Date Added: Nov 2011
Cognitive Radio Networks (CRNs) consist of Primary Users (PUs) and Secondary Users (SUs), in which SUs sense the licensed spectrum bands and opportunistically access them without interfering operations of PUs. PUs in a primary network are usually licensed to access a spectrum band. SUs in a secondary networks sense available opportunity to access in licensed bands in absence of PUs. For a network designer, designing a cognitive radio network is complex process and need to consider many challenging aspects. There exist several issues to be addressed in these kinds of networks. In this paper, cooperative approaches to spectrum sensing and sharing for CRNs are investigated and qualitatively compared with each with respect to various on design issues.