iphone use 3g when wifi is present

[apd8]

I just noticed that my iphone sent some data over 3G even wifi network was present.
I looked at at&t bills and the time stamps showed that iphone used 3G even at night when I was at home and had my wireless router on all the time.

Anyone has this experience? This may be an old issue, but I'm kinda new.
Thanks.

 

[Givmeabrek]

Error

 

[JamesMB]

Depending on what you are doing, the phone will use the cellular data network instead of WiFi. MMS is just one example.

 

[Applejuiced]

I just noticed that my iphone sent some data over 3G even wifi network was present.
I looked at at&t bills and the time stamps showed that iphone used 3G even at night when I was at home and had my wireless router on all the time.

Anyone has this experience? This may be an old issue, but I'm kinda new.
Thanks.

The AT&T system usually accumulates all your daily data usage at night and posts it on their system then. Just because it shows that you used 12MB or whatever at 11PM it doesnt mean that you used it at that exact time. Its not that accurate, you could have used it during the day etc...

 

[jav6454]

Every iPhone disconnects and connects to the Wi-Fi network. Even when resting charging the iPhone speaks thru 3G instead of Wi-Fi. Notice, when you wake your iPhone up from sleep in a Wi-Fi area, its on cell network and 2-3 secs later its on Wi-Fi.

This is a power saving feature Apple built into every iPhone since 2007.

 

[iApples]

Sometimes if your WiFi signal gets weak, 3G will kick in. It's happened to me a few times. I always tend to notice it while downloading big games from the App store. And then I wonder why I go through my crappy data plan so fast.

 

[apd8]

The AT&T system usually accumulates all your daily data usage at night and posts it on their system then. Just because it shows that you used 12MB or whatever at 11PM it doesnt mean that you used it at that exact time. Its not that accurate, you could have used it during the day etc...

This is totally not true, at least from what I see on my bills. The usages have never been accumulated and the bills show from even a few to thousands kB. Several time stamps are shown within an hour. I do believe that they must be accurate for the time since I suppose that they use a similar timing system for calling where the accurate time does matter.

I find the replies from jav6454 and iApples are more convincing. Thanks guys.

 

[Applejuiced]

This is totally not true, at least from what I see on my bills. The usages have never been accumulated and the bills show from even a few to thousands kB. Several time stamps are shown within an hour. I do believe that they must be accurate for the time since I suppose that they use a similar timing system for calling where the accurate time does matter.

I find the replies from jav6454 and iApples are more convincing. Thanks guys.

That's what happened with other members and AT&T reps have confirmed that also.
There is a delay on posting your data usage on their site and to go thru their system. Data usage is not real time accurate to the minute or even to the hour and they do post later.
Believe what you want though.

 

[LapsangSouchong]

Track down the "phantom usage" thread. Lots of folks reporting the same thing.

 

[apd8]

That's what happened with other members and AT&T reps have confirmed that also.
There is a delay on posting your data usage on their site and to go thru their system. Data usage is not real time accurate to the minute or even to the hour and they do post later.
Believe what you want though.

I do believe that it could happen sometimes but not all the time. I noticed that the data usage is not posted real-time, but when it's posted, the time stamp shows the usage time, not the posting time (otherwise it should show accumulated usages).

Another reason why I'm not convinced is that I spend most of the day in wifi areas - at my office, inside the office building or at home. My trip from home to office takes 5 minutes and I do not go out very often. So, I should not be outside wifi areas for long/often while the bill shows several usages per day.

 

[JamesMB]

I do believe that it could happen sometimes but not all the time. I noticed that the data usage is not posted real-time, but when it's posted, the time stamp shows the usage time, not the posting time (otherwise it should show accumulated usages).

Another reason why I'm not convinced is that I spend most of the day in wifi areas - at my office, inside the office building or at home. My trip from home to office takes 5 minutes and I do not go out very often. So, I should not be outside wifi areas for long/often while the bill shows several usages per day.

Even if your phone is on wifi, it will still use cellular data to ping the local tower every few minutes. In fact, if you have the phone close to a speaker, you can tell every time it pings.

 

[apd8]

Even if your phone is on wifi, it will still use cellular data to ping the local tower every few minutes. In fact, if you have the phone close to a speaker, you can tell every time it pings.

This is something new to me. Thanks.

 

[Daveoc64]

Even if your phone is on wifi, it will still use cellular data to ping the local tower every few minutes. In fact, if you have the phone close to a speaker, you can tell every time it pings.

It doesn't use any data when it's doing that.

As for the real reason why the OP's phone is using 2G/3G rather than Wi-Fi is simple.

The iPhone will only stay connected to a Wi-Fi network if any of the following are true:

- The iPhone screen is "on" (not in sleep mode)
- The iPhone is connected to a power source
- The iPhone isn't receiving a cellular data signal
- An Application is using the Wi-Fi network (e.g. Pandora streaming music with the screen switched off)

The above also assume that a Wi-Fi network is available to connect to and that the phone is using iOS 4.0 or later.

MMS does use cellular data, but that shouldn't be billed with regular data usage. Visual Voicemail also uses cellular data, but I'm not sure how AT&T bills that.