Jamming and anti-jamming technologies have become an important research topic within the GNSS discipline. While many GNSS receivers leave large space for signal dynamics, enough power space is left for the GNSS signals to be jammed. The goal of jamming is adding a noise to the satellite signal and fooling the receiver not to use signals plus noise for positioning calculations. The goal of spoo ng is a falsi cation of the satellite signal and fooling the receiver to generate a false position; thus, misleading the navigator. This article discusses the experimental approach to anti-jamming and anti-spoo ng based on the shielding of the antennas from the jammers and spoofers signals to develop an algorithm for the built-in protection system. In experimental studies, we used two types of screens: the metal funnel and the system of metallic concentric rings on a metal substrate. We also brie y consider the commercial civilian and military jammers. The presented algorithm enables the development of an integrated vehicle safety system.
Satellite based positioning provides the world's most precise location information. It is possible to acquire positioning anywhere in the world where the GNSS satellite signals are available any time of day at data rates up to 100 Hz. Raging currents, rugged coastlines, narrow passageways, and high winds all contribute to making marine environments some of the most challenging navigation conditions in the world. Modern GNSS receivers, antennas, and post-processing software provide precise, accurate, and reliable positioning measurements for a wide range of marine applications.
Ability and quality of measuring and monitoring the GNSS signals are
critical to assessing GNSS system usability and performance. The GNSS receiver
technology relies on signals broadcast from satellites orbiting 20 000 km above
the Earth at a frequency of approximately -163 dBW or about the strength of a
single Christmas tree bulb. This makes GNSS signals susceptible to interference
from many sources [
Jamming is a purposeful creation of active interference to reduce the signal/noise ratio of the GNSS satellite signals. Usually, it is a part of electronic warfare. Jamming may be targeted to all or some recipients of the signal. The device for silencing is called the jammer.
Generally, purpose of jamming is to prevent the useful information or a signal receiver or, at least, creating inconvenience to him. As the object of jamming can be any receiver insu ciently protected from external in uences signals: radio, radar beacon, the wireless network, the mobile phone (or base station), etc. Jamming can be used in actual combat conditions and in the cases of the information war, or even competitive telecommunications companies or broadcast, to make completely disable the security system or to transfer it to the unservice mode.
Development Unmanned Vehicle (UV) caused developing the special-purpose
technologies both for military and dual-use applications. And it is not only the
traditional system of military intelligence, but, also, rapidly developing
electronic warfare systems including mobile systems of noise suppression radar and
radio navigation systems (jamming) [
For positioning unmanned vehicles (UV), the GNSS and Inertial Navigation
System (INS) [
Emphasize the importance of UV as a means of electronic warfare, i.e., media jammers and/or spoofers of the GNSS. In this case, the radar will observe hundreds of decoys and the GNSS-receiver will be switched from real signals of the GNSS to false ones. 3
The availability and usage of low-cost GNSS jamming devices has resulted in the increased threat of intentional and unintentional disruption of commercial and industrial systems that rely on precise GNSS data. The basic scheme of jamming is shown in Fig. 1.
It is well known that the use of directional antennas weaken the jammer signal, and, in some cases, it is blocked to 100%. You can use a metal funnel to change the directionality of antenna. The main scenario of the GNSS jamming using a funnel is shown in Fig. 2. A vehicle during normal operation carries tra c using the GNSS. The minimal elevation angle min is known for satellite above the horizon at which the antenna can \see" the satellites.
The terrorist located at a distance from vehicle broadcasts to the vehicle a high power radio noise or a fake signals from the spoofer and suppresses a mode of the normal operation using GNSS. The maximal elevation angle max of the jammer above the horizon at which the antenna \does not see" the jammer (Fig. 2).
In most practical situations funnel (angle ) you can select as
, so the main parameter of shielding type = ( + )=2. 5
To test the e ectiveness of shielding type funnel, we performed experimental studies. The funnel was made from an aluminum sheet of diameter 300 mm and height 86.6 mm (Fig. 3). The elevation of jammer changed from 0 to a value at which jammer \drowned" normal browser operation. The experiment showed that this angle is almost coincided with the main parameter of funnel-shieldede one (angle ) equal 30 .
As described in point 4, that the use of directional antennas weaken the jammer
signal, and, in some cases, it is blocked to 100%. You can use a system of metallic
concentric rings on a metal substrate to change the directionality of the antenna.
A vehicle during normal operation carries tra c using the GNSS. The antenna
Y can \see" all satellites. Terrorist located at a distance from vehicle broadcasts
to the vehicle a high power radio noise or a fake signals from the spoofer and
suppresses a mode of the normal operation using GNSS (Fig. 4). Details related
to di raction of electromagnetic wave from a jammer was described in detail in
[
In real experiments, we used ve metallic concentric rings (Fig. 5). To test the e ectiveness of shielding with help of metallic concentric rings, we performed experimental studies. A jammer was used as a source of electromagnetic radiation.
The purpose of this experiment was to nd out the minimum distance along the X axis, from which it would be possible to receive the GNSS signal using a jammer and a screen shield. The distance was systematically increased every 10 cm between the GNSS receiver and the jammer until the satellite signal was received by the GNSS antenna Y , as shown in Fig. 6.
When the jammer was as close to the screen as possible, the antenna received the noise from the jammer. Then, the jammer was moved in the direction x until the receiver captured genuine GNSS signals with the help of the antenna Y . The result of the experiment is R = 3:6 m.
X, 2 f15 ; 10 ; 5 ; 0 ; 5 ; 10 ; 15 g
The purpose of the next experiment was to determine how the relative height of the jammer a ected the receivers reception despite the use of the screen. As in the previous experiment, the distance was systematically increased by 10 cm each time, but at di erent height levels between the GNSS receiver and the jammer until the satellite signal was received by GNSS antenna Y , as shown in Fig. 7.
When the jammer was as close to the screen as possible, the antenna received the noise from the jammer. The jammer was then moved in the direction (x) at the angle to the axis X, 2 f15 ; 10 ; 5 ; 0 ; 5 ; 10 ; 15 g until the receiver captured the GNSS signals again with the help of the antenna Y . The results of the experiment are shown in Table 1. 8
There are a few civilians that use jamming GNSS signals, mostly privacy related,
including the ability to conceal oneself or one's vehicle, in the case, when it is
being tracked by a GNSS receiver. A practical application would be a
salesperson or delivery driver that may wish to lunch outside their territory or return
home for a forgotten item without having to do a lot of explaining due to the
GNSS tracking on their vehicle. The range of the most civilian GNSS jammers is
su cient to cover even the largest of vehicles giving the user a cloak of privacy
[
For car, truck, bus, van, or even boat security, stopping the GNSS tracking
signals is provided by simply plugging the jammer into any cigarette lighter or
vehicle power outlet of 12V. With up to 10 meter coverage, it will protect you
from being detected. It will automatically protect you by blocking any GNSS
signals that are being sent to track you inside and outside your vehicle. This
tracking jammer is a popular item with sales personnel, truckers, and delivery
drivers, who wish to take lunch or make a personal stop outside of their territory
or route \o the radar" [
The PRO model secures the area and prevents both cell phone and GNSS application with the most popular combination of the cell phone and GNSS units. This high powered handheld PRO model features a built-in fan to keep the unit cool during extended periods of use, as well as switch selectable settings; so, you can choose which channels to block. The PRO creates a protected zone around you, your vehicle, or your meeting by blocking cellular and/or GNSS signals at a distance of up to 25 meters (under best conditions). The indicator lights on top of the unit con rm which bands are actively being inhibited, and the durable rubber coated antennas will not be brken with rugged use. 8.3
This model provides secure area coverage and prevents both cell phone and GNSS application with our highest powered handheld. This model features a built-in fan to keep the unit cool during extended periods of use, as well as switch selectable settings; so, one can choose, which channels to block.
Jamming: 700{800 MHz (4G) 850{965 MHz (GSM) 2400{2500 MHz 2500{2700 MHz 2100{2170 MHz (3G) 1800{1990 MHz (PCS)
GNSS L1 GNSS L2 9
In the world, there are many di erent versions of Military GNSS jammers. Here,
we give as an example the station Autobase-M 1L222M (Fig. 8), which may
operate in a mode jammer. The 1L222M \Autobase-M" complex is the
executive radio-technical reconnaissance (EW) mobile complex component with the
jamming stations SPN-2/SPN-4 [