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Author: search.filters.author.Shripathi Acharya, U.S.Subject: search.filters.subject.Underwater optical wireless communication

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    Performance investigation of underwater wireless optical system for image transmission through the oceanic turbulent optical medium
    (Springer, 2022) Naik, R.P.; Shripathi Acharya, U.S.; Lal, S.; Krishnan, P.
    The importance of resources contained in the sea and on the sea floor is increasing with each passing day. Hence, exploration of the sea and sea floor has become a very important requirement. Underwater imaging is a science that has gained importance over the past two decades. Underwater images indicate the state of sea floor and transmitting such images through the harsh and turbulent oceanic medium can cause deterioration of the information contained in the image due to diminished color reproduction, low contrast and blur. In this paper, we have performed the simulation studies to understand perturbations induced during the transmission of sea floor images using high-speed optical signaling through the underwater channels. The transmitted irradiance often suffers from underwater turbulence and beam attenuation. The bit error rate (BER) of the system proposed to transmit information through channels has been determined through analytic means and validated through Monte-Carlo simulation. Comparison between the transmitted and received images in the presence of turbulence and attenuation have been presented. The BER performance of the proposed system is evaluated in the presence of beam attenuation and underwater turbulence. The turbulence induced errors are minimized using the transmit/receive diversity and multiple input multiple output (MIMO) techniques. In addition to the diversity techniques, median and adaptive median filters used to minimize the distortion in the received image. The BER results show that the 4 × 5 MIMO system gains 19.50 dB of transmit power at BER of 10 - 5, when compared with the single input single output system. Similarly, an improvement of at-least 18 dB peak signal to noise ratio obtain using the adaptive median filter based system over the un-filter based system. © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
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    Performance analysis of underwater vertical wireless optical communication links using selection combining
    (Optica Publishing Group (formerly OSA), 2023) Savidhan Shetty, S.C.S.; Naik, R.P.; Shripathi Acharya, U.S.
    In this paper, we have investigated the performance of underwater vertical wireless optical communication (UVWOC) links employing on–off key modulation for selection combining based receive diversity schemes in the presence of underwater turbulence, pointing errors, and attenuation losses. Due to variations in temperature and salinity along the ocean’s depth, turbulence-induced fading affects the performance of the underwater vertical wireless optical link. The vertical link of the underwater medium influenced by a strong turbulence regime is modeled using cascaded gamma–gamma distribution considering multiple non-identical layers along with attenuation losses and pointing errors. We have derived closed-form expressions for the average bit error rate (BER) and outage probability (OP) for the link employing multiple detectors at the receiving end. The accuracy of all of the closed-form expressions derived in this paper has been validated using Monte Carlo simulations. © 2023 Optica Publishing Group.
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    Performance Analysis of Dual-Hop AF/DF Relay Utilizing BCH Code in an Underwater Vertical Wireless Optical Link
    (Institute of Electrical and Electronics Engineers Inc., 2024) Savidhan Shetty, C.S.; Achala, G.; Prasad Naik, R.; Shripathi Acharya, U.S.; Chung, W.-Y.
    Many attempts have been made to realize effective communication from the sea surface to ocean depths. One promising emerging technology is the deployment of underwater vertical wireless optical links to establish reliable and high-speed communication. In this study, we have attempted to evaluate the performance of an underwater vertical wireless optical communication (UVWOC) link operating beneath the ocean surface, utilizing amplify and forward (AF) as well as decode and forward (DF) relay systems. The investigation focuses on a vertical link traversing multiple layers of turbulence. The channel modeling of multiple layers under weak turbulence and strong turbulence conditions employs hyperbolic tangent log-normal and gamma-gamma distributions. Novel closed-form expressions are developed to quantify the average bit error rate and outage probability for dual-hop AF/DF relay UVWOC links in both weak and strong underwater turbulence conditions. The analysis accounts for attenuation losses and pointing errors. Monte-Carlo simulations validate the accuracy of the derived expressions. Furthermore, Bose-Chaudhuri-Hocquenghem (BCH) codes with parameters (n=31, k=11) and (n=63, k=18) are applied to enhance the integrity of information transfer over the AF/DF relay UVWOC link. This research contributes to understanding UVWOC links under diverse conditions and proposes coding techniques for improved reliability in challenging underwater environments. © 2013 IEEE.