Aug 20, 2019 9:44 AM

Think Video on Your Phone Is Slow? It’s Not Your Imagination

A study by Northeastern University researchers found that major wireless carriers sometimes limit video to DVD-quality, even on some “unlimited” plans.

A new report by researchers at Northeastern University confirms that the nation’s four major wireless carriers throttle at least some video content on their networks, and suggests a few workarounds for those who want the best possible video quality on their mobile devices.

AT&T, Sprint, T-Mobile, and Verizon all note on their websites that their cheapest "unlimited" plans only allow DVD-quality video. For example, AT&T's cheapest advertised unlimited plan, the $40 AT&T Unlimited & More plan, only allows you to stream video at 480p resolution---DVD quality. If you want high-definition streaming, you'll need to pay an extra $8 a month for the AT&T Unlimited & More Premium service.

The Northeastern report comes a little more than a year after Obama-era Federal Communications Commission rules that prohibited telecom companies from throttling, blocking, or otherwise discriminating against lawful content lapsed, after the Trump-appointed FCC voted to repeal them.

The report, based on crowdsourced data from the researchers’ mobile app, suggests that carriers limit video quality by throttling the speeds of video connections. For example, the researchers found that AT&T capped video connections at 1.5 Mbps on the cheaper unlimited plan, as a way to limit users to “DVD quality” streams.

But throttling is a blunt way to limit video quality. YouTube and some other video providers will serve 480p or lower resolution video instead of high-definition video if they detect that a user has a slow connection. In cases where a video provider doesn't offer a lower resolution alternative, you might simply end up with a choppy connection instead of a lower quality stream.

Google Fi is the only US-based mobile service for which the researchers gathered data that didn't throttle video streams. Google Fi essentially resells service from Sprint and T-Mobile. But it doesn't offer unlimited plans. Instead of a flat monthly fee, you pay for the amount of data that you actually use, meaning Google has less incentive to throttle video streams. Other services that don’t offer unlimited plans might not throttle data, but some do. For example, a spokesman for Ting, a wireless reseller that uses T-Mobile and Sprint's networks, says Ting doesn't throttle any connections, but that T-Mobile throttles Ting connections.

The FCC and the Department of Justice have both signed off on a merger between T-Mobile and Sprint, which will reduce the number of major US mobile carriers from four to three.

Carriers that limit the quality of video often do so by scanning data in the transmission identifying it as a video. To get around that, you can try using a virtual private network (VPN). These services route all your internet traffic through their own servers over encrypted connections so that carriers can't tell whether you're streaming videos.

Sometimes, carriers aren’t the only ones to blame for lower-quality video. The report notes that some apps, including Amazon and Netflix, stream video at a lower resolution than 480p by default, but you can usually change this. And even “unlimited” plans often have limits on the total amount of data you can download over a specific period. For example, the fine print for Verizon's Do More Unlimited plan says you can use 50GB of data per month, after which your connection might be slowed in times of congestion.

Blunting Traffic

Throttling connections based on specific types of content violated the FCC's Obama-era net neutrality rules, but the Republican-controlled FCC voted to jettison those rules in December 2017. Northeastern University researcher David Choffnes told WIRED last year that his team found that the four major carriers began throttling video well before the FCC's rules expired in June 2018.

A few states have passed laws aimed at preserving net neutrality. California's net neutrality law is in legal limbo, but one in Washington state is now in effect.

However, the FCC's old rules and the newer California and Washington state net neutrality rules allow internet providers to reduce connection speeds for "reasonable network management" purposes. Verizon has previously argued that its resolution restrictions fall under this loophole because most people can't actually perceive the difference between different resolutions on small smartphone screens. The FCC didn't press the issue before the rules went out of effect. Sprint, T-Mobile, and Verizon did not respond to requests for comment. A spokesperson for Washington’s attorney general declined to comment on whether carriers violate state net neutrality law.

AT&T's website acknowledges that it caps video connections on its Unlimited & More service at 1.5 Mbps. But in a statement, an AT&T spokesperson disputed the study's findings. "We don't throttle, discriminate, or degrade network performance based on content," the statement says. "We offer customers choice, including speeds and features to manage their data. This app fails to account for a user’s choice of settings or plan that may affect speeds.” AT&T did not respond to questions about why the company believes that video connection caps on Unlimited & More plans don't count as discrimination based on content.

Testing for Throttling

The Northeastern University researchers found no evidence that major home internet providers in the US, including Comcast, throttle content. But the report notes that it's possible they missed some throttling. Through their mobile app, the researchers gathered data from 126,249 users across 183 countries and regions and found 30 carriers around the world throttle video in some way.

The researchers rely on an app called Wehe that you can install on your phone from the Apple App Store or Google Play Store. The app downloads data cloned from several popular apps, including YouTube, Skype, and Netflix, from Wehe's own servers. Then the app downloads random data from the same servers and compares the data-transfer rates. Wehe tracks how quickly the cloned data downloads, compared with the random data. The researchers also confirmed the findings gathered from Wehe app users in their own lab using prepaid plans from the four major carriers. The drawback to this method is that it won't detect other techniques to throttle content, such as targeting specific IP addresses used by apps. Because wireless network signals can vary, the researchers only report throttling when at least two pairs of tests find "differentiation" between the random data and the cloned data.

Last year, the same research group found data suggesting that Sprint also throttled Skype connections. Sprint denied that it throttled the service. The new report found no evidence that Sprint has throttled Skype since October 2018.