Purpose Secure transmission in wireless communication systems has garnered significant attention recently. A key challenge is thwarting eavesdroppers while optimizing the performance of legitimate users and security. This paper aims to propose a novel scheme using index modulation (IM) for a space-time block code (STBC)-aided simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) system to ensure physical layer security (PLS). Design/methodology/approach STAR-RIS is designed as an access point (AP) to adjust array element phases for signal generation. By grouping the STAR-RIS and using IM, different antenna combinations are activated for transmission. The zero-forcing (ZF) precoding method generates artificial noise (AN) based on the channel state information (CSI) of the legitimate user, which is then added to the transmitted signals. Finally, Alamouti coding is integrated into the STAR-RIS for signal transmission. Findings Theoretical and simulation analyses of bit error rate (BER) and secrecy rate show the scheme prevents eavesdropping and enhances the secrecy rate. At a 30dB signal-to-noise ratio (SNR), the secrecy rate increases by approximately 8 bits/s/Hz compared to the no-AN scheme. Furthermore, compared to traditional STAR-RIS, at BER = 10−4, the SNR gain is approximately 2dB. Research limitations/implications The good results are based on CSI in the communication system. Practical implications It could be used for V2V communication networking and secured communications. Social implications It gives more ideas and research on the coding in the RIS. Originality/value Designing STAR-RIS as an AP simplifies channel links and, combined with Alamouti code, greatly boosts diversity gain via spatial-temporal coding. Moreover, this paper uses the STAR-RIS to implement IM, enabling the additional transmission of index bits and improving spectral efficiency. Meanwhile, adding AN to signals, a key design aspect, prevents eavesdropping and enhances security, showing a holistic approach to optimizing wireless security.
Han et al. (Fri,) studied this question.