Mohammed, AbdoNgist, Fentie2021-11-262023-11-282021-11-262023-11-282021-07http://etd.aau.edu.et/handle/12345678/28964A radio spectrum is a particular range of frequencies used to communicate information in a wireless communication system. It is naturally available and scarce resource. Besides to, the dramatically increase of the wireless communication system is a critical issue and the studies show that a certain licensed spectrum are underutilized. To solve this problem the cognitive radio is a key technology when there is a free spectrum band of the licensed users then the cognitive radio system permits that band for unlicensed or secondary users. In addition to that the cognitive radio system continuously monitors at the range of primary user transmission to minimize the interference by the secondary user’s whole opportunistically occupies on the licensed bands. For this task the cognitive radio uses different spectrum sensing methods to avoid the undesirable interfering and recognize the accessible radio spectrum band for secondary users (SUs). In this thesis, the performance of the Spherical and John’s detector spectrum sensing methods in the presence of one and two primary users by implementing it over the typical Rayleigh fading channel is investigated. The performance of probability of detection and Receiver Operating Characteristics (ROC) curves within low signal-to-noise ratio (SNR) range is compared. Using the MATLAB software with the Monte Carlo techniques are used to evaluate and analysis of the performance of this work. The implementation part shows a detailed comparison between the Spherical detector (SD) using General Likelihood Ratio Test (GLRT) estimator and John’s detector (JD) using Locally Best Invariant Test (LBIT) estimator including a single and two primary user (PU) transmitted signals of detection. The specific, result shows the performance efficiency of detection for both schemes with a tolerable interference level under the fading channel. The proposed system uses GLRT estimator for SD and LBIT estimator for JD. After doing the experiment, the result showed that JD provided the better detection performance over SD. To illustrate this, when two PUs are detected by four SUs in cooperative scheme using SD method at SNR range of [-2, -1] dB, the result is found to be incremented from 99.7% to 99.8%. The same experiment is done using JD method and the result shows that the detection performance is in the range of 99.9% and 100%.en-USSpectrum SensingSpherical DetectorJohn’s DetectorRayleigh Fading ChannelLow SNRThesis