Mystery iPhone Transmissions a Cause for Concern?

What started out as a cause for concern among some iPhone users appears to be a relatively benign function of how the device interacts with the AT&T network.

Users checking their data usage had noticed their iPhone was sending a lot of data out when it should have been in idle, stand-by mode. This led to active discussion and speculation on various Web sites such as MacRumors.

A similar thread discussed the issue on Apple's official forums. There were a number of theories, some more tinfoil than others, as to why an iPhone sitting unused would suddenly start to transfer as much as 60MB of data, usually at around 2 or 3 AM, according to those who determined their iPhone was engaging in such activity.

People eventually determined that the iPhone's push notifications and other small amounts of data are stored up during the course of the day and then sent to Apple (NASDAQ: AAPL) and/or AT&T (NYSE: T) early in the morning. It uses a 3G transmission because the iPhone turns off Wi-Fi push functionality while the phone is in sleep mode to preserve battery life.

Apple did not respond to requests for comment.

But an AT&T spokesperson told InternetNews.com that because of the way certain smartphones work, if they are left idle during the day, they sometimes won't report anything back to AT&T's network for several hours. "In those cases, the billing system registers all of the usage from that period as one line item -- but that's reflecting data that they've actually used. That's separate from how it looks when they go to check their data usage online," the spokesperson said in an e-mail.

The spokesperson went on to explain that the data transmissions that customers see being sent to its network are the reporting of data usage. A person may download a few kilobytes of e-mail data in the middle of the day, but the phone won't inform the AT&T billing network until the evening, when traffic and usage is lower.

This is especially the case for people who don't have regular 3G connectivity throughout the day, where the phone has to gather up all of the day's data use and send it to the network, and matches the experiences described by users on the message boards.

Users on the Apple and MacRumors boards had expressed concern that these mystery data transmissions would chew up their data plan cap, but AT&T said that the only thing being transmitted is a report on daily amount of data usage, and people should not be concerned with being charged twice for data transmissions.

Andy Patrizio is a senior editor at InternetNews.com, the news service of Internet.com, the network for technology professionals.