Competition works. The latest nationwide report from drive-testing firm RootMetrics shows a dramatic improvement in Sprint's network reliability, taking the perpetual LTE underdog from worst to, well, often not worst any more.

Root drives around the country all year testing mobile networks. They're like PCMag's Fastest Mobile Networks project, but on a larger scale and somewhat less transparent. In its second-half of 2014 tests, the big news was Sprint's advance, jumping to third place for "overall performance" nationwide thanks to dramatically better call and text performance, especially in rural areas.

Let's be clear: Verizon Wireless still has the best nationwide network, by far. We've found that. Root has found that. Most other studies find that. Verizon's LTE coverage and reliability are simply unmatched. But Sprint and T-Mobile are now genuinely scrapping it out with noticeable network improvements month after month, and U.S. consumers are the winners.

Sprint has been stuck down in the dumps for a few years now, routinely coming in a fourth on speed and reliability. This week's Root results show that starting to turn around. Sprint won 135 of Root's awards for reliability, calling, and texting performance, ahead of T-Mobile in those three categories. Sprint also won 32 awards at the statewide level, outpacing T-Mobile, which had only four awards. T-Mobile won more metro area awards, at 201 to 135, showing that much of Sprint's new strength is outside the largest cities.

The secret sauce seems to have been the completion of Sprint's Network Vision plan, especially its conversion of the old Nextel 800MHz band to CDMA voice and LTE data service. Networks in the 700MHz and 800MHz realms tend to have better geographical coverage and building penetration than networks at higher frequencies, such as the 1900MHz Sprint previously used.

"We spent a lot of time in the past year optimizing the network," Sprint's chief network officer John Saw said. "Getting 800MHz out there is absolutely key for voice and LTE."

T-Mobile, unsurprisingly, is derisive towards Sprint's results. T-Mobile CTO Neville Ray pointed out that Sprint's wins happened primarily in rural areas, that some of Root's results are a few months old, and that none of Root's handsets included Band 12, new spectrum that improves T-Mobile's rural coverage.

"The area where Sprint is showing improvement is out there in those rural state drives, and not in the core market testing," Ray said.

Sprint's gains came mostly in calling and texting. In metro areas, Root's report says Sprint "made tremendous strides, particularly in reliability," with a lower blocked-call rate than T-Mobile's but a slightly higher call-drop rate.

"We don't see any of those challenges that they seem to have pulled up," Ray said. "They're highlighting historical dropped-call challenges out in rural America."

Sprint is still having serious trouble with data speed, though. The carrier won zero awards for speed and data performance, where T-Mobile won 52 between those two categories. While Sprint's speeds markedly improved from the first half of 2014 to the second half, it didn't improve quite well enough to compete. Sprint's LTE network is still showing speeds below 6Mbps in 72 markets (down from 108), while T-Mobile only has speeds that slow in five markets. (AT&T is at two; Verizon has only one.)

All of this tells a very specific tale: Sprint's narrowband LTE 1900 and especially its building-penetrating, space-filling but slow LTE 800 are now covering the country much better than they used to, but its fast TD-LTE 2500 network still has poor coverage.

"Clearly we need a lot more 2.5," Saw said. "We're also looking to start to refarm spectrum at 1.9 so we can create a second 5MHz channel to give us more capacity. The focus for this year will be to finish the LTE 800 build-out, and continue to push out 2.5 aggressively."

Needed: More Low-Band Spectrum

Sprint's considerable headroom in its 2.5GHz spectrum explains why the carrier didn't bid in the recently closed, $44 billion AWS-3 spectrum auction, too.

"We didn't play a role because we have ample spectrum at the high band. AWS-3 is fairly close to that," Saw said.

Instead, Sprint may be keeping its powder dry for 2016's auction of 600MHz spectrum to supplement its nationwide, but quite narrow 800MHz allotment.

"We have been watching this 600MHz auction as a real opportunity. AT&T and Verizon currently control 75 percent of all low-band spectrum, and it's important for Sprint to be able to get some 600 if we choose to," he said.

It's spectacularly funny to me how large wireless carriers always say they desperately need to merge to improve network quality, and then when those mergers are denied, they improve network quality anyway. We saw it with AT&T and T-Mobile. Now we're seeing it with T-Mobile and Sprint. Pressed by competition rather than cushioned by scale, they're taking their networks to new levels.

The next chance to take a close look at the carriers' network performance will be our Fastest Mobile Networks 2015 feature, where we'll drive-test the country this May and June. The way Sprint and T-Mobile are looking, this year's results could really shake things up.

Further Reading