bluuebunny/crossref_metadata_2025_split huggingface dataset:
Users, services and traffic modelling for broadband telecommunications planning
Authors: Capurro Mario , Ravaglia Renzo , Giuli Dino 
Published: September 2008

AbstractThe emergent broadband networks represent the hub of the research and marketing activities in the telecommunications world. A rigorous network planning methodology is necessary in order to identify the most profitable introduction strategies of broadband telecommunications services and in order to determine the best network solutions according to users needs and fixed requirements, such as usually cost and performance requirements.The first step of such a methodology must deal with users and services analysis in the environment of interest.In this paper a proposal of users, services and traffic modelling is presented, which constitutes the first fundamental stage of a general broadband network planning theory. The analysis of these factors is performed, with particular focus on traffic characterization.
Design and verification of A CMOS transconductance cell with extended linearity
Authors: Gatti Umberto , Maloberti Franco , Torelli Guido 
Published: September 2008

AbstractA fully CMOS tunable transconductance cell is presented. The key element of the circuit is an MOS transistor operated in the triode region with an adjustable constant drain‐to‐source voltage. The cell can be used in both single‐ended‐input and differential‐input configurations. Both design considerations and measurements performed on integrated test structures are presented. The cell shows a very good linearity over a large dynamic range. For the cell used in the differential configuration, the measured total harmonic distortion is as good as −53 dB and ‐ 43 dB with a differential input signal peak amplitude of 3 V and 6 V, respectively, when the supply voltage is equal to ±5 V. The cell also shows very good performance up to several megahertz.
Effect of the transmission impairments on the performance of packet radio networks
Authors: Immovilli Gianni , Merani Maria Luisa 
Published: September 2008

AbstractPacket radio has recently gained great interest in the wider context of mobile communications. In this scenario, the signal worsening due to real transmission conditions (linear and nonlinear distortion, fading, interferences, noise) deeply affect the network performance. It is then necessary to verify whether it is feasible, and if so, how to dimension the transmission system supporting the network itself, in order to respect a fixed quality condition.In this work we suggest the introduction of a quality criterion which seems particularly suitable to set up a relationship between transmission and network parameters, and therefore to solve the problem previously submitted. We determine this relationship with reference to a star topology network, where the slotted Aloha protocol is employed in conjunction with a narrowband modulation scheme; independent, non‐selective and slowly varying fading conditions on every link of the network are also assumed.The treatment developed is then applied to a significant example of packet radio network, and many numerical results are reported.
An accuracy measure for DFT‐based analog filter simulation techniques
Authors: Presti Letizia Lo 
Published: September 2008

AbstractIt is well‐known that the simulation of analog filters must be based on the simulation theorem, which refers to a digital model of the filter to be simulated. Here we show the relationships between the DFT simulation techniques and this theorem, and how to extract the digital model implicitly contained in a filtering process based on DFT. As the simulation results depend on the quality of the digital model, we propose to introduce a parameter able to measure the difference between the actual model and the ideal one. Here we define a quality coefficient, related to the mean square error between the actual model and the ideal one, with some interesting characteristics: it can be very easily software implemented, depends only on the digital model, can be evaluated at the beggining of the simulation process (before filtering), gives the user a very simple criterion to estimate the quality of the digital model.
Classification of Ortho‐mode transducers
Authors: Bøifot Anton M. 
Published: September 2008

AbstractThis paper presents a classification of ortho‐mode transducers (OMTs). The OMTs are classified into five main groups. The first four contain OMTs based on waveguide‐to‐waveguide transitions. The basis for this classification is symmetrical properties which affect both the isolation and the matching capacities. A systematic analysis of the generation of symmetrical and odd symmetrical higher‐order modes including their influence on the isolation and matching conditions is also included. The last group of OMTs consists of devices with waveguide‐to‐coax transitions. These are denoted hybrid OMTs.
An abstract representation of the scalar wave equation of optics. Part 3
Authors: Kragl Hans 
Published: September 2008

AbstractThe abstract representation of the scalar wave equation of optics is extended from the time‐dependent wave equation to the stationary wave equation via the fundamental action integral. It is demonstrated that the stationary wave equation together with general initial conditions is not equivalent with the corresponding time‐dependent equation, because with the transition one has lost physical information. The consequences thereof are discussed. Subsequently the modes of the stationary wave equation are defined and their attributes, which follow from missing losses of the physical system, are given. Finally the mode coupling method for the stationary wave equation is derived by geometrical reflections. Two examples illustrate the considerations.
Loss formula for burst transmission spread spectrum systems
Authors: Kleinhempel Werner , Baier Paul Walter 
Published: September 2008

AbstractIn burst transmission spread spectrum systems it is advantageous to effect receiver synchronization by passive correlation, i.e. by matched filtering, and to detect the message by active correlation which means multiplication by a reference signal and integration in the time domain. If the number of available active correlation circuits is limited, a certain percentage of the arriving telegrams cannot be processed and will be lost. In conventional analog burst spread spectrum systems the loss can be calculated with the Erlang loss formula. For modern digital burst spread spectrum systems the Erlang loss formula is only an approximation which maiy give unaccurate results. In this paper an exact loss formula for digital spread spectrum systems will be presented and compared with the Erlang loss formula. The formula will be applied to minimize the loss of a practical system.
A new general procedure to extract the noise parameters of microwave gaAs mesfets
Authors: Armenise Mario Nicola , Perri Anna Gina 
Published: September 2008

AbstractIn this paper a generalized procedure to extract the noise parameters of GaAs MESFETs is presented. The average quadratic error between the measured values of optimum noise figure and the calculated ones is minimized in order to obtain the optimum admittance value at the amplifier input. The hypothesis of device unilaterality is assumed. A comparison between the proposed method and the previous ones has been carried out. A consequent more simplified analytical approach to evaluate the optimum noise source impedance of a GaAs MESFET amplifier allows the proposed procedure to be easly implemented in the most popular CAD tools.
Motion errors in an airborne synthetic aperture radar system
Authors: Buckreuss Stefan 
Published: September 2008

AbstractThe Institute for Radio Frequency Technology of the German Aerospace Research Establishment (DLR) in Oberpfaffenhofen operates an experimental synthetic aperture radar, E‐SAR. The Radar configuration was developed by DLR [1, 2] and consists of a L/C/X‐band SAR System and antennas with a wide beamwidth in azimuth and elevation. The system is installed in a small Dornier DO 228 aircraft, which operates at low altitudes between 1000 m ‐ 3000 m above ground. Due to atmospheric turbulences, the aircraft is displaced from its nominal flight path, causing a variation of the phase history of the returned radar signal. This eventually results in a degraded image quality and therefore a highly accurate motion compensation becomes necessary. It is intended to integrate an inertial measurement unit (IMU) within the E‐SAR system to support the used motion compensation algorithm during data processing [3]. The required relative accuracy of the IMU can be determined by means of statistics i.e. an approach is demonstrated to estimate the power spectral density (PSD) of the tolerable uncompensated aircraft motion. The performance of an IMU motion compensation system has been evaluated by analysis, as well as by computer simulation.
A fuzzy complete SAR processing chain for ship detection and velocity estimation
Authors: Alparone Luciano , Argenti Fabrizio , Benelli Giuliano , Cappellini Vito , Mecocci Alessandro 
Published: September 2008

AbstractEnvironmental monitoring by means of Remote Sensing methodologies is one of the most interesting and important application field of image processing techniques. In this field, a very important role is played by Synthetic Aperture Radar (SAR) images, that posses an high spatial resolution and that can be produced in all weather conditions. This paper presents a complete digital signal processing chain for the automatic detection of ships in SAR images and for the computation of an estimate of ship velocities. A particular attention has been devoted to two problems: the prefiltering problem which aims to reduce the speckle noise in the image, and the robustness problem that is related to the optimization of the true‐target detection/rejection capability. The whole chain has been first simulated and tested on a sequential machine, namely a Micro VAX II, and then it has been ported on a parallel architecture based on a hyper‐cube of IMS T800 transputers.
Preliminary considerations for an efficient SAR ocean simulation
Authors: Migliaccio Maurizio , Riccio Daniele , Schirinzi Gilda 
Published: September 2008

AbstractSome ideas toward a SAR raw data ocean simulator are presented. The suggested simulator is based on facets model of the ocean wave, two‐dimensional FFT code and asymptotic evaluation of the unit response function.Two main useful features are here explored: the phase velocity of dominant ocean wave which is supposed to travel at constant velocity; and the Bragg‐resonant dominant scattering mechanism.
An algebraic approach for performance evaluation in microwave links using angle diversity
Authors: Coraiola Alessandro 
Published: September 2008

AbstractThis paper deals with the quality of a line‐of‐sight digital radio link using angle diversity reception.Starting from a simple multipath model based on total reflections of the electromagnetic rays propagating in the atmosphere, a relation of delay between rays is inferred, which is linear with distance and, at least for long routes, is in accordance with experimental data.The paper goes on with the description of a radio channel, both for «minimum phase» and «non‐minimum phase», and with a theoretical analysis of a hop quality.Said analysis leads to consider the antenna characteristics, both in transmission and in reception, as basic components of the link performance and allows to conclude that the angle diversity may be used profitably if antennas with sufficiently narrow lobes are adopted.
Error probability evaluation in the presence of microwave oscillator phase noise
Authors: Buoli Carlo , Taverna Marcello , Ternau Wanda , Todero Franco 
Published: September 2008

AbstractThis work presents the theoretical calculation of the error probability as a function of the signal to noise ratio in presence of the oscillator phase noise in the 4 PSK and 16, 64, 256 and 1024 QAM systems. Experimental verifications confirm the computed values. On the basis of the procedure described herein, the design of two oscillators that operate in different modulation and capacity systems and with different values of the oscillation frequency is illustrated.
Performance of underlying hamming codes in M‐QAM digital radio systems with nonlinear distortions
Authors: Friederichs Karl‐Josef , Kovàts Janos 
Published: September 2008

AbstractThe performance of underlying Hamming codes in M‐QAM digital radio systems is analyzed in the presence of nonlinear distortions.An effective soft‐decision decoding algorithm is constructed to reduce the number of errors induced by the nonlinear and noisy channel.Then the residual bit error probability is calculated from the statistical estimations of the detector input samples. It is shown that for weakly and moderately nonlinear channels error correction coding can significantly improve the system performance.
On the nonbifurcated routing in virtual circuit communication networks
Authors: Zhang Zhigang , Hartmann Harro L. 
Published: September 2008

AbstractThe problem of optimal nonbifurcated routing in virtual circuit (VC) communication networks, such as the X.25 packet‐switched networks, the frame‐relay networks or the ATM networks, is considered. To describe the related characteristic of the generally asymmetrical transmit and receive traffic in such networks, a related multicommodity flow (RMCF) model with two traffic matrices is proposed. For solving the optimal flow assignment problem with this model, we present an algorithm which incorporates the transmit receive (TR) relation, an important practical constraint existing in most of the operational VC networks.A comparison of the RMCF model with the symmetrical multicommodity flow (SMCF) model shows that the former is superior with respect to the network delay. Furthermore, performance degradation has been observed, which is caused by using the traditional multicommodity flow (MCF) model due to the lack of VC bandwidth reservation of the receive traffic. We also show the dependency of the network throughput on the traffic symmetry versus the TR ratio.
Telecommunications and the introduction of home networks for the residential market
Authors: Stienstra A. J. Bert , Van Vaalen Martin , Wage Joseph 
Published: September 2008

AbstractMajor changes are likely to occur in the telecommunications infrastructure. Both researchers and standardisation institutes are hard at work paving the way for a Broadband Integrated Services Digital Network (B‐ISDN). At one time it was widely assumed in the telecommunications world that once such a network had been established, customers would feel the need for a home network, which could be used for a wide range of purposes. However, a recent review of developments has made it very clear that the equipment which people have in their homes ‐ including telecommunications equipment ‐ falls into the category of consumer electronics. Consequently, the introduction of home networks for the private consumer will proceed in a rather less orderly fashion than telecommunications experts used to think.
Letter pointer overflows in SDH equipments
Authors: Brugia Odoardo , Carbonelli Marco , De Seta Domenico , Perucchini Daniele 
Published: September 2008

AbstractParticular situations of pointer overflows, which can take place either in the presence of high amplitude wander on STM‐N signals entering SDH network elements or under severe failure conditions of the synchronization network, have been identified. In these situations waste of data results if no proper actions are carried out to handle pointer overflows. With reference to current regulations additional rules are proposed in order to avoid this kind of impairment on transported tributaries.
Letters wavelength selection via tunable birefringent optical fiber filters: A stimulated raman scattering light experiment
Authors: Gao Peijuan , Bassi Paolo , Zoboli Maurizio , Yang Tianlong , Jiang Shigan 
Published: September 2008

AbstractThe ability of a recently proposed birefringent all optical fiber filter in obtaining tunable wavelength selection is demonstrated using Stimulated Raman Scattering light. Three kinds of light: the pump light, the first order Stokes line and the second order Stokes line of a Nd:YAG laser have been extracted separately.
Numerical modeling of bends in optical rib and double rib waveguides
Authors: De Angelis Costantino 
Published: September 2008

AbstractA new method is proposed to reduce radiation and transition losses in bent rib waveguides. Theoretical results have been obtained and a numerical analysis performed with the Beam Propagation Method (BPM) has been used to find total losses of the bends which have been studied. The results indicate that sharp bends with low loss should be feasible with a simple technology.
An open environment for ATM broadband multimedia applications
Authors: Franceschini Guido , Petrelli Daniela , Sciarappa Antonio , Venuti Giovanni 
Published: September 2008

AbstractAdvances in trasmission and switching technologies promise a flexible and efficient Broadband ISDN (B‐ISDN), based on Asynchronous Transfer Mode (ATM), able to meet the increasing demand of high speed services. Multimedia applications are in particular expected to play a key role in B‐ISDN success. The paper wants to outline the architecture of an open environment based on a multimedia workstation for ATM developed in the framework of the Italian Information Technology project called Piano Finalizzato Telecomunicazioni (PFT). Design guidelines, interfaces and capabilities are described. After introducing the basic workstation architecture, some aspects of relevant multimedia applications and of the user interface are discussed.
Current architectures for ATM implementation
Authors: Melen Riccardo 
Published: September 2008

AbstractThis paper is devoted to the classification and preliminary assessment of the ATM switching architectures which are likely to hit the market in the next few years as the B‐ISDN implementation phase will proceed. In the first part of the paper a top down approach is attempted in the classification of switching architectures, with the aim of giving an abstract view of the possible options and setting a common, clearly understandable framework for their comparison. This classification is used as a guideline for a review of the current trends in ATM switching. Both current prototypes by major manufacturers and other proposals which can become products and be part of public or private networks in the future are reviewed. The merits and shortcomings of these solutions are discussed, but no direct comparison is attempted, due to the different purpose and technological effort involved in the various projects which does not provide a fair basis for comparative evaluation.
Congestion control strategies in ATM networks
Authors: Fratta Luigi , Musumeci Luigi , Gallassi Giorgio , Verri Luigi 
Published: September 2008

AbstractAsynchronous Transfer Mode (ATM) is a promising technique to implement the Broad‐band ISDN. When bursty sources are considered, high network efficiency can be obtained by taking advantage of statistical multiplexing. This technique requires to monitor the user behavior, in order to guarantee that the actual traffic parameters do not exceed the maximum values compatible with the required Grade of Service. The paper reviews the major results on the analysis of the control mechanisms. In particular, the three following issues are considered. The Connection Admission Control for both homogeneous and heterogeneous traffic sources is analyzed and the performance of different approaches are compared. The Leaky Bucket mechanism is studied for the Usage Parameter Control and its performance, such as reaction and recovery time, are analyzed. The traffic shaping function is considered in both cases of availability and non availability of a feedback on the traffic sources. The effectiveness of this functionality is investigated.
Performance analysis of trellis coded biorthogonal sequences in a variable rate system
Authors: Benvenuto Nevio , Chiaraluce Franco , Falcioni Paolo , Andreoli Sante 
Published: September 2008

AbstractFor digital communication systems with a given binary modulation scheme and variable information rate, a coding technique is described which employs a particular structure of trellis code. It consists of a convolutional encoder followed by a mapper which selects biorthogonal codewords. Based upon the state diagram of the system, performance is evaluated and then compared to that of more conventional solutions. Beside having good performance, this approach is very modular, i.e. its structure easily adapts to different information rates. Furthermore, it allows the time synchronization system to work at lower signal‐to‐noise ratios.
Letter a precise stereoscopic system with two video cameras
Authors: Tubaro Stefano 
Published: September 2008

AbstractA basic problem in stereopsis is to find the correspondence between points in right and left images. This paper presents some results obtained with a stereo vision system composed by two CCD video cameras with parallel optical axes.The presented results have been obtained using, to solve the correspondence problem, algorithms based on the comparison of the luminance profiles of the two images rather than based on the comparison of the binary images obtained after edge detection. These algorithms were originally conceived to allow motion compensated coding of TV sequences, but they are also very useful in solving the correspondence problem in stereopsis.Experimental results obtained from laboratory tests and from a hardware realization of the system are presented. And, despite the simplicity of the proposed system, they are quite promising.
Letter improved analysis of the effects of stimulated raman scattering in a multi‐channel WDM communication system
Authors: Comuzzi R. , De Angelis C. , Gianello G. 
Published: September 2008

AbstractA system of N first‐order differential equations, which describe N interacting channels in a WDM system affected by S.R.S., is solved numerically, under very general assumption, with the Runge‐Kutta method. Differential losses and different signals depletion rates are accounted for. The actual limitations imposed by SRS are evaluated and found to differ appreciably from previously published ones.
On the quantitative analysis of localized scattering centres in microwave images
Authors: Fuchs Ulrich , Wendel Horst 
Published: September 2008

AbstractThis paper introduces a new method to reveal the spectral information hidden in highly resolved microwave maps locally dominated by localized scattering centers. The method first partitions the map, i.e. it localizes these centers by suitable window function. It then transforms each segment containing a localized scattering center into frequency‐aspect angle space. The method is tested for a simulated scenario of two localized scatterers. Its superiority over previous exploitation schemes is borne out by applying it to experimental data on the edge scattering of a metal plate.
Spectral‐correlation based methods for multipath‐channel identification
Authors: Izzo Luciano , Napolitano Antonio , Tanda Mario 
Published: September 2008

AbstractThe paper deals with the problem of the estimation of the scaling amplitudes and the arrival times of a multipath signal. An extensive study of two new spectral‐correlation based estimation methods is presented. These algorithms are applicable as long as the multipath signal is cyclostationary. They are inherently tolerant to both noise and interference, and can, in principle, provide arbitrarily accurate estimates when a sufficiently long collect time is available. The methods are compared in terms of temporal resolution, arrival time dynamics and estimate accuracy. Finally, the performance of both considered methods is compared with that of conventional techniques based on temporal correlation.