Unmanned Aerial Vehicles (UAVs) connected to cellular networks present novel challenges and opportunities in mobility management and localization, distinct from those faced by terrestrial users. This thesis presents an integrated approach, combining two key aspects essential for the integration of UAVs with cellular networks. Firstly, it introduces the mobility management challenges for cellular-connected UAVs, which differ significantly from terrestrial users. While terrestrial mobility management primarily aims to prevent radio link failures near cell boundaries, aerial users experience fragmented and overlapping coverage with line-of-sight conditions involving multiple ground base stations (BSs). Thus, mobility management for UAVs extends beyond link failure avoidance, aiming to minimize unnecessary handovers while ensuring extended service availability, particularly in up-link communication. Line-of-sight conditions from a UAV to multiple BSs increase the likelihood of frequent handovers, resulting in control packet overheads and communication delays. This thesis proposes two approaches to address these challenges: 1) A model-based service availability-aware Mobility Robustness Optimization (MRO) adapting handover parameters to maintain high service availability with minimal handovers, and 2) A model-free approach using Deep Q-networks to decrease unnecessary handovers while preserving high service availability. Simulation results demonstrate that both the proposed algorithms converge promptly and increase the service availability by more than 40 %  while the number of handovers is reduced by more than 50%  as compared to traditional approaches. Secondly, to assess the ability of a network to support the range-based localization for cellular-connected UAVs, an analytical framework is introduced. The metric B-localizability is defined as the probability of successfully receiving localization signals above a specified Signal-to-Interference plus Noise Ratio (SINR) threshold from at least B ground BSs. The framework, accounting for UAV-related parameters in a three-dimensional environment, provides comprehensive insights into factors influencing localizability, such as distance distributions, path loss, interference, and received SINR. Simulation studies explore the correlation between localizability and the number of participating BSs, SINR requirements, air-to-ground channel characteristics, and network coordination. Additionally, an optimization problem is formulated to maximize localizability, investigating the impact of UAV altitude across different scenarios. Our study reveals that in an urban macro environment, the effectiveness of cellular network-based localization increases with altitude, with localizability reaching 100% above 60 meters. This finding indicates that utilizing cellular networks for UAV localization is a viable option. / Unmanned Aerial Vehicles (UAV) anslutna till cellulära nätverk presenterar nya utmaningar och möjligheter inom mobilitetshantering och lokalisering, skilda från dem som markanvändare står inför. Denna avhandling presenterar ett integrerat tillvägagångssätt, som kombinerar två nyckelaspekter som är väsentliga för integrationen av UAV:er med cellulära nätverk. För det första introducerar den mobilitetshanteringsutmaningarna för mobilanslutna UAV:er, som skiljer sig avsevärt från markbundna användare. Medan markbunden mobilitetshantering i första hand syftar till att förhindra radiolänkfel nära cellgränser, upplever antennanvändare fragmenterad och överlappande täckning med siktlinjeförhållanden som involverar flera markbasstationer (BS). Mobilitetshantering för UAV sträcker sig sålunda bortom att undvika länkfel, och syftar till att minimera onödiga överlämningar samtidigt som man säkerställer utökad servicetillgänglighet, särskilt i upplänkskommunikation. Synlinjeförhållanden från en UAV till flera BS:er ökar sannolikheten för frekventa överlämningar, vilket resulterar i kontrollpaketkostnader och kommunikationsförseningar. Denna avhandling föreslår två tillvägagångssätt för att möta dessa utmaningar: 1) En modellbaserad tjänsttillgänglighetsmedveten Mobility Robustness Optimization (MRO) som anpassar parametrar för överlämning för att bibehålla hög servicetillgänglighet med minimal överlämning, och 2) Ett modellfritt tillvägagångssätt med Deep Q- nätverk för att minska onödiga överlämningar samtidigt som hög servicetillgänglighet bibehålls. Simuleringsresultat visar att båda de föreslagna algoritmerna konvergerar snabbt och ökar tjänstens tillgänglighet med mer än 40% medan antalet överlämningar minskas med mer än 50% jämfört med traditionella metoder. För det andra, för att bedöma förmågan hos ett nätverk att stödja den räckviddsbaserade lokaliseringen för de cellulärt anslutna UAV:erna, introduceras ett analytiskt ramverk.Metriska B-lokaliseringsförmågan definieras som sannolikheten för att framgångsrikt ta emot lokaliseringssignaler över en specificerad signal-till-interferens plus brusförhållande (SINR) tröskel från minst B jord BSs.Ramverket, som tar hänsyn till UAV-relaterade parametrar i en tredimensionell miljö, ger omfattande insikter i faktorer som påverkar lokaliserbarhet, såsom avståndsfördelningar, vägförlust, störningar och mottagen SINR. Simuleringsstudier undersöker korrelationen mellan lokaliserbarhet och antalet deltagande BS:er, SINR-krav, luft-till-mark-kanalegenskaper och nätverkskoordination. Dessutom har ett optimeringsproblem formulerats för att maximera lokaliseringsförmågan, undersöka effekten av UAV-höjd över olika scenarier. Vår studie avslöjar att i en urban makromiljö ökar effektiviteten av mobilnätsbaserad lokalisering med höjden, med lokaliserbarhet som når 100% över $60$ meter. Detta fynd indikerar att användning av mobilnät för UAV-lokalisering är ett gångbart alternativ. / <p>QC 20240319</p>

Policy based network management is a promising approach for provisioning and management of quality of service in mobile ad hoc networks. In this thesis, we focus on performance evaluation of this approach in context of the amount of service received by certain nodes called policy execution points (PEPs) or policy clients from certain specialized nodes called the policy decision points (PDPs) or policy servers. We develop analytical models for the study of the system behavior under two scenarios; a simple Markovian scenario where we assume that the random variables associated with system processes follow an exponential distribution and a more complex non-Markovian scenario where we model the system processes according to general distribution functions as observed through simulation. We illustrate that the simplified Markovian model provides a reasonable indication of the trend of the service availability seen by policy clients and highlight the need for an exact analysis of the system without relying on Poisson assumptions for system processes. In the case of the more exact non-Markovian analysis, we show that our model gives a close approximation to the values obtained via empirical methods. Stochastic Petri Nets are used as performance evaluation tools in development and analysis of these system models. / Master of Science

Premature mortality resulting from the growing global burden of noncommunicable diseases (NCDs) is a contemporary development challenge. Low-income and lower-middle-income countries are disproportionately affected, with the poorest in society considered the most vulnerable. A paucity of literature exists on how leadership practices at the implementation level relate to ensuring readiness for NCD services. The purpose of this study was to investigate whether any relationship exists between leadership practices at the county level and readiness for NCD services in Kenya. Path-goal and adaptive leadership theories were used to guide this quantitative correlational study, using secondary data from a 2013 Service Availability and Readiness Assessment survey. Correlation and multiple linear regression tests were used to determine the strength and direction of any relationship between the independent variable of leadership practices (annual work planning, therapeutic committees, and supportive supervision), and the dependent variable of NCD readiness (county readiness score). The results indicated a statistically significant relationship between therapeutic committee (p = .002) and supportive supervision practices (p = .023) and NCD readiness. Leadership practices also had a statistically significant predictive relationship with NCD readiness (p = .009). This study may be significant to county health leaders in relation to their efforts to ensure proximal access to quality NCD services in Kenya. The results of this study may help to promote the development of capacity-building programs targeting health leadership and prioritization of actions to ensure access to NCD prevention and treatment services at the county level in Kenya.

Decisions concerning IT systems are often made without adequate decision-support. This has led to unnecessary IT costs and failures to realize business benefits. The present thesis presents a framework for analysis of four information systems properties relevant to IT decision-making. The work is founded on enterprise architecture, a model-based IT and business management discipline. Based on the existing ArchiMate framework, a new enterprise architecture framework has been developed and implemented in a software tool. The framework supports modeling and analysis of data accuracy, service performance, service availability and application usage. To analyze data accuracy, data flows are modeled, the service availability analysis uses fault tree analysis, the performance analysis employs queuing networks and the application usage analysis combines the Technology Acceptance Model and Task-Technology Fit model. The accuracy of the framework's estimates was empirically tested. Data accuracy and service performance were evaluated in studies at the same power utility. Service availability was tested in multiple studies at banks and power utilities. Data was collected through interviews with system development or maintenance staff. The application usage model was tested in the maintenance management domain. Here, data was collected by means of a survey answered by 55 respondents from three power utilities, one manufacturing company and one nuclear power plant. The service availability studies provided estimates that were accurate within a few hours of logged yearly downtime. The data accuracy estimate was correct within a percentage point when compared to a sample of data objects. Deviations for four out of five service performance estimates were within 15 % from measured values. The application usage analysis explained a high degree of variation in application usage when applied to the maintenance management domain. During the studies of data accuracy, service performance and service availability, records were kept concerning the required modeling and analysis effort. The estimates were obtained with a total effort of about 20 man-hours per estimate. In summary the framework should be useful for IT decision-makers requiring fairly accurate, but not too expensive, estimates of the four properties. / <p>QC 20120912</p>

BACKGROUND: More than 70% of the global premature mortality from NCDs occurs in low- and middle-income countries. These countries, including Nigeria, also have varied but mostly limited health system capacity to respond to cardiovascular disease and diabetes mellitus. Substantial gaps exist in our understanding of the subnational capacity to respond to these conditions in Nigeria. This encompasses a variety of issues, perhaps most importantly the readiness of facilities to provide care and the quality of care provided to patients with these conditions. As the Lagos State government accelerates the rollout of its mandatory state-based health insurance scheme, the number of patients with diabetes and hypertension receiving care will increase, poor management of which can threaten the scheme's financial sustainability. This mixed-methods study was conducted as part of the baseline activities of an impact evaluation of the health insurance program and was designed to answer three questions: 1) What is the capacity and readiness of health facilities in Lagos State to provide hypertension (HTN) and diabetes (DM) care? 2) What is the level of the quality of care provided to patients with HTN and DM, and how does it vary by patient and facility characteristics? 3) What are the barriers to providing diabetes and hypertension care from providers' perspectives? METHODS: The data for this study were collected using three approaches. We conducted a facility survey among public and private facilities (n=84) in Lagos State to assess facility readiness and the functionality of systems required for diabetes and hypertension care. Linear mixed-effects models were used to determine the level and factors associated with the process quality of care provided to patients in 2019 by analyzing clinical data collected via medical chart abstraction. Finally, in-depth interviews were conducted with health care providers (n=20) to explore their practices and the barriers faced in providing care to patients with diabetes and hypertension. RESULTS: The essential inputs needed for diabetes and hypertension care were mostly available; the mean HTN readiness score was 66%, and the DM readiness score was 68.9%. At the same time, systems to facilitate longitudinal care were mostly lacking; 35% had a mechanism for tracking patients who missed appointments, and 52% assigned unique patient identification numbers to NCD patients. Based on the clinical records, the quality of care provided to patients was very low; overall, patients with diabetes and hypertension received less than 30% of recommended care processes. Less than a third of the patients had their blood pressure or blood glucose controlled. There was substantial variation in the mean quality score by patient and across care processes, with lifestyle modification counseling (LSM) counseling the least likely to be delivered. According to providers, the inability to pay for laboratory tests and medications and non-compliance with medications and clinic visits are key barriers to delivery of high-quality services. Barriers at the organizational level included poorly functioning two-way referrals, non-availability of LSM counseling materials, and lack of recall and follow-up systems. CONCLUSION: While the service readiness scores for diabetes and hypertension are moderately high among these health facilities, there are critical deficits in their ability to provide long-term, integrated care of high quality to patients. Addressing these deficits will require the implementation of a comprehensive model of care co-created by providers, health system managers, patients, and insurers. Lessons can be drawn from the implementation of other chronic disease programs to kick start this process. / 2024-08-30T00:00:00Z

Utility Computing is one of the most discussed business models in the context of Cloud Computing. Service providers are more and more pushed into the role of utilities by their customer's expectations. Subsequently, the demand for predictable service availability and pay-per-use pricing models increases. Furthermore, for providers, a new opportunity to optimise resource usage offers arises, resulting from new virtualisation techniques. In this context, the control of service quality and profit depends on a deep understanding of the representation of the relationship between business and technique. This research analyses the relationship between the business model of Utility Computing and Service-oriented Computing architectures hosted in Cloud environments. The relations are clarified in detail for the entire service life cycle and throughout all architectural layers. Based on the elaborated relations, an approach to a delivery framework is evolved, in order to enable the optimisation of the relation attributes, while the service implementation passes through business planning, development, and operations. Related work from academic literature does not cover the collected requirements on service offers in this context. This finding is revealed by a critical review of approaches in the fields of Cloud Computing, Grid Computing, and Application Clusters. The related work is analysed regarding appropriate provision architectures and quality assurance approaches. The main concepts of the delivery framework are evaluated based on a simulation model. To demonstrate the ability of the framework to model complex pay-per-use service cascades in Cloud environments, several experiments have been conducted. First outcomes proof that the contributions of this research undoubtedly enable the optimisation of service quality and profit in Cloud-based Service-oriented Computing architectures.

Verlässliche Dienstbereitstellung ist eines der wichtigsten Ziele in modernen Netzwerken. Da Anbieter und Nutzer Teil einer Informations und Kommunikationstechnologie (IKT) Infrastruktur sind, wird die Verlässlichkeit der Dienste je nach Position der Aktoren variieren, so wie sich die für die Bereitstellung nötigen IKT Geräte ändern. Wir stellen zwei Ansätze zur Quantifizierung nutzerspezifischer Dienstverlässlichkeit vor. Der erste, modellgetriebene Ansatz berechnet momentane Dienstverfügbarkeit. Aus Modellen des Dienstes, der Infrastruktur und einer Abbildung zwischen den beiden, welche die Aktoren der Dienstkommunikation beschreibt, werden durch eine Serie von Modelltransformationen automatisiert Verfügbarkeitsmodelle generiert. Die Realisierbarkeit des Ansatzes wird anhand von Diensten im Netzwerk der Universität Lugano, Schweiz, gezeigt. Der zweite Ansatz behandelt die Responsivität der Dienstfindung, die Wahrscheinlichkeit innerhalb einer Frist Dienstinstanzen zu finden, unter der Annahme von Fehlern. Dies stellt den Hauptteil dieser Arbeit dar. Eine Hierarchie stochastischer Modelle wird vorgestellt, die nutzerspezifische Responsivität auf Basis von Messdaten der Routingebene berechnet. Umfangreiche Experimente wurden im Distributed Embedded Systems (DES) Funktestbett der Freien Universität Berlin durchgefürt. Diese zeigen Probleme aktueller Dienstfindungsprotokolle in modernen, dynamischen Netzwerken. Gleichzeitig dienen sie der Validierung der vorgestellten Modelle. Beide Ansätze zeigen, daß die Verlässlichkeit der Dienstbereitstellung in der Tat deutlich mit der Position von Nutzern und Anbietern variiert, sogar in hochverfügbaren Kabelnetzwerken. Die Ansätze ermöglichen die Optimierung von Dienstnetzwerken anhand bekannter oder erwarteter Nutzungsmuster. Zudem antizipieren sie neuartige Verlässlichkeitsmodelle, welche Dienstfindung, zeitige Bereitstellung, Platzierung und Nutzung kombinieren; Gebiete, die bisher im Allgemeinen getrennt behandelt wurden. / Dependability of service provision is one of the primary goals in modern networks. Since providers and clients are part of a connecting Information and Communications Technology (ICT) infrastructure, service dependability varies with the position of actors as the ICT devices needed for service provision change. We present two approaches to quantify user-perceived service dependability. The first is a model-driven approach to calculate instantaneous service availability. Using input models of the service, the infrastructure and a mapping between the two to describe actors of service communication, availability models are automatically created by a series of model to model transformations. The feasibility of the approach is demonstrated using exemplary services in the network of University of Lugano, Switzerland. The second approach aims at the responsiveness of the service discovery layer, the probability to find service instances within a deadline even in the presence of faults, and is the main part of this thesis. We present a hierarchy of stochastic models to calculate user-perceived responsiveness based on monitoring data from the routing layer. Extensive series of experiments have been run on the Distributed Embedded Systems (DES) wireless testbed at Freie Universität Berlin. They serve both to demonstrate the shortcomings of current discovery protocols in modern dynamic networks and to validate the presented stochastic models. Both approaches demonstrate that the dependability of service provision indeed differs considerably depending on the position of service clients and providers, even in highly reliable wired networks. The two approaches enable optimization of service networks with respect to known or predicted usage patterns. Furthermore, they anticipate novel service dependability models which combine service discovery, timeliness, placement and usage, areas that until now have been treated to a large extent separately.

Since the mid-1970s, top managers, politicians, and officials in both public and private institutions have promoted contracting-out services (privatization) as a means of increasing efficiency, flexibility, and quality. The privatization trend has occurred in many public sector organizations particularly in city services and prisons. Public health services are not immune to this trend. Today many county health departments have contracted the provision of public health services like womens health, primary care, and laboratory services. However, very few studies have analyzed the impact of these privatizations on cost, access, and health outcomes. Proponents favoring the private provision of these services argue that private providers are more efficient and can deliver these services at a lower cost. Also, because of better innovation, private providers can even improve quality. However, among opponents there is concern that a for-profit private provider might cut costs that adversely affects the quality of these services. The purpose of this dissertation is to analyze the effects of the privatization of primary care services on cost, access, and health outcomes in nine large counties in the state of Florida. In a survey of county health departments conducted in 1999, 61 out of 67 counties had outsourced at least one service. Primary care was the second most frequently privatized program. Womens health was the program most often privatized by counties. Using mixed models and logistic regression, a comparison was made between large counties that outsourced primary care services and counties that did not. Multiple years of data were obtained from federal and state sources for analysis.

Cloud computing provides access to on-demand computing resources and storage space, whereby applications and data are hosted with data centers managed by third parties, on a pay-per-use price model. This allows organizations to focus on core business goals instead of managing in-house IT infrastructure.                     However, as more business critical applications and data are moved to the cloud, service availability is becoming a growing concern. A number of recent cloud service disruptions have questioned the reliability of cloud environments to host business critical applications and data. The impact of these disruptions varies, but, in most cases, there are financial losses and damaged reputation among consumers.         This thesis aims to investigate the threats to service availability in cloud computing and to provide some best practices to mitigate some of these threats. As a result, we identified eight categories of threats. They include, in no particular order: power outage, hardware failure, cyber-attack, configuration error, software bug, human error, administrative or legal dispute and network dependency. A number of systematic mitigation techniques to ensure constant availability of service by cloud providers were identified. In addition, practices that can be applied by cloud customers and users of cloud services, to improve service availability were presented.

Les réseaux logiciels (Software Defined Network - SDN) permettent la programmation du réseau et facilitent sa configuration. Bien qu'SDN améliore les performances, il reste confronté à de multiples défis. Dans cette thèse, nous avons développé des solutions qui constituent un premier pas vers les réseaux SDN de prochaine génération. D’abord, nous présentons MINNIE qui permet la scalabilité des commutateurs SDN, qui ne supportent que quelques milliers de règles dans leur coûteuse mémoire TCAM. MINNIE comprime dynamiquement les règles de routage installées dans la TCAM, augmentant ainsi le nombre de règles pouvant être installées. Ensuite, nous abordons le problème de la dégradation de performance des flux courts avec un prototype d’ordonnancement qui exploite les statistiques des commutateurs pour diminuer leur délai de bout-en-bout. Puis, nous visons à diminuer l’intervalle de protection de 50ms qui n’est plus adapté aux applications modernes et réduit leur qualité d’expérience. Notre solution PRoPHYS s’appuie sur les statistiques des commutateurs dans les réseaux hybrides pour découvrir les pannes de liens plus vite que les solutions existantes. Enfin, nous abordons le problème de l’efficacité énergétique qui souvent mène à une dégradation de performance. Nous présentons SENAtoR, qui exploite les nœuds SDN en réseaux hybrides pour éteindre les nœuds réseau sans entraver la performance. Également, nous présentons SEaMLESS qui convertit le service fourni par une machine virtuelle inactive en une fonction de réseaux virtuelle pour permettre à l’administrateur d’utiliser les ressources bloquées tout en maintenant la disponibilité du service. / Software Defined Networking (SDN) was created to provide network programmability and ease complex configuration. Though SDN enhances network performance, it still faces multiple limitations. In this thesis, we build solutions that form a first step towards creating next-generation SDN based networks. In the first part, we present MINNIE to scale the number of rules of SDN switches far beyond the few thousands rules commonly available in TCAM memory, which permits to handle typical data center traffic at very fine grain. To do so MINNIE dynamically compresses the routing rules installed in the TCAM, increasing the number of rules that can be installed. In the second part, we tackle the degraded performance of short flows and present a coarse grained scheduling prototype that leverages SDN switch statistics to decrease their end-to-end delay. Then, we aim at decreasing the 50ms failure protection interval which is not adapted to current broadband speeds and can lead to degraded Quality of Experience. Our solution PRoPHYS leverages the switch statistics in hybrid networks to anticipate link failures by drastically decreasing the number of packets lost. Finally, we tackle the greening problem where often energy efficiency comes at the cost of performance degradation. We present SENAtoR, our solution that leverages SDN nodes in hybrid networks to turn off network devices without hindering the network performance. Finally, we present SEaMLESS that converts idle virtual machines into virtual network functions (VNF) to enable the administrator to further consolidate the data center by turning off more physical servers and reuse resources (e.g. RAM) that are otherwise monopolized.