bluuebunny/crossref_metadata_2025 huggingface dataset:
Discrete‐Ordinates 1‐D Time‐Dependent Kinetic Model for Neutral Particles in the Scrape‐Off Layer
Authors: Sabbadin E. , Zanino R.
Published: July 2007

A 1‐D kinetic code has been developed for simulating the transport of neutral particles in the Scrape‐Off Layer using the multi‐energy‐group discrete‐ordinates (SN) solution method. The SN algorithm, usually applied to time‐independent calculations, has been here extended to the time‐dependent case. The code has been coupled with a 1‐D, 1‐fluid, time‐dependent plasma code, and results comparing the diffusion (S2) approximation with the fully kinetic case are presented.
S2: A Finite Element Code for Modelling Transport in Tokamak Divertor and SOL
Authors: Simard M. , Marchand R.
Published: July 2007

A symbolic finite element code is used to simulate transport of a single‐species plasma in the edge and divertor of a tokamak. The physical model is based on a fluid description of the ion density, ion parallel momentum, ion and electron pressure. In modelling recycling, transport of neutral density and energy is treated in the diffusion approximation. The system of equations is discretised on an unstructured triangular mesh, thus permitting good spatial resolution near the X‐point and an accurate description of divertor plates of arbitrary shapes. S2′s symbolic interface allows the physical model to be conveniently defined using standard mathematical notation. Comparisons with B2.5 simulation results are presented.
The Effect of Heat Flux Limiting on Divertor Fluid Models
Authors: Day M. , Merriman B. , Najmabadi F. , Conn R. W.
Published: July 2007

The classical plasma electron heat flux can greatly overestimate the physical heat flux when the electron mean‐free‐path becomes long compared to the electron temperature gradient scale length. For fluid modelling of plasmas, a common remedy is to apply an artificial „flux limiter”︁ that keeps the heat flux at a physically reasonable value in this long mean‐free‐path regime. The ad‐hoc limiter is not derived from first principles and it introduces a poorly understood free parameter into the model. We study the effect of this parameter in our divertor plasma models to understand how it influences the computed solution. We investigate regimes of both short and long mean‐free‐path and consistently find large parameter sensitivity. Thus, without additional experimental or theoretical guidance in the choice of flux‐limit parameter, flux limiting does not appear to provide an acceptable basis for predictive plasma fluid modelling.
Parallelization of and Results from Kinetic Edge Plasma Code W1
Authors: Xu X. Q. , Batishchev O. V. , Byers J. A. , Cohen R. H. , Krasheninnikov S. I. , Rognlien T. D. , Sigmar D. J.
Published: July 2007

In this paper, we describe a highly parallelized implementation of the 1D2V collisional PIC‐MCC code (W1 by Batishchev[1]) for Scrape‐Off‐Layer (SOL) plasmas on the Cray T3D using the PVM message‐passing library. The particles are divided equally among the processors, and grid quantities (temperatures, etc) are averaged from all processors. The electric field is solved using the electron momentum equation. The logical sheath potential is calculated in a serial fashion. For a fixed number of particles in the simulations (1 million particles), we have obtained a factor of 31 speed‐up by using 32 processors compared to 1, and a factor of 90 speed‐up by using 128 processors. Through our efforts on Cray T3D with 256 processors we have learned that massively parallel MIMD systems offers a new supercomputing capability for kinetic SOL physics modelling.
Axial Structure of the Field Intensity in Diffusion‐Controlled Surface‐Wave Produced Plasmas
Authors: Aliev Yu. M. , Georgieva M. , Grosse S. , Schlüter H. , Shivarova A.
Published: July 2007

Surface‐wave gas discharges sustained under the conditions of a diffusion controlled regime are studied on the basis of the fluid plasma model. The self‐consistent behaviour of the plasma density and of the field intensity along the discharge length is obtained. It is shown that the nonlinearity in the particle balance equation due to stepwise ionisation determines the plasma density in terms of the field intensity and ensures self‐consistent behaviour of the wave ⟺ discharge characteristics in a diffusion controlled regime.
Doppler Broadening and Magnetic Field Effects on the Balmer Lines Emitted at the Edge of a Tokamak Plasma
Authors: Hey J. D. , Korten M. , Lie Y. T. , Pospieszczyk A. , Rusbüldt D. , Schweer B. , Unterberg B. , Wienbeck J. , Hintz E.
Published: July 2007

Profiles of the Balmer lines Da(Ha), Dβ(Hβ) and Dγ(Hγ) have been measured in the scrape‐off layer and within the edge of the TEXTOR (upgrade) plasma, under Ohmic conditions and with neutral‐beam injection. Each line profile shows a strong Zeeman effect in the vicinity of line centre, and a marked central dip when mainly the σ components are observed. The line core evidently originates from cold atoms in the edge plasma, excited in the course of molecular dissociation, while the broad pedestal on which the core rests is radiated by excited atoms produced through charge‐exchange recombination of deuterons (protons), transported outwards from the much hotter plasma interior, and by atoms heated directly by collisions with the deuterons (protons). Core temperatures of about 0.5 eV and less are obtained from line profile analysis.
The Interaction of the Supersonic Plasma‐Jet with the Substrate in the RF Plasma‐Chemical Reactor
Authors: Šícha M. , Hubička Z. , Tichý M. , Novák M. , Soukup L. , Jastrabík L. , Behnke J. F. , Kapička V. , Kapoun K. , Šerý M.
Published: July 2007

Although the plasma‐chemical processes and properties of the deposited thin film can strongly depend on the interaction of the supersonic plasma jet channel with the substrate, up to now the study of this phenomenon has not yet been done. We decided to study this interaction by means of CCD camera. The presented results indicate that the light intensity recorded close to the substrate can be used as a measure of the intensity of plasma‐chemical deposition processes on the substrate surface.
Anomalous Electric Fields Inside a Dense Plasma of a Current Sheet
Authors: Frank A. G. , Gavrilenko V. P. , Ispolatov Y. A. O. , Kyrie N. P. , Oks E.
Published: July 2007

For the first time there have been analyzed profiles of electric‐field‐sensitive na spectral lines of the Li‐like impurity ions CIV, NV, OVI emitted by a hot dense plasma of a plane current sheet. Theoretical profiles of these lines have been calculated with an allowance for Anomalous Electric Fields (AEF). By comparing the experimental and theoretical profiles of the lines it has been established for the first time that in the plane current sheet there were developed AEF of rms strengths F0 ≈ (100–120) kV/cm in the time interval from τ = −0.2 μs to τ = 0 (the time τ was counted from the instant of the maximum intensity of the spectral line OVI 5291 Å). These results have been backed up by a similar analysis of the experimental profiles of the spectral line HeII 4686 Å of the primary gas of the discharge. The AEF reached these strengths at the same instant of time, τ = −0.2 μs, when electron and ion temperatures reached their maxima: Te ≫ 100 eV, Ti ≈ 300 eV. The instant τ = −0.2 μs corresponds to a transition from the metastable stage to the explosive phase of the current sheet evolution. At this time the ratio of the AEF energy density to the thermal energy density of the plasma was § ≡ F20/[8π/NeTe + NiTi)] ≈ 10−3, which exceeded a similar ratio for the thermal wave field by three orders of magnitude.
Measurement of Excited States Density and the VUV‐Radiation in the Pulsed Xenon Medium Pressure Discharge
Authors: Kindel E. , Schimke C.
Published: July 2007

Time resolved absolute density measurements of the 1s5 (metastable) and 1s4 (resonance) level in the positive column of a pulsed xenon gas discharge for gas pressures between 1 and 40 Torr and currents between 100 and 300 mA are presented. The densities ranged from 1 × 1011 to 5 × 1012 cm−3 and were found to be ten times larger in the afterglow than in the active part of the discharge. The enhanced radiation obtained in the afterglow in the near infrared regions as well as in the VUV region is caused by a dissociative recombination and formation of excimer states.
Dissociative Excitation of Tetramethylsilane (TMS) and Hexamethyldisiloxane (HMDSO) by Controlled Electron Impact
Authors: Kurunczi P. , Koharian A. , Becker K. , Martus K.
Published: July 2007

The optical emission spectra in the wavelength region 200–800 nm produced by electron impact on the silicon‐organic molecules TMS (tetramethylsilane) and HMDSO (hexamethyldisiloxane) under controlled single‐collision conditions have been analyzed. Absolute emission cross sections from threshold to 200 eV impact energy were determined for a variety of emission features. For both targets, the CH(A2Δ → X2Π) emission, the so‐called CH „4300 Å”︁ band, was found to have the largest emission cross section with values (at 100 eV) of 5.5 × 10−19 cm2 and 6.1 × 10−19 cm2 for TMS and HMDSO, respectively. Relatively high onset energies of 28.0 ± 1.5 eV (TMS) and 33.1 ± 1.5 eV (HMDSO) were measured for these emissions. Weaker emission features in both spectra were identified as CH bands corresponding to the B2∑− → X2Π transition (the CH „3900 Å”︁ system) and the C2∑ → X2Π transition, and as the atomic Si line emissions at 253 nm and 288 nm. Near‐threshold studies indicate an onset for the Si emissions of 29.0 ± 2.0 eV (TMS) and 44.6 ± 2.0 eV (HMDSO). Absolute cross sections and appearance energies were also determined for the strongest lines of the hydrogen Balmer series for both targets. The comparatively high onset energies and small emission cross sections for all observed emissions indicate that single‐step dissociative excitation processes are unlikely to play a dominant role in low‐temperature processing plasmas containing TMS and HMDSO.
Kinetic Theory of Sound Propagation in a Dissociating Gas
Authors: McLennan J. A.
Published: July 2007

The effects on the propagation of sound of dissociation and recombination in a diatomic gas are discussed on the basis of kinetic theory for such a gas. A perturbation theory is used in which the perturbation incorporates the collision operator for reactions and the convective term in the Boltzmann equation. Consequently the sound frequency need not be small relative to the reaction rate, so the results describe the transition between slow and fast reaction regimes.
Dielectric Theory of Collisional Absorption in Intense Laser Fields
Authors: Mulser P. , Saemann A.
Published: July 2007

Collisional absorption of superintense laser pulses in dense plasmas can be described by the classical linear dielectric theory in a wide range of parameters. For electron oscillation velocities largely exceeding their thermal motion a linear oscillator model is presented and nearly exact solutions in terms of Anger functions are given for the time‐averaged electron‐ion collision frequency. A possible extension of the dielectric theory into higher density and/or lower temperature regions is indicated and the need for time‐dependent collision frequencies is stressed.
Wall Recombination in Glow Discharges
Authors: Behnke J. F. , Bindemann T. , Deutsch H. , Becker K.
Published: July 2007

We derived a model describing the radial distribution of the ion and electron densities and the radial electric field strength in the positive column of a glow discharge. The set of equations related to the plasma consists of the equations for particle and momentum conservation for the ions and electrons and the Poisson‐equation. In a novel approach, the necessary boundary conditions in our model result from a system of balance equations for the charge carriers on the insulated wall surrounding the positive column.
Analysis of Three‐Dimensional Motion of Relativistic Electrons in Ion‐Focused Electrostatic System
Authors: Liu P.‐K.
Published: July 2007

Three‐dimensional motion of relativistic electrons in ion‐focused electrostatic system, which is the basis of investigating the ion‐channel electron cyclotron maser (ICECM) or circular polarized ion‐channel laser (CPICL), is analyzed through nonlinear numerical simulation. The results show that the projection of electron orbit in cross‐section is, in general, a precessing ellipse with a center on the axis of the ion‐channel in a cylindrical ion‐focuse electrostatic system. When injection electrons satisfy a specific condition, the electrons can have a steady circular orbit. The effect of relativistic factor on electrons' motion is discussed. Using the perturbation method, the eigenfrequency of this system is derived as Equation \documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt {4 - \beta _ \bot ^2 } \omega _0 $\end{document} where wo is the cyclotron frequency of the electrons. This implies that there may exist a new kind of instability in ICECM or CPICL.
Spectral and Electrical Characteristics of a Stabilized DC Arc Seeded With Potassium
Authors: Stoiljković M. M. , Holclajtner‐Antunović I.
Published: July 2007

A systematic investigation of spectral and voltage‐current (U‐I) characteristics of a DC arc plasma was performed. The vertical, argon and wall stabilized DC arc plasma was seeded by an easily ionizable element (EIE), potassium, in a wide range of concentrations. It was found that different arc currents and potassium contents in the plasma have considerable influence on the plasma properties. A lower potassium content (< 10 g/l of KCl in solution) introduced into the arc at lower currents (<6A) causes an increase in arc voltage and a change in the arc spectrum (intensity of lines), while at higher arc currents (>6A) it causes no change in the electrical characteristics, but a further change in the intensity of the arc spectrum. Higher potassium concentrations, >20 g/l of KCl, increase the arc voltage at higher currents (>6A). There is a critical quantity of potassium in the plasma which suppresses high energy processes (ionization, excitation…) for a fixed arc current, while spectral composition and lateral distribution of the residual emitted spectra become essentially changed. Amounts of potassium above critical do not cause further changes in the plasma spectral composition nor in the I‐U characteristic, except in the spectral line intensities.
Spatially Homogeneous Modelling of a Stabilized XeCl* Laser Discharge
Authors: Gortchakov S. , Loffhagen D. , Winkler R.
Published: July 2007

Recently an improved technique to create a stable and homogeneous discharge for pumping excimer laser plasmas has been proposed in [1]. This technique is based on the additional use of a stabilizing low‐current preliminary discharge.

For the study of such laser discharges a self‐consistent spatially homogeneous model with the inclusion of the time‐dependent Boltzmann equation for the electrons, of the rate equation system arising from the heavy particle and photon kinetics and of the electrical circuit equations has been employed. A brief presentation of important features of the comprehensive model is given. An iterative procedure to solve self‐consistently the system of kinetic, rate and circuit equations has been generalized and applied to discharge conditions where a dominant electron‐electron interaction occurs.

Model calculations have been performed for typical XeCl* laser plasmas which operate according to the improved discharge technique. On this basis a detailed analysis of main features of this laser discharge is given and the impact of various parameters on significant characteristics of the discharge is calculated and discussed.
Ergodic Divertor : Present Status of Understanding
Authors: Grosman A. , Ghendrih Ph. , Capes H. , Féron S.
Published: July 2007

The ergodic divertor (ED) experiments on Tore Supra have demonstrated the capability of open divertors to reach significant results in terms of plasma‐wall interaction control. Standard statistical analysis of stochastic systems allows one to derive the diffusion of free particles when the threshold to stochasticity is reached. However, transport analysis modifies this picture owing to boundary effects due to sources and sinks. The energy deposition onto the target plate is shown to be governed by parallel transport over the parallel coherence scale of the temperature field. This transport referred to as laminar transport is very similar to that found in axisymmetric divertors. Using field line tracing (MASTOC code), one can locate precisely the location of the peak in energy deposition. Qualitative agreement with experimental evaluation of the peaking factor is obtained using the radial penetration of field lines given by Mastoc and a WKB approximation.
Multi‐Species Developments in the EDGE2D Code
Authors: Fichtmüller M. , Corrigan G , Radford G , Simonini R , Spence J , Taroni A
Published: July 2007

The scrape‐off layer code EDGE2D has been extended to accommodate more than one impurity species [1]. The parallel transport coefficients are calculated from a 21 moment description using the method of reduced charge states (RCS). Simulations with carbon and helium as impurities have been carried out to validate the multi‐species version of EDGE2D. It is shown that further use of RCS allows the reduction of the number of momentum equations. The computing time is thereby substantially reduced. At the same time the code results show little difference between using the reduced set of momentum equations and using the full set.
Modelling of Impurity Generation and Transport with a Monte Carlo Method based on Single Particle Motions
Authors: Kawamura T. , Ono T. , Kenmotsu T. , Ohyabu N.
Published: July 2007

The generation and transport of impurity particles in a boundary plasma are analysed on the basis of a single particle motion together with a Monte Carlo method, where the Langevin‐type equation of an impurity particle is used. The impurity generation and transport in a scrape‐off layer are modelled after the Large Helical Device (LHD). The screening efficiency of the SOL for the impurity penetration into a core plasma, impurity redeposition on the first wall and the other effects are analysed from the statistics of traces of many impurites.
Active Plasma Boundary Sheath with Electron Emission
Authors: Hantzsche E.
Published: July 2007

The influence of electron emission on the properties of the space charge sheath between plasma and wall is investigated theoretically using models of the stationary sheath. Especially, the following effects have been considered:

Essential parameters of the sheath (e.g. potential drop, power flux density), of the wall surface (temperature, field strength, emission yield, Joule heat generation) and of the adjacent plasma layer (emission‐caused change of the electron temperature) have been calculated under self‐consistent conditions.

From the obtained results several ways are discusséd indicating the development towards sheath instability and ending in the generation of plasma‐induced arc spots.
Polarizations of Magnetohydrodynamic Waves in a Cold Multi‐Species Plasma
Authors: Suchy K.
Published: July 2007

Starting with the expression for the permittivity tensor for a loss‐free magnetoplasma the low‐frequency limits of its eigenvalues are calculated. They are used for the dispersion relations and polarization ratios of the shear Alfvén mode and the fast magnetosonic mode.
Intense Heavy Ion Beams as a Tool to Produce and Analyze Dense Plasmas
Authors: Neuner U. , Bock R. , Funk U. N. , Hoffmann D. H. H. , Stetter M. , Stöwe S. , Tauschwitz A. , Udrea S.
Published: July 2007

The synchrotron SIS at GSI presently offers the possibility to heat samples of matter at solid state density to temperatures between 0.2 and 1 eV within times shorter than the desintegration time of these samples. Hot matter below solid state density can be investigated using the expanding sample, whereas densities above solid state density are produced by shock wave compression in compound targets.

Measurements of sample expansion and pressure as well as corresponding simulations are presented. Future experimental schemes are discussed including the use of the ion beam as a diagnostic tool for dense plasma, relating its energy loss to the sample density.
Time‐Resolved Optical Monitoring of Laser‐Produced Plasma Derived from Germanium
Authors: Német B. , Musiol K.
Published: July 2007

Optical emission studies of neutral and first ionization atomic forms of germanium in a plasma obtained by Nd:YAG laser ablation of germanium sample in atmospheric air have been presented.
Non‐Markovian Kinetics for Nonuniform Plasmas
Authors: Wallenborn J.
Published: July 2007

The nonlinear Balescu‐Lenard kinetic equation has been generalised to weakly nonideal spatially nonuniform polarisable plasmas. This is done by including nonlocality in space and time in the collision term. The local laws of conservation for particle, momentum and total energy densities follow. Some outstanding problems are discussed.
Quantum Molecular Dynamics Simulations of Dense Matter
Authors: Bickham S. R. , Collins L. A. , Kress J. D.
Published: July 2007

We have developed a quantum molecular dynamics simulation method for treating dense plasmas and a variety of other systems. The approach treats the electrons fully quantum mechanically and the nuclei classically. Applications include H plasmas, alkali metal fluids, rare gas compression, mixtures, impurities in plasmas, and shock‐compressed hydrocarbons.
Calculation of the Radiative Opacity of a Hot Dense Plasma
Authors: Orlov N.
Published: July 2007

Results are presented for a theoretical model, known as the ion model (IM), recently elaborated to calculate the radiative opacity of a hot dense plasma. The model is based on the self‐consistent field method for subsystems obeying Gibbs statistics. The model is applied to compound chemical compositions. The problem of optimal selection of compound compositions is discussed both for laser and heavy ions targets designs.
Density Expansions of the Reduced Distribution Functions and the Excess Free Energy for Plasma with Coulomb and Short‐Range Interactions
Authors: Kahlbaum T.
Published: July 2007

The equilibrium properties of a multi‐component plasma of charged particles that interact through the Coulomb potential and general short‐range potentials are investigated at low density within the framework of classical statistics. In particular, this article presents density expansions of (1) the reduced distribution functions for two and more particles up to second order as obtained from the screened Bogoliubov‐Born‐Green‐Kirkwood‐Yvon hierarchy and (2) the interaction contribution to the Helmholtz free energy including a new closed representation of the fourth cluster integral derived with the help of a usual charging procedure.
K‐Entropies of Electrons and Ions in Nonideal Plasmas
Authors: Morozov I. V. , Norman G. E. , Valuev A. A.
Published: July 2007

The Krylov‐Kolmogorov entropy (K‐entropy) is calculated for electrons and ions in nonideal plasmas by the method of molecular dynamics. Two different time scales are established corresponding to the electron and ion K‐entropies.
On Island Formation in a Locally Perturbed Tokamak Equilibrium
Authors: Kaleck A.
Published: July 2007

To control the plasma transport at the edge of a tokamak the outer flux surfaces can be artificially destroyed by applying a resonant helical magnetic field, as it is demonstrated at Pulsator [1],[2], [3], Tore Supra [4],[5] and proposed for TEXTOR‐94 [6] in the concept of “ergodic divertors”.

As a measure of the efficiency of the perturbation field e.g. the level of the field line diffusion coefficient DFL the width Δi of the magnetic islands and the related Chirikov parameter are of importance [7],[8],[9],[10].

For the planned Dynamic Ergodic Divertor (DED) at TEXTOR‐94 where the perturbation coils are located at the high field side the standard expression for Δi using the Fourier components of the magnetic field perturbation [7] leads to results significantly different from field line tracing calculations [11].

The standard expression is commonly used in terms of the perturbation magnetic field δB [5],[7],[8],[9],[12],[13]. But when replacing the Fourier components of the perturbation vector potential by those of the magnetic field finite aspect ratio effects have been neglected so far. For present tokamaks with ϵ = r/R ≃ 0.3 this can lead to an error in the field line diffusion of one to two orders of magnitude.

In this paper it is shown that taking into account the finite aspect ratio at this point leads to correct results compared to the highly precise field line tracing calculations by the Gourdon code. The island width then is recognized to depend significantly on the poloidal position of the perturbation field. This is in contrast to the standard expression. Also the role of the choice of the magnetic coordinate system is considered.
Probe Method for Measuring the Mach Number and the Flow Vector in Edge Plasma
Authors: Amemiya H. , Tsushima A. , Fuchs G.
Published: July 2007

A planar Mach probe to measure the Mach number and the flow vector with respect to the magnetic field in the edge plasma of e.g. a tokamak is being proposed. The probe is constructed as a double probe and the saturation ion current is measured as function of the angle of rotation of the probe surface normal with respect to the magnetic field. The saturation current as function of the angle is calculated by taking a drifted Maxwellian distribution for ions and an effective size of the probe depending on the angle. From the ratio of the saturation currents for plus and minus biases respectively and from the envelope of the saturation current with respect to the rotation angle, the Mach number and the flow vector can be determined.
Economic comparisons of alternative fiber‐based local access architectures using ATM components
Authors: Reed David P.
Published: July 2007

This paper presents some engineering and economic comparisons of several fiber‐based network architectures providing narrowband, and in some cases broadband, services in the subscriber loop. Specifically, comparisons are made between different bus and star configurations in the sub‐feeder plant using asynchronous transfer mode (ATM) network components. The study reports in detail an engineering cost model used to determine the installed first cost of several access architectures, including severalfiber‐to‐the‐curbapproaches which interface to the existing copper drop. The results show that these approaches can reduce the initial first cost of fiber installation, although other issues regarding network operations, maintenance, and evolution still need to be addressed.
Loop‐network configuration and single‐mode optical fiber cable technologies for subscriber network
Authors: Ashiya Fumihiro , Matsumoto Michito , Nagasawa Shinji , Tomita Shigeru , Uenoya Takuya
Published: July 2007

This paper will discuss optical fiber cable distribution networks for accomodating the immediate introduction of optical subscriber networks. The concepts of cable distribution system design, the maintenance systems and the cables and jointing technology for supporting these systems will be discussed. The results of experiments using related technology will also be discussed.
Fibre to the home—The passive way
Authors: Oakley Keith
Published: July 2007

Passive optical networks are an attractive alternative to copper for basic POTS delivery in the near term. Since PONs provide a direct photonic path between the exchange and the customer they offer the maximum opportunities for network evolution by allowing services to evolve naturally and independently in the market place.
A reasonable solution to the broadband congestion control problem
Authors: Cooper C. Anthony , Park Kun I.
Published: July 2007

The control of congestion in asynchronous transfer mode (ATM)‐based networks is an important and complex subject that must be properly addressed in order to permit efficient use of network capacity while providing good quality of service to all network users. This congestion control problem is characterized here, and the performance‐related aspects of some key congestion control features are modelled. Congestion controls for a broadband network will include features for admission control, buffer and queue management, traffic enforcement and reactive control. This paper identifies the leading alternatives for each of these congestion control features, presents an approach for comparing these alternatives based on the relative efficiencies achievable with each, and suggests one reasonable set of congestion control features. Our approch for comparing congestion control alternatives is based on a suitable model for the congestion‐related functions of an ATM‐based network, togther with a characterization of the traffic loads imposed by various broadband services.
ATM traffic control for guaranteed performance
Authors: Kositpaiboon Rungroj , Woodruff Gillian , Richards Philip
Published: July 2007

Traffic controls in an ATM network must be designed to satisfy the bandwidth and performance requirements of a wide range of services. The challenge is to design simple and effective controls while allowing a reasonable utilization of bandwidth which can be achieved with statistical multiplexing. Several high‐level design principles for these controls are emphasized, and their implications on traffic types suitable for statistical multiplexing are illustrated with analytical and simulation performance results. A simple and effective control scheme is proposed to handle multiple traffic classes.
A congestion measure for call admission and traffic engineering for multi‐layer multi‐rate traffic
Authors: Hui Joseph Y.
Published: July 2007

We consider traffic control for services with constant bit rate (CBR) or multi‐layer Poisson statistics. Through the use of the Chernoff bound for the probability of traffic overflow, a congestion measure s* can be conveniently used for traffic control methodologies such as call admission and traffic engineering. We investigate extensively the mathematical properties of this congestion measure, and provide intuitive economical interpretations for the purpose of traffic integration. Applied to dynamic non‐hierarchical routing (DNHR), we show why the marginal bandwidth cost is a good criterion for choosing least cost paths.
Considerations in ATM switching system traffic control
Authors: Murakami Koso , Takase Tadahiro , Hajikano Kazuo , Hattori Shimmi
Published: July 2007

We propose a traffic control scheme for asynchronous transfer mode (ATM) switching systems, clarifying requirements for traffic control derived from the ATM network characteristics and demonstrating basic control concepts. The proposed scheme accepts calls based on the available bandwidth and buffer use rate, making it possible to integrate the network without classification by service type.
ND:YAG light source and external modulator for a VSB‐AM video transmitter: A performance evaluation
Authors: Trisno Y. , Grubb D.
Published: July 2007

A miniature Nd:YAG laser and an intensity modulator based VSB‐AM video signal transmitter are described. With a light source having RIN level below ‐170 dB/Hz, the system allows a relatively low modulation index to be used. For a 40 channel system using a standard MZ, a CTB = 60 dB corresponds to mi = 1 per cent. With a 75 mW Nd:YAG laser source, a system with a power budget of 5.5 dB and 50 dB CNR is realizable. Several promising techniques of modulator linearization are also given.
Optical amplifiers for video distribution
Authors: Huber D. R. , Glaab J. B.
Published: July 2007

The promise of a broadband fibre communications network has attracted the interest of CATV and Telco concerns. Various networks and topologies have been discussed. Cost is a drawback in some of the proposed networks, particularly those networks which require switching. This paper discusses a low cost broadcast tree and branch network which uses optical amplifiers to extend the network penetration. Recent work in the development of optical amplifiers suggests that the Erbium fibre amplifier may be compatible with VSB‐AM. The characteristics of such an amplifier will be discussed. This scenario allows an orderly transition from the present‐day AM backbone system to the tree and branch fibre architecture. Once the broadband fibre plant is in place new services can be implemented that exploit the broadband nature of fibre.
An experimental ATM switch for BISDN studies
Authors: Palmer Rob
Published: July 2007

This paper describes the architecture, functionality and performance of an experimental ATM switch being developed at the Telecom Australia Research Laboratories as part of its investigations into the broadband ISDN. The proposed switch architecture consists of parallel omega networks preceded by a Batcher bitonic sorting network. The switching fabric has no internal cell buffering. Cell buffering is provided only on the switch outputs for cells simultaneously contending for the same output port. The switch fabric and cell buffers include mechanisms for providing prioritized servicing of queued cells and prioritized discarding of cells based on priority fields contained within the cell header. Components of the switch are currently being implemented in 2 μm CMOS VLSI.
A connection control strategy for bursty sources in broadband packet networks
Authors: Jabbari Bijan
Published: July 2007

This paper proposes an admission strategy for connection‐oriented services at the access node of a broadband integrated packet network based on asynchronous transfer mode. Based on an estimate of the probability of cell loss and in the absence of buffering, we determine the number of sources from different classes of bursty traffic which can be accepted. The parameters which are used to describe the traffic sources are average bit rate and peak bit rate. We will evaluate the cell loss estimate for homogeneous and heterogeneous cases. Furthermore, we will examine the variation of this estimate as the average to peak ratio changes. The estimate is an upper bound for the probability of cell loss. Based on this upper bound simple and robust allocation of resources to bursty sources can be developed. The proposed strategy can be implemented using simple computations or via a look‐up table to determine admission or denial of an incoming call and therefore allocating the required capacity. The procedure results in efficient use of the bandwidth, ensuring the desired service quality for connection‐oriented services and results in proactive control of network congestion.
A method for congestion control in atm networks using peak rate throttling
Authors: O'Neill Chris
Published: July 2007

This paper presents a technique, called peak rate throttling, for congestion control of controllable, variable bit rate traffic in ATM (asynchronous transfer mode) networks. It is much less conservative than techniques that have already been proposed. This is because techniques already proposed take no account of the load that is actually being carried by the network. Techniques already proposed assign a predetermined share of network capacity to connections regardless of what is actually being used. The technique proposed here works by throttling the peak bit rate that a user is allowed to send on a connection when the network detects a rising network load that may increase the cell loss rate of connections to greater than an acceptable limit. Users are still permitted to send whatever average bit rate they require, however. The technique relies on the assumption that the load offered to network links is stationary for a long enough period so that controlling action does not need to be performed too often or too quickly.

It is feasible to achieve congestion control of a network using peak bit rate throttling alone and no other technique apart from connection control.
Performance trade‐offs in input/output buffer design for a non‐blocking space‐division packet switch
Authors: Lee Myung Jong , Li San‐Qi
Published: July 2007

Performance trade‐offs in buffer architecture design for a space‐division packet switching system is studied. As described in Figure 1, the system is constructed by a non‐blocking switch fabric and input/output buffers. The capacity of the non‐blocking switch fabric is defined by the maximum number of packets, denoted bym, which can be simultaneously routed from multiple inputs to each output. The buffer size at each input is considered to be finite, equal to K. The emphasis here is placed on the input packet loss probability for systems constructed by differentmsandKs. From the performance point of view, we conclude:

choosingm= 3 or 4 is sufficient to exploit the maximum utilization of a non‐blocking switch fabric

introducing input buffers of moderate sizeKsignificantly reduces the packet loss probability.
The consumer electronic bus: An integrated multimedia lan for the home
Authors: Hofmann J.
Published: July 2007

The consumer electronic bus, or CEBus is a multi‐media LAN standard for the home which is now being finalized in North America by the Electronics Industry Association's Consumer Electronic Bus Committee (CEBC). The CEBus consists of media with data channels, and a control channel. The control channel is used for allocating the use of the data channels and for carrying short messages, whereas the data channels are used to carry various signals which do not fit the control channel. The control channel is digital, whereas the data channels can carry signals of any type.

The physical layers for six media are at present defined in the standard: the power line, twisted pair, coaxial cable, infrared, low‐power RF, and a shielded cable bundle. An effort to define the physical layer for the seventh medium, optical fibre, was started at the end of 1989.

The data link and network layers are fully implemented, whereas the transport, session and presentation layers are null. The application layer is fully implemented, including a command language which is used to facilitate easy interaction between competitor's products from the same consumer product sector, and between those from different sectors.
Customer network configurations and generic flow control
Authors: Händel Rainer , Huber Manfred N.
Published: July 2007

This paper analyses the BISDN customer network configurations as specified in CCITT Recommendation I.413 (e.g. star, bus, ring, starred bus), assumed market needs and the impact on the ATM layer functionality at the broadband user‐network interface at the SBand TBreference points. Orderly and fair access of several terminals to a shared transmission medium requires a suitable access protocol (generic flow control). Its functionality and possible implementations are discussed.
A multiservice GFC protocol
Authors: Adams J. L.
Published: July 2007

Generic flow control (GFC) is used to provide controlled transmissions from terminals over the BISDN user‐network interface. The reason for requiring controlled transmission is to allow for the multiplexing of cells from a number of terminals connected in either a dual bus or star configuration.

GFC must provide fair access for each terminal, and the meaning of this is discussed for different services. It must provide a guaranteed minimum bandwidth, meeting the requirement of fair access for constant bit‐rate terminals. It must also provide fair access for variable bit‐rate (VBR) terminals. It is proposed that all terminals of a given class are given the same percentage reduction of their agreed peak bandwidths during overload conditions, leading to approximately similar delay distributions within the class. GFC can then be considered as providing a given quality of service per terminal (through guaranteed bandwidth) and an additional common quality of service for the unguaranteed cells.

Some simulation results are provided for the dual bus configuration.
Distributed resource management and connection control for a multi‐access interface to a broadband ISDN (BISDN)
Authors: Kramer M. , Shtirmer G.
Published: July 2007

A customer premises network (CPN) provides a common communications fabric to efficiently integrate the traffic of multiple terminals on a common access interface to a BISDN. An important consideration in choosing a CPN architecture is to facilitate terminal portability and applicationtransparency, so as to accommodate standard broadband terminals and applications, requiring only minor modification to adapt them from the standard BISDN interface to the multi‐terminal environment. This paper explores the multi‐faceted issues of CPN transparency with an emphasis on the evolving BISDN control and management architecture.

We introduce a control architecture that conforms to a rigorous separation between ‘call control’ and ‘connection management’. This allows the CPN to be transparent to the user to network signalling exchange, and to participate only in the connection management via a remote resource management protocol. More generally, this scheme allows a call control entity located in a local exchange node (LEN) to manage a distributed set of resources such as switches and multiplexors (and CPNs). This is achieved through the definition of a standard interoperable interface between the central call control entity and the connection control entities which may be remotely located in various network elements. The features and functionality for such an interface, which we term the bearer connection control interface, are described within the framework of the OSI remote management architecture.

A standard remote resource management protocol allows for the co‐operative sharing of resources across administrative domains. Although the importance of such a scheme is particularly visible as applied to remote CPN management, it is useful in other application domains where it is advantageous to distribute management processes.
A passive network termination for BISDN optical subscriber lines
Authors: Liberg Øyvind
Published: July 2007

Considerable cost saving and overall simplification can be achieved if the protocol for the access digital section is made identical to the one at the T interface. The network termination (NT1) may then be realized as a passive device, such as a simple connector. All active functions associated with the NT1 can then be performed on a time‐shared basis from the premises of the network provider. This scheme obviates the need for remote power feeding and activation mechanisms of the NT1. The time sharing of active functions, such as optical time domain reflectometry (OTDR) for supervision of the physical conditions of the lines, allows a substantial cost reduction of the subscriber access. It is shown that this technique yields a more efficient maintenance scheme than that afforded by an active NT1, resulting in a cost saving also in the long term. Ways of implementing the passive NT1 are discussed, and also its position in the evolution of passive optical networks (PON) towards BISDN.
OAM mechanisms for BISDN UNI and access networks
Authors: Uno Hiroshi , Maeda Youichi , Kanayama Yukiharu
Published: July 2007

This paper clarifies operation and maintenance (OAM) requirements for broadband integrated services digital network (BISDN) customer access systems including user‐network interface (UNI), and proposes basic OAM mechanisms. Access networks employ a logical networking architecture based on the asynchronous transfer mode (ATM) virtual path (VP) concept to provide all services efficiently, economically. Services are independent of the network's physical configuration. Thus, OAM functions for the access network are required to support physical and ATM layer capabilities. UNI physical performance and failure information flows to ensure user service quality are described. A fault localization mechanism is introduced that determines whether the failure lies on the network provider side or customer side. It uses failure information flows and loop back testing at the network terminator 1 (NT1). As connection‐related virtual path connection (VPC) availability indication is necessary for user‐to‐network applications and user‐to‐user applications, two alternative VPC‐related availability indication mechanisms are studied. Furthermore, basic performance monitoring mechanisms for ATM layer are described.
Intelligence in ATM terminals
Authors: Hellemans Patrick , Decuypere Hubert
Published: July 2007

In this paper we propose to migrate the intelligence for telecommunication services from the network into the terminals. In the first three sections we elaborate on the approach taken. The descending cost of processing equipment and the increased flexibility offered by ATM networks open new perspectives for the terminal business. In addition, only limited services will be offered by early ATM networks. Terminal‐based intelligence may overcome this initial gap. The physical configuration of such a terminal is presented in Section 4. In Section 5 the functional configuration of the terminal is proposed. The control module realizes a generic platform for the execution of telecommunication applications. This platform gives access both to local peripherals and to the telecommunication services offered by the network. The top layer consists of the telecommunication applications. In Section 6 a number of these applications are discussed. The remote execution application is of special interest since it gives remote access to telecommunication applications hosted on other IATs, so enlarging the capabilities of the local IAT.
A simple detector for trellis‐coded PSK mobile radio systems
Authors: Elnoubi Said , Youssef El‐Sayed , Helal Khaled
Published: July 2007

A simple detector for a trellis‐coded PSK mobile radio system is proposed. A precoder is added to the regular TC‐PSK modulator before convolution coding, and a simple one‐bit differential detector is used in the receiver. The decision is made symbol by symbol based on the output samples. The bit error rate of this system is evaluated in fast Rayleigh fading characterizing mobile radio channels by numerical integration.
An optimal policy for competitive processing of high‐ and low‐priority arrivals
Authors: Delic Hakan , Papantoni‐Kazakos P.
Published: July 2007

We consider two mutually independent traffic streams whose arrivals are stored in an infinite capacity buffer. The two arrival traffics are modelled by renewal processes and are competing for service by a single processor, where one of the processes requires a strict upper bound on the total delay per arrival. It is assumed that the processing per arrival, for both processes, is a constant; the value of this constant is different for each of the two traffic streams.

Given the above model, we consider policies that operate in a non‐interruptive mode. We first find the optimal scheduling policy, which attains throughput one and minimizes the expected delays of both traffic streams. The delays induced by the latter policy are analysed via a methodology based on the regenerative theorem. The theoretical results are supported by numerical examples.
Integration of interactive and distribution services: Impact on the network architecture and signalling
Authors: de Prycker M. , Verhoeyen M. , Decuypere H.
Published: July 2007

The integration of interactive and distribution services has an impact on both the architecture of the network and the signalling protocols. A configuration where both services are offered via ATM is discussed here. For multimedia services a layered service model is described. The impact of this layered model on the signalling is explained.