A Security-Enhanced Precoding Scheme for RIS-Assisted THz Communication Systems

Terahertz (THz) communication, a promising 6G candidate boasting ultra-wide bandwidth, confronts critical challenges including severe path loss and the inherent beam splitting effect in wideband scenarios. Reconfigurable intelligent surfaces (RIS) offer an effective means to dynamically manipulate wireless channels for performance enhancement. This letter proposes a novel RIS-assisted terahertz physical layer security (PLS) precoding scheme aimed at 6G ultra-high-speed secure communication requirements, providing a core solution to the security transmission challenges in THz broadband scenarios. The scheme precisely resolves the double beam splitting bottleneck caused by the coupling between RIS and THz broadband through beam focusing and shaping technology, achieving directional concentration of signal energy and leakage suppression from a spatial perspective; further innovatively, the artificial noise (AN) is projected into the channel null space of legitimate users, leveraging the ultra-wide bandwidth advantage of THz to construct a full-band interference barrier. In the end, the simulation results demonstrate the effectiveness of the proposed method.