32 research outputs found

    Concurrent Geometric Multicasting

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    We present MCFR, a multicasting concurrent face routing algorithm that uses geometric routing to deliver a message from source to multiple targets. We describe the algorithm's operation, prove it correct, estimate its performance bounds and evaluate its performance using simulation. Our estimate shows that MCFR is the first geometric multicast routing algorithm whose message delivery latency is independent of network size and only proportional to the distance between the source and the targets. Our simulation indicates that MCFR has significantly better reliability than existing algorithms

    Indoor vehicles geolocalization using LoRaWAN

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    [EN] One of the main drawbacks of Global Navigation Satellite Sytems (GNSS) is that they do not work indoors. When inside, there is often no direct line from the satellite signals to the device and the ultra high frequency (UHF) used is blocked by thick, solid materials such as brick, metal, stone or wood. In this paper, we describe a solution based on the Long Range Wide Area Network (LoRaWAN) technology to geolocalise vehicles indoors. Through estimation of the behaviour of a LoRaWAN channel and using trilateration, the localisation of a vehicle can be obtained within a 20¿30 m range. Indoor geolocation for Intelligent Transporation Systems (ITS) can be used to locate vehicles of any type in underground parkings, keep a platoon of trucks in formation or create geo-fences, that is, sending an alert if an object moves outside a defined area, like a bicycle being stolen. Routing of heavy vehicles within an industrial setting is another possibility.This work was partially supported by the Ministerio de Ciencia, Innovación y Universidades, Programa Estatal de Investigación, Desarrollo e Innovación Orientada a los Retos de la Sociedad, Proyectos I+D+I 2018 , Spain, under Grant RTI2018-096384-B-I00.Manzoni, P.; Tavares De Araujo Cesariny Calafate, CM.; Cano, J.; Hernández-Orallo, E. (2019). Indoor vehicles geolocalization using LoRaWAN. Future Internet. 11(6):1-15. https://doi.org/10.3390/fi11060124S11511

    Design and prototyping of a network-enabled low-cost low-power seismic sensor monitoring system

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    Esta tese explora recentes desenvolvimentos em tecnologias de informação, comunicações e sensores no campo da sismologia. A tese aborda o potencial das redes de monitorização sísmica de elevada densidade na melhoria da resolução da actividade sísmica observada e, consequentemente, na melhor compreensão dos processos físicos que estão na base da ocorrência de terramotos. A tese argumenta que a tecnologia de sistemas de microelectromecânica (MEMS), usada na produção de acelerómetros de pequena dimensão, tem aplicabilidade e elevado potencial no domínio da sismologia. Acelerómetros MEMS já facilitaram a instalação de redes sísmicas de elevada densidade com superior resolução espacial pela Universidade da Califórnia (Rede Sísmica Comunitária) e pela Universidade de Évora (Rede Sísmica de Sensores do Alentejo), esta última ainda em fase de instalação. Neste contexto, a tese descreve o trabalho conduzido no desenho e desenvolvimento de sistemas de sensores baseados em acelerómetros MEMS. Este trabalho inclui a conceptualização de componentes de arquitectura usados para a implementação de quatro protótipos. Adicionalmente, foram também desenvolvidos os componentes necessários para a operação e gestão da rede de sensores, que inclui servidores dedicados a operar software especificamente desenvolvido neste trabalho. A tese descreve também a instalação e avaliação de protótipos, usando como base de comparação uma estação sísmica de elevado desempenho, recorrendo inclusivamente à actividade sísmica resultante de dois eventos sísmicos. A tese conclui que a arquitectura conceptualizada para o sistema sensor e para a rede de sensores demonstrou ser eficaz. Adicionalmente, embora a tecnologia MEMS seja promissora, ainda exibe limitações que limitam a sua aplicabilidade no domínio da sismologia, especificamente na observação de eventos sísmicos moderados e fortes. Conclui-se também que a instalação de acelerómetros MEMS em conjunto com sismómetros pode trazer benefícios na observação de actividade sísmica. Espera-se também que futuras gerações de acelerómetros MEMS possam ter uma adoção generalizada na sismologia; ABSTRACT: This thesis exploits advances in information technologies, communications and sensor systems to the field of seismology. It addresses the potential for high-density networks for seismic monitoring aiming to improve the resolution of the recorded seismic activity and, consequently, to improve the understanding of the physical processes that cause earthquakes, as well as to gather more detailed seismic characterisation of studied regions. It argues that microelectromechanical systems (MEMS) technology, used to produce small size accelerometers, has a potential application in seismology. Indeed, MEMS accelerometers have enabled the deployment of high-density seismic networks capable of monitoring seismic activity with high spatial resolution, such as CalTech's Community Seismic Network (CSN) and University of Évora’s SSN-Alentejo, currently in the deployment phase. In this context, this thesis describes the work conducted to design and develop low-cost seismic sensor systems, based on low-cost MEMS accelerometers. This work includes the conceptualisation of the architectural components that were implemented in four prototypes. Moreover, server-side components, necessary to operate and manage the sensor network, as well as to provide visualisation tools for users, are also developed and presented. This work also describes the field deployment and evaluation of selected prototypes, using a high-performance seismic station as the reference sensor for comparison, based on generated signals and two recorded seismic events. It is concluded that the herein conceptualised architecture for the high-dense network and sensor prototypes has been demonstrated to be effective. Moreover, albeit promising, MEMS accelerometers still exhibit performance limitations constraining their application in seismology addressing moderate and strong motion. In addition, MEMS accelerometers characteristics complement seismometers, thus installing MEMS accelerometers with seismometers, may provide additional insights concerning seismic activity and seismology in general. It is also expected that next generation MEMS accelerometers will be capable to compete with traditional seismometers, becoming the de facto technology in seismology

    Underwater Sensor Networks: Applications, Advances, and Challenges

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    This paper examines the main approaches and challenges in the design and implementation of underwater wireless sensor networks. We summarize key applications and the main phenomena related to acoustic propagation, and discuss how they affect the design and operation of communication systems and networking protocols at various layers. We also provide an overview of communications hardware, testbeds, and simulation tools available to the research community

    The Internet of Things Has a Gateway Problem

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    The vision of an Internet of Things (IoT) has captured the imag-ination of the world and raised billions of dollars, all before we stopped to deeply consider how all these Things should connect to the Internet. The current state-of-the-art requires application-layer gateways both in software and hardware that provide application-specific connectivity to IoT devices. In much the same way that it would be difficult to imagine requiring a new web browser for each website, it is hard to imagine our current approach to IoT connec-tivity scaling to support the IoT vision. The IoT gateway problem exists in part because today’s gateways conflate network connectiv-ity, in-network processing, and user interface functions. We believe that disentangling these functions would improve the connectivity potential for IoT devices. To realize the broader vision, we propose an architecture that leverages the increasingly ubiquitous presence of Bluetooth Low Energy radios to connect IoT peripherals to the Internet. In much the same way that WiFi access points revolution-ized laptop utility, we envision that a worldwide deployment of IoT gateways could revolutionize application-agnostic connectivity, thus breaking free from the stove-piped architectures now taking hold. In this paper, we present our proposed architecture, show example applications enabled by it, and explore research challenges in its implementation and deployment

    RESOURCE ALLOCATION AND EFFICIENT ROUTING IN WIRELESS NETWORKS

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    In wireless networks, devices (nodes) are connected by wireless links. An important issue is to set up high quality (high bandwidth) and efficient routing paths when one node wants to send packets to other nodes. Resource allocation is the foundation to guarantee high quality connections. In addition, it is critical to handle void areas in order to set up detour-free paths. Moreover, fast message broadcasting is essential in mobile wireless networks. Thus, my research includes dynamic channel allocation in wireless mesh networks, geographic routing in Ad Hoc networks, and message broadcasting in vehicular networks. The quality of connections in a wireless mesh network can be improved by equip- ping mesh nodes with multi-radios capable of tuning to non-overlapping channels. The essential problem is how to allocate channels to these multi-radio nodes. We develop a new bipartite-graph based channel allocation algorithm, which can improve bandwidth utilization and lower the possibility of starvation. Geographic routing in Ad Hoc networks is scalable and normally loop-free. However, traditional routing protocols often result in long detour paths when holes exist. We propose a routing protocol-Intermediate Target based Geographic Routing (ITGR) to solve this problem. The novelty is that a single forwarding path can be used to reduce the lengths of many future routing paths. We also develop a protocol called Hole Detection and Adaptive Geographic Routing, which identifies the holes efficiently by comparing the length of a routing path with the Euclidean distance between a pair of nodes. We then set up the shortest path based on it. Vehicles play an important role in our daily life. During inter-vehicle communication, it is essential that emergency information can be broadcast to surrounding vehicles quickly. We devise an approach that can find the best re-broadcasting node and propagate the message as fast as possible

    RF-based automated UAV orientation and landing system

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    The number of Unmanned Areal Vehicle (UAV) applications is growing tremendously. The most critical applications are operations in use cases like natural disasters and rescue activities. Many of these operations are performed on water scenarios. A standalone niche covering autonomous UAV operation is thus becoming increasingly important. One of the crucial parts of mentioned operations is a technology capable to land an autonomous UAV on a moving platform on top of a water surface. This approach could not be entirely possible without precise UAV positioning. However, conventional strategies that rely on satellite positioning may not always be reliable, due to the existence of accuracy errors given by surrounding environmental conditions, high interferences, or other factors, that could lead to the loss of the UAV. Therefore, the development of independent precise landing technology is essential. The main objective of this thesis is to develop precise landing framework by applying indoor positioning techniques based on RF-anchors to autonomous outdoor UAV operations for cases when a lower accuracy error than the provided by Global Navigation Satellite System (GNSS) is required. In order to analyze the landing technology, a simulation tool was developed. The developed positioning strategy is based on modifications of Gauss-Newton's method, which utilizes as an input parameter the number of anchors, the spacing between them, the initial UAV position, and the Friis-transmission formula to calculate the distance between the anchors and the UAV. As an output, a calculated position of the UAV with an accuracy in the range of tens of centimeters is reached. The simulation campaign shows the dependencies of the effects of the anchor's number and corresponding spacing on positioning accuracy. Also, the simulation campaign shows Gauss-Newton's method parameter value that maximizes the system performance. The results prove that this approach can be applied in a real-life scenario due to achievements of both high accuracy achieved and close to perfect estimated landing trajectory. Keywords: UAV, Positioning, Automatic Landing, Simulatio
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