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Sleeping iPhones Send Phantom Data
Stoobalou writes with a story that got started earlier this month when iPhone users in the US and the UK noticed that their phones seemed to be sending large data bursts via 3G overnight. (Providers are ending unlimited contracts, so iPhone users are paying more attention to how much data they are using.) The discussions began on MacOSRumors and an Apple discussion forum. Thinq.co.uk makes this guess as to what is going on, but doesn't offer much in the way of substantiation: "The simple fact of the matter is — as far as we can tell — that the iPhone's push notifications and other small transfers of data are totted up throughout the day and the total for all of those notifications is added up after dark and sent to your airtime provider while your phone is sleeping. If these tiny amounts of data were individually listed your bill would probably be the size of a telephone directory. The reason it is using the 3G network rather than Wi-Fi is that all iPhones up to and including the 3Gs turn off Wi-Fi push functionality while the phone is in sleep mode, in order to preserve battery life. The iPhone 4, incidentally, has better power management so will not need to do this."
If you are extremely worried about this, just put your device into "airplane mode" before putting it to sleep. It won't try to talk to anything at all.
If you're only slightly worried about it, well, OS4 has an option to disable using the cellular connection for data at all, forcing all data over wifi but still leaving the ability to receive SMS and phone calls on. (OS4 brings more tools for managing your bandwidth use than previous releases ever had.)
We have about 150 iPhones for corporate use and we have had to return 8 so far because of bad battery life. We have had more reports of deteriorating battery life from approx. 25 more users that doing a full restore to the phone and NOT applying the backup, just rebuilding the phone manually, has resolved their battery life back to original capacity.
The key is not to restore the backup created immediately before the restore in iTunes. Even though all of the push and antenna settings are set correctly, there is still something in the OS that makes the battery drain.
The worst one I've seen so far would drain 8% every 5 minutes; you could literally watch the battery percentage count down like a timer. Doing a restore of the OS fixed it.
Turns out they don’t, it’s just a total of use from the entire day that accumulated a lot of tiny data transfers made by the iPhone’s system which are too numerous and trivial to itemize on the bill.
Do we know this? TFA presents that as a speculative explanation, but offers no evidence. All these Apple types are relying on what their telephone bill says -- which seems kinda naive, given that cellphone carriers are not exactly known for their truthfulness.
What we really need is an RF geek to set up some equipment to monitor an iPhone's overnight radio activity, and give us some hard data to consider.