T-Mobile US (NYSE:TMUS) surpassed Sprint (NYSE: S) as the No. 3 carrier in terms of overall network performance, according to a new report from network testing firm RootMetrics, which covered the first half of 2014. That marks a reversal from RootMetrics' last report, which covered the second half of 2013 and was released in early March.

Verizon took the lead in RootMetrics' report, but T-Mobile passed Sprint. Click here for the full PDF report.

As in RootMetrics' last report, Verizon Wireless (NYSE: VZ) outpaced all of its competitors in terms of overall performance. Verizon also beat rival AT&T Mobility (NYSE: T) in terms of national network speeds, likely due to its rapid deployment of AWS spectrum for LTE services.

Verizon has deployed its AWS spectrum to augment capacity on its LTE network in most of the major cities across the country, and has said it will be done with its AWS overlay by the end of the year. RootMetrics CEO Bill Moore said Verizon's deployment of AWS "has had a material effect" on its performance. "I don't think anybody expected how fast they were going to go about deploying it," he said.

However, it was T-Mobile that showed the most movement in RootMetrics' "Midyear Mobile Network Performance Report." In the last report released in March T-Mobile had a total overall performance score of 64.3 out of 100. This time around, T-Mobile raised its total score to 71.5.

Verizon topped RootMetrics' overall performance charts with a score of 81.6, while AT&T came in second at 79.5. Sprint came in fourth with a score of 69.6. Verizon led RootMetrics' charts in terms of national network reliability, speed, data performance and call performance, with AT&T very close behind on many fronts. AT&T won for best texting performance, RootMetrics said.

Yet AT&T made "impressive" gains in network reliability. In the second half of 2013, Verizon was the clear leader on reliability, but the two networks were virtually dead-even in the new RootMetrics report. Verizon earned 112 wins in its Network Reliability Index across metro areas in the U.S., while AT&T won in 107 markets. The other carriers' networks weren't even close, though Sprint won reliability performance awards in three markets, its first awards in the category. That likely speaks to the lack of low-band spectrum both Sprint and T-Mobile have, something they hope to remedy through next year's incentive auction of 600 MHz broadcast TV spectrum.

RootMetrics testers drove more than 234,000 miles across the country, and tested performance while driving, at stationary outdoor locations, and at more than 6,400 indoor locations. In total, RootMetrics collected more than 5.6 million total samples.

T-Mobile has been working to build out its LTE network, which now covers 235 million POPs. T-Mobile currently has 15x15 MHz LTE deployments in 17 markets and expects to have 26 by year-end. Sprint, for its part, has been using a 5x5 MHz block of its 1900 MHz PCS spectrum for its main LTE deployment to date, covering 254 million POPs. But Sprint is working to build out its speedier Spark service, which combines LTE transmissions across 800 MHz, 1900 MHz and 2.5 GHz, and hopes to cover 100 million POPs with Spark this year.

In the RootMetrics report on the second half of 2013, T-Mobile finished last in five out of six categories, but in the latest report T-Mobile jumped over Sprint and finished in third place in four categories. While the separation between the erstwhile merger partners was small, T-Mobile clearly outperformed Sprint in the speed test. However, RootMetrics noted that via Sprint Spark, the carrier's tri-band LTE service, Sprint could regain an advantage in speed as that deployment gets rolled out through the rest of 2014 and beyond.

In terms of metro-area testing, T-Mobile had 169 first-place awards or ties, up from 60 in the last report.

In an interview with FierceWireless, Moore said T-Mobile's rapid deployment of LTE was a major factor in it moving up the ranks, but noted that both T-Mobile and Sprint are still in the midst of their LTE deployments. "We anticipate we will continue to see improvement in both cases," he said.

Moore said that in areas where Spark has been deployed, RootMetrics is seeing strong speeds. Moore called Sprint "a bit of a dark horse" and noted the carrier needs to attract more customers so they can "get on the network to enjoy the increased speeds that their LTE network is trying to put out there."

Moore also said that T-Mobile's charge shows that the U.S. wireless market remains competitive and dynamic. "I don't think the race is over," he said. "The one constant here is change."

For more:

- see this RootMetrics page



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Article updated Aug. 19 to reflect the name of RootMetrics' "Midyear Mobile Network Performance Report."