Wireless sensor networks (WSN) are event based systems that rely on the collective effort of densely deployed sensor nodes continuously observing a physical phenomenon. The spatio-temporal correlation between the sensor observations and the cross-layer design advantages are significant and unique to the design of WSN. Due to the high density in the network topology, sensor observations are highly correlated in the space domain. Furthermore, the nature of the energy-radiating physical phenomenon constitutes the temporal correlation between each consecutive observation of a sensor node. This unique characteristic of WSN can be exploited through a cross-layer design of communication functionalities to improve energy efficiency of the network. In this thesis, several key elements are investigated to capture and exploit the correlation in the WSN for the realization of advanced efficient communication protocols. A theoretical framework is developed to capture the spatial and temporal correlations in WSN and to enable the development of efficient communication protocols. Based on this framework, spatial Correlation-based Collaborative Medium Access Control (CC-MAC) protocol is described, which exploits the spatial correlation in the WSN in order to achieve efficient medium access. Furthermore, the cross-layer module (XLM), which melts common protocol layer functionalities into a cross-layer module for resource-constrained sensor nodes, is developed. The cross-layer analysis of error control in WSN is then presented to enable a comprehensive comparison of error control schemes for WSN. Finally, the cross-layer packet size optimization framework is described.

當發生大規模地震或強烈颱風等大型天然災害，其災後72小時為人命搜救之黃金期。由歷來的大型災變中，可知行動通訊系統其實極為脆弱且不可靠，而通訊系統癱瘓將影響救災工作之成效。本論文中探討的應急通訊系統利用倖存之連通基地台和斷訊卻沒有損毀的基地台，以無線電互相連接成一個轉送拓樸以建構臨時性通訊系統，稱為應急蜂巢式行動通訊網路(Contingency Cellular Network，CCN)。 在災難發生後，災區通常有許多須要較高通話需求的關鍵區域，其通話需求遠高於輕度災區，建置CCN時必須優先保障其通訊需求，我們先前之研究所提出的樹狀轉送拓樸其結構較脆弱，若任何一個link斷訊失去轉送功能，則其節點以下的使用者通訊將受到影響，導致任何一個節點對外通訊能力非常脆弱，影響CCN之可用度。為了提升CCN之可用度，我們提出了多路徑的CCN網路拓樸解決方案，在本方案中，每個關鍵區域都有數條對外通訊的連線。 本論文以各基地台通訊範圍內的通訊需求人數與災區毀損程度，作為效益參數，在有限緊急修復資源下，將問題塑模為一個類似K-Maximum Spanning Tree問題的Length Bounded Disjoint K-Path Max-Profit Mesh問題，我們證明它屬於NP-Hard問題，並且提出快速且效能不差之啟發式演算法，可在緊急時建立應急蜂巢式行動網路的多路徑網路拓樸。本文以電腦模擬方式，進行實驗以驗證我們的模型之適切性，並評估多路徑拓樸可提升之CCN可用度，實驗結果可提供使用者依不同的CCN可用度及總救災效益需求，選擇所需之多路徑數量。 / When stricken by a catastrophic natural disaster, the golden 72 hours is very critical to life saving. However, communication systems including cellular networks often crashed due to various causes making big impact to the efficiency of disaster response. Our research proposes the Contingency Cellular Network (CCN) by connecting disconnected base stations together using wireless links to form an overlay Ad Hoc network over a disconnected cellular network. 　　In our previous study, we proposed a tree topology to construct CCN, which is vulnerable since a single link failure may have a big impact to the availability of CCN. This thesis proposes a multi-path topology to enhance the availability of CCN such that the selected critical areas will have redundant communication paths connecting to the core network and thus, have higher resiliency against link failure. We model the CCN Multi-path Network Topology Design problem into a combinatorial problem, called Length Bounded Disjoint K-Path Max-Profit Mesh Problem. We take the degree of emergency and the population of each stricken area as the priority measure as well as the amount of emergency recovery resources as the capacity constraint in the topology computation model. The problem is proven to be NP Hard. Therefore, we designed an efficient heuristic algorithm (HLBDK) to solve the problem when it is needed in urgent. Finally, we evaluated the proposed algorithm by simulation. The simulation results show that the average performance deviation of the proposed heuristic algorithm away from the optimal solutions is smaller than 7% in all cases. A significant improvement in the availability can be obtained by using multi-path topology at a reasonable performance degradation. Our research results provide users a fundamental base to determine their availability requirement at a countable performance degradation.

This works proposes a novel methodology for Fault Section Estimation in Power Systems. This document describes a computational tool to assist operators of electrical system in decision-making, thus ensuring the reliability of the energy supply and the reduction of reestablishment time after of fault occurrence. The proposed methodology is based on the interpretation of alarms provided by the Supervisory and Data Acquisition System (SCADA) and the electrical characteristics of the system, as well as impedance of transmission lines and transformers, circuit breakers states and settings of distance protective relays. The methodology is deterministic and uses the interception between zones of distance protective relays as base for the section estimation and the circuit breaker states to associate physically isolated sections in the system after of fault occurrence, making use of a shortest path search algorithm. Possible fault scenarios were simulated on the IEEE-30 Bus System in order to validate the methodology. The results show that the approach can provide satisfactory solutions, even in cases of multiple faults or failure of protections devices. / Este trabalho propõe uma nova metodologia para a estimação da seção de falta em sistemas elétricos de potência. O presente documento descreve uma ferramenta computacional capaz de auxiliar os operadores do sistema elétrico na tomada de decisão, favorecendo a confiabilidade do fornecimento da energia e a redução do tempo de reestabelecimento quando da ocorrência de falta. A metodologia proposta esta baseada na interpretação dos alarmes fornecidos pelo Sistema de Supervisão e Aquisição de dados (SCADA) e nas características elétricas do sistema, assim como impedâncias de linhas de transmissão e transformadores; nos estados dos disjuntores e nos sinais e ajustes dos relés de proteção de distância. A metodologia é determinística e utiliza a intercepção entre as zonas de proteção dos relés de distância como base para a estimação da seção e os estados dos disjuntores para associar as seções fisicamente isoladas no sistema ante a ocorrência de falta, fazendo uso de um algoritmo de busca do caminho mais curto. Possíveis cenários de falta foram simulados no sistema IEEE-30 barras a fim de validar a metodologia. Os resultados mostram que a abordagem consegue fornecer soluções satisfatórias, mesmo em casos de faltas múltiplas ou em caso de falha de dispositivos de proteção.

Commercial provisioning of file synchronization services (FSS) relies entirely on protocols that utilize a remote central server that is often located in the cloud to host important files. Updates at user computers are propagated to the central server and from the central server to other sources in need of such updates. Therefore, a synchronization operation between two computers located on the same network often results in file data transmission to and from this local network at least twice. This introduces an unnecessary bandwidth usage on a user’s local network and has become an issue, especially since there is an increase in the demands for internet resources. This thesis work presents a new file synchronization protocol towards FSS known as LAPSync (location-aware protocol for remote file synchronization). This paper also proposes a hierarchical synchronization mechanism by utilizing LAPSync. Our proposed solution relies on the ability of LAPSync clients to acquire knowledge about the location of clients participating in the synchronization operation to construct a hierarchical synchronization path. Finally, we implement our protocol into a prototype and conduct experiments to compare with drop-box (a popular file synchronization service). The results obtained show that LAPSync offers a reduction in bandwidth usage when the files to be synchronized exist on the same local network

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Le paradigme de l'Internet des choses établit l'interaction et la communication avec une énorme quantité d'acteurs. Le concept combine un grand nombre de technologies et de protocoles et des adaptations des éléments préexistants pour offrir de nouveaux services et applications. Une des technologies clés de l'Internet des objets est l'identification par radiofréquence abrégée en anglais RFID («Radio Frequency Identification»). Elle propose un ensemble de solutions qui permettent le suivi et la traçabilité des personnes, des animaux et pratiquement n'importe quel objet en utilisant des liaisons sans fil. En considérant le concept de l'Internet des choses, plusieurs technologies doivent être liées afin de fournir des interactions qui conduisent à la mise en œuvre de services et d'applications. Le défi est que ces technologies ne sont pas nécessairement compatibles et conçues pour fonctionner ensemble. Dans ce contexte, l'objectif principal de cette thèse est de concevoir un « framework » hétérogène qui permettra l'interaction de divers dispositifs tels que la RFID, des capteurs et des actionneurs afin de fournir de nouvelles applications et de services. À cet effet, notre première contribution est la conception et l'analyse d'une architecture d'intégration pour les dispositifs hétérogènes. Dans la seconde contribution, nous proposons un modèle d'évaluation de la topologie RFID et un outil d'optimisation pour la planification de réseaux de cette technologie. Enfin, nous avons implémenté une version simplifiée du framework en utilisant du matériel embarqué et indicateurs de performance sont fournis ainsi que la configuration détaillée de la plateforme de test / The Internet of Things paradigm establishes interaction and communication with a huge amount of actors. The concept is not a new-from-scratch one; actually, it combines a vast number of technologies and protocols and surely adaptations of pre-existing elements to offer new services and applications. One of the key technologies of the Internet of Things is the Radio Frequency Identification just abbreviated RFID. This technology proposes a set of solutions that allow tracking and tracing persons, animals and practically any item wirelessly. Considering the Internet of Things concept, multiple technologies need to be linked in order to provide interactions that lead to the implementation of services and applications. The challenge is that these technologies are not necessarily compatible and designed to work with other technologies. Within this context, the main objective of this thesis is to design a heterogeneous framework that will permit the interaction of diverse devices such as RFID, sensors and actuators in order to provide new applications and services. For this purpose in this work, our first contribution is the design and analysis of an integration architecture for heterogeneous devices. In the second contribution, we propose an evaluation model for RFID topologies and an optimization tool that assists in the RFID network planning process. Finally, in our last contribution, we implemented a simplified version of the framework by using embedded hardware and performance metrics are provided as well as the detailed configuration of the test platform

[pt] Os incêndios florestais podem ser uma fonte de vulnerabilidade para sistemas de potência. Esses eventos podem afetar especialmente a operação de sistemas de distribuição, interrompendo o fornecimento de energia, aumentando os custos, e diminuindo a confiabilidade. Nesta dissertação, é considerada a relação entre as decisões operativas e a probabilidade de falha nas linhas sob o contexto de queimadas. Este tipo de estudo ainda não foi devidamente avaliado pelo meio acadêmico. Ao não reconhecer este aspecto, o funcionamento dos sistemas de potência pode estar sendo prejudicado. A modelagem adequada dessa dependência poderia reduzir a incidência de queimadas e perda de carga. Considerando este aspecto, um problema de otimização distributivamente robusto de dois estágios com incerteza endógena foi desenvolvido para considerar a operação multiperíodo de sistemas de distribuição. O primeiro estágio determina a topologia da rede e os investimentos nas linhas, e o segundo estágio avalia o custo operacional esperado no pior caso. Nessa estrutura, a incerteza é modelada de forma dependente das decisões do modelo, onde as probabilidades de falha da linha são em função do fluxo de potência das próprias linhas. Um método iterativo é proposto para resolver este modelo e uma análise fora da amostra é desenvolvida para validação através de diferentes estudos. Os resultados mostraram que, ao negligenciar a dependência da incerteza, uma maior perda de carga e um maior custo operacional são esperados. Ao considerar esta nova abordagem, a confiabilidade da rede pode ser melhorada e as consequências dos incêndios podem ser mitigadas com ações mais econômicas. / [en] Wildfires can be a source of vulnerability for power systems operations. These events can especially affect the operation of distribution systems. They can interrupt energy supply, increase costs, and decrease grid resilience. Numerous approaches can be executed to prevent them. In this dissertation, it is considered the relationship between operative actions and the probability of wildfire disruption. This type of study has not been properly evaluated in technical and scientific literature. By not recognizing this aspect, the operation of power systems may be impaired. Properly modeling this dependency could lower wildfire disruption and loss of load. Considering this, a two-stage distributionally robust optimization problem with decision-dependent uncertainty is developed to consider distribution system multiperiod operation. The first stage determines the optimal switching actions and line investments, and the second stage evaluates the worst-case expected operation cost. It is designed a decision-dependent uncertainty framework where the line failure probabilities are a function (dependent) of its power flow levels. An iterative method is proposed to solve this model and an out-of-sample analysis is developed to validate it through different case studies. Results showed that, by neglecting the uncertainty dependency on operative decisions, there could be a higher expected loss of load and a higher operational cost. By considering this new approach when operating power lines, the grid s resilience could be improved and wildfire consequences can be mitigated with less costly actions.

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