Protocol Media access Controler
I think a bit more detail explaining the MAC layer would have been better rather than just using the word Protocol because it makes the article difficult to understand
Airshark is an experimental application bringing detect-and-avoid frequency-hopping to previously dumb Wi-Fi cards, without the addition of any new hardware. Created by three boffins at the University of Wisconsin, Airshark uses the limited intelligence of existing Wi-Fi cards to spot other protocols hanging out in the 2.4GHz …
"This kind of thing is already possible, but only using spectrum analysis hardware that would be prohibitively expensive to put into a Wi-Fi router."
Someone should tell AVM. Their Fritz! wireless routers have been showing interference from other sources in the WiFi bands at the click of a checkbox for some time. They'll be delighted to hear that this is actually impossible without a load of expensive kit they don't provide.