Contributions to the performance evaluation and improvement of the IPv6 routing protocol for low-power and lossy networks

Wireless Sensor Networks (WSNs) have become increasingly important. These networks comprise sensor and actuator nodes that enable intelligent monitoring and control applications in a wide spectrum of environments including smart cities, home automation, remote health and precision agriculture to mention a few. In certain IETF circles, networks of these characteristics are called Low Power and Lossy Networks (LLNs). Whereas most LLN protocol architectures were born without native IP support, there exists a tendency in the market towards IP convergence, since IP-based LLNs offer an open and tandardized way of connecting LLNs to the Internet, thus nabling the Internet of Things (IoT). Since most LLN configurations are multihop, and thus a routing protocol is required, the IETF created the Routing Over Low power and Lossy networks (ROLL) working group, which decided to develop a new routing protocol called IPv6 Routing Protocol for LLNs (RPL). RPL was specifically designed to meet the requirements of LLNs and is a central component of the IETF protocol suite for the IoT. Since RPL has already been deployed in millions of nodes, it is fundamental to characterize its properties, evaluate the influence of its main parameters and options on network performance, and analyze performance improvement possibilities. This PhD thesis presents the following original contributions in this field: 1. Evaluation of the influence of the main RPL parameters on the network convergence process over IEEE 802.15.4 multihop networks, in terms of network characteristics such as size and density. In addition, a mechanism that leverages an option available in RPL for accelerating network convergence has been proposed and evaluated. This study provides a guideline for configuring and selecting adequately crucial RPL parameters and mechanisms for achieving high network convergence performance, as well as a characterization of the related performance trade-offs. 2. Development of an analytical model for estimating the network convergence time of RPL in a static chain topology network of IEEE 802.15.4 nodes, in the presence of bit errors. Results show the scenarii in terms of BER and chain topology length that may dramatically degrade performance experienced by a user. The model provides a lower bound on the network convergence time for a random topology network. 3. Development of an analytical tool to estimate the number of control messages transmitted in a random topology static network which uses the Trickle algorithm (a transmission scheduling algorithm used in RPL) under steady state conditions. Results show the accuracy of the model, which can be used for both synchronous and asynchronous networks. The slight difference in performance between these two network configurations is discussed and illustrated. 4. Theoretical evaluation of the route change latency incurred by RPL when 6LoWPAN Neighbor Discovery (ND) is used. On this basis, a study on the impact of the relevant 6LoWPAN ND and RPL parameters on path availability and the trade-off between path availability and message overhead, has been carried out. 5. Development of a RPL simulator for OMNeT++ using the MiXiM framework.La importància de les Wireless Sensor Networks (WSNs) ha estat creixent significativament en els darrers anys. Aquestes xarxes comprenen node sensors i actuadors que possibiliten aplicacions de control i monitorització en un ampli ventall d'entorns, incloent les ciutats intel·ligents, automatització residencial, etc. En alguns cercles de l'IETF, aquestes xarxes són anomenades Low Power and Lossy Networks (LLNs). La majoria d'arquitectures de protocols van néixer sense suport natiu per a IP, per ha existit recentment una tendència en el mercat envers la convergència IP, ja que les LLN basades en IP ofereixen una manera oberta i estandaritzada de connectar LLNs a Internet, tot creant la Internet de les Coses. Atès que moltes configuracions de LLNsn multisalt, i per tant es requereix un protocol d'encaminament, l'IETF va crear el Routing Over Low power and Lossy networks (ROLL) working group, que va decidir dissenyar un nou protocol anomenat IPv6 Routing Protocol for LLNs (RPL). RPL va ser específicament dissenyat per complir amb els requeriments de les LLNs i és un component central de la pila de protocols de l'IETF per a la Internet de les Coses. Atès que RPL ha estat desplegat en milions de nodes, és fonamental caracteritzar les seves propietats, avaluar la influència dels seus paràmetres principals i opcions en el rendiment, i analitzar les possibilitats de millora del protocol. Aquesta tesi presenta les següents contribucions originals en aquest camp: 1. Avaluació de la influència dels principals paràmetres de RPL en el procés de convergència de la xarxa en xarxes IEEE 802.15.4, en termes de característiques com la mida i la densitat de la xarxa. A més a més, s'ha proposat i avaluat un mecanisme que utilitza una opci disponible en el RPL per a accelerar la convergència de xarxa. Aquest estudi proporciona una guia per configurar i escollir adequadament paràmetres crucials del protocol RPL per tal d'assolir una ràpida convergència de xarxa, això com una caracteritzaci dels compromisos relacionats. 2. Desenvolupament d'un model analátic per estimar el temps de convergència de xarxa de RPL en una topologia de xarxaestàtica en cadena de nodes IEEE 802.15.4, en presència d'errors. Els resultats mostren els escenaris en termes de BER i mida de la cadena que poden degradar les prestacions percebudes per l'usuari. El model proporciona una fita inferior del temps de convergència de xarxa per a una topologia aleatòria. 3. Desenvolupament d'una eina analítica per estimar el nombre de missatges de control transmesos en una xarxa de topologia aleat ria i estàtica on s'usa l'algoritme Trickle (algoritme de planificació i control de les transmissions emprat en RPL), en condicions de règim permanent. Els resultats mostren la precisió del model, que pot ser emprat en xarxes síncrones i asíncrones. La lleugera diferència de prestacions entre un escenari i l'altre és discutida i il·lustrada. 4. Avaluació teòrica del temps de canvi de ruta de RPL quan s'usa 6LoWPAN Neighbor Discovery (ND). En base a aixó , es realitza un estudi de l'impacte dels paràmetres rellevants de RPL i 6LoWPAN ND en la disponibilitat de cambi el compromís amb l'overhead de missatges. 5. Desenvolupament d'un simulador de RPL per a OMNeT++ usant el MiXiM framewor

IEEE 802.15.4e: a Survey

Several studies have highlighted that the IEEE 802.15.4 standard presents a number of limitations such as low reliability, unbounded packet delays and no protection against interference/fading, that prevent its adoption in applications with stringent requirements in terms of reliability and latency. Recently, the IEEE has released the 802.15.4e amendment that introduces a number of enhancements/modifications to the MAC layer of the original standard in order to overcome such limitations. In this paper we provide a clear and structured overview of all the new 802.15.4e mechanisms. After a general introduction to the 802.15.4e standard, we describe the details of the main 802.15.4e MAC behavior modes, namely Time Slotted Channel Hopping (TSCH), Deterministic and Synchronous Multi-channel Extension (DSME), and Low Latency Deterministic Network (LLDN). For each of them, we provide a detailed description and highlight the main features and possible application domains. Also, we survey the current literature and summarize open research issues

A survey of IoT protocols and their security issues through the lens of a generic IoT stack

International audienceThe Internet of things (IoT) is rapidly growing, and many security issues relate to its wireless technology. These security issues are challenging because IoT protocols are heterogeneous, suit different needs, and are used in different application domains. From this assessment, we identify the need to provide a homogeneous formalism applying to every IoT protocols. In this survey, we describe a generic approach with twofold challenges. The first challenge we tackle is the identification of common principles to define a generic approach to compare IoT protocol stack. We base the comparison on five different criteria: the range, the openness of the protocol, the interoperability, the topology and the security practices of these IoT protocols. The second challenge we consider is to find a generic way to describe fundamental IoT attacks regardless of the protocol used. This approach exposes similar attacks amongst different IoT protocols and is divided into three parts: attacks focusing on packets (passive and active cryptographic attacks), attacks focusing on the protocol (MITM, Flooding, Sybil, Spoofing, Wormhole attacks) and attacks focusing on the whole system (Sinkhole, Selective forwarding attacks). It also highlights which mechanisms are different between two protocols to make both of them vulnerable to an attack. Finally, we draw some lessons and perspectives from this transversal study

Data Routing for Mobile Internet of Things Applications

The Internet of things (IoT) represents a new era of networking, it envisions the Internet of the future where objects or “Things” are seamlessly connected to the Internet providing various services to the community. Countless applications can benefit from these new services and some of them have already come to life especially in healthcare and smart environments. The full realization of the IoT can only be achieved by having relevant standards that enable the integration of these new services with the Internet. The IEEE 802.15.4, 6LoWPAN and IPv6 standards define the framework for wireless sensor networks (WSN) to run using limited resources but still connect to the Internet and use IP addresses. The Internet engineering task force (IETF) developed a routing protocol for low-power and lossy networks (LLN) to provide bidirectional connectivity throughout the network, this routing protocol for LLNs (RPL) was standardized in RFC6550 in 2012 making it the standard routing protocol for IoT. With all the bright features and new services that come with the futuristic IoT applications, new challenges present themselves calling for the need to address them and provide efficient approaches to manage them. One of the most crucial challenges that faces data routing is the presence of mobile nodes, it affects energy consumption, end-to-end delay, throughput, latency and packet delivery ratio (PDR). This thesis addresses mobility issues from the data routing point of view, and presents a number of enhancements to the existing protocols in both mesh-under and route-over routing approaches, along with an introduction to relevant standards and protocols, and a literature review of the state of the art in research. A dynamic cluster head election protocol (DCHEP) is proposed to improve network availability and energy efficiency for mobile WSNs under the beacon-enabled IEEE 802.15.4 standard. The proposed protocol is developed and simulated using CASTALIA/OMNET++ with a realistic radio model and node behaviour. DCHEP improves the network availability and lifetime and maintains cluster hierarchy in a proactive manner even in a mobile WSN where all the nodes including cluster heads (CHs) are mobile, this is done by dynamically switching CHs allowing nodes to act as multiple backup cluster heads (BCHs) with different priorities based on their residual energy and connectivity to other clusters. DCHEP is a flexible and scalable solution targeted for dense WSNs with random mobility. The proposed protocol achieves an average of 33% and 26% improvement to the availability and energy efficiency respectively compared with the original standard. Moving to network routing, an investigation of the use of RPL in dynamic networks is presented to provide an enhanced RPL for different applications with dynamic mobility and diverse network requirements. This implementation of RPL is designed with a new dynamic objective-function (D-OF) to improve the PDR, end-to-end delay and energy consumption while maintaining low packet overhead and loop-avoidance. A controlled reverse-trickle timer is proposed based on received signal strength identification (RSSI) readings to maintain high responsiveness with minimum overhead, and consult the objective function when a movement or inconsistency is detected to help nodes make an informed decision. Simulations are done using Cooja with different mobility scenarios for healthcare and animal tracking applications considering multi-hop routing. The results show that the proposed dynamic RPL (D-RPL) adapts to different mobility scenarios and has a higher PDR, slightly lower end-to-end delay and reasonable energy consumption compared to related existing protocols. Many recent applications require the support of mobility and an optimised approach to efficiently handle mobile nodes is essential. A game scenario is formulated where nodes compete for network resources in a selfish manner, to send their data packets to the sink node. Each node counts as a player in the noncooperative game. The optimal solution for the game is found using the unique Nash equilibrium (NE) where a node cannot improve its pay-off function while other players use their current strategy. The proposed solution aims to present a strategy to control different parameters of mobile nodes (or static nodes in a mobile environment) including transmission rate, timers and operation mode in order to optimize the performance of RPL under mobility in terms of PDR, throughput, energy consumption and end-to-end-delay. The proposed solution monitors the mobility of nodes based on RSSI readings, it also takes into account the priorities of different nodes and the current level of noise in order to select the preferred transmission rate. An optimised protocol called game-theory based mobile RPL (GTM-RPL) is implemented and tested in multiple scenarios with different network requirements for Internet of Things applications. Simulation results show that in the presence of mobility, GTM-RPL provides a flexible and adaptable solution that improves throughput whilst maintaining lower energy consumption showing more than 10% improvement compared to related work. For applications with high throughput requirements, GTM-RPL shows a significant advantage with more than 16% improvement in throughput and 20% improvement in energy consumption. Since the standardization of RPL, the volume of RPL-related research has increased exponentially and many enhancements and studies were introduced to evaluate and improve this protocol. However, most of these studies focus on simulation and have little interest in practical evaluation. Currently, six years after the standardization of RPL, it is time to put it to a practical test in real IoT applications and evaluate the feasibility of deploying and using RPL at its current state. A hands-on practical testing of RPL in different scenarios and under different conditions is presented to evaluate its efficiency in terms of packet delivery ratio (PDR), throughput, latency and energy consumption. In order to look at the current-state of routing in IoT applications, a discussion of the main aspects of RPL and the advantages and disadvantages of using it in different IoT applications is presented. In addition to that, a review of the available research related to RPL is conducted in a systematic manner, based on the enhancement area and the service type. Finally, a comparison of related RPL-based protocols in terms of energy efficiency, reliability, flexibility, robustness and security is presented along with conclusions and a discussion of the possible future directions of RPL and its applicability in the Internet of the future

Estudi bibliomètric any 2014. Campus del Baix Llobregat: EETAC i ESAB

En el present informe s’analitza la producció científica de les dues escoles del Campus del Baix Llobregat, l’Escola d’Enginyeria de Telecomunicació i Aerospacial de Castelldefels (EETAC) i l’Escola Superior d’Agricultura de Barcelona (ESAB) durant el 2014.Postprint (author’s final draft

A study into prolonging Wireless Sensor Network lifetime during disaster scenarios

A Wireless Sensor Network (WSN) has wide potential for many applications. It can be employed for normal monitoring applications, for example, the monitoring of environmental conditions such as temperature, humidity, light intensity and pressure. A WSN is deployed in an area to sense these environmental conditions and send information about them to a sink. In certain locations, disasters such as forest fires, floods, volcanic eruptions and earth-quakes can happen in the monitoring area. During the disaster, the events being monitored have the potential to destroy the sensing devices; for example, they can be sunk in a flood, burnt in a fire, damaged in harmful chemicals, and burnt in volcano lava etc. There is an opportunity to exploit the energy of these nodes before they are totally destroyed to save the energy of the other nodes in the safe area. This can prolong WSN lifetime during the critical phase. In order to investigate this idea, this research proposes a new routing protocol called Maximise Unsafe Path (MUP) routing using Ipv6 over Low power Wireless Personal Area Networks (6LoWPAN). The routing protocol aims to exploit the energy of the nodes that are going to be destroyed soon due to the environment, by concentrating packets through these nodes. MUP adapts with the environmental conditions. This is achieved by classifying four different levels of threat based on the sensor reading information and neighbour node condition, and represents this as the node health status, which is included as one parameter in the routing decision. High priority is given to a node in an unsafe condition compared to another node in a safer condition. MUP does not allow packet routing through a node that is almost failed in order to avoid packet loss when the node fails. To avoid the energy wastage caused by selecting a route that requires a higher energy cost to deliver a packet to the sink, MUP always forwards packets through a node that has the minimum total path cost. MUP is designed as an extension of RPL, an Internet Engineering Task Force (IETF) standard routing protocol in a WSN, and is implemented in the Contiki Operating System (OS). The performance of MUP is evaluated using simulations and test-bed experiments. The results demonstrate that MUP provides a longer network lifetime during a critical phase of typically about 20\% when compared to RPL, but with a trade-off lower packet delivery ratio and end-to-end delay performances. This network lifetime improvement is crucial for the WSN to operate for as long as possible to detect and monitor the environment during a critical phase in order to save human life, minimise loss of property and save wildlife

Opportunistic data collection and routing in segmented wireless sensor networks

La surveillance régulière des opérations dans les aires de manoeuvre (voies de circulation et pistes) et aires de stationnement d'un aéroport est une tâche cruciale pour son fonctionnement. Les stratégies utilisées à cette fin visent à permettre la mesure des variables environnementales, l'identification des débris (FOD) et l'enregistrement des statistiques d'utilisation de diverses sections de la surface. Selon un groupe de gestionnaires et contrôleurs d'aéroport interrogés, cette surveillance est un privilège des grands aéroports en raison des coûts élevés d'acquisition, d'installation et de maintenance des technologies existantes. Les moyens et petits aéroports se limitent généralement à la surveillance de quelques variables environnementales et des FOD effectuée visuellement par l'homme. Cette dernière activité impose l'arrêt du fonctionnement des pistes pendant l'inspection. Dans cette thèse, nous proposons une solution alternative basée sur les réseaux de capteurs sans fil (WSN) qui, contrairement aux autres méthodes, combinent les propriétés de faible coût d'installation et maintenance, de déploiement rapide, d'évolutivité tout en permettant d'effectuer des mesures sans interférer avec le fonctionnement de l'aéroport. En raison de la superficie d'un aéroport et de la difficulté de placer des capteurs sur des zones de transit, le WSN se composerait d'une collection de sous-réseaux isolés les uns des autres et du puits. Pour gérer cette segmentation, notre proposition s'appuie sur l'utilisation opportuniste des véhicules circulants dans l'aéroport considérés alors comme un type spécial de nœud appelé Mobile Ubiquitous LAN Extension (MULE) chargé de collecter les données des sous-réseaux le long de son trajet et de les transférer vers le puits. L'une des exigences pour le déploiement d'un nouveau système dans un aéroport est qu'il cause peu ou pas d'interruption des opérations régulières. C'est pourquoi l'utilisation d'une approche opportuniste basé sur des MULE est privilégiée dans cette thèse. Par opportuniste, nous nous référons au fait que le rôle de MULE est joué par certains des véhicules déjà existants dans un aéroport et effectuant leurs déplacements normaux. Et certains nœuds des sous- réseaux exploiteront tout moment de contact avec eux pour leur transmettre les données à transférer ensuite au puits. Une caractéristique des MULEs dans notre application est qu'elles ont des trajectoires structurées (suivant les voies de circulation dans l'aéroport), en ayant éventuellement un contact avec l'ensemble des nœuds situés le long de leur trajet (appelés sous-puits). Ceci implique la nécessité de définir une stratégie de routage dans chaque sous-réseau, capable d'acheminer les données collectées des nœuds vers les sous-puits et de répartir les paquets de données entre eux afin que le temps en contact avec la MULE soit utilisé le plus efficacement possible. Dans cette thèse, nous proposons un protocole de routage remplissant ces fonctions. Le protocole proposé est nommé ACME (ACO-based routing protocol for MULE-assisted WSNs). Il est basé sur la technique d'Optimisation par Colonies de Fourmis. ACME permet d'assigner des nœuds à des sous-puits puis de définir les chemins entre eux, en tenant compte de la minimisation de la somme des longueurs de ces chemins, de l'équilibrage de la quantité de paquets stockés par les sous-puits et du nombre total de retransmissions. Le problème est défini comme une tâche d'optimisation multi-objectif qui est résolue de manière distribuée sur la base des actions des nœuds dans un schéma collaboratif. Nous avons développé un environnement de simulation et effectué des campagnes de calculs dans OMNeT++ qui montrent les avantages de notre protocole en termes de performances et sa capacité à s'adapter à une grande variété de topologies de réseaux.The regular monitoring of operations in both movement areas (taxiways and runways) and non-movement areas (aprons and aircraft parking spots) of an airport, is a critical task for its functioning. The set of strategies used for this purpose include the measurement of environmental variables, the identification of foreign object debris (FOD), and the record of statistics of usage for diverse sections of the surface. According to a group of airport managers and controllers interviewed by us, the wide monitoring of most of these variables is a privilege of big airports due to the high acquisition, installation and maintenance costs of most common technologies. Due to this limitation, smaller airports often limit themselves to the monitoring of environmental variables at some few spatial points and the tracking of FOD performed by humans. This last activity requires stopping the functioning of the runways while the inspection is conducted. In this thesis, we propose an alternative solution based on Wireless Sensor Network (WSN) which, unlike the other methods/technologies, combines the desirable properties of low installation and maintenance cost, scalability and ability to perform measurements without interfering with the regular functioning of the airport. Due to the large extension of an airport and the difficulty of placing sensors over transit areas, the WSN might result segmented into a collection of subnetworks isolated from each other and from the sink. To overcome this problem, our proposal relies on a special type of node called Mobile Ubiquitous LAN Extension (MULE), able to move over the airport surface, gather data from the subnetworks along its way and eventually transfer it to the sink. One of the main demands for the deployment of any new system in an airport is that it must have little or no interference with the regular operations. This is why the use of an opportunistic approach for the transfer of data from the subnetworks to the MULE is favored in this thesis. By opportunistic we mean that the role of MULE will be played by some of the typical vehicles already existing in an airport doing their normal displacements, and the subnetworks will exploit any moment of contact with them to forward data to the sink. A particular characteristic of the MULEs in our application is that they move along predefined structured trajectories (given by the layout of the airport), having eventual contact with the set of nodes located by the side of the road (so-called subsinks). This implies the need for a data routing strategy to be used within each subnetwork, able to lead the collected data from the sensor nodes to the subsinks and distribute the data packets among them so that the time in contact with the MULE is used as efficiently as possible. In this thesis, we propose a routing protocol which undertakes this task. Our proposed protocol is named ACME, standing for ACO-based routing protocol for MULE-assisted WSNs. It is founded on the well known Ant Colony Optimization (ACO) technique. The main advantage of ACO is its natural fit to the decentralized nature of WSN, which allows it to perform distributed optimizations (based on local interactions) leading to remarkable overall network performance. ACME is able to assign sensor nodes to subsinks and generate the corresponding multi-hop paths while accounting for the minimization of the total path length, the total subsink imbalance and the total number of retransmissions. The problem is defined as a multi-objective optimization task which is resolved in a distributed manner based on actions of the sensor nodes acting in a collaborative scheme. We conduct a set of computational experiments in the discrete event simulator OMNeT++ which shows the advantages of our protocol in terms of performance and its ability to adapt to a variety of network topologie

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