Most drones on the market today are operated within close distance of the Remote Pilot, using a direct radio link, like model aircrafts, for Control and Command. These radio links are vulnerable to interferences, starting with unintentional interferences (terrain, buildings…) and drones have procedures in case of loss of communications link.
For longer distance drone operations in kilometres, the most appropriate communication links are 4G 5G mobile networks and satellite communications networks. These networks have developed cybersecurity strategies and standards to support multi-billion end-user industries, and drone connectivity will benefit of it. In the UK, OFCOM, the communication regulator, issued in December 2022 its decision to set up a mobile and satellite communications onboard equipment licence for UAS.
Drone = UAS (Unmanned/Uncrewed Aircraft System) = RPAS (Remotely Piloted Aircraft System)
WHAT IS A C2 COMMUNICATION LINK?
C2 means “Command and Control” link. It is the communication link between the drone in the air and the Control Unit on the ground that the Remote Pilot uses to control the UAS and give his/her commands to the aircraft.
Source: OFCOM, June 2022
To operate a UAS, a radio link is or will be needed to perform the key C2 functions as well as other tasks, such as:
Relaying of payload data – for data and video to be sent from the UAS to the remote pilot/operator;
Electronic Conspicuity – technology to make other airspace users aware of the UAS’s location and flight path;
Detect and Avoid – the capability for the UAS to avoid objects or other aircraft to a level at least equivalent to the ‘see and avoid’ principle in crewed aviation; and
Communications, navigation, and surveillance – depending on the airspace in which the UAS is being flown and also on the capability of other systems on the UAS, Air Traffic Controllers may need to maintain oversight and control of the flight.
WHAT kind of radio link is, or will be, used between the drone and the ground?
Today for most drones: direct radio link, like a model aircraft
Most drones commercially available today use direct radio links, like model aircrafts. Typically, these devices either use the 35 MHz frequency band (designated for airborne model control) or the 2.4 GHz and 5 GHz frequency bands (using Wi-Fi or other low power radio network technologies).
Now and for drone operations with a range in kms: 4G 5G mobile and satellite networks
A direct radio link has its limits, starting with range: 3-5km max for most drones on the market, up to 20km range for higher range system.
Also, the direct radio link can be impacted or lost in case of obstacles, like houses, terrain, or sometimes even trees.
As a result, as the operational range of UAS flights is increasing, a radio link or Wi-Fi link is not suitable and does not provide the necessary coverage.
The two leading solutions that meet the coverage needs of long distance drone operations are the use of satellite and/or mobile networks.
OFCOM, the UK's communications regulator, has issued its decision in December 2022 to “introduce a new UAS Operator Radio licence to authorise the use of radio equipment on drones. The authorisation of this equipment is an enabler for drones to be operated beyond visual line of sight (BVLOS). The licence authorises a range of equipment that an operator may choose to use or be required to carry by the Civil Aviation Authority (CAA). The UAS Operator Radio licence will:
Cover all drones a company or individual operates in the UK and territorial waters but does not cover international flights.
Have an indefinite duration, subject to payment of an annual licence fee of £75.
Authorise a range of specific radio equipment that may be needed for future drone operations, including beacons and safety equipment that may be mandated by the CAA. The list of equipment will be kept under review and, subject to consultation, will be updated to reflect changes in technology or the overarching air safety framework.
Permit the use of satellite and mobile technologies while requiring the specific agreement of the network operator(s). No transmission will be permitted in the 2.6 GHz band.
This licence does not replace the current licence exemption regime for low power 2.4 GHz and 5 GHz equipment which most drones on the market currently fall under. “
Source: OFCOM “Spectrum for Unmanned Aircraft Systems (UAS): Approach to authorising the use of radio equipment on UAS”, December 2022.
What is the impact in terms of security?
Direct radio links like Wi-Fi are vulnerable, they can be impacted by unintentional interferences, such as interference from other signals in the airspace, harsh weather conditions, buildings. They can also be subject to intentional interferences from malicious actors.
4G/5G mobile networks and satellite networks are used in a broad array of end-user industries, including mobile online banking. Of course, both types of networks are prime targets for cybercriminals. However, industries have developed cybersecurity strategies and standards to securely support a large array of multi-billion or trillion client industries, and drone connectivity will benefit from that umbrella.
Still, what happens if a drone loses its C2 link?
The loss of a C2 link could result in the pilot no longer being able to manage the aircraft’s flight. This is a known vulnerability of current radio links and as such there are methods in place to mitigate and manage the drone in the event this happens, with some examples being:
Redundancy of communication links
Fail-safe modes automatically triggered by the loss of C2 signal, without the need for human input. Typically, drones on the market would perform one of three things: return to home (RTH), hover on the spot, or land, or a combination of those.
“Return to Home” RTH is the most typical solution used in the industry and simply means that if the C2 link is lost and can’t be recovered, the drone will automatically reverse (whether this is straight away or after a set amount of time) and go back to the home point where the flight started, or to a pre-determined safe landing point. This will also activate when the battery charge is running low.
Paired with the RTH function are the landing protection mechanisms. The drone has sensors and gyros onboard so that it will first hover then find a safe area to land without risking contact with uneven terrain or other objects e.g., rocky terrain or forested areas – or people of course.
Anti-jamming equipment onboard.
Disclaimer: this overview is correct to the best of our knowledge, but may contain misunderstandings or inaccuracies to comment, feel free to contact us at email@example.com.
By Robert Burns and Anne-Lise Scaillierez