Faculty Publications
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Publications by NITK Faculty
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Item Super resolution of video with sharpened edges using multiple frames - A novel approach(2009) Pais, A.R.; D'Souza, J.; Guddeti, G.R.M.; Patil, S.B.In most electronic video applications, video with Higher Resolution(HR) are often required. HR video can offer more details that may be critical in various applications like Video Surveillance. Super resolution technique refers to generation of high resolution image from low resolution image by adding some extra information. Super resolution allows us to reduce the need of extra hardware to obtain HR image. This paper proposes a new method for super resolution video generation with sharpened edges using multiple frames. Unique information present in subpixel shifted frames is extracted and used for frequency domain registration process. © 2009 IEEE.Item Automatic video object plane segmentation and super resolution: A novel approach(2009) Pais, A.R.; Pasupuleti, N.; Gidnavar, R.; D'Souza, J.Detecting, segmenting and super resolving of moving object is an important subject in computer visual analysis and surveillance. This paper discusses automatic VOP (Video Object Plane) segmentation and super resolving of VOP. We have proposed a new method for automatic generation of VOP by using block matching and quantization techniques. Edge model based approach is used to generate the HR (High Resolution) image with sharper VOP boundaries. Experimental results show that the proper VOP is segmented and super resolution of VOP yields lesser blurring compared to bicubic, bilinear interpolation schemes. Copyright © 2009 by IICAI.Item Performance of spatially coupled LDPC codes over underwater acoustic communication channel(Institute of Electrical and Electronics Engineers Inc., 2020) Padala, S.K.; D'Souza, J.Underwater acoustic (UWA) channel is complex because of its multipath environment, Doppler shift and rapidly changing characteristics. Many of the UWA communication- based applications demand high data rates and reliable communication. The orthogonal frequency division multiplexing (OFDM) system is very effective in UWA channels and provides high data rate with low equalization complexity. It is a challenging task to achieve reliability over these channels. The low-density parity-check (LDPC) codes give a better error performance than turbo codes, for UWA channels. The spatially-coupled low-density parity-check (SC-LDPC) codes have been shown to have the capacity-achieving performance over terrestrial communication. In this paper, we have studied by simulation, the performance of protograph based SC-LDPC codes over shallow water acoustic environment with a communication range of 1000 m and channel bandwidth of 10 KHz. Our results show that SC-LDPC codes give 1 dB performance improvement over LDPC codes at a Bit Error Rate (BER) of 10-3 for the same latency constraints. © 2020 IEEE.Item Nonlinear Frequency Modulated Waveform Optimization for a Cooperative Radar-Communication System(Institute of Electrical and Electronics Engineers Inc., 2021) Mahipathi, A.C.; Gunnery, S.; Srihari, P.; D'Souza, J.; Jena, P.Co-existence research related to radar and communication systems has gained significant interest in the last decade to address the spectrum scarcity issues. Designing an optimal waveform for a Joint Radar-Communication (JRC) system is an important consideration to practically realize the convergence of these two subsystems. This paper proposes a Power Ratio Constraint (PRC) based optimization technique to evaluate phase coefficients of Non Linear Frequency Modulated (NLFM) waveform for a Cooperative Radar-Communication System (CRCS). The radar waveform is optimized here using the Cramér-Rao Lower Bound (CRLB) metric in conjunction with the PRC. We investigated the spectral energy distribution, auto correlation function, and estimation rate for radar systems using optimized NLFM waveform phase coefficients. In addition, data rate for communication system is computed. Further, the simulation results shows that, proposed joint PRC-CRLB based optimization method confines the radar spectrum, reduces the delay ambiguities and enhances the information rate of CRCS. © 2021 IEEE.Item LPI-Based NLFM Radar Waveform Design for a Cooperative Radar-Communication System(Institute of Electrical and Electronics Engineers Inc., 2023) Mahipathi, A.C.; Pardhasaradhi, B.; Srihari, P.; D'Souza, J.; Jena, P.This paper studies the Low Probability of Intercept (LPI) based Non-Linear Frequency Modulated (NLFM) radar waveform design approach in a Cooperative Radar-Communication System (CRCS). The crux of the LPI-based radar waveform design approach is to employ optimization methods to design the transmitted radar waveform for achieving the LPI characteristics by upholding the target detection characteristics. Here, the optimization problem is formulated subject to the Power Constraint (PC) (responsible for LPI characteristics) and Similarity Constraint (SC) (responsible for target detection) to guarantee a satisfactory performance in a CRCS. In addition, the simulation results exhibit that the proposed LPI-based NLFM radar waveform design approach provides desired characteristics needed to maintain the LPI and target detection performance in a CRCS. © 2023 IEEE.Item This letter presents techniques for improving the distribution of the number of stack entries, for stack sequential decoding over hard quantized channel, with emphasis on high rate codes. It is shown that, for a class of high rate b/(b+1) codes, a table-based true high rate approach can be easily implemented for obtaining decoding advantage over the punctured approach. Modified algorithms, which significantly improve the distribution of the number of stack entries and decoding time, are proposed for rate 1/N codes and high rate b/(b+1) codes.(IEEE, On low complexity stack decoding of convolutional codes) D'Souza, J.; Maskara, S.L.1999Item Automatic shadow removal algorithm for VOP, DWT based watermarking algorithm for VOP and generation of super resolved VOP(2011) Pais, A.R.; D'Souza, J.; Reddy, R.M.; Hari Krishna, P.Removal of shadow from Video Object Planes (VOPs) will assist in surveillance applications for comprehensive detection of activities. We have proposed a method for removal of shadows from the VOP. Also noise removal is done using existing methods from the VOP. To authenticate the surveillance VOP, digital watermarking is used. We have proposed digital watermarking using localized Biorthogonal wavelets for VOP. Super-resolved VOP is generated using multi-frame method. Edge model based super resolution method is used to get the better results. Also the effect of digital watermarking is studied for the super-resolved VOP. A number of test cases have been proposed and found out a best method for video surveillance application. Our proposed super resolution (SR) method gives better results than bilinear and bi-cubic methods.Item Super-resolution video generation algorithm for surveillance applications(Maney Publishing Suite 1C, Joseph's Well, Hanover Walk Leeds LS3 1AB, 2014) Pais, A.R.; D'Souza, J.; Reddy, R.M.Video surveillance is one of the major applications where high-resolution (HR) images are crucial. Since the video camera has limited spatial and temporal resolution, there is a need for super resolution video generation algorithms. In this paper, we have presented a novel technique for activity detection in the surveillance video. To achieve this goal, we have proposed and investigated efficient algorithms for Video Object Plane (VOP) generation, shadow removal from VOP and super-resolved VOP generation, for activity detection from surveillance video. The proposed VOP generation algorithm is computationally efficient and works for both dynamic and static backgrounds. The novel shadow removal algorithm for the VOP is based on texture and its performance has been studied based on average shadow detection and discrimination rates. The proposed super-resolution video generation algorithm has been designed using edge models. The performance of this algorithm has been evaluated using a numerical analysis technique and is found to be better than bi-cubic and bi-linear interpolation techniques. © 2014 RPS.Item Optimised microwave-assisted biosynthesis of silver nanoparticles from Nothapodytes foetida leaf extracts and its anti-microbial activities(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2016) Roopesh, R.; Geedhika, G.; D'Souza, J.; Anandhan, S.; Bhat, K.U.; Jaya M, J.; Fathima B, S.; Mohan Balakrishnan, R.M.The present investigation reports the biogenesis of silver nanoparticles (Ag NPs) using extracts of a medicinal plant Nothapodytes foetida. Total phenolic content (TPC) and ferric reducing antioxidant power (FRAP) assay were carried out for the microwave-assisted extract (MAE) of N. foetida using methanol as solvent and the conditions for extraction were optimised by response surface methodology (RSM). The effects of operating variables such as extraction time, temperature and ratio of sample to solvent were studied using central composite design (CCD). A mathematical model with a high determination coefficient (R2) for TPC (0.991) and FRAP (0.995) was obtained. The optimal conditions of extraction for TPC were 48.6 ºC, 23.15 min and 2.04:30 (g/mL) and for FRAP 52.31ºC, 12.32 min and 1.67: 30 (g/mL). Under these conditions, the experimental yields of TPC and FRAP were 2.426 mg gallic acid equivalents (GAE)/g dry powder and 14.985mg of FeSO4·7H2O/g of dry powder, respectively. Ag NPs were characterised using UV–Vis spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The synthesised Ag NPs have also shown potent activity against the human pathogenic Staphylococcus aureus. © 2016 Informa UK Limited, trading as Taylor & Francis Group.Item Constrained radar waveform optimization for a cooperative radar-communication system(Elsevier B.V., 2023) Mahipathi, A.C.; Gunnery, S.; Srihari, P.; D'Souza, J.; Jena, P.The coexistence of radar-sensing and communication systems research has received a surge of interest in recent times to tackle the issue of spectrum inadequacy. Designing an optimized radar waveform for a coexistence scenario has been a challenging task for accomplishing the convergence of radar-sensing and communication functionalities, without degrading the performance at either end. This paper proposes a novel global optimization-based Spatial Branch and Bound (SBnB) approach to optimize the phase coefficients of a Non-Linear Frequency Modulated (NLFM) waveform in a CRCS framework. In addition, the Modified-Power Ratio Constraint-Cramér–Rao Lower Bound (M-PRC-CRLB), a local optimization-based approach is proposed to optimize the phase coefficients of an NLFM waveform. The spectral energy distribution and auto-correlation characteristics of an NLFM waveform are comprehensively investigated for various values of polynomial order (N) and at different threshold Signal-to-Noise-Ratio (SNR) values. To compare the proposed waveform design approaches (M-PRC-CRLB, SBnB) with the existing waveform design approaches namely, Minimum Estimation Error Variance (MEEV) and PRC- CRLB, a Peak-to-Side-Lobe-Ratio (PSLR), and Integrated-Side-Lobe-Ratio (ISLR) are evaluated at various polynomial orders and threshold SNR values. Furthermore, the performance of a CRCS is assessed using the radar estimation rate and communication data rate. The simulation results reveal that the proposed optimized radar waveform design approaches provide improved performance compared to the existing radar waveform design approaches in terms of radar estimation rate. Further, the proposed global optimization-based SBnB approach achieves a comparable performance of the communication data rate. In addition, the proposed approaches accomplish enhanced spectral utilization, controlled side-lobe energy levels, reduced range-domain ambiguities, and a higher information rate in a CRCS. © 2022 Elsevier B.V.