That annoying sound you hear is T-Mobile CEO John Legere cackling madly. PCMag, which every year conducts a comprehensive study of wireless network speeds across the United States, has just published its latest study that shows T-Mobile has surged past AT&T and now offers the second-fastest 4G service in the United States behind Verizon.

This is quite a reversal of fortune for both companies from last year, when PCMag found that AT&T had the fastest 4G network in the U.S. while T-Mobile didn’t even have enough LTE coverage to warrant a score on PCMag’s Mobile Speed Index. What accounts for this dramatic change? PCMag says that it credits T-Mobile’s aggressive efforts to upgrade LTE capabilities in major U.S. cities.

“T-Mobile provided the year’s big surprise, with a powerful showing where it won half of our cities outright,” the publication writes. “The carrier’s performance in the nation’s biggest cities was reliably great.”

There is still one big problem with T-Mobile’s network, however: It still isn’t delivering very strong coverage outside of major metropolitan areas, which is where Verizon and AT&T both excel. Even so, this latest study will make T-Mobile execs very happy and will give them another club they can use to beat on rivals.

On the downside, however, PCMag found that Sprint’s network is still absolutely horrible in just about every regard compared to Verizon, AT&T and T-Mobile. While all three of its rivals scored above a 70 out of 100 on PCMag’s Mobile Speed Index nationwide, Sprint scored a paltry 49, which put it way behind every other major wireless carrier.

PCMag’s full study, which also breaks down carrier rankings by region, is well worth your time and can be found by clicking the source link below.