Wireless communications and the utilization of the radio frequency spectrum have witnessedrna tremendous boom during the past few decades. Given the limitations of the naturalrnfrequency spectrum, it becomes obvious that the current static frequency allocation schemesrncannot accommodate the requirements of an increasing number of higher data rate devices.rnCognitive Radio has come after several studies indicating that most of the allocated radiornspectrum is idle most of the time. As a result, spectrum regulation around the world is inrnprogress to allow unlicensed access in a non-interfering way. Cognitive radio is a candidaterntechnology for more efficient spectrum utilization systems based on opportunistic spectrumrnsharing. But to avoid interference, effective detection of primary users is a major issue ofrncognitive radio.rnIn this thesis work, various literature reviews on cognitive radio and detection theory byrndifferent authors which help to understand necessary theoretical background for thesis workrnhave been made. Performance of energy detector, replica correlation detector and cooperativerndetector has been evaluated using different performance metrics and the performance ofrnenergy detector has been enhanced. To evaluate the performance of the detection techniquesrnMATLAB software has been used for simulation.rnThe results of performance evaluation for the detectors have shown that the replicarncorrelation detector (delivers Pm of less than 1%) is better than energy detector (delivers Pm ofrnless than 10% but greater than 1%) under both AWGN and Rayleigh fading channel. But duernto fading, single node detection is unreliable and results in a high probability of missedrndetection and lower probability of correct detection. Thus, Rayleigh fading degrades thernperformance of single node energy and replica correlation detectors. It has been shown thatrncooperative detection helps to reduce the fading effect of single node detection and it isrnconcluded that cooperative spectrum detection outperforms single user energy detection andrnreplica correlation detector. Thus, the OR fusion rule of cooperative detection delivers betterrnperformance. In this paper, noise uncertainty has been shown to introduce considerablernamount of degradation in the detection performance of energy and replica correlationrniirndetectors. It has been also shown that cooperative detection helps to reduce the effect of noisernuncertainty factor in the overall detection performance of cognitive radio.rnFinally, this work proposes a new enhanced energy detector algorithm method. Itsrnperformance has been compared with standard squared law energy detector algorithm. ThernSimulation results indicate that the new energy detector algorithm method has betterrnperformance than square law energy detector. The enhanced energy detector deliversrnprobability of detection 12% better than square law energy detector.rnKeyword: cognitive radio, hypothesis test and spectrum detectorrn(energy, replica correlation and cooperative detector)