The problem is that, although these GNSS jammers or PPDs (Personal Privacy Devices) are low power, GNSS signals are even lower power.One PPD powered by a 12 V car cigarette lighter socket is powerful enough to knock out GNSS signals in a radius of several hundred metres. With the increasing use of GPS trackers for insurance or road tolling, the number of jamming incidents has increased significantly in recent years.
A report from the Homeland Infrastructure Threat and Risk Analysis Center (HITRAC) of the Department of Homeland Security (DHS) documented the case at Newark Liberty Airport in 2011 where a PPD caused harmful interference on the new GPS-based landing assistance system. Subsequent monitoring has since confirmed an average of 5 interference events per day. According to the report, PPDs are considered to be among the 3 biggest threats for GPS/GNSS disruption.
GNSS is more than positioning
GNSS applications have long surpassed positioning. GNSS has established itself as part of the critical infrastructure in areas as diverse as cellular communication, where providers use GPS time to manage communications between mobiles phone and phone towers, to banks and stock markets who use GPS to time-stamp their transactions to help prevent fraud.
The effect of Personal Privacy Devices on GNSS signals
Most cheap in-car PPDs transmit a chirp signal which is a signal that changes frequency rapidly over time. In this way, a signal with a rather narrow bandwidth can cover large swathes of the GNSS spectrum. Figure 2 shows the effect of the signal from a chirp jammer on the GPS L1 band. The region between 1565 and 1585 MHz is dominated by the jammer effectively swamping the GPS L1 signal.
The Septentrio solution against GPS/GNSS jamming and spoofing
The intermittent nature of most jamming events makes them difficult to detect and even more difficult to diagnose. That’s why Septentrio offers built-in protection against intentional and unintentional jamming in its GNSS receivers. As part of our patented Advanced Interference Mitigation (AIM+) technology, a sophisticated system of sampling and mitigation mechanisms has been developed called WIMU (Wideband Interference Mitigation). The red trace in Figure 2 shows the dramatic result when activating WIMU in the presence of interference from a chirp jammer. More details on WIMU can be found here.
The benefit to the user
The effects of WIMU are also illustrated in the Figures below. The white triangle indicates the location of a 10 mW chirp jammer in the centre of Tampa and the red zone is the region in which the jammer knocks out the GNSS signal. When WIMU is enabled on a Septentrio receiver for example, the ‘No RTK Zone’ indicated by the red region, is reduced from several hundred metresto a few metreseffectively confining the range of the jammer to inside the car it’s plugged into.
Uptime guaranteed
AIM+ technology brings considerable cost benefits to users of Septentrio’s GNSS solutions. Whether in urban or rural locations, on construction sites or piloting a UAS, the detrimental effects of PPDs and other sources of jamming can be considerably minimised thus reducing downtime and costs due to lost man hours.
AIM+ is available on all current Septentrio GPS/ GNSS solutions.
Jamming of GNSS signals is illegal in most countries. If you suspect that jamming is an issue in the area where you work, please report it to the local law enforcement authority.
Related webinar
GNSS hacking, from satellite signals to hardware/software cybersecurity
Related brochure
Everything you need to know about radiofrequency interference (RFI) on GNSS/GPS signals
GPS spoofing - all you need to know how to protect your receiver
