5G aircraft interference: could simulation help?
January 2022 saw the availability of new radio access network (RAN) units from telecommunications companies. These units operate in the 5G mid-band spectrum, which was bought by telecommunications companies at the end of 2020 in order to take advantage of up to 280MHz combined bandwidth. Not only does this bandwidth allow for faster download and upload speeds than 4G LTE services, but it also has an improved range and performance than 5G mm-wave bands.
This purchase, however, has not been warmly welcomed by the FFA, the Department of Defence or the commercial airline industry. They have all reported concern about the danger of potential interference with the radar altimeter systems on their aircrafts. To add fuel to fire, auto-landing and other flight systems that are used in low altitudes have been banned in areas where 5G interference could interfere with these systems.
Radar altimeter systems have simply not been designed to anticipate and reject the strength of these adjacent signals, causing many aircrafts to now fall under scrutiny. Both the developers of radar altimeters and the aircraft manufacturers who use them, must now test their equipment and designs to see just what impact 5G towers can have when in close proximity to an aircraft that is taking off or landing.
It may seem surprising, but all of this may well have been avoided had electromagnetic simulation software been leveraged.
The journey to the crisis
So, what brought us to this point? Radio frequency systems are used for a variety of missions, most notably perhaps, as critical components to instrument landing systems and autopilot. Historically, radar altimeter use has been protected in the 4200-4400 MHz band. The FCC, however, decided to relocate the band due to the telecommunications industry’s need for additional bands. Following this relocation, the FCC later sold the telecom spectrum at auction.
As radar altimeters don’t use the same frequency band as telecommunications companies, why was there an issue? Well, because there is sensitivity to interference. Radar altimeters can be disturbed by frequencies from out-of-band sources, risking erroneous readings of the distance to ground. Not only this, as these radar altimeter systems are coupled to automated landing and takeoff systems, interference could cause landing gear to lower, or even a rapidly change in thrust during flight. This poses a huge risk to customer safety.
So, what can simulation do to help?
When simulation tools exist that can predict this kind of interference effect, and even provide guidance on how to mitigate it, it is rather surprising that we are faced with this issue today. Engineering simulation tools have been designed to consider wideband transmitter emissions and evaluate their impact on wideband receiver characteristics, considering both in-channel and out-of-band effects. Antenna systems must also be taken into account, allowing for the orientation and position of the aircraft as well as the beamforming and beam steering characteristics of the 5G antenna system. Alongside this, simulation can also be used to model the physics of these antenna systems, as well as analyse their installation effects, even over long distances.
Simulation has already made huge strides in the Aerospace and Defence sector. From incorporating large databases of materials for more innovative product design, to assessing aerodynamic resistance, leveraging simulation tools can result in efficient, impactful change. While both the aviation and telecommunications industries continue to damage control, one can only hope that simulation technology will be used to assess interference effects in the future, saving everyone a lot of time, money and energy.
