Atheros, hardware access layer, collisions

Sam Pierson samuel.pierson at
Tue Jul 26 03:05:35 GMT 2005

> OK - you can probably achieve that by setting the retry limit to
> be 1, setting CWmin to be very small. However, you'll need to make
> sure that both machines transmissions are synchronised to better
> than 20us (which is no mean feat), otherwise carrier sense will
> foil your plan!

I just had a lengthy discussion with a couple of guys about the 802.11
protocol.   One had said that the random delays inserted before 
transmission was one of the *IFS delays (can't remember which
now), and that it was a standard 802.11 number, not a random 
delay.  We all came to the same conclusion as this list, that we 
have to set the transmission attempts to 1 and that CWmin must
be very small (like 1).  

The thing he said was that if carrier sensing "sensed" that the channel
was busy, it would not decrement the CW, effectively NOT transmitting
this packet until the channel is clear.  

Is the carrier sensing something done in the HAL, or is it embedded
in the hardware itself?

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