The Cognitive Radio (CR) is evolved as the potential technology to solve the problem of spectrum scarcity and to meet the stringent requirements of upcoming wireless services. CR has two distinct features, the spectrum sensing and the parameter adaptation. The former feature helps the CR to find the vacant spectrum slots/channels in the radio band while the latter mechanism allows it to adjust the operating parameters (e.g. frequency band, modulation and power, etc.) accordingly. The Primary User (PU) activity has serious effects on the overall performance of the Cognitive Radio Network (CRN).The CR should vacate the channel if it detects the arrival of the Primary User (PU) in order to avoid the interference.