Cognitive Media Access Control

With the increasing demand of wireless communication and the fact of under utilization of wireless spectrum, a lot of researches have developed technologies to enhance the efficiency of spectrum utilization. The spectrum allocation chart by the Federal Communications Commission (FCC) (NTIA, 2003) indicates high degree legislation of frequency band, in other words, our sky is quite crowded. However, another study by FCC (Report & Order, 2002) also points out the fact that the conventional, fixed spectrum allocation policy is inadequate in addressing nowadays rapidly growing wireless communication. Vast temporal and geographic variations in the usage of allocated spectrum utilization ranging are from 5% to 75% below 3GHz while the spectrum utilization is even worse in the range above 3GHz. Generally speaking, many licensed spectrum blocks are idle at most of the time. These unused spectrum blocks are known as spectrum holes, which is defined in (Haykin, 2005) : A spectrum hole is a channel (i.e. frequency band) assigned to a primary user, but, at a particular time and specific geographic location, the channel is not being utilized by that primary user. To resolve the spectrum inefficiency in the more demanding reality, dynamic spectrum access (DSA) techniques are proposed to resolve the challenge of insufficient spectrum utilization as investigated in (Akyildiz et al., 2006) and (Jha et al., 2011).