Design of a multi-carrier different chaos shift keying communication system in doubly selective fading channels

In this paper, a novel chaos modulation scheme, which combines code-shifted differential chaos shift keying (CS-DCSK) with orthogonal frequency division multiplexing (OFDM) is presented, namely OFDM-CS-DCSK. In the proposed scheme, the reference signal and the information bearing signal of CS-DCSK are firstly formed by Walsh code sequences, then different chips of the CS-DCSK signal are mapped onto different subcarriers of OFDM. Utilizing the characteristics of OFDM and CS-DCSK, the proposed scheme has robust performance over time-frequency doubly selective fading channel. In addition, the proposed system has low complexity because channel estimation, channel equalizer and the radio frequency (RF) delay circuits are not required at its receiver. By the computer simulations, bit error rate (BER) performances of the proposed scheme are compared with OFDM-DCSK and CS-DCSK under various channel parameters. Simulation results indicate that the proposed scheme has significant performance advantages over OFDM-DCSK and CS-DCSK in time-frequency doubly selective fading channel.