Is your carrier overbilling you for mobile data?

The smartphone revolution has produced a new practice among mobile users: we’ve started counting megabytes. With a few unlimited plan exceptions, most mobile data services are now capped, requiring us to keep a close eye on our usage. But are our carriers counting bytes the same way we are?

According to an MIT Technology Review report, they’re not, and as you might expect the discrepancy in byte counts come out in the operators’ favor. The carriers aren’t exactly sticking their thumb on the scale, but they’re billing you for all data they ship you, rather than the data you actually receive, UCLA computer scientist Chunyi Peng told the Review.

Peng and her research group built a custom app for Android(s GOOG) that counts bytes actually received on the device and then tested it over two unnamed U.S. operators’ networks. They were billed for 450 MB of data that they didn’t actually consume. Over a typical phone, carriers tend to over-count data by between 5 percent and 7 percent – not a huge number, but a significant one if it pushes you over your cap, triggering either an automatic overage fee or throttling policies that limit your speeds, Peng concluded.

The reason for the discrepancy has to do with where carriers count data. Peng explained to the Review that carriers start tracking usage as it leaves the network core, not when it actually hits the phone. The problem is the fickleness of mobile connections means customers often move in and out of coverage or experience dips and spikes in bandwidth. Not all data requested actually makes it to the phone, but the carriers still charge you for the delivery attempt. The issue is particularly bad with audio and video streams, which keep on coming even if the radio link to the phone disappears.

Considering that video is expected to be the biggest growth driver in mobile data, this problem is only to get worse. Consumers have every right be upset. It’s true carriers are making the effort to deliver that data, and it’s arriving all the way up the base station. But that’s hardly a justification for over-counting. If the network is too congested or cellular coverage is lost that’s ultimately the responsibility falls on the carrier, not the consumer.

Interestingly, Peng and her team also found away to bypass the data toll booth, by disguising application traffic as DNS requests that don’t count against plans’ data buckets – at least on the two operators tested. Peng told the Review that she was able to create an app that exploited that policy racking up 200 MB of data usage that went uncounted on her bill.

Abacus Photo courtesy of Shutterstock user Tomas Urbelionis Photo