iPhone sending large data files over cell network at night

I recently got an iPhone 4s. I try to keep an eye on my data usage so I don’t go over my limit and get charged. I’m usually in a WiFi area so it hasn’t been a problem. However, looking at the data sent, I’ve noticed that almost every day between 12am and 1am there is a large (2-4 megabytes) amount of data going over the cell network. This is while my phone is in my home with a WiFi connection. Examples from the last few days:

3/12 12:52AM, 4,140KB
3/10 12:35AM, 2,284KB
3/9 12:26AM, 2,871 KB

Strangely, on 3/11 it was only 14KB.

  1. Why is it doing this? I’m wondering if it’s some kind of Apple spy program keeping track of my activities.

  2. Is there any way to find out if one of my aps is doing this, and which one?

  3. Why is it going over the cell network when it has a WiFi connection available?

Do you have an iCloud backup set up?

Where are you getting the data amount information?

One way would be to look at your computer’s activity during Midnight and 1AM (in real time). On Apple computers, I don’t know how that’s done, but on a PC, XP, the Task Manager has a graphic display option for network traffic that is just the ticket. The minute the traffic spikes, check the processes that are running and what the usage stats are.

Did you read the OP? He’s talking about an iPhone, not a Mac. There is no task manager or network monitor.

As for answers, I got nuthin’.

No, I haven’t activated the iCloud. It is set to sync automatically over WiFi, but that’s obviously not what’s happening here.

AT&T website.

It’s apparently an accounting thing.

Yes, I read the OP. I have no idea how an iPhone is connected to anything but everything in my house is funneled thru the Internet tube so I can see all traffic from all devices. I guess it doesn’t work that way elsewhere.

I seriously doubt that your cell phone data goes through the “Internet tube”…

AFAIK most smartphones turn off the wifi radio when they’re in standby, but keep the cellular radio active. So this chatter would go over 3G since the phone’s likely locked or in standby.

Read the comments section, they don’t agree with the AT&T explanation.

That’s not my experience at all. I expect to be able to walk into a room with my phone in standby and have it camp on a known wireless network.

This is certainly how the phones we made at my last job, which was a major US cell phone designer/manufacturer.

If I’m camped on a WiFi network (or a known one becomes available and I have it set to camp automatically), all data is going to go over that. Both the end user and the carrier tend to prefer it that way, because it’s faster, cheaper, and doesn’t take up other people’s bandwidth.


Actually, mine doesn’t, but a friend’s does. There’s a gadget Cellcom supplies for low-signal areas where your cellphone communicates with a local station (in your house), then the signal is routed thru your cabled-Internet connection. It’s the only way he can use his cellphone at home.

Yes, a Microcell.
They’re pretty uncommon, but I know people who have one.

my GSM Galaxy nexus will camp on wifi when locked if data is being actively used. However, if data is not being actively used it will turn off the wifi radio after some amount of time and come back on after a very short delay when I unlock the phone.

I believe my Iphone 3gs did the same as well.

2 data points for what it’s worth.

Not to go too off-topic, but T-Mobile has a feature on many (all?) their smartphones that will route calls over WiFi, without any additional hardware like a microcell.

Is that not just putting the wifi radio into a reduced power state, rather than “off”, so that any app which occasionally polls for data, or an incoming push packet I guess, will put the wifi back into full powered state to handle the data transfer, meaning that data is still handled over wifi when the phone is locked?

(I’m clearly no expert though :slight_smile: )

@Baron GreenBack

This does not seem to be the case. I have a VOIP app that loses it’s connection in Wifi mode when I lock the phone, but doesn’t do so when I use 3/4g only.

I’m not sure what is happening, but wifi definitely appears to turn completely off on my phone after being asleep for say 30 minutes or so.

This happened to me when I first got my iPhone 3GS. According to AT&T I was using up huge chunks of data, and they kept giving warnings about going over the MB on my plan, and increasing my bill.

I went the rounds with their customer service, explaining that 1) when this data was being used I was in bed and the phone was sitting on my nightstand, and 2) it was in wi-fi mode and shouldn’t have been using 3G data anyway. I kept daily track on my online bill and compared it with my usage, and even started putting the phone in “airplane mode” at night, but the data charges kept building up.

Eventually they had me take my phone into an Apple Store, where they ran some diagnostics on it and gave me a new phone. Haven’t had any problems since. And yes, they did reverse the excess data charges.