Application-Driven Wireless Sensor Networks

The growth of wireless networks has resulted in part from requirements for connecting people and advances in radio technologies. Recently there has been an increasing trend towards enabling the Internet-of-Things (IoT). Thousands of tiny devices interacting with their environments are being inter-networked and made accessible through the Internet. For that purpose, several communications protocols have been defined making use of the IEEE 802.15.4 Physical and MAC layers. The 6LoWPAN Network Layer adaptation protocol is an example which bridges the gap between low power devices and the IP world. Since its release, the design of routing protocols became increasingly important and the IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) emerged as the IETF proposed standard protocol for IPv6-based multi-hop Wireless Sensor Networks (WSN). This thesis considers that the sensor nodes form a large IPv6 network making use of above technologies and protocols, and that the sensor nodes are enabled to run one or more applications. It is also assumed that the applications and the sensor nodes to which they are associated, are not always active, alternating between active and inactive states. The thesis aims to design a new energy efficient communications solution for WSN by exploring the hypothesis that the network is aware of the traffic generated by the applications running in the sensor nodes. Therefore, the thesis provides two major contributions: 1) a cross-layer mechanism using application layer and network layer information to constrainRPL-defined routing trees (RPL-BMARQ); 2) an Application-Driven WSN node synchronization mechanism for RPL-BMARQ. RPL-BMARQ is designed as an extension to the RPLrouting protocol using information shared by the application and routing layers to construct Directed Acyclic Graphs (DAGs), allowing the nodes to select parents with respect to the applications they run. By jointly considering the neighbors of each node, the applications each node runs, and the forwarding capabilities of a node, we provide a communications solution which enables the data of every application and sensor node to be transferred, while keeping the overall energy consumed low by reducing the time the nodes are active and reducing the total number of multicast packets exchanged. Therefore, RPL-BMARQ helps reducing the network energy consumption since it restricts radio communication activities while maintaining throughput fairness and packet reception ratio high. The mechanism was evaluated using four scenarios with different network topologies and compared against "standard RPL". The results obtained show that the mechanism enables lower energy consumption since the nodes are more often put a sleep, reducing the total number of packets exchanged, while maintaining fairness and query success rates high. The Application-Driven WSN node synchronization mechanism for RPL-BMARQ was designed to maintain the sensor nodes synchronized according to the duty cycle of the applications they run. The mechanism jointly uses cross-layer information and the Exponentially Weighted Moving Average (EWMA) technique for calculating in run-time average network delays which are used to control the time the sensor nodes would sleep in the next cycle in order to wake up just before the next activity period starts. This mechanism enables all the sensor nodes to go asleep and to wake up in synchronism. The mechanism was theoretically evaluated and simulated, and the results obtained show that the synchronization mechanism works as previewed. The results also showed that, when designing WSN applications with this mechanism, the nodes not involved in communications are kept sleeping as much as possible, waking up when necessary and in synchronism. In order to confirm the validity of the mechanisms designed, we also tested them in real environments where the results were confirmed

Routing and Mobility on IPv6 over LoWPAN

The IoT means a world-wide network of interconnected objects based on standard communication protocols. An object in this context is a quotidian physical device augmented with sensing/actuating, processing, storing and communication capabilities. These objects must be able to interact with the surrounding environment where they are placed and to cooperate with neighbouring objects in order to accomplish a common objective. The IoT objects have also the capabilities of converting the sensed data into automated instructions and communicating them to other objects through the communication networks, avoiding the human intervention in several tasks. Most of IoT deployments are based on small devices with restricted computational resources and energy constraints. For this reason, initially the scientific community did not consider the use of IP protocol suite in this scenarios because there was the perception that it was too heavy to the available resources on such devices. Meanwhile, the scientific community and the industry started to rethink about the use of IP protocol suite in all IoT devices and now it is considered as the solution to provide connectivity between the IoT devices, independently of the Layer 2 protocol in use, and to connect them to the Internet. Despite the use of IP suite protocol in all devices and the amount of solutions proposed, many open issues remain unsolved in order to reach a seamless integration between the IoT and the Internet and to provide the conditions to IoT service widespread. This thesis addressed the challenges associated with the interconnectivity between the Internet and the IoT devices and with the security aspects of the IoT. In the interconnectivity between the IoT devices and the Internet the problem is how to provide valuable information to the Internet connected devices, independently of the supported IP protocol version, without being necessary accessed directly to the IoT nodes. In order to solve this problem, solutions based on Representational state transfer (REST) web services and IPv4 to IPv6 dual stack transition mechanism were proposed and evaluated. The REST web service and the transition mechanism runs only at the border router without penalizing the IoT constrained devices. The mitigation of the effects of internal and external security attacks minimizing the overhead imposed on the IoT devices is the security challenge addressed in this thesis. Three different solutions were proposed. The first is a mechanism to prevent remotely initiated transport level Denial of Service attacks that avoids the use of inefficient and hard to manage traditional firewalls. It is based on filtering at the border router the traffic received from the Internet and destined to the IoT network according to the conditions announced by each IoT device. The second is a network access security framework that can be used to control the nodes that have access to the network, based on administrative approval, and to enforce security compliance to the authorized nodes. The third is a network admission control framework that prevents IoT unauthorized nodes to communicate with IoT authorized nodes or with the Internet, which drastically reduces the number of possible security attacks. The network admission control was also exploited as a management mechanism as it can be used to manage the network size in terms of number of nodes, making the network more manageable, increasing its reliability and extending its lifetime.A IoT (Internet of Things) tem suscitado o interesse tanto da comunidade académica como da indústria, uma vez que os campos de aplicação são inúmeros assim como os potenciais ganhos que podem ser obtidos através do uso deste tipo de tecnologia. A IoT significa uma rede global de objetos ligados entre si através de uma rede de comunicações baseada em protocolos standard. Neste contexto, um objeto é um objeto físico do dia a dia ao qual foi adicionada a capacidade de medir e de atuar sobre variáveis físicas, de processar e armazenar dados e de comunicar. Estes objetos têm a capacidade de interagir com o meio ambiente envolvente e de cooperar com outros objetos vizinhos de forma a atingirem um objetivo comum. Estes objetos também têm a capacidade de converter os dados lidos em instruções e de as comunicar a outros objetos através da rede de comunicações, evitando desta forma a intervenção humana em diversas tarefas. A maior parte das concretizações de sistemas IoT são baseados em pequenos dispositivos autónomos com restrições ao nível dos recursos computacionais e de retenção de energia. Por esta razão, inicialmente a comunidade científica não considerou adequado o uso da pilha protocolar IP neste tipo de dispositivos, uma vez que havia a perceção de que era muito pesada para os recursos computacionais disponíveis. Entretanto, a comunidade científica e a indústria retomaram a discussão acerca dos benefícios do uso da pilha protocolar em todos os dispositivos da IoT e atualmente é considerada a solução para estabelecer a conetividade entre os dispositivos IoT independentemente do protocolo da camada dois em uso e para os ligar à Internet. Apesar do uso da pilha protocolar IP em todos os dispositivos e da quantidade de soluções propostas, são vários os problemas por resolver no que concerne à integração contínua e sem interrupções da IoT na Internet e de criar as condições para a adoção generalizada deste tipo de tecnologias. Esta tese versa sobre os desafios associados à integração da IoT na Internet e dos aspetos de segurança da IoT. Relativamente à integração da IoT na Internet o problema é como fornecer informação válida aos dispositivos ligados à Internet, independentemente da versão do protocolo IP em uso, evitando o acesso direto aos dispositivos IoT. Para a resolução deste problema foram propostas e avaliadas soluções baseadas em web services REST e em mecanismos de transição IPv4 para IPv6 do tipo pilha dupla (dual stack). O web service e o mecanismo de transição são suportados apenas no router de fronteira, sem penalizar os dispositivos IoT. No que concerne à segurança, o problema é mitigar os efeitos dos ataques de segurança internos e externos iniciados local e remotamente. Foram propostas três soluções diferentes, a primeira é um mecanismo que minimiza os efeitos dos ataques de negação de serviço com origem na Internet e que evita o uso de mecanismos de firewalls ineficientes e de gestão complexa. Este mecanismo filtra no router de fronteira o tráfego com origem na Internet é destinado à IoT de acordo com as condições anunciadas por cada um dos dispositivos IoT da rede. A segunda solução, é uma framework de network admission control que controla quais os dispositivos que podem aceder à rede com base na autorização administrativa e que aplica políticas de conformidade relativas à segurança aos dispositivos autorizados. A terceira é um mecanismo de network admission control para redes 6LoWPAN que evita que dispositivos não autorizados comuniquem com outros dispositivos legítimos e com a Internet o que reduz drasticamente o número de ataques à segurança. Este mecanismo também foi explorado como um mecanismo de gestão uma vez que pode ser utilizado a dimensão da rede quanto ao número de dispositivos, tornando-a mais fácil de gerir e aumentando a sua fiabilidade e o seu tempo de vida

Using Cooja for WSN Simulations: Some New Uses and Limits

International audienceThe Cooja/MSPSim network simulation framework is widely used for developing and debugging, but also for performance evaluation of WSN projects.We show in this paper that Cooja is not limited only to the simulation of the Contiki OS based systems and networks, but can also be extended to perform simulation experiments of other OS based platforms, especially that with RIOT OS.Moreover, when performing our own simulations with Cooja and MSPSim, we observed timing inconsistencies with identical experimentations made on actual hardware. Such inaccuracies clearly impair the use of the Cooja/MSPSim framework as a performance evaluation tool, at least for time-related performance parameters.We will present in this paper, as our contributions: On the one hand, how to use Cooja with projects not related to Con-tiki OS; On the other hand, the detailed results of our investigations on the inaccuracy problems, as well as the consequences of this issue, and give possible leads to fix or avoid it

A holistic architecture using peer to peer (P2P) protocols for the internet of things and wireless sensor networks

Wireless Sensor Networks (WSNs) interact with the physical world using sensing and/or actuation. The wireless capability of WSN nodes allows them to be deployed close to the sensed phenomenon. Cheaper processing power and the use of micro IP stacks allow nodes to form an “Internet of Things” (IoT) integrating the physical world with the Internet in a distributed system of devices and applications. Applications using the sensor data may be located across the Internet from the sensor network, allowing Cloud services and Big Data approaches to store and analyse this data in a scalable manner, supported by new approaches in the area of fog and edge computing. Furthermore, the use of protocols such as the Constrained Application Protocol (CoAP) and data models such as IPSO Smart Objects have supported the adoption of IoT in a range of scenarios. IoT has the potential to become a realisation of Mark Weiser’s vision of ubiquitous computing where tiny networked computers become woven into everyday life. This presents the challenge of being able to scale the technology down to resource-constrained devices and to scale it up to billions of devices. This will require seamless interoperability and abstractions that can support applications on Cloud services and also on node devices with constrained computing and memory capabilities, limited development environments and requirements on energy consumption. This thesis proposes a holistic architecture using concepts from tuple-spaces and overlay Peer-to-Peer (P2P) networks. This architecture is termed as holistic, because it considers the flow of the data from sensors through to services. The key contributions of this work are: development of a set of architectural abstractions to provide application layer interoperability, a novel cache algorithm supporting leases, a tuple-space based data store for local and remote data and a Peer to Peer (P2P) protocol with an innovative use of a DHT in building an overlay network. All these elements are designed for implementation on a resource constrained node and to be extensible to server environments, which is shown in a prototype implementation. This provides the basis for a new P2P holistic approach that will allow Wireless Sensor Networks and IoT to operate in a self-organising ad hoc manner in order to deliver the promise of IoT

Tecnologias IoT para pastoreio e controlo de postura animal

The unwanted and adverse weeds that are constantly growing in vineyards, force wine producers to repeatedly remove them through the use of mechanical and chemical methods. These methods include machinery such as plows and brushcutters, and chemicals as herbicides to remove and prevent the growth of weeds both in the inter-row and under-vine areas. Nonetheless, such methods are considered very aggressive for vines, and, in the second case, harmful for the public health, since chemicals may remain in the environment and hence contaminate water lines. Moreover, such processes have to be repeated over the year, making it extremely expensive and toilsome. Using animals, usually ovines, is an ancient practice used around the world. Animals, grazing in vineyards, feed from the unwanted weeds and fertilize the soil, in an inexpensive, ecological and sustainable way. However, sheep may be dangerous to vines since they tend to feed on grapes and on the lower branches of the vines, which causes enormous production losses. To overcome that issue, sheep were traditionally used to weed vineyards only before the beginning of the growth cycle of grapevines, thus still requiring the use of mechanical and/or chemical methods during the remainder of the production cycle. To mitigate the problems above, a new technological solution was investigated under the scope of the SheepIT project and developed in the scope of this thesis. The system monitors sheep during grazing periods on vineyards and implements a posture control mechanism to instruct them to feed only from the undesired weeds. This mechanism is based on an IoT architecture, being designed to be compact and energy efficient, allowing it to be carried by sheep while attaining an autonomy of weeks. In this context, the thesis herein sustained states that it is possible to design an IoT-based system capable of monitoring and conditioning sheep’s posture, enabling a safe weeding process in vineyards. Moreover, we support such thesis in three main pillars that match the main contributions of this work and that are duly explored and validated, namely: the IoT architecture design and required communications, a posture control mechanism and the support for a low-cost and low-power localization mechanism. The system architecture is validated mainly in simulation context while the posture control mechanism is validated both in simulations and field experiments. Furthermore, we demonstrate the feasibility of the system and the contribution of this work towards the first commercial version of the system.O constante crescimento de ervas infestantes obriga os produtores a manter um processo contínuo de remoção das mesmas com recurso a mecanismos mecânicos e/ou químicos. Entre os mais populares, destacam-se o uso de arados e roçadores no primeiro grupo, e o uso de herbicidas no segundo grupo. No entanto, estes mecanismos são considerados agressivos para as videiras, assim como no segundo caso perigosos para a saúde pública, visto que os químicos podem permanecer no ambiente, contaminando frutos e linhas de água. Adicionalmente, estes processos são caros e exigem mão de obra que escasseia nos dias de hoje, agravado pela necessidade destes processos necessitarem de serem repetidos mais do que uma vez ao longo do ano. O uso de animais, particularmente ovelhas, para controlar o crescimento de infestantes é uma prática ancestral usada em todo o mundo. As ovelhas, enquanto pastam, controlam o crescimento das ervas infestantes, ao mesmo tempo que fertilizam o solo de forma gratuita, ecológica e sustentável. Não obstante, este método foi sendo abandonado visto que os animais também se alimentam da rama, rebentos e frutos da videira, provocando naturais estragos e prejuízos produtivos. Para mitigar este problema, uma nova solução baseada em tecnologias de Internet das Coisas é proposta no âmbito do projeto SheepIT, cuja espinha dorsal foi construída no âmbito desta tese. O sistema monitoriza as ovelhas enquanto estas pastoreiam nas vinhas, e implementam um mecanismo de controlo de postura que condiciona o seu comportamento de forma a que se alimentem apenas das ervas infestantes. O sistema foi incorporado numa infraestrutura de Internet das Coisas com comunicações sem fios de baixo consumo para recolha de dados e que permite semanas de autonomia, mantendo os dispositivos com um tamanho adequado aos animais. Neste contexto, a tese suportada neste trabalho defende que é possível projetar uma sistema baseado em tecnologias de Internet das Coisas, capaz de monitorizar e condicionar a postura de ovelhas, permitindo que estas pastem em vinhas sem comprometer as videiras e as uvas. A tese é suportada em três pilares fundamentais que se refletem nos principais contributos do trabalho, particularmente: a arquitetura do sistema e respetivo sistema de comunicações; o mecanismo de controlo de postura; e o suporte para implementação de um sistema de localização de baixo custo e baixo consumo energético. A arquitetura é validada em contexto de simulação, e o mecanismo de controlo de postura em contexto de simulação e de experiências em campo. É também demonstrado o funcionamento do sistema e o contributo deste trabalho para a conceção da primeira versão comercial do sistema.Programa Doutoral em Informátic

Recent Advances in Embedded Computing, Intelligence and Applications

The latest proliferation of Internet of Things deployments and edge computing combined with artificial intelligence has led to new exciting application scenarios, where embedded digital devices are essential enablers. Moreover, new powerful and efficient devices are appearing to cope with workloads formerly reserved for the cloud, such as deep learning. These devices allow processing close to where data are generated, avoiding bottlenecks due to communication limitations. The efficient integration of hardware, software and artificial intelligence capabilities deployed in real sensing contexts empowers the edge intelligence paradigm, which will ultimately contribute to the fostering of the offloading processing functionalities to the edge. In this Special Issue, researchers have contributed nine peer-reviewed papers covering a wide range of topics in the area of edge intelligence. Among them are hardware-accelerated implementations of deep neural networks, IoT platforms for extreme edge computing, neuro-evolvable and neuromorphic machine learning, and embedded recommender systems

Internet of Things From Hype to Reality

The Internet of Things (IoT) has gained significant mindshare, let alone attention, in academia and the industry especially over the past few years. The reasons behind this interest are the potential capabilities that IoT promises to offer. On the personal level, it paints a picture of a future world where all the things in our ambient environment are connected to the Internet and seamlessly communicate with each other to operate intelligently. The ultimate goal is to enable objects around us to efficiently sense our surroundings, inexpensively communicate, and ultimately create a better environment for us: one where everyday objects act based on what we need and like without explicit instructions