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Analyzing the impact of unlimited data in the US

Last week OpenSignal unveiled a new experimental metric called average peak speed, which is designed to gauge a network’s full data connection capabilities under optimal conditions. We kicked off our analysis of peak speed with a look at India’s four nationwide LTE operators, but in conjunction with OpenSignal’s State of Mobile Networks: USA report, released today, we’re applying our peak speed metric to the U.S. big four. We think that peak speed can provide some additional insight into what’s happening at the moment in the U.S. with the resurgence of unlimited data plans.

Before jumping into the analysis, I should explain how we define peak speeds and how we calculate the metric. While our 4G speed metric measures our user’s typical everyday experience, peak speed measures an operator’s 4G connections at their best -- when devices are able to access the full capacity of the network unfettered by congestion or other technical limitations. You can think of average speed as the everyday experience of driving a car in traffic, while peak speeds are what your car can achieve when the highway is empty and you’re free to lay on the gas pedal.

We calculate average peak speed by examining data only from devices that have conducted multiple automated speed tests in a three-month test period. We extract the fastest speed test from those devices and then toss out the bottom 95% of the results, leaving us with only the top 5% of the fastest speeds we’ve collected from our crowdsourced community. The average of that top 5% is our average peak speed metric. This metric isn’t measuring the theoretical peak speed of a network as those speeds are quite simply unattainable. Nor are we claiming this measurement is the topmost speed a device would ever experience on a particular operator’s network. But we feel average peak speed is an accurate measure of what consumers might really experience when the network -- to continue the car analogy -- is firing on all cylinders.

We ran average peak speed for the April-June timeframe, which is the same test period we used for our U.S. report. You can see the results below:

The first thing that sticks out in this chart is that Verizon and T-Mobile are locked into a tie for peak speed at 104 Mbps. What that tells us is that Verizon and T-Mobile’s are evenly matched when it comes to capacity and both are able to support extremely fast connections when conditions are optimal. That isn’t a surprise. For the last two years we’ve seen Verizon and T-Mobile engaged in a heated battle for fastest 4G speed in our measurements. But in the current U.S. report we saw a marked change. Our 4G speed results for Verizon dropped by 2 Mbps, allowing T-Mobile to leap ahead of Big Red in our rankings. What happened? Unlimited plans happened.

In February, Verizon and AT&T reintroduced unlimited data options, and we saw an immediate impact in our metrics. Since March, average 4G and overall speeds for both operators began dropping for both operators in our test results. In our latests results, Verizon’s average peak speed was 7 times faster than its average 4G download speed of 14.9 Mbps. In comparison, we recorded T-Mobile’s average peak speed as 6 times faster than its average 4G speed of 17.5 Mbps. That means T-Mobile customers were able to get closer to their network’s optimal experience than Verizon’s customers on an everyday basis. Here’s another way to interpret the data: While Verizon and T-Mobile’s networks have comparable capacity, the typical T-Mobile connection was able to access more of that capacity than the typical Verizon connection.

The most likely explanation for this sudden drop in average speeds compared to peak speeds is that Verizon’s network is experiencing more congestion due to its new unlimited plans. By opening up the data spigot, customers start consuming more data more often, forcing them to vie against one another for more capacity on each cell site. The more data demand there is on a network, the more average speeds will drop, regardless of the network’s technological capabilities.

Even though Verizon appears to have taken the biggest hit from unlimited plans in the last four months, our results show that Big Red has still managed the increased demand well, at least compared to its other two competitors. Our measurements on AT&T showed peak speeds 7.5 times faster than typical 4G speeds, while Sprint’s peak was 8 times higher than its average.

At 97 Mbps, our average peak speed result for AT&T was only 7 Mbps slower than Verizon and T-Mobile’s peaks, indicating Ma Bell’s networks are technically capable of supporting speeds close to Verizon and T-Mobile. If AT&T were to boost its capacity -- allowing customers to access a greater share of the network’s bandwidth -- it could become competitive in our 4G speed rankings once again. Sprint is different story. It not only had the lowest peak speed in our tests, Sprint also had the biggest gap between peak and average speeds. It would probably take a major network upgrade before Sprint could match its competitors megabit for megabit.