Reconfigurable intelligent surface (RIS)-assisted transmission and space shift keying (SSK) appear as promising candidates for future energy-efficient wireless systems. In this article, two RIS-based SSK schemes are proposed to efficiently improve the error and throughput performance of conventional SSK systems, respectively. The first one, termed RIS-SSK with passive beamforming (RIS-SSK-PB), employs an RIS for beamforming and targets the maximization of the minimum squared Euclidean distance between any two decision points. The second one, termed RIS-SSK with Alamouti space-time block coding (RIS-SSK-ASTBC), employs an RIS for ASTBC and enables the RIS to transmit its own Alamouti-coded information while reflecting the incident SSK signals to the destination. A low-complexity beamformer and an efficient maximum-likelihood (ML) detector are designed for RIS-SSK-PB and RIS-SSK-ASTBC, respectively. Approximate expressions for the average bit error probabilities of the source and/or the RIS are derived in closed-form assuming ML detection. Extensive computer simulations are conducted to verify the performance analysis. Results show that RIS-SSK-PB significantly outperforms the existing RIS-free and RIS-based SSK schemes, and RIS-SSK-ASTBC enables highly reliable transmission with throughput improvement.

中文翻译：

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具有可重新配置的智能表面的空间移位键控：相配置设计和性能分析

可重构智能表面（RIS）辅助的传输和空间移位键控（SSK）似乎是未来节能无线系统的有希望的候选者。在本文中，提出了两种基于RIS的SSK方案，分别有效地改善了常规SSK系统的错误和吞吐量性能。第一个称为无源波束成形的RIS-SSK（RIS-SSK-PB），采用RIS进行波束成形，并以任意两个决策点之间的最小平方欧几里德距离为目标。第二种称为带有Alamouti时空块编码的RIS-SSK（RIS-SSK-ASTBC），它为ASTBC使用RIS，并使RIS能够传输自己的Alamouti编码信息，同时将入射的SSK信号反射到目的地。低复杂度波束形成器和高效的最大似然（ML）检测器分别设计用于RIS-SSK-PB和RIS-SSK-ASTBC。源和/或RIS的平均误码率的近似表达式是在假设ML检测的情况下以封闭形式得出的。进行了广泛的计算机仿真，以验证性能分析。结果表明，RIS-SSK-PB明显优于现有的无RIS和基于RIS的SSK方案，而RIS-SSK-ASTBC可实现高可靠传输并提高了吞吐量。