187,015 research outputs found

    Fluid limits for networks with bandwidth sharing and general document size distributions

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    We consider a stochastic model of Internet congestion control, introduced by Massouli\'{e} and Roberts [Telecommunication Systems 15 (2000) 185--201], that represents the randomly varying number of flows in a network where bandwidth is shared among document transfers. In contrast to an earlier work by Kelly and Williams [Ann. Appl. Probab. 14 (2004) 1055--1083], the present paper allows interarrival times and document sizes to be generally distributed, rather than exponentially distributed. Furthermore, we allow a fairly general class of bandwidth sharing policies that includes the weighted α\alpha-fair policies of Mo and Walrand [IEEE/ACM Transactions on Networking 8 (2000) 556--567], as well as certain other utility based scheduling policies. To describe the evolution of the system, measure valued processes are used to keep track of the residual document sizes of all flows through the network. We propose a fluid model (or formal functional law of large numbers approximation) associated with the stochastic flow level model. Under mild conditions, we show that the appropriately rescaled measure valued processes corresponding to a sequence of such models (with fixed network structure) are tight, and that any weak limit point of the sequence is almost surely a fluid model solution. For the special case of weighted α\alpha-fair policies, we also characterize the invariant states of the fluid model.Comment: Published in at http://dx.doi.org/10.1214/08-AAP541 the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

    Testing Embedded Memories in Telecommunication Systems

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    Extensive system testing is mandatory nowadays to achieve high product quality. Telecommunication systems are particularly sensitive to such a requirement; to maintain market competitiveness, manufacturers need to combine reduced costs, shorter life cycles, advanced technologies, and high quality. Moreover, strict reliability constraints usually impose very low fault latencies and a high degree of fault detection for both permanent and transient faults. This article analyzes major problems related to testing complex telecommunication systems, with particular emphasis on their memory modules, often so critical from the reliability point of view. In particular, advanced BIST-based solutions are analyzed, and two significant industrial case studies presente

    Telecommunication Systems

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    This book is based on both industrial and academic research efforts in which a number of recent advancements and rare insights into telecommunication systems are well presented. The volume is organized into four parts: "Telecommunication Protocol, Optimization, and Security Frameworks", "Next-Generation Optical Access Technologies", "Convergence of Wireless-Optical Networks" and "Advanced Relay and Antenna Systems for Smart Networks." Chapters within these parts are self-contained and cross-referenced to facilitate further study

    Managing ubiquitous eco cities: the role of urban telecommunication infrastructure networks and convergence technologies

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    A successful urban management system for a Ubiquitous Eco City requires an integrated approach. This integration includes bringing together economic, socio-cultural and urban development with a well orchestrated, transparent and open decision making mechanism and necessary infrastructure and technologies. Rapidly developing information and telecommunication technologies and their platforms in the late 20th Century improves urban management and enhances the quality of life and place. Telecommunication technologies provide an important base for monitoring and managing activities over wired, wireless or fibre-optic networks. Particularly technology convergence creates new ways in which the information and telecommunication technologies are used. The 21st Century is an era where information has converged, in which people are able to access a variety of services, including internet and location based services, through multi-functional devices such as mobile phones and provides opportunities in the management of Ubiquitous Eco Cities. This paper discusses the recent developments in telecommunication networks and trends in convergence technologies and their implications on the management of Ubiquitous Eco Cities and how this technological shift is likely to be beneficial in improving the quality of life and place. The paper also introduces recent approaches on urban management systems, such as intelligent urban management systems, that are suitable for Ubiquitous Eco Cities

    Datacab: a geographical‐information‐system‐based expert system for the design of cable networks

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    Telecommunication networks have evolved over time as a result of technological advances, and network topologies and equipment have become increasingly complex. Expert systems are being successfully applied to the management of telecommunication networks. However, applying expert systems to network design is another especially beneficial yet still not very common approach. In this paper we propose a rule‐based expert system called Datacab. Datacab was developed at Enditel Endesa in collaboration with the Electronic Technology Department of the University of Seville, for the automatic design of hybrid fibre coax (HFC) cable networks. Using data from a geographical information system as input, it automatically generates viable HFC network designs

    Telecommunications Division

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    Spacecraft telecommunication systems - coding methods for phase locked loops, absolute time determination by pulsar, communications elements researc

    Data security for third generation telecommunication systems

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    This research work started as a humble, and yet ambitious attempt of enhancing the current security level in wireless data communication. Detailed analysis of the existing security protocols and wireless networks, together with their strengths and weaknesses, presented in the beginning of this thesis, indicates the need of employing human voice as an alternative security solution. Consequently the presentation of the state of the art biometric solutions and their applicability to the desired communication medium is more than necessary. However, the lack of previous involvement of human voice in an encryption method with successful results, constitute the core of this work. The majority of biometric applications aim to improve the confidence of the system to know whether a user is who he or she claims to be (authentication) and a few of them help the system in deciding his/her identity (identification). This novel method of encryption combines wireless communication (especially Third Generation mobile phones), data security, digital signal processing and smart cards. All these four different research areas have been covered theoretically in the beginning of this thesis. Thorough discussion of the fundamental principles governing each area results in identifying the strengths and weaknesses of these four core research elements and benefits the implementation stages of this work. Continuing with the thesis and proceeding to the second part, the theoretical analysis has been backed up by experimental development and testing. Every aspect of the novel research architecture has been transformed into a research algorithm. The performance of the algorithm, its cohesion and coupling has been closely investigated. The overall result of the research work accompanied with the algorithm’s strengths and weaknesses, future directions together with possible applicability of the research solution provide the epilogue of this scientific journey has been discussed
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