Design of High data Rate FM-QCSK Chaotic Communication System

The frequency modulated quadrature chaos shift keying FM-QCSK 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 bit-error probability BER and energy consumption. The basic modification introduced by the proposed scheme is the use one reference chaotic chip to transmit multi information-bearing chips in both in-phase and quadrature-phase channels. The results showed that the proposed scheme have achieved more than 3 dB and 5 dB gains in SNR for AWGN and Rayleigh multipath fading channels respectively at BER=10-3 over the conventional one. The results also showed that the optimum number information-bearing chip can be send per reference is 8. The theoretical expression of BER in AWGN channel has also been derived for the proposed scheme.