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2008| November-December | Volume 25 | Issue 6
February 10, 2009
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Visible Light Communication Systems Conception and VIDAS
Navin Kumar, Nuno Lourenco, Michal Spiez, Rui L Aguiar
November-December 2008, 25(6):359-367
Visible Light Communication (VLC) using LEDs is emerging as a key technology for a ubiquitous communication system, because LED has the advantages of fast switching, long life expectancy, being less expensive and being visible light that is safe for the human body. The VLC system is expected to undergo rapid progress, inspiring numerous indoor and outdoor applications; however, many technical issues need to be addressed, especially in outdoor environment. In order to provide a better understanding of the research challenges of VLC, this article presents a detailed investigation of the current state-of-art concept. Open research issues such as channel modelling and modulation techniques are also discussed, with the objective of triggering new research interest in this field. The paper also introduces our ongoing development of Wireless USB Interface and the project VIDAS.
MIMO Channel Modeling: A Review
Babu Sena Paul, Ratnajit Bhattacharjee
November-December 2008, 25(6):315-319
Channel modeling plays an important role in understanding the behavior and designing of communication systems for different environments. In this paper, we make a brief review of the different channel modeling techniques used to model a multiple-input-multiple-output (MIMO) wireless channel.
A Review of Independent Component Analysis Techniques and their Applications
DP Acharya, G Panda
November-December 2008, 25(6):320-332
Independent Component Analysis, a computationally efficient blind statistical signal processing technique, has been an area of interest for researchers for many practical applications in various fields of science and engineering. The present paper attempts to treat the fundamental concepts involved in the independent component analysis (ICA) technique and reviews different ICA algorithms. A thorough discussion of the algorithms with their merits and weaknesses has been carried out. Applications of the ICA algorithms in different fields of science and technology have been reviewed. The limitations and ambiguities of the ICA techniques developed so far have also been outlined. Though several articles have reviewed the ICA techniques in literature, they suffer from the limitation of not being comprehensive to a first time reader or not incorporating the latest available algorithm and their applications. In this work, we present different ICA algorithms from their basics to their potential applications to serve as a comprehensive single source for an inquisitive researcher to carry out his work in this field.
A Cross-layer QoS Mapping Framework for Mobile Ad Hoc Networks
Nityananda Sarma, Sukumar Nandi
November-December 2008, 25(6):346-358
Research in Quality of Service (QoS) provisioning for wireless ad hoc networks is receiving growing interest due to the rising necessity for supporting multimedia applications in such networks. Quality of Service provisioning is a multilayer problem, where the interaction between protocols at different layers is of paramount importance. In this paper, we are looking at the problem of QoS provisioning from the perspective of three layers - application layer, network layer and medium access control (MAC) layer. Our goal is to design a QoS framework which maps QoS parameters across these three layers of the protocol stack, to support a stronger notion of per-class service guarantees in terms of throughput and delay in ad hoc networks. Further, to cope with network dynamics, MAC layer and network layer are made to adapt their behavior based on both dynamic network conditions and QoS requirements of admitted flows. An MAC layer adaptation takes place in terms of dynamic contention window adjustment per class, whereas a network layer adaptation takes place in the form of rerouting or termination of existing flows. We have proposed a detailed QoS mapping scheme with adaptive protocols, using a TCP/IP protocol suite.
Floating-gate MOS Structures and Applications
Susheel Sharma, SS Rajput, SS Jamuar
November-December 2008, 25(6):338-345
Floating-gate MOS transistor (FGMOS) has proved to be suitable for low-voltage analog applications, owing to its threshold voltage programmability. This tutorial paper presents FGMOS based circuit structures and their applications in analog signal processing. The FGMOS based current mirror and its application as voltage controlled current source has been presented. The performance of these structures has been verified using PSpice simulations for 0.5 µm CMOS technology at ±0.75 V.
Transition to Online System and Thoughts on Peer Review Process
M Jagadesh Kumar
November-December 2008, 25(6):309-310
A Gray-level Value Logarithm Ratio Neighborhood Filters Method for Image Denoising
Chen Guan-nan, Chen Rong, Yang Kun-tao, Chen Jian-xin, Huang Zu-fang, Xie Zhi-ming
November-December 2008, 25(6):333-337
Neighborhood filters are modern and powerful techniques for image denoising. In this paper, we perform an analysis for the normalization Factor of Neighborhood filters, where the size of the gray Euclidean distance is small. We prove that the weak edges and details are smoothed, and the gray level transition tends to become mild, when filtering with these Neighborhood filters. As a solution, a new gray-level value logarithm ratio range filter kernel is pointed out for the normalization Factor of Bilateral filter, a representative method of Neighborhood filters. The new gray-level value logarithm ratio Neighborhood filters method can not only restrain noise well but also keep much more weak edges and details of images, and preserve the original gray level or color transition for gray images or color images.
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November-December 2008, 25(6):368-368
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