bluuebunny/crossref_metadata_2025_split huggingface dataset:
Using different spatial scale measurements in a geostatistically based approach for mapping atmospheric nitrogen dioxide concentrations. Application to the French Centre region
Authors: Malherbe Laure , Cárdenas Giovanni , Colin Patrice , Yahyaoui Abderrazak 
Published: September 2008

AbstractPassive sampling surveys followed by geostatistical data analysis have become a common and efficient approach for mapping background concentrations at regional and urban scales. Traffic‐related pollution is also a matter of concern as regards population exposure but since it acts at shorter spatiotemporal scales, it is usually not integrated in the same maps. However, to provide more comprehensive information to the authorities and the public, the agencies responsible for air quality monitoring are searching for innovative ways of representing background and roadside concentrations together. A methodology based on geostatistics and the examination of the relationships between seasonal nitrogen dioxide concentrations and auxiliary variables is proposed in this study. It is applied to data collected in the French Centre region. Copyright © 2008 John Wiley & Sons, Ltd.
A numerical approach to electromagnetic dosimetry for the human body
Authors: Caorsi Salvatore , Gragnani Gian Luigi , Pastorino Matteo 
Published: September 2008

AbstractThe quantitative evaluation of the human hazard due to exposure to nonionizing radiation requires the estimation of the em. absorption by the various tissues of the human body. In this paper, a numerical method is proposed, which can be used to predict the distribution of electromagnetic absorption inside the human body (simulated by a 3D block model consisting of variable‐sized cells). Electromagnetic scattering is studied, taking into account the mutual coupling between the source (i.e., an antenna) and the body. A moment‐method formulation is adopted to reduce to matrix form the well‐known integro‐differential equation of direct electromagnetic scattering and the equations of the boundary conditions of the electromagnetic source. A domain decomposition is performed that allows one to use limited computational resources and to perform an off‐line evaluation of the invariant model portions. Simulations results are reported, concerning the block model of a standard man (175 cm tall) made up of 450 cells and exposed to the aperture antenna. The abdominal region is considered in more detail. Such results are compared with those obtained under plane‐wave exposure of a two‐dimensional cylindrical model.
On Lattice Coding for the Gaussian Channel
Authors: Oliveira Hélio Magalhäes De , Battail Gérard 
Published: September 2008

AbstractThe definition and basic properties of lattice codes for the Gaussian channel are first recalled. Then, an estimation of the code rate and bounds on the error probability are presented. Lattice codes are shown to exit which reach the channel capacity. Separate coding and shape gains are introduced. Finally, the asymptotic behaviour of lattice codes is examined and we are led to conjecture that achieving capacity is a covering ‐ rather than packing ‐ problem.
Joint Carrier Phase Estimation and Symbol Decoding of Trellis Codes
Authors: Kaleh Ghassan Kawas 
Published: September 2008

AbstractWe use the Expectation‐Maximization algorithm to deduce an iterative method for carrier phase estimation and symbol decoding. The method applies to all trellis‐based codes. Carrier phase offset and noise variance estimation is based on the maximum likelihood criterion. The Markovian properties of the encoder state sequence enable us to calculate the required likelihoods using a forward‐backward algorithm. Given the phase estimate, the calculated likelihood functions can easily give optimum decisions on information symbols which minimize the symbol error probability. Simulation results which show rapid convergence are given.
A Self‐Routing Packet Network Via Optical Processing of the Header
Authors: Davidson A. C. , Chaudhuri S. K. 
Published: September 2008

AbstractThe speed limitations of optoelectronic conversions and electronic signal processing for routing control in a packet network restrict the usable bandwidth of a fiber optic channel to well below its full potential. By keeping the signal in optical form and using optical signal processing, it is possible to remove the electronic bottleneck and utilize the untapped bandwidth of fiber optics. Furthermore, fiber optics facilitates the use of bandwidth expansion techniques, such as wavelength division multiplexing, to simplify network design.To allow multiple users access to a high speed optical channel, a new scheme, given the name code‐division header recognition (CDHR), is devised that uses both frequency ‐ and time‐domain bandwidth expansion as well as optical signal processing. An encoded destination address for a data packet is transmitted on a low speed subchannel at a different wavelength from a high speed main channel and optical delay‐line correlators are used for packet routing. The CDHR receivers are used to form a ring network which is then analyzed at the physical layer and the data link layer, specifically the media access control, of tiie OSI network model.
Harmonic and Intermodulation Owing to Nonuniform Quantization
Authors: Abuelma'atti Muhammad Taher 
Published: September 2008

AbstractBy representing the nonuniform quantizer characteristic by an infinite Fourier series, new, computationally simple, analytical expressions for predicting the harmonic and intermodulation performance of nonuniform quantizers are presented. Using these expressions nonuniform quantizer characteristics can be tailored to maintain predetermined maximum intermodulation levels under any scenario of input signals.
The pairwise error probability for decoding a convolutionally encoded sequence using integer metrics
Authors: Goldman Haim 
Published: September 2008

AbstractThe performance of a communication system that operates over a binary‐input, output‐symmetric memoryless channel and employs a convolutional error correcting code is usually evaluated by applying the union bound to the node error and the bit error probabilities. These bounds depend on the probability that an incorrect path on the code trellis accumulates a larger metric than the correct path. The paper presents an easy method to compute this pairwise error probability that is applicable to the significant case of a Viterbi decoder that uses a finite set of integer branch metrics.
Joint evaluation of time and frequency selective fading effects in CPM systems with LDI detection
Authors: Verdone Roberto 
Published: September 2008

AbstractLimiter ‐ discriminator ‐ integrator (LDI) detection of binary full and partial response continuous‐phase modulation (CPM) in a channel characterised by Rayleigh fading, time and frequency selectivity, is investigated. An analytical approach able to take into account the presence of any number of delayed paths in the channel is presented. The narrowband bandpass filter effects and the role of the post‐detection integration time and other system parameters are evaluated. The numerical results show that full‐response schemes perform better than partial‐response modulation formats as regards the error floor due to the Doppler effect or the presence of a delayed version of the received signal.
Image processing activities in RACE projects: An overview
Authors: Badiqué Eric 
Published: September 2008

AbstractImage Processing (IP) activities within the European Union RACE (Research in Advanced Communications in Europe) Programme are primarily oriented towards image coding which can be duly considered as the most striking success of IP yet. But other IP‐related areas essential to the deployment of advanced communications are equally well covered such as image generation, manipulation, segmentation, interpretation and modelling. Intelligent IP techniques, which can range from a simple signal‐adaptive filter to a complete scene analysis prior to model‐based coding, are increasingly being introduced and their potential recognised. Within the emerging ACTS (Advanced Communications Technology and Services) Programme, they will become common place and contribute to achieving high‐quality, flexible and ubiquitous communications evolving towards full virtual presence services.
Performance of phase‐detector receivers for coded BPSK and QPSK communication
Authors: Goldman Haim 
Published: September 2008

AbstractThe paper analyses the performance of phase‐detector receivers for soft decision demodulation of coded BPSK and QPSK communication. In these receivers the received signal is passed through a hard limiter and the information is extracted from the signal's phase only. The performance criteria are cutoff rates that are computed for both maximum likelihood receivers and practical receivers that use a finite set of integer metrics. For the latter type, the optimal partition parameters of the phase circle are computed. The performance of the analysed receivers is compared with the performance of the optimal coherent BPSK receiver. It is found that the reliance on the phase only for extraction of information induces a small performance degradation in BPSK and a considerable degradation in QPSK. It is also found that the performance of the phase‐detector QPSK receiver that demodulates the two quadrature branches independently is similar to the performance of the optimal phase‐detector QPSK receiv2r.
Fast small‐kernel K‐nearest neighbour noise‐smoothing algorithm
Authors: Mitchell Harvey B. 
Published: September 2008

AbstractA basic operation in image processing is the removal of noise from a noise‐corrupted input picture. The Af‐nearest neighbour (KNN) is a very effective noise‐smoothing filter: it removes both additive and multiplicative noise without blurring the edges and lines in the input picture. The main drawback to this filter is its high computational complexity. In this paper, the author describes a fast algorithm specifically designed for the small‐kernel KNN filter. The computational complexity of the new algorithm is sufficiently low to facilitate real‐time noise‐smoothing.
The adoption of optical systems: An econometric cost model of the european telecommunications carriers
Authors: Garrone Paola 
Published: September 2008

AbstractFollowing the mainstream applied economic literature on the production structure of the telecommunications (TLC) carriers, the paper provides an econometric estimation of the overall effects of the adoption of optical systems in junction and trunk network on the aggregate long‐run costs of the existing TLC European carriers. The analysis uses data from 16 European carriers over the 1980–'92 period. The optical systems are shown to have significantly reduced the costs of the European carriers. Firms operating non‐rural and high density areas have benefited especially from the adoption of optical systems. In addition, the efficiency gain related to fibre optic lines turns out to be cumulative.
FH‐SSMA with Band‐efficient modulations over cellular fading channels
Authors: Correia Americo M. C. , Albuquerque Augusto A. 
Published: September 2008

AbstractWe present frequency hopped spread‐spectrum multiple‐access (FH‐SSMA) employing bandwidth‐efficient modulations that are phase‐continuous during each hop. The particular cases of minimum‐shift keying (MSK), and Gaussian minimum‐shift keying (GMSK) are studied in detail. Noncoherent sequence estimation on a hop‐by‐hop basis is considered. System performance has been evaluated in selective Rayleigh fading with additive white Gaussian noise (AWGN) and the presence of multiple‐access cellular interference. This system performance is better than the performance of FH‐SSMA with noncoherent binary FSK modulation. The effects of power control, different fading covariance functions and different power bandwidth definitions are investigated.
DS‐SSMA capacity for a mobile satellite system
Authors: Bartucca Francesco , Biglieri Ezio 
Published: September 2008

AbstractWe consider a cellular satellite system conceived to enhance the capabilities of the pan‐European terrestrial system (GSM). This adopts EHF band and highly‐inclined orbits. We present a preliminary assessment of system capacity based on asynchronous direct‐sequence spread‐spectrum multiple access (DS‐SSMA). Performance is measured in terms of error probability achieved by K users simultaneously accessing the system with a given signal‐to‐noise ratio.
Suboptimal, partially coherent detection over multipath/multichannel rayleigh fading
Authors: Abdel‐Ghaffar Hisham S. , Pasupathy Subbarayan 
Published: September 2008

AbstractPartially coherent detection is studied as a problem of detection over diversity channels with unknown amplitudes, and known or perfectly estimated phases. The optimum composite hypothesis receiver is derived for binary, uniformly orthogonal signaling. Because of the high corn plexity of this optimum receiver, two suboptimal structures are considered a Linear equal gain combiner (LEGC) receiver and a quadratic coherent combiner, which is also a generalized likelihood ratio test (GLRT) receiver for this case. We examine the combiner output signal‐to‐noise ratio (SNR) for the two suboptimal receivers and show that this measure cannot be a performance comparison criterion for receivers of different orders. The exact performance of the GLRT receiver is evaluated in terms of the conditional, average and asymptotic bit error rates (BER), and graphical results are presented. An interesting result is that these BER expressions are obtained, for even and odd diversity orders, via different routes and that quadratic noncoherent detection represents a degenerate case of quadratic coherent detection with even diversity. The average BER of LEGC is exactly evaluated for dual diversity. LEGC and quadratic coherent combining are compared with respect to the asymptotic BEA and the exact BER for dual diversity. It is shown that LEGC is better in terms of the average BER in fading, while quadratic coherent combining is conditionally better whenever the signals received over different links have significantly different strengths.
Letter: On the capacity of the binary input gaussian and rayleigh fading channels
Authors: Taricco Giorgio 
Published: September 2008

AbstractA class of binary‐input discrete‐time channels with symmetric distribution of the output with respect to the input is considered and the channel capacity is analytically evaluated. The Gaussian and Rayleigh fading channel belong to this class and their capacities are numerically obtained for different quantization of the output. The asymptotic capacities for low signal‐to‐noise ratio (SNR) are compared and it is shown that the Rayleigh fading channel loses about 1 dB.
Feasability of AM‐VSB CATV optical networks using semiconductor laser diodes
Authors: Froidure Jean‐Christophe , Jaunart Emmanuel , Mégret Patrice , Lamquin Michel , Blondel Michel 
Published: September 2008

AbstractIn the past five years practical multi‐channel AM‐VSB optical fibre links have moved from the R&D labs into real world applications. In this paper, we focus on the design and performance capabilities of current commercialized systems using distributed feedback lasers (DFB), single mode optical fibres and PIN optical receivers. We first discuss fundamental concepts used in IM‐DD communication links. The noise and distortions sources are identified and their influence on the systems performances are presented. The use of Erbium Doped Fibre Amplifiers (EDFA) at 1550 nm is envisaged and their influence on the power budget of the CATV network is analyzed.
Letter: New statistical model for burst error distribution
Authors: Cornaglia Bruno , Spini Marco 
Published: September 2008

AbstractDue to the adoption in high capacity Digital Radio Relay Systems of transmission techniques such as low redundancy error‐correcting codes, trellis coded modulations, Viterbi receivers, etc., the errors tend to be clustered in bursts. Up to now, a model used to describe the burst error distribution was the Neyman‐A contagious model. This model was conceived to be applied in entomology and bacteriology, but it is also used in telecommunications. So, according to this model, the bursts and the number of errors in bursts are both supposed to be Poisson distributed. However, this distribution does not represent accurately the real situation, so, in order to derive a new probability distribution function, that improves the accuracy of the description of a burst error distribution a new model is required. In this paper a new model based on Erlang distribution for the number of errors in bursts, is described by using the Neyman approach.
Orthogonal short codes for code division multiple access networks
Authors: Kanj Khalil , Elhakeem Ahmed K. , Le‐Ngoc Tho 
Published: September 2008

AbstractShort codes are known to have better balance and spectral characteristics than their long counterparts. In this work we show by simulations that for certain users loads their bit error performance are excellent. A CDMA network performance is investigated under different load and fading situations. We also investigate the effects of using orthogonal codewords in conjunction with concatenated short codes to further reduce the multi‐user interference in these networks.
Narrowband characterisation of the land mobile satellite channel: A comparison of empirical models
Authors: Kanatas Athanasios G. , Constantinou Philip 
Published: September 2008

AbstractLand Mobile Satellite Systems (LMSS) are subject to severe signal degradation due to. blockage of the line‐of‐sight (LOS) path as well as multipath propagation phenomena. A thorough understanding of the fading effects is of great importance to the design of such a system. This paper reviews and compares ‐ where appropriate ‐ the empirical narrowband models reported in literature. The observation and comparison of these models leads us to the conclusion that this type of channel is strongly dependent on the frequency used For the link, the elevation angle, and the characteristics of the environment in the vicinity of the mobile. The values included clearly indicate the behaviour of the original models and their modifications under different conditions. A table including expected values for the required link margin is presented for the system engineers.
The EXPLOIT testbed
Authors: Potts Martin 
Published: September 2008

AbstractSeveral articles in this special issue of the ETT journal, entitled “ATM Field Trials and Experiments”, refer to specific traffic experiments performed on the “EXPLOIT” ATM testbed in Basel, Switzerland. This paper is intended to give the reader a general introduction to this testbed, background information about the project in which it has been supported and extended, and an in; sight into the range of areas in which traffic experiments have been performed. The testbed currently comprises 6 ATM switches, interworking capabilities to N‐ISDN and Frame Relay, broadband signalling and traffic control features which, combined with access to the European ATM network, form a unique platform for the testing of new broadband terminals and applications. Sophisticated traffic generation and analysis equipment is also being used to undertake traffic experiments, mainly in the ATM‐sensitive areas of traffic control, resource management and network performance.
Experimental evaluation of CDV impact on ATM resource management
Authors: Jaussi Laurent , Barcelo Jose‐Maria , Louis Stephane , Casals Olga 
Published: September 2008

AbstractMeasurements of the CDV that a CBR connection accumulates through an ATM network that consists of several switches are presented in this paper. Combining network segments on the EXPLOIT testbed, the Swiss ATM pilot network and the ATM Local Area Network at the Swiss Federal Institute of Technology, an extended test platform could be constructed to evaluate the magnitude of CDV accumulated in a real network. The measurement results are compared to simple tractable models that can be used to dimension the CDV tolerance for UPC/NPC functions along the network. Finally, an estimation of the impact of CDV on resource allocation is carried out using so‐called Worst Case Traffic models to estimate the maximum amount of CDV tolerated to guarantee the proper operation of multiplexing functions.
The validation and integration of the TRIBUNE test‐bed
Authors: Doelman Arie 
Published: September 2008

AbstractThe RACE project TRIBUNE is focused on a number of issues pertaining to the introduction of the Integrated Broadband Communication. The project has implemented a broadband test‐bed with a fully standardized Broadband User Network Interface (B‐UNI) according to the latest ITU‐T recommendations. A lot of effort was therefore spent on the specification, implementation and verification of the B‐UNI and the integration of the test‐bed. This paper is intended to focus on the evaluation of the innovative methods used and experience gained during the three year period of specification, implementation and verification. In this paper we will start with focusing on the specification of the B‐UNI. Particularly the decision to use formal specification languages (‐SDL 88) will be evaluated. The actual implementation of the B‐UNI is discussed in the second part, specially the experience and result of the use of automatic code generation modules. We will elaborate on how the verification of the implementation of the B‐UNI was managed in the third part of this document. Specially the use of the Ferry Clip method and the automatic generation of test suites will be focused upon. Finally, we will show that the taken steps in the previous phases have led to relatively short and easy integration phase of a complex test‐bed around a B‐UNI.
Behaviour of XTPX in the European ATM pilot
Authors: Klovning Espen , Bonaventure Olivier 
Published: September 2008

AbstractWe present and discuss measurements performed with XTPX over the European ATM Pilot. The main characteristic of this wide area ATM network is that the traffic contract is enforced by a Usage Parameter Control (UPC) mechanism. When the ATM traffic is compliant with the traffic contract, XTPX achieves a good utilisation of the link. However, when the ATM traffic is not entirely compliant, the UPC discards cells and the link utilisation becomes very low.
On the effects of workstation scheduling on ATM cell output
Authors: Lin Eric C. , Karlsson Gunnar 
Published: September 2008

AbstractIn this paper, we report on how System V UNIX scheduling can affect the way a workstation outputs ATM cell traffic under various process loads. Whenever multiple processes run concurrently, process contention occurs that creates burstiness and affects a workstation's traffic output. Experiments using a generic sending process and an FTP file transfer were performed that reveal the scheduling contention effects on traffic flow. Our results show that contention can introduce significant cell delay which can be on the order of hundreds of milliseconds. In addition, burstiness occurs where cells are “clumped” together in a variable manner. The average cell output rate decreases with increasing process load, but there is a preference given to a process that transmits cells as opposed to CPU‐intensive programs. The impact of scheduling on traffic shaping based on a leaky bucket is also examined. We show that improper selection of the shaping parameters can occur if change in the process load is ignored and if the initial transient associated with process start‐up is not accounted for. Lastly, we make some comparisons between the scheduling algorithms of System V and 4.3 BSD UNIX.