Exclusive Testing: AT&T's C-Band Triples 5G Speeds

What's better than 40MHz of brand-new 5G? 80MHz. That simple math might explain why AT&T is slow-rolling its 5G C-band launch right now, as we discovered in exclusive tests in Chicago.

Where Verizon says it's blanketing more than 46 metro areas with C-band, AT&T only lists eight—and it doesn't have maps. We got a tip about an AT&T C-band site on Chicago's South Side, so we decided to do a long drive to see how it works and what else we could stumble upon.

The good news is, C-band offers the boost that AT&T needs. Download speeds on the C-band site were triple our average AT&T speeds in the rest of Chicago, showing that once C-band "5G+" gets up and running, it will make a real difference.

AT&T's low-band 5G didn't give us any advantage over 4G/"5GE" the way C-band did. That's consistent with what we've seen in the past: AT&T's low-band 5G only uses 5MHz of spectrum, a very narrow channel. Our testing software, which shows how much data is being transmitted over each channel, showed only a very small amount of data transmitted over that low-band channel.

With C-band, things are different. AT&T's 40MHz C-band channel is twice as big as the largest possible 4G channel, so it makes a real difference in performance. T-Mobile's and Verizon's mid-band channels are even bigger right now. Verizon uses 60MHz C-band channels, while T-Mobile uses a straight 100MHz of its own, non-C-band mid-band, at least on our test drive. But AT&T has something else in the wings, which we'll get to shortly.

In terms of C-band site range, we saw something very encouraging. With a freestanding C-band tower high over a low-rise neighborhood, we started to get signal a full 1.3 miles away from the panel. That's huge! It's very different from our experience in New York City, where Verizon's cells are considerably smaller. That also gives hope that C-band can bring wireless home internet to the suburbs and exurbs.

But...we only saw that one site, and we drove all the way from the city's North Side to the city's South Side. AT&T clearly isn't aiming for citywide C-band coverage the way Verizon is right now. Instead, the carrier may be putting up a few sites for engineering or experimental purposes while it moves to the next phase of its plan.

These maps and results come in part from our new Ookla Wind testing software, an enterprise product that Ookla is making available to PCMag for testing. (Note: Ookla is owned by Ziff Davis, PCMag.com's parent company.)

AT&T's 5G Plan Revealed

AT&T currently has 40MHz of C-band 5G available in 46 "partial economic areas" around the country. But here's the thing: It also just purchased another 40MHz of very nearby, 3.45GHz spectrum it can use in almost all of the country.

The carrier wants to install equipment that can handle both kinds of airwaves using "one tower climb," AT&T CEO John Stankey expressed in an earnings call quoted by Fierce Wireless. That equipment won't be available until late spring or early summer, he said. So AT&T's build will start to really happen in the second half of the year.

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This also helps make sure the right cell phones are in the market to take advantage of AT&T's new holdings. To combine 3.45GHz and C-band, phones need at least a Qualcomm X60 modem, which means using iPhone 13 or Samsung Galaxy S21 phones, as well as some others. The Qualcomm X65 modem will give AT&T even more flexibility, letting it combine 3.45GHz, C-band, and low-band 850MHz 5G—but that's coming with the Galaxy S22 and the iPhone 14.

AT&T is also a bit less desperate to improve performance than Verizon is. AT&T's overall median download speeds were higher than Verizon in January reports from both Ookla and OpenSignal. (T-Mobile is way ahead of both because of its mature, nationwide "5G UC" mid-band buildout.) Our 30-city tests last year agreed, with AT&T taking second place to T-Mobile's 5G network in most cities. While Verizon's speeds notably declined between our 2020 and 2021 tests, showing congestion, AT&T's speeds suffered less of a hit.

So AT&T is willing to let Verizon take the big headlines for now, while it plans to accelerate its buildout in the second half of 2022 and through 2023. The company will cover 200 million Americans with mid-band 5G by the end of 2023, Stankey said.

We're continuing to test the new networks as they roll out (and we can find them), so make sure to check back soon.