By 2020, the UK’s National Police Air Service (NPAS) and a number of partner agencies, including helicopter air ambulance services, are switching over to state-of-the-art, vehicle-mounted communications devices operating on a private 4G network. Part of the Emergency Services Mobile Communications Programme (ESMCP), this new equipment can provide increased resilience and security across all communication channels and navigation devices used by emergency services air crews in the UK. In addition, new services and applications will be launched which improve the function, efficiency and safety of the emergency aircraft services. However, the nature of the security landscape for these technologies and services is evolving rapidly. Their reliance on Global Navigation Satellite Systems (GNSS) to deliver location data to users of the ESMCP leaves them open to outside disruption. Unless properly addressed and mitigated, these threats could pose a critical risk.
Emergency services aircraft in the UK use satellite navigation for tactical operations; they do so primarily through the satellite receivers in their onboard vehicle communications systems. However, when such systems fail, the consequences have the potential to be severe. According to reports filed on NASA’s Aviation Safety Reporting System (ASRS), there were nearly 80 incidents of aircraft GNSS signal interference or malfunctions between 2013 and mid-2016. One particular entry from a helicopter pilot who was delayed in taking off from an urban helipad provides an unnerving example of the effects of GPS failure: “Loss of reception on both GPS units when departing the helipad. Ground units use this pad as an LZ due to very few options available in that area. Loss of reception occurred at XA:40 and GARMIN 530 unit gave me the error message and reacquired satellites in about 10 seconds and the GARMIN 430 unit took about three to four minutes to reacquire satellites. Reception was regained and no other anomalies.”
Whilst the satellite signal was re-established, such time delays could prove fatal for emergency service call-outs where a matter of minutes often means life or death for patients in critical conditions. What’s more, the large majority of the incidents logged involving GNSS system failures involved either a total loss of signal or misreporting of the aircraft’s position.
While GNSS has become a phenomenally successful source of navigation for a plethora of industries, it suffers from vulnerabilities that make systems reliant on GNSS inherently fallible. GNSS satellites orbit the Earth at an altitude of over 20,000 km. By the time this signal reaches the Earth’s surface it is very weak – sometimes imperceptible from the background noise of other transmissions – and so complex algorithms are needed to identify and track them. If additional ‘noise’ is transmitted over the top of a GNSS signal – called ‘jamming’ – it can stop a receiver from working.
Jamming devices, designed for this specific purpose, are available for as little as £30 online and their effects can be severe. To put it in perspective, 10mW jammers for that price can be as small as cigarette packs and could knock out satellite signals across the area of a commercial airport. Results from the NSL Strike3 Project – an international investigation into GNSS threats funded by the European GNSS Agency – found in one location 400 GPS jamming interference incidents in a single week at an airport, 138 incidents on a motorway and 839 in an inner city location.
However, the switch-over to the ESMCP’s private network provides an opportunity to tackle this issue. According to a Prior Information Notice issued last September, as part of the Air to Ground (A2G) Devices Project, new vehicle-mounted devices will replace those with existing GNSS security vulnerabilities: “The Home Office is intending to procure a combined Long Term Evolution (LTE) and TETRA airborne device as part of an A2G service for ESN.” Anti-jamming technology now exists which can be introduced to these devices to ensure emergency services do not fall victim to GNSS interference.
A new generation of multi-constellation, multi-frequency (MCMF) receivers, has been developed by QinetiQ through its own research as well as through other projects with the likes of ESA and the UK Government. These receivers can simultaneously use signals from different frequencies and different GNSS constellations, such as GPS, Galileo, GLONASS and BeiDou. In the event of jamming, the receiver can adjust to a different frequency or signals, foiling the jamming interference. This provides enhanced resilience and robustness by using all the different satellite-based navigation systems available, ensuring continuity of service. For a sector that relies on GNSS for life and death situations, these technologies could be a turning point against the increasing threat of signal jamming.
If the ESMCP is to ensure complete security and redundancy against all kinds of threats to the emergency services communications technology, then defending navigational capabilities will be paramount. The government will need to work with industry players and the emergency services to achieve this, ensuring that as the ESMCP is developed and brought online, the capability to overcome jamming incidents is a core part of its design.