What is Secondary Users

The goal of this chapter is to introduce the novel concept of cognitive radio (CR) for wireless telecommunications. Cognitive radios are a new type of radio devices that include cognition and reconfigurability features. The raising number of studies in different areas of research shows their potential and the expectation created among the telecommunications community. In this chapter, the authors first introduce the reader to the new paradigm that cognitive radio networks have created; more specifically, they explain in detail the new next generation networks. Given that our intention is to introduce cognitive radio, the authors focus on the challenges in PHY layer and MAC sublayer and the most relevant studies in these fields. Finally, the integration of game theory and cognitive radio creates a new paradigm where the advantages of both technologies merge to solve complex problems.