Faculty Publications

Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736

Publications by NITK Faculty

Browse

Author: search.filters.author.Shripathi Acharya, U.S.

Search Results

Now showing 1 - 10 of 25
  • No Thumbnail Available
    Item
    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]
  • No Thumbnail Available
    Item
    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. © 2015 SPIE.
  • No Thumbnail Available
    Item
    Performance of Alamouti space time codes in an optical uplink channel
    (Institute of Electrical and Electronics Engineers Inc., 2015) Ravula, H.; Shripathi Acharya, U.S.
    The optical uplink, ground station to satellite, is more susceptible to signal fading compared to the downlink channel due to beam wandering experienced at the transmitter in the ground station. Alamouti space time codes have been used to partially mitigate this handicap. With the use of these codes, a bit error rate(BER) of 1 × 10-8 can be achieved for a link margin of 6dB. A transmitter beam radius of 47cm and a receiver diameter of 1m are noted to be suitable for the uplink optical system with transmitter at an altitude of 2.5km from the ground and the satellite at a zenith angle of 0°. The performance of the Alamouti codes is simulated in MATLAB 2006b and analyzed for one, two and four receivers and the use of 2 × 2 is proposed in this work, since the deployment of four receivers at the satellite does not seem practical. It is demonstrated that a 2×2 Alamouti space time code achieves a total gain of 6dB when convolutional coding and QPSK modulation are used whereas a gain of about 5dB is achieved by using 8PSK or 16QAM. Link Budget analysis of the uplink scenario suggests that the proposed method reduces the required transmitter power from 24.883kW to 6.2207kW. © 2015 IEEE.
  • No Thumbnail Available
    Item
    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. © 2015 IEEE.
  • No Thumbnail Available
    Item
    Study of 2D localization using SIMO antenna
    (Institute of Electrical and Electronics Engineers Inc., 2016) Laddha, P.; Prasad, R.; Shripathi Acharya, U.S.; Srihari, P.; Prasad, S.; Rao, P.H.
    A single input and multiple output (SIMO) antenna configuration is presented for real time data acquisition. The proposed approach can provide both range and angle information in a plane. A method of localization of multiple point objects (targets) in azimuthal plane is realized by employing one stationary transmitting antenna and dynamic receiving antennas positions. FMCW chirp signals are used as transmitting signals. A parametric analysis is carried out by varying the bandwidth of transmitted signal, number of samples and number of antennas on a linear array with equal inter-element spacing. Radial resolution of 0.4 feet and 0.23 feet is achieved for 2GHz and 6 GHz bandwidths respectively. The method is extended to identify multiple targets. © 2016 IEEE.
  • No Thumbnail Available
    Item
    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. © 2017 IEEE.
  • No Thumbnail Available
    Item
    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. © 2017 IEEE.
  • No Thumbnail Available
    Item
    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. © 2018 IEEE.
  • No Thumbnail Available
    Item
    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 ∼ 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. © 2019 IEEE.
  • No Thumbnail Available
    Item
    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. © 2021 IEEE.