الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 112 |  |  |
| | | from | 112 | | |
Abstract
Nowadays, the demand for wireless communications is growing rapidly due to the required ease of access and availability requirements in the open markets. Securing this type of communications against different attacks is a very important issue. The reliability standard of such a communication system plays an important role in many applications, especially, in military applications. Several studies have proved that orthogonal frequency division multiplexing is a robust technique against several channel impairments and that makes it a core technique in the famous fourth generation mobile communication system. A jammer is a form of attacking that tries to interrupt the signal reception by injecting an interfering signal with high power in the same systems’ utilized band. Specifically, this thesis presents the effect of employing a sub-band hopping technique combined with orthogonal frequency division multiplexing (OFDM) system under the influence of various jamming strategies. In this thesis, OFDM sub-band hopping system is done using bit error rate (BER) metric in the presence of jamming attacks is obtained. This includes two different hopping strategies, which are 3-bands hopping and 6-bands hopping, and two channel models, the additive white Gaussian noise (AWGN) and Multi path Rayleigh fading. It also includes various jamming models, that fluctuate from small narrowb and jammer up to barrage jammer. The narrow-band jammers have the smallest decrease of the BER system performance when the signal to jamming power ratio (SJR) has low values (i.e. SJR ˂ 0dB). This performance degrades with the increase of the jammed bandwidth. Otherwise, at higher values of SJR (i.e. SJR ˃ 0dB), the BER system performance gets better values through applying wide-band jammers and this BER performance is decreased when narrow-band jammers are injected.