Why Using These Two Words Together?
During decades when we have refered to cyber-attacks people automatically linked the concept to network disruptions and internet hackers, leading to dozens of action and sci-fi movies where a group of characters broke the internet security layers.
Nowadays these network-related threats still exist, and more resilient methods have been developed to countermeasure them. However, new threats are adding to the cybersecurity list, this time not related to internet issues, but to signal hackers.
GPS, the satellite system responsible for spotting a blue dot in your smartphone’s Maps app is, as any other wireless telecom system, not exempt to service disruptions or malfunctioning. GPS interference has been an increasing problem every year provoking service denial in critical applications.
GPS is a system in which satellites send signals towards the Earth, where they are received by so-called GPS receivers to calculate its own position. These receivers are placed on aircrafts, ships, cars, smartphones but also banks, electric grids, weather stations or smartwatches, because although the system was designed for navigation purposes, the industry has seen other ingenuous use cases of GPS than the system’s original architects could have ever imagined, especially after its civilian use has been globally spread since disabling the system’s “selective availability” in the 2000s. We refer to satellite navigation systems as GNSS, which stands for Global Navigation Satellite Systems, a set of satellite constellations to which the American GPS belongs. GPS, along with other wireless navigation systems, are also known as Position, Navigation and Timing (PNT) service providers
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As previously mentioned, such a critical system is threatened with the presence of interfering signals operating in the same frequency band. In the wireless communications field, and especially on Satellite Navigation or GNSS, two important keywords are linked to the cybersecurity: Jamming and Spoofing.
Jamming is the presence of a signal in the GPS frequency band, with power sufficiently high to mask the satellites’ signals and disrupt the GNSS service intentionally. Spoofing, on the other hand, refers to the presence of a GPS-like signal (and therefore also on the same frequency band) generated by an artifact that imitates a specific satellite, with power sufficiently high so that a GPS receiver is mislead by “listening” to the fake signal rather than listening to the signal coming from the real satellite.
As a result, in both cases there is a service disruption, either because of an interference or an untrusty signal. The detection and mitigation of these events is an active research field and several countermeasures can be applied. Such approaches to either detect or mitigate these signal cyberattacks reside in either the signal processing or in the navigation modules of the GPS receiver. This is done through digital signal processing algorithms, as well as by using multi-frequency and multi-gnss receivers or other navigation sensors such as Inertial Measurement Units (IMU) or Light Detection and Ranging (LiDAR), among others.
If we think on alternative technologies to GPS, it is important to highlight the usage few of them. These include, among others:
- Visual-Based Navigation as an alternative that has been used in Unmanned Aerial Vehicles.
- Cellular-positioning as Time-Difference of Arrival that is used in LTE (4G) communications.
- or even other satellite navigation systems such as the LEO (Low Earth Orbit) orbit systems, which are newer and different to the current GNSS as we know it, that operate in the MEO orbit (Medium Earth Orbit).
Several proposals have been under study for developing a backup technology. The U.S. Transprotation Department has been directed by the National Timing Resilience and Security Act of 2017 to come up with an alternative in the form of a land-based timing system. It has been stated that several technologies could provide complementary service in case of GPS disruption, but none of these would be such a general backup for both the timing and navigation capabilities of GPS.
After the Transportation Department evaluted 11 technologies, NextNav’s TerraPoint was found as the one that matched all the use cases. TerraPoint is a land-based system, like “land-GPS” that provides PNT services from beacons, which transmit radio signals from cell towers rather than from space.
Several technologies are already being implemented for providing PNT services both in space an on Earth. An example of space approaches are the LEO services like Xona Space Systems, which aims to have its own satellite constellation, or Satelles which uses Iridium satellites for location and timing. On the other hand, an example of PNT services provided by systems on Earth are the aforementioned TerraPoint by NextNav, which acts as a land-based GPS.
Meanwhile, GPS is still getting boosted with the recent launch of GPS III satellite series, which have enhanced accuracy and improved anti-jamming capabilities.
Thank you for reading!
|CNET. GPS at risk: Those signals are more vulnerable than you realize. https://www.cnet.com/science/gps-at-risk-those-signals-are-more-vulnerable-than-you-realize/|
|CISA. Understanding Vulnerabilities of Positioning, Navigation and Timing. https://www.cisa.gov/sites/default/files/publications/fact_sheet_pnt_vulnerabilities_508.pdf|