Wireless sensing function is missing?

[Kan Cai]

On Sat, 18 Mar 2006, Bruce M Simpson wrote:

> On Fri, Mar 17, 2006 at 02:00:28PM -0800, Kan Cai wrote:
>>   I wonder if this is true that sensing function is missing? If yes, is it
>> supposed to be implemented in the driver or net80211 layer? Thanks in
>> advance!
>
> It's a function of the 802.11 hardware. I assume you're describing the
> CSMA/CA technique. The Coordination Function (CF) in use will also have
> an effect but you don't specify if you're in IBSS or EBSS mode.

Yes, I meant CSMA. But I was actually using ralink card, which has 802.11 
firmware implemented in open source. I am aware that freebsd has a 80211 
layer as well. So before I dig into the source, I would appreciate it if 
anyone can let me know where CSMA is implemented, in the driver or 
net80211 provided by freebsd.

I tried both ad hoc mode and hostap mode, btw.

>
> How are you getting these figures anyway?

I use two threads broadcasting and receiving packets, and measure their 
rates every 10 seconds. Two nodes are put on the edge of transmission 
range, and then put garbage cans filled with paper (water might be better) 
around one node so that they can absorb signals and interfere the signal 
propagation.

This was just trying to verify if CSMA actually works. But as the data 
suggests that it seems that sensing isn't in place.

Thanks,
--ken

>
> Regards,
> BMS
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