King-Man Ho

Performance Study of Large-Scale Video Streaming Services in Highly Heterogeneous Environment

To support large-scale Video-on-Demand (VoD) services in a heterogeneous network environment, either a replication or layering approach can be deployed to adapt the client bandwidth requirements. With the aid of the broadcasting and caching techniques, it has been proved that the overall performance of the system can be enhanced. In this paper, we explore the impact on the broadcasting schemes coupled with proxy caching and develop an analytical model to evaluate the system performance in a highly heterogeneous network environment. We develop guidelines for resources allocation, transmission strategies as well as caching schemes under different system configurations. The model can assist system designers to study various design options as well as perform system dimensioning. Moreover, a systematic comparison between replication and layering is performed. From the results, it can be seen that the system performance of layering is better than that of replication when the environment is highly heterogeneous even if the layering overhead is higher than 25%. In addition, it is found that the system blocking probability can be further reduced by exploring the broadcast capability of the network if the proxy server cannot store all the popular videos.

Video-on-Demand Systems With Cooperative Clients in Multicast Environment

Peer-to-peer (P2P) and multicast approaches are two common transmission strategies to provide scalable and cost efficient solutions for video-on-demand (VoD) services. The former approach requires small server resources and provides a negligible delay to users, but the bandwidth requirement inside the network will be rapidly increased when more customers join the video session. On the other hand, if the system simply uses a multicast scheme to deliver a video, customers will experience a noticeable delay before watching the video whereas the overall bandwidth requirement will not be significantly increased. In this paper, a new transmission policy denoted peer-to-peer batching (PPB) policy is proposed to efficiently deliver video data in a large scale VoD system by exploiting the multicast capability of the network and P2P paradigm. To avoid the disruption of services, the fault tolerance and recovery mechanism is also developed for PPB. In addition, in order to further improve the scalability of the system, a distributed PPB (DPPP) is also proposed. We then develop a mathematical model to evaluate the performance of each of our proposed policies analytically. Based on this model, system designers are able to study various design options as well as perform system dimensioning. Both analytical and simulation results show that the proposed scheme achieves better system performance compared with existing schemes.

A Simple Model for Peer-to-Peer Video-on-Demand System in Broadcast Environment

In order to provide a cost effective and scalable solution for a large-scale VoD system, a number of system topologies and transmission protocols have been proposed in the literature in the past decade, such as proxy caching, content delivery network (CDN), peer-to-peer (P2P), multicast and periodic broadcast. However, these approaches have their own problems for video delivery. To compensate their disadvantages, in this paper, we develop a hybrid VoD system model that uses a P2P paradigm coupled with video broadcasting and CDN-like approach for video delivery. In the proposed architecture, the video is first partitioned into two parts. The first part of the video is transmitted among customers, watching the video, in P2P manner while the second part of the video is broadcasted periodically by the central server. This content delivery strategy allows the workload of the system disperse over the network while customers can still guarantee to obtain the service without collapsing by the dynamic nature of P2P framework. In addition, it also takes a benefit from video broadcasting. Analytical model is developed to allow system designers better understanding of system dynamics and provide guidelines for the management of design resources and realization of VoD services based on this architecture.

Investigating the Performance of Hierarchical Video-on-Demand System in Heterogeneous Environment

To support large-scale video-on-demand (VoD) services, many transmission schemes such as data broadcasting and proxy caching have been developed to minimize the resources requirement and enhance the system scalability. However, most of the previous works mainly focused on providing the VoD services in a homogeneous environment. In this paper, we investigate a feasible solution for building an efficient hierarchical VoD system using proxy caching coupled with broadcasting and appropriate coding schemes in heterogeneous environment so as to minimize the system transmission cost. By developing a performance model in this paper, system designers can study how various techniques for VoD can be organized to maximize the efficiency of the system. From the results, it can be seen that the system performance can be greatly enhanced by efficiently coupling various techniques.

An Evolutionary Video Assignment Optimization Technique for VOD System in Heterogeneous Environment

We investigate the video assignment problem of a hierarchical Video-on-Demand (VOD) system in heterogeneous environments where different quality levels of videos can be encoded using either replication or layering. In such systems, videos are delivered to clients either through a proxy server or video broadcast/unicast channels. The objective of our work is to determine the appropriate coding strategy as well as the suitable delivery mechanism for a specific quality level of a video such that the overall system blocking probability is minimized. In order to find a near-optimal solution for such a complex video assignment problem, an evolutionary approach based on genetic algorithm (GA) is proposed. From the results, it is shown that the system performance can be significantly enhanced by efficiently coupling the various techniques.

Design of a decentralized video-on-demand system with cooperative clients in multicast environment

Peer-to-Peer (P2P) communications have become a popular alternative solution to provide large-scale video-on-demand (VoD) services. Recent approaches are designed for streaming applications in a unicast infrastructure. As the successful deployment of IP broadcast delivery, the system could have a further improvement when broadcasting scheme can be coupled with P2P paradigm. In this paper, we develop a possible solution for building a VoD system using existing broadcasting protocol coupled with cooperative clients in multicast environment. The objective of this work mainly focuses on addressing one design issue in such framework: reliability. An analytical model is developed to determine the minimum number of cooperative clients required for the system. The results showed that 60 peers, each of which has the availability of 0.4, are enough to leverage the workload of the central server up to 95%, when the startup delay of the system is 10 minutes.

Cooperative Transmission Strategy for Video-on-Demand System

Skyscraper broadcast (SB) is one of the effective ways to provide a scalable solution for video-on-demand (VoD) services. Originally, SB was only designed for supporting a near-VoD service to clients. In this paper, we propose a new transmission scheme called skyscraper-based peer-to-peer broadcasting (SPB) to realize a true-VoD service in SB. It is accomplished by shifting the duty of the first segment transmission to the clients in peer-to-peer (P2P) manner. It is found from the results that the proposed scheme is superior to the existing strategies that the transmission cost of the system and that of the central server can be reduced up to 7% and 30% respectively.

Design of a Peer-to-Peer Video-on-Demand System with the Consideration of Fault Exception

Early departure of customers during video playback brings a great impact on the design of a peer-to-peer (P2P) video-on-demand (VoD) system, especially on the system bandwidth requirement and the need for a well-defined fault exception mechanism. In this paper, we develop an analytical model to evaluate how the system parameters such as bandwidth requirement and batching time in a P2P batching system are affected when early departure behavior is taken into account. In addition, a fault exception mechanism is also proposed. Computer simulations are performed to verify the correctness of the model. The results show that the system resources can be utilized more effectively when the customer departure behavior is captured into the system.