With the constant advances in wireless technology, radio spectrum has become a very scarce resource. Cognitive Radio (CR) has emerged as a viable way to deal with our inefficient use of the radio spectrum by utilizing unused spectrum holes or white spaces, as they are referred to. Using Software Defined Radio (SDR) we are able to realize CRs and their unique properties. Most of the research that has been done on CR protocols has been based on analytical assessments and simulations using non-CR specific network simulators. In this paper we code and compare two existing CR specific Medium Access Control (MAC) protocols using a CR specific simulator. We then prototype the chosen protocols using the Universal Software Radio Peripheral (USRP). This allows us to see how close the simulated performance results come to those actually achieved in a real prototype.