الفهرس 
Chapter 1 INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Most research in mobile communication proves that spectrum resources are not efficiently utilized in spite of the growth of using wireless network applications. Fixed frequency allocations do not meet high data rate wireless applications. So, in the last few years, the aim of most research focuses on how to efficiently use spectrum resources to cope with the revolution of using wireless high data rate applications. Research results proved that the best solution of this problem is cognitive radio (CR) network. Spectrum sensing plays an important role in CR network. It enables CR network to manage spectrum holes between licensed users and unlicensed users. The CR network senses the communication environment to detect free spectrum holes that can be used by unlicensed users. The CR network adapts its transmission parameters to allow unlicensed users to use licensed users’ holes. Unlicensed users must detect the presence of the licensed user to avoid any interference or bad effect on the licensed user communication. In this thesis, cooperative spectrum sensing and non-cooperative spectrum sensing based on energy detector are examined with a fixed sensing time. Moreover, an adaptive sensing time scheme is suggested to maximize the CR network throughput in cooperative spectrum sensing scenarios. Its idea is based on varying the sensing time according to the received signal-to-noise ratio (SNR) from the licensed users at the unlicensed users. Mathematical relations that relate the sensing time which achieves maximum throughput to the SNR are deduced for different decision fusion rules. Simulation results show that the fixed sensing time scheme does not provide efficient spectrum utilization for all values of SNR, while the proposed adaptive sensing time scheme maximizes the achievable throughput.
PUBLICATIONS
[1] Mohamed Abo Elhassan, Mohammed Abd-Elnaby, Sami A. El-Dolil, Fathi E. Abd El-Samie, “Adaptively Controlled Cooperative Spectrum Sensing Using OR Fusion Rule for Throughput Maximization in Cognitive Radio,” Wireless Personal Communications, DOI:10.1007/s11277-019-06234-z.
[2]Mohamed Abo Elhassan, Mohammed Abd-Elnaby, Sami A. El-Dolil, Fathi E. Abd El-Samie, “Throughput Maximization for Multimedia Communication with Cooperative Cognitive Radio Using Adaptively Controlled Sensing Time,” Multimedia Tools and Applications ,DOI: 10.1007/s11042-019-07782-z.