Cross reference carrier index differential chaos shift keying communication with chaotic shape-forming filter

To improve the bit error rate (BER) performance and enhance the data transmission rate of the differential chaos shift keying (DCSK) system, a new cross reference carrier index (CR-CI) DCSK modulation scheme using the chaotic shape-forming filter (CSF) referred to as CR-CI-CSF-DCSK, is proposed in this paper. In the proposed scheme, the subcarriers are divided into two groups and indexed, respectively, the first group of index bits are used to select carrier for the modulated bit transmission, and the second group is for carrier selection of the reference signal, which is the same as that in the CR-CI-DCSK system. The high-priority (HP) data consists of both the index bits and the modulated bit, which are transmitted together during each symbol period. Different from the traditional reference signal generated by the logistic map, the chaotic signal generated by the CSF is used as the reference signal in this work, which can encode additional data information referred to as the low-priority (LP) data. At the receiver of the CR-CI-CSF-DCSK system, the HP data bits recovery is performed according to the correlation between the reference signal and the information-bearing signal, at the same time, the LP data bits are decoded by the zero threshold for simplicity after the correlation operation. Numerous simulations about the proposed CR-CI-CSF-DCSK system under the addition white Gaussian noise (AWGN) channel and the multipath Rayleigh fading channel are performed, the simulation results demonstrate the superiority and effectiveness of the proposed scheme in the sense of the BER performance. In particular, the BER performance of the LP data bits in the proposed CR-CI-CSF-DCSK is also improved as compared to that of the MC-CSF-DCSK scheme, because more energy is allocated to the reference signal by activating only one subcarrier for the information-bearing signal transmission in one symbol period. Moreover, the efficiency of the proposed CR-CI-CSF-DCSK system is analyzed, and the comparison results show that the energy efficiency is improved significantly as compared to several other relevant modulation schemes.