On Feb. 19, the Finnish government submitted a legislative proposal to parliament to criminalize possession and import of radio-frequency jammers and spoofers, including those blocking GNSS signals
According to Ministry of Transportation and Communications, the amendments would be made to the Act on Electronic Communications Services. The government proposes to amend the provisions on equipment that jam or spoof radio communications.
Unauthorized use of jammers is already banned. The government proposes to criminalize unauthorized possession of jammers, enabling confiscation and improving the authorities’ ability to intervene in the unauthorized possession and import of such devices. The proposal would introduce a distinct definition for jammers, separate from radio equipment, allowing for stricter regulation.
The amendment would set clearer conditions for the use and possession of jammers for the authorities and other authorized parties. The possession and use of jammers for research and product development would be permitted under a license if certain conditions are met.
The proposal would also introduce exceptions for NATO and its member states regarding the right of the Finnish Transport and Communications Agency (Traficom) to check radio equipment or jammers and confiscate them for inspection.
Parliament will first hold a debate on the government proposal in a plenary session. The proposal will then proceed to a committee reading. Following the committee report, the debate will continue in a plenary session.
The Act is scheduled to enter into force on July 1.
Charles Curry, founder of Chronos Technology, with the RIN award. (Photo: Chronos)
Chronos Technology has been recognized by the Royal Institute of Navigation (RIN) with its 2018 Duke of Edinburgh’s Navigation Award for Outstanding Technical Achievement in “recognition of technical excellence and authority in satellite navigation and timing vulnerabilities and mitigations.”
Charles Curry, founder and managing director of Chronos Technology, accepted the award at the RIN Annual General Meeting held June 10 in London.
Chronos has worked with the RIN and others since 2008 to raise awareness of GNSS vulnerabilities, and in collaboration with the University of Bath has developed a family of GNSS interference detection products.
Chronos first started researching this phenomenon with the University of Bath in the Innovate U.K. project GAARDIAN in 2008, closely followed by the SENTINEL and AJR projects. The projects have focused on detecting and locating commercial off-the-shelf jammers mostly sourced from Chinese websites.
The first success was seizing the so called “Girvan Jammer” in 2011, when a jammer was recovered from a commercial van driver through collaboration with the serious and organized crime group of the local police.
This exercise took about two weeks from initial detection to recovery of the jammer and should be compared to the six months it took U.S. enforcement agencies to identify the so called “Newark Jammer.”
SENTINEL sensors were originally rolled out in 2010 continue to provide real evidence of jamming at various locations around the U.K. The project assists police work by collating jamming events by day and time of day using a cloud-based portal.
The GPS interference detection portfolio includes low-cost, handheld GNSS interference detectors with features such as data logging and direction finding capabilities to precisely pinpoint a jammer.
The latest product to emerge is known as “JammerCam,” and is the first GPS jamming detector in the world to be able to take photographs of a moving vehicle, which is carrying a GPS jammer. This is now in trials with various local police forces and is photographing vehicles with jammers on a daily basis, providing real-time actionable intelligence to the law enforcement officers’ smartphones identifying vehicle type, color and number plate.
Early trials with this research are leading to the seizing of at least one jammer per week by U.K. law enforcement agencies.
Chronos has demonstrated the ability to work with universities and potential users to develop new, affordable products to meet a genuine need. Customers include U.K. and international law enforcement agencies and military users.
“This is a very prestigious award, as a look at the previous winners will attest,” said John Pottle, director of the Royal Institute of Navigation. “Chronos is very well respected and has continued to innovate, achieving global influence from their U.K. base. Many congratulations to all at Chronos for this well-deserved recognition.”
Curry was awarded Fellowship of the Royal Institute of Navigation in 2016 in recognition of his significant and continuing contribution to the practical aspects of time measurement and dissemination, including research into GNSS vulnerabilities and the use of eLoran for precise time.
“Chronos is honored to be the recipient of the RIN’s 2018 Duke of Edinburgh’s Navigation Award for Outstanding Technical Achievement,” Curry said. “We could not have done this without our close association with the University of Bath, in particular Dr. Robert Watson and Professor Cathryn Mitchell and their colleagues in the Electrical & Electronic Faculty.
Over the years, this association has enabled Chronos to undertake research and bring to the market GPS jamming detection products which have been thoroughly field tested at locations such as Sennybridge in the Brecon Beacons, and other international jamming trials in Norway and the U.S.
“In particular, Chronos was the only British company to be invited to JamX17 in Idaho Falls, U.S., by the U.S. Department of Homeland Security to showcase the detectors’ technology,” Curry said.
When subjected to very strong interference, a GNSS receiver can be totally blinded and stop working. This is often the scope of intentional jammers. However, in a number of cases the presence of interference is severe enough to significantly decrease receiver performance, but not so much as to make the receiver lose its lock on the satellite signals or blind the acquisition of the satellite signals.
Such intermediate power values turn out to be the most dangerous cases, because sometimes they cannot be detected, but lead to a worsening of the positioning performance. The accuracy of the position solution depends on, among others, the quality of the pseudorange measurements and/or the phase measurements. Thus, when radio-frequency interference (RFI) degrades the pseudorange and phase measurements or induces cycle slips on the phase measurements, the accuracy of the position solution will decrease.
Impact on the Front End
The front-end filters the incoming signal, demodulating it to the chosen intermediate frequency before performing the analog-to-digital conversion (ADC).We must consider the presence in the front end of the adjustable gain control (AGC) between the analog portion of the front end and the ADC. When the GNSS band is interference-free, AGC gain depends almost exclusively on thermal noise, since the received signal power is below that of the thermal noise floor. When in-band interference is present, the AGC will squeeze the incoming signal to match the maximum dynamics of the ADC, causing a reduction of the amplitude of the useful signal, which may be lost. This may typically happen in the presence of some kind of wide-band interference (WBI) spread over a bandwidth larger than the passband of the front-end filter.
With narrow-band (NBI) or continuous-wave interference (CWI), statistics of the digital signal at the ADC output are also affected. In this case the AGC can still compress the input signal to avoid a stronger saturation, but the following receiver stages will have to deal with a GNSS contribution quantized only on lower levels.
In the presence of stronger interference, even the other components of the front end (filters and amplifiers) may be led to work outside of their nominal regions, generating nonlinear effects or clipping phenomena (in which the signal amplitude exceeds the hardware’s capability to treat them). In both cases, spurious harmonics are generated and mixed with the useful signal in the front end itself.
Impact on the Acquisition Stage
If the interference is not driving the AGC/ADC to full saturation, the acquisition module is still able to perform its task, processing the interfered signal to estimate the code phase and the Doppler shift with respect to the local code. The correlation with the local code can be seen as a spreading operation followed by a filter.
Figure 1. GPS L1 C/A acquisition search space in (a) an interference-free environment and in the presence of (b) –140 dBW in-band CWI; (c) –135 DBW in-band CWI; (d) –130 dBW in-band DWI.
Figure 1 showsthe acquisition search space for different levels of theinterfering power of a CWI from –140 to –130 dBW compared to the interference-free case. The search spaces depicted for the four scenarios are achieved using 1 ms of coherent integration time and three non-coherent accumulations, and the peak-to-noise-floor separation defined as
is considered as a figure of merit. The value of αmean decreases as the interfering power increases, thus increasing the probability of a false alarm. With the increasing power of the CWI, a modulation effect in the search space floor in the Doppler domain dimension can be observed. Such an effect is mainly determined by the new harmonics components generated by the multiplication between the locally generated carrier and received CWI. Such an effect also depends on how the interfering signal and the useful GNSS signal are combined at the entrance to the acquisition block, which in turn depends on the random variables φ0 and θint.
In the presence of WBI, a different effect is observed in the acquisition search space. Considering a band-limited Gaussian white noise spread all over the GNSS useful filtered signal components, the effect on the CAF envelop is an increase in the noise floor. This increases the search space noise floor. The presence of additive band-limited noise causes a uniform increase in the noise floor tin the search space that might mask the correct correlation peak and thus fool the acquisition process.
Impact on the Tracking Stage
Interference impact on the tracking stage has a direct consequence on the quality of the measured pseudorange. Harmful interfering signals increase the variance of the time-of-arrival (TOA) estimate by the discriminator and modify the shape of the S-curve of the code discriminator, thus creating in some cases a bias in the measurements.
Figure 2 depicts outputs of the early-prompt-late correlators. In the presence of in-band CWI and of NBI, the interference is injected 9.3 seconds after the beginning of the tracking stage where the receiver is correctly locked on the received signal. A CWI, shifted 200 kHz with respect to the signal intermediate frequency (in correspondence with a C/A code spectrum line), increases the noise at the correlators outputs and leads to harmonic behavior of the early-prompt-late correlator outputs.
Figure 2. GPS L1 C/A code tracing error comparison: coherent and non-coherent early-late processing (CELP and NELP).
NBI increases the variance of the correlators’ outputs; this directly increases the pseudorange error and the noise on the receiver phase measurements. Additive band-limited noise leads to an overall increase in the carrier phase discriminator output variance over the 3σ threshold, which for a PLL two-quadrant arctangent discriminator is 45 degrees. When in presence of strong CWI, a sudden jump of the phase discriminator output is detected as soon as the CWI is injected onto the received signal.
Impact on the Estimated Signal-to-Noise Ratio
Sticking to the definition of C/N0 as the ratio between the received power and the power spectral density due to thermal noise at the input of the receiver, the presence of interference should not change the value, since the thermal noise is not increasing. However, the C/N0 value provided by the receivers is estimated on the basis of the correlator outputs at the tracking stage. For this reason the estimation is affected by the presence of the additional (nonthermal) noise generated by the interference. The variation of the C/N0 can also be used as observable for interference (or other threats) detection.
Chapters: The Interference Threat; Classification of Interfering Sources and Analysis of the Effects on GNSS Receivers; The Spoofing Menace; Analytical Assessment of Interference on GNSS Signals; Interference Detection Strategies; Classical Digital Signal Processing Countermeasures to Interference in GNSS; Interference Mitigation Based on Transformed Domain Techniques; Antispoofing Techniques for GNSS. The book is intended for members of the engineering/scientific community with pre-existing knowledge of satellite navigation principles and GNSS.
FabIo Dovis holds a Ph.D. in elecronics and communications engineering from Politecnico di Torino, Italy, where he is an associate professor.
Washington, D.C. — The Federal Communications Commission’s Enforcement Bureau today launched a dedicated jammer tip line – 1-855-55-NOJAM (or 1-855-556-6526) – to make it easier for the public to report the use or sale of illegal GPS, cell phone or other signal jammers. It is against the law for consumers to use, import, advertise, sell or ship a GPS or cell jammer or any other type of device that blocks, jams or interferes with authorized communications, whether on private or public property.
The FCC asks people to call the toll-free Jammer Tip Line immediately if:
you are aware of the ongoing use of a cell, GPS, or other signal jammer;
your employer operates a jammer in your workplace;
you observe a jammer in operation at your school or college;
you observe an advertisement for a jammer at a local store; or
you observe a jammer being operated on your local bus, train or other mass transit system.
“We need consumers to be our eyes and ears. Jammers do not just weed out noisy or annoying conversations and disable unwanted GPS tracking, they can prevent 9-1-1 and other emergency phone calls from getting through in a time of need,” Michele Ellison, chief of the Enforcement Bureau, said.
Calls to the Jammer Tip Line will be handled by experienced Enforcement Bureau staff. Callers are encouraged to provide as much detail as possible, including the time and location of the incident, a description of the jamming device (if available), and the name and contact information of the individual or business using or selling the device.
While callers may remain anonymous, the bureau urges callers to provide a contact phone number in case additional information is needed. “Every tip can make a difference,” Ellison said. “While our agents are actively pursuing these violations online and on the street, you can help. We encourage concerned parents, commuters, employees, and anyone else with credible information to tip us off. Working together, we can stop the spread of illegal jammers.
For more information, Frequently Asked Questions about cell, GPS, and Wi-Fi jammers are available at www.fcc.gov/jammers, or email [email protected].
