Wi-fi or LTE data when asleep?

Discussion in 'iPhone' started by willdude, Sep 27, 2012.

  1. willdude macrumors member

    Joined:
    Jul 16, 2010
    #1
    So here's a maybe-stupid question which I think may apply to this question of battery life vs. signal strength. When you are in a wi-fi area and wake up the screen and unlock the phone, you see that the wi-fi icon isn't initially there but then pops up, seemingly as it connects. Does that mean that, while the phone is asleep, it's not connected to wi-fi (unless you left some stream going), and any passive data usage it does -- iMessage, checking for App Store app updates, etc. -- are actually done over the cellular data network, and not wi-fi?
     
  2. Daftbrush macrumors newbie

    Joined:
    Sep 25, 2012
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    UK
    #2
    Wi-fi or LTE data when asleep?

    I've noticed the same on my iPhone 5 but not on my iPhone 4 or my wife's iPhone 4 (both running iOS6). This means I'm getting no automatic iCloud backups overnight.

    Really not sure if this is a hardware or software issue.
     
  3. SandboxGeneral Moderator

    SandboxGeneral

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    #3
    You can check if your overnight backups are occurring.

    Settings --> iCloud -->Storage & Backup.

    Scroll to the bottom and it should tell you the last time it was backed up.
     
  4. jredecop macrumors 6502a

    Joined:
    May 20, 2009
    #4
    Yup, that's what I've been thinking too. But all of my devices have been this way. I've never seen a wifi symbol up right on unlock, takes a second or so. And it can't be connecting to wifi, receive iMessage (or whatever) and disconnecting again.
     
  5. Daftbrush macrumors newbie

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    Sep 25, 2012
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    UK
    #5
    Yes, I've been checking this every morning since I bought the phone that's how I know it's not backing up unless I manually do it.
     
  6. auero macrumors 65816

    Joined:
    Sep 15, 2006
    #6
    Correct, the wifi connection drops after x amount of minutes after your phone locks. I think it's 10-15 but I'm not certain.
     
  7. Daftbrush macrumors newbie

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    Sep 25, 2012
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    UK
    #7
    So if the connection drops, how does the automatic back up to iCloud happen. I always thought that when it's charging and locked the wifi stays connected?
     
  8. netnothing macrumors 68040

    netnothing

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    NH
    #8
    This is one of those Apple mysteries that has always made me think. Most people say that when the phone goes to sleep....WiFi is turned off. Most people see this when waking their phone, you see the cell data icon first, then it switches to WiFi.

    The thing I don't know for sure is.....what about things the phone can do while asleep? For example, checking mail? Does it switch on WiFi to check for mail? If you are streaming Pandora....and let the display sleep....does WiFi turn off?

    Seems to me it shouldn't.

    As for iCloud backups....Apple is specific in that they say no iCloud backup will take place unless:

    -is connected to Internet over Wi-Fi
    -is connected to a power source
    -has the screen locked

    http://support.apple.com/kb/ht4859

    In fact.....you'll notice that you can't even force an iCloud backup unless you are on WiFi......the button isn't active while on the cell network.

    So unless there is a bug in the software....no ones iCloud backup should ever go over WiFi.

    -Kevin
     
  9. Xgm541 macrumors 6502a

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    May 3, 2011
    #9
    It turns on wifi when needed. To check mail, pandora, etc
     
  10. willdude thread starter macrumors member

    Joined:
    Jul 16, 2010
    #10
    One thing I can accurately determine, though, is that for a WPA Enterprise wi-fi network, the phone does not re-authenticate when you wake it up and the wi-fi symbol pops up. I'm not familiar with the nitty-gritty of wi-fi itself, or how and when the iPhone sends and receives data, but my guess is that it's simply putting the wi-fi chip "to sleep", and when data access it needed, it will wake up the chip and do so through wi-fi.

    Which brings me to my original question about this, stated elsewhere: since LTE doesn't do voice, why does the phone even bother to stay connected to LTE when you have wi-fi? Wouldn't it save battery to just go to 3G/4G in that case, particularly for those of thus that have weaker LTE signal than 3G/4G signal?
     
  11. SandboxGeneral Moderator

    SandboxGeneral

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    #11
    You have a good point, and I don't think anyone here has the answer. I noticed that my 4S, when awoken, defaults to 4G (HSPA+) and not WiFi. I am in agreement with you that it seems logical to stay on WiFi to save battery life and data usage.

    We can only hope that Apple changes this particular behavior in a future update.
     

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