[GRLUG] wifi connection drops under Ubuntu

[John-Thomas Richards]

On Thu, Apr 08, 2010 at 06:41:38PM -0400, Michael Mol wrote:
> On Thu, Apr 8, 2010 at 6:19 PM, John-Thomas Richards <jtr at jrichards.org> wrote:
> > I bought an Acer Aspire One for my wife.  It came with Win7 Starter
> > Edition.  W7SE is a dog.  I installed Ubuntu (full, not Netbook Remix)
> > on it.  It is much snappier than Win7.  However, wifi does not work as
> > well under Ubuntu as it does under Win7.  Win7 shows signal strength
> > around 85% and Ubuntu (NetworkManager) shows it around 42%.  Googling
> > has revealed that these figures may not be accurate.  I am inclined to
> > trust them since Win7 never experiences loss of network connectivity
> > whereas Ubuntu experiences frequent drops.
> 
> The actual "quality" measurement isn't so simple as a percentage; the
> driver itself will be reporting a signal strength in dB and a noise
> strength in dB. Your actual connection quality depends on your
> signal-to-noise ratio. That "percentage" is going to be some
> calculation based on those two numbers. If you drop into an xterm and
> run 'iwconfig (interface)', what does it say?

root at djr-laptop:~# iwconfig wlan0
wlan0     IEEE 802.11bgn  ESSID:"boston_celtics"  
          Mode:Managed  Frequency:2.462 GHz  Access Point: 00:18:39:B6:9B:2E   
          Bit Rate=54 Mb/s   Tx-Power=20 dBm   
          Retry  long limit:7   RTS thr:-Off   Fragment thr:-Off
          Encryption key:ECF6-C681-FC
          Power Management:-Off
          Link Quality=26/70  Signal level=-84 dBm  
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:0

> > I disabled power management
> > on the wifi card (thinking that perhaps Ubuntu is mistakenly reducing
> > the power to it in an effort to save power).  This does not eliminate
> > the loss of connectivity.  I am not sure what else to do, but no matter
> > what, I cannot tell my wife to just boot into Windows.  Any ideas?
> 
> Watch /var/messages and /var/syslog. There's likely something interesting there.

It just lost connection again.  dmesg shows multiple entries of this:

[ 1927.216729] ath9k: DMA failed to stop in 10 ms AR_CR=0x00000024 AR_DIAG_SW=0x40000020

> It's also possible that the Aspire One generates more EMI when running
> Ubuntu's drivers and policies than when running Windows' drivers and
> policies, based on configuration of the device. It may actually *help*
> to be more aggressive on power policies for things like your hard disk
> and CPU speed.

How could Ubuntu's drivers and policies result in more EMI?
-- 
john-thomas
------
A stereotyped but unconscious despair is concealed even under what are called
the games and amusements of mankind.
Henry David Thoreau, naturalist and author (1817-1862)