Reconfigurable intelligent surface (RIS) has recently emerged as a promising technology enabling next-generation wireless networks. In this letter, we develop an improved index modulation (IM) scheme by utilizing RIS to convey information. Specifically, we study an RIS-aided multiple-input single-output (MISO) system, in which the information bits are conveyed by reflection patterns of RIS rather than the conventional amplitude-phase constellation. Furthermore, the K-means algorithm is employed to optimize the reflection constellation to improve the error performance. Also, we propose a generalized Gray coding method for mapping information bits to an appropriate reflection constellation and analytically evaluate the error performance of the proposed scheme by deriving a tight upper bound of the average bit error rate (BER). Finally, numerical results verify the accuracy of our theoretical analysis as well as the substantially improved BER performance of the proposed RIS-based IM transmission scheme.

翻译：可重构智能表面（RIS）作为一项有望实现下一代无线网络的新兴技术近期备受关注。本文利用RIS传递信息，提出了一种改进的索引调制（IM）方案。具体而言，我们研究了一个RIS辅助的多输入单输出（MISO）系统，其中信息比特通过RIS的反射模式而非传统的幅度-相位星座进行传递。进一步地，采用K-means算法优化反射星座以提升误码性能。同时，我们提出了一种通用格雷编码方法，用于将信息比特映射至适当的反射星座，并通过推导平均误比特率（BER）的紧致上界，对所提方案的误码性能进行了理论分析。最后，数值结果验证了理论分析的准确性，以及所提基于RIS的IM传输方案在BER性能上的显著改善。