Faculty Publications

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Publications by NITK Faculty

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Subject: search.filters.subject.Free Space Optical communication

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Now showing 1 - 7 of 7
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    Performance analysis of FSO based inter-UAV communication systems
    (Springer, 2021) Nallagonda, V.R.; Krishnan, P.
    Recently unmanned aerial vehicles (UAVs) gained considerable attention for recent potential applications like 6G, internet of things, disaster management applications etc. Especially inter UAV communications have an increased interest in low, medium, and high altitude platforms. Free space optical (FSO) communication plays a vital role in UAV communication to offer a high data rate, wider bandwidth, and secure transmission. In this paper, first time we introduced heterodyne detection (HD) in FSO based inter UAV communication. The outage and average bit error rate (BER) performance of the proposed system is analyzed and the results are compared with the existing Intensity modulation direct detection (IM/DD). We studied the impact of turbulence and pointing errors on BER and outage performance of the proposed system. The results are plotted for different system parameters such as Rytov Variance, field-Of-view, Transmitter UAV orientation ; receive UAV orientation, link range, and Beam width. The analytical results are validated with the monte-carlo simulations. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
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    Bit error rate analysis of polarization shift keying based free space optical link over different weather conditions for inter unmanned aerial vehicles communications
    (Springer, 2021) Nallagonda, V.; Krishnan, P.
    The increasing availability of unmanned aerial vehicles (UAVs) is an exciting part of future emerging technology with advanced scientific and industrial interests. Free space optical (FSO) communications’ ability to offer very high data rates and the mobility of unmanned aerial vehicle (UAV) flying platforms make the delivery of Fifth-Generation (5G) wireless networking services appealing to FSO-UAV-based solutions. UAVs play a greater role in end-to-end delivery in next- generation wireless networking systems, serving as a base station, capacity enhancement, high data access, and other disaster management systems. To establish a link between unmanned aerial vehicles and ground stations, FSO can be applied. But, the different weather conditions liken rain, fog effects on the performance of the FSO link, contributing to the loss of the signal. In this paper, we proposed polarization shift keying (POLSK) modulated FSO link based UAV–UAV communication system for 6G beyond applications. We examine the effect of different weather conditions such as rain, fog on the bit error rate (BER) performance of the proposed system. Novel closed-form expressions for UAV–UAV based FSO propagation channel are derived, and BER performance is investigated under different weather conditions. Fog and rain are the main limiting factors mitigated in this paper by suitable mitigation techniques by increasing receiver field of view. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
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    Bit error rate analysis of ground-to-high altitude platform free-space optical communications using coded polarization shift keying in various weather conditions
    (Springer, 2022) Nallagonda, V.; Krishnan, P.
    High altitude platforms (HAPs) aided free-space optical (FSO) communication, a future emerging technology for next-generation communication systems. HAP aided FSO communication systems, contributing significantly to data hunger applications. Weather conditions, angle of arrival fluctuations, blockages, and pointing error loss due to the HAP’s hovering state are some of the limitations to establishing an efficient link. In this paper, we proposed for the first time a Ground-to-HAP FSO communication system based on polarization shift keying to improve performance under hovering fluctuations. We also improved the proposed system’s performance by employing BCH and repetition coding schemes. The proposed system’s average bit error rate performance is expressed in closed form, and the results are analysed under various weather conditions such as rain (light and heavy) and fog (light and moderate). The results for coded and uncoded cases are compared. The achieved coding gain is 28.5 dB. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
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    Performance enhancement of FSO communication system using machine learning for 5G/6G and IoT applications
    (Elsevier GmbH, 2022) Kumar, L.J.S.; Krishnan, P.; Shreya, B.; Sudhakar, S.
    6G networks will provide extremely high capacity and will support a wide range of new applications in the future, but the existing frequency bands may not be sufficient. Furthermore, because traditional wireless communications are incapable of providing high-speed data rates, 6G enables superior coverage by integrating space/air/underwater networks with terrestrial networks. 5G-and-beyond (5 GB) and 6G networks have been mandated as a paradigm shift to take the enhanced broadband, massive access, and ultra-reliable and low latency services of 5G wireless networks to an even more advanced and intelligent level, to meet the ever-growing quantities of demanding services. In 5G and 6G wireless communication systems, artificial intelligence (AI), particularly machine learning (ML), has emerged as an essential component of fully intelligent network orchestration and management. 5 GB and 6G communication systems will also rely heavily on a tactile Internet of Things (IoT). The diverse nature of heterogeneous traffic and the established service quality parameters in 5 GB networks will present numerous challenges. Many other wireless technologies, including free space optics (FSO), look promising for meeting the demands of 5 GB systems. FSO has been identified as a promising technology for achieving higher data rates while consuming less power. However, attenuation due to weather, pointing errors, and turbulences limits its performance. Traditional Maximum likelihood decoding techniques require prior channel information to decode the signals. in this paper, first time we proposed a novel decoding technique for decoding on–off keying (OOK) modulated FSO signals using support vector machines (SVM). The model is tested under various atmospheric weather conditions such as fog, rain, and snow, as well as turbulence and pointing errors. Simulated numerical results demonstrate that the proposed SVM-based decoding schemes are capable of mitigating attenuation, pointing error, and turbulent channel impairments. © 2021 Elsevier GmbH
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    Reconfigurable intelligent surface-assisted free-space optical communication system under the influence of signal blockage for smart-city applications
    (Optica Publishing Group (formerly OSA), 2022) Naik, R.P.; Krishnan, P.; G.D., G.D.G.
    Atmospheric turbulence and pointing errors represent substantial hurdles to free-space optical communications (FSOs), impeding their practical design. The reconfigurable intelligent surface (RIS) is an emerging technology that enables reflective radio transmission conditions for next-generation 5G/6G wireless frameworks by intelligently adjusting the beam in the desired direction using low-cost inactive reflecting elements. In this paper, we proposed an RIS-assisted FSO system for mitigating the effects of atmospheric turbulence, pointing errors, and communication system signal blockage. The probability density function and cumulative distribution functions of an FSO system composed of N-RIS elements are evaluated in a free-space environment that contains obstructions. We derived closed-form expressions for the proposed system's bit error rate (BER), outage probability, and channel capacity. The proposed system's performance is analyzed in terms of BER, outage probability, and channel capacity under various weather conditions, pointing errors, and signal blockage. The results are plotted as a function of number of RIS elements and average signal-to-noise ratio. The proposed system will be beneficial in smart-city applications since it will provide reliable connectivity in urban environments with a high population density and high-rise buildings. © 2022 Optica Publishing Group
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    Reconfigurable intelligent surface-assisted free-space optical communication link for the Satellite-Internet of Things
    (Optica Publishing Group (formerly OSA), 2023) Naik, R.P.; G.D., G.D.G.; Bhargava Kumar, L.B.; Krishnan, P.
    The Satellite-Internet of Things (S-IoT) is envisaged as one of the promising technological enhancements in this decade due to its outright connectivity, especially in the areas of terrestrial communication andweather forecasting. Invariably, turbulent atmospheric conditions and varied terrain profiles are hindrances for satellite based freespace optical (FSO) communication, and immensely disrupt signal levels. Recently, a new technological invention called a reconfigurable intelligent surface (RIS) empowered radio transmission environments for next generation wireless/optical technology has emerged. Elements of RIS are used to intelligently tune the striking beam towards desired locations. In this paper, we propose an RIS based FSO link to manueuver S-IoT. The challenges of pointing errors and turbulent atmospheric connectivity froma satellite to ground station and vice versa with the cooperation of RIS have been derived and substantiated with closed form solutions. The proposed system's performance has been analyzed using packet and bit error rates, and outage probability over atmospheric turbulence, pointing errors, and signal blockage scenarios.Results are evaluated for different RIS elements as a function of average signal to noise ratio. The proposed system is extremely productive, since this scheme has the capability to provide dependable connectivity in rural, urban, and suburban environments where reliable connectivity is difficult in spite of traditional infrastructures. ©2023 Optica Publishing Group.
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    Experimental Demonstration and Performance Analysis of Free Space and Underwater Optical Wireless Communication Systems
    (Springer, 2024) Kannan, A.; Bhavana, V.; Younus, S.M.; Rehaman, S.M.; Krishnan, P.
    This research paper presents the development and implementation of a real-time communication system that utilizes LEDs for transmitting text, image, and audio through Free Space Optical Communication (FSOC) and Underwater Wireless Optical Communication (UWOC) channels. The impact of atmospheric and oceanic attenuation and turbulences are considered for the performance analysis of the proposed system. The various atmospheric weather conditions like light fog, dense fog, and heavy rain are considered for FSOC while in the case of UWOC, effects like pure water, and seawater with turbulence and without turbulence are considered. The outcomes of the experiments and simulations, including quality factors, eye diagrams, and bit error rates, are plotted and discussed in the results. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.