bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metropolitan area network planning and design
Authors: Capurro Mario , Coronaro Massimo , Giuli Dino 
Published: September 2008

AbstractThe 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

AbstractA 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

AbstractAs 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

AbstractThe 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

AbstractA 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

AbstractA 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

AbstractWe 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

AbstractThe 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

AbstractThree 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

AbstractAn 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

AbstractThis 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.
Digital multicarrier‐transmission of audio signals over mobile radio channels
Authors: Kammeyer Karl Dirk , Tuisel Ulrich , Schulze Henrik , Bochmann Harald 
Published: September 2008

AbstractThis 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

AbstractWe 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

AbstractA 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

AbstractThe 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

AbstractOne 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

AbstractWe 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

AbstractBroadband 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

AbstractIn 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

AbstractThis 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.
Letter: Cross Section Computation of Trihedral Corner Reflectors with the Geometrical Optics Approximation
Authors: Groot Jos 
Published: September 2008

AbstractA Monte Carlo type numerical method based upon the geometrical optics (GO) approximation to compute the monostatic radar cross section of trihedral corner reflectors is introduced. Advantages of the method are its simplicity and the possibility to use it for the most complex reflector shapes. Disadvantage is its slow convergence as a function of the number N of rays involved, and hence the amount of computer time needed. Comparison of numerical with experimental and GO analytical results for the often used triangular and square‐based reflectors confirm the validity of the numerical method. The analytical results presented are valid for a wider angular range than those given in the most commonly used literature.The method was utilized in the problem of finding a reflector shape exhibiting a relatively flat angular RCS pattern. The pattern of the resulting optimal reflector varies less than approximately I dBm2 within a region of about ±25° ‐ 30° around boresight. For the most commonly used triangular reflector this region is only about ±10° ‐ 15° wide.
Noise Prediction Equalizer and Decision Feedback Equalizer for High Speed Digital Subscriber Line Transmission ‐ A Comparison of Performance
Authors: Ernst Detlef 
Published: September 2008

AbstractA new equalizer structure, the noise prediction equalizer, was recently proposed in the literature, especially for applications in high speed digital subscriber line transmission systems. It consists of a decision feedback equalizer and an additional noise prediction filter. The calculation of its optimum tap weights in the mean square error sense yields a nonlinear system of equations, that can be solved by approximation in two different ways. The characteristics of the transmission channel and the additive noise determine which method yields the smaller mean square error. Even without approximations the minimum mean square error of the noise prediction equalizer exceeds that of a decision feedback equalizer with filters of equivalent lengths. In addition the noise prediction equalizer offers almost no advantage in comparison with the decision feedback equalizer for the adaptive filter adjustment.
Distributed Routing Techniques for Internally Unbuffered Interconnection Networks
Authors: Ferrari Gianfranco , Lenti Marco , Pattavina Achille 
Published: September 2008

AbstractThis paper deals with techniques for improving the performance of unbuffered banyan networks adopted in a switching fabric of a broadband packet switching network. We propose an arrangement of parallel banyan networks provided with output buffers that enables more than one packet to reach an output interface of the switch. Different solutions for the packet distribution to the banyan networks of the stack are investigated and the corresponding traffic performance is evaluated. Two types of packet addressing patterns are considered, depending on how many packets are allowed to address each switch outlet. The results obtained prove that a significant reduction in packet loss probability is possible with respect to a simple banyan network.