Cognitive Radio Networks (CRNs) are emerging as a solution for maximising cumulative spectrum usage in radio environments by using idle or underutilised airwaves. The fundamental idea is to provide unlicensed users access to permitted spectrum as long as disturbance to licenced users is kept to a minimum. To make better use of the spectrum and increase spectrum utilisation, new communication and networking technologies must be created. This means that a number of technological issues must be resolved beforethis technique can be used. Dynamic Spectrum Access (DSA), architectural problems (with a focus on network reconfigurability), the deployment of smaller cells, and security are the most pressing concerns. Given that 3G Long Term Evolution (LTE) pilots and4G Long Term Evolution -Advanced (LTE-A) are now operational, Today, it appears that 5G will emphasis on architectural and networking features rather than faster carrier than 4G. Pervasive wireless computers and communications, cognitive radio technology, IPv6, wearable gadgets with Artificial Intelligence (AI) capabilities, and a uniform global standard are among the key 5G characteristics predicted. Wi-Fi and Bluetooth protocols are predicted to be available as radio applets by 2020, resulting in new technological advancements as well as new opportunities.