Analysis of Open Discrete Time Queueing Networks: A Refined Decomposition Approach

This paper deals with approximate analysis methods for open queueing networks. External and internal flows from and to the nodes are characterized by renewal processes with discrete time distributions of their interarrival times. Stationary distributions of the waiting time, the queue size and the interdeparture times are obtained using efficient discrete time algorithms for single server (GI/G/1) and multi-server (GI/D/c) nodes with deterministic service. The network analysis is extended to semi-Markovian representations of each flow among the nodes, which include parameters of the autocorrelation function.     

Potentials and challenges of peer-to-peer based content distribution

Multimedia content currently accounts for over three quarters of all Internet traffic. This increase in traffic volume and content availability derives from a paradigm shift from the traditional text and picture based Web, to more resource demanding audio and video content. A controversial driver for this development is content distribution systems based on peer-to-peer overlay networks. Flooding the Internet with often illegal content, these networks now pose challenges to all actors in the value chain. However, if viewed as surmountable challenges in an evolutionary path, peer-to-peer technology has the potential of increasing efficiency in content distribution and unleashing resources to form scalable and resilient overlay networks of unprecedented dimensions.

In this paper we examine the potentials and challenges of peer-to-peer technology in content distribution, and analyse how, and under which circumstances, peer-to-peer technology can be used to increase the efficiency of multimedia services. The paper provides an up-to-date overview of the development of peer-to-peer networks as well as describing the economics laws governing their use. To conclude the study, the paper analyses Skype, a well known telecommunications service utilising the peer-to-peer technology, as well as demonstrating the benefits of peer-to-peer based content distribution using empirical data from the Danish Broadcasting Corporation.     

Über eine neue Form von Zinnpest

Ohne Zusammenfassung     

Parameter estimation and optimization techniques for discrete-time semi-Markov models of H.264/AVC video traffic

We investigate a variety of known and new approaches for the estimation of the parameters of discrete-time semi-Markovian traffic models. We focus on modeling video traffic, since the accurate representation of its long-term autocorrelation is a challenge to the parameter estimation methods. The modeling techniques are applied to sample H.264/AVC-encoded video traces. We study their ability to reflect the autocorrelation and variability of the original traffic and also the delay probabilities of a resulting SMP/GI/1 queueing system. The delay probabilities are determined both by simulation and verified analysis of the queue.     

Über das Vorkommen von Eisen im Schwefel

Ohne Zusammenfassung     

Über das Wesen metallischer und elektrolytischer Leitung

Ohne Zusammenfassung     

Quality-of-Service Analysis for Statistical Multiplexing with Gaussian Distributed and Autoregressive Input

We investigate multiplexers in telecommunication systems with a workload process developing equivalent to that of a service system with semi-Markovian input, which includes fluid flow and time slotted systems. Discrete time methods are used to analyze their waiting time and loss rate.Our focus is on the performance evaluation of statistical multiplexing. Traffic flows are modeled by autoregressive processes producing autocorrelated and Gaussian distributed workload increases. The superposition of on-off voice sources approaches autoregressive processes and they also serve as a basic model for video traffic in an appropriate time scale, although video reveals a more complex autocorrelation structure. Performance results are obtained depending on only two parameters, which allow for clear conclusions about the statistical multiplexing gain with regard to bounds on loss rates as demanded in quality-of-service guarantees.     

Über die Herstellung kÜnstlicher Diamanten aus Silicatschmelzen

Ohne Zusammenfassung     

Über Potentialdifferenzen in Flammengasen und einigen festen Elektrolyten

Ohne Zusammenfassung     

A general perturbation theory for large discrete linear dynamical systems

Summary Large discrete linear dynamical systems are described by the equation of motion with symmetrical and non-symmetrical matrices. With the solution of the associated right-hand eigenproblem state transition matrix is calculated in an efficient manner, because a complex inversion of a big matrix is substituted by three small, real inversions. Now the system is assumed to be altered. The new parameters cause a change of system matrices. The new eigenvalues and eigenvectors are represented as sums of unperturbed and perturbational terms up to fourth order. Inserting yields algebraic equations arranged in the order of perturbation. They are solved successively by expanding the perturbation eigenvectors in terms of unperturbed ones and employing the appropriately defined left-hand eigenvectors. The perturbation-eigenvalues are obtained directly from simple quotients, the expansion coefficients are solutions of linear systems of equations. Repeated solution of the eigenproblem is unnecessary. For special systems formulas become even more simple. Perturbed modal matrix of state equation and its inverse are represented as simple sums. Hence, also the state transition matrix of the altered system is known.

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Eine allgemeine Störungsrechnung für diskrete, lineare Vielfreiheitsgradsysteme

Übersicht Ein diskretes, lineares, mechanisches Vielfreiheitsgradsystem ist durch die Bewegungsgleichung mit Matrizen beliebiger Symmetrieeigenschaften beschrieben. Aus der Lösung des zugeordneten RechtsEigenproblems folgt die Überführungsmatrix, welche effizient durch Ersatz der komplexen Inversion einer großen Matrix durch drei kleine, reelle Inversionen berechnet wird. Nun wird das System verändert, die neuen Parameter bewirken geänderte Systemmatrizen. Die neuen Eigenwerte und Eigenvektoren werden als Summen der ungestörten und der Störungsgrößen bis vierter Ordnung angesetzt. Einsetzen liefert nach der Ordnung der Störung sortierte algebraische Gleichungssysteme. Diese werden durch Entwicklung der Störungsvektoren nach den ungestörten Eigenvektoren sukzessive gelöst, wobei geeignet definierte Links-Eigenvektoren verwendet werden. Die Störungen der Eigenwerte sind direkt aus einfachen Quotienten berechenbar, die Entwicklungskoeffizienten folgen aus linearen Gleichungssystemen ohne neuerlicher Lösung eines Eigenproblems. Die gestörte Modalmatrix der Zustandsgleichung und ihre Inverse werden als einfache Summen dargestellt. Damit ist auch die Überführungsmatrix des geänderten Systems bekannt.