A Study of Cognitive Radio Networks

Abstract

Cognitive radio networks are emerging as a new concept of channel access and sharing in wireless networks. The aim is to exploit the residual bandwidths on the underused frequencies of the frequency spectrum. Indeed, several studies have revealed that radio bands are not used optimally since it has been noticed that the spectral band free of access (the frequencies used by WiFi for example) become overloaded while others tapes remain largely underutilized. RRCs form a new family of radio users who attempt to exploit underutilized frequency bands during the absence of primary users and release the channel as soon as the licensed users of these frequencies attempt to access it. Most of the studies done today have looked at one-leap scenarios in which one focuses on the mechanisms of the physical and MAC layers necessary to ensure cohabitation between cognitive networks and already existing primary networks such as the access control and spectra sharing. But in recent times, the research society is in progress to realize the potential in multi-hop DRRs which can provide new service potential for a wide range of ubiquitous communiqué applications. This scheme presents the existing challenges, the three types of cognitive environments, and the proposed approaches to resolving the routing difficulties in multi-hop cognitive radio networks.