Cognitive radio networks (CRN) is IEEE 802.22 standards, put together named as 5-G wireless technology. CRN carries primary users (PU) or authorized users and secondary users (CR) or unauthorized users. Throughout this paper, we’ve got given associate define of CRN, further, we’ve got a bent to tend to dialogue CRN functions. There area unit varied sensing techniques that we’ve got a bent to tend to classify and discuss, and extra, analyze the problems associated with CRN. Finally, we’ve got a bent to tend to conclude that every sensing technique has its own edges and dis advantages.

Keywords : Cognitive Radio Network, Primary user, Cognitive Radio User, Spectrum Sensing, SNR