No. 4 (2010)
Published:
2010-12-30
ARTICLES FROM THIS ISSUE
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Robust and Accurate Iris Segmentation Algorithm for Color and Noisy Eye Images
Abstract
Efficient and robust segmentation of iris images captured in the uncontrolled environments is one of the challenges of non-cooperative iris recognition systems. We address this problem by proposing a novel iris segmentation algorithm, which is suitable both for monochrome and color eye images. The method presented use modified Hough transform to roughly localize the possible iris and pupil boundaries, approximating them by circles. A voting mechanisms is applied to select a candidate iris regions. The detailed iris boundary is approximated by the spline curve. Its shape is determined by minimizing introduced boundary energy function. The described algorithm was submitted to the NICE.I iris image segmentation contest, when it was ranked 11th and 10th out of total 97.
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Iris Recognition System Based on Zak-Gabor Wavelet Packets
Abstract
The paper proposes a new iris coding method based on Zak-Gabor wavelet packet transform. The essential component of the iris recognition methodology design is an effective adaptation of the transformation parameters that makes the coding sensitive to the frequencies characterizing ones eye. We thus propose to calculate the between-to-within class ratio of weakly correlated Zak-Gabor transformation coefficients allowing for selection the frequencies the most suitable for iris recognition. The Zak-Gabor-based coding is non-reversible, i.e., it is impossible to reconstruct the original iris image given the iris template. Additionally, the inference about the iris image properties from the Zak-Gabor-based code is limited, providing a possibility to embed the biometric replay attack prevention methodology into the coding. We present the final prototype system design, including the hardware, and evaluate its performance using the database of 720 iris images.
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Image Preprocessing for Illumination Invariant Face Verification
Abstract
Performance of the face verification system depend on many conditions. One of the most problematic is varying illumination condition. In this paper 14 normalization algorithms based on histogram normalization, illumination properties and the human perception theory were compared using 3 verification methods. The results obtained from the experiments showed that the illumination preprocessing methods significantly improves the verification rate and it’s a very important step in face verification system.
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Face Tracking and Recognition with the Use of Particle-Filtered Local Features
Abstract
A consistent particle filtering-based framework for the purpose of parallel face tracking and recognition from video sequences is proposed. A novel approach to defining randomized, particle filtering-driven local face features for the purpose of recognition is proposed. The potential of cumulating classification decisions based on the proposed feature set definition is evaluated. By applying cumulation mechanisms to the classification results determined from single frames and with the use of particle-filtered features, good recognition rates are obtained at the minimal computational cost. The proposed framework can operate in real-time on a typical modern PC. Additionally, the application of cumulation mechanisms makes the framework resistant to brief visual distortions, such as occlusions, head rotations or face expressions. A high performance is also obtained on low resolution images (video frames). Since the framework is based on the particle filtering principle, it is easily tunable to various application requirements (security level, hardware constraints).
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Rule Based Speech Signal Segmentation
Abstract
This paper presents the automated speech signal segmentation problem. Segmentation algorithms based on energetic threshold showed good results only in noise-free environments. With higher noise level automatic threshold calculation becomes complicated task. Rule based postprocessing of segments can give more stable results. Off-line, on-line and extrema types of rules are reviewed. An extrema-type segmentation algorithm is proposed. This algorithm is enhanced by a rule base to extract higher energy level segments from noise. This algorithm can work well with energy like features. The experiments were made to compare threshold and rule-based segmentation in different noise types. Also was tested if multifeature segmentation can improve segmentation results. The extrema rule-based segmentation showed smaller error ratio in different noise types and levels. Proposed algorithm does not require high calculation resources. Such algorithm can be processed by devices with limited computing power.
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Speech Segmentation Algorithm Based on an Analysis of the Normalized Power Spectral Density
Abstract
This article demonstrates a new approach to speaker independent phoneme detection. The core of the algorithm is to measure the distance between normalized power spectral densities in adjacent, short-time segments and verify it based on velocity of changes of values of short-time signal energy analysis. The results of experiment analysis indicate that proposed algorithm allows revealing a phoneme structure of pronounced speech with high probability. The advantages of this algorithm are absence of any prior information on a signal or model of phonemes and speakers that allows the algorithm to be speaker independent and have a low computation complexity.
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Relaxing the WDO Assumption in Blind Extraction of Speakers from Speech Mixtures
Abstract
The time-frequency masking approach in blind speech extraction consists of two main steps: feature clustering in a space spanned over delay-time and attenuation rate, and spectrogram masking in order to reconstruct the sources. Usually a binary mask is generated under the strong W-disjoint orthogonal (WDO) assumption (disjoint orthogonal representations in the frequency domain). In practice, this assumption is most often violated leading to weak quality of reconstructed sources. In this paper we propose the WDO to be relaxed by allowing some frequency bins to be shared by both sources. As we detect instantaneous fundamental frequencies the mask creation is supported by exploring a harmonic structure of speech. The proposed method is proved to be effective and reliable in experiments with both simulated and real acquired mixtures.
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Hidden Signature for DTW Signature Verification in Authorizing Payment Transactions
Abstract
Traditional use of dynamic time warping for signature verification consists of forming some dissimilarity measure between the signature in question and a set of “template signatures”. In this paper, we propose to replace this set with the hidden signature and use it to calculate the normalized errors of signature under verification. The approach was tested on the MCYT database, using both genuine signatures and skilled forgeries. Moreover, we present the real-world application of the proposed algorithm, namely the complete biometric system for authorizing payment transactions. The authorization is performed directly at a point of sale by the automatic signature verification system based on the hidden signature.
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Simulation Model of Biometric Authentication Using Multiagent Approach
Abstract
In this article authors present the concept of application of multiagent approach in modeling biometric authentication systems. After short introduction, we present a short primer to multiagent technology. Next, we depict current state of the art related to biometrics combined with multiagent approach. In the next part of the work we present four exemplary simulation models of biometric authentication environments as well as the results of their examination.
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Probabilistic Issues in Biometric Template Design
Abstract
Since the notion of biometric template is not well defined, various concepts are used in biometrics practice. In this paper we present a systematic view on a family of template concepts based on the L1 or L2 dissimilarities. In particular, for sample vectors of independent components we find out how likely it is for the median code to be a sample vector.
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The Template Selection in Biometric Systems Based on Binary Iris Codes
Abstract
Since the variability of data within readings from the same person is intrinsic property of every biometric system, the problem of finding a good representative – the template – was recognized and present since the beginning of biometrics. This problem was solved differently for different biometric types, yet usually the template somehow averages the collected data samples. However, for the iris type, the template is usually just one or a few samples. In this paper we describe the experiments that suggest that the averaging is also justified in case of iris template creation. This is an important fact, which can significantly improve a performance of biometric template protection methods for iris.
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Impact of Crosstalk into High Resistivity Silicon Substrate on the RF Performance of SOI MOSFET
Abstract
Crosstalk propagation through silicon substrate is a serious limiting factor on the performance of the RF devices and circuits. In this work, substrate crosstalk into high resistivity silicon substrate is experimentally analyzed and the impact on the RF behavior of silicon-on-insulator (SOI) MOS transistors is discussed. The injection of a 10 V peak-to-peak single tone noise signal at a frequency of 3 MHz ( fnoise) generates two sideband tones of −56 dBm separated by fnoise from the RF output signal of a partially depleted SOI MOSFET at 1 GHz and 4.1 dBm. The efficiency of the introduction of a trap-rich polysilicon layer located underneath the buried oxide (BOX) of the high resistivity (HR) SOI wafer in the reduction of the sideband noise tones is demonstrated. An equivalent circuit to model and analyze the generation of these sideband noise tones is proposed.
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Capacity and Quality Optimization of CDMA Networks
Abstract
Coverage and capacity are important issues in the planning process for cellular third generation (3G) mobile networks. The planning process aims to allow the maximum number of users sending and receiving adequate signal strength in a cell. This paper describes the conceptual expressions require for network coverage and capacity optimization analysis, examines service quality issues, and presents practical solutions to problems common to sub-optimality of CDMA networks.
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Routing Misbehavior Detection in MANETs Using 2ACK
Abstract
This paper proposes routing misbehavior detection in MANETs using 2ACK scheme. Routing protocols for MANETs are designed based on the assumption that all participating nodes are fully cooperative. However, due to the open structure and scarcely available battery-based energy, node misbehavior may exist. In the existing system, there is a possibility that when a sender chooses anintermediate link to send some message to a destination, the intermediate link may pose problems such as, the intermediate node may not forward the packets to destination, it may take very long time to send packets or it may modify the contents of the packet. In MANETs, as there is no retransmission of packets once it is sent, care must be taken not to loose packets. We have analyzed and evaluated a technique, termed 2ACK scheme to detect and mitigate the effect of such routing misbehavior in MANETs environment. It is based on a simple 2-hop acknowledgment packet that is sent back by the receiver of the next-hop link. 2ACK transmission takes place for only a fraction of data packets, but not for all. Such a selective acknowledgment is intended to reduce the additional routing overhead caused by the 2ACK scheme. Our contribution in this paper is that, we have embedded some security aspects with 2ACK to check confidentiality of the message by verifying the original hash code with the hash code generated at the destination. If 2ACK is not received within the wait time or the hash code of the message is changed then the node to next hop link of sender is declared as the misbehaving link. We simulated the routing misbehavior detection using 2ACK scheme to test the operation scheme in terms of performance parameters.
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National Institute of Telecommunications –International Partnership: Yesterday, Todayand Tomorrow
Abstract
National Institute of Telecommunications –International Partnership: Yesterday, Todayand Tomorrow
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Rural Telecommunications Infrastructure Selection Using the Analytic Network Process
Abstract
The decisions involved in rural settings are of complex nature, with some aspects compounded by the presence of intangible criteria. Hence, a suitable approach is needed that can produce effective solutions. This paper describes the applicability of a multicriteria decision-making method, specifically the analytic network process (ANP), to model the selection of an appropriate telecommunications infrastructure technology, capable of deploying e-services in rural areas of developing countries. It aims to raise awareness among telecommunication planners about the availability of ANP, and to demonstrate its suitability to enhance the selection process. The proposed model is constructed based on concerned experts’ views of relevant selection criteria and potential technology alternatives. Its network structure caters for all possible dependencies and interactions among criteria and alternatives.
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Telecommunications, Universal Service and Poverty in Mexico: a Public Policy Assessment (1990–2008)
Abstract
This article analyzes the design and implementation of telecommunications service policies targeted at the poorest regions of Mexico (1990–2008). It begins by defining universal access and service policies, their economic and social rationale. Secondly, it discusses the scope of public policies on universal service provision designed by Mexican authorities to achieve the goal of universal access. Thirdly, the paper analyzes the distributive effects of this set of policies among the
poorest sectors of the population. The sources on which this research was based were two national surveys: the Household Income and Expenditure Survey (2008), and the Household Survey of the Access and Use of Information Technologies (2007). The additional information on regional economic development was based on the poverty indexes by the national population council and economic information given by Mexico’s Census Bureau. Additional use was made of the annual reports prepared by Ministry of Communications, statistics published by the Federal Telecommunications Commission and official documents prepared by the government agencies. Finally, a series of in-depth interviews was conducted with the former representatives of the Office of Rural Telephony. Finally, the article discusses, in the light of available evidence, possible explanations for the apparent failure of the universal service policy that was implemented to bring at least basic voice services to Mexico’s neediest. -
Performance Analysis of a Bi-Objective Model for Routing and Wavelength Assignment in WDM Networks
Abstract
Establishing end-to-end connections on wavelength division multiplexing (WDM) networks requires setting up lightpaths, defining the sequence of optical fibres and the wavelength in each fibre (the routing and wavelength assignment problem) for traffic flow. This paper reviews a bicriteria model for obtaining a topological path (unidirectional or symmetric bidirectional) for each lightpath request in a WDM network, developed by the authors, and presents a performance analysis of the model by considering important network performance measures. An extensive performance analysis of the two bicriteria model is presented, comparing the performance metrics obtained with the monocriterion models using the same objective functions, in five different reference networks commonly used in literature.
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Computational Methods for Two-Level 0-1 Programming Problems through Distributed Genetic Algorithms
Abstract
In this paper, we consider a two-level 0-1 programming problem in which there is not coordination between the decision maker (DM) at the upper level and the decision maker at the lower level. We propose a revised computational method that solves problems related to computational methods for obtaining the Stackelberg solution. Specifically, in order to improve the computational accuracy of approximate Stakelberg solutions and shorten the computational time of a computational method implementing a genetic algorithm (GA) proposed by the authors, a distributed genetic algorithm is introduced with respect to the upper level GA, which handles decision variables for the upper level DM. Parallelization of the lower level GA is also performed along with parallelization of the upper level GA. The proposed algorithm is also improved in order to eliminate unnecessary computation during operation of the lower level GA, which handles decision variables for the lower level DM. In order to verify the effectiveness of the proposed method, we propose comparisons with existing methods by performing numerical experiments to verify both the accuracy of the solution and the time required for the computation.
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A Framework for Evaluation of Communication Bandwidth Market Models
Abstract
The article presents a method of analysis of marketbased models for resource allocation in communication networks. It consists of several stages: classification of a market model, generation of input data, data adaptation to a tested model, test calculations and, finally, presentation and interpretation of results. A set of general criteria to assess various models has been proposed. Tests are run using dedicated computer applications, data is stored in open XML-based format originated in the multicommodity market model. Network topologies are derived from the SNDlib library.
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Performance Analysis of Hybrid Phase Shift Keying over Generalized Nakagami Fading Channels
Abstract
In addition to the benefits of hybrid phase shift keying (HPSK) modulation in reducing the peak to average power ratio of the transmitted signal to reduce the zero crossings and the 0◦-degree phase transmissions, HPSK enhances the bit error rate (BER) measure of the signal performance. The constellation of the HPSK is analyzed, and an expression for the conditional probability of HPSK modulation over additive white Gaussian noise (AWGN) is derived. This BER measure of HPSK is shown to outperform quadrature phase shift keying (QPSK) modulation. HPSK performance through Nakagami – m fading channel is also considered.
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Charging Phenomena at the Interface Between High-k Dielectrics and SiOx Interlayers
Abstract
The transition regions of GdSiO/SiOx and HfO2/SiOx interfaces have been studied with the high-k layers deposited on silicon substrates. The existence of transition regions was verified by medium energy ion scattering (MEIS) data and transmission electron microscopy (TEM). From measurements of thermally stimulated current (TSC), electron states were found in the transition region of the HfO2/SiOx structures, exhibiting instability attributed to the flexible structural molecular network expected to surround the trap volumes. The investigations were focused especially on whether the trap states belong to an agglomeration consisting of a single charge polarity or of a dipole constellation. We found that flat-band voltage shifts of MOS structures, that reach constant values for increasing oxide thickness, cannot be taken as unique evidence for the existence of dipole layers.
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Channel Identification Using Chaos for an Uplink/Downlink Multicarrier Code Division Multiple Access System
Abstract
A scheme of chaotic spreading sequence for multicarrier code division multiple access system (MC-CDMA) is proposed to estimate the transmission channel. This system spreads spectrum and identifies the channel, simultaneously. The proposed scheme uses a chaotic sequence generated by a logistic map as a training signal and estimate channel parameters according to dynamics of the chaotic sequence. Encoding data by chaotic sequences is first built and then the orthogonal codes are used to spread the encrypted data for multiusers scheme. At the reception, first the channel parameters are identified using a training chaotic sequence in order to equalize the received data, and then the encrypted information is decoded for the desired user. The studies reveal that the proposed system (chaos plus orthogonal codes) significantly outperforms the Walsh- Hadamard code spreading in MC-CDMA system. The performance of the system
is considered in the multiuser case by means of simulation. The simulation result shows that the proposed chaotic code spreading approach for channel identification achieves significant improvement in the channel identification, comparing to using others training sequence or the least square method. -
The Design of 4×4 Multimode Interference Coupler Based Microring Resonators on an SOI Platform
Abstract
This paper would like to propose a novel microring resonator based on 4×4 multimode interference (MMI) couplers. The device acts as two separate microring resonators just in one structure. The transfer matrix method and the three dimensional beam propagation method (3D-BPM) are used to verify the working principle of the device. The device is then designed on silicon on insulator (SOI) technology. This device may be a very promising building block for optical switches, filters, add-drop multiplexers, delay lines and modulators.
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Percolation Driven Flooding for Energy Efficient Routing in Dense Sensor Networks
Abstract
Simple flooding algorithms are widely used in ad hoc sensor networks either for information dissemination or as building blocks of more sophisticated routing protocols. In this paper a percolation driven probabilistic flooding algo- rithm is proposed, which provides large message delivery ratio with small number of sent messages, compared to traditional flooding. To control the number of sent messages the proposed algorithm uses locally available information only, thus induces negligible overhead on network traffic. The performance of the algorithm is analyzed and the theoretical results are verified through simulation examples.
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A Microscopic Approach for THz Intersubband Challenges
Abstract
The main candidate to be a practical and low cost high power THz source is the intersubband-based quantum cascade laser, which can have a tremendous impact in many practical applications, including last mile and indoor telecommunication systems. In this review we discuss current challenges for THz intersubband device development from a microscopic point of view. Next summarize the search for new mechanisms and structure designs that can lead to intersubband gain without population inversion. This is a very important topic of current research, since is both an extremely elegant phenomenon from the basic physics of view and crucial for effective lasing in the THz range. The reason is that scattering phenomena can lead to level broadenings of the same order of magnitude of the lasing transitions, making population inversion by carrier injection in upper lasing subbands extremely difficult. Previous work in the literature is compared and contrasted with a new scheme that may lead to high temperature lasing by engineering the nonequilibrium population inversion with a combination of band structure and many body effects mediated by a k-space filter.
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Impact of Signaling System Performance on QoE in Next Generation Networks
Abstract
The first experience of quality by multimedia applications’ users takes place during the setup phase of a new connection. If the setup phase is not accepted or “slowly accepted”, the confidence of the user decreases. The user becomes more sensitive when he/she pays the connections with assured quality of service (QoS). In this case, the process of call request should be also accomplished with QoS guarantees. This paper presents the signaling sub-system implemented within the EuQoS system. The EuQoS signaling process follows main assumptions of next generation networks (NGN) architecture and performs tasks related with codec agreement between multimedia end users, admission control and resource reservation functions. In this paper, we present analytical, simulation and experimental results showing the impact of signaling system performance on quality of experience (QoE) for the potential users of multi-layer EuQoS system. In particular, the presented approach aims at ensuring user QoE of the connection setup phase by ensuring QoS for transferring signaling messages by the network.
