  This paper proposes a high-throughput short reference differential chaos
shift keying cooperative communication system with the aid of code index
modulation, referred to as CIM-SR-DCSK-CC system. In the proposed
CIM-SR-DCSK-CC system, the source transmits information bits to both the relay
and destination in the first time slot, while the relay not only forwards the
source information bits but also sends new information bits to the destination
in the second time slot. To be specific, the relay employs an $N$-order Walsh
code to carry additional ${{\log }_{2}}N$ information bits, which are
superimposed onto the SR-DCSK signal carrying the decoded source information
bits. Subsequently, the superimposed signal carrying both the source and relay
information bits is transmitted to the destination. Moreover, the theoretical
bit error rate (BER) expressions of the proposed CIM-SR-DCSK-CC system are
derived over additive white Gaussian noise (AWGN) and multipath Rayleigh fading
channels. Compared with the conventional DCSK-CC system and SR-DCSK-CC system,
the proposed CIM-SR-DCSK-CC system can significantly improve the throughput
without deteriorating any BER performance. As a consequence, the proposed
system is very promising for the applications of the 6G-enabled low-power and
high-rate communication.
