K-Means Based Constellation Optimization for Index Modulated Reconfigurable Intelligent Surfaces

• Published in: IEEE communications letters Vol. 27; no. 8; pp. 2152 - 2156
• Main Authors: Liu, Hao, An, Jiancheng, Xu, Wangyang, Jia, Xing, Gan, Lu, Yuen, Chau
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.08.2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Algorithms; Bit error rate; constellation optimization; Downlink; Error analysis; index modulation; Indexes; K-means; MISO (control systems); MISO communication; Optimization; Performance evaluation; Reconfigurable intelligent surface (RIS); Reconfigurable intelligent surfaces; Reflection; Symbols; Upper bounds; Wireless networks
• ISSN: 1089-7798; 1558-2558
• DOI: 10.1109/LCOMM.2023.3282321

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.