Hybrid reconfigurable intelligent surface-enabled enhanced reflection modulation

Abstract

This paper presents a novel index modulation (IM) technique named hybrid reconfigurable intelligent surface (RIS) enabled enhanced reflection modulation (Hyb-ERM), which capitalizes on the hybrid RIS architecture comprising both active and passive elements. In Hyb-ERM, a hybrid RIS is partitioned into groups, with information bits transmitted through both conventional M-ary phase shift keying (PSK) modulated symbols and the number of active RIS groups. This approach, particularly the manipulation of transmitted symbols by the hybrid RIS based on the number of active groups, is designed to improve the minimum Euclidean distance, thereby significantly enhancing error performance. We have derived a theoretical upper bound for the bit error probability (BEP) and proposed two low-complexity detectors as alternatives to the maximum likelihood (ML) detector. Extensive simulation results validate the effectiveness of Hyb-ERM, showing its superior error performance compared to benchmark schemes under both ideal and non-ideal channel conditions. This study underscores the potential of Hyb-ERM in advancing RIS-assisted communications, paving the way for more efficient and robust 6G wireless networks.