1. Harmonic Broadcasting for Video-on- Demand Service Enhanced Harmonic Data Broadcasting And Receiving Scheme For Popular Video Service Li-Shen Juhn and Li-Ming Tseng, Department of Computer Science and Information Engineering National Central University

2. Introduction In conventional broadcasting scheme, each movie is transmitted sequentially on a video channel. –Suppose there is a popular movie which length is 120 minutes. If we can allocate 4 video channels to broadcast this movie periodically, the viewers waiting time can be reduce to less than 30 minutes.

3. Introduction Harmonic broadcasting is a scheme, which can reduce the access time to 4 minutes as we allocate 4 video channels for a 120- minute movie

4. Harmonic Broadcasting Scheme Parameters: –Movie length --- D (e.g., 120 minutes) –Consumption rate of the movie --- b (e.g., 10Mbps) –Size of the movie --- S = D*b –The movie is equally divide into N segments, and Si is the ith segment of the movie. –Viewer waiting time --- d d = D / N D Bandwidth = b S1S1 S2S2 S3S3 S4S4 d

5. Harmonic Broadcasting Scheme Parameters –The ith segment of the movie Si is equally divided into i sub-segment(s) {S i, 1, S i, 2 --- S i, i } –Let the i sub-segment(s) of Si be put on a logical channel Ci, the bandwidth of Ci is b/i.

6. Harmonic Broadcasting Scheme The total bandwidth(B) allocated for the movie is as follows: Where H N is called the harmonic number of N d B = b + b/2 + b/3 + b/4 = 2.083b H N = 1 + 1/2 + 1/3 + 1/4 = 2.083

7. Harmonic Broadcasting Scheme S1S1 S 2, 1 S 3, 1 S 4, 1 d1d1 S 2, 1 d2d2 S 3, 2 S 4, 2 S 2, 2 t0t0 d3d3 S 3, 1 S 4, 3 S 3, 3 S 3, 2 S 4, 4 S 4, 1 S 4, 2 S 4, 3 d4

8. Waiting Time vs. Bandwidth Allocation If we allocate H N = 4 video channels to broadcast a popular movie, we have N = 30. Suppose the length of the movie is 120 minutes. The waiting time will be 120/30 = 4 minutes.

9. Storage Requirements at Client End Suppose the time that we begin to load the S 1 from C 1 is t 0. During t 0 + (i - 1)*d to t 0 + i * d, the sub-segments(s) that come from C i+1, …, C N, need to be buffered. Increased data size Output data size buffer size required at t 0 + i * d

10. Storage Requirements at Client End

11. Introduction of Enhanced Harmonic Data Broadcasting Scheme In the previous harmonic broadcasting scheme, however, in some cases, the bandwidth utilization can not achieve 100% –Suppose there are 2 free video channels, the harmonic scheme can only use about 92% of the bandwidth. ( H N = 2  N = 3  1 + ½ + 1/3 = 1.83, 1.83/2 = 0.92 )

12. Introduction of Enhanced Harmonic Data Broadcasting Scheme For a given bandwidth, the enhanced scheme can improve the bandwidth utilization and reduce further the maximum delay, the average delay of the viewers’ waiting time.

13. Enhanced Harmonic Broadcasting Scheme Parameters –Movie Length --- D (e.g., 120 minutes) –Consumption rate of the movie is b (e.g., 10Mbps) –The size of the movie is S = D * b –Suppose the bandwidth that we can allocate for the movie is B =  * b,   1 (e.g., B = 15 Mbp,  = 1.5)

14. Enhanced Harmonic Broadcasting Scheme Steps –Step1 Select an integer f (starting index: enhanced factor) and to find the maximum possible integer e (end index) to let –Step2 Equally divide the movie into N segments, where N = e – f + 1

15. Enhanced Harmonic Broadcasting Scheme Step3 –The ith segment Si is equally divide into f +i-1 sub-segment(s) {S i, 1, …S i, f+i-1 }. Put the f +i-1 sub-segment(s) of Si on a logical channel C i. The bandwidth of C i is b / (f+i-1) For a given bandwidth, if we select f = 1, the scheme works exactly the same as the original harmonic broadcasting scheme

16. Enhanced Harmonic Broadcasting Scheme The actual bandwidth we allocate for the movie is d: the consumption time of a data segment d0d0

17. Analysis And Comparison Viewer’s waiting time and bandwidth utilization –Before we can start to consume the required movie, we need to download f – 1 sub-segment(s) of S 1.  min = (f – 1) * d  max = f * d  ave = (  min +  max) / 2 Uncertainty delay  =  max -  min = d –For a given bandwidth B, we only allocate B’ to broadcast the movie. The bandwidth utilization is,

18. Analysis And Comparison – The Effect of the Enhanced Factor : f For a given bandwidth, we find that both maximum delay and the delay uncertainty will reduce as we increase the enhanced factor f. f = 1 (original harmonic broadcasting scheme) f = 2

19. Analysis And Comparison – The Effect of the Enhanced Factor : f However, increase f can not always reduce the average delay Original harmonic scheme  = 1.5, f = 1  = 2.0, f = 3

20. Analysis And Comparison – The Effect of the Enhanced Factor : f

22. Conclusion Harmonic and enhanced harmonic scheme has been proved to be optimal with respect to the bandwidth requirement and the viewers’ waiting time