Why keep WiFi on while asleep?


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  1. ZDroid1

    ZDroid1 Well-Known Member This Topic's Starter

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    It's become a standard recommendation on battery-related threads: Set WiFi to stay on when the phone goes into sleep mode.

    My understanding is that 3G is only active when data is being transferred. But when WiFi is on and connected, it is ALWAYS on and connected.

    Let's say I sleep for 8 hours at night, and I have apps that update every 30 minutes. Do I want WiFi to be connected for the entire 8 hours, or just let the phone use 3G for a total of 16 times (8 hours / 30 minutes)?
     

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  2. c2k

    c2k Well-Known Member

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    Well, the wifi naturally turns off when the screen turns off, so if youre transferring data, it will switch to 3g= more battery consumption. so at night while its charging, it probably doesnt matter. When Im near wifi though, it definitely helps with battery life to have it set to not turn off. Regardless, wifi is much faster than 3g for me
     
  3. Infinite-t

    Infinite-t Well-Known Member

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    So the question is, do you let your phone use wifi 16 times a night, or use your 3g data while connected to a perfectly good wifi. If you have limited data plan, I would rather have my phone use wifi for as much as its data usage as I can. I have been doing that all along. With my wifi on all day, at the end of the day, my battery usage by wifi is a mere 2%. I think I can live with that. In fact I have mine set to turn 3g off any time I am connected to wifi I consistantly get about 20 hours of moderate use out of my battery with wifi and blue tooth on all.day. plus, if you are charging your phone at night while you sleep, battery use wont be an issue anyway.
     
  4. ZDroid1

    ZDroid1 Well-Known Member This Topic's Starter

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    I don't plug it in at night, and I'm not worried about data consumption. This is strictly about the battery.
     
  5. snapper.fishes

    snapper.fishes Well-Known Member

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    Urgh. Difficult question. I think wifi sucks up more battery, but that's just my guess.
     
  6. Infinite-t

    Infinite-t Well-Known Member

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    Yea, I don't know which uses more juice, the 3g radio, or wifi radio... either way, you are sending and receiving data that must be processed by your phone's proc. I do know that the proc. Will use the same amount of juice to process the same amount of data no matter how it was received. Perhaps I need to do some experimenting and try it each way for a day and see what happens. The only problem I see with trying that is it would be difficult to exactly match my usage 2 days in a row.

    My personal opinion is the power use difference between the two, at least for small bits like widget updates is very minimal. But I could be wrong.
     
  7. mwxiao

    mwxiao Member

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    This is a very good question. I personally feel wifi consumes more power than 3g despite everyone else claims the opposite.

    I think if you keep wifi on all the time, what consumes your power is the always connected wifi.

    But if you have wifi on only when screen is on, the phone has to switch wifi on every time the screen is on. And that consumes power too.

    But I have no idea which one consumes more power.
     
  8. Infinite-t

    Infinite-t Well-Known Member

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    Yea, the only thing I can go by, is with my current setting, wifi always on and shutting off 3g when connected to wifi, at the end of a 20hour day, my wifi radio has used 2% of my battery.. i can live with that. I am also on a limited data plan, so i prefer to use wifi over 3g any chance i can.
     
  9. harryzwd

    harryzwd Well-Known Member

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  10. ZDroid1

    ZDroid1 Well-Known Member This Topic's Starter

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    Thanks for the link. That pretty much agrees with my suspicions. I figured there was a good reason Samsung set the WiFi default to off while the phone is in sleep mode. I'm going to go back to the default setting.

    During a stretch of 6 to 8 hours at night, it doesn't make sense to keep it connected to WiFi the entire time just for the occasional updates and syncs.

    Now if they could make it so WiFi connects only when needed (while in sleep mode), I might go for that instead of 3G. Maybe I should write an app that does that and it would be the ultimate battery saver!
     
  11. sremick

    sremick Well-Known Member

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    It might not make sense from a battery standpoint (in certain circumstances), but it makes sense from a data quota standpoint.
     
  12. ZDroid1

    ZDroid1 Well-Known Member This Topic's Starter

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    But does it really? I mean my biggest data consumption happens when I'm surfing the web, streaming YouTube videos and downloading apps. Obviously, I do none of that while the screen is sleeping.

    News feed updates (which happen once an hour) and GMail syncs can't be that bad. That's what, half a megabyte a night, times 30 days = 15 MB ?
     
  13. sremick

    sremick Well-Known Member

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    Depends on the user/apps. There are other threads about people discovering 100MB/day 3G usage issues that were ultimately traced to this setting. In fact, it might be the way it was originally researched or stumbled upon.
     
  14. Infinite-t

    Infinite-t Well-Known Member

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    Hmm, interesting post there, and interesting theory. I can kinda see what he is saying.

    But he says that while on wifi you are constantly transmitting.. transmitting what? If no data is being transmitted, you have a device on either side with an antenna tuned to eachothers frequencys... they are "on" and using some power to be "on" as anything would but nothing is constantly being xmitted (at least I dont think so). Think of a two way radio (walkie talkie). They are tuned to eachother, and always "on" but they arent constantly sending signals to eachother when you arent using them. The only thing I can see with wifi is that the router does interogate (ping) the device. Basically asking your phone, "hey, are you still there?" and the phone says, "yea". But if I understand propperly, 3g does the same thing, but i dont know how frequently they do this, but the data used to do it is super small (just a few bytes).

    On the other side of the coin, we all know wifi is MUCH quicker than 3g. So lets say your phone is transmitting 1 meg of data. Over wifi it takes 5 seconds to transmit, but over 3g it takes say, 30 seconds. So your phones 3g radio was transmitting for 25 seconds more than the wifi radio, so I would assume that would use much more power to send the same amount of data over 3g than wifi.

    I dont have any raw data to back this up, its all just speculation on my part and I am certainly no expert on this, so this is just an alternate theory FWIW. It would be interesting to so some real scientificly tested information on this question, at least for me.. im a geek and proud of it ;)
     
  15. ZDroid1

    ZDroid1 Well-Known Member This Topic's Starter

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    Well yeah I'm sure the amount of data transmitted to keep WiFi on is minimal, but when it's on for a full six hours, it adds up. 3G, on the other hand, is on only when it actually needs to transmit something, at least according to my understanding.

    I'm actually concerned about the battery consumption, not data.
     
  16. mwxiao

    mwxiao Member

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    Wifi is faster because it requires more power per second.
     
  17. Infinite-t

    Infinite-t Well-Known Member

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    I actually was refering to power in that, the amount of power used to transmit the same amout of data over wifi vs. 3g.

    But again, this is just how I see it and I am no expert on how 3g works vs how wifi works, or how any of this translates into actuall power consumption.
     
  18. Infinite-t

    Infinite-t Well-Known Member

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    I thought wifi was quicker because its carrier frequency (wifi usually at 2.4Ghz) is higher than that of the 3g (1900 MHz and 850 MHz ) and has to travel less distance than 3g. Wifi to your router 50 away vs 3g to your tower a few miles away?
     
  19. Terry S

    Terry S Well-Known Member

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    We have 4 Captivates in our house. On the first night my daughter used 94 MB of data at 2 AM. She was at home asleep. This was very strange we have turned the wifi sleep mode to never and it has not happened again.
     
  20. Mathieas

    Mathieas Active Member

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    I leave Wifi on at all times when at home. Over night not plugged in i lose 4% from standby for 8-10hours. I have not tested 3g only on this phone but my last captivate(it took 4 to get a good one) lost much more over night with 3g only.

    Mathieas
     
  21. Mathieas

    Mathieas Active Member

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    That is my understanding as well, it is not simply more data means more power... its a factor of frequency and radio output signal level. Wifi uses far weaker signals then 3g thus requireing much less power per meg.
     
  22. noc

    noc Well-Known Member

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    I'll have to agree that it depends on user/apps. It also depends on location and signal you receive... personally, I don't have a lot of syncing going on. Just two email accounts. If I leave my phone on overnight (about 8 hours), I use less battery with wifi turned off. By the time I wake up, I've received about a handful of emails and only used about .1 MB of data. Doesn't bother me.

    However during the day when I'm using more data, I REALLY prefer wifi. On days that I've been out in areas with no wifi, I noticed that my phone overheats working on 3G for too long. I won't say I'm 100% sure of that 3G was the cause (it could be a combination of being in an area with low reception), but I do know that overheating = bad for battery. I leave wifi on during the day as much as possible when I'm at home or on college campus.
     
  23. ZDroid1

    ZDroid1 Well-Known Member This Topic's Starter

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    Ok I tried it both ways, and my battery loses about 6% either way (i.e. WiFi on our off) in about 7 hours when the phone is in sleep mode at night. It makes no difference
    .
     

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