Multi-carrier differential chaos-shift keying with repeated spreading sequence

This paper proposes a multi-carrier differential chaos-shift keying (MC-DCSK) system using repeated spreading sequence (RSS), namely RSS-MC-DCSK, for chaos-based wireless communications. In the proposed system, instead of transmitting the chaotic spreading sequence on a predefined subcarrier as in conventional MC-DCSK, a DCSK-modulated signal, of which each two-bit duration consisting of reference and data-bearing sequences is sent via this subcarrier. Meanwhile, a repeated spreading sequence is produced by copying the reference sequence of the DCSK-modulated signal to the same and next bit periods. The parallel bit streams are multiplied with this RSS and the resulting signals are then conveyed by corresponding subcarriers. In the receiver, the signal retrieved from the predefined subcarrier is DCSK-demodulated and simultaneously used to recover the repeated spreading sequence. The correlative demodulation is performed for all the signals retrieved from the remaining subcarriers to decode the data. The structure and operation of the proposed system are described. Bit error rate (BER) performance under a multipath Rayleigh fading channel is theoretically analyzed and then verified by numerical simulations. In addition, the BER performance, energy and spectral efficiencies of RSS-MC-DCSK are evaluated in comparison to those of MC-DCSK.