Wireless carriers have been upgrading their mobile networks quickly enough to more than keep pace with increasing data use by their customers on new unlimited data plans. That’s seen in the results of millions of network tests conducted by Rootmetrics in the first half of the year, the mobile testing firm said on Wednesday.
“Despite reports suggesting that unlimited data plans are stifling speeds due to increased demands on the networks, we are not seeing evidence of that in our first half 2017 results,” Annette Hamilton, director at Rootmetrics, tells Fortune.
More from FORTUNE
The company’s testing showed that all four major carriers–AT&T, Verizon, T-Mobile, and Sprint—improved average speeds in at least 20 markets in the first half versus the end of 2016. “Taken together, this suggests that investments are being made that counteract any demands on the networks from unlimited data plans,” Hamilton said.
Get Data Sheet, Fortune’s technology newsletter.
The twice-a-year reports from Rootmetrics reignite the debates over network speed, coverage, and quality among the carriers every six months. Verizon and AT&T have long charged more for service than Sprint and T-Mobile based on claims of superior network speed and coverage. Sometimes the report shows the two challengers closing the gap, but sometimes not. And then there is a barrage of other reports from others like PC Magazine, that offer a completely different perspective.
For the first half of 2017, the national results compiled from tests in 125 individual city areas showed Verizon again on top in most categories. The carrier ranked first in overall performance, reliability, speed, data, and call quality at the national level. It was tied for first in texting quality with AT&T and Sprint.
Rootmetrics called Verizon’s national performance “outstanding,” adding that AT&T offered “strong competition,” while Sprint “showed improvement at the national level.” T-Mobile’s national rankings were unchanged from last year, Rootmetrics said.
Drilling down and looking at the same six categories in each of the 125 markets, Verizon notched 617 wins, down from 658 in the second half of 2016. AT&T had 396 awards, up from 372, and T-Mobile grabbed 271 wins, one more than in 2016. Sprint fell back with 211 wins, 35 less than in 2016.
The data points are calculated from some 4.7 million individual tests conducted in vehicles that drove over 276,000 miles and also measured at almost 9,000 indoor locations, Rootmetrics said.
Best Network Debate
No sooner were the results released than the carriers began their debate yet again. Verizon emphasized that although it won fewer city-level awards, it still dominated at the national level. And while T-Mobile CEO John Legere has been saying that Verizon’s network was slowing—”completely choking,” he said last week—under the crush of unlimited data users, Verizon executives denied it.
“What I see is an overwhelming lead over the competition,” Nicki Palmer, chief network officer at Verizon, told Fortune, echoing remarks she has made on past Rootmetrics reports. “When you look at these numbers, they certainly don’t match up to the narrative that some people are trying to put forth.”
“T-Mobile is third or fourth in every single category, which is no change from 2016,” Palmer added. “We are in an unlimited world. These tests are reflective of our performance in that unlimited world.”
T-Mobile tmus typically points to other test results. Speedtest.net reported last August, for instance, that T-Mobile customers’ average reported download speed matched that of Verizon vz customers, while its average upload speed was faster.
“Unbiased scientific studies tell us loud and clear that Verizon’s network is struggling with unlimited and T-Mobile has caught up,” Neville Ray, T-Mobile’s network chief, said. “That’s based on millions of actual customer experiences, not consultants funded by Verizon. Color me surprised that a Verizon-sponsored report claims they’re on top.”
Sprint s chief technology officer John Saw highlighted his company’s continued improvements in the Rootmetrics report. “We’re excited to see that the Sprint LTE Plus network shows year-over-year improvement,” Saw wrote in a blog post. He also pointed to June data released by Ookla showing Sprint’s national average download speed increased by 20%, best of all the carriers, since January.
AT&T t had no comment ahead of the report’s release.