bluuebunny/crossref_metadata_2025_split huggingface dataset:
Prediction of the outage performance of an orbital diversity earth‐space system
Authors: Kanellopoulos John D. , Reppas Adrianos 
Published: September 2008

AbstractDiversity systems are foreseen for earth to satellite links operating at frequencies above 10 GHz in localities with high rain‐induced attenuation. The paper discusses orbital diversity, which uses two satellites and an earth receiving site. A recently suggested model for the prediction of site diversity performance is properly modified by considering the particular geometry of the present problem. Both types of rain (stratified and convective raincells) are also examined. Numerical results are compared with experimental data taken from a simulated earth‐space system located in Italy. The agreement was found to be quite encouraging.
Signal detection in cyclostationary generalized gaussian noise with unknown parameters
Authors: Napolitano Antonio , Paura Luigi , Tanda Mario 
Published: September 2008

AbstractThe paper deals with the detection of a known signal embedded in cyclostationary white generalized Gaussian noise. Two cases are considered: the former assumes unknown (but nonrandom) the periodic noise intensity, the latter considers unknown also the noise‐shape parameter. Since for these detection problems non uniformly most powerful test exists, the generalized log‐likelihood ratio test (GLLRT) is considered because of its asymptotic optimality properties. The GLLRT‐based detectors for both cases are synthesized and their asymptotic (i.e., for large sample size) performances are analytically evaluated. Moreover, for finite sample size, the performances, carried out via computer Monte Carlo simulations, are compared with that of the optimum detector, whose synthesis is based on a complete noise characterization.
TCP/IP measured performance over an ethernet local network
Authors: Braccini Alessandro , Bimbo Alberto Del , Vicario Enrico , Cappellini Vito 
Published: September 2008

AbstractBoth a reliable transfer and a datagram transmission protocol are provided at the transport level of the Internet protocol suite. In this paper, an evaluation of the performance of these different protocols in the presence of background load is presented. The experimental analysis was carried out on an Ethernet Local Area Network with PC‐type workstations. The loading conditions were established by means of an artificial traffic generator. A reproducible experimental environment and a methodology to achieve accuracy in measurements were developed.
Signal processing for broadband communications
Authors: Bellanger Maurice 
Published: September 2008

AbstractSignal processing affects all aspects of broadband communications: terminals, transmission media and networking techniques. In this context, the paper provides a review of several basic signal processing concepts, which can now be implemented and exploited, with the present technological capabilities: perfect filter banks, fast adaptive filtering and code representation. These are key elements for a smooth introduction and evolution of the broadband communication network.
ASIC‐based acoustic echo‐canceller board for VME bus
Authors: Maloberti Franco , Torelli Guido , Panini Claudio , Troiani Mauro , Roncella Roberto , Terreni Pierangelo , Toncelli Cristiano , Saletti Roberto 
Published: September 2008

AbstractThis paper deals with the design and realization of an echo‐canceller board for a VME bus. The work has been carried out by integrating the abilities and the competences of some academic and industrial research groups within the framework of Subproject 3.1 of the Italian National Research Council «Telecommunication Project». The board implements an efficient algorithm for the cancellation of acoustic echoes and is to be used in a video‐conference terminal. It employes application specific integrated circuits (ASIC), in order to obtain a compact realization of the system, as required in present inter‐personal terminal systems. The board consists of a DSP processor which computes the algorithm, a high‐performance interface with the analog world, and a finite impulse response filter (FIR) which emulates the response of the acoustic channel. The design and the performance of the integrated circuits for the A/D and D/A conversion and the FIR filter are reported.
VQ coding for videophone applications adopting knowledge‐based techniques: Implementation on parallel architectures
Authors: Braccini Carlo , Grattarola Aldo , Lavagetto Fabio , Zappatore Sandro 
Published: September 2008

AbstractAn innovative algorithm is presented for the design and implementation of a self‐adaptive vector quantizer for videophone coding. The codebook is organized in a binary tree structure capable to modify its topology and content in order to adaptively track the input varying statistics. The resulting tree structure is unbalanced, in the sense that some branches are extended more than others, depending on the input vector distribution, and therefore the suboptimality of tree structured VQ with respect to the full‐search approach is greatly reduced. As it is known a priori that the class of input video data consists of a human head slowly moving against a static background, knowledge based segmentation of incoming frames can be efficiently performed. Exhaustive simulations have shown the effectiveness of the algorithm in standard CIF videophone sequences. Some procedures have been parallelized and implemented on a AT&T Pixel Machine for frame‐rate coding. Results and comments on both the algorithm and the parallel implementation are presented.
Signalling protocols for multimedia application: Prototype for an ATM test‐bed
Authors: Contini Enzo , Piovano Luciano , Ravera Mauro 
Published: September 2008

AbstractCurrently under study as part of the future ATM based communication network definition is the development of a flexible signalling system. This document shows how the signalling protocol prototype at the User to Network Interface was defined in an ATM test‐bed. Taking Rec.Q.931 as a starting point, we introduced into the new signalling protocol structure the concept of Call Control and Bearer Control separation thus making it possible to handle multiconnection and multiparty call configurations in an easy way.To satisfy the new signalling requirements, a flexible description of the telecommunication service is proposed. Each information type is described individually and the relationships among them is outlined. In addition this paper proposes a matrix‐based description of the call model, particularly useful for the introduction of multiparty configurations.The paper then recalls the advantages of the Call Control and Bearer Control separation concept, and goes on to analyze a number of identifiers whose function, in this context, is to correlate the Call Control entity with those of Bearer Control. As an example, we give various messages of this signalling prototype protocol: their structure is based on the tools and identifiers described above.
Deflection network: Principles, implementation, services
Authors: Albertengo Guido , Civera Pier Luigi , Cigno Renato Lo , Piccinini Gianluca , Zamboni Maurizio , Borgonovo Flaminio , Fratta Luigi , Panizzardi Giuseppe 
Published: September 2008

AbstractThis paper deals with slotted data networks routing packets with a deflection technique. In particular regular mesh topologies that can be mapped on toroidal surfaces are analyzed. First an introduction to the concept of deflection routing is given, then many routing algorithms are considered and compared by means of their performance in terms of maximum attainable throughput and efficiency. Afterwards the architecture of a node currently under development, which implements one of the described algorithms, is described and analyzed; the switching fabric, a full custom VLSI, the interface of the node towards LANs and workstations, and the network management algorithm are described in detail. Finally the possibility of providing special services, like guaranteed bandwidth, circuit oriented connections, etc. is taken into account.
Guaranteed bandwidth transport service in multihop networks
Authors: Bernabei Francesco , Gratta Laura , Listanti Marco 
Published: September 2008

AbstractThis paper deals with the feasibility of a Guaranteed Bandwidth Transport Service (GBTS), usually employed for the handling of isochronous and/or data services with real time requirements, on Multihop Networks (MHNs). A Resource Allocation Protocol (RAP) for the set‐up of GB calls is proposed. This protocol allows the low cost requirements of a LAN/MAN node to be satisfied, together with a high flexibility in bandwidth allocation. In the paper a performance study is carried out to verify the response of the MHNs to GB traffic. In particular, the path blocking probability has been evaluated by means of an analytical model in the cases of balanced and unbalanced loads. Moreover, a comparison with the performance of similar LAN/MAN structures, i.e. simple ring and ring with spatial reuse is carried out. Finally, a methodology to manage the resources in order to make the grade of service independent of the physical location of the network nodes is proposed and its impact on the network performance is evaluated.
Bit error probability of a digital mobile radio cellular system in presence of co‐channel interference, thermal and impulsive noise
Authors: Prasad Ramjee , Hollemans Willem , Kegel Adriaan 
Published: September 2008

AbstractThe bit error probability is derived for a mobile cellular radio network in the presence of co‐channel interference, Gaussian noise and narrow‐band impulsive noise (Middleton's class A noise) using DPSK (differential phase shift keying) modulation and 4‐QAM (quadrature amplitude modulation). The spectrum efficiency of the mobile radio system is also evaluated. The influence of reuse distance, i.e. cluster size, and traffic intensity on the performance parameters is investigated. The mobile environment is considered as a (fast) Rayleigh fading channel.The UHF groundwave propagation law is introduced by considering the local mean power to be inversely propotional to the fourth power of the propagation distance.It is found that the bit error probability is more vulnerable to Gaussian white noise than to narrow‐band impulsive noise.
Orthogonal multiple carrier data transmission
Authors: Fliege Norbert J. 
Published: September 2008

AbstractIn this paper, the idea of data transmission by essentially using the discrete Fourier transform (DFT) algorithm, the idea of overlapped but orthogonally sampled multiple data transmission channels, and the idea of subband signal processing by means of DFT polyphase filter banks are combined. The main result in a novel orthogonal multiple carrier (OMC) data transmission system with high computational efficiency and high bandwidth efficiency.Intersymbol interference is avoided by choosing each channel as a Nyquist system. The problem of unavoidable crosstalk between adjacent channels is solved by sampling the equally spaced zeros of the crosstalk impulse response. It is shown that in a critically sampled DFT filter bank the space between the zeros exactly equals one symbol period. The time offset of half a symbol period between the zeros of the real part and the zeros of the imaginary part of the crosstalk impulse response leads to a special staggering technique with time offset. Finally the structure of the polyphase filter banks is optimized resulting in fast Fourier transforms of half of the original length.
Image compression by the wavelet decomposition
Authors: Albanesi M. G. , De Lotto I. , Carrioli L. 
Published: September 2008

AbstractDecomposition of images with the Haar orthonormal basis which is an important member of compactly supported Wavelets and a quadtree structured hierarchical coding technique are used in this work to obtain high image compression efficiency and time complexity linear in the number of pixels. An exhaustive testing of the algorithm has been performed on images of different complexity and typical of some application environment (image transmission and storing, remote control of intelligent robots). The results of the experiments arc presented and discussed. Finally, a comparison of quality performance of these techniques with the JPEG (Block Cosine Transform coding) compression technique is presented.
Further applications of the optimal strategy srpt to media access protocols in local area networks
Authors: Schmickler Leonhard 
Published: September 2008

AbstractAfter a recently reported application of the SRPT principle to the Ethernet LAN based on the CSMA/CD access protocol we present in this paper further SRPT applications to the token passing LANs Token Bus, Token Ring and the FDDI high speed LAN. Messages are sorted in the station transmit queues according to their length and transmitted over the network using the standardized priority classes to prefer short messages. It will be shown that under a typical user scenario the mean value as well as the standard deviation and the correlation of the transfer time are remarkably reduced compared to FIFO operation.
Performance analysis of differential chain coding
Authors: Liu Kun , Prasad Ramjee 
Published: September 2008

AbstractChain coding of hardwritten line drawings for digital transmission is considered in this paper. A line drawing is considered to be composed of unconstrained two‐dimensional open and closed thin curves. Each curve is quantized in line‐following fashion into a sequence of discrete links, i.e., the chain‐code representation. Chain quantization based on grid‐intersect quantization (GIQ) and object boundary quantization (OBQ) is considered. Their performance in terms of the quantization distortion is quantitatively analyzed. To reduce the amount of data required to represent a line drawing, differential chain coding (DCC) is used to convert the chain code of a line drawing into binary data. The performance of DCC in terms of the number of bits required per unit length of curve is analyzed. The tradeoff between quantization distortion and coding efficiency for DCC is determined.
A comparison of coherent digital PPM with PCM
Authors: Cryan Robert A. , Unwin Rodney T. , Massarella Alistair J. , Sibley Martin J. N. , Garrett Ian 
Published: September 2008

AbstractDigital pulse position modulation (PPM) is a preferred modulation format for the ideal photon counting channel and optical intersateilite links. Here we examine its potential for the coherent optical fibre communications channel. We present a thorough performance and optimisation analysis. Comparisons, at a wavelength of 1.5 μm, are made with shot‐noise limited coherent PCM (homodyne and heterodyne ASK, FSK and PSK) over a range of fibre band‐widths and varying PPM word size. We conclude that for moderate to high fibre bandwidths homodyne digital PPM should achieve an improvement in sensitivity of typically 5 dB over homo‐dyne PSK PCM.
Adaptive DCT for image‐data compression
Authors: De Natale Francesco G. B. , Desoli Giuseppe S. , Giusto Daniele D. , Vernazza Gianni 
Published: September 2008

AbstractThis paper deals with the development of a coding system for image data compression based on the Discrete Cosine Transform (DCT). The aim is to integrate several methods into a single approach in order to obtain an adaptive coder characterized by higher performances. In particular, a variable blocksize scheme is used, which is based on quadtree segmentation driven by edge information. To improve data compression, DCT coefficients are then coded by a vector quantizer.Experiments have shown that the values of compression factors can be notably increased, while maintaining a good reconstruction quality.
An abstract representation of the scalar wave equation of optics
Authors: Kragl Hans 
Published: September 2008

AbstractBased on the time ‐ dependent, lossless scalar wave equation interior losses and radiation losses are introduced by a dissipation function. This method is well ‐ known from classical mechanics. To illustrate the mathematical procedure all aspects are studied by a mechanical system analogous to the optical wave field. Finally, the results are transferred to optics. By this means the physical meaning of the lossy operators that correspond to the operators E and HF of the lossless wave equation, becomes clear. These lossy operators are no longer self ‐ adjoint and as a consequence, there is no action integral for the lossy equation but only a more general variational functional. Three examples and a discussion of the necessary approximations to be made conclude the subject.
A calculated distribution for attenuation due to atmospheric absorption in the millimeter wave range
Authors: Bernardini Angelo , Pattuelli Riccardo , Pescosolido Luca , Boumis Marina 
Published: September 2008

AbstractBased on the Liebe's model for the atmospheric absorption dependance on temperature, relative humidity and pressure, a statistical distribution of absorption for seven Italian cities is calculated from data collected over a six years period. Results are statistically analyzed and relevant issues such as climatic dependence and time variability are investigated.
On the need for integrated approaches to image understanding
Authors: Moneta Carlo , Vernazza Gianni , Zunino Rodolfo 
Published: September 2008

AbstractKnowledge‐Based (K‐B) approaches to Computer Vision seem to have come to a stalemate, due to difficulties inherent in performing crucial activities, e.g., autonomous refinement of the embedded high‐level knowledge and time‐consuming low‐level processing. In the paper, the problem is related to a broader class of issues, and the conclusion is drawn that no individual method can be regarded as a unique and comprehensive paradigm for Computer Vision. A possible solution to this problem might lie in combining different methodologies to enhance mutual advantages and to balance individual shortcomings; K‐B vision approaches are reviewed here from this integration‐oriented perspective. Higher‐level integration should aim at improving 'intelligent' activities of K‐B systems; Machine Learning approaches to Vision are discussed from this point of view, Lower‐level integration should provide K‐B systems with the fast number‐crunching capability and robustness required; the use of neural networks and of associative memories is evaluated for this purpose. All such methodologies are reviewed, taking into account both their intrinsic peculiarities and the specific problems that may arise from coupling them with K‐B vision systems. The paper aims at providing an updated and critical picture of some lines of research that are currently being pursued to achieve an efficient integration of K‐B techniques into complex vision systems.
Comparison of TP4, TCP and XTP Part 1: Connection management mechanisms
Authors: Baguette Yves , Danthine André 
Published: September 2008

AbstractThis paper is the first part of a comparative study of the transport mechanisms of three protocols: ISO TP4, XTP and, to a lesser extent, DARPA TCP. This first part focuses exclusively on the connection management (i.e. connection set‐up and release) mechanisms. The mechanisms used during the phase of data transfer over a connection will be analysed in the companion paper. The goal of the comparison of the connection management mechanisms is to determine the suitability of each of the three protocols assuming that they operate in HSLANs environments characterized by high performance but also, possibly, by a wide range of application requirements as regards the types of communications to provide. This paper takes account of the very last Revision 3.6 of XTP and of the upgraded version of the ISO Transport Protocol which has been circulated for ballot as Draft International Standard (DIS) 8073.
Towards Full Communication Through Multimedia Personal Terminals
Authors: Abdat Mourad , Bellanger Maurice 
Published: September 2008

AbstractMultimedia personal terminals are key elements in the full communication process. Basically, they have to efficiently encode multimedia signals and interconnect through transmission networks. The paper gives an up‐to‐date overview of the standards which are involved in both functions, emphasizing the still and moving picture standards, JPEG, JBIG, MPEG, and networks with a definite multimedia orientation, ISDN and IVDLAN. Finally, several issues are raised, which are important for the future impact of multimedia personal terminals.
Multisensor High‐Performance Terminal for Indoor Infrared Cellular Network
Authors: Castanié Francis , Roviras Daniel , Sala Alain , Ayache Alain , Carmona Cesar , Puech Philippe 
Published: September 2008

AbstractThis communication describes the High‐Performance Terminal of the ESPRIT II Factory Customer Premise Network project. In the first section, a brief description of the network architecture is given, showing the function of this terminal. It is shown that it is expected to integrate Audio‐Signal Processing up to the level of the automatic recognition of acoustic signatures, and Image processing up to feature extraction and image compression. The second section is devoted to the description of the signal processing algorithms, together with some relevant results of the recognition procedure. The third section gives an insight of the image processing algorithms, with a special attention paid to their 3‐D capability.
An Optical Flow Algorithm Preserving Motion Boundaries and its Parallel Implementation
Authors: Bartolini Franco , Cappellini Vito , Mecocci Alessandro 
Published: September 2008

AbstractOne of the main techniques for the analysis of image sequences is the optical flow computation. The optical flow is a vector field representing the apparent motion, on the image, of the projected points of the objects in the scene. Many algorithms have been developed to compute the optical flow. In this paper one of these algorithms is reviewed, the performance enhanced and a possible parallel implementation presented. The main advantage of the resulting algorithm is its good behavior in presence of noise or motion boundaries; this is obtained by means of a local technique which doesn't require global optimization and by applying a median filter to restore the vector field. Furthermore a pyramidal approach is used to increase the range of interframe displacements computable by the algorithm. To enhance the time performance a parallel implementation on a network of transputers has been studied; a theoretical analysis of the efficiency of the implemented architecture is discussed and its agreement with the experimental results is reported.
Autoassociative Neural Networks for Image Compression
Authors: Basso Andrea , Kunt Murat 
Published: September 2008

AbstractIn this paper a neural autoassociative technique applied to image compression is presented. Particular attention is devoted to the preprocessing stage. The validity of some of the already established theoretical results is discussed and an experimental study of the mapping capabilities of the network based on a nonlinear parametrized activation function is presented. In order to test the image reconstruction capabilities of the neural technique, comparisons with more traditional image processing tools such as Karhunen‐Loeve Transform (KLT) are shown. A massively parallel implementation of a linear version of the neural technique on the Associative String Processor (ASP) machine is presented. Despite the linear structure of the ASP and the use of fixed arithmetic for the implementation, promising results are shown in terms of learning speed (of the order of 109connections per second) and quality of the reconstructed images.