Approved for public release; distribution in unlimited. / a beam towards the UAV. A simulation model was developed and implemented in MATLAB programming language to study the effectiveness of beamforming using sensor clusters for establishing a communication link to the UAV. Results showed that the antenna main lobe remained relatively unchanged in the presence of position errors and sensor node failures or when the density of the sensor nodes changed. Additionally, the maximum average power gain of the main lobe can be increased by increasing the density of the sensor cluster, thereby increasing the transmission range between the sensor clusters and the UAV. / Civilian, Singapore Ministry of Defense

Wireless sensor networks (WSNs) represent a class of miniaturized information systems designed to monitor physical environments. These smart monitoring systems form collaborative networks utilizing autonomous sensing, data-collection, and processing to provide real-time analytics of observed environments. As a fundamental research area in pervasive computing and envisioned as large-scale autonomous networks of communicating nodes capable of monitoring conditional metrics over vast geographic areas, WSNs have the potential to provide researchers and conservationists with increased knowledge of the intricacies and interrelationships of disparate environments. The author addressed the problem of developing a methodology for the design and deployment of WSNs in uncontrolled and harsh outdoor environments. Within the context of a research and conservation field study of flora, the author developed a model for deployment of WSNs within the domain of microclimate habitat monitoring. The goal of this study was to contribute to the body of knowledge in WSN research by developing a model for deployment that was scientifically sound and replicable. To accomplish this goal, the author conducted an investigation of current technologies associated with WSNs, their capabilities, and their applications specific to the stated domain. To validate this model, the author deployed a WSN for monitoring the microclimate habitats of a population of Spiranthes lacera var. gracilis, common name, slender ladies' tresses. During this field study, the WSN performed according to design and produced sufficient data to provide an accurate representation of the microclimate habitats of the objects of study. As a contribution to the WSN research body of knowledge, the author used an SDLC methodology to provide a pragmatic approach to deployment focused on the elements of nuance specific to WSNs for microclimate habitat monitoring.

Ten years after the Internet revolution are we standing on the brink of another revolution: networked embedded systems that connect the physical world with the computers, enabling new applications ranging from environmental monitoring and wildlife tracking to improvements in health care and medicine. 98% of all microprocessors sold today are used in embedded systems. Those systems have much smaller amounts of memory than PC computers. An embedded system may have as little has a few hundred bytes of memory, which makes programming them a challenge. This thesis focus on three topics regarding programming memory-constrained networked embedded systems: the TCP/IP for memory-constrained networked embedded systems, simplifying event-driven programming of memory-constrained systems, and dynamic loading of program modules in my Contiki operating system for memory-constrained systems. I show that the TCP/IP protocol stack can, contrary to previous belief, be used in memory-constrained embedded systems by implementing two small TCP/IP protocol stacks, lwIP and uIP. I present a novel programming mechanism called protothreads that I show significantly reduce the complexity of event-driven programming for memory-constrained systems. Protothreads provide a conditional blocked wait mechanism on top of event-driven systems with a much smaller memory overhead than full multithreading; each protothread requires only two bytes of memory. I show that dynamic linking of native code in standard ELF object code format is doable and feasible for wireless sensor networks by implementing a dynamic linker in the Contiki operating system. The results show that the energy overhead of dynamic linking of ELF files mainly is due to the ELF file format and not due to the dynamic linking mechanism as such. The impact of the research in this thesis has been and continues to be large. The software I have developed as part of this thesis is currently used by hundreds of companies in embedded devices in such diverse systems as car engines and satellites. The papers in this thesis are included as required reading in advanced courses on networked embedded systems and wireless sensor networks. / Contiki / uIP / Protothreads

A Research Report submitted to the Faculty of Engineering and the Built Environment, University of Witwatersrand, in the partial fulfilment of the requirements for the degree of Master of Science in Engineering Johannesburg, 2015. / Due to the enormous demand for multimedia services which relies hugely on the availability of spectrum, service providers and technologist are devising a means or method which is able to fully satisfy these growing demands. The availability of spectrum to meet these demands has been a lingering issue for the past couple of years. Many would have it tagged as spectrum scarcity but really the main problem is not how scarce the spectrum is but how efficiently allocated to use is the spectrum. Once such inefficiency is tackled effectively, then we are a step closer in meeting the enormous demands for uninterrupted services. However, to do so, there are techniques or methodologies being developed to aid in the efficient management of spectrum. In this research project, two methodologies were considered and the efficiency of these methodologies in the areas of spectrum management. The Geo-location Spectrum Database (GLSD) which is the most adopted technique and the Cognitive radio spectrum sensing technique are currently the available techniques in place. The TV whitespaces (TVWS) was explored using both techniques and certain comparison based on performances; implementation, practicability, cost and flexibility were used as an evaluation parameter in arriving at a conclusion. After accessing both methodologies, conclusions were deduced on the preferred methodology and how its use would efficiently solve the issues encountered in spectrum management

Em redes de sensores sem fio (RSSFs), o nó sorvedouro geralmente é a única entidade confiável. Uma RSSF desassistida é aquela na qual o nó sorvedouro está indisponível por um período de tempo, sendo necessário armazenar os dados coletados ao invés de transmiti-los para a entidade segura. Portanto, até o nó sorvedouro estar novamente disponível para a recepção dos dados, um adversário pode comprometer nós sensores distribuídos em uma região geográfica com o objetivo de encontrar e apagar determinadas unidades de dado. Com o objetivo de evitar este tipo de ataque, fornecendo sobrevivência de dados, estratégias geralmente utilizam confidencialidade e redundância de dados de forma que a agregação de dados por nós sensores seja inviável. Além disso, o decorrer do tempo permite que um adversário tenha maior poder de ataque através do comprometimento de diferentes conjuntos de nós sensores. Apresenta-se um protocolo de segurança para RSSFs desassistidas que, através da renovação do estado da rede, reduz a vantagem de um adversário em montar ataques a partir de dados obtidos com o decorrer do tempo. O mecanismo proposto fornece segurança para múltiplas unidades de dados e permite o uso de agregação de dados por nós sensores. Como forma de avaliação da proposta, foram realizados experimentos em nós sensores reais, além da elaboração de um modelo analítico e de simulações. Resultados indicam como usar o protocolo proposto em diferentes cenários para maximizar a sobrevivência de dados. Adicionalmente, apresenta-se a aplicabilidade do método proposto em cenários de redes heterogêneas, caso das redes de segurança pública, utilizando-se do paradigma de redes definidas por software (SDN) para implantação da rede. / In Wireless Sensor Networks, the base station is usually the only unconditionally trusted entity. If it is not connected for a period of time, the network is left unattended and sensor nodes cannot offload data in real time. Thus, until the base station becomes available, adversaries can compromise some sensor nodes and selectively destroy data. In order to prevent such attacks, providing the so-called data survival, strategies generally employ the use of cryptography in a scenario where decryption keys are exclusively in possession of the base station, which restricts the use of in-network aggregation. In addition, as time increases, mobile adversaries become stronger due to the ability of compromising different sets of nodes. We present a secure protocol that refreshes the state of the network and prevents adversaries from taking advantage of data obtained in prior rounds. The scheme provides security to multiple units of data and allows data aggregation to be performed by nodes. In order to evaluate the performance of the proposed scheme, we carried out measurements on real devices. We analyzed the security of the scheme analytically and through simulations. Results indicate increased time epochs before an adversary succeeds the attack, leading to more probability of data survival. We also apply our protocol to scenarios of heterogeneous networks, namely a public safety network scenario, which is deployed under the paradigm of software-defined networking (SDN).

As redes de sensores sem fio estão presentes nos mais diversos setores, formando um conjunto de elementos colaborativos que realizam o transporte da informação em cenários urbanos, agricultura de precisão, saúde e automação industrial. Sua utilização enfrenta desafios como necessidade constante de adaptações a alterações de topologia, baixas taxas de comunicação e uso eficiente de energia. Dessa forma, as aplicações dessas redes precisam suportar estas características dinamicamente. Esta tese propõe, então, um novo protocolo de roteamento: o HOFACO (Hybrid Objective Function based on Ant Colony Optimization), com base no funcionamento do padrão RPL (Routing Protocol for Low Power and Lossy Networks) aplicado à eficiência energética. Este protocolo proposto preserva as interfaces já consolidadas de roteamento e faz uso de uma informação heurística baseada em swarm intelligence (inteligência de enxames), por meio do uso de agentes - colônia de formigas -, para a composição híbrida de métricas utilizadas na avaliação do rank durante a construção de topologias. Esta proposta foi validada por meio de implementações em simulações e dispositivos reais em duas plataformas distintas: o Contiki e o OpenWSN. O processo de validação utilizou parâmetros como número de mensagens de controle, alterações de configurações topológicas, latência da rede e taxa de entrega de pacotes comparando-se a proposta a soluções tradicionais. Os resultados obtidos demonstraram um funcionamento compatível com estes parâmetros e uma melhoria em torno de 7,6% no sentido de redução do tempo de estabilização da rede. Adicionalmente, foi feito um teste comparativo de consumo de energia, evidenciando uma melhoria em termos de eficiência enérgica de até 20,9% da proposta com relação a protocolos tradicionais. / The wireless sensor networks are present in the most diverse sectors, forming a set of collaborative elements that perform the transport of information in urban scenarios, precision agriculture, health and industrial automation. Its use faces challenges as a constant need for adaptations to topology changes, low communication rates and efficient energy use. In this way, the applications of these networks must support these characteristics dynamically. This thesis proposes, therefore, a new routing protocol: the HOFACO (Hybrid Objective Function based on Ant Colony Optimization), based on the RPL (Routing Protocol for Low Power and Lossy Networks) applied to energy efficiency. This proposed protocol preserves the already consolidated routing interfaces and makes use of heuristic information based on swarm intelligence, using ant colony agents for the hybrid composition of metrics used in rank evaluation during the construction of topologies. This proposal was validated through implementations in simulations and real devices in two different platforms: Contiki and OpenWSN. The validation process used parameters such as number of control messages, changes of topological configurations, network latency and packet delivery rate, comparing the proposal to traditional solutions. The results showed a functioning compatible with these parameters and an improvement around 7.6% in the sense of reducing the time of stabilization of the network. In addition, a comparative test of energy consumption was made, evidencing an improvement in terms of energetic efficiency up to 20.9% of the proposal with respect to traditional protocols.

Les réseaux de capteurs sans fils sont de plus en plus utilisés dans des applications de surveillance de grands systèmes (feux de forêt, gaz dans les galeries minières, éthologie, ...). Une caractéristique de ces applications est que la topologie du réseau va être dynamique : soit les capteurs sont géographiquement mobiles (dispersion d'une nappe de pétrole), soit les conditions environnementales évoluent et modifient les capacités de communication des capteurs entre eux. Aussi, d'un système connexe, on peut évoluer vers un système clustérisé qui présente une rupture de la connectivité globale, et donc du système d'information. Une solution consiste à utiliser un (ou des) collecteur(s) des mesures (par exemple un robot mobile) qui va rétablir une connectivité discrète pour reconstituer à des échéances fixes un système d'information cohérent. Nous avons proposé un algorithme de clustering du réseau de capteurs sans fils adapté à la dynamique de sa topologie. La métrique choisie prend en compte la densité et la mobilité des noeuds, ainsi que leur énergie résiduelle. Ensuite, nous avons conçu un protocole de couche session permettant au collecteur de reconstruire le contexte de communication avec les clusters précédemment visités, sachant qu'ils ont pu évoluer en nombre, dispersion, fusion, ... Pour ce faire, il faut générer dynamiquement une trajectoire optimale du collecteur, en se basant sur un modèle d'estimation de la topologie, en prenant en compte les exigences applicatives (fréquence et volume des informations remontées). Pour la validation de l'algorithme de clustering et du protocole de couche session proposés, nous avons défini un modèle de noeud capteur que nous avons intégré à l'environnement de simulation Opnet / Wireless sensor networks are increasingly used in applications for monitoring large systems (forest fires, gas in the mine galleries, ethology, ...). A characteristic of these applications is that the topology of the network will be dynamic, either the sensors are geographically mobile (dispersion of an oil slick) or environmental conditions change and modify the communication capabilities of these sensors. Also, from a connex system, we can move to a clustered system that presents a discontinuity of the global connectivity, and therefore of the information system. One solution is to use one (or more) collector (s) that will restore a discrete connectivity at fixed deadlines to reconstruct a coherent information system. We have proposed a clustering algorithm of the wireless sensor network which is adapted to the dynamics of its topology. The chosen metric takes into account the density and the mobility of nodes and their remaining energy. Then we designed a session-layer protocol allowing the collector to reconstruct the context of communication with the previously visited clusters, knowing that they have evolved in number, splitting, merging, ... To do this, it is necessary to dynamically generate the trajectory of the collector, on the basis of a model of the topology, taking into account the application requirements (frequency and volume of the collected information). For the validation of the proposed clustering algorithm and the session-layer protocol, we defined a sensor model we have integrated in the Opnet simulation environment

The function of wireless sensor networks is to monitor events or gather information and report the information to a sink node, a central location or a base station. It is a requirement that the information is transmitted through the network efficiently. Wireless communication is the main activity that consumes energy in wireless sensor networks through idle listening, overhearing, interference and collision. It becomes essential to limit energy usage while maintaining communication between the sensor nodes and the sink node as the nodes die after the battery has been exhausted. Thus, conserving energy in a wireless sensor network is of utmost importance. Numerous methods to decrease energy expenditure and extend the lifetime of the network have been proposed. Researchers have devised methods to efficiently utilise the limited energy available for wireless sensor networks by optimising the design parameters and protocols. Cross-layer optimisation is an approach that has been employed to improve wireless communication. The essence of cross-layer scheme is to optimise the exchange and control of data between two or more layers to improve efficiency. The number of transmissions is therefore a vital element in evaluating overall energy usage. In this dissertation, a Markov Chain model was employed to analyse the tuning of two layers of the protocol stack, namely the Physical Layer (PHY) and Media Access Control layer (MAC), to find possible energy gains. The study was conducted utilising the IEEE 802.11 channel, SensorMAC (SMAC) and Slotted-Aloha (S-Aloha) medium access protocols in a star topology Wireless Temperature Sensor Network (WTSN). The research explored the prospective energy gains that could be realised through optimizing the Forward Error Correction (FEC) rate. Different Reed Solomon codes were analysed to explore the effect of protocol tuning on energy efficiency, namely transmission power, modulation method, and channel access. The case where no FEC code was used and analysed as the control condition. A MATLAB simulation model was used to identify the statistics of collisions, overall packets transmitted, as well as the total number of slots used during the transmission phase. The bit error probability results computed analytically were utilised in the simulation model to measure the probability of successful transmitting data in the physical layer. The analytical values and the simulation results were compared to corroborate the correctness of the models. The results indicate that energy gains can be accomplished by the suggested layer tuning approach. / Electrical and Mining Engineering / M. Tech. (Electrical Engineering)

A presença da tecnologia da informação dentro do agronegócio tem avançado e contribuído para a obtenção de melhores resultados para a gestão e, consequentemente, para o proprietário rural. Uma área de pesquisa que tem avançado dentro do setor rural é o monitoramento e a coleta de dados dos animais, em tempo real, possibilitando ao proprietário rural gerenciar seu rebanho, sem a necessidade de se deslocar ao local monitorado ou ao ponto de coleta de dados. A utilização das redes de sensores sem fio para fins de monitoração ainda possui limitações, como por exemplo a limitação do alcance do sinal de transmissão entre os nós sensores. Atualmente as tecnologias de transmissão de dados sem fio em uma rede de sensores alcançam pequenas distâncias, limitando o processo de detecção e coleta dos dados às áreas de pastagem menores. Assim, esta pesquisa teve como objetivo avaliar, através de simulação computacional, dois tipos de protocolos de comunicação sem fio que têm potencial para serem utilizados no monitoramento de sistemas de produção animal em longas distâncias: o protocolo ZigBee e o IEEE 802.1ah. Para a realização das simulações foram utilizados os softwares OMNet++ 4.5 e uma ferramenta de extensão chamada Mixim. Para tanto, foram criados dois cenários (ambientes) para cada protocolo, onde foram definidos: a área de cobertura, em torno de 1.500 metros, topologia da rede sem fio do tipo estática, dois nós para comunicação (um coordenador e um receptor) e as características do cenário. Por meio dos resultados obtidos através de simulação computacional com aplicação das métricas: distância, latência e taxa de perda de pacotes de dados nas simulações, observou-se que o protocolo ZigBee obteve o melhor desempenho em relação à distância de cobertura do sinal e da confiabilidade dos dados transmitidos. / The presence of information technology within the agribusiness has advanced and contributed to better results for the management and, consequently, to the landowner. One area of research that has advanced into the rural sector is the monitoring and collection of animal data in real time, allowing the landowner to manage his herd, without the need to move to the monitored site or the data collection point. However the technology of wireless sensor networks used for this purpose, has limitations and one of them is the signals range factor because, in order to make the data collection is necessary to install sensors and antennas in the pasture to reach the signals. Currently, wireless data transmission technologies in a network of sensors reach short distances, limiting the detection process and data collect to smaller pasture areas. This study aimed to find a long-distance transmission solution to reach areas of larger proportions pastures, and offer the landowner new monitoring resources. The methodology used to find such a solution was through simulations, using two transmission technologies: ZigBee and IEEE 802.11ah. To perform the simulations it was used the OMNet++ software, version 4.5 and an extension tool, called the Mixim. It was created two scenarios (environments) for each protocol, where has been defined: the coverage area of about 1,500 meters, network topology wireless static type, two nodes for communication (a coordinator and a receiver) and the characteristics of the environment. Through the results obtained by computer simulation with application of the metrics: distance, latency and data packets loss rate in the simulations, it was observed that the ZigBee protocol had the best performance in relation to the signal coverage distance and the transmitted data reliability.

Sensors are shaping many activities in our society with an endless array of potential applications in military, civilian, and medical application. They support different real world applications ranging from common household appliances to complex systems. Technological advancement has enabled sensors to be used in medical applications, wherein they are deployed to monitor patients and assist disabled patients. Sensors have been invaluable in saving lives, be it a soldier's life in a remote battlefield or a civilian's life in a disaster area or natural calamities. In every application the sensors are deployed in a pre-defined manner to perform a specific function. Understanding the basic structure of a sensor node is essential as this would be helpful in using the sensors in devices and environments that have not been explored. In this research, patterns are used to present a more abstract view of the structure and architecture of sensor nodes and wireless sensor networks. This would help an application designer to choose from different types of sensor nodes and sensor network architectures for applications such as robotic landmine detection or remote patient monitoring systems. Moreover, it would also help the network designer to reuse, combine or modify the architectures to suit more complex needs. More importantly, they can be integrated with complete IT applications. One of the important applications of wireless sensor networks in the medical field is a remote patient monitoring system. In this work, patterns were developed to describe the architecture of patient monitoring system. / This pattern describes how to connect sensor nodes and other wireless devices with each other to form a network that aims to monitor the vital signs of a person and report it to a central system. This central system could be accessed by the patient's healthcare provider for treatment purposes. This system shows one of the most important applications of sensors and it application which needs to be integrated with medical records and the use of patterns makes this integration much simpler. / by Anupama Sahu. / Thesis (M.S.C.S.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.