• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.10
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• pp.1183-1188
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• 2015

The FM-QCSK(: Frequency Modulated Quadrature Chaos Shift Keying) system is one of the most efficient systems in chaotic literature. One of the problems in this system is that half the bit duration is used for sending a chaotic reference signal which leads to increase the energy losses and reduces the data rate. In this paper, a novel scheme to enhance the performance of FM-QCSK system has been proposed. With the proposed scheme, FM-QCSK would be able to operate at higher data rates with reduced BER(: Bit Error Rate) and energy consumption. The basic modification introduced by the proposed scheme is the use one reference chaotic signal to transmit multi information signals in both in-phase and quadrature-phase channels. The results showed that the proposed scheme have achieved more than 3 dB gains in SNR for AWGN channels respectively at $BER=10^{-3}$ over the conventional one. The results also showed that the optimum number information signals can be send per reference signal is 8.

• Journal of the Institute of Convergence Signal Processing
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• v.8 no.1
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• pp.44-50
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• 2007

In this paper generating algorithms of the conventional chaos code sequences and a new chaos code sequence derived from the real and imaginary parts of FFT of one chaos code sequence, and the time-frequency function characteristics of generated code sequences to measure the signal resolution, are considered. And two chaos based QCSK digital communication systems-one with two different chaos code sequences, the other with FFT of one chaos code sequence-are analyzed in AWGN and fading communication channels. After analyzing the correlation functions of such sequences, the delta-like autocorrelation and near zero crosscorrelation functions of them are very suitable for chaos based spread spectrum communication systems, is verified. Through evaluating the performance of two chaos based QCSK systems above using Monte-Carlo simulation, the improvement of performance in the latter QCSK system compare favorably with that of the former system, is shown.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.11a
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• pp.361-361
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• 2004