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100 Posts


Ohio USA

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  • Posts: 100
  • Registered: ‎10-24-2009
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Save 3G Data Usage and Battery, Less Wifi Waiting

2011-08-15, 20:16 PM

The point of all this is to turn off wifi sleep mode, which is a really hard-to-find setting, and it sounds counterintuitive for saving battery.

After having high 3G data usage for months, I tried changing Social Application sync to Over Wifi Only (in Data Manager), but then I wouldn't get social networking updates. I realized that the issue was that the wifi radio would sleep after a while with the screen off. Automatic wifi sleep was annoying in other ways too: for example, when listening to streaming podcasts with 3G data disabled (with, say, Widgetsoid)-- the playback would stop after 20-40 minutes. If 3G data wasn't disabled, the streaming would eventually take place over 3G, even though a wifi network was still available!

I believe data connections are attempted over 3G when the wifi radio is asleep or is waking up and reconnecting to a network. This sleep mode is different than what can be set using the battery profiles in Battery Manager (Peak, Off-Peak Data Connection). Background 3G data transfers as well as 3G data transfers immediately after waking the screen seem to use a lot of battery as well. Consider the following:

  1. You wake the screen after not using the phone for a while. The wifi radio was automatically in sleep mode.
  2. Because of background or foreground apps, 3G data transfers start taking place before and while the wifi reconnects.
  3. The wifi radio eventually wakes up and reconnects to the wifi network.
  4. The data connection via 3G is interrupted because the "new" wifi network connection is available
  5. The data transfer resumes or restarts (partially or wholly) over wifi

I think turning on the wifi radio and having it scan for networks is power intensive. Additionally, any repeated transfers take more time and the preceding 3G data transfer may be wasted (the connection to the data may be repeated over wifi once the phone reconnects). Also, the preceding partial 3G data transfer uses up battery.

Anyway, I've had better performance, better battery usage, and less 3G data usage by turning off wifi sleep mode: Settings - Wireless & networks - Wifi settings - [Menu button] - Advanced - WiFi Sleep Policy - Never

I also turn check the box for sync over wifi only: Settings - Data manager - Data Delivery - Social Applications - Sync over Wifi Only

These are just my observations only, and you might find differently depending on how you use your phone.

Lenovo Thinkpad T400 Model 6474AH4
Windows 7 Professional 64-bit

99 Posts


United States

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  • Posts: 99
  • Registered: ‎11-14-2010
  • Location: United States
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Re: Save 3G Data Usage and Battery, Less Wifi Waiting

2011-08-20, 11:59 AM

Yay! Thank you irv4 for posting this information. I have have been wanting to find out how to change that setting. The delay in WiFi waking it when the screen turns back on is annoying, and for that period of time it uses 3G data despite a WiFi network being available. For people like me that spend most of the day in an office with WiFi, there is no reason for it to sleep when the screen does.


132 Posts


United States

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  • Posts: 132
  • Registered: ‎01-14-2011
  • Location: United States
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Re: Save 3G Data Usage and Battery, Less Wifi Waiting

2011-08-22, 17:52 PM

Nice post irv4. Thanks for the info.

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