A Wireless Sensor Network is formed of several small devices encompassing the capability of sensing a physical characteristic and sending it hop by hop to a central node via low power and short range transceivers. The Sensor network lifetime strongly depends on the routing protocol in use. Routing protocol is responsible for forwarding the traffic and making routing decisions. If the routing decisions made are not intelligent, more re-transmissions will occur across the network which consumes limited resources of the wireless sensor network like energy, bandwidth and processing. Therefore a careful and extensive performance analysis is needed for the routing protocols in use by any wireless sensor network. In this study we investigate Objective Functions and the most influential parameters on Routing Protocol for Low power and Lossy Network (RPL) performance in Contiki (WSN OS) and then evaluate RPL performance in terms of Energy, Latency, Packet Delivery Ratio, Control overhead, and Convergence Time for the network. We have carried out extensive simulations yielding a detailed analysis of different RPL parameters with respect to the five performance metrics. The study provides an insight into the different RPL settings suitable for different application areas. Experimental results show ETX is a better objective, and that ContikiRPL provides very efficient network Convergence (14s), Control traffic overhead (1300 packets), Energy consumption (1.5% radio on time), Latency (0.5s), and Packet Delivery Ratio (98%) in our sample RPL simulation of one hour with 80 nodes, after careful configuration of DIO interval minimum/doublings, Radio duty cycling, and Frequency of application messages. / En Wireless Sensor Network består av flera små enheter som omfattar de förmåga avkänning en fysisk egenskap och skicka den hoppa med hopp till en centrala noden via låg effekt och kort sändtagare räckvidd. Det sensornätverk livslängd är starkt beroende av routingprotokoll som används. Routingprotokoll är ansvarar för att vidarebefordra trafik och göra routing beslut. Om dirigeringen beslut som fattas inte är intelligenta, kommer fler återsändningar förekomma på nätverk som förbrukar begränsade resurser trådlösa sensornätverk som energi, bandbredd och bearbetning. Därför är en noggrann och omfattande prestanda analys behövs för routingprotokoll används av alla trådlösa sensornätverk. I denna studie undersöker vi mål Funktioner och den mest inflytelserika parametrar Routing Protokoll för låg effekt och Förstörande nätverk (RPL) prestanda i Contiki (WSN OS) och sedan utvärdera RPL prestanda vad gäller av energi, fördröjning, Packet Delivery Ratio, kontroll overhead och konvergens Dags för nätverket. Vi har genomfört omfattande simuleringar som ger en detaljerad analys av olika RPL parametrar med avseende på de fem resultatstatistik. Studien ger en inblick i de olika RPL inställningar som är lämpliga för olika användningsområden. Experimentella resultat visar ETX är en bättre målsättning och att ContikiRPL ger mycket effektivt nätverk Konvergens (14s), Control trafik overhead (1300 paket), Energiförbrukning (1,5% radio i tid), Latens (0,5 s), och paket Leverans Ratio (98%) i vårt urval RPL simulering av en timme med 80 noder, efter noggrann konfiguration av DIO intervall minimum / dubbleringar, Radio plikt cykling, och frekvensen av ansökan meddelanden. / tocomputerscientist@gmail.com Mob: 0046760721720

The recent development of wired and wireless communication technologiesmake building automation the next battlefield of the Internet of Things. Multiplestandards have been drafted to accommodate the complex environmentand minimize the resource consumption of wireless sensor networks. This MasterThesis presents a thorough experimental evaluation with the latest Contikinetwork stack and TI CC2650 platform of network performance indicators,including signal coverage, round trip time, packet delivery ratio and powerconsumption. The Master Thesis also provides a comparison of the networkprotocols for low power operations, the existing operating systems for wirelesssensor networks, and the chips that operate on various network protocols. Theresults show that CC2650 is a promising competitor for future development inthe market of building automation.

Les réseaux de capteurs sont des réseaux particuliers composés d'objets contraints en ressources. Ils possèdent une faible puissance de calcul, une faible puissance de transmission, une faible bande passante, une mémoire de stockage limitée ainsi qu'une batterie à durée de vie limitée. Afin d'intégrer de tels réseaux dans l'internet des objects, de nouveaux protocoles ont été standardisés. Parmi ces protocoles, le protocole RPL (pour Routing Protocol for Low Power and Lossy Networks). Ce protocole est destiné a construire une topologie logique de routage appelée DODAG. Dans cette thèse, nous abordons l'aspect acheminement de données qui considère une topologie de routage arborescente. L'acheminement des données se fait donc de saut en saut d'un enfant à son parent (ou d'un parent à son enfant). Optimiser la construction du DODAG revient donc à construire un arbre couvrant selon une contrainte donnée. Un arbre couvrant est une structure communicante qui permet de maintenir un unique chemin entre toutes paires de noeuds tout en minimisant le nombre de liens de communication utilisés. De plus, nous considérons les contraintes des réseaux de capteurs telles qu'une batterie déchargée et la variabilité du lien radio comme des fautes transitoires. Ceci nous conduit par conséquent à construire une structure couvrante tolérante aux fautes transitoires. L'auto-stabilisation est une branche de l'algorithmique distribuée qui assure qu'à la suite d'une ou de plusieurs fautes transitoires, le système va retrouver de lui-même un comportement correcte au bout d'un temps fini. L'objectif de cette thèse est de proposer des algorithmes auto-stabilisants dédiés aux réseaux de capteurs. / Spanning Trees from theory to practiceSelf-Stabilizing algorithms and sensor networksAbstract : Sensor networks are composed of ressources constrained equipments. They have low computing power, low transmission power, low bandwidth, limited storage memory and limited battery life.In order to integrate such networks in the Internet of things, new protocols were standardized such as RPL protocol (for Routing Protocol for Low Power and Lossy Networks). This protocol is intended to build a logical routing topology called DODAG (for Destination Oriented Directed Acyclic Graph). In this thesis, we discuss the data routing aspect by considering a tree routing topology. Thus, the routing of data is hop by hop from a child to its parent (or from a parent to its child). Optimize the construction of the DODAG is therefore to build a spanning tree in a given constraint. A spanning tree is a connecting structure that maintains a unique path between all pairs of nodes while minimizing the number of used communication links. Furthermore, we consider the constraints of sensor networks, such as a dead battery and the variability of the radio link as transient faults. This leads us to build a covering structure tolerant to transient faults. The self-stabilization is a branch of distributed algorithms that ensures that following one or more transient faults, the system will find itself a correct behavior after a finite time.The objective of this thesis is to propose self-stabilizing algorithms dedicated to sensor networks. The contributions of this thesis are:In the first part of the thesis, we proposed a self-stabilizing algorithm for the construction of a minimum diameter spanning tree.This construction is natural when we want to minimize the communication delay between a root and all other network nodes. Our algorithm has several advantages. First, our algorithm is limited to memory occupation of O(log n) bits per node, reducing the previous result of an n factor while maintaining a polynomial convergence time. Then, our algorithm is the first algorithm for minimum diameter spanning tree that works as an unfair distribution demon. In other words, we make no restriction on the asynchronous network behavior. In the second part of the thesis, we are interested in the unstable topology built by RPL protocol (DODAG). Our solution is to place an additional constraint on the number of children a node can accept during the construction of the DODAG. This constraint has the effect of reducing the rate of parent change and consequently to improve the protocol performance in terms of packet delivery rate, delay of communication and power consumption. In addition, we implemented a mechanism to update the information of the downward routes in RPL. Furthermore, our solution has the advantage of not generating overhead because we use existing control messages provided by RPL to implement it. Finally, this contribution is twofold since we validated our solution both by simulations and experiments.

Le présent rapport fournit plusieurs extensions des protocoles de réseau ad hoc et leurs évaluations, qui permettent d'augmenter la performance, de dimensionner la taille des réseaux et d'intégrer les réseaux ad hoc dans l'Internet : Premièrement, ce rapport présente plusieurs outils de logiciel qui permettent d'étudier des protocoles de routage sans modifications, implémentés en Java, dans le simulator de réseaux NS2. Deuxièmement, ce rapport fournit une discussion architecturale des réseaux ad hoc, qui explique les problèmes de la configuration automatique des adresses IP (nommé autoconfiguration) des routeurs ad hoc. Ensuite, le rapport présente un modèle architectural pour des réseaux ad hoc qui est compatible avec l'Internet. Un protocole d'autoconfiguration, basé sur le modèle architectural proposé, est spécifié, et ses propriétés sont formellement vérifiées au moyen de Model Checking. Troisièmement, plusieurs extensions du protocole de routage des réseaux ad hoc OLSRv2 sont présentées : La performance du protocole est augmentée d'ordre de grandeur en utilisant un algorithme dynamique pour calculer les plus courts chemins. Une autre optimisation proposée est un framework basé sur SNMP pour gérer et contrôler des objets liés à la performance sur des routeurs tournant OLSRv2. Une extension d'OLSRv2 est présentée dans laquelle des paquets sont retransmis ultérieurement lorsque les destinations sont indisponibles temporairement, au lieu de les rejeter. Cette extension mène à un taux de remis considérablement plus élevé que OLSRv2 par défaut dans certains scenarios. Ce rapport présente alors une analyse des menaces de sécurité pour OLSRv2, suivie par la spécification d'un mécanisme de contrôle d'accès pour OLSRv2, qui empêche nombre de ces attaques. Quatrièmement, ce rapport explore le dimensionnement des réseaux de capteurs sans fil, et évalue un protocole de routage des réseaux de capteurs, nommé RPL, spécifié par l'IETF en 2011. En outre, étant donné que RPL ne contient pas de mécanisme de broadcast efficace, plusieurs mécanismes de broadcast optimisés dans RPL sont présentés et comparés.

Le paradigme de l'Internet des Objets (IoT) envisage d'enrichir l'Internet actuel avec un grand nombre de dispositifs intelligents communicants. Les réseaux de capteurs sans fil (RCF) exploitent des appareils avec des ressources énergétiques limitées équipés de capteurs afin de récupérer en temps réel des mesures (comme la température, la radioactivité, ou le CO2). Les réseaux de capteurs sont particulièrement pertinents pour la surveillance, la télémétrie ou la prévention des catastrophes naturelles. Cependant, ce type de réseau pose des problèmes majeurs tels que l'utilisation efficace de ressources énergétiques limitées, la prise en charge transparente de nœuds défaillants, sans intervention humaine. L'Internet des Objets ne permettra d'intégrer des réseaux de capteurs autonomes que si les protocoles sont standards et passent à l'échelle. Les contributions de cette thèse sont les suivantes : * nous avons caractérisé expérimentalement un réseau radio multisaut en exploitant statistiquement un grand volume de mesures provenant d'une plate-forme expérimentale opérée par Orange. Notre analyse porte sur la caractérisation d'un lien et de sa qualité ainsi que de la dynamique du réseau. * nous avons proposé de modifier le standard IEEE 802.15.4 afin qu'il puisse cohabiter efficacement avec le protocole de routage actuellement standard de l'Internet des Objets, RPL. En particulier, nous proposons d'exploiter une structure de graphe dirigé acyclique afin d'exploiter une topologie maillée et pallier à la déficience éventuelle d'un nœud. Nous avons proposé également des algorithmes simples d'ordonnancement distribué des supertrames adaptés à cette topologie. * le choix des pères au niveau MAC dans une structure de graphe dirigé acyclique est déterminant dans la qualité des routes possibles dans la couche réseau. Nous avons ainsi proposé un algorithme de choix des pères basé sur plusieurs métriques. Nous aboutissons à une structure permettant d'équilibrer la charge, limitant les points de congestion, utilisant des liens radio de bonne qualité, limitant la congestion au niveau MAC. * nous avons enfin présenté des mécanismes permettant d'offrir une qualité de service dans une pile s'appuyant sur IEEE 802.15.4 et RPL. Notre extension de routage opportuniste et multi-chemin contribue à améliorer la livraison des paquets avant une date limite, tout en minimisant le surcout et la consommation d'énergie par rapport à la version originale de RPL.

The Internet is one of the greatest innovations ever created by mankind, and it is a technical trend that has moved into industries to facilitate automation, supervision and management in the form of IoT devices. These devices are designed to be extremely lightweight and operate in low-power and lossy networks, and therefore run a low duty cycle and CPU-clock frequency to reserve battery life. Fog nodes are located on site to minimize network delay and provide centralized processing to handle data from hundreds of connected devices in wireless sensor networks. This is the future of industrial automation. Our goal is to show the functionality of an industrial IoT network within the scope of Fog computing by implementing a closed-loop control system in Cooja. Performance evaluations considered network reliability in terms of packet delivery ratio and timeliness. We assume that wireless IoT devices are running RPL routing (one of the most common standard routing protocols for IoT applications). We implement a mobility controller at the Fog-server in order to collect measurements made by the Fog nodes and send commands to IoT devices. In this thesis work, we assume that the commands are related to the mobility pattern of mobile node (e.g. AGVs in industrial automation) in order to avoid collision. From the simulation results we can conclude that sampling rates and node density have a greater impact on performance compared to payload size. We cannot be sure that our results reflect what a real-world evaluation would imply as we are running an emulation software, even though it has a very realistic physical layer. We do however believe that with substantial testing and improvements to both Cooja and our implementation, an accurate representation can be accomplished and algorithms in Cooja can be moved to real-world implementations.

Magister Artium - MA / This research paper investigates the extent to which the Recognition of Prior Learning (RPL) is implemented in the Real Estate industry within the Johannesburg Metropolitan area. The Real Estate industry is an ideal industry to assess the prior learning of real estate agents since there is no doubt that such a workplace has been recognized as an effective and efficient learning environment which allows workers to take part in an ever-changing work environment (Le Clus, 2011). Despite the availability of resources from different entities, i.e. the Services Sector Education and Training Authority (SETA), RPL centres, Umalusi, the Department of Higher Education and Training (DHET), the Estate Agency Affairs Board (EAAB), and so on (OECD, 2010) there seems to be incompatibility between the existing policy and the implementation of such policy in the Real Estate industry. Hence, to paraphrase a common theme within the literature (Cameron and Miller, 2004) there is a gap between the promise and rhetoric of RPL and the actual reality, and a disjuncture between policy formulation and implementation of RPL. Also, most research (Cameron and Miller, 2004) reveals that RPL has neither fulfilled its promised potential of encouraging the previously disadvantaged groups to access formal education and training, nor achieved its goal as a mechanism for social inclusion. The two primary research questions for this research paper were: Why are potential RPL candidates not taking the RPL route to obtain their certification? What are the barriers that obstruct efficient RPL implementation within the Real Estate industry? The research design was exploratory within a qualitative framework employing focus group interviewing, individual interviewing and the distribution of questionnaires that consisted of open-ended questions. The research sample comprised nineteen participants that included eight estate agents, four principals, five RPL Centers‟ representatives, one representative from the Services SETA and one representative from the Estate Agency Affairs Board. Master of Education in Adult Education and Global Change - Dissertation [University of the Western Cape] The research findings show that there are serious issues with the implementation current RPL policy within the real estate industry. Many scholars (Colardyn and Bjørna°vold, 2004; Bjørna°vold, 2000) indicate that RPL comes with its challenges, for instance that of the role it can play and the extent to which it can address the twin goals of increasing educational level of participation and employment rates. RPL also takes much time, as Anderson, Fejes and Ahn (2004) stress, to transform non-formal and informal learning into more or less formal learning that is ratified in the form of officially acknowledged certificates. Elements such as lack of or insufficient learner support by advisors and language barriers, have contributed significantly to the dropping out of most candidates. The strength of RPL is that unaccredited knowledge and skills can be brought into the open for everyone to see and, in a sense, come into use (Berglund and Anderson, 2012). This was made evident by the candidates who made it through RPL. RPL has also contributed to social equity and redress by admitting candidates as recognised agents and principals who previously were about to be excluded from the industry due to lack of recognised qualifications.

The policy and practice of RPL (Recognition of Prior Learning) remains a contested area in the higher education sector. While a growing body of research on RPL has become available, little is known about the quality assurance dimensions of this policy and its current expression in higher education practice. Accordingly, this study seeks to provide a comprehensive and detailed portrait of the manner in which RPL is implemented in the Faculty of Education at the University of Pretoria. The central question is does the RPL system that is in place at this institution meet national and international requirements for quality and quality assurance? If not, what are the reasons and how can the faculty improve its RPL practice? The research sub-questions addressed are the following: <ul> <li> What is the quality of the inputs used to design the RPL that is in place in the Faculty of Education at the University of Pretoria?</li> <li> How does the Faculty of Education at the University of Pretoria assess RPL candidates for their prior learning? </li> <li> What is the effect of the output of the RPL system on client satisfaction?</li></ul> A mixed methods research design was used for this study. A single Faculty (Education) was selected as the data collection site, to reveal the deeper and nuanced impact of the process of implementation of the RPL programme. A semi-structured interview schedule administered to the senior managers of the faculty was to elicit information on how the RPL system was conceptualised and designed. This process included the Dean (Faculty of Education); Head of Department (Curriculum Studies); Head of Department (Educational Management, Law and Policy Studies); Director (Centre for Evaluation and Assessment) and the Director (Centre for Joint Science, Mathematics and Technology Education). To determine whether there is a link between what the Quality Assurance Unit of the university promotes and application of such principles and procedures at service delivery level, an interview with the Director of the QA Unit was done. Other interviews involved students (undergraduates and postgraduates); the non-academic staff and lecturers within all the departments of the faculty, to determine whether they knew or were aware of RPL related activities in the faculty. An observation tool was constructed to examine the quality of the assessment process, which involved RPL learners, assessors, evidence facilitators, verifiers, moderators and RPL administrators. A questionnaire was administered to RPL learners involved in the assessment process to determine their satisfaction with the output of the RPL programme. Lecturers who participated in the RPL assessment process were interviewed to determine their experiences. Finally, an observational checklist was used to determine quality indicators at macro (administrative) and micro (academic) levels. The data was analysed using pattern matching, discrepancy, content and interpretational analyses methods. The research findings presented are in the form of a “thick” narrative on the quality of RPL implementation, that is, what the faculty should do to improve or strengthen the current system, and a portrayal of how the RPL programme truly operates. The findings indicate that a relatively good system of RPL provisioning is in place in the Faculty of Education, with a few areas of concern (weaknesses). The major problem is that this system is not benefiting the majority of people it was intended for. The system is “selective” and “exclusionary” in nature. There are clear procedures and processes for RPL assessment, which are adhered to strictly by faculty assessors. The RPL system that is currently in place is satisfactory to those who were assessed for prior learning during the period 2003-2006 and unsatisfactory at the level of the lecturers who participated in the assessment process. Most of them indicated that RPL is an add-on activity to their workloads, with very little incentives from management. To those who were not part of the assessment process, but were assumed to have received information from the faculty, the findings indicated that they knew very little about RPL and how it is being assessed in the faculty. From the client’s perspective, most (eighty four percent) said if they knew how this system operates in the faculty, they would want to be assessed for their prior learning. An extensive examination of the RPL practice in the Faculty of Education gave useful insights on the quality of RPL provisioning. Future research needs to concentrate on evaluations on how RPL is implemented in the other faculties of the university. Second to this, is to begin to provide answers as to what causes full-scale implementation of RPL problematic in the higher education sector, to provide empirical data to policy makers for decision-making purposes. Thirdly, to provide solutions towards the sustainability of the RPL system in the higher education sector, there is a need to do studies on the cost-effectiveness of RPL implementation. / Thesis (PhD (Assessment and Quality Assurance in Education and Training))--University of Pretoria, 2007. / Curriculum Studies / PhD / unrestricted

No description available.

Philosophiae Doctor - PhD / This study begins with an ethnographic self-study which allows for a reflection on traditional learning experiences. This study is located in the context of the initial development of dental health professionals within those higher education institutions that endeavour to provide education and training in a rapidly changing context. This context is characterised by the simultaneous need to address the blurring of boundaries and the dichotomies that exist such as the first world and the third world, the developed and the less developed world, the rich and the poor, health and wealth, the private and the public sectors, the formal and the informal sectors, the advantaged and the disadvantaged, the privileged and the underprivileged. The definitions, concepts, theories and principles around curricula and professional development are examined in an effort to extend into discoveries of educational research usually beyond the purview of dental health practitioners, policy makers or higher education specialists involved in training these dental health practitioners. It poses key questions regarding the nature of professional competences within dental health science undergraduate studies and how the curricula are organised around these perceptions of competence. Investigative tools include participant observation, interviews and questionnaires which have included both education deliverers - the teaching staff - and education consumers - the students. The areas of access by students to programmes (input), activities whilst in the programmes (throughput) and their competences at the exit end of the programme (output) are examined. It was found that institutions and programmes are paradoxically positioned declaring missions to be globally competitive and internationally recognised and at the same time wanting to reach out to the population who are disadvantaged and who form a majority. Whilst the needs of the wider community is for basic dental services and primary health care, the resources appear to be geared for producing technologically-superior professionals who will cater for a largely urban and middle class populations. The resources available, particularly human resources, for this training, are going through a critical shortage. Simultaneously demands are being made to challenge the epistemological rationale of the curriculum practice of the training sites at both universities and technikons (now known as universities of technology). These findings reveal that the SAQA demands and the proposed transformation of higher education provided an impetus for schools and departments within universities and technikons and their institutes to look at educational concepts and to transform curricula. This shift was found to be hampered by a variety of causes which included territorial protection, lack of a deep understanding of the education and training concepts and lack of human, physical and financial resources. It was also found that traditional designs of programmes are locked into tribal boundaries which restrict movement beyond these. The boundaries are ring-fenced by historical legacies and practices which confine programmes within these borders and continue to cement the fragmented development of dental health science professionals. The education and training of the different dental health science occupational categories are fragmented between institutes, within institutes and with three separate professional regulating bodies and, seemingly, disjointed functioning national and provincial departments of health and education. This (education and training) is found to be dominated by the traditional mould of teaching, learning and assessment with pockets of change in some schools and departments. Teaching units in the form of subjects, which operate as discrete units and remain entrenched by the habituations of subjects and departments within schools, restricts movement in the competence-based direction. The framework offered by this thesis sets broader and more fluid principles and guidelines which embody the notion of knowledge, skills, attitudes and values and which course designers and educators can utilise so that renewed ways can emerge for their programmes. This allows for a cross over into each other's territories (regulatory, institutional and the health and educational services) that will allow for courses to be designed more holistically and rationally with appropriate transformatory potential.