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I have an Acer laptop with Atheros AR928X wireless card installed, supported by ath9k driver in the linux kernel. There are other 5 computers sharing wireless connection via a TPLink 150Mbit/s wireless router. At first I found the network is a little bit slower than it's in Windows7, which I accepted as it should be. However a very strange thing is, each time I connected to the router and downloaded stuff for a while, one of the computers running Windows7 in my local network dropped off from the router. And if I run my laptop under Windows7, everything is fine. What's even stranger is although the network becomes slower, only the certain computer drops and totally freezes in connection with the router. I'm not willing to conclude it's due to the unhealthy connection from my laptop to the router, however we have confirmed this for more than one times and there is no problem with the network when I'm running WIndows7.

I'm extremely confused about what's going on. As a Linux user running Ubuntu over 5 years, I am awared that wireless driver in Linux is badly notorious of lack of stability and slow speed. But is it so bad that the unhealthy wireless connection can do damage to another computer in the same local network? I do see a lot of "Tx excessive retries" in iwconfig output. But how exactly does this happen ?

Thanks for your help. I guess I have to use this answer box to show the outputs

$ sudo iwconfig

wlan0 IEEE 802.11bgn ESSID:"TP-LINK111"

         Mode:Managed  Frequency:2.427 GHz  Access Point: E0:05:C5:E8:A9:92   
         Bit Rate=121.5 Mb/s   Tx-Power=16 dBm   
         Retry  long limit:7   RTS thr:off   Fragment thr:off
         Encryption key:off
         Power Management:off
         Link Quality=47/70  Signal level=-63 dBm  
         Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
         Tx excessive retries:2  Invalid misc:23   Missed beacon:0

To show what's wrong with the wireless connection, I ran iwconfig again within 3 minutes, during which time I hardly did anything and the network was not much busy than being nearly idle

$ sudo iwconfig

wlan0 IEEE 802.11bgn ESSID:"TP-LINK111"

         Mode:Managed  Frequency:2.427 GHz  Access Point: E0:05:C5:E8:A9:92   
         Bit Rate=121.5 Mb/s   Tx-Power=16 dBm   
         Retry  long limit:7   RTS thr:off   Fragment thr:off
         Encryption key:off
         Power Management:off
         Link Quality=48/70  Signal level=-62 dBm  
         Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
         Tx excessive retries:9  Invalid misc:28   Missed beacon:0

You can see Tx excessive retires and Invalid misc increase very quickly.

$ sudo iwlist wlan0 modu

wlan0 unknown modulation information.

$ sudo iwlist wlan0 channel

wlan0 13 channels in total; available frequencies :

         Channel 01 : 2.412 GHz
         Channel 02 : 2.417 GHz
         Channel 03 : 2.422 GHz
         Channel 04 : 2.427 GHz
         Channel 05 : 2.432 GHz
         Channel 06 : 2.437 GHz
         Channel 07 : 2.442 GHz
         Channel 08 : 2.447 GHz
         Channel 09 : 2.452 GHz
         Channel 10 : 2.457 GHz
         Channel 11 : 2.462 GHz
         Channel 12 : 2.467 GHz
         Channel 13 : 2.472 GHz
         Current Frequency:2.427 GHz (Channel 4)
share|improve this question
    
Well, logically, since only one out of four Windows machines drops out, the problem is with that machine and not with Ubuntu. Otherwise, why arent the other three drop out? Do you know what wireless mode the ath9k driver uses? 802.11n, 802.11g...? –  mikewhatever Nov 13 '12 at 11:00
    
Not exactly. When I'm running Windows7, everything is fine. By the way through search in google I found my wireless card is based on 802.11n Draft. And it's said somewhere there might be problem when several 11n clients coexist with a 11n draft client behind the same router. But this sounds too technical to me. –  funicorn Nov 14 '12 at 3:12
    
Alright, instead of arguing and jumping to conclusions, let us see some outputs: sudo iwconfig, sudo iwlist wlan0 modu, sudo iwlist wlan0 channel. Please add those to the question above, I have a theory that needs checking. Unfortunately, troubleshooting stuff can get a bit techical, don't know of any way to avoid that. –  mikewhatever Nov 14 '12 at 5:16
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