C-band triggers chaos in 2021

The C-band was one of those events that kept on giving throughout 2021. Those who participated in the C-band auction – namely Verizon and AT&T – spent record amounts, to the cumulative tune of more than $81 billion, on precious mid-band spectrum for 5G. This, only to be told later in the year that they would threaten airline traffic if they were to actually use the spectrum for commercial purposes.

The wireless operators spent so much money in part so they can catch up with T-Mobile, which acquired its sizable prize of 2.5 GHz mid-band spectrum through the merger with Sprint. While AT&T and Verizon were waiting for satellite operators to clear out of C-band spectrum, T-Mobile forged ahead with the deployment of its 2.5 GHz spectrum, further solidifying its 5G coverage lead with “Ultra Capacity” 5G.

AT&T and Verizon had to wait to deploy their mid-band spectrum until the end of 2021 – a date they voluntarily postponed to January 5, 2022, due to the aviation community’s concerns. They also volunteered to lower the power emanating from C-band equipment near airports for six months to give aviation officials more time to study the situation.  

RELATED: AT&T, Verizon postpone C-Band rollouts until air safety review

Still, near the end of 2021, the Federal Aviation Administration (FAA) issued safety directives for pilots of airplanes and helicopters about the risk of C-band and their reliance on radio altimeters under certain conditions near C-band equipment. While the threat to airline safety remained the subject of debate, aviation officials said that turning on C-band spectrum could lead to delays in air travel for passengers and cargo.

On December 23, the FAA posted newly published documents providing further information about steps that will be required in areas potentially affected by 5G C-band interference.

Why so late?

A lot of folks, understandably, wondered why aviation officials, led by the FAA, waited until what seemed to be the 11th hour to warn airline pilots of the dangers of using archaic radio altimeters in the presence of C-band spectrum. Surely, they had plenty of time to issue warnings and plan accordingly, right?

RELATED: C-band costs rise as AT&T, Verizon unscramble cluster with aviation: Editor’s Corner

The auction closed in early 2021, and it happened after years of very public fights between satellite companies, the FCC and wireless officials. In fact, the satellite companies had been using the spectrum for years prior to the FCC instructing them to move so that the lower part of the band could be cleared for 5G.

Indeed, many of the same groups opposed to turning on 3.7 GHz C-band for 5G in 2021 were among those who voiced concerns back in 2018, when they said radio altimeters operating in the adjacent 4.2-4.4 GHz radio frequency could be compromised.

In the FCC’s written decision about repurposing the C-band for 5G, the commission noted that a 220-megahertz guard band would protect radio altimeters in the 4.2-4.4 GHz band – double the minimum guard band requirement initially discussed by Boeing and other aviation officials.  

The wireless industry trade group CTIA also pointed out that nearly 40 countries already are safely using these and similar radio waves for 5G, at similar power levels, with no evidence of harmful interference with aviation equipment.

RELATED: Airline execs blast away at C-band before commercial deployments

Last week, CTIA issued a joint statement with the Aerospace Industries Association and Airlines for America about their “ongoing collaboration to find a data-driven solution” to deploy 5G while ensuring aviation safety. CTIA reiterated the wireless industry’s plan to launch 5G in the C-band on January 5, 2022.

“We are pleased that after productive discussions we will be working together to share the available data from all parties to identify the specific areas of concern for aviation. The best technical experts from across both industries will be working collectively to identify a path forward, in coordination with the FAA and FCC,” the groups stated. “Our belief is that by working collaboratively in good faith on a data-driven solution, we can achieve our shared goal of deploying 5G while preserving aviation safety.”