Nowadays, wireless sensor networks can be found in many new application areas. In these sensor networks there may exit a part of the network which are difficult to access or lie in a wide area, far apart. A change in the software (e.g., function update or bug fix) can entail reprogramming of all sensor nodes. This is very time consuming and labour intensive, if the patching has to be done manually for each individual sensor nodes. In the area of mobile phones, the over the air (OTA) update function has been established very well with good reliability. In embedded systems such as sensor nodes, where resources are severely restricted, an update cannot be stored but must be programmed directly with the transfer. For this to be possible, a lot of basic functionality is needed to be established to correct errors or to be able to resume a failed programming. Within the framework of this thesis a concept for the transmission and distribution of the firmware and programming the sensor node is established. Focus here is to optimize the use of resources and to provide basic functionality within the programming mode.

Doctor of Philosophy / Department of Electrical and Computer Engineering / Balasubramaniam Natarajan / In recent years, there has been a rapid expansion in the development and use of low-power, low-cost wireless modules with sensing, computing, and communication functionality. A wireless sensor network (WSN) is a group of these devices networked together wirelessly. Wireless sensor networks have found widespread application in infrastructure, environmental, and human health monitoring, surveillance, and disaster management. While there are many interesting problems within the WSN framework, we address the challenge of energy availability in a WSN tasked with a cooperative objective. We develop approximation algorithms and execute an analysis of concave utility maximization in resource constrained systems. Our analysis motivates a unique algorithm which we apply to resource management in WSNs. We also investigate energy harvesting as a way of improving system lifetime. We then analyze the effect of using these limited and stochastically available communication resources on the convergence of decentralized optimization techniques. The main contributions of this research are: (1) new optimization formulations which explicitly consider the energy states of a WSN executing a cooperative task; (2) several analytical insights regarding the distributed optimization of resource constrained systems; (3) a varied set of algorithmic solutions, some novel to this work and others based on extensions of existing techniques; and (4) an analysis of the effect of using stochastic resources (e.g., energy harvesting) on the performance of decentralized optimization methods. Throughout this work, we apply our developments to distribution estimation and rate maximization. The simulation results obtained help to provide verification of algorithm performance. This research provides valuable intuition concerning the trade-offs between energy-conservation and system performance in WSNs.

The IoT concept has revolutionised the vision of the future Internet with the advent of standards such as 6LoWPAN making it feasible to extend the Internet into previously isolated environments, e.g., WSNs. The abstraction of resources as services, has opened these environments to a new plethora of potential applications. Moreover, the web service paradigm can be used to provide interoperability by offering a standard interface to interact with these services to enable WoT paradigm. However, these networks pose many challenges, in terms of limited resources, that make the adaptability of existing IP-based solutions infeasible. As traditional service discovery and selection solutions demand heavy communication and use bulky formats, which are unsuitable for these resource-constrained devices incorporating sleep cycles to save energy. Even a registry based approach exhibits burdensome traffic in maintaining the availability status of the devices. The feasible solution for service discovery and selection is instrumental to enable the wide application coverage of these networks in the future. This research project proposes, TRENDY, a new compact and adaptive registry-based SDP with context awareness for the IoT, with more emphasis given to constrained networks, e.g., 6LoWPAN It uses CoAP-based light-weight and RESTful web services to provide standard interoperable interfaces, which can be easily translated from HTTP. TRENDY's service selection mechanism collects and intelligently uses the context information to select appropriate services for user applications based on the available context information of users and services. In addition, TRENDY introduces an adaptive timer algorithm to minimise control overhead for status maintenance, which also reduces energy consumption. Its context-aware grouping technique divides the network at the application layer, by creating location-based groups. This grouping of nodes localises the control overhead and provides the base for service composition, localised aggregation and processing of data. Different grouping roles enable the resource-awareness by offering profiles with varied responsibilities, where high capability devices can implement powerful profiles to share the load of other low capability devices. Thus, it allows the productive usage of network resources. Furthermore, this research project proposes APPUB, an adaptive caching technique, that has the following benefits: it allows service hosts to share their load with the resource directory and also decreases the service invocation delay. The performance of TRENDY and its mechanisms is evaluated using an extensive number of experiments performed using emulated Tmote sky nodes in the COOJA environment. The analysis of the results validates the benefit of performance gain for all techniques. The service selection and APPUB mechanisms improve the service invocation delay considerably that, consequently, reduces the traffic in the network. The timer technique consistently achieved the lowest control overhead, which eventually decreased the energy consumption of the nodes to prolong the network lifetime. Moreover, the low traffic in dense networks decreases the service invocations delay, and makes the solution more scalable. The grouping mechanism localises the traffic, which increases the energy efficiency while improving the scalability. In summary, the experiments demonstrate the benefit of using TRENDY and its techniques in terms of increased energy efficiency and network lifetime, reduced control overhead, better scalability and optimised service invocation time.

This work starts from the proposition that it is beneficial to conserve communication energy in Wireless Sensor Networks (WSNs). For WSNs there is an added incentive for energy-efficient communication. The power supply of a sensor is often finite and small. Replenishing the power may be impractical and is likely to be costly. Wireless Sensor Networks are an important area of research. Data about the physical environment may be collected from hostile or friendly environments. Data is then transmitted to a destination without the need for communication cables. There are power and resource constraints upon WSNs, in addition WSN networks are often application specific. Different applications will often have different requirements. Further, WSNs are a shared medium system. The features of the MAC (Medium Access Control) protocol together with the application behaviour shape the communication states of the node. As each of these states have different power requirements the MAC protocol impacts upon the operation and power consumption efficiency. This work focuses on the development of an energy conservation protocol for WSNs where direct communication between sources and a base station is feasible. Whilst the multi-hop approach has been regarded as the underlying communication paradigm in WSNs, there are some scenarios where direct communication is applicable and a significant amount of communication energy can be saved. The Power & Reliability Aware Protocol has been developed. Its main objectives are to provide efficient data communication by means of energy conservation without sacrificing required reliability. This has been achieved by using direct communication, adaptive power adaptation and intelligent scheduling. The results of simulations illustrate the significance of communication energy and adaptive transmission. The relationship between Received Signal Strength Indicator (RSSI) and Packet Reception Rate (PRR) metrics is established and used to identify when power adaptation is required. The experimental results demonstrate an optimal region where lower power can be used without further reduction in the PRR. Communication delays depend upon the packet size whilst two-way propagation delay is very small. Accurate scheduling is achieved through monitoring the clock drift. A set of experiments were carried out to study benefits of direct vs. multi-hop communication. Significant transmitting current can be conserved if the direct communication is used. PoRAP is compared to Sensor-MAC (S-MAC), Berkeley-MAC (B-MAC) and Carrier Sense Multiple Access (CSMA). Parameter settings used in the Great Duck Island (GDI) a production habitat monitoring WSNs were applied. PoRAP consumes the least amount of energy.

<p>Recently, wireless sensor network (WSN) has become a promising technologywith a wide range of applications such as supply chain monitoringand environment surveillance. It is typically composed of multiple tiny devicesequipped with limited sensing, computing and wireless communicationcapabilities. Design of such networks presents several technique challengeswhile dealing with various requirements and diverse constraints. Performanceanalysis techniques are required to provide insight on design parametersand system behaviors.</p><p>Based on network calculus, we present a deterministic analysis methodfor evaluating the worst-case delay and buffer cost of sensor networks. Tothis end, three general traffic flow operators are proposed and their delayand buffer bounds are derived. These operators can be used in combinationto model any complex traffic flowing scenarios. Furthermore, the methodintegrates a variable duty cycle to allow the sensor nodes to operate at lowrates thus saving power. In an attempt to balance traffic load and improveresource utilization and performance, traffic splitting mechanisms areintroduced for mesh sensor networks. Based on network calculus, the delayand buffer bounds are derived in non-splitting and splitting scenarios.In addition, analysis of traffic splitting mechanisms are extended to sensornetworks with general topologies. To provide reliable data delivery in sensornetworks, retransmission has been adopted as one of the most popularschemes. We propose an analytical method to evaluate the maximum datatransmission delay and energy consumption of two types of retransmissionschemes: hop-by-hop retransmission and end-to-end retransmission.</p><p>We perform a case study of using sensor networks for a fresh food trackingsystem. Several experiments are carried out in the Omnet++ simulationenvironment. In order to validate the tightness of the two bounds obtainedby the analysis method, the simulation results and analytical results arecompared in the chain and mesh scenarios with various input traffic loads.From the results, we show that the analytic bounds are correct and tight.Therefore, network calculus is useful and accurate for performance analysisof wireless sensor network.</p> / Ipack VINN Excellence Center

Wireless Sensor Networks (WSNs) that use tiny wireless devices capable of communicating, processing, and sensing promise to have applications in virtually all fields. Smart homes and smart cities are just few of the examples that WSNs can enable. Despite their potential, WSNs suffer from reliability and energy limitations. In this study, we address the problem of designing Distributed Data Storage Systems (DDSSs) for WSNs using decentralized erasure codes. A unique aspect of WSNs is that their data is inherently decentralized. This calls for a decentralized mechanism for encoding and decoding. We propose a distributed data storage framework to increase data survivability in WSNs. The framework utilizes Decentralized Erasure Codes for Data Survivability (DEC-DS) which allow for determining the amount of redundancy required in both hardware and data to allow sensed data to survive failures in the network. To address the energy limitations, we show two approaches to implement the proposed solution in an energy efficient manner. The two approaches employ Random Linear Network Coding (RLNC) to exploit coding opportunities in order to save energy and in turn prolong network life. A routing based scheme, called DEC Encode-and-Forward (DEC-EaF), applies to networks with routing capability, while the second, DEC Encode-and-Disseminate (DEC-EaD), uses a variation of random walk to build the target code in a decentralized fashion. We also introduce a new decentralized approach to implement Luby Transform (LT)-Codes based DDSSs. The scheme is called Decentralized Robust Soliton Storage (DRSS) and it operates in a decentralized fashion and requires no coordination between sensor nodes. The schemes are tested through extensive simulations to evaluate their performance. We also compare the proposed schemes to similar schemes in the literature. The comparison considers energy efficiency as well as coding related aspects. Using the proposed schemes can greatly improve the reliability of WSNs especially under harsh working conditions. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2013-09-30 22:43:04.509

The emergence of the Internet of Things (IoT) has increased the demand for networked, resource-constrained devices tremendously. Many of the devices used for IoT applications are designed to be resource-constrained, as they typically must be small, inexpensive, and powered by batteries. In this dissertation, we consider a number of challenges pertaining to these constraints: system support for energy efficiency; flash-based storage systems; programming, testing, and debugging; and safe and secure application execution. The contributions of this dissertation are made through five research papers addressing these challenges. Firstly, to enhance the system support for energy-efficient storage in resource-constrained devices, we present the design, implementation, and evaluation of the Coffee file system and the Antelope DBMS. Coffee provides a sequential write throughput that is over 92% of the attainable flash driver throughput, and has a constant memory footprint for open files. Antelope is the first full-fledged relational DBMS for sensor networks, and it provides two novel indexing algorithms to enable fast and energy-efficient database queries. Secondly, we contribute a framework that extends the functionality and increases the performance of sensornet checkpointing, a debugging and testing technique. Furthermore, we evaluate how different data compression algorithms can be used to decrease the energy consumption and data dissemination time when reprogramming sensor networks. Lastly, we present Velox, a virtual machine for IoT applications. Velox can enforce application-specific resource policies. Through its policy framework and its support for high-level programming languages, Velox helps to secure IoT applications. Our experiments show that Velox monitors applications' resource usage and enforces policies with an energy overhead below 3%. The experimental systems research conducted in this dissertation has had a substantial impact both in the academic community and the open-source software community. Several of the produced software systems and components are included in Contiki, one of the premier open-source operating systems for the IoT and sensor networks, and they are being used both in research projects and commercial products.

Cette thèse porte sur les problèmes de déploiement des Réseaux de Capteurs sans Fil (RCsF). Elle suit trois directions principales : (1) le déploiement aléatoire, (2) le déploiement déterministe, et (3) l'auto-déploiement. En premier lieu, nous présentons une étude sur le placement aléatoire des capteurs dans les RCsF et nous élaborons une stratégie pratique de déploiement aléatoire. Ensuite, dans le cadre d'un déploiement déterministe, nous analysons le problème de gestion des imperfections liées à la collecte des données par les capteurs. Nous discutons les modèles de couverture et les algorithmes de placement existants et nous exploitons la théorie de l'évidence pour concevoir des stratégies de déploiement plus efficaces. Enfin, nous explorons les stratégies d'auto-déploiement existantes et nous élaborons un protocole en deux phases, léger et complet, pour assurer une couverture optimisée de la zone contrôlée en utilisant un RCsF mobile. Les résultats obtenus montrent l'efficacité des approches proposée qui ont été étudiées à la fois sur des données synthétiques que sur un test expérimental / This dissertation is an in-depth investigation of the Wireless Sensor Networks (WSNs) deployment problems that follows three general directions: (1) random deployment, (2) deterministic deployment, and (3) self-deployment. First, we present a survey and taxonomy of random node placement in WSNs and we devise a practical random deployment strategy. Second, we analyze the uncertainty-aware deterministic WSNs deployment problem where sensors may not always provide reliable information. We discuss sensor coverage models and placement algorithms found in the literature and we investigate the evidence theory to design better deployment strategies. We devise evidence-based sensor coverage models and we propose several polynomial-time uncertainty-aware deployment algorithms. Third, we explore the published self-deployment strategies and we devise a lightweight and comprehensive two-phase protocol, for ensuring area coverage employing a mobile WSN. Experimental results based on synthetic data sets, data traces collected in a real deployment, and an experimental test, show that the proposed approaches outperform the state-of-the-art deployment strategies

Dans le contexte des réseaux de capteurs sans fil, la technique de localisation ”range-free” est plus efficiente, par rapport au principe ”range-based”. Par conséquent, nous avons focalisé nos travaux de cette thèse sur les techniques ”range-free”. Afin de permettre à chaque noeud mobile ou normal de choisir son propre algorithme de localisation, nous avons proposé un mécanisme adapté en scindant les noeuds normaux en deux classes: les noeuds de la première classe ont au moins 3 ancres voisines, alors que les noeuds de la deuxième classe ont moins de trois ancres voisines. Pour les noeuds normaux de la classe 1, nous avons proposé un nouvel algorithme ”Mid-perpendicular”. Pour les noeuds normaux de la classe 2, nous avons proposé deux nouveaux algorithmes ”Checkout DV-hop” et ”Selective 3-Anchor DV-hop”.Pour simuler et évaluer la performance de nos trois nouveaux algorithmes dans le contexte protocolaire des réseaux, nous avons pris soin de proposer deux protocoles associés : ”DV-hopprotocol” et ”Classe-1 protocol”. Par la suite, nous avons combiné ces deux protocoles pour obtenir notre ”adaptive range-free localization protocol”. Basé sur nos protocoles, en utilisant le simulateur WSNet, nous avons simulé différents algorithmes ”range-free” dans le contexte des réseaux de capteurs conformes au standard IEEE 802.15.4. Les résultats ont été présentés et analysés en termes de précision de la localisation, charge du réseau, mobilité des noeuds, et synchronisation de ces derniers. / In the context of wireless sensor networks, the range-free localization technique is more costeffective than the range-base scheme. Therefore, in this thesis we focus on the range-free technique.In order to permit each normal node to choose its suitable localization algorithm, we proposed anadaptive mechanism to categorize normal nodes into two classes: the normal nodes having at least 3 neighbor anchors are class-1 nodes, while others are class-2 nodes. For class-1 normal nodes, we proposed a new algorithm named as Mid-perpendicular. For class-2 normal nodes, we proposed twoalgorithms Checkout DV-hop and Selective 3-Anchor DV-hop.In order to simulate and evaluate the performance of our three new algorithms, we proposed two protocols: DV-hop protocol and Class-1 protocol. Then we combined these two protocols into our adaptive range-free localization protocol. Based on our protocols, using the network simulator WSNet,we simulate the concerned range-free localization algorithms in the IEEE 802.15.4 wireless network.The comparative network simulation results are presented and analyzed in terms of localization accuracy, overhead, node mobility, and node synchronization

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering, 2016 / The design and implementation of network coding into a location based ad- dressing algorithm for VANET has been investigated. Theoretical analysis of the network coding algorithm has been done by using a simplified topology called the ladder topology. The theoretical models were shown to describe the way that network coding and standard location based addressing works over the VANET network. All tests were performed over simulation. Network coding was shown to improve performance by a factor of 1.5 to 2 times in both simulation and theoretical models. The theoretical models demonstrate a fundamental limit to how much network coding can improve performance by, and these were confirmed by the simulations. Network coding does have a susceptibility to interference, but the other benefits of the techniques are substantial despite this. Network coding demonstrates strong possibilities for future development for VANET protocols. The ladder topology is an important tool for future analysis. / GS