802.11 for Gnuradio?

Hi,
I am interested in using USRP + Gnuradio as a Cognitive Radio. I wish to
apply learning algorithms to an 802.11 style MAC and evaluate the
response of the radio for using unused spectra.

Is there an 802.11 style MAC protocol (i.e. RTS/CTS) for Gnuradio out
there? I could begin using this as a base.

Alternatively are there any pointers or considerations I should heed if
I need to code the MAC from scratch?

I have looked at the BBN, ACERT 802.11 code but they appear to be mainly
concerned with the physical layer and only define the frame structure. I
have read the paper “Enabling MAC Protocol Implementations on
Software-Defined Radios” by George N., which examines problems
Gnuradio has implementing a practical MAC Protocol. George N. writes
that he implemented an 802.11 style protocol in this paper.