Design and analysis of hybrid multimedia-on-demand systems

Abstract

Broadband networks are currently able to support high‐bandwidth applications such as multimedia‐on‐demand (MoD) with a specified Quality‐of‐Service (QoS) guarantee. Using MoD services, clients can view video programs, listen to audio programs, and play online‐games anytime, anywhere on the Internet. Multimedia programs are delivered from a content server in an MoD network to the client's device (such as a personal computer, notebook, PDA, mobile phone, etc.) when the service is requested. In the content server, storage capacity and stream transmission capacity are limited resources. The challenge for the service provider is to obtain the highest possible revenue from the MoD system with limited resources while maintaining the QoS to satisfy clients. This thesis addresses this challenge. Interactive, batch and broadcast are the three common ways of providing MoD services. Interactive service provides each client with a dedicated stream to transmit content. With it, the client can use VCR function controls such as pause, forward and rewind. However, the type of service is expensive and does not scale well with user population. For batch service, clients who request the same multimedia content within a batch period are grouped together and served by a single dedicated transmission stream. Hence, the system can use fewer streams to serve more clients. However, batch users must wait for their programs to start and are unable to perform VCR control functions. For broadcast service, the system reserves the necessary streams for serving content in each broadcast cycle. However, a stream will be wasted if no requests choose that content within the broadcast cycle. In this thesis, we study a hybrid MoD system which combines two or three service types so that we can take advantage of those individual services to improve system performance and QoS. In addition, we propose a new incentive charging scheme to encourage clients to select batch service as compensation for the startup latency and lack of VCR functions on the batch service for a system providing 2 types of service for clients' selection in each item of stored content. Moreover, we study different approaches to improving the system performance of the proposed hybrid MoD system with 3 types of services. Furthermore, a stream reservation scheme is proposed for hybrid MoD systems with 2 types of service. In this scheme, some unoccupied streams will be reserved to serve only interactive requests and batch requests with a large group of batch queues during a stream starving stage in order to increase the system efficiency. Furthermore, we consider a more realistic model for MoD systems with the feature of service retrial in which some blocked clients are allowed to retry the system and request the service again. Analytical models will be developed for design, analysis and dimensioning of the proposed hybrid MoD systems and the models will be validated by computer simulation. Numerical results show that the hybrid MoD system with the stream reservation scheme can generate higher revenue by serving more concurrent clients and decrease the average waiting time. And, the hybrid MoD system with service retrial model can generate higher revenue at the expense of increasing the average waiting time.