Hindawi Publishing

Displaying 1681-1720 of 1733 results

  • White Papers // Apr 2009

    Multilevel Simulation of Heterogeneous Reconfigurable Platforms

    This paper presents a general system-level simulation and testing methodology for reconfigurable System-on-Chips, starting from behavioral specifications of system activities to multilevel simulations of accelerated tasks running on the reconfigurable circuit. The system is based on a common object-oriented environment that offers valuable debugging and probing facilities as well as...

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  • White Papers // Apr 2009

    Dynamic Subcarrier Allocation for Real-Time Traffic Over Multiuser OFDM Systems

    A dynamic resource allocation algorithm to satisfy the packet delay requirements for real-time services, while maximizing the system capacity in multiuser Orthogonal Frequency Division Multiplexing (OFDM) systems is introduced. The authors' proposed cross-layer algorithm, called Dynamic Subcarrier Allocation algorithm for Real-time Traffic (DSA-RT), consists of two interactive components. In the...

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  • White Papers // Apr 2009

    Degenerated-Inverse-Matrix-Based Channel Estimation for OFDM Systems

    This paper addresses time-domain channel estimation for pilot-symbol-aided Orthogonal Frequency Division Multiplexing (OFDM) systems. By using a cyclic sinc-function matrix uniquely determined by Nc transmitted subcarriers, the performance of proposed scheme approaches perfect Channel State Information (CSI), within a maximum of 0.4 dB degradation, regardless of the delay spread of...

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  • White Papers // Apr 2009

    Modeling Misbehavior in Cooperative Diversity: A Dynamic Game Approach

    Cooperative diversity protocols are designed with the assumption that terminals always help each other in a socially efficient manner. This assumption may not be valid in commercial wireless networks where terminals may misbehave for selfish or malicious intentions. The presence of misbehaving terminals creates a social-dilemma where terminals exhibit uncertainty...

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  • White Papers // Apr 2009

    Implementing Statistical Multiplexing in DVB-H

    A novel technique for implementing Statistical Multiplexing (StatMux) of broadcast services over Digital Video Broadcasting for Handhelds (DVB-H) channels is proposed. DVB-H uses a time-sliced transmission scheme to reduce the power consumption used for radio reception part in DVB-H receivers. Due to the time-sliced transmission scheme, the implementation of known...

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  • White Papers // Apr 2009

    An Adaptive Message Passing MPSoC Framework

    Multi-Processor Systems-on-Chips (MPSoCs) offer superior performance while maintaining flexibility and reusability thanks to software oriented personalization. While most MPSoCs are today heterogeneous for better meeting the targeted application requirements, homogeneous MPSoCs may become in a near future a viable alternative bringing other benefits such as run-time load balancing and task...

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  • White Papers // Apr 2009

    A Reconfigurable and Biologically Inspired Paradigm for Computation Using Network-On-Chip and Spiking Neural Networks

    FPGA devices have emerged as a popular platform for the rapid prototyping of biological Spiking Neural Networks (SNNs) applications, offering the key requirement of reconfigurability. However, FPGAs do not efficiently realise the biologically plausible neuron and synaptic models of SNNs, and current FPGA routing structures cannot accommodate the high levels...

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  • White Papers // Apr 2009

    A Flexible and Efficient Key Distribution Scheme for Renewable Wireless Sensor Networks

    Many applications of wireless sensor network require secure data communications, especially in a hostile environment. In order to protect the sensitive data and the sensor readings, secret keys should be used to encrypt the exchanged messages between communicating nodes. Traditional asymmetric key cryptosystems are infeasible in WSN due to its...

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  • White Papers // Apr 2009

    In Situ Key Establishment in Large-Scale Sensor Networks

    Due to its efficiency, symmetric key cryptography is very attractive in sensor networks. A number of key predistribution schemes have been proposed, but the scalability is often constrained by the unavailability of topology information before deployment and the limited storage budget within sensors. To overcome this problem, three in-situ key...

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  • White Papers // Apr 2009

    Bargaining and the MISO Interference Channel

    The authors examine the MISO interference channel under cooperative bargaining theory. Bargaining approaches such as the Nash and Kalai-Smorodinsky solutions have previously been used in wireless networks to strike a balance between max-sum efficiency and max-min equity in users' rates. However, cooperative bargaining for the MISO interference channel has only...

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  • White Papers // Apr 2009

    Improving the Performance of Bus Platforms by Means of Segmentation and Optimized Resource Allocation

    Consider a processor organization consisting of a number of client modules and server modules (jointly called devices), like memory units and arithmetic-logic processing units. Suppose that these devices are interconnected with a bus which is segmented in such a way that devices connected to a particular segment can communicate in...

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  • White Papers // Apr 2009

    A New Multithreaded Architecture Supporting Direct Execution of Esterel

    The authors propose a fully pipelined, multithreaded, reactive processor called STARPro for direct execution of Esterel. STARPro provides native support for Esterel threads and their scheduling. In addition, it also natively supports Esterel's preemption constructs, instructions for signal manipulation, and a notion of logical ticks for synchronous execution. In addition...

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  • White Papers // Apr 2009

    Probabilistic Localization and Tracking Of Malicious Insiders Using Hyperbolic Position Bounding in Vehicular Networks

    A malicious insider in a wireless network may carry out a number of devastating attacks without fear of retribution, since the messages it broadcasts are authenticated with valid credentials such as a digital signature. In attributing an attack message to its perpetrator by localizing the signal source, the authors can...

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  • White Papers // Mar 2009

    Implementation of a Cooperative MAC Protocol: Performance and Challenges in a Real Environment

    Cooperative communication is an active area of research today. It enables nodes to achieve spatial diversity, thereby achieving tremendous improvement in system capacity and delay. Due to its immense potential, extensive investigations have been directed to closely examine its performance by means of both analysis and simulation. However, the study...

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  • White Papers // Mar 2009

    Performance Analysis of Bit-Width Reduced Floating-Point Arithmetic Units in FPGAs: A Case Study of Neural Network-Based Face Detector

    This paper implements a Field Programmable Gate Array- (FPGA-) based face detector using a Neural Network (NN) and the bitwidth reduced Floating-Point arithmetic Unit (FPU). The analytical error model, using the Maximum Relative Representation Error (MRRE) and the Average Relative Representation Error (ARRE), is developed to obtain the maximum and...

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  • White Papers // Mar 2009

    A Geometry-Inclusive Analysis for Single-Relay Systems

    Successful message relay, or the quality of the interuser channel, is critical to fully realize the cooperative benefits promised by the theory. This in turn points out the importance of the geometry of cooperative system. This paper investigates the impact of the relay's location on the system capacity and outage...

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  • White Papers // Mar 2009

    Firefly Clock Synchronization in an 802.15.4 Wireless Network

    This paper describes the design and implementation of a distributed self-stabilizing clock synchronization algorithm based on the biological example of Asian Fireflies. Huge swarms of these fireflies use the principle of pulse coupled oscillators in order to synchronously emit light flashes to attract mating partners. When applying this algorithm to...

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  • White Papers // Mar 2009

    Low Profile EBG Resonator Antennas

    An Electromagnetic Band Gap (EBG) antenna is a planar structure which is composed of a cavity and an EBG material. In most applications, the height of the EBG antenna is half wavelength. The authors present in this paper the conditions to reduce the profile of an EBG antenna to subwavelength...

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  • White Papers // Mar 2009

    Time Domain Equalizer Design Using Bit Error Rate Minimization for UWB Systems

    Ultra-WideBand (UWB) communication systems occupy huge bandwidths with very low power spectral densities. This feature makes the UWB channels highly rich in resolvable multipaths. To exploit the temporal diversity, the receiver is commonly implemented through a Rake. The aim to capture enough signal energy to maintain an acceptable output Signal-to-Noise...

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  • White Papers // Mar 2009

    vMAGIC-Automatic Code Generation for VHDL

    Automatic code generation is a standard method in software engineering, improving the code reliability as well as reducing the overall development time. In hardware engineering, automatic code generation is utilized within a number of development tools, the integrated code generation functionality, however, is not exposed to developers wishing to implement...

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  • White Papers // Mar 2009

    High level modeling of Dynamic Reconfigurable FPGAs

    As System-on-Chip (SoC) based embedded systems have become a defacto industry standard, their overall design complexity has increased exponentially in recent years, necessitating the introduction of new seamless methodologies and tools to handle the SoC co-design aspects. This paper presents a novel SoC co-design methodology based on Model Driven Engineering...

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  • White Papers // Mar 2009

    Adaptive Error Resilience for Video Streaming

    Compressed video sequences are vulnerable to channel errors, to the extent that minor errors and/or small losses can result in substantial degradation. Thus, protecting compressed data against channel errors is imperative. The use of channel coding schemes can be effective in reducing the impact of channel errors, although this requires...

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  • White Papers // Mar 2009

    Orthogonal Space-Time Block Codes in Vehicular Environments: Optimum Receiver Design and Performance Analysis

    The authors consider Orthogonal Space-Time Block Codes (OSTBC) in vehicular environments, where the channels are non-identically distributed. It is shown that the non-identical channel statistics lead to non-identical channel estimation errors, which consequently affect the performance and even the existing receiver structure of OSTBC. They show that the conventional Symbol-By-Symbol...

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  • White Papers // Mar 2009

    Ku Band Hemispherical Fully Electronic Antenna for Aircraft in Flight Entertainment

    The results obtained in the frame of the ESA activity "Advanced Antenna Concepts For Aircraft In Flight Entertainment" are presented. The aim of the activity consists in designing an active antenna able to guarantee the Ku band link between an aircraft and a geostationary satellite in order to provide in...

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  • White Papers // Mar 2009

    APRON: A Cellular Processor Array Simulation and Hardware Design Tool

    The authors present a software environment for the efficient simulation of Cellular Processor Arrays (CPAs). This software APRON (Array Processing enviRONment) is used to explore algorithms that are designed for massively parallel fine-grained processor arrays, topographic multilayer neural networks, vision chips with SIMD processor arrays, and related architectures. The software...

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  • White Papers // Mar 2009

    A Fast LMMSE Channel Estimation Method for OFDM Systems

    A fast Linear Minimum Mean Square Error (LMMSE) channel estimation method has been proposed for Orthogonal Frequency Division Multiplexing (OFDM) systems. In comparison with the conventional LMMSE channel estimation, the proposed channel estimation method does not require the statistic knowledge of the channel in advance and avoids the inverse operation...

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  • White Papers // Mar 2009

    A Novel Image Data Hiding Scheme With Diamond Encoding

    A novel data hiding scheme in digital images with the diamond encoding by pixel value adjustment is proposed. The proposed method is the extension of the Exploiting Modification Direction (EMD) embedding scheme. First, the process of embedding partitions the cover image into non-overlapping blocks of two consecutive pixels and transforms...

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  • White Papers // Mar 2009

    Advances in Propagation Modeling for Wireless Systems

    Advanced wireless systems face an ever-increasing number of challenges, such as the limited availability of the radio frequency spectrum and the demand for faster data transmissions, better quality of service, and higher network capacity. Yet, the true challenge faced by new communication technologies is to achieve the expected performance in...

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  • White Papers // Mar 2009

    Performance Comparison of Reflector- and Planar-Antenna Based Digital Beam-Forming SAR

    The trend in the conception of future spaceborne radar remote sensing is clearly toward the use of digital beamforming techniques. These systems will comprise multiple digital channels, where the analog-to-digital converter is moved closer to the antenna. This dispenses the need for analog beam steering and by this the used...

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  • White Papers // Mar 2009

    Propagation Measurements and Comparison with EM Techniques for In-Cabin Wireless Networks

    This paper presents results of a narrowband measurement campaign conducted inside a Boeing 737 - 400 aircraft, the objective being the development of a propagation prediction model which can be used in the deployment of in-cabin wireless networks. The measurements were conducted at three different frequency bands: 1.8, 2.1, and...

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  • White Papers // Mar 2009

    Optimal Channel Width Adaptation

    Radio frequency spectrum is a finite and scarce resource. How to efficiently use the spectrum resource is one of the fundamental issues for multi-radio multi-channel wireless mesh networks. However, past research efforts that attempt to exploit multiple channels always assume channels of fixed predetermined width, which prohibits the further effective...

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  • White Papers // Mar 2009

    Cooperative Mobile Web Browsing

    This paper advocates a novel approach for mobile web browsing based on cooperation among wireless devices within close proximity operating in a cellular environment. In the actual state of the art, mobile phones can access the web using different cellular technologies. However, the supported data rates are not sufficient to...

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  • White Papers // Mar 2009

    On Power Allocation for Parallel Gaussian Broadcast Channels with Common Information

    This paper considers a broadcast system in which a single transmitter sends a common message and (independent) particular messages to K receivers over N unmatched parallel scalar Gaussian subchannels. For this system the set of all rate tuples that can be achieved via SuperPosition Coding and Gaussian Signalling (SPCGS) can...

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  • White Papers // Mar 2009

    Accurate Antenna Pattern Modeling for Phased Array Antennas in SAR Applications - Demonstration on TerraSAR-X

    The high flexibility and tight accuracy requirements of today's space borne Synthetic Aperture Radar (SAR) systems require innovative technologies to calibrate and process the SAR images. To perform accurate pattern correction during SAR processing, an Antenna Model is used to derive the multitude of different antenna beams generated by active...

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  • White Papers // Mar 2009

    Reliable Steganalysis Using a Minimum Set of Samples and Features

    This paper proposes to determine a sufficient number of images for reliable classification and to use feature selection to select most relevant features for achieving reliable steganalysis. First dimensionality issues in the context of classification are outlined, and the impact of the different parameters of a steganalysis scheme (the number...

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  • White Papers // Mar 2009

    A Time-Variant MIMO Channel Model Directly Parametrised from Measurements

    This paper presents the Random-Cluster Model (RCM), a stochastic time-variant, frequency-selective, propagation-based MIMO channel model that is directly parametrised from measurements. Using a fully automated algorithm, multipath clusters are identified from measurement data without user intervention. The cluster parameters are then used to define the propagation environment in the RCM....

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  • White Papers // Mar 2009

    Multiple CFOs in OFDM-SDMA Uplink: Interference Analysis and Compensation

    In OFDM-based Space Division Multiple Access (SDMA) systems, multiple users are served by a multiantenna base station simultaneously on the same frequency resources. In the uplink, each user's signal may be distorted by an independent Carrier Frequency Offset (CFO), which impairs the orthogonality of the subcarrier signals and, if not...

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  • White Papers // Feb 2009

    Flat Array Antennas for Ku-Band Mobile Satellite Terminals

    This paper presents the advances in the development of two innovative flat array antennas for Ku-band mobile satellite terminals. The first antenna is specifically conceived for double-deck trains to allow a bi-directional high data rate satellite link. The available circular surface (diameter 80 cm) integrates both a transmitting and a...

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  • White Papers // Jan 2009

    Autocorrelation Properties of OFDM Timing Synchronization Waveforms Employing Pilot Subcarriers

    The authors investigate the autocorrelation properties of timing synchronization waveforms that are generated by embedded frequency domain pilot tones in Orthogonal Frequency Division Multiplex (OFDM) systems. The waveforms are composed by summing a selected number of OFDM subcarriers such that the AutoCorrelation Function (ACF) of the resulting time waveform has...

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  • White Papers // Dec 2008

    Parallel Backprojection: A Case Study in High-Performance Reconfigurable Computing

    High-Performance Reconfigurable Computing (HPRC) is a novel approach to provide large-scale computing power to modern scientific applications. Using both General-Purpose Processors (GPPs) and FPGAs allows application designers to exploit fine-grained and coarse-grained parallelism, achieving high degrees of speedup. One scientific application that benefits from this technique is backprojection, an image...

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