Video-on-Demand Broadcasting Protocols: a Comprehensive Study

Broadcasting protocols are proved to be efficient for transmitting most of the popular videos in video-on-demand systems. We propose a generalized analytical approach to evaluate the efficiency of the broadcasting protocols and derive the theoretical lower bandwidth requirement bound for any periodic broadcasting protocols. By means of the proposed analytical tool temporal-bandwidth map, the approach can be used to direct the design of periodic broadcasting protocols to achieve different goals, e.g., server bandwidth requirement, client waiting time, client I/O bandwidth requirement etc. As the most important performance index in VOD system is the required server bandwidth, we give the solution to achieve the optimal bandwidth efficiency given client waiting time requirement and the length of the video. To take into account the popular compressed video with variable bit rate, the optimal approach is applied readily to the VBR videos and can achieve zero loss and best bandwidth efficiency. We give proof why existing techniques such as smoothing and prefetching is not necessary and in some cases inefficient in broadcasting protocols. We also discuss how broadcasting schemes can be tailored to support true and interactive VOD service. An insightful comparison between broadcasting and multicasting schemes is also given in this paper.