Estimación del rendimiento de la codificación Dash en la transmisión de video streaming

Propone un método para evaluar el rendimiento de la técnica MPEG-DASH en la entrega del streaming de video. Para ello se mide la similitud del video original, transmitido por el servidor, con el video recepcionado en el cliente. Finalmente, se valida el procedimiento seguido, con un modelo matematico de evaluación de la calidad de experiencia (QoE) del video

Enhancing cooperation in wireless networks using different concepts of game theory

PhDOptimizing radio resource within a network and across cooperating heterogeneous networks is the focus of this thesis. Cooperation in a multi-network environment is tackled by investigating network selection mechanisms. These play an important role in ensuring quality of service for users in a multi-network environment. Churning of mobile users from one service provider to another is already common when people change contracts and in a heterogeneous communication environment, where mobile users have freedom to choose the best wireless service-real time selection is expected to become common feature. This real time selection impacts both the technical and the economic aspects of wireless network operations. Next generation wireless networks will enable a dynamic environment whereby the nodes of the same or even different network operator can interact and cooperate to improve their performance. Cooperation has emerged as a novel communication paradigm that can yield tremendous performance gains from the physical layer all the way up to the application layer. Game theory and in particular coalitional game theory is a highly suited mathematical tool for modelling cooperation between wireless networks and is investigated in this thesis. In this thesis, the churning behaviour of wireless service users is modelled by using evolutionary game theory in the context of WLAN access points and WiMAX networks. This approach illustrates how to improve the user perceived QoS in heterogeneous networks using a two-layered optimization. The top layer views the problem of prediction of the network that would be chosen by a user where the criteria are offered bit rate, price, mobility support and reputation. At the second level, conditional on the strategies chosen by the users, the network provider hypothetically, reconfigures the network, subject to the network constraints of bandwidth and acceptable SNR and optimizes the network coverage to support users who would otherwise not be serviced adequately. This forms an iterative cycle until a solution that optimizes the user satisfaction subject to the adjustments that the network provider can make to mitigate the binding constraints, is found and applied to the real network. The evolutionary equilibrium, which is used to 3 compute the average number of users choosing each wireless service, is taken as the solution. This thesis also proposes a fair and practical cooperation framework in which the base stations belonging to the same network provider cooperate, to serve each other‘s customers. How this cooperation can potentially increase their aggregate payoffs through efficient utilization of resources is shown for the case of dynamic frequency allocation. This cooperation framework needs to intelligently determine the cooperating partner and provide a rational basis for sharing aggregate payoff between the cooperative partners for the stability of the coalition. The optimum cooperation strategy, which involves the allocations of the channels to mobile customers, can be obtained as solutions of linear programming optimizations

Análisis de la calidad experimentada en aplicaciones de voz sobre IP de libre distribución

En este proyecto el trabajo que se ha realizado ha consistido en determinar los parámetros de la red que determinan la calidad de servicio de las aplicaciones de VoIP y comparar los resultados obtenidos con las encuestas realizadas a un número de personas. Para ello, primeramente se ha realizado un estudio de las características y funcionamiento de los protocolos para VoIP. Seguidamente se eligieron 5 aplicaciones de VoIP y se realizaron capturas de su transferencia de paquetes. Con estos datos se ha podido calcular los parámetros de la red y se ha establecido de este modo la calidad de servicio ofrecida. El análisis de las aplicaciones se realizará mediante capturas con la herramienta wireshark, que serán analizadas posteriormente utilizando awk. Por otro lado para medir la QoE se han realizado encuestas de las mismas aplicaciones a un número elevado de personas. Con estos datos, hemos podido establecer una comparación de los resultados obtenidos en ambos estudios para realizar una posterior conclusión de los mismos.Escuela Técnica Superior de Ingeniería de Telecomunicació

A QoE-driven Vertical Handover Management Framework for Multimedia Services over Wireless Networks

With advances in wireless technology and mobile devices, the number of mobile users using multimedia services has increased significantly in recent years. Mobile devices can be connected and roam on heterogeneous wireless networks. The IEEE 802.21 group has designed a Media Independent Handover (MIH) standard to ensure seamless Vertical Handover (VHO) in heterogeneous networks. However, the standard currently depends on features of the network (e.g. the type of network and available bandwidth) to achieve seamless VHO. This approach is limited, as it does not consider how a Quality of Experience (QoE) can be provided and maintained for customers when delivering multimedia services in heterogeneous wireless networks. The aim of the project is to develop a novel QoE-driven VHO management framework for providing and maintaining an appropriate level of QoE of multimedia services as the mobile user’s actual requirements in heterogeneous wireless networks. A QoE-driven VHO algorithm is more efficient for maintaining this acceptable QoE of multimedia services than traditional network-based or QoS-based VHO algorithms. There are three main contributions during this project. Firstly, A thorough evaluation of the performance of voice and video services via Skype was carried out in terms of the QoE metric (i.e. MOS). This work identified the impact of video content and packet loss on the QoE metric for voice and video communication services over wireless networks. Secondly, a QoE-driven VHO algorithm was developed to provide and maintain an acceptable QoE of mobile video services for mobile users. Compared to a traditional network-based VHO algorithm, this algorithm can provide better QoE and maintain acceptable QoE. Lastly, the User-centric QoE-driven (UCQoE) VHO framework to provide satisfactory QoE of multimedia services according to the mobile user’s requirements. The framework allows users to set their own preferences (e.g. quality-guarantee or cost-free) and carry out VHO operations accordingly. The evaluation showed that the proposed framework can provide a better QoE for delivered video services than QoS-based and network-based VHO algorithms. Furthermore, the proposed framework can be used to avoid unnecessary cost of mobile data when the option of cost-free is preferred by the user. During this project, three international conference papers had been published and a journal paper has been submitted to IEEE Transactions on Mobile Computing. The main contribution-UCQoE VHO management framework can be developed to maintain QoE of all mobile services in the future

Cognitive Radio Systems

Cognitive radio is a hot research area for future wireless communications in the recent years. In order to increase the spectrum utilization, cognitive radio makes it possible for unlicensed users to access the spectrum unoccupied by licensed users. Cognitive radio let the equipments more intelligent to communicate with each other in a spectrum-aware manner and provide a new approach for the co-existence of multiple wireless systems. The goal of this book is to provide highlights of the current research topics in the field of cognitive radio systems. The book consists of 17 chapters, addressing various problems in cognitive radio systems

Πλαίσιο Υποστήριξης Αποφάσεων για την Αξιολόγηση και Προώθηση Δυναμικών Δικτύων Επιχειρήσεων

Η παρούσα διδακτορική διατριβή με τίτλο «Πλαίσιο Υποστήριξης Αποφάσεων για την Αξιολόγηση και Προώθηση Δυναμικών Δικτύων Επιχειρήσεων» εστιάζει στο πεδίο των δικτύων παραγωγής, η εγκαθίδρυση των οποίων κερδίζει διαρκώς έδαφος, ως μετεξέλιξη των παραδοσιακών αλυσίδων εφοδιασμού. Αντικείμενο της διατριβής αποτελεί πιο συγκεκριμένα η μελέτη και διερεύνηση της έννοιας των Δυναμικών Δικτύων Παραγωγής, ενός νέου τύπου σχηματισμών παραγωγής που βασίζεται στη συνεργασία και τη διαφάνεια, με απώτερο στόχο την αξιολόγηση και προώθηση της αποδοχής και υιοθέτησής τους από τις επιχειρήσεις παραγωγής ως απόκριση στις απαιτήσεις του σύγχρονου επιχειρηματικού περιβάλλοντος. Η συμβολή της διατριβής της διατριβής εντοπίζεται σε δύο επίπεδα, εκείνα: •Tης θεώρησης και ποιοτικής διερεύνησης ως προς τα οφέλη και τους κινδύνους μιας πρωτοποριακής και πολλά υποσχόμενης προσέγγισης οργάνωσης και λειτουργίας σχηματισμών συνεργατικών δικτύων παραγωγής. Η εν λόγω προσέγγιση μοντελοποιεί όλες τις φάσεις του κύκλου ζωής τους και επιτρέπει την από άκρο σε άκρο και σε πραγματικό χρόνο διαχείριση αυτών στη βάση ενός παραμετροποιήσιμου μοντέλου μεταδεδομένων και αρχιτεκτονικών λύσεων, προσανατολισμένων στις υπηρεσίες που καθιστούν δυνατή τη διασφάλιση διαλειτουργικότητας και αυξημένων επιπέδων συνεργασίας μεταξύ των εμπλεκόμενων εταίρων. •Της ανάλυσης, μοντελοποίησης και αξιολόγησης του αντίκτυπου της υιοθέτησης του μοντέλου παραγωγής που αντιπροσωπεύουν οι εν λόγω σχηματισμοί σε όρους επίδοσης και ρίσκου με τη βοήθεια των Ασαφών Γνωστικών Δικτύων και κατ’ επέκταση τη συμμετοχή εμπειρογνωμόνων. Συνολικά, η διατριβή θέτει τα θεμέλια για την εισαγωγή ενός νέου, εύρωστου μοντέλου παραγωγής και παρέχει το πλαίσιο για την τεκμηρίωση των αποτελεσμάτων της λειτουργίας του, συμβάλλοντας ως εκ τούτου στη δημιουργία ενός αισθήματος εμπιστοσύνης, προτού μια επιχείρηση επενδύσει και προβεί ουσιαστικά στην υιοθέτησή του στην πράξη