GPS Anti-Jamming uses power minimization to reduce the effect of interference and jamming so that the GPS receiver can continue to operate correctly. GPS technology has revolutionized modern warfare.
Military organizations regularly depend on satellite technology for accurate positioning, timing and communications.
Radar jamming and deception
But GPS signals received on Earth are weak and susceptible to interference and intentional jamming. Indeed, the signals are usually obscured by thermal noise and only observable with a tuned signal analyser - in other words a GPS receiver. A simple low power jammer, readily available via the World Wide Web, can overpower GPS signals within a large area, denying a position solution and timing.
GPS anti-jam technology is quickly evolving. Until recently, size and cost considerations meant anti-jam systems were only feasible for expensive assets, such as strategic aircraft and capital ships. NovAtel's approach to the problem is to build a range of compact and affordable anti-jam systems for land, sea, air including unmanned aerial systemsand fixed installations.
GAJT is a null-forming system that preserves the antenna's view of the GPS satellites while ignoring jammers, ensuring the satellite signals required to compute precise position remain available. The GAJT range of products provides anti-jam performance at a significantly lower cost than others and is available off-the-shelf for rapid deployment.
Of course, the performance is scenario-dependent but this means effectively that you can operate safely times close to a jammer than without protection. The whole system performance is the sum of GAJT interference suppression plus that provided by the installed receiver itself.
Please click here to view. Overview Related Products. Do not show this message again.This project deals with anti-jamming techniques for wireless radio transmissions and wireless networks.
We explore ways to detect, prevent, and counteract signal jamming attacks in which a third party transmits targeted jamming signals that disrupt wireless communications between nodes. We made the following proposals for jamming resistance; further information and related publications are given below:. Signal and Message Manipulations: Investigation of signal and message manipulations on the wireless channel. Detection of Reactive Jamming in Sensor Networks: Detection of reactive jamming based on identification of the cause of bit errors during transmission.
Uncoordinated Frequency Hopping: Key Establishment over a wireless channel in the presence of a communication jammer. This work explores the possibilities of the attacker to tamper with the integrity of messages and signals on the wireless channel. We explore the suitability of Dolev-Yao-based attacker models for the security analysis of wireless communication. The Dolev-Yao model is commonly used for wireline and wireless networks.
It is defined on abstract messages exchanged between entities and includes arbitrary, real-time modification of messages by the attacker. In this work, we aim at understanding and evaluating the conditions under which these real-time, covert low-energy signal modifications can be successful. In particular, we focus on the following signal and message manipulation techniques: symbol flipping and signal annihilation.
We analyze these techniques theoretically, by simulations, and experiments and show their feasibility for particular wireless channels and scenarios. An integral part of most security- and safety-critical applications is a dependable and timely alarm notification.
However, owing to the resource constraints of wireless sensor nodes i. With current alarm forwarding schemes, blocking of an alarm by jamming is straightforward and jamming is very likely to remain unnoticed. In this work, we propose a novel jamming detection scheme as a solution to this problem. Our scheme is able to identify the cause of bit errors for individual packets by looking at the received signal strength during the reception of these bits and is well-suited for the protection of reactive alarm systems with very low network traffic.
We present three different techniques for the identication of bit errors based on: predetermined knowledge, error correcting codes, and limited node wiring. We perform a detailed evaluation of the proposed solution and validate our findings experimentally with Chipcon CC and CC radios. The results show that our solution effectively detects sophisticated jamming attacks that cannot be detected with existing techniques and enables the formation of robust sensor networks for dependable delivery of alarm noti cations.
Our scheme also meets the high demands on the energy efficiency of reactive surveillance applications as it can operate without introducing additional wireless network traffic. Jamming-resistant communication is crucial for safety-critical applications such as emergency alert broadcasts or the dissemination of navigation signals in adversarial settings.Integrated power solutions from GPS is a key battlefield enabler, allowing precise location of military assets in a real-time environment; however, it is relatively easy to disrupt the GPS signal due to its extremely low power level.
In battlefield and airborne operations, enemy countermeasures include the use of GPS denial effects, to disrupt and jam GPS. Department of Defense and more than 20 other nations. Raytheon UK has designed and manufactured in excess of 10, GPS anti-jam units for the worldwide market.Resilience communication with anti jamming techniques
Learn more about our products:. This cost-effective, small form factor and lightweight upgrade will simply replace existing unprotected GPS antennas, as well as enhance original installations where protection against jamming and interference is required. These fully integrated GPS-AJ antennas are suitable for military, critical national infrastructure, maritime, government and avionics where low Size, Weight and Power constraints are key.
The system delivers proven GPS anti-jam performance in harsh airborne and maritime environments as well as complex high-threat solutions.
Performance Benefits:. GAS-1 technology consists of a multi-element Controlled Reception Pattern Antenna CRPA and separate Antenna Electronics AE unit which is able to recognise multiple sources of deliberate jamming and other electrical interference — such as mobile phone networks, satellite communications and High Definition terrestrial TV — and reject them.
This allows the navigation equipment to function safely, accurately and efficiently in the presence of multiple jammers. In military use, jammer-protected targets can be approached more closely and all operations requiring GPS-derived position and time UTC can be carried out with greater accuracy and improved mission assurance.
It is the ability of GAS-1 to track jammers and generate nulls faster than any of its competitors that has seen it selected by the air forces of the United Kingdom, United States and Australia governments. When configured with a multi-element Controlled Reception Pattern Antenna CRPAthe AGR's post-correlation nulling techniques allow continued satellite track in the presence of high levels of hostile jamming.
By clicking, you agree to our privacy notice. GPS Anti-Jam Systems Integrated power solutions from GPS is a key battlefield enabler, allowing precise location of military assets in a real-time environment; however, it is relatively easy to disrupt the GPS signal due to its extremely low power level. It provides the user with an indication of the presence of jamming and its power; this information can be fed back into the tactical and strategic real-time awareness picture. Share Content.Discussions of signal jamming were once largely confined to electronic warfare forums.
But with the rise of autonomous vehicle technology, jamming has become a mainstream topic. It now pays to know a few basics about both the test setups necessary to gauge resistance to jamming techniques and the principles of signal propagation. Many of the sophisticated advances in signal jamming arose from work with radar. So it is useful to start with a review of a few radar fundamentals. The idea of radar, of course, is that a target reflects some of the energy of a transmitted signal.
The returned energy is received and processed to detect the target and extract its location and relative velocity. The direction of arrival of the returned signal can also reveal the angular position of the target if the original antenna beam is narrow enough. And if there is relative motion between the target and radar, the shift in the carrier frequency of the reflected wave i.
Typical radar transmitters emit signals in the form of pulses. And the pulses generally have a low duty cycle where the duty cycle is the ratio of pulse duration over a pulse period. Moreover, the resolution of radar and for that matter, lidar is limited by the pulse width. Chirp radar typically generates a signal by mixing a carrier from a stable local oscillator STALO with a pulse that has been chirped. The receiver mixes signals it receives with the STALO and runs them through a correlation filter before sending the result to a detector that uses a coherent oscillator COHO for generating I and Q components that in turn feed to a signal processor.
A chirp is a signal whose frequency rises or falls with time. There are several kinds of chirps — linear, nonlinear, exponential, etc. Some systems also emit a compressed pulse in the interest of reducing transmitter power and the possibility of interception.
All in all, the subject becomes complex quickly. Thus a chirp radar includes stages that modulate the transmitted pulse, transmit it, receive the echo, and then correlate the received signal with the transmitted pulse. There is a potential ambiguity when energy returns from a distant target after the radar has already emitted a second pulse. This is called a second-time-around echo. To measure far-away objects unambiguously, the radar must wait for their pulses to return.
However, the fastest object the radar can unambiguously measure is determined by the emitted pulse rate, i. To measure the speed of fast objects, the PRF must be high, hence there is a tradeoff between radar range and speed detection. A point to note is that a radar jammer often has a range advantage over the radar it targets.
With these points in mind, consider the various types of radar jamming methods as defined in electronic warfare. Barrage jammers attempt to overwhelm the radar receiver with an interfering signal in the received frequency band.
Noise jammers modulate the jamming signal with AM or phase noise. Deceptive jammers use either a repeater or a memory to produce a replica of a radar return with appropriate modifications in time or frequency.Villard, Professor Emeritus of Stanford, founding father of SRI Inc, and one of the most wonderful colleagues with which it has been my sheer pleasure to be associated.
Mike had been asked by the Chief of U. His mind set to work: he made a pile of different antennas that seemed to show some promise, and presented a proposal to USIA to produce two different anti-jam antennas that would be effective.
I was at VOA engineering. Mike showed me myriad designs that filled his pool house to the max! We selected two promising ones, and spent the rest of the year studying them, improving them, and producing a really neat end product. One counters jamming via sky wave, where the jammer propagates by ordinary HF propagation. The other counters ground wave jammers — noise transmitters located near the receiver, usually on the outskirts of the city being jammed.
Ground wave jamming is exactly similar to arcing power lines or other locally produced noise from appliances and the like — even from lightning. Lay it on the base, with its edge along the edge of the base. Fold the foil over itself as shown. Use tabs of scotch tape to hold the foil in place. Continue taping it down on three, and part of the fourth, side:.
You can use saran wrap, waxed paper, or lots of other thin, insulated material for this — even a handkerchief! But thick insulation could prevent tuning the antenna to low HF frequencies. Put the insulating sheet over the first part of the foil and tape it in place, per the drawing. Leave the fifth flap of foil loose, so it can be lifted up when necessary. Cut off excess foil so it does not short circuit against the foil beneath the newspaper.
When using a battery-operated, pocket size shortwave receiver, set the antenna on a table, couch, bed, or on the floor. Keep it hoizontal. Put the receiver on the foil as shown.
Pull the whip antenna out, and lay it on the other side of the foil loop. Use a small weight to make sure the whip contacts the foil. Use a book to press the loose foil flap down against the newspaper. Pull excess foil up and back over the book.Wireless networks are meant for transferring information of any kind between two or more points that are not physically connected.
Wireless networks are vulnerable to various kinds of attacks because of its shared medium. There is need to deal with numerous security issues. Attackers with a transceiver can be able to hinder wireless transmission, insert unwanted messages, or jam messages of high importance. Jamming can be considered as one of a fundamental way of degrading network performance.
In the simplest form of jamming, the adversary corrupts the content of the original message by transmitting radio frequency signals in the network or by blocking the message so that it cannot reach to the intended receiver. Radio interference attacks cannot be easily addressed by conventional security methods. An adversary can simply disregard the medium access protocol and continually transmit on Wireless networks.
Typically, jamming can be done in two forms. One is external threat model in which jammer will not be the part of the network. Another one is internal threat model in which jammer will be part of the network. Jamming makes use of intentional radio interferences to harm wireless communications by keeping communicating medium busy, causing a transmitter to back-off whenever it senses busy wireless medium or corrupted signal received at receivers.
Jamming mostly targets attacks at the physical layer but sometimes cross-layer attacks are possible too. In this section, we elaborate on various types of jammers and the placement of jammers to maximize the jammed area. Blocking of the wireless channel due to interference noise or collision at the receiver end. Jammers are malicious wireless nodes planted by an attacker to cause intentional interference in a wireless network.
Depending upon the attack strategy, a jammer can either have the same or different capabilities from legitimate nodes in the network which they are attacking.
The jamming effect of a jammer depends on its radio transmitter power, location and influence on the network or the targeted node.
A jammer may jam a network in various ways to make the jamming as effective as possible. Basically, a jammer can be either elementary or advanced depending upon its functionality. For the elementary jammers, we divided them into two subgroups: proactive and reactive. The advanced ones are also classified into two sub-types: function-specific and smart-hybrid.
The detailed classification of different jammers can be found in Fig. Proactive jammer — Proactive jammer transmits jamming interfering signals whether or not there is data communication in a network.
Basics of signal jamming
It sends packets or random bits on the channel it is operating on, putting all the others nodes on that channel in non-operating modes. However, it does not switch channels and operates on only one channel until its energy is exhausted. There are three basic types of proactive jammers: constant, deceptive and random. From here on, whenever we use proactive jammers it can mean all these three. Constant jammer emits continuous, random bits without following the CSMA protocol.
According to the CSMA mechanism, a legitimate node has to sense the status of the wireless medium before transmitting. If the channel is found busy during the DIFS interval, the station should defer its transmission. A constant jammer prevents legitimate nodes from communicating with each other by causing the wireless media to be constantly busy.
This type of attack is energy inefficient and easy to detect but is very easy to launch and can damage network communications to the point that no one can communicate at any time. Deceptive jammer continuously transmits regular packets instead of emitting random bits as in constant jammer. It deceives other nodes to believe that a legitimate transmission is taking place so that they remain in receiving states until the jammer is turned off or dies.
Compared to a constant jammer, it is more difficult to detect a deceptive jammer because it transmits legitimate packets instead of random bits.
Similar to the constant jammer, the deceptive jammer is also energy inefficient due to the continuous transmission but is very easily implemented. Random jammer intermittently transmits either random bits or regular packets into networks.Radar jamming and deception is a form of electronic countermeasures that intentionally sends out radio frequency signals to interfere with the operation of radar by saturating its receiver with noise or false information.
Concepts that blanket the radar with signals so its display cannot be read are normally known as jammingwhile systems that produce confusing or contradictory signals are known as deceptionbut it is also common for all such systems to be referred to as jamming. There are two general classes of radar jamming, mechanical and electronic. Mechanical jamming entails reflecting enemy radio signals in various ways to provide false or misleading target signals to the radar operator.
Electronic jamming works by transmitting additional radio signals towards enemy receivers, making it difficult to detect real target signals, or take advantage of known behaviors of automated systems like radar lock-on to confuse the system.
Various counter-countermeasures can sometimes help radar operators maintain target detection despite jamming. Mechanical jamming is caused by devices that reflect or re-reflect radar energy back to the radar to produce false target returns on the operator's scope. Mechanical jamming devices include chaff, corner reflectors, and decoys.
Electronic jamming is a form of electronic warfare where jammers radiate interfering signals toward an enemy's radar, blocking the receiver with highly concentrated energy signals.
The two main technique styles are noise techniques and repeater techniques.
The three types of noise jamming are spot, sweep, and barrage. The burn-through range is the distance from the radar at which the jamming is ineffective. When a target is within this range, the radar receives an adequate target skin return to track it.
In some cases, jamming of either type may be caused by friendly sources.
Inadvertent mechanical jamming is fairly common because it is indiscriminate and affects any nearby radars, hostile or not. Electronic jamming can also be inadvertently caused by friendly sources, usually powerful EW platforms operating within range of the affected radar. A lower RCS also reduce the "burn-through" range. Stealth technologies like radar-absorbent materials can be used to reduce the return of a target.
While not usually caused by the enemy, interference can greatly impede the ability of an operator to track. Interference occurs when two radars in relatively close proximity how close they need to be depends on the power of the radars are operating on the same frequency. This will cause "running rabbits", a visual phenomenon that can severely clutter up a radar display scope with useless data.
Interference is not that common between ground radars, however, because they are not usually placed close enough together. It is more likely that some sort of airborne radar system is inadvertently causing the interference—especially when two or more countries are involved. The interference between airborne radars referred to above can sometimes usually be eliminated by frequency-shifting the transmitter s.
The other interference often experienced is between the aircraft's own electronic transmitters, i. This interference is eliminated by suppressing the radar's reception for the duration of the transponder's transmission.
Instead of "bright-light" rabbits across the display, one would observe very small black dots. Because the external radar causing the transponder to respond is generally not synchronised with your own radar i.
The returning image may be much larger than the "dot" or "hole", as it has become known, anyway. Keeping the transponder's pulse widths very narrow and mode of operation single pulse rather than multi-pulse becomes a crucial factor. The external radar could, in theory, come from an aircraft flying alongside your own, or from space. Another factor often overlooked is to reduce the sensitivity of one's own transponder to external radars; i.
In this way it will only respond to nearby radars—which, after all, should be friendly.
Jamming radar for the purpose of defeating police radar guns is simpler than military-grade radar jamming. The jamming of bat sonar by certain tiger moth species has recently been confirmed. From Wikipedia, the free encyclopedia. This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources.