If you're having trouble with Wifi power management in Ubuntu, Or just want to simply keep your Wireless modem card running 100% all the time, then this post is for you.
This topic has been covered already by another excellent blogger, and I want to give them credit here: https://itechscotland.wordpress.com/2011/09/25/how-to-permanently-turn-off-wi-fi-power-management-in-ubuntu/
I just wanted to bring this subject to light again, and add to it, increasing wireless transmission power (txpower)
Run this command to turn off power management:
sudo su -c 'mkdir -p /etc/pm/power.d/; echo -e "#!/bin/bash\n\niwconfig wlan0 power off" >> /etc/pm/power.d/wireless'
To increase your Wifi power to max output, run this also:
sudo su -c 'for((i=1;i<699;i++)); do iwconfig wlan0 txpower $i > /dev/null 2>&1; done; i=$(iwlist wlan0 txpower | grep -oP "=\d+" | cut -c2-); echo "iwconfig wlan0 txpower $i" >> /etc/pm/power.d/wireless'
You will be able to see the changes in the file: /etc/pm/power.d/wireless
You can check your current settings with the iwlist command:
iwlist wlan0 power
iwlist wlan0 txpower