  Over the past decade we have witnessed a rapid growth and development in
wireless communication systems, to the point that conventional spectrum
allocation policies may not be able to fulfill them all. Federal Communications
Commission (FCC) licenses certain frequency segments to a particular user in a
particular geographic area. Industrial, Scientific and Medical (ISM) radio
bands have also been envisioned for all other unlicensed user to share, as long
as they follow certain power regulations. But with the recent boom in the
wireless technologies, these open channels have become overcrowded with
everything from wireless networks to wireless controllers.
  Therefore, the regulatory and standardization agencies have been working on
new spectrum regulation policies for wireless communication systems. The
underlying idea is to let unlicensed users to use the licensed band as long as
they can guarantee low interference to the licensed users. Though seemingly
simple, sophisticated interference management protocols are needed to meet the
expected level of transparency accepted by licensed users. In this report we
adopt the dynamic spectrum access approach to limit the interference to primary
users and analyze the performance of the cognitive MAC protocols based on
randomized sensing and access schemes.
