Browsing by Author "Shripathi Acharya, U.S."

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3-D radar imaging using extended 2-D range migration technique
(Institute of Electrical and Electronics Engineers Inc., 2017) Nagarad, S.R.; Sourabh, A.S.; Shripathi Acharya, U.S.; Srihari, P.; Prasad, S.; Rao, P.H.
A three dimensional (3-D) imaging system is implemented by employing 2-D range migration algorithm (RMA) for frequency modulated continuous wave synthetic aperture radar (FMCW-SAR). The backscattered data of a 1-D synthetic aperture at specific altitudes are coherently integrated to form 2-D images. These 2-D images at different altitudes are stitched vertically to form a 3-D image. Numerical simulation for near-field scenario are also presented to validate the proposed algorithm. Â© 2017 IEEE.
A MIMO SM-NSTBC Scheme for High Altitude Platform Communication Systems: Study and Analysis
(Institute of Electrical and Electronics Engineers Inc., 2019) Shrutkirthi, G.S.; G.D., S.G.D.; Shripathi Acharya, U.S.
In this paper, the performance of a novel non-binary Spatially Modulated Non-orthogonal Space Time Block Code (SM-NSTBC) scheme for High Altitude Platform (HAP) communication systems is designed and analyzed. SM-NSTBC utilizes full rank length n cyclic codewords derived over Galois Field (GF(q{m})), where (nvert q{m}-1 and m < n). In order to obtain higher spectral efficiencies in terms of data rate, NSTBC schemes have been devised. SM-NSTBC gives an improvement in the BER performance of âˆ¼ 3 dB as compared to other conventional STBC-SM schemes given in literature. Monte Carlo simulations have been performed to validate the results. The computational complexity of the proposed scheme has been analytically derived and estimated. Â© 2019 IEEE.
BER Performance Analysis ofÂ Optical Wireless Communication System overÂ Weak andÂ Strong Underwater Turbulence Channels
(Springer Science and Business Media Deutschland GmbH, 2023) Naik, R.P.; Shripathi Acharya, U.S.; Bhargava Kumar, L.B.; Krishnan, K.; Chung, W.-Y.
In this paper, we have investigated the performance of an underwater wireless optical communication (UWOC) link employing single-input and single-output (SISO) and selection combining (SC) as receiver diversity for varying link-ranges. As the the link-range increases, then strength of turbulence between the underwater optical entities also increases. It is assumed that the distribution of light propagation in weak and strong turbulence UWOC channel as log-normal (LN) and gamma-gamma (GG) density functions, respectively. The analytical bit error rate (BER) equations of onâ€“off keying modulated UWOC link have been derived for SISO and SC receiver diversity using hyperbolic tangent distribution for LN and power series for GG density functions. The analytical BER results are validated with the Monte Carlo simulations. Â© 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
DSP Architectures of Covariance Intersection Fusion Algorithm for Automotive Sensor Fusion
(Institute of Electrical and Electronics Engineers Inc., 2023) Praharshita, D.S.L.; Achala, G.; Srihari, P.; Shripathi Acharya, U.S.; Pardhasaradhi, B.
The data fusion from sensors within the automotive vehicle is vital for improved accuracy and safety. The centralized and information matrix fusion (IMF) algorithms are famous for providing an optimal fusion estimate. However, the IMF is not viable in automotive sensor fusion applications due to the limited bandwidth and low hardware resources. Hence, distributed fusion technology is widely adopted in the automotive sensor applications to achieve high-speed and low-area realizations. This paper proposes three digital signal processing (DSP) architectures for covariance intersection (CI) fusion algorithm: Pipelined-traditional CI, adder-ladder CI, and pipelined adder-ladder CI. The proposed DSP architectures are evaluated with hardware resource consumption (multipliers, adders, and delays), maximum achievable frequency, and latency of the architecture. In addition, proposed CI algorithms for Digital Signal Processing (DSP) architectures are compared with IMF DSP architectures. The hardware resources and optimal pipeline stages required for CI with respect to N number of sensors are provided. The traditional pipeline algorithm requires N number of stages where as the proposed pipelined version of adder-ladder CI requires a N-1 pipeline stage with additional 7N-1 and 7N-3 delay elements for even and odd number of sensors to achieve the overall system operating frequency to an operation of multiplier. The proposed DSP architectures are suitable for automotive sensor fusion due to their high operating frequency and low hardware resources. Â© 2023 IEEE.
Energy efficient rateless codes for high speed data transfer over free space optical channels
(SPIE spie@spie.org, 2015) Prakash, G.; Kulkarni, M.; Shripathi Acharya, U.S.
Terrestrial Free Space Optical (FSO) links transmit information by using the atmosphere (free space) as a medium. In this paper, we have investigated the use of Luby Transform (LT) codes as a means to mitigate the effects of data corruption induced by imperfect channel which usually takes the form of lost or corrupted packets. LT codes, which are a class of Fountain codes, can be used independent of the channel rate and as many code words as required can be generated to recover all the message bits irrespective of the channel performance. Achieving error free high data rates with limited energy resources is possible with FSO systems if error correction codes with minimal overheads on the power can be used. We also employ a combination of Binary Phase Shift Keying (BPSK) with provision for modification of threshold and optimized LT codes with belief propagation for decoding. These techniques provide additional protection even under strong turbulence regimes. Automatic Repeat Request (ARQ) is another method of improving link reliability. Performance of ARQ is limited by the number of retransmissions and the corresponding time delay. We prove through theoretical computations and simulations that LT codes consume less energy per bit. We validate the feasibility of using energy efficient LT codes over ARQ for FSO links to be used in optical wireless sensor networks within the eye safety limits. Â© 2015 SPIE.
Experimental studies on realization of underwater optical communication link
(Institute of Electrical and Electronics Engineers Inc., 2017) Kumar, A.; Naik, R.P.; Shripathi Acharya, U.S.
A comprehensive experimental setup for underwater optical communication (UWOC) is proposed in this paper. This UWOC real time setup provides an underwater communication link (using sea water) which is able to achieve reliable communication within a 3m long range. The minimum transmit power requirement for communication at a Bit Error Rate (BER) of 10-3 in the presence of turbulence (generated within the experimental setup) and stationary water has been determined. Two UWOC setups are implemented, first setup is designed by utilizing opaque PVC pipes and the second setup is designed by aquarium tank. These setups are used in conjunction with water jets and rotating plates (to bring about obstruction in the line of sight) to replicate conditions of underwater turbulence and blockage. This allows a realistic reconstruction of light wave propagation under the surface of the sea. Our proposed setup provides a platform for experimental studies on UWOC and convey the idea and it is helpful in the analysis of real time power budget required by the system. It provides a foundation for more comprehensive experimental platforms which will be designed to accurately mimic various disruptions that can be encountered with UWOC. The proposed UWOC helps in the development of constructive techniques that can mitigate the effects of the channel induced errors and ensure error free communication. Â© 2017 IEEE.
FPGA Accelerated Automotive ADAS Sensor Fusion
(Institute of Electrical and Electronics Engineers Inc., 2023) Swamy, B.G.; Pardhasaradhi, B.; Shripathi Acharya, U.S.; Srihari, P.; Reddy, S.; Annavajjala, R.
Fusion of multi-modal sensor data is crucial to improve the performance of advanced driver assistance and safety systems. Usually, sensors such as radars, lidars, and cameras work individually to provide the time-varying kinematics (also referred to as tracks) of other vehicles and objects in the field of view of the ego vehicle. Further, these individual tracks are fused in a decentralized manner to achieve the fused tracks. For an automotive vehicle, low-latency and high-speed sensor fusion is a requirement to improve the overall safety. Rather than running the entire fusion algorithm in the central processing unit, some portion of the code or the whole fusion algorithm can be accelerated on a field programmable gate array to improve the overall functionality. With this objective, in this paper we propose a dedicated digital signal processing (DSP) architecture to realize the fusion algorithm which involves computation of fused state and covariance matrix by making use of matrix-to-matrix multiplications and matrix inversion. The matrix inversion is carried out using an efficient LU decomposition method, and matrix multiplication is realized as a vector-to-vector multiplication DSP architecture. Moreover, a folded DSP architecture is proposed for the state and covariance sub-modules to accelerate the overall functionality. Simulations are presented for two-dimensional constant velocity (CV) model with 4-dimensional state space, three-dimensional CV model with 6-dimensional state space, and three-dimensional constant acceleration (CA) model with 9-dimensional state space. Our results indicate that the proposed architecture is well suited for automotive sensor fusion. Â© 2023 IEEE.
FPGA Implementation of SSRS Codes for NAND Flash Memory Device
(Institute of Electrical and Electronics Engineers Inc., 2024) Achala, G.; Nandana, S.; Jomy, F.; Girish, M.M.; Shripathi Acharya, U.S.; Srihari, P.; Cenkarmaddi, L.R.
NAND flash memory is a non-volatile storage device that is extensively used in personal electronic gadgets, digital television, digital cameras, and many consumer/ professional electronics devices. Error control coding techniques have been incorporated to improve the integrity of information stored in these devices. We have synthesized the Subfield Subcodes of Reed Solomon codes (SSRS) for use on Multi-Level cell (MLC), Triple Level Cell (TLC), and Quadruple Level Cell (QLC) NAND flash devices. The primary advantage of these codes is that the codeword symbols can be correctly matched to the number of bits that can be stored in these multilevel cells. Deployment of these codes improves the integrity of information storage and useful life. This paper describes the implementation of the encoder and decoder of SSRS codes synthesized for MLC, TLC, and QLC NAND flash devices. The encoder circuit is designed using addition and multiplication tables derived from elements of synthesized SSRS codes. The Non-binary decoding procedure consists of the syndrome computation, Berlekamp -Massey algorithm, Chein search, and Forney's algorithm. The designed encoder requires 16% resources for MLC, 18% of resources for TLC, and 18% of resources for QLC. This research work has reported the design of very high rate (R ≥ 0.97) codes that can bring about significant improvements to the Undetected Bit Error Rate (UBER) even when the Raw Bit Error rate (RBER) values are significant (> 10-3). © 2013 IEEE.
Generalized designs for precoded receive spatial modulation derived from non-orthogonal space time block codes
(Springer, 2022) Shashikant, S.G.; G.D., G.D.G.; Shripathi Acharya, U.S.
In this paper, a new MIMO scheme termed as precoded Spatially Modulated Non-orthogonal Space Time Block Code (precoded SM-NSTBC) is proposed. The primary concept of precoded SM-NSTBC is to activate a subset of receive antennas in a pre-defined manner and choose specific activated patterns to represent information symbols. We have synthesized schemes derived from full rank Cyclic codes defined over Galois field Rank preserving transformations are used to map the full rank codewords over a finite field to full rank Space Time Block Codes. Due to the characteristics of full rank Cyclic codes employed, a performance improvement of approximately 2 dB to 7 dB is observed. This advantage is realized when the performance of these schemes is compared with precoded SM-OSTBC and precoded STBC-SM. The improvement due to the coding gain is observed in both uncorrelated as well as correlated Rayleigh fading environments. An upper bound on the average bit error rate (ABER) is derived. Close correspondence between Monte-Carlo simulations and analytic values are observed. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
High-Frequency and Low-Latency DSP Architecture for Information Matrix Fusion
(Institute of Electrical and Electronics Engineers Inc., 2021) Praharshita, D.S.L.; Pardhasaradhi, B.; Srihari, P.; Shripathi Acharya, U.S.; Sharma, G.V.K.
The centralized fusion architecture gives optimal global estimate by fusing all the measurements pertaining to a given target. The centralized architectures are computationally huge and requires full data rate requirements. Hence, in practice, decentralized architectures with Information matrix fusion (IMF) is popular to derive an estimate which is equal to optimal global estimate accomplished in centralized architecture. In this paper, a digital signal processing (DSP) architectural minimization technique of pipelining is applied to derive the highspeed IMF. We proposed two different DSP architectures, namely pipelined traditional IMF and pipelined adder-ladder IMF to reduce the critical path, which inturn, increases the architecture's operating frequency. Further, we derived an optimal number of pipeline stages and hardware resources that are required for a generalized N sensors case. The proposed pipelined adder-ladder IMF configuration requires a N + 1 pipeline stage and N + 2 pipeline stages for an even number of sensors and an odd number of sensors respectively. Besides that, The pipelined traditional IMF requires 2N + 1 stages to optimally pipeline and achieve the same operating frequency as that of pipelined adder-ladder IMF. Furthermore, the proposed pipelined adder-ladder IMF is superior in performance (less hardware and less latency) compared to pipelined traditional IMF. The theoretical analysis is performed with metrics (critical path, number of resources, and maximum achievable frequency) to compare various architectures presented in this research work. Â© 2021 IEEE.
Human Muscle Energy Harvesting: Models and Application for Low Power Loads
(IEEE Computer Society help@computer.org, 2018) Shenoy, B.B.; Laxminidhi, L.; Shripathi Acharya, U.S.; Mitra, J.
This paper presents models for human muscle power which can be harvested and utilized for low power applications. The low power application considered in this paper is the case of off-grid rural electrification, where a person in a rural area uses a bicycle-based human power generating system to charge a battery for the purpose of lighting his home with a few low-wattage LED lamps during periods of necessity. In this regard, two methods to convert energy from human muscle activity into useful electricity by utilizing the commonly available bicycle are proposed and presented with hardware results. The presented hardware results prove that power of the order of 50 W can be successfully generated using these methods. Another important feature is that, the methodology involved in generating useful electricity is carbon-free and power can be generated at any given point of time regardless of location or the associated climatic condition. Â© 2018 IEEE.
Link budget for a terrestrial FSO link and performance of space time block codes over FSO channels
(Institution of Engineering and Technology, 2019) Shah, A.; Moorthy, K.K.N.; Kallapur, P.R.; Shripathi Acharya, U.S.
[No abstract available]
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
On the Design of SSRS and RS Codes for Enhancing the Integrity of Information Storage in NAND Flash Memories
(Institute of Electrical and Electronics Engineers Inc., 2023) Achala, G.; Shripathi Acharya, U.S.; Srihari, P.
The revolution in the field of information processing systems has created a huge demand for reliable and enhanced data storage capabilities. This demand is being met by advances in channel coding algorithms along with upward scaling of the capacities of hardware devices. NAND Flash memory is a type of non-volatile memory. Scaling of the size of flash memories from Single Level Cell (SLC) devices to Multilevel cell (MLC) devices has increased the storage capacity. However, these multi-bit per cell architectures are characterized by significantly higher Raw Bit Error Rate (RBER) values when compared with SLC architectures. The requirement of low Undetected Bit Error Rate (UBER) values has motivated us to synthesize powerful channel codes for enhancing the integrity of information Storage in multi-level NAND Flash Memory devices. This paper describes the synthesis of novel Subfield Subcodes of Reed Solomon Codes (SSRS) and Reed-Solomon (RS) codes which are matched to multi-bit per cell architectures. UBER values have been calculated for each of the synthesized codes described in this paper. This allows the determination of the performance and the improvement in data storage integrity brought by using these codes. We have shown that the synthesized SSRS and RS codes can provide very low UBER even when the corresponding RBER values are appreciable. As RS codes permit the detection and correction of a greater number of errors for a given code length, their performance is superior to that of SSRS codes. This improved performance is obtained at the cost of greater complexity of encoding and decoding processes. © 2013 IEEE.
On the Synthesis of Channel Codes for NAND flash devices in Space Application
(Institute of Electrical and Electronics Engineers Inc., 2024) Achala, G.; Srihari, P.; Shripathi Acharya, U.S.
NAND flash memory technology is an important component that is vital in enabling data storage and processing capabilities for deep space missions. Thus, it plays an important role in contributing to the success and scientific outcomes of exploration endeavors beyond Earth's orbit. Its non-volatile characteristic guarantees data integrity even when power is unavailable, a critical attribute for extended missions where power resources are constrained. To improve the data integrity in NAND flash devices used in space applications, appropriate channel codes have to be incorporated. In this work, we have synthesized channel codes for two different NAND flash memory architectures used in space applications. The designed codes provide improved bit error rates when compared with the state-of-the-art. By incorporating suitably designed Subfield Subcodes of Reed Solomon (SSRS) codes in flash memory devices, the device is able to return stored data at acceptable bit error rates even when the raw bit error rate is as high as 10-3 Â© 2024 IEEE.
Performance analysis of concatenated convolutional and Reed Solomon coding with interleaving in optical communication channels
(Institute of Electrical and Electronics Engineers Inc., 2015) Devi, N.D.; Shripathi Acharya, U.S.
For reliable and error free transmission of data in communication systems we require a system employing forward error correction schemes. This paper analyze the performance comparison of Convolution code, Reed-Solomon code as well as concatenation of Convolution code and Reed-Solomon code over optical communication links with interleaving in terms of their probability of Bit error rate and signal to noise ratio with different code rate and identify with code rate will give best performance. Â© 2015 IEEE.
Performance Analysis of Dual-Hop AF/DF Relay Utilizing BCH Code in an Underwater Vertical Wireless Optical Link
(Institute of Electrical and Electronics Engineers Inc., 2024) Savidhan Shetty, C.S.; Achala, G.; Prasad Naik, R.; Shripathi Acharya, U.S.; Chung, W.-Y.
Many attempts have been made to realize effective communication from the sea surface to ocean depths. One promising emerging technology is the deployment of underwater vertical wireless optical links to establish reliable and high-speed communication. In this study, we have attempted to evaluate the performance of an underwater vertical wireless optical communication (UVWOC) link operating beneath the ocean surface, utilizing amplify and forward (AF) as well as decode and forward (DF) relay systems. The investigation focuses on a vertical link traversing multiple layers of turbulence. The channel modeling of multiple layers under weak turbulence and strong turbulence conditions employs hyperbolic tangent log-normal and gamma-gamma distributions. Novel closed-form expressions are developed to quantify the average bit error rate and outage probability for dual-hop AF/DF relay UVWOC links in both weak and strong underwater turbulence conditions. The analysis accounts for attenuation losses and pointing errors. Monte-Carlo simulations validate the accuracy of the derived expressions. Furthermore, Bose-Chaudhuri-Hocquenghem (BCH) codes with parameters (n=31, k=11) and (n=63, k=18) are applied to enhance the integrity of information transfer over the AF/DF relay UVWOC link. This research contributes to understanding UVWOC links under diverse conditions and proposes coding techniques for improved reliability in challenging underwater environments. © 2013 IEEE.
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.
Performance analysis of underwater vertical wireless optical communication links using selection combining
(Optica Publishing Group (formerly OSA), 2023) Savidhan Shetty, S.C.S.; Naik, R.P.; Shripathi Acharya, U.S.
In this paper, we have investigated the performance of underwater vertical wireless optical communication (UVWOC) links employing on–off key modulation for selection combining based receive diversity schemes in the presence of underwater turbulence, pointing errors, and attenuation losses. Due to variations in temperature and salinity along the ocean’s depth, turbulence-induced fading affects the performance of the underwater vertical wireless optical link. The vertical link of the underwater medium influenced by a strong turbulence regime is modeled using cascaded gamma–gamma distribution considering multiple non-identical layers along with attenuation losses and pointing errors. We have derived closed-form expressions for the average bit error rate (BER) and outage probability (OP) for the link employing multiple detectors at the receiving end. The accuracy of all of the closed-form expressions derived in this paper has been validated using Monte Carlo simulations. © 2023 Optica Publishing Group.
Performance analysis of underwater vertical wireless optical communication system in the presence of weak turbulence, pointing errors and attenuation losses
(Springer, 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 underwater vertical wireless optical communication (UVWOC) link employing on–off key modulation in the presence of underwater turbulence, pointing errors and attenuation losses. The turbulence of the medium (assumed to be weak turbulence) has been modeled by employing the hyperbolic tangent log normal (HTLN) distribution. Temperature, pressure and salinity are parameters which can bring about variation of optical transmission characteristics with respect to depth of the ocean/sea. An in-depth study of optical transmission through vertical oceanic links requires the the underwater medium to be modeled as comprising of non-identical turbulent layers. Each of these independent and non-identical turbulence layers are modeled using the HTLN distribution function. The pointing error due to misalignment between source and detector is modeled using Rayleigh displacement pointing error. A novel closed-form expression to quantify the average bit error rate (BER) has been derived for single input single output (SISO) communication link. This expression has then been further generalized to make it applicable to the case of receive diversity schemes such as selection combining, majority logic combining and maximum ratio combining. The expression for the average BER associated with the UVWOC link for different pointing errors, different data rates and different types of ocean water has been determined. Novel closed-form expressions quantifying the outage probability and ergodic channel capacity have been derived for SISO and SC receive diversity schemes. The accuracy of all of the closed-form expressions derived in this paper have been validated using Monte-Carlo simulations. © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.