Journal of Global Research in Computer Science (JGRCS)
Reference to the latest developments the spectrum shortage problems are because of the wireless communication. For the future networks the most practical, scientific and systematic challenges is the use of licensed or unlicensed wireless networks with opportunistic use of the spectrum with, without and limited rules. Since different wireless networks are using different frequency bands. So there is a need to use lessening bands when there is no activity on them. Cognitive radio is a new technology which leads to solve these problems through dynamically utilization of rules and spectrum.