Search code examples
androidgpslocationwifibattery

Android: Battery impact of using wifi to get location; without being actually connected

I have heavy location requirements for my app. I want to use wifi to get location data. If I make users turn wifi on throughout day(mostly it will not be connected), how much of battery impact it will have compared to using GPS with high accuracy?

Solution

  • GPS will kill your battery life whether used with high accuracy or not. When you use your phone for turn by turn direction, notice how it turns into a little heater.

    Wifi is better. Notice how continuous usage of wifi generates a lot less heat than does the GPS. And heat directly corresponds to energy usage due to a nasty thing called physics.

    WiFi impacts power in the following way. They are in order of high power to low.

    1. transmitting data (worst)
    2. keeping the processor awake (competes for worst)
    3. receiving data (pretty bad)
    4. monitoring for networks (depends)
      • asking to join (transmits so not good)
      • without asking to join (pretty good since only receiving)
    5. Off (for completeness and has excellent power usage)

    I suspect that phones don't need to use joining to improve accuracy. This should be easy to test by leaving the wifi on but set to disabling "join" requests. If your phone says, "Please turn on wifi joining to improve accuracy," then you know you need to transmit.

    You didn't ask this, but the best advice I can give to minimize power usage is to figure out the minimum sampling rate you can use but still obtain the accuracy you need. See this explanation, specifically the "checking events" explanation at the bottom.