Over the past week, many airlines canceled their flights to the US over fears that the new 5G C-band rollout will impact safety on many routes. While 5G services have been live in the US and at least 40 other countries over the past couple of years, these new fears over the mid-band frequency have the potential to derail rollout of this next generation telecom technology in many markets.
What is C-band?
A band is a specific range of frequencies in the radio frequency (RF) spectrum, which is divided among ranges from very low frequencies (vlf) to extremely high frequencies (ehf). Each band has a set upper and lower frequency limit. Because a band is valuable, it is regulated by national agencies such as the Federal Communications Commission (FCC) in the US.
C-band, a radio frequency band between 3.7 and 4.2GHz. “C-band is not a new frequency, but a part of mid-band,” Pulkit Pandey, Associate Principal Analyst at Gartner, told indianexpress.com. “Every country has their own set of rules in accordance to which the spectrum rollout is planned.”
Initially, the C-band spectrum was set aside for satellite TV in the US. But last March, the FCC allocated C-band for use in 5G. A total of 21 companies took part in the FCC auction last year with about 5,600 C-band licenses up for grabs. In fact, the FCC managed to sell a range of C-band in the 3.7 GHz to 3.98 GHz frequency range last February for $81 billion, with Verizon and AT&T dishing out $44 billion and $23 billion, respectively.
C-band is already in use across the world, making it the most popular 5G band. According to the International Telecommunication Union (ITU), C-band is divided into three subsets: band n77, band n78, and band n79. While the EU uses n78 which is in the range of 3.3 to 3.8GHz, the US will use n77, a larger band stretches from 3.3 to 4.2GHz. Japan already uses band n77. All major flagship smartphones including the Galaxy S21 series, Galaxy Fold lineup, iPhone 13 and Google Pixel 6 support C-band in the US.
Why are the airlines worried about C-band?
Both AT&T and Verizon were supposed to roll out 5G services on C-band frequencies in December last year but voluntarily decided to delay for two weeks after the FAA and the airline industry raised concerns over potential interference to airplane safety mechanisms from 5G deployments in C-band frequencies.
“The whole debate right now is between the altimeter and frequency,” Pandey explained. An altimeter that works in the range of C-Band frequencies 4.2 and 4.4GHz not only tells the altitude at which the aircraft is but also filters out other frequencies. This instrument is critical for landing aircraft in low-visibility conditions like rain, fog, and heavy snow. But the fear is that these aren’t designed to be used with the same band as the 5G networks.
Pandey explained that it is not yet clear if the altimeters can filter out interference from the 5G networks especially when the airplanes land. Since the US has over 1,30,000 small single-engine aircraft the worries are not limited to just large airliners.
The CTIA, the wireless industry’s main lobbying arm, made its point by saying that airplanes fly uninterrupted in over 40 countries where similar 5G services are deployed. However, it is to be noted that those countries have also taken steps to avoid the risk of potential negative effects on aircraft safety equipment by either moving towers or receivers away from the runway or by lowering 5G’s power to avoid aircraft interference.
For now, AT&T and Verizon have agreed to temporarily limit deployment of 5G C-band of the spectrum near airports, but 5G towers elsewhere can broadcast C-band spectrum starting January 19.
Meanwhile, the FAA is in the process of verifying which radio altimeters can filter out signals from the new 5G transmitters. The FAA now estimates 78 per cent of the US commercial fleet has been cleared to land at airports with 5G C-band, even under low-visibility conditions. But critics question the timing of the move as many believe the government agency could have verified this when the spectrum was being auctioned off.