How Carriers Miscalculate Your Data Usage

Every month, your carrier calculates how much data you've crunched through on your cell phone and charges you accordingly. But a new study suggests that they might not be adding things up quite right.

Technology Review reports that computer scientists at University of California, Los Angeles, have been probing the systems used by "two large U.S. cell-phone networks"—no names are named—to assess how accurately they calculate data usage. Using data-logging software, the team kept tabs on how the carrier's calculations squared up with their own.

They found that, while carriers often get the calculations right, they often over count. In particular the team found that over counting seemed to happen most when using applications that stream video or audio, or when coverage was weak or unreliable.

The problem boils down to the fact that carriers count data that leaves their network, and not what's received by your phone. Obviously, the two don't always match.

While the effect isn't huge, with typical discrepancies being somewhere between 5 and 7 percent, that's definitely enough to accidentally nudge you over your monthly data allowance. With AT&T and Verizon both charging $15 for straying into each new gigabyte of data over and above your cap, it could even be costing you real money.

The solution, of course, would be to tweak the measurement systems so that they count how much data actually makes it to your phone. Whether that's ever going to happen, though, is a completely different story. [Technology Review]