The presence of computer technologies in our daily life is growing by leaps and bounds. One of the recent trends is the use of mobile technologies and cloud services for supporting everyday tasks and the sharing of information between users. The field of education is not absent from these developments and many organizations are adopting Information and Communication Technologies (ICT) in various ways for supporting teaching and learning. The field of Mobile Learning (M-Learning) offers new opportunities for carrying out collaborative educational activities in a variety of settings and situations. The use of mobile technologies for enhancing collaboration provides new opportunities but at the same time new challenges emerge. One of those challenges is discussed in this thesis and it con- cerns with uncertainties related to the dynamic aspects that characterized outdoor M-Learning activities. The existence of these uncertainties force software developers to make assumptions in their developments. However, these uncertainties are the cause of risks that may affect the required outcomes for M-Learning activities. Mitigations mechanisms can be developed and included to reduce the risks’ impact during the different phases of development. However, uncertainties which are present at runtime require adaptation mechanisms to mitigate the resulting risks. This thesis analyzes the current state of the art in self-adaptation in Technology-Enhanced Learning (TEL) and M-Learning. The results of an extensive literature survey in the field and the outcomes of the Geometry Mobile (GEM) research project are reported. A list of uncertainties in collaborative M-Learning activities and the associated risks that threaten the critical QoS outcomes for collaboration are identified and discussed. A detailed elaboration addressing mitigation mechanisms to cope with these problems is elaborated and presented. The results of these efforts provide valuable insights and the basis towards the design of a multi-agent self-adaptive architecture for multiple concerns that is illustrated with a prototype implementation. The proposed conceptual architecture is an initial cornerstone towards the creation of a decentralized distributed self-adaptive system for multiple concerns to guarantee collaboration in M-Learning.

When designing networks intended to carry real-time media that is critical to arrive several aspects must be considered. For instance, the network must have redundant connectivity, should this traffic (and if so, how) be prioritized in networks where other traffic also travel, which technology is best in the given situation etc. This report will describe technologies that can solve these problems after which some of some of them will be tested in laborations to see how well they measure up in a given problem. The report establishes that in a self-governed LAN link aggregation in collaboration with Virtual Router Redundancy Protocol is a solid solution for providing redundancy with fast reconvergence. On WAN-connections and other shared networks Quality of Service rules should be implemented and in the case of Internet Service Providers a Service Level Agreement should be established.

In future mobile networks service quality might be poor. A new measure is needed to be able to assess services in terms of their effectiveness and usefulness despite their lacking visual appeal. Cognitive Quality of Service is a way to measure the effectiveness in use of a networked service. This thesis introduces Cognitive Quality of Service and puts it in relation to other ways to measure quality in streaming media. Through four studies the concept is used to improve multicast performance in a WLAN, to assess the effectiveness of simple animations compared to video, to build an application that fuses video and animations and to assess the differences between various levels of streaming video quality. Guidelines on how to measure Cognitive Quality of Service are introduced based on a review of available literature and later analyzed in light of the studies presented in the thesis. It turns out that the guidelines are sound and should be used as a basis for assessing Cognitive Quality of Service. Finally, the usefullness of Cognitive Quality of Service is analyzed. It turns out that it is especially useful when comparing different media, e.g. animations and video. In the video only case even bit-rate might be a useful predictor of subjective quality. / I framtiden kommer användare att titta på videosekvenser i trådlösa apparater, exempelvis mobiltelefoner. På grund av tekniska faktorer som störningar och på grund av kostnaden för det kommer den kvalitet som de erhåller inte att vara jämförbar med till exempel den kvalitet som kan erhållas när man tittar på tv. Trots det kan man anta att sådan video kan vara intressant och upplysande. I avhandlingen introduceras och används begreppet Cognitive Quality of Service (CQoS) - kognitiv servicekvalitet. Begreppet definieras av att den överföring som ger den bästa förståelsen och känslomässiga reaktionen också har bäst CQoS. För att mäta CQoS bör man följa vissa riktlinjer, särskilt som det är svårt att mäta förståelse i samband med att man tittar på video. Författaren har tillsammans med medarbetare tittat på hur man kan förbättra förhållandena för själva radioöverföringen (studie I). Genom en algoritm som ger multicast-paket bättre skydd mot kollisioner visas att man kan erhålla förbättrad överföringskapacitet för strömmande video i ett trådlöst nätverk. Animeringar är ett alternativ till video som kräver låg bandbredd. I ett experiment har man undersökt hur väl animeringar står sig mot video av olika kvalitet när det gäller att upplysa användaren och ge en bra upplevelse (studie II). Det visade sig att animeringar var bättre för förståelsen medan video gav en bättre känslomässig upplevelse. Vanare åskådare föredrog videon medan ovanare åskådare föredrog animeringarna. Frågan som ställdes var då hur man kunde kombinera respektive mediums fördelar för att få en så bra blandning som möjligt. Å ena sidan var animeringarna billiga och lätta att förstå medan videon var dyrare och mer intressant. Ett prototypgränssnitt skapades. Där kunde användaren själv välja vilken mix mellan de två alternativen som skulle visas (studie III). Det visade sig att försökspanelen föredrog video och dessutom ville ha mer information om spelare och match. Trots animationernas förträfflighet kan man anta att det ändå är video som kommer att dominera i framtiden. En sista studie genomfördes för att se om man kunde finna liknande resultat vid olika kvalitetsgrader i video som man tidigare hade funnit mellan video och animeringar (studie IV). Det visade sig att så länge man höll sig till ett format var sambanden enklare. Mer var helt enkelt bättre upp till en viss gräns där det inte tillförde mer att öka överföringsresurserna för videon. Sammanfattningsvis visar studierna att CQoS kan ge värdefull designkunskap. I synnerhet när man jämför olika presentationsformer som i det här fallet animeringar och video. Nästa steg blir att gå vidare med att applicera CQoS i tvåvägskommunikation, särskilt i Conversational Multimedia (CMM)– ungefär bildtelefoni – där det är särskilt goda möjligheter att sammanställa en för omständigheterna anpassad mediamix.

Cette thèse est consacrée à l'évaluation de la fiabilité d’une caravane de véhicules intelligents avec les principaux objectifs de fournir une méthode pour évaluer et améliorer la sécurité des ITS. Après examen de l'évolution des ITS et DSRC, la fiabilité/qualité de service (QoS) de transmission de bout-en-bout des communications courtes est analysée. Ensuite, les effets de la transmission et QoS sur le système de commande PID et flou sont étudiés respectivement.D'abord, Les méthodes de protection des données utilisées dans le protocole Bluetooth sont analysées en termes de fiabilité. Un modèle de performance du nœud est construit pour les différentes distributions de temps de service du nœud. Ainsi, chaque nœud dans le réseau peut surveiller directement la qualité de service du nœud à tout moment. Basé sur ce modèle, un protocole de routage ad hoc (NPDSR) est proposé. Ce protocole présente les avantages de maintenir la qualité de service requise de la communication, et des économies de routage.Deuxièmement, les effets sur les systèmes de contrôle, en termes de retards et de pertes, sont analysés en utilisant la méthode mathématique et statistique. Des fonctions descriptives pour les contrôleurs flous de types Mamdani et T-S sont fournies, et la stabilité du contrôleur multi-flou avec un retard de communication est analysée à l'aide des lieux de Nyquist.Enfin, en perspective, l’utilisation possible de NS-2 sur le modèle de simulation et de vérification est discutée, ce qui s’avère intéressant pour simuler des protocoles différents. En outre, il peut être connecté avec Simulink permettant une meilleure analyse de performances des systèmes de contrôle en réseau / This PhD thesis is dedicated to the reliability assessment for intelligent vehicles platoon with the main aim of providing an approach to evaluate and enhance the safety of ITS. After a review of developments of ITS and DSRC, the reliability/QoS of end-to-end transmission of short range communication is analyzed. Then, the effects of transmission QoS on PID sampling control system and fuzzy control system are studied respectively.At first, The data protection methods used in Bluetooth communication protocol are analyzed for the data reliability. A node performance model is built, suitable for different distributions of service time of the node. Hence, a node in the network can monitor the QoS of the node by itself at any time. Based on this model, a QoS-aware ad hoc routing protocol (NPDSR) is proposed. This protocol has the advantages in maintaining requested QoS of communication, and it has less routing overhead.Secondly, for the effects on the control systems, time delay and loss are both discussed using mathematical and statistical simulation methods. Describing functions for both Mamdani and T-S type fuzzy controllers are provided. The stability of multi-fuzzy controller with communication delay is analyzed using Nyquist stability plots.Finally, in the perspective, the possible use of NS-2 on the model simulation and verification has been discussed, which is powerful in simulating different behavior of protocols, routing protocol comparisons. Also, it can be connected with Simulink to enhance performance the simulation of network control systems

De nos jours, la filiale automobile connait une évolution énorme en raison de la croissance évolutive des technologies de communication, des aptitudes de détection et de perception de l’environnement, et des capacités de stockage et de traitement présentes dans les véhicules. En effet, une voiture est devenue une sorte d'agent mobile capable de percevoir son environnement et d’en collecter des informations, de communiquer avec les autres véhicules ou infrastructures présentes sur la route, et de traiter les données collectées. Ces progrès stimulent le développement de plusieurs types d'applications qui vont permettre d'améliorer la sécurité et l'efficacité de conduite et de rendre le voyage des automobilistes plus confortable. Cependant, ce développement repose beaucoup sur les données collectées et donc ne pourra se faire que via une collecte sécurisée et un traitement efficace de ces données détectées. La collecte de données dans un réseau véhiculaire a toujours été un véritable défi en raison des caractéristiques spécifiques de ces réseaux fortement dynamiques (changement fréquent de topologie, vitesse élevée des véhicules et fragmentation fréquente du réseau), qui conduisent à des communications opportunistes et non durables. L'aspect sécurité, reste un autre maillon faible de ces réseaux sans fils vu qu'ils sont par nature vulnérables à diverses types d'attaques visant à falsifier les données recueillies et affecter leur intégrité. En outre, les données recueillies ne sont pas compréhensibles par eux-mêmes et ne peuvent pas être interprétées et comprises si montrées directement à un conducteur ou envoyées à d'autres nœuds dans le réseau. Elles doivent être traitées et analysées pour extraire les caractéristiques significatives et informations pour développer des applications utiles et fiables. En plus, les applications développées ont toujours des exigences différentes en matière de qualité de service (QdS). Plusieurs travaux de recherche et projets ont été menées pour surmonter les défis susmentionnés. Néanmoins, ils n'ont pas abouti à la perfection et souffrent encore de certaines faiblesses. Pour cette raison, nous focalisons nos efforts durant cette thèse au développement d’une plateforme de collecte efficace et sécurisée de données dans un réseau de véhicules ainsi que l’exploitation de ces données par des applications améliorant le voyage des automobilistes et la connectivité des véhicules. Pour ce faire, nous proposons une première solution visant à déployer de manière optimale des véhicules, qui auront la tâche de recueillir des données, dans une zone urbaine. Ensuite, nous proposons un nouveau protocole de routage sécurisé permettant de relayer les données collectées vers une destination en se basant sur un système de détection et d'expulsion des véhicules malveillants. Ce protocole est par la suite amélioré avec un nouveau mécanisme de prévention d'intrusion permettant de détecter des attaquants au préalable en utilisant les filtres de Kalman. En deuxième partie de thèse, nous nous sommes concentré sur l’exploitation de ces données en développant une première application capable de calculer de manière fine l’itinéraire le plus économique pour les automobilistes ou tout gestionnaire de flottes de véhicules. Cette solution est basée sur les données influents sur la consommation de carburant et collectées à partir des véhicules eux mêmes et aussi d’autres sources d’informations dans l’Internet et accessibles via des API spécifiques. Enfin, un mécanisme spatio-temporel permettant de choisir le meilleur médium de communication disponible a été développé. Ce dernier est basé sur la logique floue et considère les informations recueillies sur les réseaux, les utilisateurs et les applications pour préserver de meilleure qualité de service. / Nowadays, automotive area is witnessing a tremendous evolution due to the increasing growth in communication technologies, environmental sensing & perception aptitudes, and storage & processing capacities that we can find in recent vehicles. Indeed, a car is being a kind of intelligent mobile agent able to perceive its environment, sense and process data using on-board systems and interact with other vehicles or existing infrastructure. These advancements stimulate the development of several kinds of applications to enhance driving safety and efficiency and make traveling more comfortable. However, developing such advanced applications relies heavily on the quality of the data and therefore can be realized only with the help of a secure data collection and efficient data treatment and analysis. Data collection in a vehicular network has been always a real challenge due to the specific characteristics of these highly dynamic networks (frequent changing topology, vehicles speed and frequent fragmentation), which lead to opportunistic and non long lasting communications. Security, remains another weak aspect in these wireless networks since they are by nature vulnerable to various kinds of attacks aiming to falsify collected data and affect their integrity. Furthermore, collected data are not understandable by themselves and could not be interpreted and understood if directly shown to a driver or sent to other nodes in the network. They should be treated and analyzed to extract meaningful features and information to develop reliable applications. In addition, developed applications always have different requirements regarding quality of service (QoS). Several research investigations and projects have been conducted to overcome the aforementioned challenges. However, they still did not meet perfection and suffer from some weaknesses. For this reason, we focus our efforts during this thesis to develop a platform for a secure and efficient data collection and exploitation to provide vehicular network users with efficient applications to ease their travel with protected and available connectivity. Therefore, we first propose a solution to deploy an optimized number of data harvesters to collect data from an urban area. Then, we propose a new secure intersection based routing protocol to relay data to a destination in a secure manner based on a monitoring architecture able to detect and evict malicious vehicles. This protocol is after that enhanced with a new intrusion detection and prevention mechanism to decrease the vulnerability window and detect attackers before they persist their attacks using Kalman filter. In a second part of this thesis, we concentrate on the exploitation of collected data by developing an application able to calculate the most economic itinerary in a refined manner for drivers and fleet management companies. This solution is based on several information that may affect fuel consumption, which are provided by vehicles and other sources in Internet accessible via specific APIs, and targets to economize money and time. Finally, a spatio-temporal mechanism allowing to choose the best available communication medium is developed. This latter is based on fuzzy logic to assess a smooth and seamless handover, and considers collected information from the network, users and applications to preserve high quality of service.

Abstract Radio resource management techniques for broadband wireless systems beyond the existing cellular systems are developed while considering their special characteristics such as multi-carrier techniques, adaptive radio links and multiple-input multiple-output (MIMO) antenna techniques. Special focus is put on the design of linear transmission strategies in a cooperative cellular system where signal processing can be performed in a centralised manner across distributed base station (BS) antenna heads. A time-division duplex cellular system based on orthogonal frequency division multiplexing (OFDM) with adaptive MIMO transmission is considered in the case where the received signals are corrupted by non-reciprocal inter-cell interference. A bandwidth efficient closed-loop compensation algorithm combined with interference suppression at the receiver is proposed to compensate for the interference and to guarantee the desired Quality of Service (QoS) when the interference structure is known solely at the receiver. A greedy beam ordering and selection algorithm is proposed to maximise the sum rate of a multiuser MIMO downlink (DL) with a block zero forcing (ZF) transmission. The performance of the block-ZF transmission combined with the greedy scheduling is shown to approach the sum capacity as the number of users increases. The maximum sum rate is often found to be achieved by transmitting to a smaller number of users or beams than the spatial dimensions allow. In addition, a low complexity algorithm for joint user, bit and power allocation with a low signalling overhead is proposed. Different linear transmission schemes, including the ZF as a special case, are developed for the scenario where the cooperative processing of the transmitted signal is applied to users located within a soft handover (SHO) region. The considered optimisation criteria include minimum power beamformer design; balancing the weighted signal-to-interference-plus-noise ratio (SINR) values per data stream; weighted sum rate maximisation; and balancing the weighted rate per user with additional QoS constraints such as guaranteed bit rate per user. The method can accommodate supplementary constraints, e.g., per antenna or per BS power constraints, and upper/lower bounds for the SINR values of the data streams. The proposed iterative algorithms are shown to provide powerful solutions for difficult non-convex transceiver optimisation problems. System level evaluation is performed in order to assess the impact of a realistic multi-cell environment on the performance of a cellular MIMO-OFDM system. The users located in the SHO region are shown to benefit from greatly increased transmission rates. Consequently, significant overall system level gains result from cooperative SHO processing. The proposed SHO scheme can be used for providing a more evenly distributed service over the entire cellular network.

[pt] Este trabalho faz um estudo da arquitetura Diffserv para oferecimento de QoS na internet.São revistos conceitos básicos e descritos os principais mecanismos de controle de tráfego.Utilizando o software NS2, avalia-se o desempenho desses algoritmos de controles de tráfego.Para um cenário específico foram estudados: disciplinas de serviço, mecanismos de gerenciamento de buffers, para diferentes fontes de tráfego, procurando-se obter medidas de desempenho que possam ser úteis em projetos de rede com qualidade de serviço. / [en] This work presents a Diffserv architecture study to provide QoS in the Internet. A review of some basic concepts of the main traffic control algorithm and a performance evaluation, through the NS simulation program, is done. In order to get important performance measurement of the QoS network, it was done, for a specific scenario, a study of the queue discipline, queue activity management, with different traffic source.

Magister Commercii (Industrial Psychology) - MCom(IPS) / The primary aim of this thesis was to undertake research in a Higher Education and Training Institution in a Provincial Government Department in the Western Cape to determine which variables affect the services that are being delivered and the quality of the services and how these services could be improved. The population selected for the purpose of the research was a large number of students at a Higher Education and Training Institution in a Provincial Government Department in the Western Cape. A research sample represented by a subset of participants from this organisation was selected. A biographical questionnaire and the SERVQUAL questionnaire were administered to a sample of 130 students enrolled at a Higher Education Institution in the Western Cape. The results indicate that there are significant relationships between selected biographical variables and perceptions of service quality. Moreover, there were also statistically significant differences in perceptions on the variables Reliability, Responsiveness, Assurance, Tangibles and Empathy. Tentative conclusions can be drawn from the results and recommendations regarding future research are highlighted. / South Africa

An important goal of modern data networks is to support multiple applications over a single network infrastructure. The combination of data, voice, video and conference traffic, each requiring a unique Quality of Service (QoS), makes resource dimensioning a very challenging task. To guarantee QoS by mere over-provisioning of bandwidth is not viable in the long run, as network resources are expensive. The aim of proper resource dimensioning is to provide the required QoS while making optimal use of the allocated bandwidth. Dimensioning parameters used by service providers today are based on best practice recommendations, and are not necessarily optimal. This dissertation focuses on resource dimensioning for the DiffServ network architecture. Four predefined traffic classes, i.e. Real Time (RT), Interactive Business (IB), Bulk Business (BB) and General Data (GD), needed to be dimensioned in terms of bandwidth allocation and traffic regulation. To perform this task, a study was made of the DiffServ mechanism and the QoS requirements of each class. Traffic generators were required for each class to perform simulations. Our investigations show that the dominating Transport Layer protocol for the RT class is UDP, while TCP is mostly used by the other classes. This led to a separate analysis and requirement for traffic models for UDP and TCP traffic. Analysis of real-world data shows that modern network traffic is characterized by long-range dependency, self-similarity and a very bursty nature. Our evaluation of various traffic models indicates that the Multi-fractal Wavelet Model (MWM) is best for TCP due to its ability to capture long-range dependency and self-similarity. The Markov Modulated Poisson Process (MMPP) is able to model occasional long OFF-periods and burstiness present in UDP traffic. Hence, these two models were used in simulations. A test bed was implemented to evaluate performance of the four traffic classes defined in DiffServ. Traffic was sent through the test bed, while delay and loss was measured. For single class simulations, dimensioning values were obtained while conforming to the QoS specifications. Multi-class simulations investigated the effects of statistical multiplexing on the obtained values. Simulation results for various numerical provisioning factors (PF) were obtained. These factors are used to determine the link data rate as a function of the required average bandwidth and QoS. The use of class-based differentiation for QoS showed that strict delay and loss bounds can be guaranteed, even in the presence of very high (up to 90%) bandwidth utilization. Simulation results showed small deviations from best practice recommendation PF values: A value of 4 is currently used for both RT and IB classes, while 2 is used for the BB class. This dissertation indicates that 3.89 for RT, 3.81 for IB and 2.48 for BB achieve the prescribed QoS more accurately. It was concluded that either the bandwidth distribution among classes, or quality guarantees for the BB class should be adjusted since the RT and IB classes over-performed while BB under-performed. The results contribute to the process of resource dimensioning by adding value to dimensioning parameters through simulation rather than mere intuition or educated guessing. / Dissertation (MEng (Electronic Engineering))--University of Pretoria, 2007. / Electrical, Electronic and Computer Engineering / unrestricted

Finding an optimal solution to the problem of fast and efficient provisioning of reliable connections and failure recovery in future intelligent optical networks is an ongoing challenge. In this dissertation, we investigate and compare the performance of an adapted shared-path protection algorithm with a more conventional approach; both designed for survivable optical Wavelength Division Multiplexing (WDM) mesh networks. The effect of different classes of service on performance is also investigated. Dedicated path protection is a proactive scheme which reserves spare resources to combat single link failures. Conventional Shared-path Protection (CSP) is desirable due to the efficient utilization of resources which results from the sharing of backup paths. Availability is an important performance assessment factor which measures the probability that a connection is in an operational state at some point in time. It is the instantaneous counterpart of reliability. Therefore, connections that do not meet their availability requirements are considered to be unreliable. Reliability Aware Shared-path Protection (RASP) adopts the advantages of CSP by provisioning reliable connections efficiently, but provides protection for unreliable connections only. With the use of a link disjoint parameter, RASP also permits the routing of partial link disjoint backup paths. A simulation study, which evaluates four performance parameters, is undertaken using a South African mesh network. The parameters that are investigated are: 1. Blocking Probability (BP), which considers the percentage of connection requests that are blocked, 2. Backup Success Ratio (BSR), which considers the number of connections that are successfully provisioned with a backup protection path, 3. Backup Primary Resource Ratio (BPR), which considers the ratio of resources utilized to cater for working traffic to the resources reserved for protection paths and lastly 4. Reliability Satisfaction Ratio (RSR), which evaluates the ratio of provisioned connections that meet their availability requirements to the total number of provisioned connections. Under dynamic traffic conditions with varying network load, simulation results show that RASP can provision reliable connections and satisfy Service Level Agreement (SLA) requirements. A competitive Blocking Probability (BP) and lower Backup Primary Resource Ratio (BPR) signify an improvement in resource utilization efficiency. A higher Backup Success Ratio (BSR) was also achieved under high Quality of Service (QoS) constraints. The significance of different availability requirements is evaluated by creating three categories, high availability, medium availability and low availability. These three categories represent three classes of service, with availability used as the QoS parameter. Within each class, the performance of RASP and CSP is observed and analyzed, using the parameters described above. Results show that both the BP and BPR increase with an increase in the availability requirements. The RSR decreases as the reliability requirements increase and a variation in BSR is also indicated. / Dissertation (MEng)--University of Pretoria, 2009. / Electrical, Electronic and Computer Engineering / unrestricted