M. Sathish Kumar

Transmission and storage of medical images with patient information

Digital watermarking is a technique of hiding specific identification data for copyright authentication. This technique is adapted here for interleaving patient information with medical images, to reduce storage and transmission overheads. The text data is encrypted before interleaving with images to ensure greater security. The graphical signals are interleaved with the image. Two types of error control-coding techniques are proposed to enhance reliability of transmission and storage of medical images interleaved with patient information. Transmission and storage scenarios are simulated with and without error control coding and a qualitative as well as quantitative interpretation of the reliability enhancement resulting from the use of various commonly used error control codes such as repetitive, and (7,4) Hamming code is provided.

Torus Embedded Hypercube Interconnection Network: A Comparative Study

analysis and comparison of a product network generated from torus and hypercube networks known as torus embedded hypercube scalable interconnection network suitable for parallel computers is presented in this paper. It is shown here that with minor modifications in architecture of the existing mesh embedded hypercube interconnection network how good a torus embedded hypercube interconnection network could be. Also it has been proved with the computational results that the torus embedded hypercube interconnection network is highly scalable and more efficient in terms of communication.

Full length article: Performance evaluation of random linear network coding using a Vandermonde matrix

This paper discusses random linear network coding with and without the use of a Vandermonde matrix to obtain the coding coefficients. Performance comparisons of such random linear network coded networks with networks employing traditional store and forward technique are also provided. It is shown that random linear network coding using a Vandermonde matrix can improve the network utilization factor by reducing the overhead compared to random linear coding that does not use a Vandermonde matrix. Our numerical results show that random linear network coding with a Vandermonde matrix provides a considerable improvement in throughput and delay when compared to a network employing a traditional store and forward strategy. An inherent feature of random linear network coding which makes it possible to employ simple encryption techniques is also discussed.

A Comparative Study of Various Meta-Heuristic Algorithms for Ab Initio Protein Structure Prediction on 2D Hydrophobic-Polar Model

Ab initio protein structure prediction (PSP) models tertiary structures of proteins from its sequence. This is one of the most important and challenging problems in bioinformatics. In the last five decades, many algorithmic approaches have been made to solve the PSP problem. However, it remains unsolvable even for proteins of short sequence. In this review, the reported performances of various meta-heuristic algorithms were compared. Two of the algorithmic settings—protein representation and initialization functions were found to have definite positive influence on the running time and quality of structure. The hybrid of local search and genetic algorithm is recognized to be the best based on the performance. This work provides a chronicle brief on evolution of alternate attempts to solve the PSP problem, and subsequently discusses the merits and demerits of various meta-heuristic approaches to solve the PSP problem.

PAPR and out-of-band power reduction in OFDM-based cognitive radios

One of the interesting features of cognitive radio (CR) systems is their ability to provide dynamic spectrum access even in the licensed spectral bands; wherein they should be strictly causing no interference to the licensed users or among themselves. Orthogonal frequency-division multiplexing (OFDM) is considered for CR user transmission because of its flexible operation in frequency band switching; but suffers from high peak-to-average power ratio (PAPR). Hence, a transmission method where it can cause minimum interference with lower PAPR is obtained. In this paper, a better method to reduce out-of-band (OOB) power as well as PAPR is modeled by combining spectral precoding which aims at OOB radiation suppression; and PAPR reduction techniques such as selected mapping (SLM) technique and iterative clipping and filtering (ICF). The performance of these methods are discussed in terms of power spectral densities (PSD) and complementary cumulative distribution function (CCDF) of PAPR.

A generalized closed form relation for BER of QPSK/M-QAM over fading channel

The analytical computation of average bit error probability over fading channel is very difficult if the probability of bit error over an AWGN involves square of Gaussian Q function or error function. In this paper curve fitting technique has been applied to represent bit error probability of any digital modulation technique in terms of a simple Gaussian function. Using this approximated function, a generalized closed form relation for computing average probability of error over fading channel has been obtained.

Coding to Enhance Performance of Hybrid Multiplexed Coherent Optical Communication Systems in the Presence of ICI and SRS

Long haul, repeaterless, coherent optical multichannel communication systems employing hybrid multiplexing schemes wherein Wavelength Division Multiplexing (WDM) and Optical Code Division Multiplexing (OCDM) are combined is analyzed in the presence of performance limiting factors such as Inter Channel Interference (ICI), Stimulated Raman Scattering (SRS) and detector shot noise. Error control coding techniques in the form of rate 1/2 convolutional codes are employed in the system to counter these performance limiting factors. It is seen that the use of error control coding technique can enhance the system performance to such an extent that a Bit Error Rate (BER) performance of less than 10 -8 is achievable without crossing the SRS power threshold for as many as 1000 to 1200 channels. Advantages of the hybrid multiplexed system over systems relying solely on WDM or OCDM are also discussed along with the advantages of using error control coding compared to optical amplification in countering the performance degrading factors.

Plasmonic Wavelength Demultiplexer with Mode Conversion Capabilities

An efficient wavelength demultiplexer with its input as a metal-insulator-metal (MIM) waveguide mode and output an out of plane free-space mode is proposed. The proposed demultiplexer design is integrated on a MIM waveguide such that power is evanescently coupled into an array of appropriately designed cavity-groove combination. The demultiplexer design permits control of phase of the dropped wavelength to achieve a desired wavefront. We demonstrate this through generation of circular and plane wavefront. By controlling the evanescently coupled power into the cavity-groove combinations, it is possible to dramatically improve the efficiency of the proposed demultiplexer. Results are simulated using FEM technique.

A Novel Framework for Ab Initio Coarse Protein Structure Prediction

Hydrophobic-Polar model is a simplified representation of Protein Structure Prediction (PSP) problem. However, even with the HP model, the PSP problem remains NP-complete. This work proposes a systematic and problem specific design for operators of the evolutionary program which hybrids with local search hill climbing, to efficiently explore the search space of PSP and thereby obtain an optimum conformation. The proposed algorithm achieves this by incorporating the following novel features: (i) new initialization method which generates only valid individuals with (rather than random) better fitness values; (ii) use of probability-based selection operators that limit the local convergence; (iii) use of secondary structure based mutation operator that makes the structure more closely to the laboratory determined structure; and (iv) incorporating all the above-mentioned features developed a complete two-tier framework. The developed framework builds the protein conformation on the square and triangular lattice. The test has been performed using benchmark sequences, and a comparative evaluation is done with various state-of-the-art algorithms. Moreover, in addition to hypothetical test sequences, we have tested protein sequences deposited in protein database repository. It has been observed that the proposed framework has shown superior performance regarding accuracy (fitness value) and speed (number of generations needed to attain the final conformation). The concepts used to enhance the performance are generic and can be used with any other population-based search algorithm such as genetic algorithm, ant colony optimization, and immune algorithm.

NS-2 extension for interface assignment in AODV routing protocol

Network Simulator(NS-2) is an open source discrete event simulator, widely used by the networking research community. NS-2 provides flexibility for the researcher to extend the simulator functionality for any new area of research in networks. The primary objective of the paper is to investigate the development and simulation of the interface assignment in multi-interface multi-channel wireless adhoc network in NS-2. Accordingly, existing ad hoc on-demand distance vector(AODV) routing protocol which was designed for single interface single channel (S-AODV) was studied and modified to support multi-interface multi-channel (M-AODV)configuration. Simulation results show better performance of M-AODV over S-AODV.