Integration of STAR-RIS With Index Modulation: Novel Attraction Solutions for IoT Applications

The integration of the sixth-generation (6G) communication technology with the Internet of Things (IoT) is one of the directions in achieving a digitalized world, aiming to provide ultrahigh-speed communication services that exhibit higher energy-efficiency, lower latency, and heightened reliability and availability. In this article, we investigate the use of the simultaneous transmitting and reflecting reconfigurable intelligent surface (STAR-RIS), one of the candidate technologies for 6G communication, along with the index modulation (IM) in multiantennas ambient backscatter communication system (ABCS) to form the STAR-RIS-assisted ABCS with spatial modulation (STAR-RIS-ABCS-SM). In particular, through the utilization of STAR-RIS and backscatter communication, we meet the demand for low-power wireless communication devices in the green communication, which is also a crucial characteristic of the IoT. Specifically, we introduce STAR-RIS into ABCS, which not only significantly boost the signal strength but also achieve full communication coverage. Meanwhile, we apply the spatial modulation (SM) technology in the multiantennas backscatter tags (BTs), located on both sides of the STAR-RIS, and use joint detection at the reader to enhance the system’s spectral efficiency (SE) as well as its bit error rate (BER) performance. Furthermore, we divide the STAR-RIS into various subsurfaces to form patterns that further enhance SE, which is termed STAR-RIS-assisted ABCS with pattern index and SM (STAR-RIS-ABCS-PISM) scheme. Finally, theoretical BER analytical expressions for both schemes are derived and presented. Simulation and theoretical results demonstrate the enhanced performance of the proposed schemes as well as the validity of the system model.