Chaotic Frequency Hopping

Ahmed El Sayed Ali Hassan Mansour


Spread spectrum techniques are used to improve the communication systems transmission in the presence of multiple different impairments such as interference, fading, jamming and security issues. The spread spectrum is categorized into direct sequence spread spectrum (DSSS), time hopping spread spectrum (THSS) and frequency hopping spread spectrum (FHSS). The FHSS is widely used in the military applications because of its capabilities to mitigate the jamming and interference effect. Adaptive frequency hopping (AFH) is developed to improve the bit error rate (BER) performance in the presence of fading and jamming environments by selecting the best sub-channels and ignore bad sub-channels. However, chaotic frequency hopping (CFH) is used to enhance the randomness of the hopping pattern and the auto-correlation and the cross-correlation between different users due to the sensitivity to the initial conditions and the non-repetitive features. To exploit the merits of both techniques (AFH and CFH), we proposed two models that combine the good properties of chaotic maps and the high (BER) performance of adaptive frequency hopping systems to accomplish a robust communication system in the presence of jamming and interference environment. The first proposed model is adaptive chaotic frequency hopping (ACFH) that synthesizes a 1-D chaotic map according to the channel status to generate the hopping pattern. The second model is the cross-coupled chaotic frequency hopping (CCCFH) that uses the cross-coupled logistic maps with matched frequency hopping (MFH) scheme to generate the hopping pattern. The BER performance of the proposed models is simulated and compared with advanced I matched frequency hopping (AMFH) scheme in the presence of different interference and jamming scenarios. The ACFH model has better frequency diversity hence, it has better performance in case of jamming environment. However, CCCFH has better BER performance in jamming environment compared with convention MFH because CCCFH uses all the sub-channels to achieve better frequency diversity. Key words: Spread spectrum, adaptive frequency hopping, fading channel, synthesized chaotic maps. II

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Other Titles إستخدام الدوال الفوضویة في نظام القفز الترددي
Issue Date 2016

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