الفهرس 
Electronic Warfare and JammingOnly 14 pages are availabe for public view
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Abstract
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 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.