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Support Why is WIFI throttled with the screen off?

Discussion in 'Android Devices' started by Travisimo, Jan 3, 2012.

  1. Travisimo

    Travisimo Android Enthusiast
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    I'm not referring to wifi disconnecting when the phone sleeps - that's entirely different. I mean, my wifi speed drops to near dial up speed immediately when I turn the screen off. When I turn the screen back on, it kicks back up to broadband.

    For example, I installed modern combat 3 because it was on sale for 99 cents. It's nearly a gigabyte in size and I obviously wanted to do it via wifi. When the download started, it was cruising by at appx 1 Megabyte/sec (~8 Mbps), but immediately when I turned the screen off, it slows down to something like 5% of that speed (I didn't do any exact measurements).

    Does anyone know if this is by design or a bug? Is it something unique to the Gnex or ICS? Do we have an exact figure on what it's throttled down to? My wifi setting on the phone is set not to sleep, so please don't suggest that... Plus, as I said, it's not disconnecting but merely severely throttling.
     

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  2. DavidLinSuperstar

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    I am getting the same issue when I use Winamp to sync my music. If I leave the screen on, it transfers the songs fine, but if I lock the screen, it slows to a crawl.

    My "Keep WiFi on during sleep" option is set to "Always".
     
  3. PhilosoRaptor

    PhilosoRaptor Android Enthusiast
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    I'm going to guess it's the CPU bottlenecking connection when the phone is idle due to the the clock speed being governed when the display is off. I think it automatically downclocks to around 350 MHz at idle. Same deal for the issue when people play high bit-rate music when the display is off and it starts skipping/popping while playing the music.

    Just a guess though. A good test would be for a rooted user to set the governor to "performance" so the CPU stays at higher clocks and see if the same thing happens.
     
  4. CharlzO

    CharlzO Android Expert
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    Couldn't tell you for certain as for percentages, but I just downloaded a 200 MB file, nothing else running on the phone as far as data. With the screen on, I was pulling about 20 MB in a 90 second stretch. With the screen OFF, it dropped to 9 MB. I repeated it three times, with a short break between tests, and got pretty much the same results across it. It's not enough of a drop to interrupt anything streaming (Pandora) on my phone, so I had never really even noticed it. But figured I'd just add my quickie test for those interested.
     
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  5. stevevt

    stevevt Member
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    Confirmed that this behavior is happening for me as well. When I needed to grab a very large file, my solution was to select the option not to turn the screen off when charging (in Development options), start the download, and plug the phone into a charger.
     
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  6. jkc120

    jkc120 Android Expert
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    Hmm, weird my reply didn't go through earlier.

    Anyway, just wanted to say that this has been the behavior I have observed on my dinc with the stock ROM, a custom sense ROM as well as Cyanogenmod 7. I believe T4rd is correct that it's likely a CPU throttling thing. When the screen is off, the CPU probably goes into a low power state and/or a lower frequency to conserve battery.

    You can test this by downloading the SetCPU app (root required) and set both the min and max CPU frequency to 1.2 GHz. Then see if the wifi speeds are still throttled when the screen is off. If not, the CPU is likely the culprit and you'll have to use a workaround or SetCPU profile to keep the CPU up at 1.2GHz or something similar. If it's still a problem even when the CPU is kept at 1.2 GHz, then it's possible the wifi chipset is still entering a low(er) power state, despite that setting. That could indicate a bug or simply a feature to conserve power.
     
  7. CharlzO

    CharlzO Android Expert
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    To be honest, I don't mind that it throttles with the screen off to conserve battery, it's what a lot of people do anyway. However, I would like to at least know ahead of time, and get the option to disable that feature on my own. As long as it doesn't interrupt streaming, I won't care TOO much, but it'd be nice to have the option.
     
  8. quickaudi

    quickaudi Android Expert
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    Same thing happened to mine.
     
  9. 318vert

    318vert Newbie
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    Im having the exactly same issue, im trying to download modern combat but i get to like 500 mb and screen goes off. But im not throttled i lose my wifi completely. It says i have internet connection but i cannot even open web pages.

    When i start the download again i says i only downloaded like 200mb... stupid.
     
  10. Travisimo

    Travisimo Android Enthusiast
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    Try Stevevt's suggestion of plugging the phone in and setting the screen to stay on. That should at least get you through the download of Modern Combat. As for your WIFI completely disconnecting, are you certain you've checked the settings for keeping WIFI on when the phone is asleep?
     
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