Channel Estimation, Resource Optimization, and Experimental Validation of Multi STAR-RIS Aided UOWC System

This paper proposes an underwater optical wireless communication (UOWC) system to facilitate the data broadcasting in optical domain and allows distant users to receive data. Such benefits have been demonstrated by deploying multiple simultaneously transmitting and reflecting reconfigurable intel ligent surface (STAR-RIS), where the STAR-RISs can transmit and reflect data simultaneously in two modes of operation- energy splitting (ES) and time switching (TS). In this paper, the bit error rate (BER) performance of such a system has been evaluated experimentally as well as analytically. The phase shifts of all the optical STAR-RISs are intricately coupled, for which evolutionary algorithms such as particle swarm optimization (PSO) and differential evolution (DE) have been utilized to optimize the sum-rate of all users. For optimization, estimation of channel coefficients is necessary, which is solved using artificial neural network. The aforementioned experimental setup demonstrated that the proposed system can serve the farthest user, which cannot be served directly. The proposed method can yield around 13dBof transmit power gain over a single optical STAR-RIS system