Looks like no one’s replied in a while. To start the conversation again, simply ask a new question.

User profile for user: Spencer Simmonds
Spencer Simmonds Author
User level: Level 1
9 points

iPhone 4 using Cellular Data when on standby and connected to wifi.

This is a real strange one. I have two wifi networks, one at home and one at work. I have recently upgraded to the iphone 4 so I have lost my unlimited data tariff so I thought I would have a look at what data was being consumed on the phone. I have noticed that although I am connected to wifi on both networks, if I just leave the phone so the screen goes black and it goes into its lock mode, when I press the home button to use the phone, for a second or so it shows 3G as the connection and then after about a second the wireless logo appears. This is sort of giving the indication that when in sleep mode it is dropping the wifi connection until I start using the phone again and wifi kicks back in. Sure enough if I then check the cellular data usage it has increased. Sometimes just by 1 or 2 kilobytes on sent and received, sometimes 20 or 30 kilobytes or more on both sent and received. This is without receiving any e-mails or any apps in the background running. This is happening on both the home and work networks, but it seems to consume more data on the work network. The only difference between the two is that the work SSID is hidden but I have set that up manually so the iphone sees and connects to it without any problems. The problem seems to arise when the phone is not used and goes into locked/sleep mode.

iphone 4, iOS 4

Posted on Jul 4, 2010 9:23 AM

Reply
53 replies
User profile for user: Allan Sampson
Allan Sampson
User level: Level 10
123,677 points

Jul 4, 2010 9:36 AM in response to Spencer Simmonds

This is normal and by design, which has been the same since day one 3 years ago.

If an email account is checked for new messages, data is used regardless if any new messages are downloaded.

With iOS4, you can disable data or internet access via the cellular network entirely just as it has been possible to disable wi-fi or 3G network access in the past. You can do this when at work and at home.
Reply
User profile for user: Denethor1977
Denethor1977
User level: Level 1
0 points

Jul 4, 2010 9:52 AM in response to Allan Sampson

Allan Sampson wrote:
This is normal and by design, which has been the same since day one 3 years ago.

If an email account is checked for new messages, data is used regardless if any new messages are downloaded.


I think the question that the OP is asking is why the phone is using the 3G connection rather than established wifi. Obviously, it can't check for new messages without transferring data (inherent fact of any data transfer going back way further than 3 years ago), but why use 3G if connected to wifi?
Reply
User profile for user: Allan Sampson
Allan Sampson
User level: Level 10
123,677 points

Jul 4, 2010 9:56 AM in response to Denethor1977

I think the question that the OP is asking is why the phone is using the 3G connection rather than established wifi.


Thanks, but I know what the OP is asking.

After an iPhone has been asleep for a designated period of time when connected to an available wi-fi network, the connection with the wi-fi network will be disconnected. When waking the iPhone up, the connection with the wi-fi network is quickly re-established. This is by design to conserve battery and has been the same since day one three years ago.
Reply
User profile for user: Joe Z in VA
Joe Z in VA
User level: Level 2
457 points

Jul 4, 2010 10:22 AM in response to Spencer Simmonds

The i4 now has wake-on-wireless in which it should not be disconnecting itself despite off the charger. However while on the charger it would maintain the connection regardless of how long sleep was.

Another suggestive point of view on the cellular data used is the i4's way of pinging MMS/SMS and Voicemail. Every so often, it checks to see if you have received a text message or an AT&T voicemail message on the 3G network. Just like a normal cellular would except it's on the 3G data network as a normal phone is on EDGE/GSM services.

It also now has the ability to receive carrier updates from what I've understand in some of the blogs rather than going through Apple.
Reply
User profile for user: Spencer Simmonds
Spencer Simmonds Author
User level: Level 1
9 points

Jul 4, 2010 10:26 AM in response to Denethor1977

Thanks for the quick response. What you have said makes sense but there is no rhyme or reason to he data used. I reset my cellular data counter to zero so both sent and received read zero. I was connected to wifi and let the phone to go into sleep mode. I waited about ten minutes and sent myself the same email four times, each with a 750 kb attachment. It was sent to my .me address so it was push mail on my phone. Sure enough I checked a minute later while bringing the phone out of sleep mode and checked the data. It showed just 10kb sent but 1mb received which just doesn't tally with the 4 x 750kb mails received. It just isn't making sense.
Reply
User profile for user: Allan Sampson
Allan Sampson
User level: Level 10
123,677 points

Jul 4, 2010 10:27 AM in response to Joe Z in VA

Are you sure about data being used to ping for SMS/MMS?

I know visual voicemail messages are downloaded via AT&T's cellular data or internet network, but SMS/MMS is exchanged via the same network as calls. "Dumb" phones or phones not in the smart phone category that don't have internet access via the cellular network can exchange SMS/MMS.
Reply
User profile for user: Denethor1977
Denethor1977
User level: Level 1
0 points

Jul 4, 2010 10:31 AM in response to Spencer Simmonds

Spencer Simmonds wrote:
Thanks for the quick response. What you have said makes sense but there is no rhyme or reason to he data used. I reset my cellular data counter to zero so both sent and received read zero. I was connected to wifi and let the phone to go into sleep mode. I waited about ten minutes and sent myself the same email four times, each with a 750 kb attachment. It was sent to my .me address so it was push mail on my phone. Sure enough I checked a minute later while bringing the phone out of sleep mode and checked the data. It showed just 10kb sent but 1mb received which just doesn't tally with the 4 x 750kb mails received. It just isn't making sense.


He knows what you asked and has already answered it! 😉

I thought I had read where the iOS4 (or maybe just the iPhone 4) was supposed to be able to keep wifi connections alive while inactive. If the phone is sitting there on a charger with a wifi connection available, why use the 3G?
Reply
User profile for user: Spencer Simmonds
Spencer Simmonds Author
User level: Level 1
9 points

Jul 4, 2010 10:38 AM in response to kcpistol

Even now as we speak I am connected to a wifi network and the phone has not been asleep. I have just check and the cellular data usage has increased from my reset zero on sent and received to 49kb sent and 78kb received. I know this is a tiny amount of data but I am on a live wifi connection, I have no apps running in the background. The only emails I have received are the replies from this post on the last ten minutes. Surely it should not be using any cellular data at all.
Reply
User profile for user: Allan Sampson
Allan Sampson
User level: Level 10
123,677 points

Jul 4, 2010 10:43 AM in response to Joe Z in VA

SMS/MMS aren't exchanged via an available wi-fi network. SMS/MMS are exchange via the same network as calls. "Dumb" phones or phones not in the smart phone category that don't have internet access via the carrier's cellular network can exchange SMS/MMS. There should be no data used via a carrier's cellular data or internet network when exchanging SMS/MMS or when the carrier's server is pinged for SMS/MMS.
Reply

iPhone 4 using Cellular Data when on standby and connected to wifi.

Welcome to Apple Support Community
A forum where Apple customers help each other with their products. Get started with your Apple ID.
Learn more Sign up