Faculty Publications

Now showing 1 - 3 of 3

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).
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.
Performance Analysis of MIMO-EGC System for the Underwater Vertical Wireless Optical Communication Link
(Institute of Electrical and Electronics Engineers Inc., 2023) Savidhan Shetty, S.C.S.; Naik, R.P.; Shripathi Acharya, U.S.; Chung, W.-Y.
In this paper, we have investigated the performance of an underwater vertical wireless optical communication (UVWOC) link employing multiple input-multiple output (MIMO) operating in conjunction with equal gain combing (EGC) techniques perturbed by weak and strong turbulence in the presence of pointing errors and attenuation losses. Vertical underwater turbulence, which varies from layer to layer due to temperature and salinity variation connected to depth, is modeled using hyperbolic tangent log-normal (HTLN) distribution in the case of weak underwater turbulence and gamma-gamma (GG) distribution in the case of strong underwater turbulence. Novel closed-form expressions quantifying the average bit error rate (BER) have been derived for the UVWOC MIMO EGC system for weak and strong turbulence regimes. The expression for the average BER associated with the UVWOC link for different values of pointing error, differing vertical layer depth, modulation types, and differing numbers of sources and detectors have been determined. In addition, closed-form expressions for the outage probability (OP) and ergodic channel capacity (ECC) have been derived for the UVWOC MIMO EGC system. The accuracy of all closed-form expressions derived in the paper has been verified using Monte Carlo simulations. © 2013 IEEE.

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