Wednesday, February 26, 2014

WiFi Characteristics of mobile phones in screen lock mode

I have a Nexus 5 and I was wondering what power strategies/algorithms are used in it to save power when the screen is locked and the display is off. I wanted to have a practical first hand experience of seeing this happening.

So I pinged the phone from my computer while it was connected to my WiFi network. I did performed the process twice - once while the phone was active and I was switching between/using apps on it, and the second time when the screen was locked and the display was off.
I sent out 100 ping packets and here are the results:
Ping during locked screen with display off

Ping when the phone was active
Summary:

  • When screen was locked and display was off
    • Minimum = 8ms, Maximum = 866ms, Average = 295ms
    • Sporadic replies to ping, although no no packet was lost. Maybe the WiFi receiver was always on but the transmitter was only turned on periodically.
    • A very large variance in the round trip times.

  • When the phone was active
    • Minimum = 3ms, Maximum = 387ms, Average = 63ms
    • Quick replies. WiFi chipset must always be active.
    • Lesser variance in round trip times

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