What is Cognitive Radio Network (CRN)

Software Defined Radio (SDR) and Cognitive Radio (CR) are the key enabling technologies to overcome the spectrum scarcity problem a bit, by supporting dynamic spectrum access in which either a network or a wireless node reconfigures its transmission or reception parameters to communicate efficiently, avoiding interference with licensed or unlicensed users. CR senses the environment and enables a secondary system to share the licensed spectrum with the primary system, which usually has exclusive access. The performance of the secondary system could be enhanced by Cooperative Spectrum Sensing (CSS) as it increases the primary detection probability. Again cognitive radio network greatly benefits from a cooperative transmission, employing intermediate nodes as relays. This chapter is focused on software defined radio, its architecture, limitations, then evolution to cognitive radio network, architecture of the CR, and its relevance in the wireless and mobile ad-hoc networks. Additionally, an overview of Cooperative Spectrum Sensing (CSS), its classification, components, challenges, and Cooperative Relay are discussed.