Placement solutions for multiple versions of a multimedia object

Transcoding is an important technology which adapts the same multimedia object to diverse mobile appliances; thus, users' requests for a specified version of a multimedia object could be served by a more detailed version cached according to transcoding. Therefore, it is of particularly theoretical and practical necessity to determine the proper versions to be cached at a node such that the specified objective is achieved. In this paper, we address the problem of multimedia object placement. The performance objective is to minimize the total access cost by considering both transmission cost and transcoding cost. We present an optimal dynamic programming-based solution for this problem. The performance of the proposed solutions is evaluated with a set of carefully designed simulation experiments for various performance metrics over a wide range of system parameters. The simulation results show that our solution consistently and significantly outperforms comparison solutions in terms of all the performance metrics considered.Keqiu Li, Hong Shen, Francis Y. L. Chi

Proposta de um modelo de qualidade de serviço e segurança para a tecnologia de web services

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Ciência da Computação

Rich media content adaptation in e-learning systems

The wide use of e-technologies represents a great opportunity for underserved segments of the population, especially with the aim of reintegrating excluded individuals back into society through education. This is particularly true for people with different types of disabilities who may have difficulties while attending traditional on-site learning programs that are typically based on printed learning resources. The creation and provision of accessible e-learning contents may therefore become a key factor in enabling people with different access needs to enjoy quality learning experiences and services. Another e-learning challenge is represented by m-learning (which stands for mobile learning), which is emerging as a consequence of mobile terminals diffusion and provides the opportunity to browse didactical materials everywhere, outside places that are traditionally devoted to education. Both such situations share the need to access materials in limited conditions and collide with the growing use of rich media in didactical contents, which are designed to be enjoyed without any restriction. Nowadays, Web-based teaching makes great use of multimedia technologies, ranging from Flash animations to prerecorded video-lectures. Rich media in e-learning can offer significant potential in enhancing the learning environment, through helping to increase access to education, enhance the learning experience and support multiple learning styles. Moreover, they can often be used to improve the structure of Web-based courses. These highly variegated and structured contents may significantly improve the quality and the effectiveness of educational activities for learners. For example, rich media contents allow us to describe complex concepts and process flows. Audio and video elements may be utilized to add a “human touch” to distance-learning courses. Finally, real lectures may be recorded and distributed to integrate or enrich on line materials. A confirmation of the advantages of these approaches can be seen in the exponential growth of video-lecture availability on the net, due to the ease of recording and delivering activities which take place in a traditional classroom. Furthermore, the wide use of assistive technologies for learners with disabilities injects new life into e-learning systems. E-learning allows distance and flexible educational activities, thus helping disabled learners to access resources which would otherwise present significant barriers for them. For instance, students with visual impairments have difficulties in reading traditional visual materials, deaf learners have trouble in following traditional (spoken) lectures, people with motion disabilities have problems in attending on-site programs. As already mentioned, the use of wireless technologies and pervasive computing may really enhance the educational learner experience by offering mobile e-learning services that can be accessed by handheld devices. This new paradigm of educational content distribution maximizes the benefits for learners since it enables users to overcome constraints imposed by the surrounding environment. While certainly helpful for users without disabilities, we believe that the use of newmobile technologies may also become a fundamental tool for impaired learners, since it frees them from sitting in front of a PC. In this way, educational activities can be enjoyed by all the users, without hindrance, thus increasing the social inclusion of non-typical learners. While the provision of fully accessible and portable video-lectures may be extremely useful for students, it is widely recognized that structuring and managing rich media contents for mobile learning services are complex and expensive tasks. Indeed, major difficulties originate from the basic need to provide a textual equivalent for each media resource composing a rich media Learning Object (LO). Moreover, tests need to be carried out to establish whether a given LO is fully accessible to all kinds of learners. Unfortunately, both these tasks are truly time-consuming processes, depending on the type of contents the teacher is writing and on the authoring tool he/she is using. Due to these difficulties, online LOs are often distributed as partially accessible or totally inaccessible content. Bearing this in mind, this thesis aims to discuss the key issues of a system we have developed to deliver accessible, customized or nomadic learning experiences to learners with different access needs and skills. To reduce the risk of excluding users with particular access capabilities, our system exploits Learning Objects (LOs) which are dynamically adapted and transcoded based on the specific needs of non-typical users and on the barriers that they can encounter in the environment. The basic idea is to dynamically adapt contents, by selecting them from a set of media resources packaged in SCORM-compliant LOs and stored in a self-adapting format. The system schedules and orchestrates a set of transcoding processes based on specific learner needs, so as to produce a customized LO that can be fully enjoyed by any (impaired or mobile) student

Modelo de correlación QoS-QoE en un ambiente de aprovisionamiento de servicio de telecomunicaciones OTT-Telco

ANTECEDENTES El aprovisionamiento de la Calidad de la Experiencia (QoE) en servicios de telecomunicaciones requiere de sistemas de gestión que permitan monitorizar y controlar la QoE de los usuarios luego de consumir diferentes servicios de internet provistos sobre la red del operador. En efecto, el consumo elevado de datos por parte de los usuarios requiere, a nivel de gestión de la red, la asignación de recursos suficientes para el correcto funcionamiento de los servicios. En particular, la configuración de la Calidad del Servicio (QoS) ofrecida por el operador dentro de su dominio de operación se torna fundamental para proveer un tratamiento apropiado del tráfico, permitiendo que la percepción de la calidad del servicio por parte de los usuarios finales pueda mantenerse dentro del umbral de tolerancia de acuerdo con las políticas establecidas por la compañía de telecomunicaciones (Telco). En consecuencia, un modelo de correlación QoS-QoE es clave en el aprovisionamiento de servicios de internet sobre la infraestructura del operador de telecomunicaciones. OBJETIVOS La presente tesis de doctorado se centra en proponer un modelo de correlación QoS-QoE en un ambiente de aprovisionamiento de servicios de telecomunicaciones OTT-Telco. Para ello, cinco acciones generales deben llevarse a cabo; a saber: () caracterizar los parámetros de QoS que mayor efecto tienen en la degradación de servicios OTT. () determinar las características, condiciones, parámetros y medidas de QoE en la prestación de un servicio OTT. () establecer las condiciones y restricciones de prestación de un servicio OTT en la infraestructura de una Telco que mantenga una buena relación QoS-QoE. () desarrollar un mecanismo de estimación o predicción de QoE con base en los factores de influencia de QoS que afectan la prestación de un servicio OTT. () evaluar experimentalmente el modelo de correlación QoE-QoS. MÉTODOS Para el cumplimiento de los objetivos, se definió un modelo integrado por un macro-componente Conceptualización y otro Operacional. El macro-componente Conceptualización está orientado por el referente metodológico para la construcción de marcos conceptuales de Jabareen, y el macro-componente Operacional está alineado con las fases definidas para el desarrollo de proyectos de minería de datos, CRISP-DM. Adicionalmente, se emplearon diseños de comprobación para los algoritmos, con el fin de comprobar la validez del modelo de estimación basado en algoritmos de aprendizaje automático; es decir, el modelo de estimación fue evaluado a partir de un diseño de comprobación donde se definen, para cada uno de los algoritmos, los parámetros iniciales de operación, las configuraciones de las diferentes pruebas, y las métricas usadas para evaluar su desempeño. RESULTADOS Los resultados más importantes alcanzados son los siguientes: un mapa estratégico del estado de la ciencia en el aprovisionamiento de la QoE para servicios OTT, una conceptualización de los perfiles del modelo de correlación, un modelo matemático para la valoración de la QoE de acuerdo con el comportamiento de consumo de los usuarios, un conjunto de datos de tráfico etiquetado que relaciona el comportamiento de la red con la percepción de la calidad de los usuarios, y un modelo de estimación de la QoE de los usuarios a partir del comportamiento de tráfico de la red. CONCLUSIONES El modelo de correlación QoS-QoE puede ser empleado en sistemas gestión de la QoE donde se requiere por parte de la Telco un diagnóstico y monitorización más objetiva de la percepción de la calidad del servicio por parte de sus usuarios dentro su red de aprovisionamiento. De igual manera, el empleo de parámetros adicionales de contexto de usuario enriquecería los sistemas de gestión de la QoE en el aprovisionamiento de servicios OTT.BACKGROUND Quality of Experience (QoE) provisioning requires robust QoE-centric network and application management on Telco network for providing internet services. Indeed, traffic growth over Telco network demands resource allocation for service well performance. Particularly, Quality of Service (QoS) configuration offered by network provider operational domain becomes a key component for traffic control in a proper manner. Hence, the quality of services perceived can be managed within a tolerance threshold according to telecom operator policies. Therefore, a QoS-QoE correlational model for internet services provisioning over the telecom operator infrastructure is required. AIMS The doctoral thesis is focused on propose a correlation QoS-QoE model for provisioning telecommunications services in OTT-Telco context. To this end, five goals must be accomplishing. () To characterize QoS parameters that more impact have on OTT services performance. () To determinate QoE assumptions, features, parameters, and metrics for OTT service provisioning. () To establish the assumptions and restrictions for providing a well QoS-QoE relation in the telecom operator. () To develop an estimation model for QoE based on QoS factors in the OTT services provisioning. () To evaluate the correlation QoS-QoE model. METHODS To accomplish the aims, a model with a Conceptual and Operational macro-component was structured. The Conceptual macro-component is based on the principles for building conceptual frameworks by Jabareen, and an Operational macro-component aligned with data mining project development phases, CRISP-DM. Furthermore, test bed design was structured to validate the estimation model base on machine learning algorithms; namely, algorithms initial parameters, some tests setup, and regression metrics were determined on a test bed for validate the performance of the estimation model proposed RESULTS The most relevant results achieved are the following: a strategic science map in the QoE provisioning for OTT services, three conceptual profiles as part of the correlation QoS-QoE model, a mathematical model for QoE assessment according to user consumption behavior, a label traffic dataset that relates the traffic network with quality of services perception, and estimation QoE model for users based on traffic flows. CONCLUSIONS The QoS-QoE correlational model can be applied in QoE-Driven application and network management in which an objective controlling and monitoring of quality of services perception by users is required. Moreover, additional user context parameters could be taking account for improving the QoE management systems in OTT services provisioning.Programa de Doctorado en Ciencia y Tecnología Informática por la Universidad Carlos III de MadridPresidente: Jesús García Herrero.- Secretario: José Armando Ordóñez Córdoba.- Vocal: Juan Carlos Cuéllar Quiñóne