The driver is already installed by default but it does not work great, but there is a tweak we can do to help.

echo "options ath9k nohwcrypt=1" | sudo tee  /etc/modprobe.d/ath9k.conf
sudo modprobe -rfv ath9k
sudo modprobe -v ath9k

I tried the following solution and it worked fine for me: sudo -i echo "options ath9k nohwcrypt=1 ps_enable=1" >> /etc/modprobe.d/ath9k.conf modprobe -r ath9k modprobe ath9k nohwcrypt=1 modprobe ath9k ps_enable=1

Then, reboot your system to take affect.
To get more option, see here