Αλγόριθμος Μετάδοσης Πολυμέσων Self-Clocked Rate Adaptation for Multimedia (SCReAM)

Στην Πτυχιακή Εργασία αυτή παρουσιάζεται μια μελέτη για τον αλγόριθμο ελέγχου συμφόρησης Self-Clocked Rate Adaptation for Multimedia (SCReAM). Αρχικά, αναλύθηκε το πρόβλημα που καλείται να αντιμετωπίσει το SCReAM καθώς και οι τεχνολογίες και πρωτόκολλα που χρησιμοποιεί για να λειτουργήσει. Στη συνέχεια, παρουσιάζονται τα τρία στάδιά του, ο έλεγχος συμφόρησης δικτύου, ο έλεγχος μετάδοσης αποστολέα και ο έλεγχος ρυθμού πολυμέσων. Στη συνέχεια, αναλύεται σε μεγαλύτερο βάθος η λειτουργία του αλγορίθμου, τόσο από την πλευρά του αποστολέα δεδομένων, όπου και συγκεντρώνεται η περισσότερη λειτουργικότητα του αλγορίθμου, όσο και από την πλευρά του παραλήπτη. Παρατίθενται κάποια αποτελέσματα προσομοιώσεων και δοκιμών, που παρουσιάζονται στη βιβλιογραφία, τα οποία ερευνούν το αν ο αλγόριθμος πράγματι κάνει αυτά που υπόσχεται. Στη συνέχεια, πραγματοποιείται μια γενική περιγραφή κάποιων ανταγωνιστικών αλγορίθμων του SCReAM και παρουσιάζεται μια γενική σύγκριση μεταξύ αυτών. Επίσης, ερευνάται το αν και με ποιον τρόπο θα μπορούσε το SCReAM να ενταχθεί στην τεχνολογία 5G. Τέλος, αναφέρονται κάποιοι προβληματισμοί σχετικά με την λειτουργία του SCReAM και παρουσιάζονται τα συμπεράσματα που προέκυψαν από την όλη μελέτη.At this undergraduate thesis a study for the congestion control algorithm "Self-Clocked Rate Adaptation for Multimedia (SCReAM)" is presented. The problem that SCReAM has to face is being analyzed at the beginning, and the protocols and technologies that SCReAM uses for its function are referred. Afterwards, the three levels of the algorithm (network congestion control, sender transmission control, media rate control) are being described. Moreover, experiment results of the use of SCReAM, taken by the bibliography, are being presented. Also, a description of some competitive algorithms of SCReAM, a short comparison between them and a sample of SCReAM's use in 5G technologies is being displayed. After all, some concerns about using SCReAM are being presented and a conclusion of the whole study is being made

DyPS: Dynamic Processor Switching for Energy-Aware Video Decoding on Multi-core SoCs

In addition to General Purpose Processors (GPP), Multicore SoCs equipping modern mobile devices contain specialized Digital Signal Processor designed with the aim to provide better performance and low energy consumption properties. However, the experimental measurements we have achieved revealed that system overhead, in case of DSP video decoding, causes drastic performances drop and energy efficiency as compared to the GPP decoding. This paper describes DyPS, a new approach for energy-aware processor switching (GPP or DSP) according to the video quality . We show the pertinence of our solution in the context of adaptive video decoding and describe an implementation on an embedded Linux operating system with the help of the GStreamer framework. A simple case study showed that DyPS achieves 30% energy saving while sustaining the decoding performanc

System Support for Bandwidth Management and Content Adaptation in Internet Applications

This paper describes the implementation and evaluation of an operating system module, the Congestion Manager (CM), which provides integrated network flow management and exports a convenient programming interface that allows applications to be notified of, and adapt to, changing network conditions. We describe the API by which applications interface with the CM, and the architectural considerations that factored into the design. To evaluate the architecture and API, we describe our implementations of TCP; a streaming layered audio/video application; and an interactive audio application using the CM, and show that they achieve adaptive behavior without incurring much end-system overhead. All flows including TCP benefit from the sharing of congestion information, and applications are able to incorporate new functionality such as congestion control and adaptive behavior.Comment: 14 pages, appeared in OSDI 200

High-Speed Communications Over Polymer Optical Fibers for In-Building Cabling and Home Networking

This paper focuses on high-speed cabling using polymer optical fibers (POF) in home networking. In particular, we report about the results obtained in the POF-ALL European Project, which is relevant to the Sixth Framework Program, and after two years of the European Project POF-PLUS, which is relevant to the Seventh Framework Program, focusing on their research activities about the use of poly-metyl-metha-acrilate step-index optical fibers for home applications. In particular, for that which concerns POF-ALL, we will describe eight-level pulse amplitude modulation (8-PAM) and orthogonal frequency-division multiplexing (OFDM) approaches for 100-Mb/s transmission over a target distance of 300 m, while for that which concerns POF-PLUS, we will describe a fully digital and a mixed analog-digital solution, both based on intensity modulation direct detection, for transmitting 1 Gb/s over a target distance of 50 m. The ultimate experimental results from the POF-ALL project will be given, while for POF-PLUS, which is still ongoing, we will only show our most recent preliminary results

End to end architecture and mechanisms for mobile and wireless communications in the Internet

Architecture et mécanismes de bout en bout pour les communications mobiles et sans fil dans l'Internet. La gestion performante de la mobilité et l'amélioration des performances des couches basses sont deux enjeux fondamentaux dans le contexte des réseaux sans fil. Cette thèse apporte des solutions originales et innovantes qui visent à répondre à ces deux problématiques empêchant à ce jour d'offrir des possibilités de communication performantes et sans couture aux usagers mobiles accédant à l'Internet via des réseaux d'accès locaux sans fil (WLAN). Ces solutions se distinguent en particulier par l'impact minimum qu'elles ont sur les protocoles standards de l'Internet (niveaux transport et réseau) ou de l'IEEE (niveaux physique et liaison de données). S'inscrivant dans les paradigmes de "bout en bout" et "cross-layer", notre architecture permet d'offrir des solutions efficaces pour la gestion de la mobilité : gestion de la localisation et des handover en particulier. En outre, nous montrons que notre approche permet également d'améliorer l'efficacité des transmissions ainsi que de résoudre efficacement plusieurs syndromes identifiés au sein de 802.11 tels que les anomalies de performance, l'iniquité entre les flux et l'absence de contrôle de débit entre la couche MAC et les couches supérieures. Cette thèse résout ces problèmes en combinant des modèles analytiques, des simulations et de réelles expérimentations. Ces mécanismes adaptatifs ont été développés et intégrés dans une architecture de communication qui fournit des services de communication à haute performance pour réseaux sans fils tels que WIFI et WIMAX. ABSTRACT : Wireless networks, because of the potential pervasive and mobile communication services they offer, are becoming the dominant Internet access networks. However, the legacy Internet protocols, still dominant at that time, have not been designed with mobility and wireless in mind. Therefore, numerous maladjustments and “defaults of impedance” can be observed when combining wireless physical and MAC layers with the traditional upper layers. This thesis proposes several solutions for a pacific coexistence between these communication layers that have been defined and designed independently. Reliable mobility management and Low layer performance enhancements are two main challenging issues in the context of wireless networks. Mobility management (which is mostly based on mobile IP architecture nowadays) aims to continuously assign and control the wireless connections of mobile nodes amongst a space of wireless access networks. Low layer performance enhancements mainly focus on the transmission efficiency such as higher rate, lower loss, interference avoidance. This thesis addresses these two important issues from an original and innovative approach that, conversely to the traditional contributions, entails a minimum impact on the legacy protocols and internet infrastructure. Following the “end to end” and “cross layer” paradigms, we address and offer efficient and light solutions to fast handover, location management and continuous connection support through a space of wireless networks. Moreover, we show that such an approach makes it possible to enhance transmission efficiency and solve efficiently several syndromes that plague the performances of current wireless networks such as performance anomaly, unfairness issues and maladjustment between MAC layer and upper layers. This thesis tackles these issues by combining analytical models, simulations and real experiments. The resulting mechanisms have been developed and integrated into adaptive mobility management communication architecture that delivers high performing communication services to mobile wireless systems, with a focus on WIFI and WIMAX access networks

Just Queuing: Policy-Based Scheduling Mechanism for Packet Switching Networks

The pervasiveness of the Internet and its applications lead to the potential increment of the users’ demands for more services with economical prices. The diversity of Internet traffic requires some classification and prioritisation since some traffic deserve much attention with less delay and loss compared to others. Current scheduling mechanisms are exposed to the trade-off between three major properties namely fairness, complexity and protection. Therefore, the question remains about how to improve the fairness and protection with less complex implementation. This research is designed to enhance scheduling mechanism by providing sustainability to the fairness and protection properties with simplicity in implementation; and hence higher service quality particularly for real-time applications. Extra elements are applied to the main fairness equation to improve the fairness property. This research adopts the restricted charge policy which imposes the protection of normal user. In terms of the complexity property, genetic algorithm has an advantage in holding the fitness score of the queue in separate storage space which potentially minimises the complexity of the algorithm. The integrity between conceptual, analytical and experimental approach verifies the efficiency of the proposed mechanism. The proposed mechanism is validated by using the emulation and the validation experiments involve real router flow data. The results of the evaluation showed fair bandwidth distribution similar to the popular Weighted Fair Queuing (WFQ) mechanism. Furthermore, better protection was exhibited in the results compared with the WFQ and two other scheduling mechanisms. The complexity of the proposed mechanism reached O(log(n)) which is considered as potentially low. Furthermore, this mechanism is limited to the wired networks and hence future works could improve the mechanism to be adopted in mobile ad-hoc networks or any other wireless networks. Moreover, more improvements could be applied to the proposed mechanism to enhance its deployment in the virtual circuits switching network such as the asynchronous transfer mode networks

Dynamic Window-Constrained Scheduling for Real-Time Media Streaming

This paper describes an algorithm for scheduling packets in real-time multimedia data streams. Common to these classes of data streams are service constraints in terms of bandwidth and delay. However, it is typical for real-time multimedia streams to tolerate bounded delay variations and, in some cases, finite losses of packets. We have therefore developed a scheduling algorithm that assumes streams have window-constraints on groups of consecutive packet deadlines. A window-constraint defines the number of packet deadlines that can be missed in a window of deadlines for consecutive packets in a stream. Our algorithm, called Dynamic Window-Constrained Scheduling (DWCS), attempts to guarantee no more than x out of a window of y deadlines are missed for consecutive packets in real-time and multimedia streams. Using DWCS, the delay of service to real-time streams is bounded even when the scheduler is overloaded. Moreover, DWCS is capable of ensuring independent delay bounds on streams, while at the same time guaranteeing minimum bandwidth utilizations over tunable and finite windows of time. We show the conditions under which the total demand for link bandwidth by a set of real-time (i.e., window-constrained) streams can exceed 100% and still ensure all window-constraints are met. In fact, we show how it is possible to guarantee worst-case per-stream bandwidth and delay constraints while utilizing all available link capacity. Finally, we show how best-effort packets can be serviced with fast response time, in the presence of window-constrained traffic