Enhancing the multimedia experience in emerging networks

As multimedia processing and networking technologies, products and services evolve, the number of users communicating, collaborating and entertaining over the IP networks is growing rapidly. With the emergence of pervasive and ubiquitous multimedia services, this proliferation creates an abundant increase in the amount of the Internet backbone traffic. This brings the problem of efficient transmission of real-time and time-sensitive media content to the fore. Effective multimedia services demand appropriate application-specific and media-aware solutions, without which the full benefits of such services will not be realized. Poor approaches often lead to system performance degradations such as unacceptable presentation quality perceived by the users, possible network collapses due to the high-bandwidth nature of the multimedia applications, and poor performance observed by other data-oriented applications due to the unresponsiveness of multimedia flows. From a networking perspective, traditional approaches consider the application data as "sacred" and do not differentiate any part of it from the rest. While this keeps the datadelivery mechanisms, namely, the transport-layer protocols, as plain as possible, it also precludes these mechanisms from interpreting the media content and tailoring their actions according to the importance of the content. Given that this naive approach cannot satisfy the specific needs of each and every one of the today's emerging applications ranging from videotelephony to video-on-demand, from distance education to telemedicine, from remote surveillance to online video gaming, the study of Multimedia Transport Protocols (MMTP) is overdue. An MMTP solution basically integrates the multimedia content information into the responsible data-delivery mechanisms along with the requirements of the invoking application and network characteristics to deliver the highest level of service quality. In other words, an MMTP solution offers a unified environment where all cooperating protocol components interact with each other and make the best use of this collaboration to fulfill their respective duties. The focus of this thesis is on the design and evaluation of a set of end-to-end and system-level MMTP solutions for scalable, reliable, and high quality multimedia services in ever-changing, complex and heterogeneous computing and communication environments. The main contributions of this thesis are: (1) To develop an optimal overlay-based multi-path transmission framework for streaming error-resilient videos in low-delay video applications, (2) To analyze the performance of single/multi-hop and single/multi-path transmission methods for streaming high-resolution videos in mesh networks, (3) To formulate a mathematical framework that models on-demand video delivery from multiple content servers, and to develop a rate-distortion optimal packet scheduling algorithm for a multi-server streaming system, (4) To investigate proxy-based solutions to overcome the problems associated with packet loss, large delay and delay jitter in interactive video applications, (5) To characterize the packet dynamics in networked-video applications, to propose models for packet delay, to develop accurate delay and delay-boundary prediction methods, and to interpret the correlation between the packet delay and packet loss events, (6) To engineer media-aware and network-adaptive error-control methods, and to lay out a framework that computes the optimal actions for error control. In addition to providing the mathematics behind these solutions, a considerable emphasis is also given to the real-time implementation issues. We envision a future that will involve richer and more demanding multimedia services, which will be available anywhere and anytime, and accessible from a variety of devices. We anticipate that this thesis will play an enabling role and help establish a solid foundation forthe next generation multimedia services, which will doubtlessly have a great influence on how we communicate and collaborate, teach and learn, conduct business and entertain.