Unstable wifi connection after 14.04 upgrade

[shaansweb]

Hello,

After I upgraded my PC to Ubuntu 14.04, the connection has been really unstable. The connection frequently drops, fails to connect, or is very slow. This does not occur in Windows 8. The result's to varunendra's scirpt that I have seen people using on this forum are attached. Does anybody have any idea how I can fix this, or at the very least diagnose the problem?

I also temporarily put the result of the script on pastebin in case you don't want to download the attached archive

http://pastebin.com/KCV5R16Z

Thanks in advance.

[praseodym]

Hi,

deactivate the N-mode of the driver (bug):

echo "options iwlwifi 11n_disable=1" | sudo tee /etc/modprobe.d/iwlwifi.conf
sudo modprobe -rfv iwlwifi
sudo modprobe -v iwlwifi

Additionally you can deactivate the power management of the card:

sudo iwconfig wlan0 power off

[shaansweb]

Thanks!! I'm getting "modprobe: FATAL: Module iwlwifi is in use." when I run "sudo modprobe -rfv iwlwifi" but the other three commands seem to have improved things. Can you (or anyone reading this) please explain to me what exactly those commands did? What is the N-mode of the card?

[praseodym]

There are different modes your router provides (or could provide depending on the model): a, b, c, g and n. Here, the N-mode of the driver is buggy. You can check the router manual

[chris214]

I even tried newer kernels (3.15.0-031500rc3) but the issue persists.
Disabling N mode "fixed" the issue for now.

[chris214]

I take it back...disabling N mode does not fix the issue.
Looking at iwconfig, I have extremely high Invalid misc packet count. Right now, it is over 3,000, and my uptime is 5 minutes. After a few hours of browsing, it is well over 600,000.

[kenjiru]

Disabling N mode worked for me.

radu@sasuke:~$ iwconfig
wlan0     IEEE 802.11abg  ESSID:"FOO"  
          Mode:Managed  Frequency:2.462 GHz  Access Point: 28:BE:9B:05:7E:68   
          Bit Rate=54 Mb/s   Tx-Power=15 dBm   
          Retry  long limit:7   RTS thr:off   Fragment thr:off
          Power Management:off
          Link Quality=50/70  Signal level=-60 dBm  
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:1093   Missed beacon:0

radu@sasuke:~$ uptime
 23:56:59 up  3:13,  2 users,  load average: 0,29, 0,46, 0,47

I hope they will fix the 802.11n mode, as it's really annoying to use a slower speed.

[rrohde]

This issue still persists with the latest beta of Ubuntu 14.10... You'd think that would be resolved; such a basic functionality of an OS. Hate to having to boot into Windows just to get persistent wifi connectivity.

[phottomatt]

This did not work for me, I may need additional help here. Sometimes I don't even get a list of available WiFis.

wlan0     IEEE 802.11g  ESSID:off/any  
          Mode:Managed  Frequency:2.437 GHz  Access Point: Not-Associated   
          Bit Rate:1 Mb/s   Sensitivity=-200 dBm  
          RTS thr=2346 B   Fragment thr=2346 B   
          Power Management:off
          Link Quality:0  Signal level:0  Noise level:0
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:0


lo        no wireless extensions.


eth0      no wireless extensions.


usb0      no wireless extensions.

[praseodym]

Change the mtu value to 1500 instead of "Automatic" in the network manager profile