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Advanced Techniques for Propositional Satisfiability

In the past, economy and performance have been the main driving factors in the development of mass products and services, while energy and ecology aspects have not been considered as much. Notwithstanding this approach, Information and Communication Technologies (ICT) have been historically and fairly considered as a key objective to reduce and monitor "third-party" energy wastes and achieve higher levels of efficiency. However, until recently, ICT has not applied the same efficiency concepts to itself, not even in fast growing sectors like telecommunications and Internet. In the last year, the energy consumption of the ICT sector has been increasing; it is estimated to account for 2% of the total energy consumption. An even more aggressively increasing trend is the volume of Internet traffic and the number of connected devices. Thus, reducing the energy needs of the Internet is recognised as one of the main challenges that the ICT sector will have to face in the near future to reduce its overall energy footprint. Introducing energy-efficient techniques, both at the device level and the network level, is required. In this context, the challenges of my Ph.D. are the investigation, study and development of new techniques for the optimal exploitation of green networking capabilities in Future Internet devices, focusing on wired network elements. During the past three years, I addressed the problem of the energy consumption in network devices with several activities, which can be classified into three different categories. The main part of my research activities are related to the "low Energy COnsumption NETworks" (ECONET) project where I worked as a staff member of the TNT (Telecommunication Networks and Telematics) Laboratory of the University of Genoa (UNIGE) and member of the CNIT (Consorzio Nazionale Interuniversitario per le Telecomunicazioni), the Italian InterUniversity Consortium for Telecommunications. Inside this project, I am one of the most active members in the implementation of energy-aware mechanisms for network devices. Indeed, this thesis describes in detail what I have developed within the project. Motivated by the above considerations about the energy consumption issues, we established a partnership with a group of primary device manufacturers and TELCOs to launch the ECONET initiative. The main aim is to design and develop innovative solutions and device prototypes for wired network devices. The resulting network platforms will adopt Green Network Technologies (GNTs) for aggressively modulating power consumption according to actual workloads and service requirements. In particular, our efforts are focused on the investigation, development, and testing of new capabilities for the Future Internet devices that can enable the efficient management of power consumption, so to strongly reduce the current network energy waste. The ECONET project will therefore be devoted at re-thinking and re-designing wired network equipment and infrastructures toward more energy-sustainable and eco-friendly technologies and perspectives. The overall idea is to introduce novel "green" network-specific paradigms and concepts enabling the reduction of energy requirements of wired network equipment by 50% in the short to mid-term (and by 80% in the long run) with respect to the Business-as-Usual (BAU) scenario. Therefore, this thesis covers in detail the main results that were obtained during the Ph.D. activities. I exploited dynamic adaptive technologies for wired network devices that allow saving energy when a device (or part of it) is not used. The largest part of undertaken approaches is founded on few base concepts, which have been generally inspired by energy-saving mechanisms and power management criteria that are already partially available in computing systems. These base concepts can be classified as follows: re-engineering, dynamic adaptation (DA), and sleeping/stand-by. Re-engineering approaches aim at introducing and designing more energy-efficient elements for network device architectures, at suitably dimensioning and optimizing the internal organization of devices, as well as at reducing their intrinsic complexity levels. The dynamic adaptation (DA) of network/device resources is designed to modulate capacities of packet processing engines and of network interfaces, to meet actual traffic loads and requirements. This can be performed by using two power-aware capabilities, namely, Performance Scaling (PS) and Idle Logic (IL), which both allow the dynamic trade-off between packet service performance and power consumption. Finally, sleeping/stand-by approaches are used to smartly and selectively drive unused network/device portions to low stand-by modes, and to wake them up only if necessary.

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Sommario “Gli uomini comuni guardano le cose nuove con occhio vecchio. L’uomo creativo guarda le cose vecchie con occhio nuovo. G.P. Bona Sommario Il problema di soddisfacibilita` proposizionale (Sat) consiste nella risoluzione di una formula espressa in logica proposizionale. L’obiettivo e` la risposta alla seguente domanda: esiste un assegnamento delle variabili che possa soddisfare tale formula? Ugualmente importante e` individuare se tale assegnamento non esiste, arrivando a concludere che la funzione espressa dalla formula e` identica- mente “falsa” per tutti i possibili assegnamenti delle sue variabili. In questo ultimo caso si dice che la funzione e` insoddisfacibile, altrimenti e` soddisfacibile. Il problema Sat appartiene alla classe di complessita` Np-completa. I problemi Np-completi sono i piu` difficili della classe Np (non deterministici a tempo polinomiale). Hanno grande importanza sia teorica che pratica; se si trovasse un algoritmo in grado di risolvere in tempo polinomiale un qualsiasi problema Np-completo allora sarebbe possibile utilizzarlo per risolvere qua- lunque problema Np. La classe Np si riferisce a quei problemi che possono essere risolti in tempo polinomiale attraverso un algoritmo non deterministico. Nella pratica, nel caso peggiore, sono quindi risolti in tempo esponenziale. Il problema Sat e` di fondamentale importanza in un ampio spettro di settori dell’informatica, che vanno dall’informatica teorica [1] agli algoritmi ii

Laurea liv.II (specialistica)

Facoltà: Ingegneria

Autore: Alessandro Carrega Contatta »

Composta da 189 pagine.


Questa tesi ha raggiunto 164 click dal 06/02/2009.

Disponibile in PDF, la consultazione è esclusivamente in formato digitale.