Toward Non-Coherent Chaotic Communications: An RIS-Aided Dual <i>M</i>-ary DCSK System

In this letter, we propose a reconfigurable intelligent surface (RIS)-aided dual M-ary differential chaos shift keying (RIS-DM-DCSK) system for non-coherent chaotic communications. In RIS-DM-DCSK, a dual M-ary DCSK signal is designed to transmit twice the number of modulated bits compared to a standard M-ary DCSK signal while permutation index modulation is employed to convey additional index bits, thereby enhancing energy efficiency. Furthermore, we propose a permutation index detection and dual M-ary DCSK demodulation algorithm to recover the transmitted bits. The bit error probability (BEP) of RIS-DM-DCSK is analyzed over a Rayleigh fading channel. Numerical results show that the proposed RIS-DM-DCSK achieves superior bit error rate (BER) performance and energy efficiency compared to benchmark schemes.