FaceTime when iPhone is 'sleeping'

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Level 6

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FaceTime when iPhone is 'sleeping'

Historically, iPhones (i.e. 2G, 3G, and 3GS) when sleeping do not have WiFi connected, only mobile data. You can see this because when you wake the iPhone the status display at the top will after a second switch from E or 3G to the normal WiFi fan as it finishes waking and reconnects to WiFi.

This is a problem with FaceTime if someone is trying to make a FaceTime only call to you (without the voice stage) as if your not connected to WiFi then you cannot use FaceTime!

I had read somewhere that either the iPhone 4 or iOS 4 was changing this sleep behaviour so as to keep WiFi constantly live even when asleep and this would obviously then allow FaceTime to keep working without the need for the voice call stage.

Has anyone else seen this problem? Does anyone else remember this supposed change in sleep mode?

Note: If you receive a normal voice call this of course rings your iPhone 4 as normal and this wakes the iPhone, and you can then answer the voice call and accept a FaceTime request as you will by then have an active WiFi signal. This problem only happens when the other party is trying to make a direct FaceTime call without the voice stage and if your iPhone is asleep.

I am running iOS 4.0.1 on an iPhone 4 and do have WiFi at least when the iPhone is awake!

MacBook Pro, Mac OS X (10.6.3)

Posted on Aug 2, 2010 3:16 AM

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Answer 1

Aug 2, 2010 4:13 AM in response to John Lockwood

Does anyone else remember this supposed change in sleep mode?

The iOS 4 Software Update page lists the following as features:

+- VoIP apps can receive and maintain calls in the background or when device is asleep+
+- Persistent WiFi connection to receive push notifications+

http://support.apple.com/kb/DL1058

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Answer 2

Aug 2, 2010 4:35 AM in response to Julian Wright

Excellent point, John Lockwood!

Under settings, if you disable 'cellular data' then wi-fi is indeed persistent while the phone sleeps. This was not the case prior to iOS 4.0.

However, what really needs to happen, as you say, is wi-fi needs to be persistent when the phone sleeps even with cellular data active.

Right now, I'm trying to figure out whether the 'persistent wi-fi' feature is supposed to do the former or the latter. However, for 'direct' Facetime calls, the latter must be the case for this to be possible.

None of the documentation or other posts I've read make this subtle difference clear. Anyone?

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Answer 3

Aug 2, 2010 8:55 PM in response to Michael271

John, I've just tried a 'direct' Facetime call, and it was successful! The way it happens is that when the phone rings with a Facetime request already there, the phone wakes and finds wifi, the Facetime protocol then confirms wifi on their end, then they have the option to accept or decline.

So that's how it works. I didn't think of that either, but now that I've seen it in action it makes perfect sense.

I hope that helps!

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Answer 4

John Lockwood Author

Level 6

13,697 points

Aug 3, 2010 1:56 AM in response to Michael271

Micbarry wrote:
John, I've just tried a 'direct' Facetime call, and it was successful! The way it happens is that when the phone rings with a Facetime request already there, the phone wakes and finds wifi, the Facetime protocol then confirms wifi on their end, then they have the option to accept or decline.

So that's how it works. I didn't think of that either, but now that I've seen it in action it makes perfect sense.

I hope that helps!

When the iPhone screen goes black (sleep) it does not immediately turn off the WiFi, that takes a little longer. I have had someone several times try to do a FaceTime only call to me and when my iPhone is fully asleep it does not ring because WiFi is by then inactive. The FaceTime caller then gets a failure message.

I am not sure what you mean when the phone rings when the FaceTime request is already there. The only point of the issue is that a FaceTime only call cannot cause a sleeping phone to ring because the sleeping phone is no longer connected to WiFi.

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Answer 5

Aug 3, 2010 8:41 AM in response to John Lockwood

John,

I think this needs further testing. I just spoke to the friend I made the Facetime call to earlier today and he confirmed that his phone was asleep when I made my Facetime call. Yet, his phone woke up and he was able to accept the 'direct' (no voice call first) Facetime request from me.

There are a couple of possibilities. Perhaps his phone was charging; when this happens, WiFi stays on permanently. If it's not charging, WiFi stays active for 30 minutes before dropping the connection, so he could have been within this 30 minute timeframe when I started the call. I will clarify these points further with him.

What I meant before by the 'Facetime request being already there' is that a request to answer a Facetime call appears on the recipient's screen instead of a standard voice call request appearing on their screen.

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Answer 6

aburman1

Level 1

5 points

Aug 3, 2010 3:32 PM in response to John Lockwood

I've received direct Facetime calls many times with the phone sleeping. The phone rings as if you are receiving a voice call but when you look at the screen it asks you to accept or decline the Facetime call. The initial Facetime signal obviously wakes the phone and turns on WiFi.
Alex

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Answer 7

Aug 3, 2010 7:33 PM in response to aburman1

Perhaps the iPhone 4 uses some kind of Wireless Wake On Demand protocol to facilitate this. That might explain it.

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Answer 8

John Lockwood Author

Level 6

13,697 points

Aug 4, 2010 2:08 AM in response to Michael271

Micbarry wrote:
Perhaps the iPhone 4 uses some kind of Wireless Wake On Demand protocol to facilitate this. That might explain it.

If it does it is not working for me, further more, I and the caller both had Apple AirPort Extreme base-stations. It would be possible, indeed sensible for the wakeup data request to go over any live data connection i.e. the cell data while the WiFi signal is asleep which can then trigger a wakeup which in turn reconnects to the WiFi. However this is not working (for me).

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Answer 9

Aug 4, 2010 9:41 AM in response to John Lockwood

I just checked it out, and 'Wake On Wireless' is officially part of the spec for the iPhone 4. Waking the phone up to receive a Facetime call would be a completely logical extension of this feature.

If you and your friend both have Airport Extreme Base Stations, they must be running firmware 7.4.2 or later for Bonjour/Wake On Wireless to function. They must also host the network, and the wireless network the iPhone is connecting to should be the first network in your list of preferred networks.

See this page for more:

http://support.apple.com/kb/HT3774

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Answer 10

Aug 4, 2010 9:47 AM in response to Michael271

This is likely a dumb question, but I usually don't have WiFi on in my settings. I only turn WiFi on when I'm in an area where I know I can access a WiFi spot (ex: Starbucks, Panera, etc.) So, what happens if someone tries to facetime me and I don't have WiFi on?

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Answer 11

Aug 5, 2010 1:42 AM in response to lobsterghost1

That's a good question! If your wifi isn't on, the Facetime call will be rejected.

One idea is to SMS the other person to ask them if they want a Facetime call, so they can connect to wifi first. Otherwise, call them first, then you can switch to Facetime during the call.

It never hurts to just try first and see what happens. Your timing might just be perfect!

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Answer 12

John Lockwood Author

Level 6

13,697 points

Aug 5, 2010 2:19 AM in response to Michael271

Micbarry wrote:
I just checked it out, and 'Wake On Wireless' is officially part of the spec for the iPhone 4. Waking the phone up to receive a Facetime call would be a completely logical extension of this feature.

If you and your friend both have Airport Extreme Base Stations, they must be running firmware 7.4.2 or later for Bonjour/Wake On Wireless to function. They must also host the network, and the wireless network the iPhone is connecting to should be the first network in your list of preferred networks.

See this page for more:

http://support.apple.com/kb/HT3774

My base stations are 802.11n simultaneous dual band models running 7.4.2, I don't know the exact version the other person was running but they were doing the calling so the wake on demand issue would not be applicable to them.

I cannot see any method in the iPhone settings to prioritise the order of WiFi networks, but as it does reconnect to my network automatically when manually woken rather than trying someone else's network I presume it is correct.

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Answer 13

Aug 7, 2010 9:47 AM in response to John Lockwood

One thing to try is to check your Base Station client log to see if your phone is being 'pinged' from time to time when it's asleep. Your Base Station should be sending periodic checks to see if the phone is still responding.

To check this, sleep the phone, then open Airport Utility. Select your Base Station on the left, then click 'manual setup'. On the top bar select 'Advanced'. There will be three tabs: Logs, Wireless Clients and DHCP Clients. Select Logs.

You'll need to know the WiFi MAC address of your phone, which can be found out on your phone via Settings, General, About.

Once your phone has been sleeping for 10-15 minutes (it can take longer to occur, but if you don't see it within an hour then something is wrong), look for long entries that say, 'Associated with station Xx:xx:xx:xx:xx:xx' where that character string represents your wifi address. About 20 seconds later in the log, it will say, 'Disassociated with station Xx:xx:xx:xx:xx:xx'.

If you are seeing this periodically in your log even though your phone definitely wasn't receiving anything or in operation in any way (apart from being in standby) then your network is aware that your phone is ready to be woken up if need be.

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