abstract: The electric transmission grid is conventionally treated as a fixed asset and is operated around a single topology. Though several instances of switching transmission lines for corrective mechaism, congestion management, and minimization of losses can be found in literature, the idea of co-optimizing transmission with generation dispatch has not been widely investigated. Network topology optimization exploits the redundancies that are an integral part of the network to allow for improvement in dispatch efficiency. Although, the concept of a dispatchable network initially appears counterintuitive questioning the wisdom of switching transmission lines on a more regu-lar basis, results obtained in the previous research on transmission switching with a Direct Current Optimal Power Flow (DCOPF) show significant cost reductions. This thesis on network topology optimization with ACOPF emphasizes the need for additional research in this area. It examines the performance of network topology optimization in an Alternating Current (AC) setting and its impact on various parameters like active power loss and voltages that are ignored in the DC setting. An ACOPF model, with binary variables representing the status of transmission lines incorporated into the formulation, is written in AMPL, a mathematical programming language and this optimization problem is solved using the solver KNITRO. ACOPF is a non-convex, nonlinear optimization problem, making it a very hard problem to solve. The introduction of bi-nary variables makes ACOPF a mixed integer nonlinear programming problem, further increasing the complexity of the optimization problem. An iterative method of opening each transmission line individually before choosing the best solution has been proposed as a purely investigative approach to studying the impact of transmission switching with ACOPF. Economic savings of up to 6% achieved using this approach indicate the potential of this concept. In addition, a heuristic has been proposed to improve the computational efficiency of network topology optimization. This research also makes a comparative analysis between transmission switching in a DC setting and switching in an AC setting. Results presented in this thesis indicate significant economic savings achieved by controlled topology optimization, thereby reconfirming the need for further examination of this idea. / Dissertation/Thesis / M.S. Electrical Engineering 2011

Depuis plusieurs années, l’aéronautique est confrontée à une mutation majeure due à l’émergence des matériaux composites. Ce changement, justifié par les excellentes propriétés mécaniques des matériaux composites et un gain de masse important, implique une révision complète des réseaux de retour de courant. Pour faciliter cette révision, la thèse propose de lier au travers de l’analyse spectrale des graphes les performances des réseaux électriques avec leur topologie. Deux objectifs couplés sont étudiés : un dimensionnement topologique visant un bon compromis masse/robustesse et une stratégie de surveillance de ces réseaux. / The principles of the electrical system design in future aircrafts have to be reconsidered due to the emergence of new composite materials. The use of these materials for the aircraft structure has indeed implied a complete revision of on-board current return path networks. To facilitate this revision, it is proposed to link through the spectral graph analysis the performances of electrical networks with their topology. The aim of this thesis is to give topological drivers that could help the aeronautical engineers during the design process and then to propose a monitoring methodology.

Magister Scientiae - MSc / This thesis demonstrates that a situation-aware algorithm improves quality of service on small mesh networks running BATMAN-adv with some mobile nodes. BATMAN-adv is a proactive mesh routing protocol that counts beacons as a link quality metric. BATMAN-adv was modi ed to give more recently received beacons more weight, thereby calculating a more precise indication of the current state of a link that BATMAN-adv can use to forward packets. BATMAN-adv `original' was compared with a situation-aware version in two laboratory test beds with the same voice traffic profile on actual hardware with a realistic voice traffic profile; with controlled transmission rates and buffer sizes to simulate congestion. The second test bed included mesh potatoes, PCs and laptops as mobile nodes. BATMAN-adv achieved better jitter and packet loss than the situation-aware version in the initial, smaller test bed, and average throughput for both versions was almost identical. However, in the second slightly larger test bed, with additional mobile nodes, the situation-aware algorithm performed better than the original BATMAN-adv algorithm for all quality of service metrics, including throughput. Thus the thesis concludes that a situation-aware protocol offers a promising solution to address issues pertaining to mobility, congestion and scalability for voice traffic in mesh networks with mobile nodes. / South Africa

In-band full-duplex (FD) communications have been optimistically promoted to improve the spectrum utilization and efficiency. However, the penetration of FD communications to the cellular networks domain is challenging due to the imposed uplink/downlink interference. This thesis presents a tractable framework, based on stochastic geometry, to study FD communications in multi-tier cellular networks. Particularly, we assess the FD communications effect on the network performance and quantify the associated gains. The study proves the vulnerability of the uplink to the downlink interference and shows that the improved FD rate gains harvested in the downlink (up to 97%) comes at the expense of a significant degradation in the uplink rate (up to 94%). Therefore, we propose a novel fine-grained duplexing scheme, denoted as α-duplex scheme, which allows a partial overlap between the uplink and the downlink frequency bands. We derive the required conditions to harvest rate gains from the α-duplex scheme and show its superiority to both the FD and half-duplex (HD) schemes. In particular, we show that the α-duplex scheme provides a simultaneous improvement of 28% for the downlink rate and 56% for the uplink rate. We also show that the amount of the overlap can be optimized based on the network design objective. Moreover, backward compatibility is an essential ingredient for the success of new technologies. In the context of in-band FD communication, FD base stations (BSs) should support HD users' equipment (UEs) without sacrificing the foreseen FD gains. The results show that FD-UEs are not necessarily required to harvest rate gains from FD-BSs. In particular, the results show that adding FD-UEs to FD-BSs offers a maximum of 5% rate gain over FD-BSs and HD-UEs case, which is a marginal gain compared to the burden required to implement FD transceivers at the UEs' side. To this end, we shed light on practical scenarios where HD-UEs operation with FD-BSs outperforms the operation when both the BSs and UEs are FD and we find a closed form expression for the critical value of the self-interference cancellation power required for the FD UEs to outperform HD UEs.

Tesis por compendio / [EN] The study of Complex Systems is one of the scientific fields that has had the highest productivity in recent decades and has not ceased to fascinate the community dedicated to studying its properties. In particular, Network Science has proven to be one of the most prolific areas within Complex Systems. In recent years, his methods have been applied to model multiple phenomena in real life, both naturally generated, such as in biology, and due to the actions and interactions of man, such as social networks or communication networks. Recently, it has been seen how the methods of Network Science can be applied in the context of mathematics, as is the case of Number Theory. One of the most studied cases is networks whose elements are numbers and which are related through the divisibility relation. The main objective of this thesis is to extend these studies to other sets of numbers. On the one hand, we study the divisibility in natural numbers when we obtain these from Pascal matrices of increasing size, which allows us to extract non-sequential sets of numbers with non-constant increments between them. On the other hand, we study the case of the divisibility relation of rational numbers. Cantor's diagonal argument provides a way to order all rational numbers, which allows us to check to what extent some of the properties observed for the divisibility of natural numbers are extensible to a more general context. The thesis is divided into 4 Chapters. Chapter 1 contains a general introduction to the thesis and it is structured into 6 sections. In Sections 1.1 and 1.2, we briefly introduce Network Science, show some application examples, and motivate the study of networks of numbers generated from the divisibility property. In Section 1.3, we define the objectives of this PhD thesis and its scope. In Section 1.4, we present the notion of network, its representations, and some measures that can be calculated on them, such as nodes degrees, their distribution, the assortativity and the clustering coefficients. In another hand, in Section 1.5, we review the best-known network models such as Erdo¿s and Re'nyi random networks, Watts and Strogatz small-world networks, Baraba'si and Albert scale-free networks, and hierarchical networks. Finally, at the end of this Chapter 1, we show in Section 1.6 a review of various studies carried out in order to apply Network Science methods to problems and properties that arise in Number Theory, such as divisibility networks or networks generated from Collatz's Conjecture. or Goldbach's Strong Conjecture. In Chapters 2 and 3, we show the results obtained and that have been published to date. Finally, in Chapter 4, we summarize the conclusions obtained and indicate some related problems that we consider of interest to address in the future. / [ES] El estudio de los Sistemas Complejos es uno de los campos científicos que ha tenido mayor productividad en las últimas décadas y no ha dejado de fascinar a la comunidad que se dedica al estudio de sus propiedades. En particular, la Ciencia de Redes se ha mostrado como una de las áreas más prolíficas dentro de los Sistemas Complejos. En los últimos años, sus métodos han sido aplicados para modelar múltiples fenómenos de la vida real tanto generados de manera natural, como puede ser en el caso de la biología, como debidos a las acciones e interacciones del hombre, como puede ser el caso de las redes sociales o las redes de comunicaciones. Recientemente, se ha visto cómo los métodos de la Ciencia de Redes pueden ser aplicados en el contexto de las matemáticas, como es el caso de la Teoría de Números. Uno de los casos que más se han estudiado es el de las redes cuyos elementos son números y que se relacionan mediante la relación de la divisibilidad. El objetivo principal de esta tesis es extender estos estudios a otros conjuntos de números. Por una parte, estudiamos la divisibilidad en los números naturales cuando obtenemos estos a partir de subconjuntos de números naturales extraídos de matrices de Pascal de orden creciente, lo que nos permite extraer conjuntos de números de manera no secuencial y con incrementos no constantes entre ellos. Por otra parte, estudiamos el caso de la relación de divisibilidad de los números racionales, dado que a partir del argumento diagonal de Cantor se pueden ordenar, lo que nos permite comprobar hasta qué punto algunas de las propiedades observadas para la divisibilidad de los números naturales son extensibles a un contexto más general. La tesis se divide en 4 capítulos. El capítulo 1 contiene una introducción general a la tesis y está estructurado en 6 secciones. En las secciones 1.1 y 1.2, presentamos brevemente la Ciencia de Redes, mostrando algunos ejemplos de aplicación y motivamos el estudio de redes de números generadas a partir de la propiedad de divisibilidad. En la Section 1.3, definimos los objetivos de esta tesis doctoral y su alcance. En la sección 1.4, presentamos la noción de red, sus formas de representación y algunas medidas que se pueden calcular sobre ellas, como son los grados de los nodos, la distribución de estos grados, la asortatividad y los coeficientes de clustering. Por otro lado, en la Sección 1.5, revisamos los modelos de redes más conocidos como son las redes aleatorias de Erdös y Rényi, las redes de pequeño mundo de Watts y Strogatz, las redes libres de escala de Barabási y Albert y las redes jerárquicas. Mostramos en la Sección 1.6, una revisión de diversos estudios realizados con el fin de aplicar métodos de la Ciencia de Redes a problemas y propiedades que surgen en la Teoría de Números, como son las redes de divisibilidad o redes generadas a partir de la Conjetura de Collatz o la Conjetura Fuerte de Goldbach. En los Capítulos 2 y 3, mostramos los resultados obtenidos y que han sido publicados hasta la fecha y, finalmente, en el Capítulo 4, resumimos las conclusiones obtenidas e indicamos algunos problemas relacionados que consideramos de interés abordar en un futuro. / [CAT] L'estudi dels Sistemes Complexos és un dels camps científiques que ha tingut major productivitat en les últimes dècades i no ha deixat de fascinar a la comunitat que es dedica a l'estudi de les seues propietats. En particular, la Ciència de Xarxes s'ha mostrat com una de les àrees més prolífica dins dels Sistemes Complexos. En els últims anys, els seus mètodes han sigut aplicats per a modelar múltiples fenòmens de la vida real tant generats de manera natural, com pot ser en el cas de la biologia, com deguts a les accions i interaccions de l'home, com pot ser el cas de les xarxes socials o les xarxes de comunicacions. Recentment, s'ha vist com els mètodes de la Ciència de Xarxes poden ser aplicats en el context de les matemàtiques, com és el cas de la Teoria de Números. Un dels casos que més s'han estudiat és el de les xarxes els elements de les quals són números i que es relacionen mitjançant la relació de la divisibilitat. L'objectiu principal d'aquesta tesi és estendre aquests estudis a altres conjunts de números. D'una banda, estudiem la divisibilitat en els nombres naturals quan obtenim aquests a partir de matrius de Pascal de grandària creixent, la qual cosa ens permet extraure conjunts de números de manera no sequëncial i amb increments no constants entre ells. D'altra banda, estudiem el cas de la relació de divisibilitat dels nombres racionals, atés que a partir de l'argument diagonal de Cantor es poden ordenar, la qual cosa ens permet comprovar fins a quin punt algunes de les propietats observades per a la divisibilitat dels nombres naturals són extensibles a un context més general. La tesi es troba dividida en 4 Capítols. El capítol 1, conté una introducció general a la tesi i está estructurat en 6 seccions. En les seccions 1.1 i 1.2, presentem breument la Ciència de Xarxes, mostrant alguns exemples d'aplicació i motivem l'estudi de xarxes de números generades a partir de la propietat de divisibilitat. En la Section 1.3, definim els objectius d'aquesta tesi doctoral y el seu abast. En la Secció 1.4, presentem la noció de xarxa, les seves formes de representació i algunes mesures que es poden calcular sobre elles, com són els graus dels nodes, la distribució d'aquests graus, la asortatividad i els coeficients de clustering. En la Sección 1.5, revisem els models de xarxes més coneguts com són les xarxes aleatòries de Erdös i Renyi, les xarxes de xicotet món de Watts i Strogatz, les xarxes lliures d'escala de Barabási i Albert i les xarxes jeràrquiques. Mostrem en la Sección 1.6 una revisió de diversos estudis realitzats amb la finalitat d'aplicar mètodes de la Ciència de Xarxes a problemes i propietats que sorgeixen en la Teoria de Números, com són les xarxes de divisibilitat o xarxes generades a partir de la Conjectura de Collatz o la Conjectura Forta de Goldbach. En els Capítols 2 i 3, vam mostrar els resultats obtinguts i que han sigut publicats fins hui i, finalment, en el Capítol 4, resumim les conclusions obtingudes i indiquem alguns problemes relacionats que considerem d'interés abordar en un futur. / Solares Hernández, PA. (2021). Sets of numbers from complex networks perspective [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/176015 / TESIS / Compendio

Práce představuje model a metody analýzy vlasností komunikace v počítačových sítích. Model dosažitelnosti koncových prvků v IP sítích je vytvořen na základě konfigurace a síťové topologie a umožňuje ukázat, že vabraný koncový uzel je dosažitelný v dané síťové konfiguraci a stavu.   Prezentovaná práce se skládá ze dvou částí. První část se věnuje modelování sítí, chování směrovaích protokolů a síťové konfiguraci. V rámci modelu sítě byla vytvořena modifikovaná topologická tabulka (MTT), která slouží pro agregaci síťových stavů určených pro následnou analýzu. Pro analýzu byl použit přístup založený na logickém programování, kdy model sítě je převeden do Datalog popisu a vlastnosti jsou ověřovány kladením dotazů nad logickou databází. Přínosy práce spočívají v definici grafu síťových filtrů, modifikované topologické tabulce, redukce stavového prostoru agrgací síťových stavů, modelů aktivního síťového prvku jako filter-transformace komponenty a metoda pro analýzu dosažitelnosti založena na logickém programování a databázích.

Modern heterogeneous networks present a great challenge for network operators and engineers from a management and configuration perspective. The Tail-f Systems’ Network Control System (NCS) is a network management framework that addresses these challenges. NCS offers centralized network configuration management functionality, along with providing options for extending the framework with additional features. The devices managed by NCS are stored in its Configuration Database (CDB). However, currently there is no mechanism for automatically adding network devices to the configuration of NCS, thus each device’s management parameters have to be entered manually. The goal of this master’s thesis project is to develop a software module for NCS that simplifies the process of initial NCS configuration by allowing NCS to automatically add network devices to the NCS CDB. Apart from developing the software module for discovery, this project aims to summarize existing methods and to develop new methods for automated discovery of network devices with the main focus on differentiating between different types of devices. A credential-based device discovery method was developed and utilized to make advantage of known credentials to access devices, which allows for more precise discovery compared to some other existing methods. The selected methods were implemented as a component of NCS to provide device discovery functionality. Another focus of this master’s thesis project was the development of an approach to network topology discovery and its representation. The aim is to provide both a logical Internet Protocol (IP) network topology and a physical topology of device interconnections. The result is that we are able to automatically discover and store the topology representation as a data structure, and subsequently generate a visualization of the network topology. / Moderna heterogena nätverk utgör en stor utmaning för operatörer och ingenjörer att hantera och konfigurera. Tail-f Systems NCS produkt är ett ramverk för nätverks konfiguration som addresserar dessa utmaningar. NCS är ett centraliserat nätverks konfigurations verktyg. NCS är användbart som det är, men kan också byggas ut av användaren med ytterligare funktioner. De enheter som hanteras med NCS lagras i konfigurationsdatabasen (CDB). För närvarande finns det ingen automatiserad mekanism för att addera nätverksenheter till NCS, och varje enhets parametrar måste fyllas i manuellt. Detta examensarbetes mål är att utveckla en mjukvarumodul för NCS som förenklar NCS konfiguration genom att automatiskt lägga nätverksenheter till NCS CDB. Förutom att utveckla programvara för enhetsidentifiering, syftar detta projekt till att sammanfatta befintliga metoder och utveckla nya metoder för automatiserad nätverksenhetsidentifiering med huvudfokus på att skilja mellan olika typer av enheter. En metod baserad på förkonfigurerade autenticeringsuppgifter har utvecklats och den används för att precist kunna identifiera olika typer av nätverkselement. De valda metoderna har implementerats som en optionell modul till NCS som erbjuder enhetsidentifieringsfunktionalitet. Ytterligare ett fokus för detta examensarbete har varit att utveckla metoder för identifieraing av nätverkstopologin, och modeller för hur topologin ska representeras.  Vi har syftat till att identifiera både den logiska IP nätverkstopologin (L3) och den fysiska topologin av sammankopplade enheter (L2). Den viktigaste uppgiften har varit att identifiera och lagra topologi representation som en datastruktur, och dessutom generera en visualisering av nätverkstopologin.

Disruptions due to either natural or anthropogenic hazards significantly impact the operation of critical infrastructure networks because they may instigate network-level cascade (i.e., systemic) risks. Therefore, quantifying and enhancing the resilience of such complex dynamically evolving networks ensure minimizing the possibility and consequences of systemic risks. Focusing only on robustness, as one of the key resilience attributes, and on transportation networks, key critical infrastructure, the current study develops a hybrid complex network theoretic-genetic algorithms analysis approach. To demonstrate the developed approach, the robustness of a city transportation network is quantified by integrating complex network theoretic topology measures with a dynamic flow redistribution model. The network robustness is subsequently investigated under different operational measures and the corresponding absorptive capacity thresholds are quantified. Finally, the robustness of the network under different failure scenarios is evaluated using genetic algorithms coupled with k-means clustering to classify the different network components. The hybrid approach developed in the current study is expected to facilitate optimizing potential systemic risk mitigation strategies for critical infrastructure networks under disruptive events. / Thesis / Master of Applied Science (MASc)

ZigBee is a substandard of IEEE 802.15 family that is specially designed to take care of factors such as power, data rate and area that primarily affect network performance. This has controlling and monitoring capability, which finds potential applications in different sectors. ZigBee allows the concept of hybrid networks and mobility. A comprehensive analysis of ZigBee networks was carried out by constructing and simulating the networks to evaluate the performance in terms of throughput, delay, network load, and packets dropped. This research is aimed at evaluating the effect of network topology on the system performance. A careful review of simulation platforms brought the conclusion of using OPNET Modeler which has the required frame work. Different network topologies of simple and hybrid were built and simulated. Throughout the simulations, the best-case scenarios were drawn to the conclusion by the graphical analysis of parameters of evaluation. Mobile networks were constructed and simulated to investigate the effect of mobility on communication.

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