Faculty Publications
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Item Non-orthogonal full rank space-time block codes over Eisenstein-Jacobi integers for MIMO systems(Institute of Electrical and Electronics Engineers Inc., 2017) Raghavendra, R.; G.D., G.S.; Shripathi Acharya, U.In this work we present a full rank Space Time Block Codes with Non-orthogonal designs designated as NSTBCs constructed from cyclic codes over GF(qm). Rank-Preserving Eisenstein-Jacobi map is employed to map the codewords over finite field to codewords over complex field. A generalized procedure for designing NSTBCs for MIMO system containing Nt Transmit antennas and Nr receive antennas is obtained. The computational complexity of the MIMO system employing the presented NSTBC with ML detection has been derived and an upper bound on the average probability of error is presented. It is shown that under quasi-static Rayleigh flat fading channel conditions at an ABER of 10-4 the proposed NSTBC MIMO system provides a gain of approximately 3 dB in compared with C (4,2,4) code. © 2017 IEEE.Item Performance of SM-NSTBC for Correlated HAP Fading Channels with Imperfect-CSI(Springer, 2020) Godkhindi Shrutkirthi, S.; G.D., G.D.; Shripathi Acharya, U.This paper analyzes the performance of Spatially Modulated Non-orthogonal Space Time Block Code (SM-NSTBC) scheme for a correlated high altitude platform (HAP) MIMO system in the presence of imperfect channel state information (Imp-CSI). The proposed SM-NSTBC employs cyclic codewords derived over Galois Field, which satisfies full rank property. The performance of SM-NSTBC is compared with traditional STBCs such as SM-OSTBC and STBC-SM schemes. It is observed through simulations that SM-NSTBC outperforms SM-OSTBC and STBC-SM schemes by a minimum of 2 dB in HAP correlated environments. Monte-Carlo simulations have been performed to validate the claims. © 2020, Springer Nature Singapore Pte Ltd.Item Experimental Evaluation of Reliable Underwater Optical Communication in the Presence of Turbulence and Blockage(Springer Science and Business Media Deutschland GmbH, 2020) Prasad Naik, R.; Shripathi Acharya, U.; Suyan, N.K.In this paper, we have evaluated the performance of underwater wireless optical communication (UWOC) link in the presence of turbulence, air bubbles and blockage of 2.5-m-length channel. To mitigate the effects of turbulence and air bubbles, we have employed channel coding and receiver diversity combining techniques. Blocking causes the burst errors, and to mitigate the effect of blocking, we have employed interleaved channel-coded receiver diversity combining technique. Bit error rate (BER) performance of UWOC system evolved, and improvement in BER is achieved by employing channel codes, receiver diversity combining and interleaved channel codes. © 2020, Springer Nature Singapore Pte Ltd.Item Sustainable Off-Grid Electricity Generation System for Low Power Lighting in Remote Locations(Institute of Electrical and Electronics Engineers Inc., 2020) Shenoy, B.B.; Mitra, J.; Shripathi Acharya, U.; Laxminidhi, T.This paper proposes an environmental friendly and sustainable approach to generate electricity for small lighting applications in rural and remote locations. In the proposed system, human muscle energy, abundantly available in rural and remote locations, has been converted into electrical energy to be stored in an alternative energy storage device, e.g. a supercapacitor. The usual bicycle with a minor modification is plugged to a charging platform. The charging platform has a power processing circuit and a Permanent Magnet Direct Current generator. The system has the ability to power up a 1 W white LED lamp for a duration of approximately 60 minutes, when the bicycle is pedaled for 4 minutes. The proposed system is not only eco-friendly, but also effectively caters to the challenges posed by seasonal variations and locational disadvantages and is targeted specifically for locations which are not having access to the power grid. © 2020 IEEE.Item FPGA Accelerated Track to Track Association and Fusion for ADAS Distributed Sensors(Institute of Electrical and Electronics Engineers Inc., 2023) Gopala Swamy, B.; Reddy, G.H.; Srihari, P.; Shripathi Acharya, U.; Pardhasaradhi, B.The integration and amalgamation of sensor data in the automotive domain play a pivotal role in informing real-time decision-making for advanced driver assistance and safety (ADAS) systems. In a distributed architecture, the track-to-track association (T2TA) modules are responsible for associating the correct track pairs and subsequently fusion modules fuses the information. The T2TA and fusion modules operate within the CPU framework, often leading to elevated latency across the system. This paper introduces digital signal processing (DSP) architectures for the T2TA and fusion modules, designed to meet stringent constraints in terms of both area and latency. These modules encompass critical operations such as matrix inversion, vector-to-matrix multiplications, and matrix-to-matrix multiplications. The challenge of vector-to-matrix multiplications is effectively addressed through the utilization of the constant co-efficient multiplication technique. Additionally, matrix-to-matrix multiplication is performed by employing a vector-to-vector multiplication architecture with Block RAMs (BRAMs). Further-more, matrix inversion is realized through the LU decomposition method. Moreover, this paper presents an innovative approach to expedite the T2TA and fusion modules by harnessing folded DSP architecture within a system-on-chip (SOC) framework. The results of simulations substantiate that the proposed architectures exhibit a remarkable suitability for applications necessitating low area, low power consumption, and high throughput capabilities. © 2023 IEEE.Item Performance of Orthogonal and Non-Orthogonal Space Time Block Code Through the Underwater Wireless Optical Channels(IEEE Computer Society, 2023) Naik, R.P.; Mans, R.; Shripathi Acharya, U.; Savidhan Shetty, C.S.Multiple input multiple output (MIMO) schemes have been integrated with the space-time (ST) codes to enhance the reliability of information transfer across the wireless channel. Due to their rich algebraic structure, space time block codes (STBCs) such as orthogonal STBCs (OSTBC), quasi-orthogonal STBC (QOSTBC), and non-orthogonal STBCs (NOSTBC), offer efficient implementation of a reliable communication system. The underwater wireless optical communication (UWOC) channel is perturbed by the weak turbulence and fading (referred as scintillation), and shares many properties with a wireless channel. In this paper, we have designed OSTBC/QOSTBC and NOSTBC schemes for UWOC system, which can significantly improve the integrity of information transfer across the underwater optical wireless channels. These codes have been suitably conditioned to operate with an UWOC system employing intensity modulation. Monte-Carlo bit error rate simulations of the proposed schemes are plotted and presented with respect to the available transmit power in dB. © 2023 IEEE.Item A comprehensive framework for Double Spatial Modulation under imperfect channel state information(Elsevier B.V., 2017) G.D., G.S.; Koila, K.; Raghavendra, R.; Shripathi Acharya, U.The essential requirement for a 5G wireless communication system is the realization of energy efficient as well as spectrally efficient modulation schemes. Double Spatial Modulation (DSM) is a recently proposed high rate Index Modulation (IM) scheme, designed for use in Multiple Input Multiple Output (MIMO) wireless systems. The aim of this scheme is to increase the spectral efficiency of conventional Spatial Modulation (SM) systems while keeping the energy efficiency intact. In this paper, the impact of imperfect channel knowledge on the performance of DSM system under Rayleigh, Rician and Nakagami-m fading channels has been quantified. Later, a modified low complexity decoder for the DSM scheme has been designed using ordered block minimum mean square error (OB-MMSE) criterion. Its performance under varied fading environments have been quantified via Monte Carlo simulations. Finally, a closed form expression for the pairwise error probability (PEP) for a DSM scheme under conditions of perfect and imperfect channel state information has been derived. This is employed to calculate the upper bound on the average bit error probability (ABEP) over aforementioned fading channels. It is observed that, under perfect and imperfect channel conditions DSM outperforms all the other variants of SM by at least 2dB at an average bit error ratio (ABER) of 10?5. Tightness of the derived upper bound is illustrated by Monte Carlo simulation results. © 2017 Elsevier B.V.Item Signal constellations employing multiplicative groups of Gaussian and Eisenstein integers for Enhanced Spatial Modulation(Elsevier B.V., 2017) G.D., G.S.; Raghavendra, R.; Koila, K.; Shripathi Acharya, U.In this paper, we propose two new signal constellation designs employing Gaussian and Eisenstein Integers for Enhanced Spatial Modulation (ESM). ESM is a novel technique which was propounded by Cheng et al. The advantage of ESM over other Spatial Modulation (SM) schemes lies in its ability to enhance spectral efficiency while keeping the energy efficiency intact. This is done by activating either one or two antennas judiciously depending upon the required trade-off. In ESM, information radiated from the antennas depends upon index of the active transmit antenna combination(s) and also on the set of constellation points chosen, which may include points from multiple constellations. In this paper, we propose signal constellations based on multiplicative groups of Gaussian and Eisenstein integers. The set comprising of Gaussian and Eisenstein integers serves as primary and secondary constellation points for Gaussian Enhanced Spatial Modulation (GESM) scheme. The secondary constellation points are deduced from a single geometric interpolation from the primary constellation points. The Monte Carlo simulation results indicate that the proposed nonuniform constellations achieve impressive SNR gains compared to conventional constellation points used in the design of ESM. This new design has been described for MIMO employing 4 × 4 and 8 × 8 antenna configurations with only two active antennas. Furthermore, a closed form expression for the pairwise error probability (PEP) for the GESM scheme has been deduced. The PEP is utilized to determine the upper bound on the average bit error probability (ABEP). Our simulations indicate that the proposed GESM from Gaussian and Eisenstein integers scheme outperforms all the other variants of SM including conventional ESM by at least 2.5 dB at an average bit error ratio (ABER) of 10?5. Close correspondence between the theoretical analysis and the Monte Carlo simulation results are observed. © 2017 Elsevier B.V.Item Index modulation aided multi carrier power line communication employing rank codes from cyclic codes(Elsevier B.V., 2020) Raghavendra, M.A.N.S.; Shripathi Acharya, U.In a multi-carrier power line communication (mPLC) with dominant Narrowband and Impulse noise, crisscross errors can be clearly observed. In this work, mPLC employing Rank codes with Index modulation (mPLC-IM) has been considered to provide a reliable high data rate communication over the powerline channel. The rank codes required for this implementation have been derived from cyclic codes over GF(qm) viewed as m×n matrices over GF(q). Encoding has been performed by employing the Galois Field Fourier Transform (GFFT) domain description of cyclic codes. This scheme is able to correct a variety of crisscross errors in mPLC-IM The GFFT approach provides an additional degree of freedom that is offered by choice of free transform component indices. It can be used to design an index key scheme which can enhance the physical layer security of an mPLC system. In the absence of knowledge of the index key, it is observed that the probability of error reaches an error floor of ?10?2, highlighting the need for index key for appropriate decoding. Further, a novel check matrix construction is proposed and used in devising a decoding strategy. It is observed that the proposed decoder is capable of correcting any errors of rank ??m?12?. In mPLC-IM with OFDM, the proposed codes over GF(24) provide an asymptotic gain of approximately 3 dB when compared to the uncoded system. For mPLC-IM with multi-tone Frequency Shift Keying (FSK), the proposed RC over GF(24) provides a 25% improvement in symbol error rate (SER) at lower values of p (probability of occurrence of narrowband noise) when compared to Reed-Solomon (RS) based Constant Weight (CW) CW(13,6,5)2?RS[15,14,2]16 codes. Further, a SER improvement of around 30% is achieved using rank codes (RCs) over GF(28) when compared with CW(9,4,4)2?RS[15,14,2]16. In the presence of dominant background noise, the BER graphs show that the proposed codes are equivalent (slightly superior) in performance as that of Low Rank Parity Check (LRPC)/Gabidulin based designs. In the presence of dominant impulse noise, the proposed system is providing significant gain when compared with the Linearly Pre-coded Orthogonal Frequency Division Multiplexing (LP-OFDM) system and LRPC based scheme. Additionally, simulation results show that, in the absence of an index key, the probability of error reaches the error floor, highlighting the need for index key for appropriate decoding. This can be viewed as the code capable of providing an additional layer of security. © 2019 Elsevier B.V.