Performance Evaluation on Transmitter Detection Techniques for Cognitive Radio

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Addis Ababa University


Wireless communications and the utilization of the radio frequency spectrum have witnessed a tremendous boom during the past few decades. Given the limitations of the natural frequency spectrum, it becomes obvious that the current static frequency allocation schemes cannot accommodate the requirements of an increasing number of higher data rate devices. Cognitive Radio has come after several studies indicating that most of the allocated radio spectrum is idle most of the time. As a result, spectrum regulation around the world is in progress to allow unlicensed access in a non-interfering way. Cognitive radio is a candidate technology for more efficient spectrum utilization systems based on opportunistic spectrum sharing. But to avoid interference, effective detection of primary users is a major issue of cognitive radio. In this thesis work, various literature reviews on cognitive radio and detection theory by different authors which help to understand necessary theoretical background for thesis work have been made. Performance of energy detector, replica correlation detector and cooperative detector has been evaluated using different performance metrics and the performance of energy detector has been enhanced. To evaluate the performance of the detection techniques MATLAB software has been used for simulation. The results of performance evaluation for the detectors have shown that the replica correlation detector (delivers Pm of less than 1%) is better than energy detector (delivers Pm of less than 10% but greater than 1%) under both AWGN and Rayleigh fading channel. But due to fading, single node detection is unreliable and results in a high probability of missed detection and lower probability of correct detection. Thus, Rayleigh fading degrades the performance of single node energy and replica correlation detectors. It has been shown that cooperative detection helps to reduce the fading effect of single node detection and it is concluded that cooperative spectrum detection outperforms single user energy detection and replica correlation detector. Thus, the OR fusion rule of cooperative detection delivers better performance. In this paper, noise uncertainty has been shown to introduce considerable amount of degradation in the detection performance of energy and replica correlation ii detectors. It has been also shown that cooperative detection helps to reduce the effect of noise uncertainty factor in the overall detection performance of cognitive radio. Finally, this work proposes a new enhanced energy detector algorithm method. Its performance has been compared with standard squared law energy detector algorithm. The Simulation results indicate that the new energy detector algorithm method has better performance than square law energy detector. The enhanced energy detector delivers probability of detection 12% better than square law energy detector. Keyword: cognitive radio, hypothesis test and spectrum detector (energy, replica correlation and cooperative detector)



cognitive radio, hypothesis test and spectrum detector, energy replica correlation and cooperative detector