The electromagnetic (EM) spectrum has long had its uses in the military arena—ever since battleships began to beat the turn of the 20th century.
Today, electromagnetic signals play a wide-ranging role in warfare and defense, spawning an ever-growing number of descriptive terms. Two of the most commonly used terms are Electronic Warfare (EW) and Navigation Warfare (NAVWAR). Here’s what they mean and how they differ.
What is Electronic Warfare?
The more general term of the two terms, Electronic Warfare refers to any directed use of electromagnetic energy in the pursuit of military operations, military intelligence, or defense against military aggression.
EM energy sources that can be exploited for EW include gamma rays, infrared, microwaves, millimeter waves, radio waves, ultraviolet light and visible light. EW usually refers to the use of these sources to disrupt an adversary’s access to and use of the EM spectrum for navigation, communications or surveillance.
An increasingly important aspect of EW is that its use can extend beyond traditional conflict zones. Like cyber-warfare,like energy grids and cellular networks, with the intention of disrupting daily life and causing economic harm.
What is NAVWAR?
NAVWAR (not to be confused with the US Naval Information Warfare Systems Command, which uses the same acronym) is a subset of Electronic Warfare. It refers to the deliberate disruption of an adversary’s use of global navigation satellite system (GNSS) signals for navigation.
Theoccurred during the Gulf War of 1990-1991, when Iraqi forces used signal jammers to disrupt the Coalition forces’ use of GPS; then a relatively recent introduction.
Since then, disruption of GNSS signals has become a common military tactic, with nation-states engaged in a race to simultaneously develop and protect against new signal disruption techniques.
Offensive NAVWAR tactics: jamming, spoofing and cyberattacks
Today, offensive NAVWAR tactics tend to take one or more of three forms: signal jamming, signal spoofing and cyberattacks on navigation systems data.
This refers to the use of electromagnetic noise to drown out GNSS signals, which are very weak by the time they reach Earth. Jammers broadcast noise on the same frequency as GNSS, leaving receivers unable to distinguish the GNSS signal and less able to calculate their position.
While most military vehicles and equipment use encrypted signals and receivers that are hardened against jamming, any device that makes use of unprotected civilian GNSS signals is highly vulnerable.
This vulnerability can have major repercussions when military signal jamming is deployed over a wide range, as hasin the conflict zones near the Eastern Mediterranean. Signal jamming in these zones has frequently disrupted commercial shipping and air travel.
This is a more sophisticated NAVWAR tactic. It involves transmitting false GNSS signals with the aim of fooling a navigation system into thinking it is somewhere else, or traveling in another direction, in order to convince either the pilot or the autonomous engine to make incorrect corrections.
Recent reports from the Ukraine-Russia war, for example, describeby targeting their built-in geofencing controls. The spoofed signal tells the drone’s GNSS receiver that it’s entering an airport’s no-fly zone, upon which the drone immediately lands, in accordance with its safety procedures.
Spoofing can also be used tothat relies on the precise timing information contained in GNSS signals. If not protected, infrastructure like electricity grids and cellular communications networks can be degraded or denied by spoofing.
While jamming and spoofing attacks, categorized by many as cyberattacks and viewed as an element of a cybersecurity framework, are targeted directly at the receiver’s radio frequency (RF) capabilities, NAVWAR attacks can also be conducted on the processing of navigation data.
For instance, NMEA data used into so-called man-in-the-middle (MITM) attacks, which intercept and alter data between the GNSS receiver and the software system that uses it for tactical decision-making.
Technologies for defending against NAVWAR attacks
Protecting military equipment and personnel against attacks is the other side of the NAVWAR coin. Techniques used to harden and protect equipment include:
Encrypted signals: GNSS systems typically provide encrypted signals for authorized use, which are highly resistant to spoofing and difficult to jam. In the case of GPS the most recently introduced encrypted signal is known as M-CODE, while Europe’s Galileo operates the Public Regulated Service (PRS) signal.
Advanced antenna systems: Military-grade controlled reception pattern antennas (CRPAs) mitigate against spoofing and jamming by analyzing signals’ angle of arrival (AOA) and directing the antenna beam away from threats and towards genuine GNSS signals. Less-sophisticated fixed reception pattern antennas (FRPAs) can detect spoofed signals and raise an alarm.
Anti-jam signal processing: Military-grade GNSS receivers can mitigate against signal jamming using space-time adaptive processing (STAP) and/or space-frequency adaptive processing (SFAP) signal processing techniques.
Alternative sensors: Additional sensors are integrated into a multi-sensor positioning, navigation and timing (PNT) system to ensure continuity of navigation when GNSS is compromised. These typically include inertial measurement units (IMUs), and can also include LiDAR, camera vision, Wi-Fi, cellular positioning, and more.
Techniques and technologies for assessing NAVWAR vulnerabilities
It’s essential to understand the performance, robustness and resilience of any mission-critical GNSS-based PNT system in the face of a NAVWAR attack. Thorough testing, both in the lab and in the field, is critical. Resources typically used for testing receivers, systems, equipment, and vehicles include:
RF signal simulators likecan replicate civilian and (where authorized) encrypted signals including GPS M-CODE and Galileo PRS, for comprehensive GNSS receiver testing in the lab.
Theoffers powerful, flexible capabilities—from interference generation and spoofing scenarios to modeling antenna patterns for CRPA testing and supporting hardware in the loop (HIL) environments for multi-sensor integration. Selective jamming, also known as Blue Force Electronic Attack (BFEA), can also be simulated.
, meanwhile, enables the performance of military-grade integrated/embedded GNSS/inertial systems to be tested in the lab.
In addition to integrated jamming capabilities, interference waveforms can be generated independently from the simulator platform, to emulate the noise produced by RF jamming equipment. Theenables comprehensive testing against the critical threat of RF interference.
To test the physical beamforming capabilities of a CRPA antenna, simulated signals can be transmitted over the air to the antenna in a sealed or anechoic chamber. Here, Spirent’s unique, patented approach toheightens realism and extends test times.
Field testing of military equipment in realistic jamming and spoofing conditions is typically conducted on outdoor test ranges in remote locations. Jammer noise or spoofed signals are transmitted over the air for the duration of the test. The use of dedicated and authorized test ranges helps to minimize the impact of testing on civilian and commercial systems, and enables developers to avoid breaches of local, national, and international law.
Spirent supports two core methodologies for controllable and repeatable field testing of NAVWAR capabilities. The ground-breakingenables the device under test (DUT) to receive live-sky signals while additional signals are broadcasted by the simulator, enabling myriad test cases for PNT resilience. For record and playback testing, the handheld records real signals in high dynamic range for repeatable playback in the lab.
Testing PNT systems with Spirent
For over 35 years, Spirent has been the trusted partner of defense developers and integrators for all aspects of PNT test and measurement.