An M-ary code shifted differential chaos shift keying scheme

In this paper, by applying M-ary constellation modulation to code shifted differential chaos shift keying (CS-DCSK), a new M-ary DCSK which is called CS-MDCSK, is proposed. In the proposed scheme, the reference chaos signal is the same with the CS-DCSK, and the two orthogonal components of information bearing signal are obtained by two Walsh codes. Furthermore, the proposed CS-MDCSK is extended to general scheme (GCS-MDCSK), which transmits more than one M-ary constellation information bearing signals with one reference. Since high order constellations are used, the proposed scheme enhances the spectrum efficiency compared to CS-DCSK and GCS-DCSK. By computer simulations, the bit error rate (BER) performance of two proposed systems are compared to that of CS-DCSK and GCS-DCSK, respectively. Simulation results show that the proposed systems outperform the CS-DCSK and GCS-DCSK when 4-ary constellation is applied.