Re: [Discuss-gnuradio] BBN 802.11-b project - MAC Layer issue

[Doug Geiger]

Juan Ramon Gutierrez Agullo wrote:
> Hello
>
> I've been analyzing the BBN project code (trunk and branches versions)
> and I can't understand how is the MAC layer working. 
> As the standard 802.11 says, the minimal functionality is CSMA/Carrier
> Avoidance but I haven't seen any implementation in this project.
>
> Which part of the MAC is developed? I see 3 files only (in src/80211mac
> folder):framing.py, simple_mac.py and mac_utils.py but I can't see where
> the code does some 802.11 MAC tasks as Back-Off, where is testing the
> medium and decide if it's busy or not, ...
>
>
>   
As far as my understanding goes, there is not a complete implementation 
of the 802.11b-spec MAC. The files you've found are, to the best of my 
knowledge, the only released code out there implementing a partial MAC 
(i.e. it performs some carrier-sensing functions in an attempt to avoid 
collisions), but I don't believe anyone has a real, compliant MAC 
working (or at least has not released one to the world). In particular, 
I think making the timing requirements of the SIFS and DIFS would be 
extremely difficult to achieve, although I don't know if anyone has 
performed any in-depth latency measurements with the USRP2 as has been 
done with the USRP1.
Doug

--
Douglas Geiger
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U.S. Naval Research Laboratory
Washington, DC 20375
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