Date Added: May 2013
Cognitive Radio (CR) is a promising technology that can alleviate the spectrum shortage problem by enabling unlicensed users equipped with CRs to coexist with incumbent users in licensed spectrum bands without inducing interference to incumbent communications. Spectrum sensing is one of the essential mechanisms of CRs that has attracted great attention from researchers recently. Although the operational aspects of spectrum sensing are being investigated actively, its security aspects have garnered little attention. In this paper, the authors have shown all the spectrum sensing techniques used to detect the primary user in non cooperative system. Here they have analyzed all the existing sensing techniques and done a comparative survey of the sensing techniques.