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How does wifi save battery over 3g/4g?General

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  1. jimmypop13

    jimmypop13 Well-Known Member

    I've read several times to keep wifi on when you are at home or anywhere you can get wifi to save battery. I'm confused on how it saves battery though bc even with wifi on, my phone still shows the signal strength for 3g if I've chosen cdma, or the signal strength for 4g if I've chosen lte/cdma. And under network type, it will still show ehrpd or lte depending on the above. Doesn't this mean it is still using those radios PLUS wifi so battery should drain faster in standby? I know mobile network state says "disconnected" but if I'm still getting a signal bar reading and dbm reading for 3g or 4g, doesn't that mean I'm still connected, just not receiving data over them other than phone/txt? So to me, it would seem that best battery with a data connection when the phone is asleep would be 3g. If I turn off all data though just so I can still get phone/txt, it still shows ehrpd so am I really saving any battery over turning on data?

    Am I making any sense? Is there a piece to the puzzle that I'm missing?

  2. jkc120

    jkc120 Well-Known Member

    When you are on wifi, the 3G/4G radios are in a lower power state (iirc) and even so, aren't passing any data so are using much less power than if they were kept awake and transferring data.

    wifi uses less power than 3G and 4G because 802.11 radios are very mature and also are dealing with connections that are feet or tens of feet versus hundreds or thousands of feet with cellular signals.
    jimmypop13 and Andrew725 like this.
  3. Turdbogls

    Turdbogls Well-Known Member

    using a wifi connection doesnt actually turn off the 3g/LTE radios but keeps them at a super low power level. even if it is displaying signal bars for either or, it isn't using the radios.

    not sure of the technicalities, but that is just how it works.
    i can easily go all day on Wifi, but when i am out and about, the 3g/LTE just kills my battery.
  4. Unforgiven

    Unforgiven -.. --- - / -.. .- ... .... Moderator

    I am only on WIFI when I am at home. I am out of the house normally 7:45 - 5:30 a day and leave WIFI on all the time and I can personally attest that it gets better battery life that way. I don't know what kind of VooDoo is going on inside my GNex :confused:. It is counter-intuitive to think that leaving an extra radio on that I know I'm not going to use would increase battery life, but it does.

    Another note, on Sunday I was home all day, never left the house so it was on WIFI all day. I was still at 60% battery 17hrs and I was using the phone more than usual.
  5. LTek1

    LTek1 Well-Known Member

    it's the simple difference between being "on" versus being "actively transmitting."

    Moving data over a high power transmitter consumes more battery than moving data over a lower power transmitter.

    It's just like standby time vs talk time, only with data.
  6. jimmypop13

    jimmypop13 Well-Known Member

    Sweet, thanks guys!
  7. zerocool79346

    zerocool79346 Well-Known Member

    All of this is only true if you are actively using the data connection. I've tested it using battery monitor widget and it consistently uses +20ma with the wifi radio on while in standby versus with just the cell radios active. That said yes, it will use less power if you are browsing or using the data connection.
  8. jimmypop13

    jimmypop13 Well-Known Member

    Hmm, when you say cell radio active, do you have data turned on too? I'm trying to figure out what would be best for overnight battery. I just need calls/txts, but I've noticed even with data turned off, apps are still waking up my phone at night. Maybe I could turn off sync too but I thought that was just for google apps.
  9. jinwons

    jinwons Well-Known Member

    I rarely turn off mobile data in setting. Just toggles Wifi as needed. When the phone connects with WiFi source, 3G/4G icon on signal bar goes away. So I guess it turns off cell radio for data or data radio goes into standby mode with minimal power. Any android phone works this way with WiFi as far as I know.

    I normally use WiFi at home and it drains about 2.5%/hour on standby. 4G radio easily chews up three times more power with Wifi off.
  10. zerocool79346

    zerocool79346 Well-Known Member

    I NEVER turn off mobile data haha. But yes if you will turn off background data and all syncs, there won't be anymore waking up.
  11. syntrix

    syntrix Well-Known Member

    Assumption is that everyone on the cell radios is DRX mode. Is that a fact with our VZWSGN's?

    Or does this rely on tower equipment that supports the mode (not all VZW deployments supposedly support this).
  12. jkc120

    jkc120 Well-Known Member

    How can we tell if we're on a tower with DRX mode?
  13. syntrix

    syntrix Well-Known Member

    I have no idea!!!!
  14. jkc120

    jkc120 Well-Known Member

    I was hoping something would show up in the radio logcat logs, but no drx in there :)
  15. syntrix

    syntrix Well-Known Member

    Doubt it unless the driver is set to log.

    I will say that I have 3 other devices here in the house that are on the same gmail account.

    They all get notifications well before my gnex..... so maybe radio is in that mode... I'm not so sure there's a way to verify it.

    If there's a /proc filesystem, maybe navigate around there ...../usb/lteradioname/anything

    I eat linux for breakfast at work, and I'm not even IT, lol. I haven't dived into android as much as I would have liked to.
  16. jkc120

    jkc120 Well-Known Member

    No luck :(

    Oh well, was worth a quick look. :)
  17. syntrix

    syntrix Well-Known Member

    No, you won't find it that way.

    Look for the cell driver, which I think is under USB from the TI references.

    You'll need to find the folder for the DRIVER/NET ADAPTER, not the name... then peek in there and then cat some files on the running system. It might not be named that.

    Damn, should we be muddying up this thread?

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