Sensing-Assisted Physical Layer Security for Near-Field Terahertz Systems With Beam Squint

In this paper, we investigate the sensing-assisted physical layer security (PLS) in the near-field THz systems. It is well known that the application of PLS requires the channel state information (CSI) of the eavesdropping user. On this basis, we first propose a sensing scheme based on the controllable beam squint to obtain the CSI, and the cooperation of multiple RF chains is considered to avoid the large time overhead of traditional beam training. After that, we design a nearfield beamforming scheme based on two-dimensional search to maximize the secrecy rate by adjusting the beamsquint trajectory. Finally, simulation results demonstrate the effectiveness of the proposed schemes.