Η διπλωματική εργασία συνίσταται στην ανάπτυξη ασύρματου δικτύου αισθητήρων και Προγραμματιζόμενων Λογικών Ελεγκτών (PLCs) στο χώρο του Εργαστηρίου Γενικής Ηλεκτροτεχνίας για την παρακολούθηση σε πραγματικό χρόνο ορισμένων φυσικών μεγεθών. Η διάταξη χωρίζεται σε δύο τμήματα. Το πρώτο αφορά το ασύρματο δίκτυο αισθητήρων (WSN) και περιλαμβάνει τους αισθητήρες, τους πομπούς αποστολής δεδομένων από τους αισθητήρες και το δέκτη λήψης δεδομένων από όλους τους πομπούς. Το δεύτερο αφορά το ασύρματο δίκτυο των PLCs και περιλαμβάνει τα PLCs, τους επικοινωνιακούς επεξεργαστές και τις μονάδες ασύρματης επικοινωνίας, για την επιτυχή ανταλλαγή δεδομένων μεταξύ τους. Επίσης, χρησιμοποιείται το λογισμικό WinCC – Flexible για τη δημιουργία εποπτικού σταθμού παρακολούθησης των τιμών των μεγεθών (σύστημα SCADA). Βασικός σκοπός της εργασίας είναι η ενοποίηση των δύο δικτύων ώστε να είναι δυνατή η μεταφορά δεδομένων μεταξύ των διάφορων συσκευών, σύμφωνα με τις απαιτήσεις μια πιθανής απλής βιομηχανικής διεργασίας. Οι αισθητήρες είναι διασκορπισμένοι στο χώρο του εργαστηρίου και παίρνουν μετρήσεις για ένα φυσικό μέγεθος ο καθένας. Τα μεγέθη προς μέτρηση είναι: εξωτερική θερμοκρασία, εσωτερική θερμοκρασία, υγρασία, πίεση δικτύου πεπιεσμένου αέρα, ύψος, ρεύμα και βάρος. Κάθε αισθητήρας είναι ηλεκτρικά συνδεδεμένος με ένα πομπό, ο οποίος αναλαμβάνει τη μετάδοση των μετρήσεών του σε ένα δέκτη. Ο πομπός μεταδίδει δεδομένα μέσω της μονάδας επικοινωνίας XBEE, η οποία εσωκλείεται μαζί με το ολοκληρωμένο κύκλωμα λειτουργίας της σε περίβλημα κατάλληλο για την προστασία της σε απαιτητικές βιομηχανικές συνθήκες. Κάθε ζευγάρι αισθητήρα και πομπού μετάδοσης συνιστά ένα περιφερειακό κόμβο του WSN. Όλα τα δεδομένα λαμβάνονται από τον κεντρικό κόμβο – δέκτη του WSN. Από τον κεντρικό κόμβο είναι δυνατή η απεικόνιση των μετρήσεων σε κατάλληλο περιβάλλον του λογισμικού TC-Central, που συνοδεύει τις συσκευές του WSN, καθώς και η ανατροφοδότηση τους στο ασύρματο δίκτυο των PLCs. Το λογισμικό TC-Central χρησιμοποιείται επιπλέον για τη ρύθμιση βασικών παραμέτρων του WSN, όπως είναι η διεύθυνση των πομπών στο δίκτυο και ο ρυθμός μετάδοσης δεδομένων. Για την ανατροφοδότηση των μετρήσεων στο δίκτυο των PLCs χρησιμοποιούνται οι 4 αναλογικές έξοδοι του κεντρικού κόμβου του WSN. Τα 3 PLCs της διάταξης διασυνδέονται τόσο ενσύρματα, μέσω δικτύου PROFIBUS-DP, όσο και ασύρματα μέσω τοπολογίας Σημείο-προς-Σημείο. Στην παρούσα εφαρμογή χρησιμοποιείται μόνο η ασύρματη σύνδεση μεταξύ των PLCs, όπου αυτά ακολουθούν μέθοδο πρόσβασης στο δίκτυο κυρίου – εξαρτημένου, με έναν κύριο και δύο εξαρτημένους σταθμούς. Κάθε PLC περιλαμβάνει επικοινωνιακό επεξεργαστή CP 342-5 για την ενσύρματη σύνδεση, καθώς και επικοινωνιακό επεξεργαστή CP 340 και μονάδα ασύρματης επικοινωνίας ARM-IOS RS232/485 για την ασύρματη σύνδεση. Ο επικοινωνιακός επεξεργαστής αποτελεί το συνδετικό κρίκο μεταξύ της μνήμης του PLC και της μονάδας επικοινωνίας. Σε περίπτωση μετάδοσης δεδομένων, αυτά μεταφέρονται από τη μνήμη στον επεξεργαστή και στη συνέχεια στη μονάδα επικοινωνίας, ενώ σε περίπτωση λήψης ακολουθείται η αντίστροφη πορεία. Από τις αναλογικές εξόδους του δέκτη, τα μεγέθη μεταφέρονται μέσω καλωδιακής σύνδεσης, στην κάρτα αναλογικών εισόδων ενός εκ των εξαρτημένων PLC. Από εκεί μεταδίδονται στον άλλο εξαρτημένο, μέσω του κύριου σταθμού, ο οποίος συνδέεται με το σύστημα SCADA. Στο χώρο του εργαστηρίου έχει αναρτηθεί οθόνη, για την απεικόνιση των τιμών των μεγεθών σε όσους βρίσκονται εντός. / The thesis consists in developing a wireless sensors and programmable logical controllers (PLCs) network in Systems and Measurements Laboratory in order to monitor on-line some physical values. The experimental set-up is divided in two parts. The first part is related to the wireless sensors network (WSN) and consists of the sensors, the transceivers and the receiver, which collects data among all sensor nodes. The second part is related to the PLCs' wireless network and consists of the PLCs, the communication processors and the wireless networking modules. In addition, software WinCC-Flexible is used in order to implement a monitoring station of measured values (SCADA system). The thesis' basic goal is to unify the networks, so that data transfer among used devices is achieved, according to the standards of a possible industrial application. Sensors are dispersed in the laboratory and measure a physical value per each. The measured values are: outdoor and indoor temperature, relative humidity, pneumatics' network pressure, height, current and weight. Each sensor is electrically connected to a transceiver, which transmits measured data to the receiver. The transceiver transmits data through the radio frequency module XBEE, which is enclosed into a special cover, suitable for protection in demanding industrial conditions. Each sensor-transceiver pair constitutes a WSN's sensor node. All data is received by the WSN's central node-receiver. On-line monitoring of all measured values is possible through the receiver, by use of TC-Central software, which is also used in order to set WSN's parameters, such as sensor nodes' addresses and data sample rate. Moreover, the receiver contains four analog outputs, which can be used to redirect four received signal in external devices. These analog outputs unify the two wireless networks, by retransmitting four selected measured values to the PLCs' network. The PLCs' network consists of 3 PLCs, networked both wired (PROFIBUS-DP) and wireless (Point-to-Point topology). In the current application only the wireless connection between the PLCs is used, following master / slave media access method, including 1 master station and 2 slave stations. Each PLC includes a communication processor CP 342-5 for wired connection, as well as a communication processor CP 340 and a RF module ARM-IOS RS232/485 for wireless connection. The communication processor connects the PLC's memory and RF module. A PLCs' network slave station is connected to the SCADA system. In the laboratory, a screen has been posted, so that measured values can be visible by everyone inside.

The emerging technology of Cyberphysical systems consists of networked computing, sensing, and actuator devices used to monitor, connect, and control physical phenomena. In order to economically and sustainably operate Cyberphysical systems, their devices need to cooperate over a communication network to solve optimization problems. For example, in smart power grids, smart meters cooperatively optimize the grid performance, and in wireless sensor networks a number of sensors cooperate to find optimal estimators of real-world parameters. A challenging aspect in the design of distributed solution algorithms to these optimization problems is that while the technology advances and the networks grow larger, the communication bandwidth available to coordinate the solution remains limited. Motivated by this challenge, this thesis investigates the convergence of distributed solution methods for resource allocation optimization problems, where gradient information is communicated at every iteration, using limited communication. This problem is approached from three different perspectives, each presented in a separate paper.  The investigation of the three papers demonstrate promises and limits of solving distributed resource allocation problems using limited communication bandwidth. Future work will consider how even more general problems can be solved using limited communication bandwidth and also study different communication constraints. / <p>QC 20170424</p>

Un nœud d'un réseau de capteurs sans fil traite dans ses unités de calcul les signaux issus de plusieurs types de capteurs et effectue différentes tâches liées aux protocoles de communication. Devant exécuter plusieurs types de contrôle, sa flexibilité est un paramètre très important. Les solutions à base de microcontrôleurs ou de FPGA ont été proposées pour aborder le besoin de flexibilité, mais au prix d'une efficacité énergétique réduite. Dans cette thèse, des contrôleurs flexibles à ultra-faible énergie basés sur un contexte de micro-tâches reconfigurables sont explorés comme alternative. Des architectures modulaires pour des machines d'états finis (FSM) et des chemins de données (DP) reconfigurables sont proposées. Les techniques de coupure de l'alimentation (PG pour power gating) sont utilisées pour adapter la consommation aux besoins et réduire la puissance statique. Dans un premier temps, des modèles pour l'estimation des paramètres clés d'un circuit avec PG sont proposés au niveau porte. Ensuite, les opportunités des techniques PG sont déterminées sur les FSM et DP reconfigurables pour en réduire l'énergie. Dans les chemins de données, la reconfiguration fait varier la précision des opérateurs et le PG permet d'éteindre les blocs logiques inutilisés. Une gestion de l'alimentation au niveau lookup table (LUT) est proposée pour réduire les courants de fuite en mode actif et en veille dans les FSM reconfigurables. Des résultats montrent les très bonnes performances des architectures proposées par rapport aux processeurs et FPGA. / A wireless sensor network (WSN) node may need to process signals from various sensors and perform different transceiver tasks apart from being able to change its functions dynamically. A controller in the node is therefore required to execute different control tasks to manage its resources implying that flexibility is a key concern. Microcontrollers and FPGAs have been proposed to address the need for flexibility at the cost of reduced energy efficiency. In this thesis, ultra-low power flexible controllers for WSN nodes based on reconfigurable microtasks are explored. A reconfigurable microtask is a digital control unit with a reconfigurable finite state machine (FSM) and datapath. Scalable architectures for reconfigurable FSMs along with variable precision adders in datapath are proposed for flexible controllers in this work. Power gating is considered for FSMs and adders for low power operation. First, the design issues in power gating are studied extensively. Models for estimation of key design parameters of power-gated circuits are derived at gate level. Next, power gating opportunities are determined in reconfigurable adders and FSMs proposed for microtasks. In adders, reconfigurability is used for varying the precision of operation and saving energy by power-gating unused logic. Power gating at the level of lookup table logic is proposed to achieve active leakage power reduction in reconfigurable FSMs. The proposed models are then applied to analyze energy savings in logic clusters due to power gating. Power estimation results show good performance of proposed architectures with respect to different metrics relative to others in the design space of controllers.

L’émergence des systèmes embarqués a permis le développement des réseaux de capteurs sans fil dans de nombreux domaines différents. Cependant, la sécurité reste un problème ouvert. La vulnérabilité des nœuds est principalement liée au manque de ressources. En effet, l’unité de traitement ne dispose pas d’assez de puissance et de mémoire pour gérer des mécanismes de sécurité très complexes.La cryptographie est une solution qui est largement utilisée pour sécuriser les réseaux. Par rapport à la cryptographie symétrique, la cryptographie asymétrique nécessite des calculs plus compliqués,mais elle offre une distribution de clés plus sophistiquée et la signature numérique. Dans cette thèse, nous essayons d’optimiser la performance d’ECC (Elliptic Curve Cryptography), un cryptosystème asymétrique qui est connu pour sa robustesse et son utilisation de clé plus courte par rapport à RSA. Nous proposons d’utiliser le parallélisme pour accélérer le calcul de la multiplication scalaire, qui est reconnue comme l’opération la plus coûteuse sur les courbes elliptiques. Les résultats de tests ont montré que notre solution offre un gain intéressant malgré une augmentation de la consommation d’énergie.La deuxième partie de la contribution concerne l’application de la tolérance aux pannes dans notre architecture de parallélisation. Nous utilisons les nœuds redondants pour la détection des pannes et la restauration du calcul. Ainsi, en utilisant l’ECC et la tolérance aux pannes, nous proposons une solution de sécurité efficace et sûre pour les systèmes embarqués. / The emergence of embedded systems has enabled the development of wireless sensor networks indifferent domains. However, the security remains an open problem. The vulnerability of sensor nodesis mainly due to the lack of resources. In fact, the processing unit doesn’t have enough power ormemory to handle complex security mechanisms.Cryptography is a widely used solution to secure networks. Compared with symmetric cryptography,the asymmetric cryptography requires more complicated computations, but it offers moresophisticated key distribution schemes and digital signature.In this thesis, we try to optimize the performance of ECC. An asymmetric cryptosystem which isknown for its robustness and the use of shorter keys than RSA. We propose to use parallelismtechniques to accelerate the computation of scalar multiplications, which is recognized as the mostcomputationally expensive operation on elliptic curves. The test results have shown that our solutionprovides a significant gain despite an increase in energy consumption.The 2nd part of our contribution is the application of fault tolerance in our parallelism architecture.We use redundant nodes for fault detection and computation recovery. Thus, by using ECC and faulttolerance, we propose an efficient and reliable security solution for embedded systems.

Le développement dans les micros systèmes électromécaniques (MEMS) combiné avec l'émergence des nouvelles technologies de l'information et de la communication a permis l'intégration des fonctionnalités de collecte, de traitement et de transmission des données dans un seul dispositif minuscule qui est le capteur sans fil. En voie de conséquence, les réseaux composés de ces capteurs offrent aujourd'hui une pléiade d'avantages par rapport aux réseaux traditionnels notamment en termes de simplicité et de coût de déploiement. Ceci a conduit au développement d'une gamme très variée d'applications des réseaux de capteurs sans fil dans les domaines de la santé, de l'environnement, de l'industrie, des infrastructures, des activités spatiales, ou encore des activités militaires et dans plusieurs autres domaines. Cependant, de nouveaux défis surgissent des caractéristiques particulières de ces réseaux. En réalité, de nombreuses applications de ces réseaux sont critiques et exigent qu'un fonctionnement correct du réseau soit maintenu le plus longtemps possible. Par contre, les environnements dans lesquels ces réseaux sont déployés rendent la mission de maintien en condition correcte de ces réseaux très compliquée et même parfois impossible ; d'où la nécessité d'intégrer des mécanismes d'auto-correction qui visent à surmonter les problèmes qui puissent surgir dans le réseau sans intervention humaine. Dans ce contexte, nous avons, dans cette thèse, concentré notre étude sur les techniques et les mécanismes mis en œuvre pour améliorer la propriété de tolérance aux pannes dans les réseaux de capteurs sans fil. Tout d'abord, nous avons proposé des approches centralisées et distribuées pour l'auto-rétablissement de la connectivité et la réallocation des canaux dans un contexte de réseaux de capteurs sans fil reposant sur des communications multi-canal après la panne d'un nœud critique. Après la formulation du problème sous la forme d'un problème d'optimisation multi-objectif, nous avons proposé des algorithmes basés sur des heuristiques de coloration de graphes et d'arbre de Steiner, très connus dans la théorie de graphes pour la résolution de ce type de problèmes. Dans une deuxième partie de cette thèse, nous avons étudié un cas d'application particulier, l'agriculture de précision, et avons proposé une solution distribuée pour le rétablissement du fonctionnement du réseau de capteurs sans fil / The development in Micro Electro-Mechanic Systems (MEMS) combined with the emergence of new information and communication technologies allowed the integration of the data sensing, processing and transmission in a single tiny device which is the wireless sensor. Consequently, the networks formed by these sensors offer a lot advantages compared with the traditional networks, in particular in terms of the deployment simplicity and cost. This led to the development of a wide range of Wireless Sensor Networks' applications in the domains of health, environment, industry, infrastructures, spatial activities, or even military activities and in many other domains. However, new challenges appear from the particular characteristics of these networks. In fact, many applications of this type of networks are critical and require that the correct functioning of the network is maintained as long as possible. However, the environments in which these networks are deployed return the mission of network maintenance very complicated or even impossible; hence, the necessity of integrating mechanisms of self-correction which aim to overcome the appeared problems without a human intervention. In this context, we focused our study on the techniques and mechanisms implemented to improve the property of fault tolerance in the wireless sensor networks. First, we proposed centralized and distributed approaches for the connectivity restoration and the channel reallocation in a multi-channel communication context after the failure of a critical node. After the formulation of the problem as a multi-objective optimization problem, we proposed some algorithms based on the heuristics of graphs coloring and Steiner tree, very known in the graph theory to solve this type of problems. In a second part in this thesis, we studied a particular application case, precision agriculture, and we proposed a distributed solution for the failure recovery in wireless sensor networks

O trabalho desenvolvido nessa dissertação é a concepção de uma camada de segurança nomeada de CoEP (Constrained Extensible Protocol), nome similar à camada de aplicação CoAP (Constrained Aplication Protocol), por razões de sua compatibilidade em utilização, como apresentado em detalhes no texto. Essa camada, por sua vez, é criada por conta da identificação de lacuna de prover tecnologia de segurança adequada e compacta em dispositivos restritos; isto é, dispositivos com baixa capacidade de processamento, comunicação e armazenamento, mas alto volume de dipositivos em rede que, como justificado posteriormente, chamamos de dispositivo de grão fino. Além disso, esses volumes, que são de dezenas a centenas de dispositivos, se dão em sistemas conhecidos como redes de sensores sem fio, onde processamento paralelo e distribuído ocorre de forma autônoma e de forma a criar-se uma rede de comunicação. Enquanto diversas tecnologias habilitadoras permitiram que redes de sensores sem fio se tornassem cada vez mais possíveis tecnicamente e economicamente - devido ao avanço da tecnologia em áreas como baterias, supercapacitores, circuitos de consumo ultra-baixo, sensores mais econômicos e com novas técnicas de medição, e outras -, o mesmo tem sido feito em questões de software e implementação de protocolos e padrões para que se utilize todo esse avanço de hardware de forma inteligente e eficiente. Isto foi feito através de reestruturação e adaptação de protocolos para esses dispositivos, porém percebe-se que foram feitas poucas contribuições para implementar-se segurança de forma eficiente; como identificado na dissertação, esses dispositivos têm utilizado versões parcialmente implementadas do protocolo DTLS, um protocolo extenso e que foi desenvolvido para dispositivos de recursos abundantes, isto é, que possuem recursos de sobra para a tecnologia. O CoEP é, nesse contexto, uma camada de segurança que substituiria o DTLS em dispositivos de grão fino para realizar tarefas de segurança para protocolos de aplicação de forma inteligente e eficiente. Além do CoEP realizar sua tarefa de segurança, a camada também foi arquitetada para utilizar recursos de forma eficiente e prover segurança como um serviço para protocolos, retirando necessidades de implementação de segurança individualmente em cada protocolo e demais trabalhos de desenvolvimento. Como resultado, a camada foi implementada em sistema restrito e pode reduzir consideravelmente a utilização de seus recursos, bem como sua utilização obriga todos dispositivos conectados nessa mesma rede a utilizem segurança, o que é essencial para redes de sensores sem fio, que tem o potencial de ter o mesmo impacto na sociedade que a própria Internet teve, como detalhado no texto. / The developed work in this dissertation is the design of a security layer named Constrained Extensible Protocol (CoEP), similar name to the Constrained Application Protocol (CoAP) application layer, for reasons of its compatibility in use, as presented in detail in the text. This layer, on the other hand, is created because of the identification of the gap to provide adequate and lean security technology in restricted devices; that is, with low processing, communication and storage capacity, but with high volume which, as justified later, we call fine grain device. In addition, these device volumes are reachable in systems known as wireless sensor networks, where parallel and distributed processing occurs autonomously and in a way to create a communication network. While several enabling technologies have made wireless sensor networks to become increasingly possible technically and economically - due to the advancement of technology, areas such as batteries, supercapacitors, ultra-low consumption circuits, more economical sensors and new measurement techniques, and more -, the same has been done in software, protocols and standards implementation so that all this advance of hardware can be used intelligently and efficiently. This was done through the restructuring and adaptation of protocols for these devices, but it is noticed that few contributions were made to implement security efficiently; as identified in the dissertation, these devices have used partially implemented versions of the DTLS protocol, an extensive protocol that was developed for relatively unlimited resource devices. CoEP is, in this context, a security layer that would replace DTLS in fine grain devices to perform security tasks for application protocols in an intelligent and efficient manner. In addition to CoEP performing its security task, the layer was also architected to efficiently utilize resources and provide security as a service for protocols, removing individual security implementation needs in each protocol and other development work. As a result, the layer has been deployed on a lean system and can greatly reduce the utilization of its resources, as well as its use obliges all connected devices to use security, which is essential for wireless sensor networks, which has the potential to have the same impact on society that the Internet itself had, as detailed in the text.

Wireless sensor networks (WSN) play an important role in today’s monitoring and controlsystems like environmental monitoring, military surveillance, industrial sensing and control, smarthome systems and tracking systems. As the application of WSN grows by leaps and bounds, there is anincreasing demand in placing a larger number of sensors and controllers to meet the requirements. Theincreased number of sensors necessitates flexibility in the functioning of nodes. Nodes in wirelesssensor networks should be capable of being dynamically reconfigured to perform various tasks is theneed of the hour.In order to achieve flexibility in node functionality, it is common to adopt reconfigurablearchitecture for WSN nodes. FPGA-based architectures are popular reconfigurable architectures bywhich WSN nodes can be programmed to take up different roles across time. Area and power are themajor overheads in FPGA based architectures, where interconnect consumes more power and area thanlogic cells. The contemporary WSN standard requires longer battery life and micro size nodes for easyplacement and maintenance-free operation for years together.Three solutions have been studied and evaluated to approach this problem: 1) Homogenousembedded FPGA platform, 2) Power gated reconfigurable finite state machines and 3) Pass transistorlogic (PTL) based reconfigurable finite state machines. Embedded FPGA is a CMOS 65nm customdeveloped small homogenous FPGA which holds the functionality of the WSN nodes and it will bedynamically reconfigured from time to time to change the functionality of the node. In Power gatedreconfigurable FSM architecture, the functionality of the node is expressed in the form of finite statemachines, which will be implemented in a LUT based power gated design. In PTL based reconfigurablefinite state machine architecture, the finite state machines are completely realized using PTL basedcustom designed sets of library components. Low power configuration memory is used to dynamicallyreconfigure the design with various FSMs at different times.

Multi-hop broadcast is one of the main approaches to disseminate data in VANET. Therefore, it is important to design a reliable multi-hop broadcast protocol, which satis es both reachability and bandwidth consumption requirements. In a dense network, where vehicles are very close to each other, the number of vehicles needed to rebroadcast the message should be small enough to avoid a broad- cast storm, but large enough to meet the reachability requirement. If the network is sparse, a higher number of vehicles is needed to retransmit to provide a higher reachability level. So, it is obvious that there is a tradeo between reachability and bandwidth consumption. In this work, considering the above mentioned challenges, we design a number of smart broadcast protocols and evaluate their performance in various network den- sity scenarios. We use fuzzy logic technique to determine the quali cation of vehicles to be forwarders, resulting in reachability enhancement. Then we design a band- width e cient fuzzy logic-assisted broadcast protocol which aggressively suppresses the number of retransmissions. We also propose an intelligent hybrid protocol adapts to local network density. In order to avoid packet collisions and enhance reachability, we design a cross layer statistical broadcast protocol, in which the contention window size is adjusted based on the local density information. We look into the multi-hop broadcast problem with an environment based on game theory. In this scenario, vehicles are players and their strategy is either to volunteer and rebroadcast the received message or defect and wait for others to rebroadcast. We introduce a volunteer dilemma game inspired broadcast scheme to estimate the probability of forwarding for the set of potential forwarding vehicles. In this scheme we also introduce a fuzzy logic-based contention window size adjustment system. Finally, based on the estimated spatial distribution of vehicles, we design a transmission range adaptive scheme with a fuzzy logic-assisted contention window size system, in which a bloom lter method is used to mitigate overhead. Extensive experimental work is obtained using simulation tools to evaluate the performance of the proposed schemes. The results con rm the relative advantages of the proposed protocols for di erent density scenarios. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

Diversas aplicações de redes de sensores sem fio necessitam de serviços de segurança, como confidencialidade, integridade e autenticação de origem de dados. Contudo, dadas as limitações de processamento, memória e suprimento de energia dos dispositivos, os mecanismos de segurança tradicionais podem causar efeitos indesejáveis na rede, como atraso na comunicação e aumento no consumo de energia, impondo obstáculos para seu uso na tecnologia em questão. Muitas propostas de esquemas de segurança baseados em criptografia simétrica projetados especificamente para redes de sensores sem fio são encontradas na literatura. Contudo, essas soluções são focadas na segurança salto-a-salto. Tal abordagem é adequada para garantir a segurança dos enlaces deste tipo de rede, mas não garante a segurança na comunicação fim-a-fim. Neste trabalho são apresentados cenários e desafios de implementação de segurança neste tipo de rede, e a concepção, o projeto e a implementação de uma arquitetura de segurança para redes de sensores sem fio, que tem como objetivos: prover segurança na comunicação fim-a-fim; permitir a interoperabilidade entre diferentes sistemas; e possibilitar uma maior flexibilidade em relação à utilização de chaves criptográficas em diferentes cenários e topologias. Adicionalmente, a solução proposta suporta ativação e desativação de seus serviços em tempo de execução. O projeto da referida arquitetura, atuante na camada de aplicação da pilha de protocolos de rede, foi construído com base na análise das características de arquiteturas encontradas na literatura, bem como de estratégias adotadas por estas. Para a construção da implementação foram selecionados mecanismos e algoritmos criptográficos a partir da avaliação de desempenho que considerou assimétricas de uso de memória, tempo de execução e consumo de energia. Como resultados são apresentados a especificação da arquitetura, a avaliação qualitativa da mesma e a avaliação de desempenho da implementação desenvolvida como prova de conceito. Além disso, é apresentada uma análise do impacto de diferentes topologias e características de disposição na tarefa de distribuição de chaves criptográficas em redes de sensores sem fio. / Many wireless sensor networks applications need security services, such as confidentiality, data integrity and data source authentication. On the other hand, because of device limitations, security mechanisms may affect the network energy consumption and communication delay, which impose a great challenge for practical implementation of security mechanisms in such scenario. Many solutions based on symmetric cryptography were proposed for the specific challenges of wireless sensor networks. Nevertheless, they are focused on hop-by-hop security. Such approach is suited to provide link-layer security, but it cannot guarantee end-to-end security. This work presents scenarios and challenges to implement security in wireless sensor networks, and the conception, design and implementation of a security architecture, which aims to provide: security in end-to-end communication; interoperability between different systems, and enable greater flexibility in cryptographic keys distribution in different scenarios and topologies. Additionally, the proposed solution supports on-the-y adjustment of its security services. The architecture design, which targets the application layer of the network protocol stack, was based on the main properties of the architectures found in literature as well as adopted strategies. For the implementation, mechanisms and cryptographic algorithms were selected through the performance evaluation that considers memory usage, execution time and power consumption as metrics. The results were the architecture specification and its qualitative analysis, and the performance evaluation of the implementation developed as proof of concept. Furthermore, we present an analysis of topology and deployment impact on key distribution task.

A aplicação eficiente de agrotóxicos é um desafio na produção agrícola, mesmo considerando os avanços com a agricultura de precisão. O efeito deriva é o principal responsável pela ineficiência no controle das pragas ou doenças, pelo desperdício de recursos e pela contaminação ambiental. Para minimizar a deriva é essencial conhecer as condições ambientais como vento, temperatura e umidade. Esta pesquisa propõe o uso das redes de sensores sem fio como sistema de monitoramento ambiental e de suporte ao processo de pulverização agrícola, especialmente a pulverização executada por aeronave. São propostas três funcionalidades para o sistema: avaliação das condições ambientais, verificando se as condições estão apropriadas para a pulverização, buscando minimizar a ocorrência da deriva; suporte na definição e manutenção da rota do veículo pulverizador por meio dos dados do vento, de modo a efetuar ajustes na rota de pulverização e manter a aplicação do defensivo agrícola na área alvo; e a avaliação da eficácia da pulverização por meio dos dados da deposição do produto pulverizado coletados pela rede de sensores. Para viabilizar a utilização das redes de sensores sem fio no controle da deriva é proposto um protocolo de roteamento de dados que visa garantir a coleta dos dados pelos nós e a entrega para o veículo pulverizador, mesmo sendo ele um avião e se deslocando em alta velocidade. Para demonstrar a viabilidade do sistema proposto, foi desenvolvido um sistema de simulação computacional que considera os aspectos das redes de sensores sem fio e as características do protocolo de roteamento proposto. Os resultados demonstraram sua viabilidade, demonstrando que as redes de sensores sem fio podem ser utilizadas como suporte em um sistema de controle da deriva, incrementando a qualidade da pulverização, reduzindo custos e a contaminação ambiental. / The efficient application of low cost pesticides is a challenge for agricultural production. Pesticide drift is the major cause of money loss, inefficiency in crop disease control, and environmental contamination in the crop spraying process. At the time of application, it is essential to know the environmental conditions, such as wind, temperature and humidity to minimize contamination by pesticide drift. This study proposes the use of wireless sensor networks in a support and control system for crop spraying, especially in aircraft application methods. Three system functionalities are proposed: In the first case, the sensor network evaluates environmental data at the time of application to notify the user if the environmental conditions are suitable for continuing with the application. The second case evaluates the wind speed and its direction to suggest corrections in the path of a spray vehicle. Due to this alteration in the vehicle path, the pesticide will be applied only in the appropriate area. The final case involves collecting data samples and analyzing the quality of the spraying operation by evaluating the deposition of pesticide over the crop. This work proposes a new routing data protocol to make possible the use of wireless sensor networks in aerial crop spraying. It ensures that the sensor node data will be delivered to the sink node. Through computer simulations, wireless sensor networks are shown to be useful in crop spraying to minimize and to control pesticide drift, to improve the quality of application, to reduce environmental contamination and to reduce costs and the duration of the application operation.