RIS-Aided Protected Zone Formation for Physical Layer Security of In-Band Full Duplex Systems

The rapid evolution of mobile technologies presents a formidable security challenge, as traditional cryptographic methods struggle to keep pace. Integrating physical layer security (PLS) solutions with cutting-edge technologies such as in-band full-duplex (IBFD) and reconfigurable intelligent surfaces (RISs) holds promise for addressing these challenges effectively. This study introduces a novel RIS-driven protected zone (PZ) formation approach that employs artificial noise (AN) to safeguard legitimate users without requiring <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a priori</i> knowledge of eavesdropper locations, channels, or numbers. The proposed methodology partitions the RIS into two distinct segments: while the former segment enhances the achievable data rate for legitimate signal, the latter segment concurrently amplifies AN to jam illegitimate users within the PZ.We present formulations and solutions for maximizing secrecy capacity (SC) and minimizing power consumption through optimized transmit power allocation factors, RIS segmentation, and beams’ directions, all subject to stringent quality-of-service (QoS) constraints. Closed-form expressions are derived to facilitate efficient implementation and performance optimization. Simulation results validate closed-form solutions and demonstrate that the proposed scheme can significantly enhance SC compared to benchmarks where RIS and AN are used separately, with the proposed scheme achieving approximately 81% greater capacity than the “RIS-Only” approach and a substantial advantage over the “AN-Only” approach, which results in no secrecy. Additionally, this work includes an analysis of energy efficiency, emphasizing the critical importance of optimizing power consumption in practical applications. This dual focus on improving security while effectively managing energy resources underscores the scheme’s practical relevance and efficiency.