Faculty Publications

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Author: search.filters.author.Krishnan, K.Subject: search.filters.subject.Bit error rate

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    Asymptotic bit-error rate analysis of quadrature amplitude modulation and phaseshift keying with OFDM RoFSO over M turbulence in the presence of pointing errors
    (Institution of Engineering and Technology journals@theiet.org, 2018) Krishnan, K.; Jana, U.; Kumar, B.K.
    In case where installation of optical fibre is not practically reliable, the new generation wireless communication popularised as free-space optics (FSO) systems can be used to transmit radio-frequency (RF) signals. FSO technology can efficiently transfer multiple RF signals, and this new technique is commonly referred as radio-on-FSO (RoFSO). The major challenges in this technology are atmospheric turbulence and pointing errors. In this study, the authors analysed the performance of RoFSO links employing the orthogonal frequency division multiplexing (OFDM) scheme under both modulation formats namely quadrature amplitude modulation and phase shift keying in the newly developed Málaga or M distribution turbulent channel model. The performance is evaluated with consideration of both scintillation and pointing errors in M distribution channel for higher values of the carrier-to-noise plus distortion ratio. M distribution channel serves as an effective generalised model which unifies all other available statistical channel models. The novel expressions of average bit-error rate has been derived and performance comparison has been done between the two modulation formats. This study identifies the crucial parameters that deteriorate the efficiency of the OFDM signal over FSO link which can be helpful in designing an optimal system. © The Institution of Engineering and Technology 2018.
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    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.