Windows Phone is very careful with how much power it uses. Normal behaviour for the OS is that whilst running on battery it will drop the Wi-Fi connection after a short period in order to conserve as much juice as possible. We have seen reports that point the finger at some apps which are seemingly overriding normal power saving behaviour. Is this a feature or a bug, I decided to do some tests.
The initial report I saw highlighted iHeartRadio as a culprit, but I had already noticed Skype holding onto its Wi-Fi connection when I was making a few calls the other day. To clarify, I was on a call in Skype, ended the call, locked the device, opened again and Wi-Fi was still showing as connected.
I decided to first test the behaviour of Wi-Fi with the streaming app, LastFM. Running on battery, I started streaming some music, locked the screen and left it playing. LastFM continued to stream music over Wi-Fi, keeping the connection active. I then went into LastFM to stop streaming, locked the screen, unlocked the screen and can see that it’s dropped the Wi-Fi connection. I think this behaviour is fairly normal, although have to admit to not knowing it kept Wi-Fi alive when streaming as I normally leave my phone powered whilst doing so.
Skype on the other hand seems rather different. I started Skype, made a call, ended the call, pressed the Start button, locked the screen and left it. Upon opening the device again I can see Wi-Fi is still active, the phone has not dropped the Wi-Fi connection. Skype doesn’t show itself as running as a background task or anything out of the ordinary.
The only way to get the phone to drop Wi-Fi is to toggle the radio on and off. We know that some Windows Phone apps have special privileges to hit the OS directly. I can certainly understand the need for apps to hold onto Wi-Fi but is this breaking the general power saving rules of the OS to do so? In the case of LastFM for instance, it’s not actually that much of a big deal as Wi-Fi is pretty efficient compared to 3g and when streaming stops, the connection to Wi-Fi is broken. But there is something happening with the Skype app where is maintaining the connection or at least not signaling to the OS that it can resume normal operation of dropping Wi-Fi once a call has ended, the screen is locked or the app is suspended.
Those are the apps I have tested and the behaviours I have seen. I’d be really interested if you have seen other apps that show this type of behaviour & do you think it’s a feature or a bug?
Source Mobility Digest; Thanks, tire_007, for the tip!
Reader comments
Skype and other apps causing Wi-Fi on Windows Phone to stay connected?
Hi Robert,
I'm quite confused by all this, especially since you seem to suggest that Last.fm for you keeps the WiFi on. That doesn't happen for me (WP8 Lumia 820); if i want to listen to Last.fm at home, on my phone, my only option is to turn off WiFi to force use of 3G or tap the screen every time it's about to turn off. Otherwise it just drops the WiFi once it's locked and shortly the music stops playing. If i unlock the screen it will wait a few seconds, reconnect to WiFi and continue playing.
This Skype thing therefore is pretty annoying for me because i'm definitely not gonna download Skype and leave it on all the time just to allow me to listen to Last.fm uninterrupted but that seems the only way. How can i make Last.fm just work properly? Any ideas? Sounds like yours just worked from the get-go so i don't get why mine is like this =(
Finally! A way to stay connected to WiFi under lock screen. Something I've been irritated about since I got my Windows Phone.
Time to download Skype.
There is a yahoo messenger by ashterisk which hold the Wi-Fi always on even after locking the screen. mostly I use this to keep my Wi-Fi alive and I haven't check for the other programs
Hey guys, this is ALL I NEED!
Even if it costs me less battery time.
I really want my Lumia 800 to keep the damn wifi ALWAYS ON. when I'm at work, those wifi droppings force me to log in at the company's network every 5 minutes (this, combined with the fact that IE doesn't remember passwords, really pisses me off).
It would be great, in fact, if there was a native OPTION to leave wifi on persistently or the usual drop way.
There should be an app for that, really. Developers? :P
Anyway, thanks for the heads up. I'm opening skype here right now! :D
(hope this "bug" never get corrected. or, ideally, get turned into a system option)
Have no problems using Skype on my wp 7.5
If this is a "bug" then they should turn it into a feature! I can't believe MS still hasn't added a toggle in the WIFI settings menu to keep WIFI on all the time.
Lack of persistent WIFI makes WP7 nearly useless for people with spotty 3G or PAYGO data plans.
Ate we basing this on an icon? Are we looking at our router to see what devices are connected? Are we looking at data usage to see of it's cell ot not?
Either way I think the constant cycling is breaking my L900. It is getting crap reception on WiFi.
I think WiFi needs to have two options...one that's recognized as private, safe and auto connects and a second open public connection that must be manually connected each time. The same way your PC connects to its networks...they should also add settings in these apps to add user preference regarding this issue.
Spotify does this on my Titan, every time, without fail. I use it to toggle WiFi on and leave it on so that I don't have to wait for it to reconnect every time I turn my phone back on.
Yeah, I'm the one who posted that initial report to keep the wifi connection alive using iheartradio and it goes like this. Open iheartradio, hit play on any station, then stop and exit the app (you can press the Back button). Go to the Music Hub just to make sure that the station shows as paused. Now enjoy always connected WiFi... Just note that if you listen to anything else after having stopped iheartradio you break the spell.
Using Skype as you described in my original Focus seems to work.
Yeah, I'm the one who posted that initial report to keep the wifi connection alive using iheartradio and it goes like this. Open iheartradio, hit play on any station, then stop and exit the app (you can press the Back button). Go to the Music Hub just to make sure that the station shows as paused. Now enjoy always connected WiFi... Just note that if you listen to anything else after having stopped iheartradio you break the spell.
God! Just a few days ago I posted about this "bug" on XDA. I had no idea what caused it though. http://forum.xda-developers.com/showthread.php?t=1759008
Not having this issue on my L900 with Skype and tango installed among other apps
I don't get why everyone thinks WiFi wastes juice. If your constantly locking/unlocking, keeping the connection will use less power than constantly connecting and disconnecting.
Sounds like a case for Mythbusters... turning your lights off is always better even though it does take power to turn them back on...using a second radio just logically makes sense it would use more juice, but that would depend on what type of cell signal you were working with.
Apparently you should only turn your light off if you're not going to turn it back on after.an hour i.e. Turning a light on and running for 1 hour is more efficient than turning it on twice.
Correct, if it is a modern low energy or a tube bulb which has a "starter" to come on. In a traditional lamp with only a wire that glows white hot you should switch off when not in use regardless.
I think you guys are grossly mis-informed. The amount of power to start up a tube bulb or CFL is equal to about 3-5 seconds of run time. Not even CLOSE to 1 hour. Turning a bulb on and off does put a strain on the life of the bulb, and most review cases I could find state that you should use a ~5 minute Rule of Thumb...if you leave for less, leave them on, gone for more, turn them off. Now...having said that, if you are on the East Side of the Atlantic, I don't know if your volt differences completely changes everything...
I'm a bit confused. You are saying that the streaming app keeping the WiFi alive under lock screen while on battery (and streaming) is not the correct behavior?
No, I dont find that wifi is kept alive whilst streaming underlock that much of an issue. the issue is that once skype is launched wifi just stays on no matter what your doing. Until you manually switch it off.
Ah ok. I just wanted to make sure I understood correctly. :)
I like it either way, if WiFi is on its on. So if it's a bug, its a god bug, even if a god bug is a dead bug, but as said, this bug don't bugger me at all :-D
The wifi only seems to stay on after I have ran skype, other streaming apps (once stopped) seem to resume the normal behaviour of dropping wifi. LastFm dropped it after I stopped streaming.
What if you run Skype, THEN run Last.fm...does the phone go through a process when using a second streaming app that breaks it out of the "WiFi Persistance Loop" caused by Skype?
Do not have WiFi here to test myself, but I would LOVE if the Xbox Compainion app had WiFi persistance. Every time I turn the screen off it has to reconnect to WiFi again so I can control my Xbox.
Its a bug, not present on my titan since I've been using it pretty much every night since beta. The only way it stays connected is during a call (even under lock screen).
Device specific then maybe, thats interesting. I'm using a Lumia 800 running
OS 7.10.8107.79
Firmware 1600.2487.8107.12070
RB
I've seen this happening to me the last couple of days. I have Skype installed but I rarely use it on my phone. I don't think it's Skype. My latest app installation is at least one 3-4 week old, so an updated app can be the one blame here. Perhaps one of them triggered this behavior/feature/bug somehow.
I'm not sure if I want some app to keep WiFie on while the device is locked and on battery, but I've seen the battery last a little longer when this began and I noticed it. Specially with the phone staying locked for extended periods of time.
I personally would love to be able to keep my WiFi constantly connected even when the device is locked... 3G coverage where I am is spotty so a constant WiFi connection would be beneficial
So what if I told you this little glitch that keeps WiFi running (persistent WiFi) is actually saving your battery. Stay tuned.
WiFi is certainly much easier going on the overall power footprint. I'd love to know if you have some numbers on it.
How can keeping it on for hours be better than keeping it off for the same time? Or is it like a house light that uses most of it's power upon being switched on, and very little while running by comparison i.e. So it's more efficient to leave a light on for an hour instead of switching it on/off 5 times?
Because while WiFi is off the the phone is defaulting to using the cellular radios for data connection, which often tends to be a more power hungry radio. Plus this let's background data to be loaded from WiFi which saves your data plan if you're on a limited one (fyi, both other major OS's do this).
I haven't changed my startscreen or installed new apps, however I did sideload my own app using the developer tools. This was WAY before I noticed my Wi-Fi staying on all the time. So basically Wi-Fi is turned on all the time with no outside influence. It must be OS related. Still at Mango though, no Tango dancing for me...
Well interesting thought, just throwing this out there, what if this was by design? Doesn't skype on desktop work based on a node or p2p technology? So by keeping the wi-fi on your phone on, doesn't that make your phone a node?
It could very well be a bug but am sure skype developers would have thought of this. I mean wi-fi doesn't cost anyone anything really... so why not use free wi-fi to create a p2p node for mobile devices which otherwise are not always connected to the internet (besides 3g/4g)?
Super nodes dont exist anymore (on the client), MS are now running servers to replace that system. But good thinking.
True, but Skype requires a constent connection, hence why Skype can't use the existing Notification system Windows Phone.
It's a bug, there is no reason for an app that is no longer reading data over the network to keep the WiFi on. It might have some beneficial consequences, but that doesn't make it any less of a bug.
I think developing the option to stay connected to Wi-Fi would be a great concept, especially for people who have limited data plans. It wouldn't be breaking the power consumption rule, because as long as the ability to toggle is there, they can stay true to their word that the phone has a great battery life...giving us the choice to selectively reduce the consumption at our own risk. In fact, it wouldn't surprise me if the concept was already on the table, but shot down by carriers due to loss of revenue.
I'm sure carriers wouldnt mind phones being used only to make VoIP calls? ;)
I think its a feature, and a good one because I need to receive notifications and IMs over WiFi which I normally can't while under lock screen. Another app that does this is Nokia PlayTo.
I second the Nokia PlayTo claim. I installed it and noticed my battery life had almost halved. Uninstalled it again (never use it) and battery life is back to where it should be.
Thats interesting, you think it impacted your battery even without it being active, was it keeping wifi enabled the whole time regardless?
I'm not quite sure what it was doing. However, I did uninstall Viber at the same time, which could equally have been the cause.
I didn't notice the WiFi on at any time - it wasn't connected, if it was on. But something was definitely using power - the phone would go down to 40% overnight doing nothing.