[CUWiN-Dev] 802.11 beacon strength oscillation

[David Young]

On Thu, Jul 21, 2005 at 12:02:03PM -0500, Bill Comisky wrote:
> 
> I've been trying to do some crude QA on our nodes before they go out the 
> door; a sanity check to make sure everythings working (pigtail is 
> connected, etc).  So I've been plugging them in at one end of our lab 
> space, and looking the received beacon strength at another node at the 
> other end of the lab with:  tcpdump -ne -y ieee802_11_radio
> 
> Somes nodes show a steady ~65dB signal level, while a sizable percentage 
> have beacon levels that alternate between ~45dB and ~65dB, maybe every 
> 20-30 packets.  The behavior seems tied to the radio, switching the radio 
> could change the behavior.  I haven't started bandwidth testing to see if 
> there is any difference, but wanted to see if anyone knew if perhaps this 
> was normal (an 802.11 "thing") or could offer an explanation..

Another possibility is receive diversity.  Does the antenna alternate
between 1 and 2?  You can see that with 'tcpdump -ne -y ieee802_11_radio
-i ath0', there is an 'antenna X' field for transmit & receive.  It should
always be 1 or 2 for rx, and 0, 1, or 2 for tx.  0 means "hardware chose
tx port."

Dave

-- 
David Young             OJC Technologies
dyoung at ojctech.com      Urbana, IL * (217) 278-3933