Over the past year, the growth in the popularity of smartphones has led the largest U.S. mobile carriers to replace unlimited data plans with ones that place caps on data usage, and charge extra for exceeding those limits.
Working with three colleagues at the University of California, Los Angeles, computer science PhD researcher Chunyi Peng probed the systems of two large U.S. cell-phone networks. She won’t identify them but says that together they account for 50 percent of U.S. mobile subscribers. The researchers used a data-logging app on Android phones to check the data use that the carriers were recording. The carriers were found to usually count data correctly, but they tended to overcount—and hence potentially overcharge—when a person used applications that stream video or audio, and particularly when coverage was weak or unreliable.
The researchers determined that even typical use of a phone could lead the data to be overcounted by 5 to 7 percent, Peng says. That could cost customers money. The two largest U.S. wireless networks, AT&T and Verizon, both charge a user $15 for straying into each new gigabyte of data over the data cap.
The problem stems from the way networks count data use. They count data as it leaves the heart of a company’s network and sets out on the journey to the mobile tower nearest a subscriber. That means data is counted whether a phone receives it or not. If a person on a bus is streaming video but enters a tunnel and loses her connection, for example, video that she never sees will already have been counted toward her plan.