give a visual interpretation of the real-time environment while looking at the statistical spectrum persistency, spectrum power vs time, and spectrum vs time. Concurrent with the monitoring receiver, a separate dedicated recording receiver was linked to the GNSS receiver to record the RF spectrum, metadata, and live feedback on a GNSS test receiver performance. A key to a successful intercept of the GNSS Jammers was to begin the studies in an area of low speed traffic where individual suspect vehicles could be easily identified. This study looks at the practical implications of collecting records of GNSS jammers in the field with the intention of being able to duplicate the field results back in the lab. The places of interest to look for the potential threats and the practical considerations on to the mobility of the threat signals and the collection system will be discussed. This study will also discuss the results to date and lessons learn on the identification of GNSS Jamming devices, hints on the identification of false targets, tips on how to collect viable recordings, and the technical aspects of a record and replay systems to produce representative results of the threats logged in the field. Triggering, isolating, capturing, and identifying the multitude of legal and illegal signals in the GNSS bands has yielded some unexpected results with regards to the number of unintentional and intentional signals. These results of these events have not yet been widely reported or documented in open literature. Real-life tracking results will be discussed and the implications on potential receiver designs and reliable tracking methods.
Published in:	Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014) September 8 - 12, 2014 Tampa Convention Center Tampa, Florida
Pages:	372 - 391
Cite this article:	McCarthy, Darren, Scott, Logan, Tkatch, Alex, "Tips and Tricks to Finding GNSS Jammers – A Field Story," Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014), Tampa, Florida, September 2014, pp. 372-391.
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