Carrier Interferometry Code Index Modulation Aided OFDM-based DCSK Communications

In this paper, we proposed a novel carrier interferometry (CI) code index modulation aided orthogonal frequency division multiplex (OFDM) differential chaotic shift keying (DCSK) communication system. In our design, we utilize the orthogonality property of CI codes matrix, and propose to transmit more information bits using the index of the CI codes matrix. The input information stream is divided into two subsets. One subset is modulated by the chaotic sequence and then spread by the information-bearing CI codes matrix which carries another information subset. At the receiver, the non-coherent chaotic demodulation and the maximum likelihood detection are respectively performed on these two subsets to retrieve the information. Since more bits can be transmitted while not requiring extra chaotic sequences and remaining the same overall energy, the energy efficiency is improved. Additionally, thanks to the spreading in the frequency domain achieved by the usage of CI codes, the peak to average power ratio (PAPR) can be suppressed. Moreover, theoretical performances including the energy efficiency, the bit error rate (BER) expressions are analyzed. Simulation results are provided to validate the theoretical analysis, and demonstrate the satisfactory PAPR and BER performances achieved by our design.