| Summary: | 博士 === 國立中央大學 === 資訊工程研究所 === 87 === Using multiple channels to broadcast a popular video can reduce the viewer''s waiting time to approach video-on-demand service. For a 120-minute movie, conventional broadcasting schemes can support the movie every 30 minutes with 4 video channels. Suppose the set-top box at client end can buffer portions of the playing video on disk. For a given bandwidth, pyramid broadcasting schemes can provide users with shorter waiting time as compared with conventional broadcasting schemes. However, when the bandwidth allocation for each movie is less than 5 video channels, the access time improvements by pyramid schemes are still not significant. For example, the maximum waiting time is still greater than 19 minutes as the bandwidth allocation for each movie is 4 video channels. This thesis presents several improved schemes. They are fast broadcasting scheme, staircase broadcasting scheme, harmonic broadcasting scheme, enhanced harmonic broadcasting scheme, and adaptive fast bandwidth allocation scheme. The harmonic broadcasting scheme can reduce the waiting time to less than 4 minutes for the above case. The enhanced harmonic broadcasting scheme can further reduce the waiting time to about 2 minutes. With the same waiting requirement for a popular movie, all new schemes need much less bandwidth and, thus, greatly save the bandwidth requirements. However, all schemes have a difference of performance. For example, the fast broadcasting scheme can support on-site program. The staircase broadcasting scheme can save the buffer requirements at the client end. The adaptive scheme needs not to predict the popularity of videos. We present the detail analysis and comparison results to show the benefit of each scheme.
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