Verizon and AT&T were hoping to fire up their new mid-range 5G networks in the coming weeks, but they may have to wait a little longer. The launch of the C band was previously scheduled for December 5th, but the Wall Street Journal now reports it will be January 5, at the earliest. The issue is the potential interference with the safety systems of some aircraft.
5G connectivity in the US is in trouble right now and the spectrum in band C is seen as a milestone in making 5G live up to the hype. Verizon and AT&T recently spent billions of dollars on licensing for this spectrum because they tried to put together a functional 5G network with scraps. I’m sure carriers would contest this description, but their focus on the 5G millimeter wave speaks louder than any protest. These signals have high speeds, but the range is abysmal: it doesn’t even work indoors.
Mid-band 5G (like C-band) can handle higher data throughput than lower LTE-like frequencies, but still have a respectable range. There isn’t much of any of this around. In the absence of adequate midband spectrum, Verizon has resorted to using dynamic spectrum sharing (DSS) to run a 5G network in the same bands as 4G. The results aren’t surprising, but the C-band should solve this.
The spectrum that AT&T and Verizon want to use is in the 3.7-4GHz range, which is only part of this C-band block. C-band was reserved for satellite TV signals, but satellite broadcasts in this range required huge antennas. 10 feet and larger – you may remember seeing them quite often in the 80s and 90s. They have mostly been replaced by Ku-band technology, which can use smaller 1-foot dishes. With modern technology, it is possible for operators to squeeze the remaining usage of the C-band, opening up large swaths of these frequencies that are optimal for 5G. And that’s what they are doing; traders will be done with the lower C band on December 5th.
The aviation industry has been expressing concern about C-band interference for some time, and this prompted the Federal Aviation Administration (FAA) to finally take action this week. It issued a “special information bulletin” which detected the potential for interference in C-band with radio altimeters. These devices measure the height of the aircraft from the ground using radio waves between 4.2 and 4.4 GHz, which is adjacent to the new 5G C-band. The FAA believes that C-band broadcasts could leak into the altimeter’s range, causing potential safety concerns.
Industry experts point out that there is no evidence of problems like this in other regions where mid-range 5G is more developed. However, this is a “better safe than sorry” situation. Carriers are working with regulators to understand the FAA’s concerns. The launch is likely to go ahead in early 2022, but you never know. Meanwhile, T-Mobile is quite sitting on the big spectrum pile it got from Sprint. The Band 41 block (2.5 GHz) is generally faster than LTE and has a better range than mmWave, so it’s already in a good position for 5G. T-Mobile has also acquired a piece of the C-band spectrum that won’t be clear until 2023. AT&T and Verizon will push hard to start with the C-band to catch up with Tmo.