Multilevel code-shifted differential-chaosshift-keying system

The M-ary differential-chaos-shift-keying (M-ary DCSK) system offers a good noise performance over an additive white Gaussian noise (AWGN) channel in the category of non-coherent detection chaotic systems. However, the way that the M-ary DCSK system utilises the available Walsh codes results in a relatively low bandwidth efficiency (BE). Moreover, the number of delay elements required at the transmitter and receiver increases exponentially with the number of bits per symbol. To overcome the aforementioned problems, the authors propose a multilevel code-shifted DCSK (MCS-DCSK) system in this study. In the proposed MCS-DCSK system, the reference chaotic signal and the information-bearing chaotic signals are orthogonal and are transmitted in the same time slot. They show that the MCS-DCSK system significantly outperforms the M-ary DCSK system in terms of BE and complexity. They also derive analytical bit-errorrate expressions for the MCS-DCSK system over additive white Gaussian noise and multipath fading channels, and verify them with simulation results.