Sudipta Mahapatra

Efficient FPGA implementation of DWT and modified SPIHT for lossless image compression

In this paper, we present an implementation of the image compression technique set partitioning in hierarchical trees (SPIHT) in programmable hardware. The lifting based Discrete Wavelet Transform (DWT) architecture has been selected for exploiting the correlation among the image pixels. In addition, we provide a study on what storage elements are required for the wavelet coefficients. A modified SPIHT (Set Partitioning in Hierarchical Trees) algorithm is presented for encoding the wavelet coefficients. The modifications include a simplification of coefficient scanning process, use of a 1-D addressing method instead of the original 2-D arrangement for wavelet coefficients and a fixed memory allocation for the data lists instead of the dynamic allocation required in the original SPIHT. The proposed algorithm has been illustrated on both the 2-D Lena image and a 3-D MRI data set and is found to achieve appreciable compression with a high peak-signal-to-noise ratio (PSNR).

QoS-aware fuzzy rule-based vertical handoff decision algorithm incorporating a new evaluation model for wireless heterogeneous networks

AbstractNext generation networks are envisioned to be heterogeneous in nature with an increase in demand towards ubiquitous services in wireless networks. As various networks have widely different characteristics, it is difficult to maintain the quality of service (QoS) after executing a handoff from one network to another network. Maintaining the QoS, based on applications, during the handoff in an heterogeneous networks needs an intelligent handoff decision mechanism. This article proposes a QoS-aware fuzzy rule-based vertical handoff mechanism that makes a multi-criteria-based decision, found to be effective for meeting the requirements of different applications in a heterogeneous networking environment. The QoS parameters considered are available bandwidth, end-to-end delay, jitter, and bit error rate. A new evaluation model is proposed using a non-birth–death Markov chain, in which the states correspond to the available networks. Simulation results show that compared to other vertical handoff algorithms, the proposed algorithm gives better performance for different traffic classes.

QoS aware fuzzy rule based vertical handoff decision algorithm for wireless heterogeneous networks

Increasing demands of ubiquitous services in wireless networks and evolution towards heterogeneous solutions has driven the necessity of developing efficient QoS aware vertical handoff (handoff between different networks) mechanisms. This paper proposes a QoS aware fuzzy rule based vertical handoff mechanism that makes a multi-criteria based decision, found to be effective for meeting the requirements of different applications. The QoS parameters considered are available bandwidth, end-to-end delay, jitter, and bit error rate (BER). A new evaluation model is proposed using a non birth-death Markov chain, in which the states correspond to the available networks. Simulation results show that compared to other vertical handoff algorithms, the proposed algorithm gives better performance for different traffic classes.

Capillary optical fibers: design and applications for attaining a large effective mode area

We study the application of capillary optical fibers to attain a large effective mode area for nonlinearity suppression in high-power lasers and amplifiers. The effect of the inclusion of an air capillary on the modal properties of a conventional optical fiber, such as the effective index of the guided modes, is calculated using fully vectorial analytical techniques and verified using the finite element method. It is illustrated that our design transcends the recently predicted limit on the effective mode area obtainable in conventional optical fibers at 1064 nm. The influence of bending on the mode area is investigated in detail. We further propose alternative designs, such as the depressed-clad capillary optical fiber and the trench-assisted capillary optical fiber, and we carry out simulations to show how they can be used to reduce losses in optical fibers. The variation of the fractional power contained within the capillary is calculated to determine the effect on nonlinearity suppression. We also show that by including a nanosized air capillary in the core of a photonic crystal fiber, the effective mode area can be further enhanced even in bent conditions.

Energy and quality of service aware FUZZY-technique for order preference by similarity to ideal solution based vertical handover decision algorithm for heterogeneous wireless networks

Next generation networks will use multiple transport technologies that offer unrestricted user access to different service providers and support generalised mobility to allow consistent and ubiquitous service provisioning to users. Different networks have widely varying characteristics, which makes it difficult to maintain the requested quality of service (QoS) after executing handoff from one transport technology to another. Maintaining the QoS during handoff in heterogeneous networks needs an intelligent decision mechanism. Moreover, the developed algorithms should be energy aware as the devices involved rely on battery power. This study proposes a novel vertical handover decision mechanism namely FUZZY-technique for order preference by similarity to ideal solution (FUZZY-TOP), obtained by combining a fuzzy rule-based mechanism with the technique for order preference by similarity to ideal solution approach. Simulation results based on a generalised Markov chain show that compared with existing vertical handover decision algorithms, the proposed FUZZY-TOP decision algorithm performs better for different traffic classes.

FWM aware evolutionary programming algorithm for transparent optical networks

This paper proposes and evaluates a four-wave mixing (FWM) aware evolutionary programming algorithm for dynamically setting up lightpaths in an optical wavelength division multiplexed network (WDM network). The proposed algorithm also considers the effect of amplified spontaneous emission noise (ASE noise) on a lightpath during propagation of the optical signal from any source to the intended destination. As crosstalk due to FWM and ASE noise are two transmission impairments that degrade the quality of optical signal even at low to medium data rates, it is mandatory for an algorithm for dynamic routing and wavelength assignment in a WDM network to consider the effect of these two impairments on the lightpath to be established. The distinguishing feature of the proposed algorithm is that it is based on an initial population of a single individual and uses a fitness function that is expressed in terms of the number of hops, path cost, variance contributions due to FWM crosstalk, amplifier noise, and different beat noises at the receiver. The performance of a newly introduced FWM aware priority-based wavelength assignment technique is compared with few of the existing wavelength assignment techniques in the present work.

Design and Evaluation of a Failure Detection Algorithm for Large Scale Ad Hoc Networks Using Cluster Based Approach

In this paper we propose a scalable failure detection service for large scale ad hoc networks using an efficient cluster based communication architecture. Our failure detection service adapts the detection parameter to the current load of the wireless ad hoc network. The proposed approach uses a heartbeat based testing mechanism to detect failure in each cluster and take the advantage of cluster based architecture to forward the failure report to other cluster and their respective members. The simulation results show that this approach is linearly scalable in terms of message complexity and consensus time.

A parallel formulation of back-propagation learning on distributed memory multiprocessors

Abstract This paper presents a mapping scheme for parallel pipelined execution of the Back-propagation Learning Algorithm on distributed memory multiprocessors. The proposed implementation exhibits inter-layer or pipelined parallelism, unique to the multilayer neural networks. Simple algorithms have been presented, which allow the data transfer involved in both recall and learning phases of the back-propagation algorithm to be carried out with a small communication overhead. The effectiveness of the mapping scheme has been illustrated, by estimating the speedup of the proposed implementation on an array of T-805 transputers.

An evolutionary programming algorithm for survivable routing and wavelength assignment in transparent optical networks

The dynamic routing and wavelength assignment (DRWA) problem is a challenging optimisation problem in optical wavelength division multiplexed (WDM) networks. This paper proposes a novel evolutionary programming algorithm, namely, ERWA, to reduce the set-up time of lightpaths in a WDM network. It is shown that the proposed algorithm with simple extensions, referred to in this paper as ESRWA, is able to provide dedicated protection at the optical layer of the network, thereby addressing the survivable DRWA problem. In contrast to other bio-inspired algorithms available in the literature for the DRWA problem, ERWA facilitates the online discovery of a requested lightpath. The novelty of ERWA lies in the fact that it uses an initial population consisting of only one individual or chromosome and integrates a soft constraint with a set of hard constraints to accomplish proper load balancing. These features result in a lower mean blocking probability and a lower mean execution time compared to those exhibited by the existing bio-inspired algorithms for both the DRWA and the survivable DRWA problems.

Mapping of Neural Network Models onto Systolic Arrays

This paper presents a mapping scheme for the proposed implementation of neural network models on systolic arrays. The mapping technique is illustrated on the multilayer perceptron with back-propagation learning. Dependency graphs have been given that represent the operations in the execution phases of the neural network model and later suitable algorithms are presented to realize the operations in a linear bidirectional systolic array. The speedup metric has been used to evaluate the performance of the proposed implementation.