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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Circuit Design of Fast Fourier Transform for DVB-H Systems

Tseng, Wei-Chen 05 March 2009 (has links)
A circuit design of Fast Fourier Transform for DVB-H system is presented in this thesis. This circuit is based on SDF (single path delay feedback) pipeline architecture with radix-2 computation element. We propose a novel method of timing scheduling that can share one complex multiplier for couple of stage and promote the utilization of complex multiplier to 100%, so we can improve the implementation with radix-2 computation. The number of bits is carefully selected by system simulation to meetthe requirements of DVB-H system. In addition, a memory table permutation deletion method for memory scheduling, which can reduce the size of memory storing twiddle factors tables. The circuit is carried out by CMOS 0.18£gm 1P6M process with core area 2.08 x 2.076 mm2. In the gate level simulation, the output data rate of this circuit is above 50MHz, so the circuit can meet the requirement of DVB-H system.
2

Models and methods for Traffic Engineering problems with single-path routing

Barros Joyce Moniz, Martim 06 October 2016 (has links)
Traffic Engineering (TE) uses methods and models from a variety of mathematical fields, such as statistics and optimization, to improve the performance of telecommunication networks. In this thesis, we study TE problems dealing with networks that impose single-path routing. As the name infers, in this type of routing, the traffic flow of each "commodity" cannot be split in its path between its origin and destination. Given its cheap cost, single-path routing is widely used in today's data centers, where thousands of stored servers perform computations or host Internet services. One common case of single-path routing is the one enforced by the Spanning Tree Protocol (STP) in switched Ethernet networks. The STP requires the network to keep its activated links loop-free, while maintaining the other redundant links ready for back-up, in case of link failure. The Multiple Spanning Tree Protocol (MSTP) extends the STP by installing multiple virtual networks compliant with the STP, over a single physical topology. Therefore, the MSTP is greatly beneficial for network service providers, as it allows for a more efficient use of the existing resources.Network design problems dealing with the MSTP are generally highly combinatorial and very hard to solve. As such, TE literature mainly suggests heuristic methods, which can quickly produce reasonable designs. Notwithstanding, due to a scarce existence of lower bounds to the optimum values of such problems, there is little knowledge about the quality of the solutions provided by these heuristics.In this sense, we propose mathematical programming models and methods that can provide optimal designs for these networks, or at the very least, obtain valid lower bounds. Taking into mind the goal of avoiding congestion in the network, we focus on two problems that deal with the following load-balancing objectives: the minimization of the worst-case link utilization, and the minimization of flow costs given by piecewise linear functions that penalize heavily-loaded links. The study of both these problems yielded relevant by-products: the first is the study of a MSTP network design problem, where we minimize the total load, and the second is the study of a fundamental unsplittable multicommodity flow problem with piecewise linear costs.For all the considered problems, we provide studies of complexity, extensive polyhedral studies to compare the proposed formulations, and a wide array of computational experiments to evaluate the performance of the proposed models and methods. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished
3

Energy-aware scheduling : complexity and algorithms

Renaud-Goud, Paul 05 July 2012 (has links) (PDF)
In this thesis we have tackled a few scheduling problems under energy constraint, since the energy issue is becoming crucial, for both economical and environmental reasons. In the first chapter, we exhibit tight bounds on the energy metric of a classical algorithm that minimizes the makespan of independent tasks. In the second chapter, we schedule several independent but concurrent pipelined applications and address problems combining multiple criteria, which are period, latency and energy. We perform an exhaustive complexity study and describe the performance of new heuristics. In the third chapter, we study the replica placement problem in a tree network. We try to minimize the energy consumption in a dynamic frame. After a complexity study, we confirm the quality of our heuristics through a complete set of simulations. In the fourth chapter, we come back to streaming applications, but in the form of series-parallel graphs, and try to map them onto a chip multiprocessor. The design of a polynomial algorithm on a simple problem allows us to derive heuristics on the most general problem, whose NP-completeness has been proven. In the fifth chapter, we study energy bounds of different routing policies in chip multiprocessors, compared to the classical XY routing, and develop new routing heuristics. In the last chapter, we compare the performance of different algorithms of the literature that tackle the problem of mapping DAG applications to minimize the energy consumption.
4

Energy-aware scheduling : complexity and algorithms / Ordonnancement sous contrainte d'énergie : complexité et algorithmes

Renaud-Goud, Paul 05 July 2012 (has links)
Dans cette thèse, nous nous sommes intéressés à des problèmes d'ordonnancement sous contrainte d'énergie, puisque la réduction de l'énergie est devenue une nécessité, tant sur le plan économique qu'écologique. Dans le premier chapitre, nous exhibons des bornes strictes sur l'énergie d'un algorithme classique qui minimise le temps d'exécution de tâches indépendantes. Dans le second chapitre, nous ordonnançons plusieurs applications chaînées de type « streaming », et nous étudions des problèmes contraignant l'énergie, la période et la latence. Nous effectuons une étude de complexité exhaustive, et décrivons les performances de nouvelles heuristiques. Dans le troisième chapitre, nous étudions le problème de placement de répliques dans un réseau arborescent. Nous nous plaçons dans un cadre dynamique, et nous bornons à minimiser l'énergie. Après une étude de complexité, nous confirmons la qualité de nos heuristiques grâce à un jeu complet de simulations. Dans le quatrième chapitre, nous revenons aux applications « streaming », mais sous forme de graphes série-parallèles, et nous tentons de les placer sur un processeur multi-cœur. La découverte d'un algorithme polynomial sur un problème simple nous permet la conception d'heuristiques sur le problème le plus général dont nous avons établi la NP-complétude. Dans le cinquième chapitre, nous étudions des bornes énergétiques de politiques de routage dans des processeurs multi-cœurs, en comparaison avec le routage classique XY, et développons de nouvheuristiques de routage. Dans le dernier chapitre, nous étudions expérimentalement le placement d'applications sous forme de DAG sur des machines réelles. / In this thesis we have tackled a few scheduling problems under energy constraint, since the energy issue is becoming crucial, for both economical and environmental reasons. In the first chapter, we exhibit tight bounds on the energy metric of a classical algorithm that minimizes the makespan of independent tasks. In the second chapter, we schedule several independent but concurrent pipelined applications and address problems combining multiple criteria, which are period, latency and energy. We perform an exhaustive complexity study and describe the performance of new heuristics. In the third chapter, we study the replica placement problem in a tree network. We try to minimize the energy consumption in a dynamic frame. After a complexity study, we confirm the quality of our heuristics through a complete set of simulations. In the fourth chapter, we come back to streaming applications, but in the form of series-parallel graphs, and try to map them onto a chip multiprocessor. The design of a polynomial algorithm on a simple problem allows us to derive heuristics on the most general problem, whose NP-completeness has been proven. In the fifth chapter, we study energy bounds of different routing policies in chip multiprocessors, compared to the classical XY routing, and develop new routing heuristics. In the last chapter, we compare the performance of different algorithms of the literature that tackle the problem of mapping DAG applications to minimize the energy consumption.

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