الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Cognitive radio (CR) has been proposed as a methodology for overcoming the
inefficiency of the conventional static allocation of the available spectrum in wireless communication networks. To overcome this issue, transition from static spectrum
allocation policies to dynamic spectrum access methodologies was implemented. As a result, the CR concept has been introduced to solve the problem of the frequency
bandwidth under-utilization. CR technology provides a solution to the abovementioned problem by allowing unlicensed users to access the licensed bands
opportunistically when those bands are not occupied by the original users.
Spectrum sensing is the main and vital step in CR systems; so that the CR
users/secondary users (SUs) could be able to utilize the holes overcoming any interference with the licensed users/primary users (PUs). Various developments have been done in spectrum sensing techniques to accurately sense the presence or absence of a licensed user. Energy detection (ED) is one of the most common and easiest spectrum sensing techniques for CR. Spectrum sensing suffers from many challenges.
One of the most crucial challenges of spectrum sensing is noise uncertainty and channel uncertainty.
In this thesis, performance metrics and traditional ED receiver operating characteristic (ROC) curve are simulated using Monte Carlo simulation under consideration of additive white Gaussian noise (AWGN) and a fading environment. Also, the efficiency of ED is analyzed under binary phase shift keying (BPSK) modulation
technique using single threshold (ST), ED based adaptive double threshold (ED-ADT) and cooperative spectrum sensing based adaptive double threshold (CSS-ADT). The
efficiency study will carry the assumption of noise uncertainty. Moreover, the relation between the number of samples and the signal to noise ratio wall (SNR wall) is
proposed and simulated. To minimize the unreliable performance of ED due to noise uncertainty; the dynamic threshold is used. The analytic form for the detection and false alarm probabilities are provided in case of noise uncertainty. The simulation
results of weighted ED is compared by conventional ED with noise ncertainty. By analysis, the optimal threshold is used to reduce the effect of random nature of PU and noise uncertainty. Finally, the execution of ED technique in the time domain and frequency domain is designed on a Universal Software Radio Peripheral (USRP) software defined radio
(SDR) device with model number (USRP-2942R) by using Laboratory Virtual
Instrument Engineering Workbench (LabVIEW) which is a system-design platform and development environment for a visual programming language from National Instruments. This includes sensing the spectrum and allocating the SU to an appropriate band in order to achieve efficient utilization of the frequency bandwidth and also prevent any interference.