Analysis of signal processing based spectrum sensing practices in cognitive radio: A review

Radio frequency spectrum is a natural resource that has restricted existence and this constraints it to be used logically, efficiently and frugally so that equitable access can be made available to the spectrum users for various radio communication services. With advancement of wireless communications, the issue of bandwidth usage has turned out to be more conspicuous. To resolve the issue, Cognitive Radio technology has come out as a way, by permitting the unlicensed or opportunistic users to use the licensed bands. Cognitive radio (CR) based systems and networks are constructed grounded on software defined radio, a novel architecture and have extensive signal processing capabilities for sensing spectrum underutilization and easing network congestion by efficiently distributing spectrum resources, which are exiguous and expensive, by dynamically allocating the spectrum to multiple users (Licensed/Unlicensed). Spectrum sensing empowers the cognitive radio to search for the available free bands in the form of spectrum holes so that they can be utilized by Secondary Users (SUs) leading to minimize the spectrum scarcity. But practically, inadequacies such as signal/noise ambiguity, channel/interference ambiguity, transceiver hardware deficiencies, synchronization/calibration problems, etc. may severely descend the execution of a CR system. This paper reviews the concept of cognitive radio, performance metrics, imperfections that may degrade the performance and some existing signal processing based spectrum sensing techniques with their merits and demerits.