If you notice that your Raspberry Pi disconnects from the Wi-Fi network and then fails to reconnect automatically, check the power-saving setting by running the following command from the terminal:
iwconfig
if the output includes Power Management:on
disable this setting with the following command:
sudo iw dev wlan0 set power_save off
Now check that the command has taken effect by running iwconfig again.
If nothing has changed, edit the interfaces file, again from the terminal, with the following command:
sudo nano /etc/network/interfaces
and add the line:
wireless-power off
save the file, restart the Raspberry Pi and then check again with the iwconfig command.
Enjoy!
