STAR-RIS Assisted Ambient Backscatter Communication System With Index Modulation

Ambient Backscatter Communication System (ABCS) is regarded as one of the core technologies in the Internet of Things (IoT) due to its ultra-low power consumption and low-cost advantages. However, it also faces multiple challenges in terms of communication reliability, coverage range, and Spectral Efficiency (SE), which constrain its application potential in dense networks and complex scenarios. In this paper, we apply Simultaneous Transmitting and Reflecting Reconfigurable Intelligent Surface (STAR-RIS) with pattern technology and Index Modulation (IM) into ABCS to improve the SE and Bit Error Rate (BER) performance as well as coverage range. Specifically, the proposed scheme enables extra information bits to be transmitted by allocating subsurfaces to different Backscatter Tags (BTs) and leveraging antenna combinations formed by active antennas of BTs. Meanwhile, the integration of STAR-RIS into ABCS not only significantly enhances signal strength but also achieves full communication coverage. Furthermore, the theoretical and simulation analysis of BER for the proposed scheme is investigated, which reveals the reliability of this scheme with high SE and comparable BER performance.