A Fixed-Delay Broadcasting Protocol for Video-on-Demand

1. A Fixed-Delay Broadcasting Protocol for Video-on-Demand A Channel-Based Heuristic Distribution Protocol For Video-on-Demand Jehan-Francois Paris Department of Computer Science University of Houston Qiong Zhang Department of Computer Science University of Houston

2. Outline • Previous schemes • Fixed-delay pagoda broadcasting • Channel based heuristic distribution • Conclusion

3. Fast broadcasting and Pagoda broadcasting Fast Broadcast Pagoda Broadcast d d C1 C1 S1 S1 S1 S1 S1 S1 S1 S1 S1 S1 C2 C2 S2 S4 S2 S3 S2 S3 S2 S4 S2 S5 S7 S9 C3 S4 S5 S6 S7 C3 S3 S6 S8 S3 1/4 ≥ 1/7 1/6 ≥ 1/7

4. Fixed-delay pagoda broadcasting(FDPB) • It implements a fixed-delay policy that results in lower bandwidth requirements than other pagoda protocols. • It uses a much simpler segment-to-channel mapping.

5. Waiting time • All customers need to wait for a fixed time interval w = md, where m is some integer m ≥ 1 • Previous scheme • Segment Si need to be repeated at least once every i slots • This paper • Segment Si need to be repeated at least once every m+i-1 slots

6. Subchannel • The FDPB protocol partitions each channel Cj into sj subchannels in such a way that slot j of channel Cj belongs to its subchannel j (mod sj). b/3 b/3 b/3

7. Optimal number of subchannels • Let Si be the first segment assigned to channel Cj , then channel Cj is partitioned into subchannels. • For example (m = 9, i = 1) Waiting time = md First segment = S1

8. The first channel for m = 9 1 C1 1/3 Subchannel 0 Subchannel 1 Subchannel 2 S1 =1/9 (needs to be repeated at least once every 9 slots) Repeat 4 segments = (1/3)/4 = 1/12 < 1/9 Repeat 3 segments = (1/3)/3 = 1/9 ≥ 1/9 S1, S2, S3

9. The first channel for m = 9 1 C2 1/3 Subchannel 0 Subchannel 1 Subchannel 2 S4 =1/(9+4-1) = 1/13 (needs to be repeated at least once every 13 slots) Repeat 5 segments = (1/3)/5 = 1/15 < 1/13 Repeat 4 segments = (1/3)/4 = 1/12 ≥ 1/13 S4, S5, S6, S7

10. The first channel for m = 9 1 2 0 S1 S4 S8 S2 S5 S9 S3 S6 S10 S7 S11 S12

11. The second channel for m = 9 1 C1 (m = 9 , i = 13) 1/5 Subchannel 0 Subchannel 1 Subchannel 2 Subchannel 3 Subchannel 4 S13 =1/(9+13-1) = 1/21 (needs to be repeated at least once every 21 slots) Repeat 5 segments = (1/5)/5 = 1/25 < 1/21 Repeat 4 segments = (1/5)/4 = 1/20 ≥ 1/21 S13, S14, S15, S16

12. The second channel for m = 9 3 4 1 2 0 S13 S17 S22 S28 S35 S14 S18 S23 S29 S36 S15 S19 S24 S30 S37 S20 S25 S31 S38 S16 S21 S26 S32 S39 S27 S33 S40 S34 S41 S42

13. Result New Pagoda : 44 seconds 7200 x 9 / 2046 = 32 seconds 7200 x 10 / 2046 = 21.4 seconds

15. 4096 channels

16. Restricting the client bandwidth 1/230 S566 =1/(566+100-1-230) = 1/435 (needs to be repeated at least once every 435 slots)

18. Channel based heuristic distribution (CBHD) • A dynamic broadcasting protocol • Reducing the bandwidth requirements • All customers need to wait for a fixed time interval w = md, where m is some integer m ≥ 1 • Segment Si need to be repeated at least once every m+i-1 slots

19. How many segments? 1 C1 S1 =1/m (needs to be repeated at least once every m slots) Repeat m segments= 1/m S1, S2, …, Sm

20. How many segments? 1 C2 Sm+1 =1/(m+1+m-1) = 1/2m (needs to be repeated at least once every 2m slots) Repeat 2m segments = 1/2m Sm+1, Sm+2, …, S3m

21. CBHD • Channel i will be assigned segments S(si-1-1)m+1 to S(si-1)m • Allocating k channels to a video will allow us to partition a video into (2k-1)m segments.

22. Algorithm

23. If m = 1, k = 4 C1 1 1 C2 2 3 2 3 C3 4 5 6 7 4 5 6 7 C4 8 9 10 12 14 13 15 8 11 9

24. K = 7 channels

25. Conclusion • FDPB make all customers to wait for the same amount of time before watching the video. • FDPB provides the lowest waiting times of all protocol using segments of equal duration and channels of equal bandwidth. • CBHD proposed a dynamic protocol to saving the bandwidth.