Security-Spectral Efficiency Tradeoff in STAR-RIS RSMA: A Max-Min Fairness Framework
This addresses security challenges in wireless communications for scenarios with full-space coverage, but it is incremental as it builds on existing STAR-RIS and RSMA frameworks.
The paper tackles the trade-off between spectral efficiency and security in STAR-RIS-assisted RSMA systems with internal and external eavesdroppers, developing an iterative algorithm that improves spectral efficiency while maintaining confidentiality.
Simultaneously transmitting and reflecting reconfigurable intelligent surfaces (STAR-RISs) enable full-space coverage but also expose wireless transmissions to security from multiple spatial directions. This paper investigates a STAR-RIS-assisted secure RSMA system where both internal and external eavesdroppers may coexist in the transmission and reflection regions. In such a scenario, the RSMA common stream simultaneously serves legitimate users, impairs external eavesdroppers, and avoids assisting internal eavesdroppers, leading to a challenging trade-off between spectral efficiency and confidentiality. To address this issue, we formulate a max-min fairness problem under secrecy constraints and develop an iterative algorithm to jointly optimize transmit beamforming and STAR-RIS phase shifts. Simulation results demonstrate that the proposed scheme improves spectral efficiency while maintaining confidentiality.