Context: Wireless Sensor Networks (WSN) are applied to collect information by distributed sensor nodes (anchors) that are usually in fixed positions. Localization (estimating the location of objects) of moving sensors, devices or people which recognizes the location’s information of a moving object is one of the essential WSN services and main requirement. To find the location of a moving object, some of algorithms are based on RSSI (Received Signal Strength Indication). Since very accurate localization is not always feasible (cost, complexity and energy issues) requirement, RSSI-based method is a solution. This method has two specific features: it does not require extra hardware (cost and energy aspects) and theoretically RSSI is a function of distance. Objectives: In this thesis firstly, we develop an RSSI-based localization algorithm (server side application) to find the position of a moving object (target node) in different situations. These situations are defined in different experiments so that we observe and compare the results (finding accurate positioning). Secondly, since RSSI characteristic is highly related to the environment that an experiment is done in (moving, obstacles, temperature, humidity …) the importance and contribution of “environmental condition” in the empirical papers is studied. Methods: The first method which is a common LR (Literature Review) is carried out to find out general information about localization algorithms in (WSN) with focus on the RSSI-based method. This LR is based on papers and literature that are prepared by the collaborating company, the supervisor and also ad-hoc search in scientific IEEE database. By this method as well as relevant information, theoretical algorithm (mathematical function) and different effective parameters of the RSSI-based algorithm are defined. The second method is experimentation that is based on development of the mentioned algorithm (since experiment is usually performed in development, evaluation and problem solving research). Now, because we want to compare and evaluate results of the experiments with respect to environmental condition effect, the third method starts. The third method is SMS (Systematic mapping Study) that essentially focuses on the contribution of “environmental condition” effect in the empirical papers. Results: The results of 30 experiments and their analyses show a highly correlation between the RSSI values and environmental conditions. Also, the results of the experiments indicate that a direct signal path between a target node and anchors can improve the localization’s accuracy. Finally, the experiments’ results present that the target node’s antenna type has a clear effect on the RSSI values and in consequence distance measurement error. Our findings in the mapping study reveal that although there are a lot of studies about accuracy requirement in the context of the RSSI-based localization, there is a lack of research on the other localization requirements such as performance, reliability and stability. Also, there are a few studies which considered the RSSI localization in a real world condition. Conclusion: This thesis studies various localization methods and techniques in WSNs. Then, the thesis focuses on the RSSI-based localization by implementing one algorithm and analyzing the experiments’ results. In our experiments, we mostly focus on environmental parameters that affect localization’s accuracy. Moreover, we indicate some areas of research in this context which need more studies.

Wireless Sensor Networks (WSNs), in addition to enabling monitoring solutions for numerous new applications areas, have gained huge popularity as a cost-effective, dynamically scalable, easy to deploy and maintainable alternatives to conventional infrastructure-based monitoring solutions. A WSN consists of spatially distributed autonomous wireless sensor nodes that measure desired physical phenomena and operate in a collaborative manner to relay the acquired information wirelessly to a central location. A wireless sensor node, integrating the required resources to enable infrastructure-less distributed monitoring, is constrained by its size, cost and energy. In order to address these constraints, a typical wireless sensor node is designed based on low-power and low-cost modules that in turn provide limited communication and processing performances. Data and computation intensive wireless monitoring applications, on the other hand, not only demand higher communication bandwidth and computational performance but also require practically feasible operational lifetimes so as to reduce the maintenance cost associated with the replacement of batteries. In relation to the communication and processing requirements of such applications and the constraints associated with a typical wireless sensor node, this thesis explores energy efficient wireless sensor node architecture that enables realization of data and computation intensive applications. Architectures enabling raw data transmission and in-sensor processing with various technological alternatives are explored. The potential architectural alternatives are evaluated both analytically and quantitatively with regards to different design parameters, in particular, the performance and the energy consumption. For quantitative evaluation purposes, the experiments are conducted on vibration and image-based industrial condition monitoring applications that are not only data and computation intensive but also are of practical importance. Regarding the choice of an appropriate wireless technology in an architecture enabling raw data transmission, standard based communication technologies including infrared, mobile broadband, WiMax, LAN, Bluetooth, and ZigBee are investigated. With regards to in-sensor processing, different architectures comprising of sequential processors and FPGAs are realized to evaluate different design parameters, especially the performance and energy efficiency. Afterwards, the architectures enabling raw data transmission only and those involving in-sensor processing are evaluated so as to find an energy efficient solution. The results of this investigation show that in-sensor processing architecture, comprising of an FPGA for computation purposes, is more energy efficient when compared with other alternatives in relation to the data and computation intensive applications. Based on the results obtained and the experiences learned in the architectural evaluation study, an FPGA-based high-performance wireless sensor platform, the SENTIOF, is designed and developed. In addition to performance, the SETNIOF is designed to enable dynamic optimization of energy consumption. This includes enabling integrated modules to be completely switched-off and providing a fast configuration support to the FPGA.  In order to validate the results of the evaluation studies, and to assess the performance and energy consumption of real implementations, both the vibration and image-based industrial monitoring applications are realized using the SENTIOF. In terms of computational performance for both of these applications, the real-time processing goals are achieved. For example, in the case of vibration-based monitoring, real-time processing performance for tri-axes (horizontal, vertical and axial) vibration data are achieved for sampling rates of more than 100 kHz. With regards to energy consumption, based on the measured power consumption that also includes the power consumed during the FPGA’s configuration process, the operational lifetimes are estimated using a single cell battery (similar to an AA battery in terms of shape and size) with a typical capacity of 2600 mA. In the case of vibration-based condition monitoring, an operational lifetime of more than two years can be achieved for duty-cycle interval of 10 minutes or more. The achievable operational lifetime of image-based monitoring is more than 3 years for a duty-cycle interval of 5 minutes or more.

Vu les perspectives qu'ils offrent, les réseaux de capteur sans fil (RCSF) ont perçu un grand engouement de la part de la communauté de recherche ces dernières années. Les RCSF couvrent une large gamme d'applications variant du contrôle d'environnement, le pistage de cible aux applications de santé. Les RCSFs sont souvent déployés aléatoirement. Ce dispersement des capteurs nécessite que les protocoles de transmission utilisés soient résistants aux conditions environnementales (fortes chaleurs ou pluies par exemple) et aux limitations de ressources des nœuds capteurs. En effet, la perte de plusieurs nœuds capteurs peut engendrer la perte de communication entre les différentes entités. Ces limitations peuvent causer la perte des paquets transmis ce qui entrave l'activité du réseau. Par conséquent, il est important d'assurer la fiabilité des transmissions de données dans les RCSF d'autant plus pour les applications critiques comme la détection d'incendies. Dans cette thèse, nous proposons une solution complète de transmission de données dans les RCSF répondant aux exigences et contraintes de ce type de réseau. Dans un premier temps, nous étudions les contraintes et les challenges liés à la fiabilisation des transmissions dans les RCSFs et nous examinons les travaux proposés dans la littérature. Suite à cette étude nous proposons COMN2, une approche distribuée et scalable permettant de faire face à la défaillance des nœuds. Ensuite, nous proposons un mécanisme de contrôle d'erreur minimisant la perte de paquets et proposant un routage adaptatif en fonction de la qualité du lien. Cette solution est basée sur des acquittements implicites (overhearing) pour la détection des pertes des paquets. Nous proposons ensuite ARRP une variante de AJIA combinant les avantages des retransmissions, de la collaboration des nœuds et des FEC. Enfin, nous simulons ces différentes solutions et vérifions leurs performances par rapport à leurs concurrents de l'état de l'art. / Over the past decades, we have witnessed a proliferation of potential application domainsfor wireless sensor networks (WSN). A comprehensive number of new services such asenvironment monitoring, target tracking, military surveillance and healthcare applicationshave arisen. These networked sensors are usually deployed randomly and left unattendedto perform their mission properly and efficiently. Meanwhile, sensors have to operate ina constrained environment with functional and operational challenges mainly related toresource limitations (energy supply, scarce computational abilities...) and to the noisyreal world of deployment. This harsh environment can cause packet loss or node failurewhich hamper the network activity. Thus, continuous delivery of data requires reliabledata transmission and adaptability to the dynamic environment. Ensuring network reliabilityis consequently a key concern in WSNs and it is even more important in emergencyapplication such disaster management application where reliable data delivery is the keysuccess factor. The main objective of this thesis is to design a reliable end to end solution for data transmission fulfilling the requirements of the constrained WSNs. We tackle two design issues namely recovery from node failure and packet losses and propose solutions to enhance the network reliability. We start by studying WSNs features with a focus on technical challenges and techniques of reliability in order to identify the open issues. Based on this study, we propose a scalable and distributed approach for network recovery from nodefailures in WSNs called CoMN2. Then, we present a lightweight mechanism for packetloss recovery and route quality awareness in WSNs called AJIA. This protocol exploitsthe overhearing feature characterizing the wireless channels as an implicit acknowledgment(ACK) mechanism. In addition, the protocol allows for an adaptive selection of therouting path by achieving required retransmissions on the most reliable link. We provethat AJIA outperforms its competitor AODV in term of delivery ratio in different channelconditions. Thereafter, we present ARRP, a variant of AJIA, combining the strengthsof retransmissions, node collaboration and Forward Error Correction (FEC) in order toprovide a reliable packet loss recovery scheme. We verify the efficiency of ARRP throughextensive simulations which proved its high reliability in comparison to its competitor.

The concept of wireless sensor network (WSN) is where tiny devices (sensor nodes), positioned fairly close to each other, are used for sensing and gathering data from its environment and exchange information through wireless connections between these nodes (e.g. sensor nodes distributed through out a bridge for monitoring the mechanical stress level of the bridge continuously). In order to easily deploy a relatively large quantity of sensor nodes, the sensor nodes are typically designed for low price and small size, thereby causing them to have very limited resources available (e.g. energy, processing power). Over the years, different security (cryptographic) primitives have been proposed and refined aiming at utilizing modern processor’s power e.g. 32-bit or 64-bit operation, architecture such as MMX (Multi Media Extension) and etc. In other words, security primitives have targeted at high-end systems (e.g. desktop or server) in software implementations. Some hardware-oriented security primitives have also been proposed. However, most of them have been designed aiming only at large message and high speed hashing, with no power consumption or other resources (such as memory space) taken into considerations. As a result, security mechanisms for ultra-low power (<500µW) devices such as the wireless sensor nodes must be carefully selected or designed with their limited resources in mind. The objective of this project is to provide implementations of security primitives (i.e. encryption and authentication) suitable to the WSN environment, where resources are extremely limited. The goal of the project is to provide an efficient building block on which the design of WSN secure routing protocols can be based on, so it can relieve the protocol designers from having to design everything from scratch. This project has provided three main contributions to the WSN field.  Provides analysis of different tradeoffs between cryptographic security strength and performances, which then provide security primitives suitable for the needs in a WSN environment. Security primitives form the link layer security and act as building blocks for higher layer protocols i.e. secure routing protocol.  Implements and optimizes several security primitives in a low-power microcontroller (TI MSP430F1232) with very limited resources (256 bytes RAM, 8KB flash program memory). The different security primitives are compared according to the number of CPU cycles required per byte processed, specific architectures required (e.g. multiplier, large bit shift) and resources (RAM, ROM/flash) required. These comparisons assist in the evaluation of its corresponding energy consumption, and thus the applicability to wireless sensor nodes.  Apart from investigating security primitives, research on various security protocols designed for WSN have also been conducted in order to optimize the security primitives for the security protocols design trend. Further, a new link layer security protocol using optimized security primitives is also proposed. This new protocol shows an improvement over the existing link layer security protocols. Security primitives with confidentiality and authenticity functions are implemented in the TinyMote sensor nodes from the Technical University of Vienna in a wireless sensor network. This is to demonstrate the practicality of the designs of this thesis in a real-world WSN environment. This research has achieved ultra-low power security primitives in wireless sensor network with average power consumption less than 3.5 µW (at 2 second packet transmission interval) and 700 nW (at 5 second packet transmission interval). The proposed link layer security protocol has also shown improvements over existing protocols in both security and power consumption. / Dissertation (MEng (Computer Engineering))--University of Pretoria, 2008. / Electrical, Electronic and Computer Engineering / unrestricted

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Interactive digital art installations are fundamentally enabled by hardware and software. Through a combination of these elements an interactive experience is con- structed. The first half of this thesis discusses the technical complexity associated with design and implementation of digital interactive installation. A system, dreamIO, is proposed for mediating this complexity through providing wireless building blocks for creating interactive installations. The technical details–both hardware and software– of this system are outlined. Measurements of the system are presented followed by analysis and discussion of the real world impact of this data. Finally, a discussion of future improvements is presented. The second half of this thesis examines an example interactive installation, Trans- code, which uses the proposed system as the building block for the piece. The piece is presented as evidence for the value of the proposed system and as a work of art in it’s own right. The use of the dreamIO system is detailed followed by a discussion of the interactivity and aesthetic form of the work. The purposes of these specific design choices are then presented. Finally, the work is analyzed through a combination of Relational Aesthetics and Cybernetics. / Graduate

Neste trabalho foi realizado um estudo sobre o uso e influências do efeito small world, ou seis graus de separação, no roteamento de redes de sensores sem fio (RSSFs). Para esse objetivo, foram analisadas as características das RSSFs que influenciam no roteamento e os diferentes tipos de protocolos. Além disso, foram estudadas as características do efeito small world e suas propriedades, de um modo geral, em redes de larga escala e com alta densidade de nós, incluindo o modelo de small world para o estudo de redes ad hoc. Realizou-se um breve estudo sobre redes overlay, redes lógicas criadas sobre a rede física com o propósito de melhorar suas qualidades e seu desempenho. A conclusão neste trabalho é que small worlds pode ser empregado para melhorar o funcionamento de protocolos de roteamento em RSSFs. / In this work, has made an study about the use and influences of the small world effect, or six degrees of separation, in routing of wireless sensors network (WSNs). For this objective, was analyzed the characteristics of WSNs that influence in the routing and the different types of protocols. Moreover, was studied the characteristics of small world effect and it properties, generically, in large scale networks with a high node density, including the small world model for the study of ad hoc networks. Was accomplished a brief study about overlay networks, logical network created over physical network with the purpose of improve qualities and performance. The conclusion in this work is that small worlds can be applied to improve the operation of WSNs routing protocols.

The purpose of this thesis is to investigate the impact on latency and power consumption of certain usage environments for selected communication protocols that have been designed for resource constrained usage. The research questions in this thesis is based on the findings in Lindén report “A latency comparison of IoT protocols in MES” and seeks to answer the following: ”How does MQTT impact the latency and power consumption on a constrained device?” ”How does CoAP impact the latency and power consumption on a constrained device?” ”How does usage environment influence the latency for MQTT and CoAP?” This thesis only seeks to explore concepts and usage environments related to wireless sensor networks, internet of things and constrained devices. The experiments have been carried out on a ESP WROOM 32 Core board V2 applying MQTT and CoAP as the communication protocols. The overall research method used in this thesis is the experimental research design proposed by Wohlin et al. Experiments have been created to support or disprove hypotheses which are formulated to answer the research questions. The experiments were conducted in test environments, which mimic a real-life wireless sensor network environment. The process is thoroughly recorded to further increase the traceability of this thesis. This decision was made due to a comment Boyle et al. made about the problems with real-life experiments about the wireless communication-based research domain. Where Boyle et al. states that there is “insufficient knowledge” available for the research community. The MQTT related latency experiments showed that QoS level 0 had the lowest latency of all the QoS levels. However, the results also showed that QoS 1 and 2 almost had an identical latency. The CoAP related latency experiments did not indicate any obvious trends. The results from the power consumption related experiments were inconclusive since the data was incomplete. The usage environment related experiments yielded conclusive results. The data showed that there was a small variation in the latency impact across the various usage environments. Furthermore, the data suggest that CoAP and MQTT had lower latencies in a high signal strength environment compared to a lower signal strength environment. However, it is not clear if there were any unknown factors influencing the results.

This diploma thesis describes the standard IEEE802.15.4 and Zigbee for wireless sensor networks. These norms are described in detail in the first two chapters. The main priority of the wireless sensor networks is to minimize the power of the devices and the price while maximizing the reliability of the data transfer. Minimum consumption is provided by the significantly lowered complexity in comparison to the standard wireless networks. Further, the design of the concept of the complex and universal hardware platform focused on intelligent building is described. Software implementation of those norms is described in the chapters five and six. Finally, comparison of the designed hardware platform and the other commercial platforms is described in the last chapter.

The aim of this work is to become familiar with simulation environment Network Simulator 2, study the problems of sensor networks and their support in the simulator and implement the selected protocol and verify its funcitonality in a practical simulation.