Quadrature multi-carrier DCSK: A high-efficiency scheme for radio communications

摘要

This paper proposes an enhanced version of multicarrier differential chaos-shift keying (MC-DCSK) scheme using quadrature modulation (QM), namely QMC-DCSK. In the proposed scheme, the chaotic spreading sequence is transmitted on a predefined frequency the same as in the conventional MC-DCSK, while each of the remaining frequencies is phase-shifted an 90° angle in order to produce two quadrature sub-carriers located at the same frequency. These subcarriers are modulated by the data-bearing sequences which are the product of the chaotic spreading sequence and the corresponding bit sub-streams in parallel. The use of quadrature modulation aims at doubling the data rate for a defined bandwidth and hence improve the bandwidth efficiency of the system. In the receiver, the chaotic sequence retrieved from the predefined frequency is correlated with the data-bearing sequences retrieved from the subcarriers. The bit sub-streams are recovered based on the sign of the correlation values. The structure and operation of the conventional and proposed schemes are described. The BER performance over a typical model of radio channel is theoretically analyzed and then verified by numerical simulations. The improvement in terms of bit rate, energy and bandwidth efficiencies of QMC-DCSK is evaluated in the comparison to those of MC-DCSK.