Cognitive Radio (CR) systems are the upcoming technology in the wireless communication where they have to utilize their spectrum available in the best and the efficient way. The tasks to be covered in the CR technology are broadly classified into two categories. They are efficient utilization of the available spectrum and secondly energy efficiency in the wireless transmission. As said above that in the wireless communication system they have major two challenges are to utilize the spectrum efficiently by also keeping in mind that the least power gets wasted during this process.