Faculty Publications
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Item Analysis of M-QAM Modulated Underwater Wireless Optical Communication System for Reconfigurable UOWSNs Employed in River Meets Ocean Scenario(Institute of Electrical and Electronics Engineers Inc., 2020) Uppalapati, A.; Naik, R.P.; Krishnan, K.In this paper, the bit error rate (BER) performance of underwater wireless optical communication system employing with M-ary quadrature amplitude modulation is proposed for underwater optical wireless sensor networks (UOWSN) in river meets ocean scenario. The underwater channel degradation effects such as absorption, scattering and oceanic turbulence is taken into account. The oceanic turbulence is modelled by the Gamma-Gamma distribution. The first time, we proposed re-configurable UOWSN for the real time scenario of the river meets the ocean and derived the novel closed form analytical BER expressions of the proposed system over Gamma-Gamma turbulence with attenuation effects. The impact of oceanic turbulence parameters such as the variations of temperature, kinetic energy, viscosity, salinity, link range and the water type of system performance is investigated for river water, mixed water (river and ocean water) and ocean water. The proposed system and the related analysis will be highly useful in UOWSN and the Internet of underwater thing (IoUT) applications. © 1967-2012 IEEE.Item Performance enhancement using multiple input multiple output in dual-hop convergent underwater wireless optical communication-free-space optical communication system under strong turbulence with pointing errors(SPIE, 2021) Bhargava Kumar, B.K.; Naik, R.P.; Krishnan, P.For the first time, we propose a dual-hop multiple input multiple output (MIMO)-based convergent underwater wireless optical communication (UWOC)-free-space optical (FSO) system. The UWOC and FSO links are Gamma-Gamma (GG) distributed. Closed-form expression for the average bit error rate (ABER) is derived for the proposed MIMO-based dual-hop UWOC-FSO convergent system using the GG cumulative distribution function. The end-to-end system performance analysis is carried out by considering the turbulence, attenuation, and pointing error effects for UWOC and FSO links. For the UWOC link, different oceanic conditions, such as the clear ocean, coastal ocean, and turbid harbor, are considered. Various atmospheric effects, such as clear air, fog, rain, drizzle, and haze, are considered for the FSO link. The analytical results of the proposed MIMO-based convergent system are compared with single-input single-output (SISO) system. As a result, it is observed that the proposed MIMO 2 × 3 scheme offers an improvement of 35 dB in the average signal-to-noise ratio compared with the SISO system at ABER of 10-5 in the case of weak pointing error. © 2021 Society of Photo-Optical Instrumentation Engineers (SPIE).Item Wireless-optical-communication-based cooperative IoT and IoUT system for ocean monitoring applications(The Optical Society, 2021) Naik, R.P.; G.D., G.D.G.; Krishnan, P.This paper proposes the idea of a new cooperative communication between the Internet of Things (IoT) and the Internet of Underwater Things (IoUT) using wireless optical connectivity for ocean monitoring applications.We considered IoT communication using a hybrid radio frequency (RF)/free space optical (FSO) link and IoUT using a underwater wireless optical communication (UWOC) link. Channel models for RF, FSO, and UWOC links are considered to be Rayleigh,Malaga with pointing errors, and hyperbolic tangent log-normal distributions, respectively. The outage probability and the bit error rate (BER) expressions for the proposed system are derived over the combined channel model, which includes the effects of attenuation, turbulence, and pointing errors. The BER results are plotted for various binary digital modulation schemes such as on-off keying, binary phase-shift keying, binary frequency-shift keying, and differential phase-shift keying over UWOC, hybrid RF/FSO and RF-UWOC, FSO-UWOCwith end-to-end systems.BERresults are extended for various turbulence regions and pointing errors of theFSOlink.MonteCarlo simulation results authenticate the correctness of the results. © 2021 Optical Society of America.Item RIS Assisted Triple-Hop RF-FSO Convergent With UWOC System(Institute of Electrical and Electronics Engineers Inc., 2022) Bhargava Kumar, L.B.; Naik, R.P.; Krishnan, P.; Raj, A.A.B.; Majumdar, A.K.; Chung, W.-Y.The convergence of wireless optical communication (WOC) and radio-frequency (RF) systems is a promising technology that overcomes the shortcomings of standalone communication systems. By incorporating reconfigurable intelligent surfaces (RISs) on top of these WOC and RF communication systems, it is possible to circumvent the connection challenges associated with standard line of sight (LOS) communication links. Wireless communication systems with RIS assistance are a promising and evolving technology that enables more efficient and reliable link performance over long distances. The performance of the triple-hop RIS-assisted RF-FSO convergent with the underwater wireless optical communication (UWOC) system is investigated in this article. We considered the fading channel Nakagami-m over the RIS-RF connection and the fading channel Gamma-Gamma (GG) over the RIS-FSO and UWOC links. Then, the average bit error rate (ABER) and outage probability are determined using closed-form expressions. The ABER and outage probability performances of the triple-hop communication system is analysed by varying parameters such as turbulence, misalignment fading, and the number of RIS elements. The obtained results demonstrate an improvement in performance for low turbulence, low pointing error, and an increasing number of RIS elements. Additionally, the data demonstrate the accuracy of the analytical results. © 2013 IEEE.Item Underwater wireless optical communications based reconfigurable UOWSN for monitoring and discovering continental margin ore deposits(Optica Publishing Group (formerly OSA), 2022) Bhargava Kumar, B.K.; Naik, R.P.; Krishnan, P.; Majumdar, A.K.Changes in the environment, such as landslides, tsunamis, rising or falling sea levels in coastal oceans, and neighboring land surfaces, significantly impact the structure of the ocean and human life. These natural climate-change processes have unanticipated and deadly consequences for coastal areas. The continental margin part of the ocean has recently attracted the most attention because of the mineral sources and human activities such as exploration, navigation, recreation, and fishing. The continental margin stretches fromthe coastal mountains and plains to continental shelf, slope, and rise, where terrestrial and maritime means meet. In this paper, we propose a reconfigurable underwater optical wireless sensor network (UOWSN) based on underwater wireless optical communication (UWOC) to monitor and discover continental margin ore deposits. In this proposed system, a transceiver on the underwater wireless autonomous vehicle moving around the different regions of the continental margin collects information and transmits it to the seashore control station once it reaches the ocean surface. We investigated the outage probability and average bit error rate of the proposed system at the continental margin and used coding techniques to mitigate the effects of high turbulence in the continental shelf region. © 2022 Optica Publishing Group.Item Performance analysis of multi-hop FSO convergent with UWOC system for security and tracking in navy applications(Springer, 2022) Bhargava Kumar, B.K.; Naik, R.P.; Krishnan, P.The Navy is ubiquitous in every major geographic area of the world. It is estimated that 60% of global goods are transported by sea. The Navy plays a vital role in offering protection of the sea lanes and the trade transportation, preserves territorial ocean borders and the right to the resources contained in them, and facilitates the response to natural disasters and other disasters. In this paper, we proposed for the first time a multi-hop free-space optical (FSO)—underwater wireless optical communication (UWOC) converging system. It is useful for the secure transport and tracking of goods and missiles through cargo ships for the navy and marine applications. The end-to-end average bit error rate (ABER) and outage probability performance of multi-hop FSO transmission systems converged with UWOC is analysed. The outage and ABER expression of the proposed system was obtained and the results were plotted for different weather conditions, turbulence regimes, pointing error and number of FSO hop scenarios. A case study is done on the extent to which the speed and height of the ship, the wind speed and the links between the ships affect the end-to-end outage performance of the proposed triple hop FSO converging UWOC system. This study is performed in Surathkal, which is located 20 km north of Mangalore. We assumed in this case study that the ships are located near surathkal in the Arabian Sea (GPS coordinates: N 13∘0′38.0988′, E 74∘47′17.4876′), Karnataka, India. Computational complexity of proposed cumulative distribution functions (CDF) have been evaluated with the existing CDF in the literature. In addition to that the expected cost analysis of the proposed communication system provided. © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.Item High-speed long-range multihop underwater wireless optical communication convergent with free-space optical system for optical internet of underwater things and underwater optical wireless sensor network applications(SPIE, 2022) Bhargava Kumar, B.K.; Naik, R.P.; Krishnan, P.We propose a multihop underwater wireless optical communication (UWOC) convergent with free-space optical (FSO) system for an optical internet of underwater things (O-IoUT) and underwater optical wireless sensor network (UOWSN) applications. A closed-form expression of outage probability was derived for the proposed system using the cumulative distribution functions gamma-gamma and hypertangent log-normal for FSO link and UWOC link, respectively. The outage performance of the proposed multihop UWOC convergent with FSO system was analyzed over various oceanic water types (clear ocean, coastal ocean, and turbid harbor) and different FSO weather conditions (clear air, haze, drizzle, and light fog). The results also depict the end-to-end system performance for different pointing errors (strong, moderate, and weak) and varying the number of hops. The maximum link range of ∼2.5 km, which includes 2 km of FSO link and 450 m of multihop UWOC link (nine hops with each of 50 m clear ocean), is considered. © 2022 Society of Photo-Optical Instrumentation Engineers (SPIE).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.