Abstract: Energy Efficient scheme in Cognitive radio networks (CRNs) has many advantages compared to the traditional networks. But the dynamic allocation of spectrum by enabling unlicensed users to use the licensed spectrum in a proficient manner is difficult for dynamic spectrum access. In this paper , we analyze and compare some of the existing works on energy efficient spectrum sensing in CRNs, We categorize the works as Energy based spectrum sensing scheme, Energy based MAC Scheme, Clustering,Resource allocation,green energy powered CR and Quality of service.We also present the advantages and disadvantages of these techniques and suggest a best energy efficient approach based on the observation.

Keywords: Cognitive Radio, MAC protocol, Spectrum Sensing, Quality of Service.