Faculty Publications

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    Modelling of OFDM based RoFSO system for 5G applications over varying weather conditions: A case study
    (Elsevier GmbH, 2019) Pati, P.S.; Krishnan, P.
    From the perspective of spectrum scarcity, Radio-on-FSO (RoFSO)system is the best available option as it operates at unlicensed optical frequencies with the salient features of high bandwidth, cost effectiveness, lower transmit power, immunity to electromagnetic interference and easy deployment. To cater to the high data rate requirement of 5G applications in the near future, RoFSO systems will definitely be the best assisted alternative technology to the conventional wireless systems. However, the atmospheric conditions and non-linearity of the optical link have got a bearing on the efficiency of the system. In this work, we have presented an analytical model for transmitting phase shift keying (PSK)modulated orthogonal frequency division multiplexing (OFDM)signals through free space optics (FSO)links. RL is the load resistor of the photo detector an Considering optical noises, nonlinear distortion resulting from laser diode and the atmospheric turbulence effect modelled by gamma-gamma distribution, we have derived a closed form closed-form bit error rate (BER)and outage probability expression for the aforementioned transmission system. Pointing error is also factored in for more accurate and appropriate analysis of the system performance. Better system performance was observed through use of aperture averaging technique. A case study has been undertaken for analyzing the FSO system performance with reference to BER for various seasons for the year 2016 over IIIT Bhubaneswar area by considering the wind speed and altitude at different floors of the building of the institute. © 2019 Elsevier GmbH
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    Non-orthogonal space–frequency block codes from cyclic codes for wireless systems employing MIMO-OFDM with index modulation
    (Elsevier B.V., 2019) Raghavendra, R.; Shripathi Acharya, U.S.
    Space–frequency codes (SFC) having error correcting structure can be used to enhance the bit error rate (BER) performance of modern wireless systems (5G and beyond) employing multiple-input multiple-output (MIMO) and multi-carrier communication. In this work, the construction of non-orthogonal space–frequency block codes (NSFBC) from (n,k) cyclic codes has been proposed. In which, n represents the number of symbols in the codeword and k represents the number of symbols in the information sequence. The performance of proposed codes has been evaluated in MIMO systems employing orthogonal frequency division multiplexing and index modulation (MIMO-OFDM-IM). We initially obtained (n,k) full rank cyclic codes for any 1 q m . Further, NSFBCs are obtained from full rank codes using Rank preserving maps. In a 2 × 2 system and a 10-path MIMO channel, the proposed full rank NSFBC with rank-preserving IM mapping (FR-NSFBC-IM), over F 5 2 , provides he similar BER performance when compared to MIMO-OFDM-IM system with Rate-1 Alamouti code and QPSK. Moreover, it provides an improvement in spectral efficiency of about 0.9 b/s/Hz. When compared to the MIMO-OFDM-IM with BPSK, FR-NSFBC-IM codes over F 5 2 provide an asymptotic SNR gain of about 1 dB and also the spectral efficiency has been improved by about 0.6 b/s/Hz. In the 4 × 4 scenario, full rank NSFBCs over F 5 4 with rank deficient IM mapping (RD-NSFBC-IM) provide an improvement in spectral efficiency of about 1.3 b/s/Hz. However, BER performance is similar to that of MIMO-OFDM-IM with BPSK. © 2019
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    High-speed and reliable Underwater Wireless Optical Communication system using Multiple-Input Multiple-Output and channel coding techniques for IoUT applications
    (Elsevier B.V., 2020) Naik, P.N.; Acharya Udupi, S.; Krishnan, P.
    In this paper, we investigate the performance of an Underwater Wireless Optical Communication (UWOC) system employing on–off keying modulation at a data-rate of 500 Mbps over a link-range of 30 m. Transmit/receive diversity schemes, namely Multiple-Input to Single-Output (MISO), Single-Input to Multiple-Output (SIMO) and Multiple-Input to Multiple-Output (MIMO) techniques with and without RS-coding have been employed to mitigate the effects of weak oceanic turbulence and beam attenuation. The novel closed-form analytical Bit Error Rate (BER) expressions of Single-Input to Single-Output (SISO), SIMO, MISO and MIMO links for un-coded and RS-coded cases have been computed using the hyperbolic tangent distribution and validated with Monte-Carlo simulation results. The obtained BER results show that the use of (63,51) RS-coded 4 × 5 MIMO UWOC system offers at-least 35 dB of transmit power gain compared with the un-coded SISO UWOC system at a BER of 10?5. Emerging technologies like the fifth-generation (5G) networks and the Internet of Underwater Things (IoUT) will have a high impact on UWOC as these systems require a high degree of information integrity, high data rates and energy efficiency when employed in conjunction with data transfer between underwater vehicles and objects. The proposed RS-coded MIMO UWOC system offers high reliability and power efficiency and it has the potential to be gainfully employed in IoUT applications. © 2020 Elsevier B.V.
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    Performance analysis of RoFSO links with spatial diversity over combined channel model for 5G in smart city applications
    (Elsevier B.V., 2020) Kumar, A.; Krishnan, P.
    The smart city concept improves the lives of citizens and optimizes the efficiency of city operations, services through the integration of information and communication technology with the help of the internet of things (IoT) and 5G techniques. The bandwidth demand for 5G, smart city, and IoT applications are fulfilled with wireless optical communications. Particularly, radio over free space optical (RoFSO) communication establishes a very attractive choice for interconnecting central base stations with remote antenna units. In this paper, we consider the transmission of orthogonal frequency division multiplexing (OFDM) radio signals with quadrature amplitude (QAM) modulation format through a free space optical link using spatial diversity mitigation technique. The atmosphere is modeled as the combined channel model which takes into account atmospheric attenuation, turbulence, and pointing errors. The atmospheric turbulence and pointing errors are modeled by Malaga, Beckmann, and Rayleigh distributions. The novel closed form BER expressions are derived for the proposed QAM OFDM RoFSO link with spatial diversity. The results are analyzed and plotted for different weather conditions (clear, haze, light fog), turbulence regimes (weak, moderate, strong), misalignment (weak, enhanced), the order of QAM and number of transceivers. The proposed RoFSO system is highly useful for 5G in smart city applications. © 2020 Elsevier B.V.
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    An electronically switchable UWB to narrow band antenna for cognitive radio applications
    (John Wiley and Sons Inc. P.O.Box 18667 Newark NJ 07191-8667, 2020) Jacob, N.; Kulkarni, M.; Kandasamy, K.
    Cognitive radio (CR) is designed to achieve intelligent spectrum sensing and sharing, in order to solve spectrum underutilization problem. Conventional CR uses multiple/multiport antenna to switch between UWB and narrow band (NB) frequencies for primary and secondary users. In this article, we propose a compact frequency reconfigurable single port antenna using PIN diodes, to switch between UWB and NB frequencies. A circular disc monopole antenna with partial ground plane is designed to deliver UWB response. Three interdigital capacitors (IDC) are electrically connected to a partial ground plane and feed line using PIN diodes. OFF condition of all PIN diodes will provide the UWB response of 2.8 to 10.6 GHz and ON condition of the diodes will result in 36 different NB frequencies, completely covering the UWB spectrum. A simulation study carried out by incorporating a varactor diode into IDC, clearly shows that, the antenna resonance can be switched using PIN diodes and each resonant frequency can be fine-tuned independently, with in the band of interest. This is the unique feature of proposed antenna, which facilitates the technology for CR based internet of things applications in 5G wireless communication networks. © 2020 Wiley Periodicals, Inc.
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    Performance analysis of 65 nm CMOS LNA using SSL technique for 5G cellular front-end receivers
    (Elsevier GmbH k.ernst@elsevier.com, 2020) R, V.; Gorre, P.; Song, H.; Kumar, S.
    This paper presents a performance analysis of a wideband low noise amplifier (LNA) that utilizes a 65 nm CMOS Samsung mm-wave process. The proposed CMOS LNA designed with new built-in techniques will overcome the challenges faced by device parasitic and electromagnetic (EM) losses. A suspended substrate line (SSL) is characterized and analyzed with its dual-band operation and achieves excellent EM compatibility. The traditional EM losses in bulk active and passive components have been incurred using built-in techniques to provide better linearity of LNA. The proposed mm-wave LNA enables it's each family component to avoid leakage of EM waves and its interconnected parasitic losses in layout. An SSL based parallel-series network is optimized to achieve a wide bandwidth of 26 GHz to 34 GHz. The full design of LNA achieves the highest peak gain of 25 dB by using proper 50 ? matching constraints over the wideband response of 27.8 GHz to 32.5 GHz. The fabricated chip of LNA is given a supply voltage of 1.2 V, and the calculated chip area is 0.35*0.22 mm2. The simulation and measurement results demonstrate the minimum noise figure of 2.5 dB and achieve the highest stability factor in the desired band of operation. The LNA also measured linearity with a 1 dB compression point where input power of ?19dBm has obtained at 30.5 GHz. © 2020 Elsevier GmbH
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    Robust and secure authentication protocol protecting privacy for roaming mobile user in global mobility networks
    (Inderscience Publishers, 2021) Madhusudhan, R.; Suvidha, K.S.
    With the advent of new 5G technology there is a need to develop security architecture. Two factor authentication schemes are developed to address the security features such as user anonymity and privacy preservation during roaming scenario in GLObal Mobility NETwork. The entire communication during roaming is carried over insecure channel and owing to this, security concern is raised. The main objective of the proposed protocol is to secure the channel and to overcome all active and passive security attacks. The proposed protocol addresses the active and passive security attacks that exist in 5G cellular networks which are formally verified using AVISPA tool. The proposed protocol is simulated using NS2.35 simulator and the performance metrics such as throughput, end to end delivery and packet delivery ratio are computed. The protocol is efficient in terms of computational and communication cost. The proposed scheme is robust and practically implementable. © 2021 Inderscience Enterprises Ltd.
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    A 8–12 GHz, 44.3 dBm RF output class FF?1 DPA using quad-mode coupled technique for new configurable front-end 5G transmitters
    (Springer, 2021) Kumar, R.; Dwari, S.; Kumar Kanaujia, B.K.; Kumar, S.; Song, H.
    This paper presents a high-efficiency Class FF - 1 DPA using the quad-mode coupled technique for new configurable front-end 5G transmitters. The proposed DPA consists of carrier PA, main PA, input–output matching network and hybrid power network (HPN). The HPN includes a quad-mode coupled technique which is four-section U-shaped transmission line. The HPN is used for even–odd mode impedance analysis to ensures the high-selectivity of output power and achieve a wideband response in the presence of harmonic control conditions. The optimum harmonic impedance is analyzed for the desired band to achieve high output power and efficiency. The DPA circuit is fabricated by using 0.25 µm GaN HEMT on silicon nitride monolithic microwave integrated circuit die process. At maximum output power level of 44.3 dBm, the delivered power-added efficiency (PAE) of 64.3–67.3% and drain efficiency (DE) of 71.7–73.7% at even–odd mode operation are achieved with a gain of 13.0–14.3 dB. For the output power level of 39.045 dBm corresponding to 9 dB output back-off (OBO), the drain efficiency lies between 55–62% with 73% fractional bandwidth. All the demonstrated transmission parameters are working in the band of 8–12 GHz. The size of the chip is 2.8 × 1.9 mm2 and it occupies less die area as compared to the existing DPAs. © 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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    Robust transmission using channel encoding towards 5G New Radio: A telemetry approach
    (Elsevier Ltd, 2021) Sharma, V.; Arya, R.K.; Kumar, S.
    This paper presents a robust channel encoding scheme under adaptive modulation and coding for a massive machine type communication device in 5G new radio. For the very first time, mode-selection and distance statistics algorithms have been simultaneously evaluated, in which together it provides the closest approximation of efficient adaptive modulation and coding with robust transmission. The prediction of optimum adaptive modulation and coding is based on the analysis of uplink packet using distance statistics, and downlink packet using mode-selection mechanism. The performance of 5G new radio by incorporating OFDM subcarrier has been evaluated using analytical as well as simulation approach. Mode-selection algorithm has been considered to predict the environmental condition under a fading channel while the distance statistics provide feedback of the previously transmitted channel condition. The result of both the approaches provide a better bit error rate for adaptive modulation & coding profile under 1/4, 1/18, 1/16 and 1/32 cyclic prefix. © 2021