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Thread: Ubuntu 12.04 not connecting to home wireless

  1. #11
    Join Date
    Aug 2011
    Beans
    7

    Re: Ubuntu 12.04 not connecting to home wireless

    So, I've given it a couple of days and even after making the swcrypto=1 line permanent, my laptop stopped connecting - it worked for the first and second reboot but not after that. However, what seems to kick-start the wireless connection is the "sudo iwconfig wlan0 power off" line. This seems (touch wood!) to be quite reliable. Why would this be and what would cause such a problem?

    Thanks.

  2. #12
    Join Date
    Mar 2010
    Location
    India
    Beans
    8,149
    Distro
    Ubuntu 12.04 Precise Pangolin

    Re: Ubuntu 12.04 not connecting to home wireless

    Quote Originally Posted by javeitch View Post
    However, what seems to kick-start the wireless connection is the "sudo iwconfig wlan0 power off" line. This seems (touch wood!) to be quite reliable. Why would this be and what would cause such a problem?
    Notebook wireless adapters often have a power saving mode to save battery power. It is supposed to kick in when there is no traffic (when the network is idle), and return to full (or optimal) power mode as soon as a traffic starts (network becomes active). However, certain driver/firmware bugs seem to fail to return (the device, or themselves) to active mode once they go to the idle mode.

    The "iwconfig <interface> power off" command tries to turn this automatic power management off on the mentioned interface, thus offering better stability at the cost of power saving feature. It is supposed to be permanent (although I'm not very sure about this), but the intel drivers seem to have their own power management techniques, so one has to use the above command on each boot (or when required) if these inbuilt power management techniques don't work well with the OS.

    Hope this gives a rough explanation of what happens and why. But this is just my own understanding, and I may be incorrect at some points.

    That being said, if you think that the "power off" command makes it stable, you can make it run automatically at startup. Just add it to the "/etc/rc.local" file, above "exit 0" line :

    1) Open the /etc/rc.local file as root -
    Code:
    gksu gedit /etc/rc.local
    2) Insert this line just above the last line "exit 0" :
    Code:
    sleep 20 && iwconfig wlan0 power off
    It is very important that the "exit 0" line remains the last line in the file ! Proofread, save and close the file.

    Since this file is run (at boot time) with root permissions, "sudo" is not needed. The "sleep 20" part makes sure that the command is run 20 seconds later after executing the file, thus allowing enough time for the wireless adapter to get ready. It may not be needed, but just to be extra sure..

    Keep us posted if anything interesting happens.
    Varun
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  3. #13
    Join Date
    Aug 2011
    Beans
    7

    Re: Ubuntu 12.04 not connecting to home wireless

    Thank you for that explanation. I appreciate all the help.

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