Optimizing Video-on-Demand Service with Enhanced Harmonic Broadcasting

1. Harmonic Broadcasting for Video-on-Demand ServiceEnhanced 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. S1 S2 S3 S4 d 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

5. Harmonic Broadcasting Scheme • Parameters • The ith segment of the movie Si is equally divided into i sub-segment(s) {Si, 1, Si, 2 --- Si, 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 d The total bandwidth(B) allocated for the movie is as follows: Where HN is called the harmonic number of N B = b + b/2 + b/3 + b/4 = 2.083b HN = 1 + 1/2 + 1/3 + 1/4 = 2.083

7. d1 d2 d3 d4 S1 S2, 1 S2, 1 S2, 2 S3, 1 S3, 1 S3, 2 S3, 2 S3, 3 S4, 1 S4, 1 S4, 2 S4, 2 S4, 3 S4, 3 S4, 4 Harmonic Broadcasting Scheme t0

8. Waiting Time vs. Bandwidth Allocation • If we allocate HN = 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 S1 from C1 is t0. During t0 + (i - 1)*d to t0 + i * d , the sub-segments(s) that come from Ci+1, …, CN, need to be buffered. Increased data size Output data size buffer size required at t0 + 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. ( HN = 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 thebandwidth 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) {Si, 1, …Si, f+i-1}. Put the f +i-1 sub-segment(s) of Si on a logical channel Ci. The bandwidth of Ci 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 d0 d: the consumption time of a data segment The actual bandwidth we allocate for the movie is

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 S1. • 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  = 1.5, f = 1  = 2.0, f = 3 Original harmonic scheme

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

21. 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