Analytical Evaluation of a Hybrid Chaotic Shift Keying [CS-QCSK] in a CDMA System

In recent years, various chaos based modulation schemes were evolved, of which the CS-DCSK modulation technique provides a better BER performance and bandwidth efficiency, due to its code domain approach[10]. The QCSK modulation technique provides double benefit, namely: higher data rate with similar BER performance and same bandwidth occupation as DCSK. By combining the advantage of code shifted differential chaos shift keying (CS-DCSK) and Quadrature chaos shift keying (QCSK) scheme, a novel CS-QCSK modulation scheme called code shifted Quadrature chaos shift keying is proposed. The noise performance of CS-QCSK is better to most conventional modulation schemes and also provides an increased data transmission rates with greatly improved robustness. Analytical expressions for the bit-error rates are derived for both AWGN channel and Rayleigh multipath fading channel. The simulation result shows that the proposed method outperforms the classical approaches in terms of bit error rate and spectral efficiency.