ATH rate and rssi considerations

JoaoBR joao at matik.com.br
Sat Feb 2 16:43:50 UTC 2008



I understand the difference between FBSD v.6 and v.7 regarding the RSSI value 
displayed by `ifconfig ath list stat` on a machine running ath as hostap and 
the reasons for this change but I think it is not so a very good idea at the 
end, I explain why.

BTW `ifconfig ath0 list ap` on the client station does it well, showing the 
signal strength and the noise level.

By only showing the RSSI value I have no chance to guess what is wrong with a 
station with a low rssi. Perhaps the client antenna is bad aligned or if 
interference or something else is drawing the rssi down. If I had the signal 
strength and it is good I could say it is not antenna alignment but something 
else by looking at the noise level. So now the sys-adm has a hard time 
figuring out what is going on.

At the end it is not only the cosmetic issue, in fact the signal strength of 
the ATH cards felt down, by 5-10 points or when looking at percentage, by 
almost 50%. This is measured on the client with any 11abg card and as well on 
freeBSD with the same ath card as on the AP.

*** I like to suggest that this is reconsidered and displayed as in FBSD v.6x 
or displaying S:N which than would be much more useful on an AP and making 
sense ***

At the same time the rssi change came up the RATE displayed when running OFDM 
as 11g or 11a went amok, any station which had before a at least 12,24 or 
higher RSSI felt down to 5.5 or often lower, most of them to 1 or 2M. Can you 
tell why ? In order to answer possible daughts, I change the AP which runs 
7-STABLE, lets say a 6.3 or a early 7-Stable (~07/2007) with same configs and 
wthout touching the antenas the RSSI comes back to normal and the noise leevl 
is less and at the end the signal strength measured on the client station 
(whatever 11a/b/g gear) almost doubles.




-- 

João







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