[Ubuntu] Wireless not working when on battery

If you have read my previous post How to release/renew IP when dhclient doesn't work, but you still unable to use your wireless when running your laptop on battery mode, then it could have something to do with the power management in Ubuntu.

The symptom you might get is:

1. the wireless IP cannot be renew/release
2. the wireless connection is up, but you can ping local or internet
3. the wireless takes forever to get an IP from your router

The reason behind is when you're on battery, Ubuntu will activate power saving on your wireless device. This made the device cannot function properly. In this case my wireless device is:

"Broadcom Corporation" "BCM4312 802.11b/g LP-PHY" -r01 "Foxconn International, Inc." "T77H030.00 Wireless Mini PCIe Card"

If you are asking for help, you can identify your network controller by enter this command in terminal (special thanks to Serendah Linux from Ubuntu Malaysia LoCo Team to provide this command):

lspci -mm | grep Network | sed 's/.*"Network controller" //'

There are some solution that propose to deal with the 'wireless' file in the following location

• /etc/pm/power.d
• /usr/lib/pm-utils/power.d

but those doesn't work for me, and it might happen to you as well. If that is the case, you can still solve it by manual enter the following command into terminal:

• iwconfig eth1 power off

Please note that the "eth1" has to be your wireless interface. Some might name after "wlan1". You have to enter the command every time you reboot a new session. I have not found any working method to execute this command during start up, if you do found it, please share with me.