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DALLAS - The new generation of commercial wireless communications (5G) and the proliferation of 5G antennas have raised concerns about interference with aircraft operations during landings at airports. But what is 5G technology?
5G is the 5th Generation Mobile Network technology succeeding 4G-LTE that is being designed by the International Telecommunication Union (ITU-R) and 3rd Generation Partnership Project (3GPP) to virtually connect everyone, and everything, including machines, objects, and devices, together on the internet to provide an immersive experience, telepresence, and massive connectivity as well as advancing internet of things(IoT) at the faster data rate.
5G can reach a data rate of up to 20 Gbps and a user experience of up to 100 Mbps, low latency compared to 4G, support device density of 1 million devices per 1 Km2, and the mobility of 500 Km/hr which can support high-speed railways and flying drones.
5G technology services are delivered using the upper bands of UHF (ultra-high frequency), SHF (super-high frequency), and the lower band of EHF (extremely-high frequency) of the radio frequency spectrum. The 5G frequency ranges are 1 to 4 GHz, 6 to 24 GHz, 30 GHz, and 40 GHz.
Since the commercialization of 5G in April 2019, more than 89 countries, including Tanzania, have invested in, tested, deployed, and launched 5G network services in different radio frequency ranges.
For instance, the European Union and South Korea use 3.4 to 3.8 GHz and 3.42 to 3.7 GHz bands respectively, while the USA uses 3.7 to 4.2 GHz bands.
Risk of Interference of Aircraft’s Radar Altimeter from 5G Radio Frequencies
The Radar Altimeter, also known as a Radio Altimeter or a low-range radar, is a critical instrument that enables and enhances several different safety and navigation functions in civil, commercial, and military aircraft by determining and showing height above ground level. It provides situational awareness to the crew during different phases of flight and instrument approaches.
The Radar Altimeter operates in an Aeronautical Radio Navigation Service (ARNS) spectrum allocation, in the 4.2 to 4.4 GHz band, and its information forms a part of the Terrain Awareness and Warning System (TAWS), Traffic Alert and Collision Avoidance System (TCAS), wind shear detection system, flight control system, autoland systems (including autothrottle and automated landing flare and roll out), Automatic Flight Guidance and Control System (AFGCS), as well as the Electronic Centralized Aircraft Monitoring (ECAM) system.
A study conducted by the Radio Technical Commission for Aeronautics (RTCA) in 2020 found that both 5G base stations and user equipment on board an aircraft operating in the 3.7–4.2 GHz frequency band (currently deployed in the USA) presented a risk of harmful interference to Radar Altimeters (which operate in the 4.2–4.4 GHz range) across all aircraft types with far-reaching safety consequences and impacts to aviation operation.
Radar Altimeter interference from 5G radio signals can cause the loss of radar altitude information or, worse, incorrect radar altitude information being generated unknowingly.
Impacts on the US Aviation Sector
The Federal Communication Commission (FCC) auctioned a frequency band from 3.7 to 3.98 GHz of the allocated 3.7 to 4.2 GHz frequency band to telecommunications companies AT&T and Verizon and some regional airports were included in the network deployment.
Because this frequency band sits close to the radio altimeter operation frequency of 4.2 to 4.4 GHz, the interference could lead to safety consequences in the aviation industry.
As a result, the Federal Aviation Administration (FAA) imposed restrictions on aircraft operation, which led to airliners delaying, diverting, or canceling their flights in airports equipped with 5G and during poor weather.
Turkish Flight TK1951 Crash Due to Fault Radar Altimeter
On February 24, 2009, Turkish Airlines (TK) Flight TK1951, operating a Boeing 737-800 from Istanbul (IST), Turkey, and carrying 135 souls, crashed at Amsterdam Schiphol Airport (AMS), the Netherlands, after stalling while landing at 400 ft due to a faulty radar altimeter and pilot error.
The faulty radar altimeter caused the automatic throttle control system to decrease power to idle during the approach. The crew noticed this too late to take appropriate action to increase the thrust and recover the aircraft before it stalled and crashed.
The airliner broke into three pieces on impact resulting in the deaths of 9 passengers and crew, including all 3 pilots.
The Likelihood of the Co-existence of 5G and the Radar Altimeter
Aviation safety and 5G can co-exist, but stakeholders must collaborate to find and lay permanent solutions. Some of the implementable solutions could include:
Updates to Radar Altimeter
Future radar altimeter designs should be improved to become more resilient to radio frequency interference in the 3.7—3.98 GHz band by updating the Minimum Operational Performance Standards (MOPS).
The Altimeters should then be certified with additional performance requirements for the RF interference rejection. In the step to solve the problem, the FAA has approved new and more robust and reliable radar altimeters which are resistant and eliminate 5G C- Band radio signals interference with unique digital signal processing (DSP) technology.
Reducing 5G Power Levels and Antenna Heights
Every country deploying 5G could impose some level of restrictions on its use to protect radar altimeters against harmful interference. These may include reducing both the power levels of 5G transmissions and antenna heights near airports and along approach and landing paths.
Also, 5G transmissions could be limited to antennas pointing skyward and at locations near public helipads. These measures will ensure that 5G operates at a greater distance from the aviation environment and limit the directional tilt of the 5G antennas.
Sufficient Spacing for 5G Frequency Bands from the Radar Altimeter
ITU standards specify an adequate margin of a 6dB requirement from a Radio Altimeter's operating frequency limits to eliminate the possibility of radio interference by other radio frequency services.
Countries, when choosing and managing frequency spectrum for 5G, should ensure required spacing between frequency usage to eliminate interference possibility.
For instance, the European Union and South Korea chose 5G frequency bands far from Radio Altimeter frequency limits and did not experience cases of interference with their operations.
Restricting 5G in the Airport Vicinity
Experts advise countries to restrict the deployment of 5G in the airport vicinity unless viable solutions are in place to mitigate the interference of radar altimeters from 5G signals.
When Canada approved 5G in the frequency band of 3.45 to 3.65 GHz, restrictions were placed in the vicinity of 26 airports to ensure aviation safety.
To learn more about the protection of the civil aviation spectrum and aircraft safety systems, you can read IATA's Aviation and 5G and 5G and Aviation Safety documents.
Featured image: Michael Rodeback/Airways
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