“Remember to turn off your phone before takeoff«.
If you have ever had to fly in an airplane, you will know that this is one of the main security rules of the airlines when getting on one of their aircraft.
And it is that, despite the fact that technology advances by leaps and bounds and that new devices come out every day to make our lives easier, all the devices we use are limited by the basic physical principles that govern the universe.
For example, the waves that your cell phone emits and receives are radio waves and move in the same electromagnetic spectrum used by radios and aircraft antennas. The only thing that changes is the frequency on which they are transmitted.
It is this basic principle of physics that explains why it is better not to use your phone on a plane: by preventing the use of mobile phones in the air, the aeronautical authorities seek to minimize the chances that the waves that reach your phone interfere with those reaching the aircraft’s navigation equipment.
And while this is a very basic explanation of a fairly complex process, it also helps explain why airlines in the United States have asked the country’s cell phone providers to delay the rollout of fifth-generation (5G) technology by nearly certain airports.
5G and airplanes
At the end of 2020, the United States Federal Communications Commission (FCC) opened an auction to offer telecommunications companies licenses to operate in the so-called “C band” of the electromagnetic spectrum.
Band C is the one used by cell phone providers to deploy 5G, a technology with which they seek to expand speed and cell coverage throughout the national territory.
During the auction, the FCC managed to award more than US$80 billion in licenses.
The problem is that within the frequencies that were auctioned, there were blocks in the frequencies from 3.7 to 3.98GHz, which are very close to those used by the radio altimeters of some aircraft.
These devices operate on frequencies between 4.2 and 4.5Ghz.
That is why, more than a year after the auction and a few hours after the telephone companies roll out their 5G networks in band C, the airlines warned that the country could be facing a “possible massive interruption in the transport of people and goods”.
5G “everywhere, except near airports”
With the deployment of 5G networks in band C set to start on January 19, some of the main airlines in the country sent a letter to the FCC, the Federal Aviation Administration (FAA) and the Secretary of Transportation expressing their concerns .
“We are urgently writing to request that 5G be implemented across the country except within approximately 2 miles of affected airport runways,” argued the letter, signed, among others, by the presidents of American Airlines, Delta and United. .
“The secondary effects on both passenger and cargo operations, our workforce and the economy in general are simply incalculable,” the document argues.
Concern expressed by airline companies prompted two of the largest US cell phone carriers, AT&T and Verizon, to announce that they would delay the rollout of 5G networks near airports.
An AT&T spokesperson told BBC Mundo: “At our own discretion, we have voluntarily agreed to temporarily postpone the power-up of a limited number of towers near certain airport runways.”
Verizon, another of the nation’s large cell phone carriers, made a similar announcement.
However, the AT&T spokesman criticized the federal authorities and the airline companies for not having foreseen these inconveniences, having had almost two years since the auction to do so.
“We are frustrated with the FAA’s inability to do what nearly 40 countries have done, which is safely deploy 5G technology without disrupting aviation services, and we urge them to do so in a timely manner,” the spokesperson said.
He added that the company would continue to work with the industry and the country’s aeronautical regulators, providing them with more information about the deployment of their 5G networks, “since they have not used the two years they have had to responsibly plan this deployment.”
A “simple” question
Professor of electrical engineering Ted Rappaport, who is also the director and founder of the NYU Wireless study center for wireless services at New York University, told BBC Mundo that he saw “very strange” that after so much time after the auction, the airline industry expresses so much concern.
“It is a simple technical solution. Everything is easily solved in aircraft that have bad radio altimeters. They just have to put in band filters so they are less susceptible to interference from other bands.”
In addition, explains Professor Rappaport, there is one more reason to be calm and that is the frequency range between 3.98GHz for 5G and 4.2GHz for radio altimeters. It is what is known as a band of guards.
“There is already a band of guards that the FCC put under consideration for almost two years. The 220 megahertz guard band already exists.”
In addition, he adds, “I’m pretty sure that cellular operators are also doing their part, as they do around the world. They’re just not going to allow cell phone users to use the frequencies closest to the speed cameras.”
To address the dilemma, the FAA announced on Sunday that it had approved two models of radio altimeters “that are installed on a wide variety of Boeing and Airbus aircraft.”
“The FAA also continues to work with manufacturers to understand how information from radio altimeters is used in other control systems,” the federal administration added.