Design of an improved multi-carrier DCSK system for digital communications

In this paper, we propose a differential chaos-shift keying (DCSK) system using multi-carrier modulation (MCM), namely improved multi-carrier DCSK (IMC-DSCK), which can be considered as an improve version of conventional (MC-DSCK) system. Instead of transmitting the chaotic spreading sequence on a predefined subcarrier as in the conventional MC-DCSK, in the proposed system, a DCSK-modulated signal is sent via this subcarrier. The remaining parallel bit streams are multiplied with the same repeated reference sequence and then sent by the corresponding subcarriers. In the receiver, the repeated reference is retrieved from the signal on the predefined subcarrier and used for the demodulation. Structure and operation of the IMC-DCSK system are designed and described. Bit error rate (BER) performance under AWGN and Rayleigh fading channels is evaluated by numerical simulations. The obtained results show that the spectral efficiency and BER performance of the IMC-DCSK system are enhanced in the comparison to those of the MC-DCSK system.