[ath9k-devel] TX power control, WAS: Rate Selection problems in mixed 802.11b/802.11g IBSS

[Joerg Pommnitz <pommnitz@yahoo.com>]

Luis,
I'm retracting my observation. Trying to reproduce it with the
logs you asked for did show that the ath9k node tried to increase
the tx data rate from time to time and that the signal strength
was very low. I don't quite understand this, but now I do not
think that the RC algorithm is to blame.

Another question popped up, however. I'm evaluating ath9k and
Atheros 802.11n cards for a project we are working on. Together
with a co-worker we did some measurements of the tx power. What
we found is, that using iwconfig to change the tx power had no
measurable effect on the tx power on the antenna port. Even if I
configured the tx power down to 1db the measured value remained 
constant at 27mW.
So, tx power control seems not to be implemented in ath9k. Is this
correct and if so, will this change?

 -- 
Regards 
Joerg 




----- Urspr?ngliche Mail ----
> Von: Luis R. Rodriguez <mcgrof@gmail.com>
> An: Joerg Pommnitz <pommnitz@yahoo.com>
> CC: ath9k-devel at lists.ath9k.org
> Gesendet: Dienstag, den 17. November 2009, 18:07:12 Uhr
> Betreff: Re: [ath9k-devel] Rate Selection problems in mixed 802.11b/802.11g IBSS
> 
> On Tue, Nov 17, 2009 at 12:34 AM, Joerg Pommnitz wrote:
> > Hello all,
> > I have seen a problem using ath9k in an IBSS network formed from
> > two nodes: one AR5xxx running Madwifi and one A9xxx using ath9k.
> >
> > The network was running on channel 14 which Madwifi limits to 802.11b
> > for regulatory reasons (we have permission to use this channel).
> >
> > The strange part was ath9k: Using "iwdevwlan0 stations dump" I could see
> > that the TX rate to the Madwifi node was stuck at 1 Mbit/s. An iperf run
> > confirmed the miserable data rate. I could force
> > the rate with "iwconfigwlan0 rate 11M" to something reasonable (once again
> > measured with iperf). In the latter case, iw still claimed a TX rate of 
> 1Mbit/s
> > but iperf did show the expected data rate.
> >
> > The Madwifi node on the other end was happily selecting 11Mbit/s on its own.
> >
> > Any ideas?
> 
> Yeah I'm curious can you try on the ath9k station:
> 
> iw list
> 
> And then please try monitoring the rcstat file as root:
> 
> watch cat /sys/kernel/debug/ath9k/phy0/rcstat
> 
> When you run iperf what rates do you see being used? After a while of
> running iperf (3 times) with UDP:
> 
> iperc -c ip-address-of-server -u -i 1 -b 30M
> 
> please paste the output of the rcstat file.
> 
>   Luis


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