Faculty Publications
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Item Multiuser Data Transmission Aided by Simultaneous Transmit and Reflect Reconfigurable Intelligent Surface in Underwater Wireless Optical Communications(Institute of Electrical and Electronics Engineers Inc., 2024) Naik, R.P.; Salman, M.; Bolboli, J.; Savidhan Shetty, C.S.; Chung, W.-Y.Recent research in the wireless communications field has focused on the reconfigurable intelligent surface (RIS), which can enhance energy and spectrum efficiency by reconfiguring radio waves to propagate in a specific direction. In this study, we applied the simultaneous transmit and reflect (STAR)-RIS to an underwater wireless optical communication (UWOC) system. In contrast to a conventional RIS, a STAR-RIS allows multiple users to transfer data simultaneously in all directions by obtaining a UWOC channel despite underwater turbulence, beam attenuation, blockage, and pointing errors. Underwater turbulence-induced fading was obtained by using exponential and generalized Gamma distributions, and numerical analysis were performed to evaluate the outage probability, bit error rate (BER), and channel capacity of a direct UWOC channel, conventional RIS assisted UWOC channel, and STAR-RIS assisted UWOC channel. The BER performance was also evaluated according to the number of reflective elements, type of modulation scheme, impact of pointing errors, blockage levels, and varying the transmit-reflection coefficient. Monte-Carlo simulations were performed to validate the analytical results for the BER and outage probability with respect to the average signal-to-noise ratio. Experiments were performed to demonstrate the received luminous intensity performance with respect to the incident beam luminous intensity of the proposed STAR-RIS assisted UWOC channel. © 1967-2012 IEEE.Item Outage probability analysis of vertical underwater wireless optical links under varying turbulence with pointing errors and attenuation losses(Optica Publishing Group (formerly OSA), 2025) Savidhan Shetty, C.S.; Badiger, M.; Prasad, D.In this paper, we investigate the outage probability performance of underwater wireless optical communication for a vertical link. Due to temperature and salinity variations, turbulence in the vertical link ranges from strong to weak. The vertical link turbulence is modeled using a cascade of the gamma–gamma and hyperbolic tangent log-normal distributions. In addition to turbulence, we consider the impact of attenuation losses in the underwater medium and pointing errors at the receiver for outage probability analysis. A closed-form expression for the outage probability of the vertical link is derived. Outage probability results are presented for different water types, signal-to-noise ratio thresholds, degrees of pointing errors, and data rates. Additionally, an asymptotic analysis is provided to offer insights at high transmitted power. The accuracy of the derived closed-form expression is validated using Monte Carlo simulations. © 2025 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.