A Hybrid DCSK Scheme Combining Cyclic Shift Keying and Code Index Modulation

In this letter, a hybrid differential chaos shift keying (DCSK) scheme combining cyclic shift keying and code index modulation (CSK-CIM-DCSK) is proposed to improve data rate and bit error rate (BER) performance. In the CSK-CIM-DCSK system, the bit stream is divided into blocks of
$m_{c} + m_{s} + 1$
bits, where the
$m_{c}$
bits are used for code index modulation and the
$m_{s}$
bits are used for cyclic shift keying modulation, and the last one bit is modulated by DCSK. The analytical BER expressions of the CSK-CIM-DCSK are derived over additive white Gaussian noise (AWGN) and multipath Rayleigh fading channels and validated via simulations. Simulation results indicate that the BER performance of the CSK-CIM-DCSK is significantly improved in contrast to DCSK with code index modulation (CIM-DCSK). Furthermore, the BER performance of the proposed system is compared with other non-coherent chaotic modulation systems, and the results show the superiority of the proposed system.