The war between T-Mobile and Verizon over network performance has taken a new twist. In our latest round of tests, Verizon has regained lost ground in 4G speed, bringing it even with T-Mobile. Meanwhile T-Mobile has continued to narrow the gap with Verizon in our 4G availability rankings, putting the Un-carrier within a stone's throw of matching Verizon signal for signal. In no report has the clash between the two operators been so heated. Either Verizon or T-Mobile won or shared every single national award in our report.

In our third State of Mobile Networks report for the U.S., OpenSignal parsed 4.6 billion measurements collected by 169,683 smartphone users in the fourth quarter of 2016 to gauge the 3G and 4G performance of national operators AT&T, Sprint, T-Mobile and Verizon. We also examined 4G speed and availability in 36 of the biggest cities in the U.S. First, let's look at the tight race over network speed.

It's a draw

The LTE speed race between T-Mobile and Verizon has long been a close one, but in our last U.S. report T-Mobile held the edge. That narrow lead, however, disappeared in our latest round of testings. We measured average LTE download speed on T-Mobile at 16.7 Mbps and on Verizon at 16.9 Mbps, results close enough to produce a statistical tie. While T-Mobile LTE speeds essentially held steady in our tests since our last report, we recorded a 1 Mbps bump in Verizon's average performance.

We also measured a 1 Mbps boost in AT&T's 4G speeds between reports, but our average download measurement on Sprint's LTE network dropped slightly. For 3G, we saw the typical huge gap between CDMA and HSPA connection speeds. T-Mobile won our 3G speed award with an average download of 4 Mbps, followed by AT&T with an average of 3 Mbps, but 3G is becoming less of a factor in gauging operators' overall performance in the U.S. as LTE signals become widespread. All four operators' overall speed scores — which measures the typical download speed our users experience across all data networks — were only a megabit or two slower than their 4G speeds in our measurements. T-Mobile's fast HSPA+ network gave it a slight bump in our overall speed metric, but T-Mobile and Verizon were still in a dead heat in our overall category, tying with an average of about 14.6 Mbps.

In August, Verizon announced it was implementing an LTE-Advanced upgrade across its 4G network, stating it would boost peak speeds by as much as 50%. While OpenSignal tracks average speeds, not peak speeds, we definitely see evidence of Verizon's upgrades showing up in our metrics. In addition to our measured uptick in national 4G speeds, we recorded big increases for Verizon in several of the markets in our U.S. city breakdown. For instance, our tests in New York City showed that Verizon's average LTE download jumped from 17.4 Mbps to 22 Mbps since the summer, which allowed Verizon to leap over T-Mobile for our speed prize in the Big Apple.

Verizon ranked highest in speed in 14 of the 36 cities we analyzed, compared to four cities for T-Mobile and one for AT&T, but in seven other metro areas the speed contest between Verizon and T-Mobile resulted in a statistical tie. In three other cities we recorded a draw between AT&T and either Verizon or T-Mobile, while in the remaining markets, we saw ties between three or more operators.

A tightening race over 4G reach

Verizon has long been proud of its network reach, and its dominance in 4G availability continued in our latest tests. Rather than track geographic coverage, our availability metric measures the proportion of time our users can access a particular network. In Verizon's case, our testers were able to find an LTE signal 88.2% of the time, earning it once again our award for best 4G availability. For the last year, however, T-Mobile has been climbing up our rankings. In our last report, T-Mobile surpassed AT&T, and in our most recent tests T-Mobile has closed the gap separating it from Verizon to within 2 percentage points. Users were able to connect to the T-Mobile network 86.6% of the time, while we measured AT&T's 4G availability at 82.2%.

Just as Verizon has been boosting its LTE network capacity and performance, T-Mobile has been expanding its LTE footprint and reach, tapping low-frequency airwaves that propagate further and penetrate deeper into buildings. But T-Mobile isn't the only one providing a more consistent LTE signal. Since our last U.S. report, all four national operators saw not insignificant improvements in our 4G availability metrics, but the biggest improvement we measured was on Sprint's LTE network. Sprint's 4G availability jumped from 69.9% in August to 76.8%. Sprint, however, is still last among the four national operators in our availability rankings, but it's now much closer to bridging the once yawning chasm between itself and the other three.

In our 4G availability breakdown of U.S. cities, Verizon emerged as the dominant operator in our tests. It won our award for best 4G availability in 20 of the 36 markets we analyzed, and it was the only operator to win any of those awards outright. In the remaining 16 cities, Verizon was also extremely competitive, drawing statistically with one or more operators for the top ranking.

The final metric we looked at was latency, which measures the response time of a data connection. Networks with lower latency generally start loading web pages and videos faster. A low latency also means less lag time in real-time communications apps like voice over LTE, which is beginning to displace 2G voice services on U.S. operators' networks. In our last report Sprint won our 4G latency award and T-Mobile won its 3G counterpart. In our latest tests, T-Mobile held onto the 3G award with a latency of 115.8 milliseconds, but Verizon walked away with our 4G prize, averaging 59.8ms.

Improving by increments

While we didn't track any major shifts in our metrics from one report to the last, we're clearly seeing steady increases in speed and availability across the board. The U.S. has long been one of the world leaders in providing consistent LTE access, and it's only adding to its elevated status each year with gradual gains in 4G service availability. In several of U.S. cities we analyzed, we were able to find an LTE signal more than 90% of the time on one or more operators' networks. As a whole, the U.S. mobile operator community had an overall 4G availability score of 81.3%, as measured in our recent State of LTE report, so it will take some work before the entire country has access to 4G connections 90% of the time. But that's a very high bar to achieve indeed. Only two countries have managed to surpass 85% 4G availability: Japan and South Korea.

In terms of LTE speed, though, the U.S. still lags the global mobile community, despite incremental improvements in performance. We see speeds on the increase at operators like AT&T and Verizon thanks to new upgrades and new 4G spectrum, and in individual cities operators are pushing well beyond 20 Mbps in our download tests. But in our nationwide tests, all four operators fell short of the global LTE download average of 17.4 Mbps. While U.S. operators are starting to take advantage of new LTE-Advanced techniques, they haven't pushed the limits of that technology to the extent that we have seen in Europe, East Asia and even neighboring Canada. We're seeing average LTE-Advanced speed in many of those countries exceed 25 Mbps — and in some cases 40 Mbps. Some LTE-Advanced networks are clearly more advanced than others.