35 research outputs found

    Convolution Model of a Queueing System with the cFIFO Service Discipline

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    Journal of Telecommunications and Information Technology, 2003, nr 3

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    kwartalni

    Journal of Telecommunications and Information Technology, 2009, nr 3

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    kwartalni

    On-board B-ISDN fast packet switching architectures. Phase 1: Study

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    The broadband integrate services digital network (B-ISDN) is an emerging telecommunications technology that will meet most of the telecommunications networking needs in the mid-1990's to early next century. The satellite-based system is well positioned for providing B-ISDN service with its inherent capabilities of point-to-multipoint and broadcast transmission, virtually unlimited connectivity between any two points within a beam coverage, short deployment time of communications facility, flexible and dynamic reallocation of space segment capacity, and distance insensitive cost. On-board processing satellites, particularly in a multiple spot beam environment, will provide enhanced connectivity, better performance, optimized access and transmission link design, and lower user service cost. The following are described: the user and network aspects of broadband services; the current development status in broadband services; various satellite network architectures including system design issues; and various fast packet switch architectures and their detail designs

    Stochastig modeling with continuous feedback markov fluid queues

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    Cataloged from PDF version of article.Markov fluid queues (MFQ) are systems in which a continuous-time Markov chain determines the net rate into (or out of ) a buffer. We deal with continuous feedback MFQs (CFMFQ) for which the infinitesimal generator of the background process and the drifts in each state are allowed to depend on the buffer level through continuous functions. Explicit solutions of CFMFQs for a few special cases has been reported, but usually numerical methods are preferred. A numerically stable solution method based on ordered Schur decomposition is already known for multi-regime MFQs (MRMFQ). We propose a framework for approximating CFMFQs by MRMFQs via discretizing the buffer space. The parameters of the CFMFQ are approximated by piecewise constant functions. Then, the solution is obtained by block-tridiagonal LU decomposition for the related MRMFQ. Moreover, we describe a numerical method that enables us to solve large scale systems efficiently. We model basically two different stochastic systems with CFMFQs. The first is the workload-bounded MAP/PH/1 queue, to which the arrivals occur according to a workload-dependent MAP (Markovian Arrival Process), and the arriving job size distribution is phase-type. The jobs that would cause the buffer to overflow are rejected partially or completely. Also, the service speed is allowed to depend on the buffer level. As the second application, we model the horizon-based delayed reservation mechanism in Optical Burst Switching networks with or without fiber delay lines. We allow multiple traffic classes and the effect of offset-based and FDL-based differentiation among traffic classes in terms of burst blocking is investigated. Lastly, we propose a distributed algorithm for air-time fairness in multi-rate WLANs that overcomes the performance anomaly in IEEE 802.11 WLANs. We also give a stochastic model of the proposed model, and provide a novel and elaborate proof for its effectiveness. We also present an extensive simulation study.Yazıcı, Mehmet AkifPh.D

    Design, testing and performance analisys of efficient lock-free solutions for multi-core Linux scheduler

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    Multiprocessor systems are nowadays de facto standard for both personal computers and server workstations. Benefits of multi-core technology has recently been used for embedded devices and cellular phones as well. Linux has not been originally designed to be a Real-Time Operating System (RTOS) but, recently, a new scheduling class, named SCHED_DEADLINE, was added to it. SCHED_DEADLINE is an implementation of the well known Earliest Deadline First algorithm. In this thesis we first present PRACTISE, a tool for developing, debugging, testing and analyse real-time scheduling data structures in user space. Unlike other similar tools, PRACTISE executes code in parallel, allowing to test and analyse the performance of the code in a realistic multiprocessor scenario. We also show an implementation of a skiplist, realized with the help of the tool above. This implementation is intended to be used for processes migration among the CPUs in SCHED_DEADLINE. To effectively manage the concurrent accesses to the data structure we used a revised version of the flat combining framework

    Access to telecommunications markets: the interrelation between general competition rules and sector-specific rules In the EU and Japan

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    The starting point of the thesis is the key competition law issues that arise in relation to access to telecommunications markets in the EU and Japan. This issue is presently regulated in the EU and Japan by a dual regime combining general competition law regulation and sector-specific regulation aimed at opening up the markets. Chapter 1 analyses the relevant general competition rules (i.e. dominance and its abuse, including the doctrine of essential facilities) and the relevant sector-specific rules (i.e. interconnection) that apply to access to EU telecommunications markets. Chapter 2 does the same exercise for Japan through the analysis of the relevant general competition rules (i.e. refusal to deal) and sector-specific rules (i.e. general market access regulation and interconnection) that apply to access to Japanese telecommunications markets. The analysis described above leads to the core object of the thesis which is the study, undertaken at Chapter 3, of the interrelation between general competition rules and sector-specific rules as they apply to access to telecommunications markets in the EU and Japan. This thesis will argue that the dual regime presently regulating access to the EU and Japanese telecommunications industries needs to be maintained. However, the increasing complexity and dynamic character of the telecommunications industry means that a change in the current interrelation between the two types of regulation is necessary. It will be argued that the future balance between the two types of regulation should be one where sector-specific rules will increasingly serve limited functions and where general competition rules will progressively take precedence over the regulation of third party access to telecommunications markets
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