A recent study by four UCLA computer science researchers documents what some wireless data customers have long suspected -- that users can be charged for wireless data they never received.
In the most extreme case of overcharging, an unnamed carrier charged the researchers for 450 MB of data that they didn't receive.
In the study ( download PDF), the researchers also describe their hacking into Domain Name System servers at two unnamed wireless carriers to be able to send data at no cost.
The researchers said they transferred 200 MB from an Android device for free by using the DNS hack, and added that they could have sent as much as they wanted.
The study team was headed by UCLA computer science doctoral candidate Chunyi Peng.
In both the cases of overcharging and undercharging, the study concluded that "the root causes lie in lack of both coordination between the [carrier] charging system and the end device, and prudent policy enforcement by certain operators."
The UCLA team published a 12-page paper on the study in August. Team leader Peng presented the paper at MobiCom '12 in late August in Istanbul, Turkey.
The study didn't assess how widespread the overcharging is across entire networks.
The authors recommended that carriers make changes in network architectures to take account of data usage feedback from end user devices, and make policies ensuring that only data used is charged for.
The study noted that Cisco has proposed a form of overcharging protection.
The researchers also called for further study of the issue by the research community, noting that the data charging system used by U.S. wireless carriers "mostly works as a black box for users. Users do have questions and concerns."
One question on the minds of many customers is how to determine whether a carrier's bill overcharges for data access not received, the researchers noted.
The study looked at two unnamed U.S. wireless carriers with 3G networks, and separately compared a third U.S. carrier with two others in China and Taiwan.
The team said the results are also applicable to 4G networks such as LTE.
The tests were conducted using a free app from Google Play called TrafficMonitor to log data usage, along with a custom tool built by the UCLA team.
In terms of overcharging, the study found that accounting standards of carriers do not take feedback from end user devices. Data packets can be lost in a cellular network, and can be counted as being sent by the carrier even if it was never received by the user device, the study said.
The highest overcharge was for 7.2% more data charged for than used. That overcharge resulted from a user watching YouTube videos on a train that traveled through a long tunnel that lacked cellular signals.
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