Samsung Galaxy S3 SC-06D docomo Instruction Manual page 246

Setting sleep policy of Wi-Fi
You can set to disable Wi-Fi when the display
of the terminal turns off or to enable when
charging.
1
From the Home screen,
"Settings" → "Wi-Fi"
2
"Advanced"
3
"Keep Wi-Fi on during sleep" → Select
a sleep policy
Selecting frequency band for Wi-Fi
Select frequency band to use.
1
from the Home screen,
"Settings" → "Wi-Fi"
2
"Advanced"
3
"Wi-Fi frequency band" → Select
frequency band to use
244
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→
Settings