Driver [upd]: Atheros 9285

echo "options ath9k ps_enable=0" | sudo tee /etc/modprobe.d/ath9k-ps.conf Disables hardware power saving, which stops random disconnects.

If you need a direct link to the most practical article (step-by-step with commands), search for – the community wiki on UbuntuForums is still actively maintained for this chip. atheros 9285 driver