The differential chaos shift keying with code index modulation (CIM-DCSK) using Walsh codes can increase the data rate, but error rate performance degrades over practical multipath channel with high delay spread. To tackle this drawback, this paper proposes a parallel CIM-DCSK (PT-CIM-DCSK), where the first time slot is used to transmit the chaotic reference sequence, and the second slot is used to transmit the multiple sequences carrying data bits. In particular, multiple $q$ chaotic sequences are added for data transmission in parallel, and each sequence is modulated by CIM-DCSK with $m_{c}$ bits. By exploiting the quasi-orthogonal characteristics of permuted chaotic signals, the interference between $q$ sequences can be remarkably suppressed. In this way, given the data rate, PT-CIM-DCSK can achieve a larger length of Walsh segment than the CIM-DCSK, since its parallel transmission compensates the rate. In addition, the error performance of the proposed scheme over the multipath Rayleigh fading channel is theoretically analyzed. The theoretical and consistent simulation results demonstrate that the PT-CIM-DCSK can obtain significant performance gains over the conventional CIM-DCSK, and the gain can be up to 5 dB in multipath fading channel with high delay. This is because the larger Walsh segment of PT-CIM-DCSK provides the enhanced robustness against multipath effect. The performance superiority of the proposed scheme is further verified in practical ultra-wideband (UWB) wireless industrial scenarios, which suggests promising for low-cost and low-complexity wireless communication applications.

中文翻译：

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用于无线通信的具有码索引调制的并行差分混沌移位键控

使用 Walsh 码的码索引调制差分混沌键控 (CIM-DCSK) 可以提高数据速率，但误码率性能在具有高延迟扩展的实际多径信道上会下降。针对这一缺陷，本文提出了一种并行CIM-DCSK（PT-CIM-DCSK），其中第一个时隙用于传输混沌参考序列，第二个时隙用于传输携带数据比特的多个序列。特别是多 $q$添加混沌序列用于并行数据传输，每个序列通过CIM-DCSK调制 $m_{c}$位。利用置换混沌信号的准正交特性， $q$序列可以被显着抑制。这样，在给定数据速率的情况下，PT-CIM-DCSK 可以实现比 CIM-DCSK 更大的 Walsh 段长度，因为它的并行传输补偿了速率。此外，从理论上分析了该方案在多径瑞利衰落信道上的误码性能。理论和一致的仿真结果表明，与传统的CIM-DCSK相比，PT-CIM-DCSK可以获得显着的性能增益，并且在具有高延迟的多径衰落信道中增益可以达到5 dB。这是因为 PT-CIM-DCSK 的较大 Walsh 段提供了针对多径效应的增强鲁棒性。在实际的超宽带（UWB）无线工业场景中进一步验证了所提方案的性能优越性，