Physical Layer Authentication in Distributed RIS-Enabled VLC Systems for Mobile Users

This work proposes a physical layer authentication framework for Distributed Reconfigurable Intelligent Surface (DRIS)-enabled Visible Light Communication (VLC) systems, specifically designed to address both stationary and mobile users in dynamic environments. DRIS plays a crucial role in adapting the communication channel to enhance authentication accuracy. The legitimate transmitter employs a time-slotted communication strategy to transmit a predefined set of authentication challenges to the receiver. While an adversary may attempt to replicate some of these challenges, the probability of correctly guessing all of them remains extremely low. To address the challenges posed by user mobility and the resulting variations in channel response characteristics, the proposed framework leverages known channel properties from predefined locations and approximates unknown conditions using two possible approaches: the nearest-channel method and a weighted averaging method that incorporates multiple nearby recorded channel responses. Both approaches aim to compensate for rapid channel fluctuations, ensuring more reliable authentication for mobile users. Since VLC channels are inherently vulnerable to impersonation attacks, authentication strategies must be capable of distinguishing legitimate users from adversaries under varying mobility conditions. To evaluate the effectiveness of the proposed approach, a simulation framework was developed to model user trajectories, dynamic channel variations, and blockage conditions. The study considers 20 different user movement cases within a predefined environment, where authentication performance is analyzed using Monte Carlo simulations. Results indicate that while stationary users achieve superior authentication performance due to stable channel conditions, mobile users can still maintain reasonable PFA and PMD with the proposed weighted approach. However, when the new user location is significantly distant from predefined channel responses, authentication performance deteriorates, leading to a noticeable increase in both false alarms and missed detections. The simulation results validate the proposed framework’s ability to enhance security in DRIS-enabled VLC systems across both stationary and mobile contexts.