bluuebunny/crossref_metadata_2025 huggingface dataset:
Analytical ecological epidemiology: exposure–response relations in spatially stratified time series
Authors: Scherb Hagen , Voigt Kristina
Published: September 2008

An important task of environmental research is the investigation of a possible causal relationship between exposure and the frequency of a biologic trait. Major industrial accidents provide examples where the exposure status of large populations may change considerably within relatively short time intervals of days or weeks (e.g. Seveso herbicide plant explosion, Chernobyl Nuclear Power Plant catastrophe). Therefore, purely temporal change‐points may be tested in time series of appropriate public health indicators (e.g. mortality, morbidity, sex ratio at birth). If, in addition, the spatial contamination is strong and variable enough and can be identified with sufficient precision at the level of regional units (e.g. districts), then a spatial‐temporal approach makes sense. This essentially means that a global time trend model is adjusted for region‐specific trend functions, allowing for local or global temporal jumps or broken sticks (change‐points) at certain points in time. The local jump heights may be tested for associations with local exposure (exposure–response relation), and all other characteristics in the data that vary with locality and in time are automatically accounted for, thus minimizing confounding. Spatial‐temporal approaches may help to strengthen the evidence of possible causal relationships. As an example, the human sex ratio at birth in several European countries before and after the Chernobyl Nuclear Power Plant accident was investigated. A long‐term chronic impact of radioactive fallout on the secondary sex ratio has been found. Copyright © 2008 John Wiley & Sons, Ltd.
Europe 1992: The European commission's policy in telecommunications
Authors: Schulte‐Braucks Reinhard
Published: September 2008

This article deals with both the principles of the Green Paper on telecommunications and the current situation of its implementation. It presents the measures necessary for the completion of the Community's internal market and the liberalization of the markets for telecommunications terminal equipment and services. Moreover, it describes the European Commission's initiatives in the field of public procurement and Community‐wide telecommunications infrastructures.
A modification of the predictive analysis for the multiple site diversity performance taking into account the stratified rain
Authors: Kanellopoulos John , Ventouras Spyros
Published: September 2008

Multiple site diversity systems are foreseen for earth to satellite paths operating at frequencies above 10 GHz in localities with high rain‐induced attenuation. A recently suggested model for the prediction of diversity performance is properly modified by considering also the stratified type of rain. The modified method uses the assumption of lognormal unconditional distribution of rainfall for the location under consideration. Numerical results are applied to several satellite systems operating in various locations in the United States and Italy. Some useful conclusions are deduced.
Comparison of different facsimile data compression methods for text, graphics and halftone documents
Authors: Böhm Wolfgang , Hartmann Ralf , Ruske Günther
Published: September 2008

In order to store digital image data in a pel‐by‐pel representation a huge amount of storage capacity is necessary. For example a DIN A4 page scanned with a resolution of 300 dpi (dots per inch) needs about 1.1 Mbyte storage capacity in binary representation.

This paper deals with various methods to compress binary image data. The focus is to discuss their suitability for archiving usual business documents made up of text, graphics and halftone segments.

The two‐dimensional CCITT group 4 recommendation is compared with an adaptive prediction algorithm and a Classified Pel‐Pattern (CLAP) method. For the latter a very efficient systematic code is given. The Classified Pel‐Pattern algorithm achieves the best data compression but at the cost of high complexity. Compressing documents scanned with a resolution of 300 dpi the measured compression ratio is between 1.3–2.5 (halftone pictures) and 50 (line art). Considering only text and graphic documents the recommendation of the CCITT is 5–10% worse but complexity is significantly less. However, it is found that this methods show unsatisfactory results applied to halftone pictures.
Linear prediction methods for interference elimination in spread spectrum systems
Authors: Bernardini Angelo , Bernesi Marco , Salerno Mario
Published: September 2008

The performance of Pseudonoise (PN) Spread Spectrum System in the presence of narrow‐band interference can be improved by using various types of interference rejection filters.

In this paper two different approaches are considered, the first based on Surface Acoustic Wave (SAW) devices and the second based on digital whitening using transversal filters.

The reasons for the convenience of digital whitening are discussed and techniques for determining the coefficients of a linear interference suppression filter are described.

Numerical results are presented on the characteristics of the linear filter and on its effectiveness in suppressing the interference when many different jamming and signaling conditions are considered.

It is found that a critical point is the choice of the filter order which is related to a number of different design parameters: the signal‐to‐jammer power ratio, the noise power, the number of bands in which the jammer tones are splitted and the number of signal samples used in the coefficient estimation.
A migrating data driven architecture for signal processing
Authors: Brofferio Sergio , Mastronardi Giuseppe
Published: September 2008

The paper presents a migrating operations data‐driven multiprocessor architecture suited for digital signal processing.

Three types of basic operations are first defined; this allows a simplified and efficient representation of algorithm execution in terms of Petri Nets.

Data‐flow primitives, packets and operators, allow the implementation of the algorithm into an architecture, which is a generalization of the well known data driven architecture.

Operand packets allow migration of operation computing from one processor to the neighbouring ones in case of nonuniform computation load within the system.

The architecture of the data driven processor is then examined in its basic blocks and an example of operation migration control strategy is shown.

Different architectures suited for specific trade‐off are proposed.
VLSI technologies: High performers and workhorses
Authors: Baldi Livio
Published: September 2008

The evolution of integrated circuit has been characterized in the past three decades by an exponential growth, both in performances and in circuit complexity, and it is showing no sign of slowing down. Several families of technologies have contributed to this explosive development: bipolar, GaAs and MOS, but only the last one has emerged as suitable for VLSI. However, each of the three has found its special field of application and is bringing its contribute to the total growth of circuit integration. It is very likely that all three shall coexist also in the next future, and will benefit from a mutual exchange of basic techniques. CMOS however will remain the main technology for VLSI, due to low power dissipation, flexibility and relatively low complexity. The critical issues which could hinder the further development of CMOS technology in the submicron range are essentially related to reliability, due to the increase in electric field and power density. The proposed solutions will probably imply new standards in supply voltages and slow down the progress in device speed.
Shallow junctions for ULSI technology
Authors: Solmi Sandro , Angelucci Renato , Merli Marco
Published: September 2008

Abstract.

Post‐implantation annealing conditions suitable to obtain very shallow p + ‐n and n + ‐p junctions with good electrical characteristics are critically examined by considering transient enhanced diffusion phenomena, dopant electrical activation, regrowth of the amorphous layer and radiation damage removal. Since activation energy of the diffusion processes is lower than that of damage recovery, high temperature rapid thermal annealings results, in principle, the best technique to fabricate shallow junction. The characteristics of diodes with junction depth of about 0.1 μm obtained by low energy implantation and annealing at 1000°C for 10 s are reported and discussed. Finally, ion implantation of B and As through a film of molybdenum or molybdenum silicide has been considered as a promising approach to shallow junction formations. Preliminary results related to devices fabricated by means of this self‐aligned procedure are presented.
Doped SiO2 deposition from TMP in APCVD
Authors: Bartholomew L. D. , Gralenski N. M. , Sisson J. C. , Pignatel G. U.
Published: September 2008

In this work we have investigated the feasibility of atmospheric pressure chemical vapor deposition of phosphorus and boron doped silicon oxides from a liquid source—namely TMP (tri‐methyl‐phosphite)—an alternative to phosphine as a P dopant source'. The most important results on process characterization, dopant incorporation, and film properties are presented. In addition to the easy operation of the liquid source, a remarkable improvement in step coverage has been found, in comparison with PSG deposition from conventional silane and phosphine chemistry.
Testing of E2PROM aging and endurance: A case study
Authors: Lanzoni Massimo , Menozzi Roberto , Olivo Piero , Riccò Bruno , Haardt Andrea
Published: September 2008

This work presents a detailed characterization of commercial E2PROMs performed by means of a new technique that allows non destructive monitoring of cell aging. Such a tech nique is based on accurate time control of the device power supply to stop the programming process, thus freezing the charge injected into the floating gate. Since a characteristic time is measured, the experiments can be performed varying other important parameters (in particular the supply voltage), whose influence on device endurance has been demonstrated. Thp method is also used to monitor the floating gate charging and discharging dynamics exploiting measurements of the drawn current.
Investigation of non‐local transport phenomena in small semiconductor devices
Authors: Gnudi Antonio , Odeh Farouk , Rudan Massimo
Published: September 2008

The hydrodynamic transport model based fin the generalized momentum and energy equations is used to simulate a n + ‐n‐n + one‐dimensional silicon device and the results are compared with Monte Carlo calculations. The non‐local effects are shown to become important for lengths of the order of a few tenths of a micrometer at applied voltages around 1.0–1.5 V. The hydrodynamic and Monte Carlo velocity and energy are generally in good agreement. Finally, the effects of the thermal conductivity and of the convective terms, in regions where large gradients are present, are investigated.
Information management in VLSI technology
Authors: Robertson John M. , Holwill Robert J.
Published: September 2008

Any review of the development of microelectronics technology tends to emphasise improvements in packing density. However, there are also a number of other important parallel developments. This paper considers the factors which have contributed to an explosion of data concerning the device fabrication process. Ways in which that data may be structured and handled as technical or product information are reviewed and some of the implications for success are also out‐lined.
Two‐dimensional simulation of quantum well lasers
Authors: Song G. Hugh , Hess Karl , Kerkhoven Thomas , Ravaioli Umberto
Published: September 2008

A versatile two‐dimensional simulator for various types of semiconductor lasers for both steady state and transients has been developed. The simulator is capable of spectral analysis of quantum‐well semiconductor lasers, such as gain‐spectrum analysis, as well as analysis of the two‐dimensional current flow and optical intensity patterns. The simulator is based on the drift‐diffusion model with full Fermi‐Dirac statistics for the transport equations as well as for the Poisson equation. Simulation of the thermionic emission current is required at the abrupt heterointerfaces of the quantum well. For the spectral analysis of quantum‐well lasers, we have used the photon rate equation for each Fabry‐Perot mode. For the optical intensity pattern, we have solved the two‐dimensional Helmholtz eigenvalue equation using the subspace iteration method. The transient simulation is done by the full backward‐Euler method in conjunction with the full Newton approach for the entire semiconductor equations. To demonstrate the simulator, a model GaAs‐AIGaAs graded‐index‐separate‐confinement‐heterostructure buried‐quantum‐well laser is analyzed.
Quasi‐two dimensional MESFET models application and validation
Authors: Snowden Christopher M. , Pantoja Renato R.
Published: September 2008

A physical model of a gallium arsenide MESFET, based on an improved quasi‐two‐dimensional description of the transport in the device is presented. The formulation of the model includes a comprehensive treatment of the doping profile and allows sharp variations in the profile to be reflected in the device characteristics, unlike previously published models. The model is applied to the dc and microwave characterisation of MESFETs and microwave power amplifiers. Comparison with a wide range of measured data has permitted the validation of the models for a variety of small‐signal and power devices.
A computer aided procedure for experimental chamcterization and small signal modeling of MESFETs
Authors: Ferrero Andrea , Pisani Umberto
Published: September 2008

A system which integrates in a single workstation the experimental procedures and data processing in order to carry out small‐signal equivalent circuits of microwave FET is presented.

The workstation basic hardware consists of a HP8510 vector network analyzer, a dual programmable power supply, a dc bias switching box and a HP9000 series 300 desktop computer.

While other approaches base the extraction of circuit elements mainly from scattering parameter measurements, the developed one implements several types of measurement techniques both in dc (pulsed), and in, necessary to directly extract several circuit parameters.

Thus the optimization of a great number of parameters is avoided, which often leads either to an ill conditioned determination of element values, or to extraction of physically meaningless parameters.

Furthermore by means of the described procedure several MESFET parameters tied to the technological process can be achieved.

Some experimental results obtained with on wafer ion implantated devices show a very good model accuracy reached in the frequency band from 1 GHz to 18 GHz.
Alternative formulation of boundary‐element method for two‐dimensional electromagnetic boundary‐value problems
Authors: Gentili Gian Guido
Published: September 2008

An alternative formulation of the Boundary Element Method for internal two‐dimensional electromagnetic boundary‐value problems related to Helmholtz equation is presented.

The formulation does not require the computation of special functions and the speed of computation is considerably faster than in standard formulations of BEM. The method of moments is used to solve the integral equation of BEM and all the integrals are computed analytically.

Several examples of application of the method to the study of planar structures are shown and a comparison with the results obtained with standard BEM analysis is presented.
A new millimetre wave satellite system for land mobile communications
Authors: Valdoni Francesco , Ruggieri Marina , Vatalaro Francesco , Paraboni Aldo
Published: September 2008

Cellular systems are gaining wide acceptance. In Europe the GSM system is expected to provide service to more than 10 million users by the year 2000. Assuming that a demand for additional services at 64 kbit/s or so will not easily be satisfied either by the present GSM system or by advanced satellite systems at L‐band, this paper proposes a new satellite system at EHF (40150 GHz) to be integrated at the end of the decade with the GSM system or its descendants. First, the paper describes the main obstacles for the new system, in terms of channel characteristics and technology developments, and then illustrates a preliminary system design to show the technical feasibility in the proposed ten years time scale.
Mathematical approaches to electron device modelling for non‐linear microwave circuit design: State of the art and present trends
Authors: Filicori Fabio , Monaco Vito A. , Vannini Giorgio
Published: September 2008

The accuracy of CAD techniques for the design of non‐linear microwave circuits is strongly dependent on the features of the models used for the characterization of electron devices (i.e. MESFET, bipolar transistors, diodes etc.,.). At present, empirical equivalent circuits are widely used. These models, which are in many cases sufficiently accurate, require, however, quite refined numerical and measurement techniques to extract from measured data the parameters of a model which is strongly dependent on the particular physical structure of each device.

Moreover, when using equivalent circuit models, the design of non‐linear microwave circuits must be carried out by using numerical optimization techniques. In this respect a simple mathematical model described in the frequency domain in terms of explicit equations between the electrical variables, would be preferable for the designer. Mathematical models, in fact, allow quite easy, direct procedures for circuit design. This paper deals with the problem of mathematical modelling of electron devices operating under large‐signal conditions at microwave frequencies. In particular, mathematical models based on the describing‐function and Volterra‐series approach are considered also taking into account their application to circuit design. The advantages of a recently proposed mathematical modelling approach based on mild assumptions valid for most types of electron devices, are also discussed in the paper.
Speech and image coding for digital communications
Authors: Guglielmo Mario , Modena Giulio , Montagna Roberto
Published: September 2008

The paper is presenting a sketch of the main results achieved in the recent years and of the ongoing activities (mainly within the Standardization Bodies) in the areas of audio and video coding for bandwidth reduction. The evolution of the telecommunication Field and the needs which originate the different standards are also considered.

The paper is organized in two main chapters: the first one is dealing with the techniques for audio and speech coding while the second presents the main achievements in terms of Recommendations and consolidate algorithms for image coding. Concerning speech and audio coding the paper presents and overview of the coding techniques and then examines the different environments of transmissions (network and mobile communication), the bandwidths required to satisfy the considered applications and the defined speech quality evaluation methods. A similar approach has been used for video coding and the evolution of the coding techniques appearing in the CCITT Recommendations is presented. The ongoing activities within CCIR, CMIT, CCITT and ISO towards new worldwide standards are also outlined providing indications on the areas which will require further developments.
Integrated services digital networks: Narrowband networks
Authors: Mossotto Cesare
Published: September 2008

This paper deals with the deployment of the narrowband Integrated Services Digital Network, which is conceived as a significant rationalization of the existing public telecommunication networks, which include at present a number of different structures devoted to the various kinds of services.

The main guidelines of ISDN evolution are depicted, starting with a short analysis of the expected wide range of TLC services, as this market is the main driving force for the deployment of new network architectures providing a powerful integrated access, a rapid service introduction and a high flexibility. The resulting reference network architecture is then described, highlighting the maximum possible integration of techniques and services, the unified access for the whole range of TLC services, the significant improvement of the user‐network signalling capabilities, the provision of high level network capabilities and the efficient communication among the various network entities. Some interworking and network dimensioning aspects, related to the gradual deployment of this new network architecture, are also examined, together with some consideration about further evolutionary steps.

A second part of the paper is devoted to an analysis of ISDN functionalities, starting with a short survey of ISDN protocols (X.31 network access protocol, higher layers protocols, CCITT N. 7 network signalling for ISDN), which are the international standards on which this evolution is based. Circuit and packet ISDN switching facilities are then briefly examined, focusing on ISDN access functions, which are very important for both the access integration and the hardware cost reduction. A further important point examined concerns ISDN protocol testing and validation (for both terminals and switching offices), together with the performance evaluation of ISDN switching officies.

The last part of the paper is devoted to a short survey of the present status of ISDN world development (pilot services, start of commercial services), starting from the European situation (France, Germany, United Kingdom, Italy etc.), examining the ISDN development in other Countries (United States, Japan, Canada and others) and giving finally some indications about the expected future plans.
Integrated services digital networks: Broadband networks
Authors: Listanti Marco , Roveri Aldo
Published: September 2008

This paper deals with the final goal of the evolutionary process of the public telecommunication networks towards broadband capabilities (B‐ISDN), process which is based on the adoption of the Asynchronous Transfer Mode (ATM).

At first, a critical analysis is carried out about the transfer modes which gave rise to the definition of ATM. This analysis makes reference to three different and complementary aspects, i.e. the multiplexing technique, the switching principle and the protocol architecture.

Then the current status of B‐ISDN is presented on the basis of the most recent results available from the standardization activity. In particular aichitectural aspects and traffic control issues are considered.
Broadband switching systems: First generation
Authors: Pattavina Achille
Published: September 2008

Several generations of switching systems for broadband networks have been developed in the eighties. This paper describes the structures, the properties and performance Of the first generation of such systems known as banyan interconnection networks. Three classes of these networks are examined, that is unbuffered networks, buffered networks with internal queueing and buffered networks with output quequeing.
Terminals and signal processing in atm networks
Authors: Modena Giulio
Published: September 2008

The paper presents the research topics of the «Progetto Finalizzato Telecomunicazio‐ni» partially founded by CNR (National Council for Research) on the multi‐media terminals, video broadcast terminal and HDTV (High Definition Television) signal processing. It describes the main features of a full ATM Workstation, of ISDN multiservice terminal and digital video broadcast codec connected to ATM node. It presents also the studies on HDTV by simulation of algorithm.
Coherent optical FSK transmission systems
Authors: Prati Giancarlo
Published: September 2008

Coherent optical systems are getting much closer to commercial realizations than expected only few years ago. Front‐running candidates for simplicity and effectiveness are FSK communication systems. Several reasons stand in favour of this system: most evident are direct modulation of semiconductor lasers, generation of two‐lobe spectrum or compact spectrum by simply setting the modulation index, possibility of envelope or discriminator detection, full compatibility with optical amplifiers due to constant optical envelope, direct application to subcar‐rier multiplexing with analog optical FM. In this paper we describe the basic FSK trasmission system, presenting the relative problems and illustrating possible different solutions for transmission and for the receiver, and concentrating on specific subsystems time by time, such as line coder, automatic frequency control, receiver balanced front‐end, post‐detection pre‐amplifier, discriminator and envelope detection, from both theoretical and implementation points of view.
Application of tricomi functions in the eigenvalue analysis of the circular gyrotropic waveguide
Authors: Ivanov Kamen P. , Georgiev Georgi N.
Published: September 2008

The complex Tricomi confluent hypergeometric functions Φ (a, c;x) are introduced as exact functions for propagation of normal TEommodes in circular guiding structures, containing coaxially positioned azimuthally magnetized ferrite layer of double‐connected cross‐section. An original form of characteristic equation of the ferrite‐fiiled coaxial waveguide is derived in terms of the arguments of Tricomi functions. Using the specially tabulated values of the latter, a numerical solution of this equation is accomplished, giving the eigenvalue spectrum and nonreciprocal phase characteristics of the structure. An analysis of its phase shifting capabilities is presented for a variety of geometry and ferrite parameters. The potentialities of the gyrotropic waveguide as digital nonreciprocal phaser, operating in theTE01mode, are discussed.
Space variant resolution ADCT still image coding
Authors: Imperato Mario Alessandro , Jacovitti Giovanni , Neri Alessandro
Published: September 2008

Starting from the principle that the distorsion measure, representing the cost payed by the users for lossy reproducing an image, takes its maxima in correspondence of local minima of Shannon's Entropy, a space variant resolution coding method matched to the local content of the image is presented. A fidelity criterion based on the estimated kurtosis function of the image is then applied to drive the quantization phase of an ADCT coder. Finally, an enhanced version of the ISO/CCITT hierarchical progressive transmission mode is proposed and its perfomance evaluated on the basis of reference images.
Digital computer simulation of synthetic aperture systems and images
Authors: Camporeale Claudio , Galati Gaspare
Published: September 2008

Digital computer simulation is a powerful tool for the design, the mission planning and the image quality analysis of advanced SAR Systems.

«End‐to‐end» simulators describe the whole process of the SAR imaging including the generation of the coherent echoes and their processing and allow, unlike the «product simulators», to evaluate the effects of the various impairments on the final image.

The main disadvantage of the «end‐to‐end» approach, as described in this paper, is the heavy computation burden; therefore, a new type of simulator is presented, attempting to reduce the burden but presenting a greater degree of completeness and realism than the SAR product simulators, already existing.

An «end‐to‐end» simulator and an «intermediate» simulator are described and analyzed, with emphasis on their architecture and performance.
Metropolitan area network planning and design
Authors: Capurro Mario , Coronaro Massimo , Giuli Dino
Published: September 2008

The subject of this paper is a planning methodology under development for application to broadband networks. The problem, faced and analysed in a general way, originates a sub‐problem of particular interest: the planning of MANs (Metropolitan Area Network). In particular the DQDB MAN, thanks to its architectural features constitutes the most promising solution in the short‐medium term in order to offer telecommunication broadband services, and represents a well‐located step in the evolution towards the B‐ISDN.

The MAN planning methodology is presented, with particular focus on some software tools developed for the solution of the main tasks involved in the methodology, which applies to all environments and situations of interest. In particular the methodology has been applied in the project of the experimental metropolitan network, to be implemented in the Florence area in the frame of the C.N.R. Telecommunication Project.
A new subaperture approach for real‐time SAR processing
Authors: Moreira Alberto
Published: September 2008

A novel, subaperture approach for high quality SAR processing has been developed at DLR. This approach is based on dividing the received SAR signal (range or azimuth direction) into small subapertures, allowing a quadratic phase variation of up to_ 115° within one subaperture. With a simple linear correction of the phase variation, the correlation process in each subaperture is reduced to an up/down frequency conversion followed by two moving average operations. By adding all the subapertures coherently, a high resolution impulse response function is obtained, which leads to the same image quality as with the conventional matched filter method. Due to the reduced amount of computation and the subaperture structure, this new approach is especially suitable for real‐time SAR processing while providing flexibility to multi‐look processing and auto‐focus. The concept of a high resolution real‐time SAR processor for the DLR's airborne E‐SAR system is discussed and a simulation result for evaluating the performance of the proposed algorithm is shown.
The node equation approach to wide band SAR image reconstruction
Authors: Hellsten Hans , Edberg Eva
Published: September 2008

As opposed to Fourier and associated integral methods for SAR processing, the paper discusses a method, based on the numerical unfolding of a differential equation along the synthetic aperture path. The method is a particular case of a general approach, which also may be applied to other synthetic aperture techniques, such as ISAR and btstatic imaging. The integration process may be termed cumulative, since a low resolution image available at a certain time along the synthetic aperture, together with the data registered at this moment of time, form the basis for constructing an image of successively improved resolution. The approach seems suitable for real time imaging, motion compensation, adaptive radar, and whenever continuous control over the imaging process is required. The paper considers application of the method to the extreme situation of ultra wide band, low frequency SAR. It is not as yet known how the method compares to the more conventional correlation methods, in the case of narrow band microwave SAR. The method is demonstrated by several numerical tests.
Real time SAR‐data processing: Parallelism and granularity illusions and possibilities
Authors: Lecce Vincenzo Di , Marino Diomede , Mastronardi Giuseppe
Published: September 2008

The problem of precision processing of SAR data in real time is here discussed, considering both a new performance evaluation model for structured algorithms and effective computational schemes of the SAR data compression process, in order to assess conditions of effective real time processing possibilities in this performance demanding application. Our analysis leads us to propose &fine grain architecture as a reasonable solution. Rigorous performance estimate is also provided for it. The single lowermost‐level processing element “ad hoc” designed by us, has been yet implemented in VLSI technology and is under test; it is suitable to work in very high granularity systems of bit‐sequential type (as “connectionist” architectures). Interconnection and data allocation policies, as well as possible process decomposition are also discussed.

Results of the present investigation are the basis of a joint research program we have started with the Italian Space Agency (ASI) at the CGS Laboratory (Spatial Geodesy Center) in Matera (Italy).
Vector implementation of synthetic aperture radar processing
Authors: Perna Antonio Di , Lanari Riccardo , Schirinzi Gilda
Published: September 2008

A vector computer implementation of a wide‐angle Synthetic Aperture Radar processor is presented. The choice of this architecture is convenient inasmuch Fast Fourier Transform codes and matrix multiplications can be efficiently implemented. Experiments and performance data of the processor are presented.
SAR application of a signal coding technique for single‐hit measurement of the target scattering matrix
Authors: Giuli Dino , Facheris Luca
Published: September 2008

A new technique for the simultaneous measurement of all the target scattering matrix elements, recently proposed for general application to polarimetric radars, is analyzed for specific application to a fully polarimetric SAR. With reference to a focused SAR, the new concept of homopolar and heteropolar generalized ambiguity functions is introduced to evaluate the performance of the proposed technique in the presence of distributed targets, comparing it with the performance of the conventional polarimetric measurement technique based on pulse‐to‐pulse polarization switching. The possibility of synthesizing the heteropolar ambiguity function by means of pulse‐to‐pulse coding in order to improve performance of the single‐hit measurement technique is also pointed out.
A workstation for SAR processing, simulation and image analysis
Authors: Eichenherr Harald , Faller Nikolaus P.
Published: September 2008

We describe a SAR data processing system comprising a SAR processor for image generation, a raw data simulator, and a set of image display and analysis tools. The system is implemented on a SUN workstation supported by a Mercury array processor. The applications range from routine off‐line SAR image generation to development and test of processing algorithms and SAR system simulation.
Rain attenuation predicted with a two‐layer rain model
Authors: Matricciani Emilio
Published: September 2008

The paper presents a new prediction model of rain attenuation in slant paths; it models the precipitation with two layers of constant vertical precipitation rate. The relationship between the rain‐rate in the first layer above the ground (layer A) and the apparent precipitation rate (defined in the paper) in the second layer (layer B, which models the melting layer) is theoretically derived: assuming a log‐normal probability distribution for the rain‐rate in layer A (measured at ground), the apparent rain‐rate in layer B is also log‐normal with the same standard deviation, but with its median value 3.134 times the median value of the ground rain‐rate. The rain‐rate statistical process in space is assumed to be also log‐normal with a correlation function determined from radar measurements. Assuming that the path attenuation (expressed in decibels) is also log‐normal, its average and standard deviation are then derived. The model is tested against the large CCIR data bank of slant path attenuation with or without concurrent rain‐rate, frequency ranges between 6 and 34.5 GHz, in the latitude range between 1.3 and 67.4 degrees. In the probability range 10−3‐10−3 the root mean square (RMS) log‐error of the Long Term data bank (single experiments of about 5 years) is about 26%, with average (<τ>) log‐error close to zero. For data banks of single experiments of shorter duration the RMS increases while <τ> decreases. The model is not significantly biased with attenuation, frequency of the experiment or latitude of the station. The distributions of the overall log‐error and that of the log‐error conditioned on given probabilities are both Gaussian. Sensitivity to different theoretical assumptions about the calculation of the specific attenuation kRα and to different numerical values of the snow density is also tested.
Study of on‐board digital FDM‐demultiplexing for mobile SCPC satellite communications
Authors: Göckler Heinz G. , Eyssele Helmut
Published: September 2008

Three different approaches to FDM demultiplexing applying digital signal processing are investigated for L0 = 32 slot signals: The single stage method (SSM), the polyphase method (PPM), and the hierarchical multistage method (HMM). All three approaches apply bandpass sampling and are based on the processing of complex signals by linear‐phase FIR filters, where the respective signals are always oversampled by a factor of two at any stage of processing. For the three methods all relevant design results are given including the required fixed‐point signal and coefficient wordlengths.

The HMM is the most efficient of the above approaches in terms of (bit) operation rate per channel, immediately followed by the PPM, while the SSM is less efficient by a factor of ten. Additional advantages claimed for the HMM are its high degree of modularity with the potential of optimization, ease of manufacturing and testing, suitability for VLSI realization, high reliability, and reduced amount of overhead circuitry.

This paper is published in two parts. Part I comprises the introduction, the front end issues common to all three approaches to FDM demultiplexing and the treatment of the SSM. In Part II the work on the PPM and the HMM is reported. Furthermore, all three approaches are compared with each other and a conclusion is given.
The CNR telecommunication project: An updated overview
Authors: Coiro Stefano , Esposito Antonio , Ripani Emilio , Roveri Aldo
Published: September 2008

An updated overview of the research activities carried out within the scopes of the CNR Telecommunication Project is given.

The main results of these activities are briefly described, with reference to the evolution of ISDN towards broadband capabilities, technologies for optical communications, terminal equipment and signal processing issues, access and switching techniques for an ATM environment and some experimental realizations of high speed networks.
The ATM shuffleout switching fabric: Design and implementation issues
Authors: Masetti Francesco , Pattavina Achille , Sironi Cesare
Published: September 2008

This paper describes the design and implementation aspects of the Shuffleout switch, a new class of switching fabric architectures. The key points of this structure are the adoption of a memoryless multistage interconnection network and a new packet routing strategy. Compared to the basic multistage shuffle interconnection network of Shuffleout, adopting 2×4 switching elements, three other architectures of the interconnection network are described, which use larger switching elements, that is 4×6, 3×5 and 4×8. Adopting these upgraded structures aims not only at decreasing the number of interconnection network stages that provide a given cell loss probability, thus reducing the switching fabric complexity, but also at improving fairness in the network. The VLSI hardware design of a switching element and of a chip is then described with reference to the basic Shuffleout structure, with design and implementation details on their major functional blocks. Finally a complexity comparison of the different enhanced architectures is assessed.
Analysis and properties of the modified constant modulus algorithm for blind equalization
Authors: Wesolowski Krzysztof
Published: September 2008

A modification of the Godard blind equalization criterion and algorithm is presented. The analysis of the proposed criterion is performed, showing that the corresponding cost function has four equivalent global minima. The original Godard algorithm and the proposed algorithm are compared by simulation of data transmission through telephone channels.
Digital multicarrier‐transmission of audio signals over mobile radio channels
Authors: Kammeyer Karl Dirk , Tuisel Ulrich , Schulze Henrik , Bochmann Harald
Published: September 2008

This paper presents a systematic overview over different concepts of multicarrier‐trans‐mission under the specific aspect of mobile radio transmission. It will be shown that under realistic multipath channel conditions the postulation of ideal bandwidth efficiency has to be given up. As a consequence sub‐optimum multicarrier concepts are regarded and mutually compared under the aspects of intersymbol interference and adjacent channel interference. A specific impuls shaping concept based on time and frequency concentrated impulses (Gaussian shaping) turns out as an appropriate solution since hereby the adjacent channel interference can be largely suppressed at the expense of a small increase in intersymbol inference. The performance of the different multicarrier concepts is illustrated by various simulation results under mobile radio channel conditions.
Concatenation of polarization dispersion in single‐mode fibers: A monte‐carlo simulation
Authors: Matera Francesco , Someda Carlo G.
Published: September 2008

We present a model for non‐ideal long single‐mode fiber links affected by polarization mode dispersion. It leads to simple expressions for the overall polarization delay and for the r.m.s. width of the impulse response, which entail systematic simulation on personal computers within reasonable CPU times.

Simulations show that the mean differential group delay and the double r.m.s. width of the impulse response coincide in such a way that both quantities can characterize the fiber polarization mode dispersion. In particular, both grow as the square root of the link length when the correlation length of the perturbation is much smaller then the fiber length. This confirms the results obtained by other authors under restrictive approximations.
Recursive techniques for the synthesis of a pth‐order inverse of a volterra system
Authors: Sarti Augusto , Pupolin Silvano
Published: September 2008

A new recursive technique for the synthesis of a pth‐order inverse of a Volterra system is presented. In such a method, the condition that the pth‐order inverse be exactly of order p, as proposed by Schetzen, is relaxed. The choice of the residuals, that is the operators of the inverse whose order is higher than p, is done with the purpose of reducing the complexity of the synthesis scheme and of deriving a recursive procedure to build‐up such an inverse.

A comparison between the complexity of Schetzen's synthesis schemes and those obtained with our recursive procedure shows that the structures that we obtain are much less complex and easier to derive, and the increment of complexity related to the increase in order is much slower than in Schetzen's case.

As an example of application, we use the proposed method in order to linearize a digital radio link in which the high‐power amplifier is operated near saturation.
A new definition of transmission network availability with applications
Authors: Barezzani Michele , Pupolin Alcatel‐Telettra Silvano , Zorzi Michele
Published: September 2008

The concept of transmission network availability is discussed and defined. On this basis, a method for measuring the transmission network availability is presented, along with its applications and usefulness to some networks.

The presence of privileged customers into the network enable us to compare preemptive vs. non‐preemptive mechanisms of using network redundancies. The effects of the mechanisms on network availability are discussed and compared.
Letter shortening of the settling time of digital IIR‐filters
Authors: Nagel Dieter , Wolf Günter
Published: September 2008

One of the most serious problems when using IIR‐Filters is the behaviour of the settling which depends on the incoming signal and the values which are in the state vector or memory of the filter. The description of the state vector is given in the z‐domain for the second direct form and for the cascaded structure. If the incoming signal is monochromatic, and when magnitude, phase and frequency are given or can be calculated, it is possible to determine the state vector (memory) of the filter in order that the settling time of a response to a step change of the monochromatic signal is zero. Various results are shown for one case when the preinitialization is done exactly with no noise present and for other cases when the monochromatic signal is overlaid by white noise.
Optical isolators for telecommunications: Review and current trends
Authors: Bendelli Giampaolo , Donati Silvano
Published: September 2008

We review the design of the state‐of‐the‐art of optical isolators intended for use in fiber optics communication systems. Special emphasis is given to the protection of narrow‐line, frequency stabilized lasers and of optical amplifiers. Finally, perspectives of future developments of OI's are discussed.
Models for ATM video packet transmission
Authors: Alparone L. , Argenti F. , Capriotti L. , Benelli G.
Published: September 2008

Broadband ISDN (B‐ISDN) offers new facilities for video transmission. Asynchronous Transfer Mode (ATM) is suitable for integrating different types of services (data, voice, video) and ensures a new flexibility of the network relatively to traffic control and resources utilization. As a drawback delays and losses of packets are to be considered. A basic step to valutate such performance parameters is the estimation of models of packet production of each data source contending network resources. In this paper a model, not strictly frame buffered, accounting of the bit rate generated by a compressed video source is proposed and its validity is assessed by fitting it to true bit rate data from a DCT video coder. Simulations of the modeled video source as input to an ATM multiplexer, together with other kinds of traffics, are presented to investigate the performance of the network.
A survey of applications of mathematical programming to circuit‐switched network planning problems
Authors: Craveirinha José , Clímaco Joó
Published: September 2008

In the planning of circuit‐switched networks the decisions regarding the capacity of transmission and switching equipments, the location of exchanges and the routing principles are of primary importance. Traditionally planning methods were based on heuristic type algorithms using sometimes simple mathematical programming algorithms for particular sub‐problems. However in the 70's and 80's, new approaches based on mathematical programming algorithms (namely non‐linear programming, integer programming and dynamic programming algorithms) have been put forward for solving some key telecommunication network planning problems.

The main objective of the paper is to identify the main characteristics of problems where mathematical programming has been applied (in the context of circuit‐switched network planning) and referring to relevant works in these areas. A system of taxonomic classification of circuit‐switched network planning problems is proposed and applied to an extensive list of relevant publications complemented with a list of correlated papers and other publications. The core of the overview of contributions, presented in the paper, will be limited to models of operational planning of circuit‐switched networks. Finally the authors, based on their own experience in specific problems, will try to put forward some general conclusions of a broad methodological nature.
A New Approach to Multipulse Speech Coding
Authors: Docampo Domingo , Abreu Victoria , González Francisco
Published: September 2008

This paper introduces a new approach to classical Multipulse Speech Coding. Based on spiky deconvolution techniques, which take advantage of the sparse character of the multipulse sequence, a new accurate scheme for generating the excitation sequence in multipulse coders is presented and analyzed. Using different quantization procedures, we propose a multipulse coder that can be adjusted to work within bit rates ranging from 4.8 to 9.1 kbit/s. The performance and computational burden of the new coder are also evaluated.