Quality of Experience in Cyber-Physical Social Systems: A Cultural Heritage Space Use Case

In this PhD thesis, the focus is placed on the optimization of user Quality of Experience (QoE) in Cyber Physical Social Systems and speci cally in cultural heritage spaces. In order to achieve maximization of visitor perceived satisfaction, the challenges associated with visitor optimal decision making regarding touring choices and strategies in a museum or a cultural heritage space are examined and the problem of museum congestion is αddressed. Cultural heritage spaces, and museums in particular, constitute a special type of socio-physical system because, in contrast to other social systems like schools or churches, user experience is primarily controlled by the visitors themselves. Such a system also embodies both human behaviors and physical and technical constraints, a fact that makes adopting a socio-technical perspective in order to improve the visiting experience, essential. Within the above setting, quantitative models and functions are initially formulated to express the visitor experience that is gained throughout a touring process. The functions are based on several socio-physical and behavioral factors. Using this QoE modeling approach, the problem of how to optimise visitor route choices is addressed. A social recommendation and personalization framework is also presented that exploits common visitor characteristics and recommends a set of exhibits to be visited. The creation of self-organizing museum visitor communities are proposed as a means to enhance the visiting experience. They exploit visitor personal characteristics and social interactions and are based on a participatory action research (PAR) process. Recommendation Selection and Visiting Time Management (RSVTM) are combined and formulated into a two-stage distributed algorithm, based on game theory and reinforcement learning. In addition, this PhD thesis examines the problem of congestion management in cultural heritage spaces from a more pragmatic perspective, considering visitor behavioral characteristics and risk preferences. The motivation behind this approach arose from the observation that, in cultural heritage spaces, people interact with each other and consequently the decisions and behavior of one visitor influence and are influenced by others. It is, therefore, important to understand the unknown behavior tendencies of visitors especially when making decisions in order to improve their visiting experience and reduce museum congestion. The proposed mechanisms are founded on and powered by the principles of Prospect Theory and the Tragedy of the Commons. Particular attention is paid to modeling and capturing visitor behaviors and decision making under the potential risks and uncertainties which are typically encountered by visitors during their visit. According to their relative popularity and attractiveness, exhibits at a cultural heritage site are classi ed into two main categories: safe exhibits and Common Pool of Resources (CPR) exhibits. CPR exhibits are considered non-excludable and rivalrous in nature, meaning that they may experience "failure" due to over-exploitation. As a result, a visitor's decision to invest time at a CPR exhibit is regarded as risky because his/her perceived satisfaction greatly depends on the cumulative time spent at it by all visitors. A non-cooperative game among the visitors is formulated and solved in a distributed manner in order to determine the optimal investment time at exhibits for each visitor, while maximizing the visitor's perceived satisfaction. Detailed numerical results are presented, which provide useful insights into visitor behaviors and how these influence visitor perceived satisfaction, as well as museum congestion. Finally, pricing is introduced as an effective mechanism to address the problem of museum congestion. Motivated by several studies that position pricing as a mechanism to prevent overcrowding in museums, this thesis analyzes and studies the impact of different pricing policies on visitor decisions when they act as prospect-theoretic decision-makers. The theory of S-modular games is adopted to determine the time invested by each visitor at exhibits while maximizing satisfaction gained

Measures of quality of experience based on the E-model during a VoIP call

Orientador: Yuzo IanoTese (doutorado) ¿ Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: A tecnologia de voz sobre protocolo de internet (voz sobre IP) ou simplesmente, VoIP (Voice Over Internet Protocol) ganha novos usuários decorrente do cenário atual de mercado de convergência de redes de dados e telecomunicações. Entretanto, o sucesso desta tecnologia depende fortemente da qualidade do sinal da fala percebida pelo usuário, uma medida subjetiva, também conhecida como Qualidade de Experiência (Quality of Experience - QoE). Esta Tese propõe e valida um mecanismo de observação de variáveis de ambiente durante uma comunicação VoIP tendo como saída um número que representa a QoE não referenciada (sem o sinal transmitido, somente o sinal recebido) ao utilizar o Modelo-E com o propósito de selecionar os melhores parâmetros disponíveis de configuração que afetam o fluxo de voz e ao mesmo tempo obter a melhor qualidade de chamada possível dentro de um determinado cenário de rede. O resultado obtido fez a ligação entre uma medida objetiva, o parâmetro R gerado pelo Modelo-E, e uma medida subjetiva estimada, o MOS (Mean Opinion Score), durante uma chamada VoIP, não se limitando a medida em si. Todavia, cobriu-se todo o cenário para a medição e a comparação com sistemas padrões de medição de qualidade, formando uma base de conhecimento com os resultados obtidos. O método utilizado de estimativa de qualidade da fala foi comparado em diferentes codecs de voz padrão ITU-T (PCMU, GSM, G.723, G.729, G.726-32), testados em uma topologia de rede que sofreu distorções, como diferentes situações de perdas de dados (0,0%, 1,0%, 2,0%, 2,5%, 3,0%, 5,0%, 7,5%, 10,0%). Uma análise de regressão foi utilizada para permitir uma melhor compreensão do impacto das condições de rede e codecs sobre a QoE do serviço VoIP medido. Foi utilizado um suíte de testes padronizados para medição da QoE nos arquivos de voz recebidos e transmitidos durante os testes baseados em testes referenciados (com os sinais transmitidos e recebidos) nos padrões ITU-T P.863 (Perceptual Objective Listening Quality Assessment - POLQA) e ITU-T P.862 (Perceptual Evaluation of Speech Quality - PESQ) e os resultados foram comparados com os obtidos pelo método não referenciado proposto para medida de QoE. Para os resultados do codec testado foi aplicado o método de regressão linear sendo a variável independente as medidas de QoE obtidas pelo método proposto e a variável dependente foram os resultados obtidos pelos algoritmos PESQ e POLQA. Para todos os codecs testados, o Coeficiente de Determinação (R2) entre o método proposto e os resultados obtidos pelo algoritmo PESQ foram superiores a 0,90 indicando uma forte correlação linear. Já entre o método proposto e o algoritmo POLQA, para os codecs PCMU, GSM e G.723, os resultados de R2 foram superiores a 0,973, indicando uma correlação muito forte. R2 para o codec G.726-32 foi de 0,88 indicando uma correlação forte. Já para o codec G.729, R2 ficou em 0,67 indicando que o modelo linear pode não ser o mais adequado para explicar a relação entre os resultados do método proposto e os valores obtidos pelo algoritmo POLQAAbstract: The technology of Voice over Internet Protocol (Voice over IP or simply VoIP) is present in our personal and professional lives. The number of VoIP users increases day after day due to the current scenario of convergence of data and telecommunications networks. However, the success of this technology depends on the speech signal quality as perceived by the user, a subjective measure as function of the user's point of view, also known as the Quality of Experience (QoE). This thesis proposes and validates an environment variable observation mechanism during a VoIP communication having as output a number that represents the QoE not referenced (without the transmitted signal, only the received signal) of the call, using the E-Model, in order to select the best available parameter settings that affect voice flow of the current VoIP call and at the same time gets the best call quality as possible within a given network scenario. The result relates an objective measurement, the R parameter generated by the E-Model, to the estimated subjective measurement, MOS, during a VoIP call, not limited to the measurement itself. However, it covered the whole scenario for measurement and comparison with quality measurement standards systems, forming a knowledge base with the results. The method of speech quality estimation was compared in different standard voice codec's ITU-T (PCMU, GSM, G.723, G.729, G.726-32) tested in a network topology that has suffered distortions, as different situations of data loss (0.0%, 1.0%, 2.0%, 2.5%, 3.0%, 5.0%, 7.5%, 10.0%). A regression analysis was used to allow a better understanding of the impact of network conditions and codec's on the VoIP service QoE measured. In this thesis it was used a suite of standardized tests for measuring QoE in voice files received and transmitted during testing based on referenced tests (with the transmitted and received signals) in the ITU-T P.863 standard (Perceptual Objective Listening Quality Assessment - POLQA) and ITU-T P.862 (Perceptual Evaluation of Speech Quality - PESQ) and the results were compared with those obtained by the no referenced measure method of QoE proposed in this thesis. The linear regression was applied in order to analyze the results of the tested codec. The independent variable was the QoE measurements obtained by the proposed method to measure QoE and the dependent variable were the results of PESQ and POLQA algorithms. For all tested codec's, the Coefficient of Determination (R2) between the proposed method and the results of the PESQ algorithm was higher than 0.90 indicates a strong linear correlation. For PCMU, G.723, GSM codec's R2 was greater than 0.973 indicating a strong correlation between the results of proposed method and the results of POLQA algorithm. R2 for G.726-32 codec was 0.88 that indicates a high correlation. For G.729 codec, R2 was 0.67 that indicates the linear model may not be the most appropriate to explain the relationship between the results of the proposed method and values obtained by POLQA algorithmDoutoradoTelecomunicações e TelemáticaDoutor em Engenharia Elétric

Systemunterstützung zur Bewertung der Qualität persönlicher Cloud-Dienste

Cloud-Technologien ermöglichen Endnutzern das flexible und bedarfsgerechte Beziehen von IT-Leistungen über das Internet. In einer Public Cloud können die Dienste oder Ressourcen von beliebigen Unternehmen und Endnutzern zeit- sowie ortsunabhängig verwendet werden. Nutzer von Cloud-basierten Softwareanwendungen haben keinen Einfluss auf die sachgerechte Verwaltung und Überwachung der darunterliegenden Cloud-Infrastruktur. Infolgedessen haben sie zunehmend Bedenken hinsichtlich der Sicherheit ihrer Daten oder in Bezug auf die Performance bzw. Verfügbarkeit des Dienstes. Um diese Bedenken abzubauen, müssen die nichtfunktionalen Eigenschaften eines Dienstes betrachtet werden, da sie dessen qualitative Wahrnehmung beeinflussen. Derzeit steht Endnutzern weder ein vollständiger Kriterienkatalog zur Bewertung von Cloud-Diensten als Orientierungshilfe zur Verfügung noch sind Cloud-Gütesiegel oder Zertifikate ausreichend verbreitet. Mangelnde Fachkenntnisse und verstreute oder nicht verfügbare Qualitätsinformationen führen dazu, dass Endnutzer die Dienstqualität nur erschwert oder gar nicht bewerten können. Das Ziel der Dissertation ist, Cloud-Nutzer bei der schnellen und umfangreichen Überwachung und Bewertung der Qualität ihrer Public-Cloud-Dienste zu unterstützen. Die Berücksichtigung der Nutzerinteressen und -bedürfnisse in Bezug auf die Dienstqualität steht dabei im Vordergrund. Die Untersuchung der verwandten Cloud-spezifischen Qualitätsmodelle hat gezeigt, dass die Modelle unvollständig sind und keine Aussagen zu deren Eignung und Akzeptanz aus Nutzersicht getroffen werden. Folglich werden in der Arbeit zunächst die nichtfunktionalen Qualitätsattribute von Softwareanwendungen identifiziert und nutzerfreundlich kategorisiert. Das daraus abgeleitete Modell bildet die Grundlage für ein Qualitätsinformationssystem, das Endnutzer künftig bei der kontinuierlichen Einschätzung der Qualität ihrer Dienste unterstützen soll. Darüber hinaus wird ein Konzept zur nutzerfreundlichen visuellen Aufbereitung der Qualitätsinformationen entwickelt. Es werden Empfehlungen zur Darstellung, Strukturierung und Verknüpfung der Informationen innerhalb des Systems gegeben. Jeder Nutzer kann individuell festlegen, über welche Qualitätseigenschaften er informiert werden möchte und wann die Qualität eines Dienstes als hoch eingeschätzt werden soll. Mit der prototypisch technischen Realisierung des Qualitätsinformationssystems werden die praktische Eignung des Qualitätsmodells und Konzeptes demonstriert. Ferner belegen die Ergebnisse von zwei Nutzerbefragungen, dass Cloud-Nutzer durch das Informationssystem bei der Qualitätsbewertung unterstützt werden und mit dem System grundsätzlich zufrieden sind