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
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Douglas G.
Code 5545
U.S. Naval Research Laboratory
Washington, DC 20375
(202) 767-9048 [email protected]