Secrecy Sum-Rate Maximization and Symbol Detection for OSTAR-RIS Assisted VLC System

Visible light communication (VLC) is an energy-efficient, green, and low-cost technology for high-speed next-generation communication systems. However, it has been observed that the performance of a VLC-based system is limited due to the light-emitting diode's (LED) nonlinear characteristics, low coverage area, and loss of the VLC signal due to the absence of a direct link between the transmitter and receiver caused by blockages present in the environment. In addition, the secrecy sum rate (SSR) of a VLC system is compromised due to the presence of an eavesdropper. To address the problem of dead zones and low coverage area, an optical simultaneously transmitting and reflecting intelligent surface (OSTAR-RIS) is proposed in the literature. For SSR maximization, the particle swarm optimization (PSO) method is employed and compared with the benchmark exhaustive search method. For implicit channel estimation and direct symbol detection, an LSTM-based algorithm for a nonlinear OSTAR-RIS VLC system is proposed. Simulations indicate superiority of the proposed optimization and implicit channel estimation technique over benchmark schemes.