New Architectures for ubiquitous networks : use and adaptation of internet protocols over wireless sensor networks

This thesis focuses on the study of low-resource demanding protocols, communication techniques and software solutions to evaluate, optimise and implement Web service in WSNs. We start analysing the Web service architectures in order to choose the most appropriate for the constraints of WSNs, which is REST. Based on this analysis, we review the state-of-the-art of protocols that allows implementing REST Web services. To this end, we adopt the IEEE 802.15.4 standard for the physical and data-link layers, 6LoWPAN for the network layer and CoAP for the application layer. 6LoWPAN defines two forwarding techniques, which are called mesh under (MU) and route over (RO). It also provides a mechanism to fragment packets, which is called 6LoWPAN fragmentation. In part of the thesis, we study the effects that MU and RO have on communications using 6LoWPAN fragmentation. In particular, MU does not prevent forwarding unnecessary fragments and out-of-order delivery, which could lead to an inefficient use of bandwidth and a growth of energy consumption. We propose, then, a novel technique able to improve the performance of MU with fragmented packets, which we refer to as controlled mesh under (CMU). The results of a performance evaluation in a real WSN show that CMU is able to enhance the performance of MU by reducing its packet loss and end-to-end delay. In 6LoWPAN fragmentation, the loss of a fragment forces the retransmission of the entire packet. To overcome this limitation, CoAP defines blockwise transfer. It splits the packet into blocks and sends each one in reliable transactions, which introduces a significant communication overhead. We propose a novel analytical model to study blockwise and 6LoWPAN fragmentation, which is validated trough Monte Carlo simulations. Both techniques are compared in terms of reliability and delay. The results show that 6LoWPAN fragmentation is preferable for delay-constrained applications. For highly congested networks, blockwise slightly outperforms 6LoWPAN fragmentation in terms of reliability. CoAP defines the observe option to allow a client to register to a resource exposed by a server and to receive updates of its state. Existing QoS in the observe option supports partially timeliness. It allows specifying the validity of an update but it does not guarantee its on-time delivery. This approach is inefficient and does not consider applications, i.e. e-health, that requires the delivery of an update within a deadline. With this limitation in mind, we design and evaluate a novel mechanism for update delivery based on priority. The evaluation proves that implementing a delivery order improves the delay and delivery ratio of updates. Our proposal is also able to reduce the energy consumption allowing clients to express the class of updates that they wish to receive. In part of this thesis, we present our original library for TinyOS, which we referred to as TinyCoAP, and the design and implementation of a CoAP proxy. We compare TinyCoAP to CoapBlip, which is the CoAP implementation distributed with TinyOS. TinyCoAP proves to be able to reach a high code optimization and to reduce the impact over the memory of WSN nodes. The evaluation includes also the analysis of the CoAP reliability mechanism, which was still uncovered in the literature. As a novelty, we also compare CoAP with HTTP considering different solutions for the transport layer protocol such as UDP and persistent TCP connections. The CoAP proxy enables Web applications to transparently access the resources hosted in CoAP devices. It supports long-lived communications by including the WebSocket protocol. It also supports Web applications that use the traditional HTTP long-polling technique. Finally, one of the main contributions of the proxy design is the proposal of a standard URI path format to be used by Web applications to access to a CoAP resource.Esta tesis se enfoca en el estudio de protocolos de bajo consumo, técnicas de comunicación y software con el fin de evaluar, optimizar y desarrollar servicios Web en WSNs. Empezamos analizando la arquitectura de servicios Web con el objetivo de elegir la arquitectura más apropiada debido a las limitaciones de WSNs. Ésta se denomina REST. En base a este análisis, revisamos el estado del arte de los protocolos que permiten desarrollar servicios Web. Con este objetivo adoptamos el estándar IEEE 802.15.4 por la capa física y de enlace, 6LoWPAN por la de red y CoAP por la capa de aplicación. 6LoWPAN define dos técnicas de enrutamiento, denominadas 'Mesh Under' (MU) y 'Route Over' (RO). Asimismo ofrece un mecanismo para fragmentar paquetes, llamado 6LoWPAN fragmentation. En parte de la tesis estudiamos los efectos que MU y RO tienen sobre la comunicación que utiliza 6LoWPAN fragmentation. En particular, MU no previene enrutar fragmentos innecesarios y la entrega fuera de orden, lo cual podría provocar un uso ineficiente de ancho de banda y un crecimiento del consumo energía. Proponemos entonces nueva técnica capaz de mejorar las prestaciones de MU con paquetes fragmentados que denominamos 'Controlled Mesh Under' (CMU). Los resultados de una evaluación en una WSN real demuestran que CMU es capaz de mejorar las prestaciones de MU reduciendo la pérdida de paquetes y el retraso end-to-end. En 6LoWPAN fragmentation, la pérdida de un fragmento causa la retransmisión del paquete entero. Para evitar esta limitación CoAP define blockwise transfer. Esto divide el paquete en bloques y los envía en comunicaciones fiables provocando overhead. Proponemos un nuevo modelo analítico para estudiar blockwise y 6LoWPAN fragmentation cuya validación se realiza mediante simulaciones de Monte Carlo. Ambas técnicas se comparan en términos de fiabilidad y retraso. Los resultados muestran que es preferible usar 6LoWPAN fragmentation para las aplicaciones con restricciones en retraso. Para las redes mas congestionadas, blockwise mejora ligeramente 6LoWPAN fragmentation en términos de fiabilidad. CoAP define la opción observe para permitir a un cliente registrarse a un recurso proporcionado por un servidor y recibir actualizaciones de su estado. La QoS ofrecida por la opción observe proporciona soporte parcial por el timeliness. Esta permite especificar la validez de una actualización pero no garantiza su entrega a tiempo. Este enfoque es ineficiente y no incluye aplicaciones, como por ejemplo e-health que requieren la entrega de las actualizaciones en un plazo determinado. Teniendo en cuenta esta limitación, diseñamos y evaluamos un mecanismo novedoso para la entrega de actualizaciones basada en la prioridad. La evaluación demuestra que la implementación de una orden de entrega mejora la tasa de llegada y el retraso de las actualizaciones. Nuestra propuesta es capaz de reducir el consumo de energía permitiendo a los clientes expresar el tipo de actualización que desean recibir. En parte de esta tesis presentamos nuestra librería original pro TinyOS a la que nos referimos como TinyCoAP, así como el diseño y desarrollo de un Proxy CoAP. Comparamos TinyCoAP a CoapBlip, que es la aplicación distribuida con TinyOS. TinyCoAP demuestra ser capaz de alcanzar una alta optimización de código y reducir el impacto sobre la memoria de nodos de WSNs. La evaluación también incluye el análisis de la fiabilidad de CoAP que no había sido estudiada en la literatura. Como novedad también comparamos CoAP con HTTP, considerando diferentes soluciones para el protocolo de transporte como UDP y conexiones TCP persistentes. El Proxy CoAP permite a las aplicaciones Web acceder de manera transparente a los recursos almacenados en dispositivos CoAP. Éste incluye el protocolo WebSocket, que permite el establecimiento de conexiones long-lived. También permite el uso de aplicaciones Web con la tradicional técnica HTTP long-pollin

Performance Assessment of Routing Protocols for IoT/6LoWPAN Networks

The Internet of Things (IoT) proposes a disruptive communication paradigm that allows smart objects to exchange data among themselves to reach a common goal. IoT application scenarios are multiple and can range from a simple smart home lighting system to fully controlled automated manufacturing chains. In the majority of IoT deployments, things are equipped with small devices that can suffer from severe hardware and energy restrictions that are responsible for performing data processing and wireless communication tasks. Thus, due to their features, communication networks that are used by these devices are generally categorized as Low Power and Lossy Networks (LLNs). The considerable variation in IoT applications represents a critical issue to LLN networks, which should offer support to different requirements as well as keeping reasonable quality-of-service (QoS) levels. Based on this challenge, routing protocols represent a key issue in IoT scenarios deployment. Routing protocols are responsible for creating paths among devices and their interactions. Hence, network performance and features are highly dependent on protocol behavior. Also, based on the adopted protocol, the support for some specific requirements of IoT applications may or may not be provided. Thus, a routing protocol should be projected to attend the needs of the applications considering the limitations of the device that will execute them. Looking to attend the demand of routing protocols for LLNs and, consequently, for IoT networks, the Internet Engineering Task Force (IETF) has designed and standardized the IPv6 Routing Protocol for Low Power and Lossy Networks (RPL). This protocol, although being robust and offering features to fulfill the need of several applications, still presents several faults and weaknesses (mainly related to its high complexity and memory requirement), which limits its adoption in IoT scenarios. An alternative to RPL, the Lightweight On-demand Ad Hoc Distancevector Routing Protocol – Next Generation (LOADng) has emerged as a less complicated routing solution for LLNs. However, the cost of its simplicity is paid for with the absence of adequate support for a critical set of features required for many IoT environments. Thus, based on the challenging open issues related to routing in IoT networks, this thesis aims to study and propose contributions to better attend the network requirements of IoT scenarios. A comprehensive survey, reviewing state-of-the-art routing protocols adopted for IoT, identified the strengths and weaknesses of current solutions available in the literature. Based on the identified limitations, a set of improvements is designed to overcome these issues and enhance IoT network performance. The novel solutions are proposed to include reliable and efficient support to attend the needs of IoT applications, such as mobility, heterogeneity, and different traffic patterns. Moreover, mechanisms to improve the network performance in IoT scenarios, which integrate devices with different communication technologies, are introduced. The studies conducted to assess the performance of the proposed solutions showed the high potential of the proposed solutions. When the approaches presented in this thesis were compared with others available in the literature, they presented very promising results considering the metrics related to the Quality of Service (QoS), network and energy efficiency, and memory usage as well as adding new features to the base protocols. Hence, it is believed that the proposed improvements contribute to the state-of-the-art of routing solutions for IoT networks, increasing the performance and adoption of enhanced protocols.A Internet das Coisas, do inglês Internet of Things (IoT), propõe um paradigma de comunicação disruptivo para possibilitar que dispositivos, que podem ser dotados de comportamentos autónomos ou inteligentes, troquem dados entre eles buscando alcançar um objetivo comum. Os cenários de aplicação do IoT são muito variados e podem abranger desde um simples sistema de iluminação para casa até o controle total de uma linha de produção industrial. Na maioria das instalações IoT, as “coisas” são equipadas com um pequeno dispositivo, responsável por realizar as tarefas de comunicação e processamento de dados, que pode sofrer com severas restrições de hardware e energia. Assim, devido às suas características, a rede de comunicação criada por esses dispositivos é geralmente categorizada como uma Low Power and Lossy Network (LLN). A grande variedade de cenários IoT representam uma questão crucial para as LLNs, que devem oferecer suporte aos diferentes requisitos das aplicações, além de manter níveis de qualidade de serviço, do inglês Quality of Service (QoS), adequados. Baseado neste desafio, os protocolos de encaminhamento constituem um aspecto chave na implementação de cenários IoT. Os protocolos de encaminhamento são responsáveis por criar os caminhos entre os dispositivos e permitir suas interações. Assim, o desempenho e as características da rede são altamente dependentes do comportamento destes protocolos. Adicionalmente, com base no protocolo adotado, o suporte a alguns requisitos específicos das aplicações de IoT podem ou não ser fornecidos. Portanto, estes protocolos devem ser projetados para atender as necessidades das aplicações assim como considerando as limitações do hardware no qual serão executados. Procurando atender às necessidades dos protocolos de encaminhamento em LLNs e, consequentemente, das redes IoT, a Internet Engineering Task Force (IETF) desenvolveu e padronizou o IPv6 Routing Protocol for Low Power and Lossy Networks (RPL). O protocolo, embora seja robusto e ofereça recursos para atender às necessidades de diferentes aplicações, apresenta algumas falhas e fraquezas (principalmente relacionadas com a sua alta complexidade e necessidade de memória) que limitam sua adoção em cenários IoT. Em alternativa ao RPL, o Lightweight On-demand Ad hoc Distance-vector Routing Protocol – Next Generation (LOADng) emergiu como uma solução de encaminhamento menos complexa para as LLNs. Contudo, o preço da simplicidade é pago com a falta de suporte adequado para um conjunto de recursos essenciais necessários em muitos ambientes IoT. Assim, inspirado pelas desafiadoras questões ainda em aberto relacionadas com o encaminhamento em redes IoT, esta tese tem como objetivo estudar e propor contribuições para melhor atender os requisitos de rede em cenários IoT. Uma profunda e abrangente revisão do estado da arte sobre os protocolos de encaminhamento adotados em IoT identificou os pontos fortes e limitações das soluções atuais. Com base nas debilidades encontradas, um conjunto de soluções de melhoria é proposto para superar carências existentes e melhorar o desempenho das redes IoT. As novas soluções são propostas para incluir um suporte confiável e eficiente capaz atender às necessidades das aplicações IoT relacionadas com suporte à mobilidade, heterogeneidade dos dispositivos e diferentes padrões de tráfego. Além disso, são introduzidos mecanismos para melhorar o desempenho da rede em cenários IoT que integram dispositivos com diferentes tecnologias de comunicação. Os vários estudos realizados para mensurar o desempenho das soluções propostas mostraram o grande potencial do conjunto de melhorias introduzidas. Quando comparadas com outras abordagens existentes na literatura, as soluções propostas nesta tese demonstraram um aumento do desempenho consistente para métricas relacionadas a qualidade de serviço, uso de memória, eficiência energética e de rede, além de adicionar novas funcionalidades aos protocolos base. Portanto, acredita-se que as melhorias propostas contribuiem para o avanço do estado da arte em soluções de encaminhamento para redes IoT e aumentar a adoção e utilização dos protocolos estudados

IDHOCNET-A Novel Protocol Stack and Architecture for Ad hoc Networks

Presently employed Internet Protocol (IP) stack possesses number of architectural problems. The issues like Dual/Overriding role of IP addresses, mobility, multi-homing etc are the limitations for the infrastructure oriented networks which even have support of Dynamic Host Configuration Protocol (DHCP), Domain Name System (DNS), Network Address Translation (NAT) servers, etc. Such issues are extremely complex to handle in the case of multi-hop wireless ad hoc networks which lack the support of any infrastructure component. The contemporary research direction for the improvement of present Internet architecture mainly focuses on the use of real identifiers instead of IP addresses for host identification in the network. However, the proposed architectures mostly discuss the infrastructure oriented network models and minimal research has been conducted in the direction of proposals for ad hoc networks.  In this paper we provide a thorough discussion on the practical usage issues of IP based ad hoc network implementation. In order to resolve the present limitations of ad hoc networks, we describe an implementation of a novel identifier based ad hoc network protocol stack and architecture known as IDHOCNET (Identifier based ad hoc network). The architecture proposes a novel paradigm of identifier based applications for multi-hop wireless ad hoc environment. The proposed system further provides backward compatibility to support co-existence with IP based applications. As a proof of concept, the architecture has been implemented on Linux platform with WiFi interfaces. Various practical scenarios with architectural insight are presented to demonstrate the practicability of the proposed approach

A critical analysis of research potential, challenges and future directives in industrial wireless sensor networks

In recent years, Industrial Wireless Sensor Networks (IWSNs) have emerged as an important research theme with applications spanning a wide range of industries including automation, monitoring, process control, feedback systems and automotive. Wide scope of IWSNs applications ranging from small production units, large oil and gas industries to nuclear fission control, enables a fast-paced research in this field. Though IWSNs offer advantages of low cost, flexibility, scalability, self-healing, easy deployment and reformation, yet they pose certain limitations on available potential and introduce challenges on multiple fronts due to their susceptibility to highly complex and uncertain industrial environments. In this paper a detailed discussion on design objectives, challenges and solutions, for IWSNs, are presented. A careful evaluation of industrial systems, deadlines and possible hazards in industrial atmosphere are discussed. The paper also presents a thorough review of the existing standards and industrial protocols and gives a critical evaluation of potential of these standards and protocols along with a detailed discussion on available hardware platforms, specific industrial energy harvesting techniques and their capabilities. The paper lists main service providers for IWSNs solutions and gives insight of future trends and research gaps in the field of IWSNs

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

Wireless Technologies for Indoor Asset Positioning

The Positioning of assets in a manufacturing industry is one of the milestones in the process to increase the visibility inside the factory and improve the current manufacturing practices. Furthermore, in order to cope with the high mobility of the assets in a factory, the utilization of wireless technologies has been increased in the past few years in order to develop the positioning applications. However, the utilization of these technologies must not increase the complexity of the manufacturing systems. Therefore, the utilization of a common network protocol such as the Internet Protocol is preferred. The theoretical part of this thesis work presents a general description of the wireless technologies used in industrial environments. Additionally, it discusses the different methodologies and algorithms used for the positioning of assets applications in wireless networks in more detail. Furthermore, an introduction to the latest efforts and systems developed to address the problem of position estimation of assets in wireless networks is provided. In order to understand the realization of the IP-based wireless sensor networks, a brief review of the operating systems supporting this characteristic is presented. Finally a survey about the IP-ready wireless sensor network is performed in order to select the most suitable platform to use in the practical part of this work. The practical part of this thesis work focuses on the implementation of a real-time position estimation tool for manufacturing assets based on a Wireless Sensor Network for indoor environments. The main purpose is to estimate the position of a pallet allocated on a light assembly manufacturing line. In addition, the wireless sensor network utilizes the Internet Protocol version 6 as the networking protocol. Furthermore, the estimation parameter utilized by the tool is the received signal strength. Consequently, the position estimation methodologies based on the received signal strength are implemented by this tool. Finally, the position estimation tool was tested which is documented in the results section. /Kir1

State-of-the-art in Power Line Communications: from the Applications to the Medium

In recent decades, power line communication has attracted considerable attention from the research community and industry, as well as from regulatory and standardization bodies. In this article we provide an overview of both narrowband and broadband systems, covering potential applications, regulatory and standardization efforts and recent research advancements in channel characterization, physical layer performance, medium access and higher layer specifications and evaluations. We also identify areas of current and further study that will enable the continued success of power line communication technology.Comment: 19 pages, 12 figures. Accepted for publication, IEEE Journal on Selected Areas in Communications. Special Issue on Power Line Communications and its Integration with the Networking Ecosystem. 201