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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Queueing systems 23 (1996), S. 301-316 
    ISSN: 1572-9443
    Keywords: M/G/1 queue ; negative customers ; queue length ; Wiener-Hopf technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Two variants of an M/G/1 queue with negative customers lead to the study of a random walkX n+1=[X n +ξ n ]+ where the integer-valuedξ n are not bounded from below or from above, and are distributed differently in the interior of the state-space and on the boundary. Their generating functions are assumed to be rational. We give a simple closed-form formula for $$\mathbb{E}(s^{X_n } )$$ , corresponding to a representation of the data which is suitable for the queueing model. Alternative representations and derivations are discussed. With this formula, we calculate the queue length generating function of an M/G/1 queue with negative customers, in which the negative customers can remove ordinary customers only at the end of a service. If the service is exponential, the arbitrarytime queue length distribution is a mixture of two geometrical distributions.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Queueing systems 23 (1996), S. 293-300 
    ISSN: 1572-9443
    Keywords: Probability generating function (of a Laurent series form) ; factorization ; quotient factorization ; ladder-heights
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This note is concerned with the identification of the Wiener-Hopf factors of a function 1−f, wheref generates an aperiodic distribution on the integers with a negative mean. The general and rational cases are addressed. We give a concise summary of the main practical facts needed for calculations involving the Wiener-Hopf factors. The basic facts are cited from the literature, but a few aspects are briefly proven here.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Queueing systems 27 (1997), S. 251-269 
    ISSN: 1572-9443
    Keywords: closed queueing networks ; branching processes ; nearly complete decomposability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A new class of models, which combines closed queueing networks with branching processes, is introduced. The motivation comes from MIMD computers and other service systems in which the arrival of new work is always triggered by the completion of former work, and the amount of arriving work is variable. In the variant of branching/queueing networks studied here, a customer branches into a random and state-independent number of offspring upon completing its service. The process regenerates whenever the population becomes extinct. Implications for less rudimentary variants are discussed. The ergodicity of the network and several other aspects are related to the expected total number of progeny of an associated multitype Galton-Watson process. We give a formula for that expected number of progeny. The objects of main interest are the stationary state distribution and the throughputs. Closed-form solutions are available for the multi-server single-node model, and for homogeneous networks of infinite-servers. Generally, branching/queueing networks do not seem to have a product-form state distribution. We propose a conditional product-form approximation, and show that it is approached as a limit by branching/queueing networks with a slowly varying population size. The proof demonstrates an application of the nearly complete decomposability paradigm to an infinite state space.
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2014-10-20
    Description: The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an imaging limb emission sounder operating in the thermal infrared region. It is designed to provide measurements of the upper troposphere/lower stratosphere with high spatial and high spectral resolution. The instrument consists of an imaging Fourier transform spectrometer integrated into a gimbal. The assembly can be mounted in the belly pod of the German High Altitude and Long Range research aircraft (HALO) and in instrument bays of the Russian M55 Geophysica. Measurements are made in two distinct modes: the chemistry mode emphasises chemical analysis with high spectral resolution, and the dynamics mode focuses on dynamical processes of the atmosphere with very high spatial resolution. In addition, the instrument allows tomographic analyses of air volumes. The first measurement campaigns have shown compliance with key performance and operational requirements.
    Print ISSN: 1867-1381
    Electronic ISSN: 1867-8548
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 5
    Publication Date: 2015-11-03
    Description: Der flächendeckende Betrieb mehrerer Mobilfunknetze unterschiedlicher Technologie in einem Land sorgt aufgrund der ständigen Bereithaltung von Übertragungskapazität für Dienste mit zunehmend höherem Datenvolumenbedarf für einen erheblichen Energieverbrauch. Das Forschungsförderungsprojekt ComGreen hat sich zur Aufgabe gesetzt, durch lastadaptiven Betrieb und intelligente dynamische Rekonfiguration des Funkzugangsnetzes zur Energieeinsparung beizutragen. Konzept, Herausforderungen, ausgewählte Ergebnisse von Simulationen und prototypischem Betrieb werden ebenso wie typische Erwartungswerte des künftigen Energieverbrauchs im Mobilfunkbereich vorgestellt. Sowohl Berechnungen als auch Messungen zeigen, dass durch kontext-basierte dynamische Rekonfiguration von zellularen Funknetzen Energieeinsparungen im Bereich von 25–40 % ermöglicht werden.
    Print ISSN: 1684-9965
    Electronic ISSN: 1684-9973
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 6
    Publication Date: 2011-08-01
    Description: Provision of mobile and wireless services today within a competitive environment and driven by a huge amount of steadily emerging new services and applications is both challenge and chance for radio network operators. Deployment and operation of an infrastructure for mobile and wireless broadband connectivity generally requires planning effort and large investments. A promising approach to reduce expenses for radio access networking is offered by Wireless Mesh Networks (WMNs). Here traditional dedicated backhaul connections to each access point are replaced by wireless multi-hop links between neighbouring access nodes and few gateways to the backbone employing standard radio technology. Such a solution provides at the same time high flexibility in both deployment and the amount of offered capacity and shall reduce overall expenses. On the other hand currently available mesh solutions do not provide carrier grade service quality and reliability and often fail to cope with high traffic load. EU project CARMEN (CARrier grade MEsh Networks) was initiated to incorporate different heterogeneous technologies and new protocols to allow for reliable transmission over "best effort" radio channels, to support a reliable mobility and network management, self-configuration and dynamic resource usage, and thus to offer a permanent or temporary broadband access at high cost efficiency. The contribution provides an overview on preliminary project results with focus on main technical challenges from a research and implementation point of view. Especially impact of mesh topology on the overall system performance in terms of throughput and connection reliability and aspects of a dedicated hybrid mobility management solution will be discussed.
    Print ISSN: 1684-9965
    Electronic ISSN: 1684-9973
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 7
    Publication Date: 2014-03-07
    Description: The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an imaging limb emission sounder operating in the thermal infrared region. It is designed to provide measurements of the Upper Troposphere/Lower Stratosphere with high spatial and high spectral resolution. The instrument consists of an imaging Fourier transform spectrometer integrated in a gimbal. The assembly can be mounted in the belly pod of the German high altitude and long range research aircraft HALO and in instrument bays of the Russian M55 Geophysica. Measurements are made predominantly in two distinct modes: the chemistry mode emphasises chemical analysis with high spectral resolution, the dynamics mode focuses on dynamical processes of the atmosphere with very high spatial resolution. In addition the instrument allows tomographic analyses of air volumes. The first measurement campaigns have shown compliance with key performance and operational requirements.
    Electronic ISSN: 1867-8610
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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