To improve the data rate in differential chaos shift keying (DCSK) based ambient backscatter communication (AmBC) system, we propose a new AmBC system based on code index modulation (CIM), referred to as CIM-DCSK-AmBC system. In the proposed system, the CIM-DCSK signal transmitted in the direct link is used as the radio frequency source of the backscatter link. The signal format in the backscatter link is designed to increase the data rate as well as eliminate the interference of the direct link signal. As such, the direct link signal and the backscatter link signal can be received and demodulated simultaneously. Moreover, we derive and validate the theoretical bit error rate (BER) expressions of the CIM-DCSK-AmBC system over multipath Rayleigh fading channels. Regarding the short reference DCSK-based AmBC (SR-DCSK-AmBC) system as a benchmark system, numerical results reveal that the CIM-DCSK-AmBC system can achieve better BER performance in the direct link and higher throughput in the backscatter link than the benchmark system.

翻译：为了提升基于差分混沌键控（DCSK）的环境反向散射通信（AmBC）系统的数据传输速率，我们提出了一种基于码索引调制（CIM）的新型AmBC系统，称为CIM-DCSK-AmBC系统。在该系统中，直传链路发送的CIM-DCSK信号被用作反向散射链路的射频源。反向散射链路的信号格式经过设计，既能提高数据速率，又能消除直传链路信号的干扰。由此，直传链路信号和反向散射链路信号可同时接收与解调。此外，我们推导并验证了CIM-DCSK-AmBC系统在多径瑞利衰落信道下的理论误码率（BER）表达式。以基于短参考DCSK的AmBC（SR-DCSK-AmBC）系统为基准系统，数值结果表明，CIM-DCSK-AmBC系统在直传链路上可获得更优的BER性能，在反向散射链路上可实现比基准系统更高的吞吐量。