# WiFi and 4g at the same time?



## dpaine88 (Jul 21, 2011)

So I try to turn 4G on only when I need it really.

I usually am on WiFi. If I am on WiFi and have 4G enabeled, will it still suck power? OR can I just leave 4g on as long as I am on WiFi since it wont be turning the 4g radio on at all.


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## CC16177 (Dec 29, 2011)

I've been curious about this also.

Sent from my Galaxy Nexus using Tapatalk 2


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## times_infinity (Aug 6, 2011)

Nope. When you connect to wifi it disconnects the phone from the data network unless an event where it needs to pull something over the network using data like MMS or other things.

Sent from my Galaxy Nexus using RootzWiki


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## dpaine88 (Jul 21, 2011)

times_infinity said:


> Nope. When you connect to wifi it disconnects the phone from the data network unless an event where it needs to pull something over the network using data like MMS or other things.
> 
> Sent from my Galaxy Nexus using RootzWiki


Thank you.

Someone said the exact oppsite on XDA and it didnt sound right at all.


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## Joesyr (Feb 7, 2012)

That was me! I am going off of my experience in flashing a new rom and trying to figure out why the battery was so terrible, only to find out I forgot to turn off 4g again. I only really flash roms when I have a sit-around-the-house and work kind of day, but it's possible I am misremembering my experience.

Also, my reasoning behind it is this: Part of what drains your battery is your phone actually powering the antenna to maintain the signal. Check your phone status in settings when you are connected to wifi and you will see that you still have an LTE signal, same as always. It is true that when wifi is on all of your data is processed through it. But the radio in your phone does not actually turn off, and this will drain the battery.

If anyone disagrees that it works this way I am happy to hear that I'm wrong, but I am not a heavy data user by a long shot, I'm usually on wifi, and I -always- notice that my battery has been terrible if 4g is on.

Edit: To clarify, your phone won't be drained _additionally_ by doing data transfers over LTE, because the data does go through wifi. But the idle drain is a killer as well, and you will notice this. 4g idle drain>3g idle drain.


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## legacystar (Jun 9, 2011)

Radios have a sleep state. So while the radio may not be switched off, its asleep using no power.


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## Joesyr (Feb 7, 2012)

legacystar said:


> Radios have a sleep state. So while the radio may not be switched off, its asleep using no power.


Well it might be less but it's not none. "Cell standby" in battery under settings is usually around 10% of my total battery drain, on 3g, even if the phone's just been sleeping all night with wifi on.

Edit: With regard to the original question, maybe it's just that I'm not in a particularly strong 4g area? I get a good signal bars-wise, but looking at it right now, I get a 3g signal of -83dBm and -100dBm on 4g. I agree that it seems like wifi -should- work the way your describe, but my experience tells me otherwise. I'm interested now though; I wrote off 4g a while ago and just don't use it, but I'll put it on tonight and see how my overnight drain stacks up to usual.


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## legacystar (Jun 9, 2011)

Joesyr said:


> Well it might be less but it's not none. "Cell standby" in battery under settings is usually around 10% of my total battery drain, on 3g, even if the phone's just been sleeping all night with wifi on.


3g radio is the same radio used for making calls and texts, so unless your in airplane mode, that radio is always on.
The lte radio on the other hand is like a USB modem, and when its not used its turned off.


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## Joesyr (Feb 7, 2012)

legacystar said:


> 3g radio is the same radio used for making calls and texts, so unless your in airplane mode, that radio is always on.
> The lte radio on the other hand is like a USB modem, and when its not used its turned off.


See that's how I thought it would work, but then why is it that under settings->status->about phone, it still says LTE under mobile network type when wifi is on (with a different dBm rating than I get with 3g+wifi)? I don't see how it could have a constant bead on my 4g signal strength unless it's powering the radio, even if in a low-power state.


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## yarly (Jun 22, 2011)

Joesyr said:


> See that's how I thought it would work, but then why is it that under settings->status->about phone, it still says LTE under mobile network type when wifi is on (with a different dBm rating than I get with 3g+wifi)? I don't see how it could have a constant bead on my 4g signal strength unless it's powering the radio, even if in a low-power state.


Well you're always connected to a tower regardless unless you switch to airplane mode. Same tower gives you voice (which is really also a form of data) and data, so obviously it can also report if your current data connection would be LTE. Does not mean it's actually using the data connection though. When you switch off wifi, it still takes a few seconds for it to start working again on LTE.


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## Barf (Sep 26, 2011)

I get considerably better battery life when on wifi at home all day, compared to out and about on 4g, so does everyone else I've talked to. This is proof enough for me that wifi puts your radio to sleep. Your mobile network still says lte because it is still enabled, just not currently on.


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## legacystar (Jun 9, 2011)

Joesyr said:


> See that's how I thought it would work, but then why is it that under settings->status->about phone, it still says LTE under mobile network type when wifi is on (with a different dBm rating than I get with 3g+wifi)? I don't see how it could have a constant bead on my 4g signal strength unless it's powering the radio, even if in a low-power state.


I don't pretend to have all the answers but the low power states we are talking about are very very tiny amounts of power. We aren't talking about charging up vacuum tubes. I wouldn't stress yourself ou about it.
If your really worried about it turn mobile data off every time u use wifi but I would wager your not going to see any power savings.


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## Joesyr (Feb 7, 2012)

Well I still intend to run an overnight test for my own knowledge, but as a quick test I just charged up my phone and left it sitting there with 4g and wifi on. A half hour in, it's down 4%. Usually my idle drain is about 1-2% per hour. No other changes made to my phone at all today. Obviously needs a longer sample period but I'd say that's the start of something pretty conclusive.


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## yarly (Jun 22, 2011)

Joesyr said:


> Obviously needs a longer sample period but I'd say that's the start of something pretty conclusive.


Test all you like, but remember that correlation does not imply causation (one's observations of an outcome may not be the real cause). Way too many variables.


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## Joesyr (Feb 7, 2012)

yarly said:


> Test all you like, but remember that correlation does not imply causation (one's observations of an outcome may not be the real cause). Way too many variables.


Doesn't refute it either! I'm well aware of that paradigm but I'm sitting here controlling just about every conceivable variable. True, it's possible that the day I chose to run my test might well be the day that Verizon chose to do maintenance on my local cell tower, or the day the sun chose to throw extra ions into my local atmosphere, but for practical purposes, when my testing methodology is
1)Leave everything else how it normally is.
2)Press the button to turn on 4g.
Then I feel pretty confident when I present my results. I might have little in the way to explain why exactly this happens, but there's not exactly a lot of variables flying around here (hmm, thinking about it, day vs night might actually be a big one if network strain from everyone running around can impact my phone's radios). Of course I patiently await to see if my initial start will average out to normal drain or continue at this rate. And I encourage anyone to run their own test because ymmv when it comes to one person testing on one phone in one region of cell signal coverage.

I need to leave for a bit and take my phone with me so I have to put this on hiatus, but my first tiny sample came out to 2 hours on, 7% drain, 20% of which was cell standby. Without any saved battery logs or screenshots to reference I have only my fallible memory to consult, but that does seem to be at least double what I'm used to, both for total drain and cell standby as a % of total.

Not going to break my back testing a feature I don't need/use much at all, but I'll try to compile some overnight data side by side over the next two nights. Updates in the future!

Edit: Did a few overnight tests and I retract my previous bias against 4g with wifi on! However I am seeing a strange pattern in kernel wakelocks due to the data radio, but I think I'll just start a new thread on that.


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