Cognitive Radio Ad Hoc Networks (CRAHNs) constitute a viable solution to solve the current problems of inefficiency in the spectrum allocation, and to deploy highly reconfigurable and self-organizing wireless networks. Cognitive Radio (CR) devices are envisaged to utilize the spectrum in an opportunistic way by dynamically accessing different licensed portions of the spectrum. However the phenomena of channel fading and primary cum secondary interference in cognitive radio networks does not guarantee application demands to be achieved continuously over time. Availability of limited spectrum and the inadequate spectrum resource usage necessitates a new communication standard to utilize the existing wireless spectrum opportunistically. This paper discusses currently existing mechanism for providing better efficiency by utilizing cognitive network intelligence. The frequencies used are utilized to the maximum extent without any interference. This paper aims in comparing the techniques used for enhancing the throughput in CR.