QoP-Driven Scheduling for MPEG Video Decoding

MPEG video decoding algorithm has been embedded into many consumer electronic products. In this paper, we demonstrate that the completion ratio (CR) does not represent well the quality of presentation (QoP) of MPEG video. We then propose a new QoP metric, which 1) is based on frame completion ratio but 2) differentiates firm and soft deadlines and also 3) considers the frame dependency. We show that, on a set of simulated MPEG movies, the proposed QoP metric measures the QoP of the movies much better than the completion ratio. We then present a set of online scheduling algorithms that enhance QoP significantly, particularly for overloaded systems

Survey of Weakly-Hard Real Time Schedule Theory and Its Application

Colloque avec actes et comité de lecture. internationale.International audienceNormally, tasks are classified into real time and non real time according to temporal constraints for the processing and transmitting of these tasks, consequently the worst-case response time and average performance should be focused on them. However, in practical engineering context, partly violated temporal constraints can be tolerated if the violation meets certain distribution. Nevertheless, the loss-rate (within real time region, an instance of a task is regarded as loss if it violates its temporal constraint) under stable state or statistical real time can solve the problem in some extent, it can't include the permitted distribution of violation. For completely solving the problem, weakly-hard real time schedule theory or window-constraint real time schedule theory, which is used to investigate the problem related to allowing violation of instances over a finite range, consecutive instances or a time window, is proposed. In order to effectively utilize the fact that a practical application can tolerate some violations of temporal constraint under certain distribution, the fundamental research must be done from the aspects of specification of temporal constraint, schedule and schedulibility, and implementation, which are explained in detail in this paper

Estudo do gerenciamento de QoS ao nível de sistema operacional para aplicações multimídia distribuídas

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

Scalable Scheduling Support for Loss and Delay Constrained Media Streams

Real-time media servers need to service hundreds and, possibly, thousands of clients, each with their own quality of service (QoS) requirements. To guarantee such diverse QoS requires fast and efficient scheduling support at the server. This paper describes the practical issues concerned with the implementation of a scalable real-time packet scheduler resident on a server, designed to meet service constraints on information transferred across a network to many clients. Specifically, we describe the implementation issues and performance achieved by Dynamic Window-Constrained Scheduling (DWCS), which is designed to meet the delay and loss constraints on packets from multiple streams with different performance objectives. In fact, DWCS is designed to limit the number of late packets over finite numbers of consecutive packets in loss-tolerant and/or delay-constrained, heterogeneous traffic streams. We show how DWCS can be efficiently implemented to provide service guarantees to hundreds of streams. We compare the costs of different implementations, including an approximation algorithm, which trades service quality for speed of execution

Scalable approaches for DiffServ multicasting

Over the last several years, there has been an explosion in the introduction of new Internet technologies. Whereas the Internet in its original form was a medium primarily for academia and research interests, the Internet has been redefined as business and consumer interests have dominated the focal points of Internet technology. The dominant question facing the Internet today is, how can the network meet the needs of the users and their applications while trying to keep such implementations scalable to the billions of users present on the Internet? Two of the emerging technologies for answering the question are Differentiated Services (DiffServ) and multicasting. Although the two technologies share complementary goals, the integration of the two technologies is a non-trivial issue due to three fundamental conflicts. The three fundamental conflicts are the scalability of per-group state information, sender versus receiver-driven QoS, and resource management. The issues surrounding how to solve these conflicts provide the basis for this dissertation.;In this dissertation, two architectures (DiffServ Multicasting (DSMCast) and Edge-Based Multicasting (EBM)) are proposed to satisfy the requirements for scalable DiffServ multicasting architectures. In addition to the two architectures, this dissertation also presents the first in-depth study regarding single tree support for heterogeneous QoS multicasting. Furthermore, the dissertation proposes a novel application of DSMCast for fault tolerance and management of the DiffServ network. Finally, the dissertation comments on future applications of the architectures and proposes several areas for future research

Performance Analysis of RR and FQ Algorithms in Reconfigurable Routers

Currently, we are witnessing a trend in network routers to include reconfigurable hardware structures to provide flexibility at improved performance levels when compared to software-only implementations. This permits the run-time reconfiguration of the hardware resources, i.e., to change their functionality (for example, from one scheduling algorithm to another), to adapt to changing network scenarios. In particular, different scheduling algorithms are more efficient in handling a specific mix of incoming packet traffic in terms of various criteria (e.g., delay, jitter, throughput, and packet loss). Therefore, reconfigurable hardware is able to provide improved performance levels and to allow more efficient algorithms to be utilized when different incoming packet traffic patterns are encountered. This project investigates the possibilities to improve upon end-to-end delays, jitter, throughput, and packet loss by exploiting the availability of a flexible hardware structure such as an field-programmable gate array (FPGA). The aim of the project is to provide an overview on adaptive scheduling using reconfigurable hardware. Consequently, we investigate different scheduling algorithms that provide QoS provisioning for traffic streams that are sensitive to packet delay and jitter, e.g., mpeg video traffic. The investigation utilizes the NS-2 simulator for which we generate realistic network scenarios. Our approach is based on understanding which kind of traffic is passing in the network, and subsequently change the scheduling algorithm accordingly in the core router to meet specific performance requirements. The investigated scheduling algorithms are taken from two well-known families, i.e., Round Robin (RR) and Fair Queuing (FQ). Our investigation confirmed the idea on the behavior of the two investigated scheduling algorithm: WFQ outperforms WRR in terms of end-to-end delay, jitter and throughput but it is more expensive than it at a computational level. Nonetheless, it is possible to find a tradeoff between the required area in FPGA and the level of performance desired for a kind of stream

Packet scheduling strategies for emerging service models in the internet

Traditional as well as emerging new Internet applications such as video-conferencing and live multimedia broadcasts from Internet TV stations will rely on scheduling algorithms in switches and routers to meet a diversity of service requirements desired from the network. This dissertation focuses on four categories of service requirements that cover the vast majority of current as well as emerging new applications: best-effort service, guaranteed service (delay and bandwidth), controlled load service, and soft real-time service. For each of these service types, we develop novel packet scheduling strategies that achieve better performance and better fairness than existing strategies.Best-effort and guaranteed services: A fair packet scheduler designed for best- effort service can also be employed to achieve bandwidth and delay guarantees. This dissertation proposes a novel fair scheduling algorithm, called Greedy Fair Queueing (GrFQ),that explicitly incorporates the goal of achieving better fairness into the actions of the scheduler. A simplified version of the scheduler is also proposed for easier deployment in real networks. Controlled load service: This dissertation analyzes and defines requirements on packet schedulers serving traffic that request the controlled load service (part of the Integrated Services architecture). We then propose a novel scheduler, called the CL(®) scheduler, which provides service differentiation for aggregated traffic for controlled load service. The proposed scheduler satisfies the defined requirements with a very low processing complexity and without requiring per-flow management. Soft real-time service: We formally define the service requirements of soft real-time applications which have delay constraints but which can tolerate some packet losses. Two novel schedulers of different levels of complexity are proposed. These schedulers achieve better performance (lower overall loss rates) and better fairness than previously known schedulers.We adapt a metric used widely in economics, called the Gini index, to our purpose of evaluating the fairness achieved by our schedulers under real traffic conditions. The Gini index captures the instantaneous fairness achieved at most instants of time as opposed to previously used measures of fairness in the networking literature. Using real video, audio and gateway traffic traces, we show that the proposed schedulers achieve better performance and fairness characteristics than other known schedulers.Ph.D., Electrical Engineering -- Drexel University, 200