1. 1 A Low Bandwidth Broadcasting Protocol for Video on Demand J. Paris, S. W. Carter, D. D. E. Long In Proceedings of ICCCN, 1998

2. 2 Outline Harmonic-base Broadcasting Harmonic-base Broadcasting Polyharmonic Broadcasting Polyharmonic Broadcasting Discuss Discuss Conclusion Conclusion

3. 3 Harmonic Broadcasting (HB) Divide a video into n equally-sized segments Divide a video into n equally-sized segments Each segment Si, for 1 ≤ i ≤ n, is broadcast repeatedly on its own channel with a bandwidth (b / i) Each segment Si, for 1 ≤ i ≤ n, is broadcast repeatedly on its own channel with a bandwidth (b / i) Unfortunately HB does not always deliver all data on time Unfortunately HB does not always deliver all data on time

4. 4 An illustration of the first three streams for a video under harmonic broadcasting Play Rate : b Receive Rate : b/2

5. 5 Harmonic Broadcasting The bandwidth The bandwidth Where H (n) is the harmonic number of n

6. 6 Cautious Harmonic Broadcasting (CHB) The first channel broadcasts S1 repeatedly as before. (bandwidth b) The first channel broadcasts S1 repeatedly as before. (bandwidth b) The second channel alternates between broadcasting S2 and S3 (bandwidth b) The second channel alternates between broadcasting S2 and S3 (bandwidth b) Then the remaining n – 3 channel broadcasting S4 – Sn. (bandwidth b/i) Then the remaining n – 3 channel broadcasting S4 – Sn. (bandwidth b/i)

7. 7 Cautious Harmonic Broadcasting

8. 8 The bandwidth The bandwidth

9. 9 Quasi-harmonic Broadcasting (QHB) The first segment is left intact. The first segment is left intact. The remaining segments Si, for 2 ≤ i ≤ n, is divided up into im-1 fragment, for some positive parameter m. The remaining segments Si, for 2 ≤ i ≤ n, is divided up into im-1 fragment, for some positive parameter m. Slots are also broken up into m equal subslots, and each subslot can be used to broadcast a single fragment. Slots are also broken up into m equal subslots, and each subslot can be used to broadcast a single fragment.

10. 10 Quasi-harmonic broadcasting (m = 4) S1S2,1S2,3S2,5S2,7 ……

11. 11 Quasi-harmonic Broadcasting The key to QHB is that the fragments are not broadcast in order. The key to QHB is that the fragments are not broadcast in order. 1) The last subslot of each slot is used to broadcast the first i -1 fragment 1) The last subslot of each slot is used to broadcast the first i -1 fragment 2) the rest of the fragments are ordered such that the k-th subslot of slot j is used to broadcast fragment ik+j-1 mod i(m-1) +i 2) the rest of the fragments are ordered such that the k-th subslot of slot j is used to broadcast fragment ik+j-1 mod i(m-1) +i

12. 12 Quasi-harmonic Broadcasting The bandwidth The bandwidth

13. 13 Polyharmonic Broadcasting (PHB) 1) it requires that the client STB starts downloading data from the moment a customer requests a specific video instead of waiting until the customer begins watching the beginning of the first segment. 1) it requires that the client STB starts downloading data from the moment a customer requests a specific video instead of waiting until the customer begins watching the beginning of the first segment. 2) polyharmonic broadcasting uses a fixed wait policy. 2) polyharmonic broadcasting uses a fixed wait policy.

14. 14 Polyharmonic Broadcasting Divide into n equal segment (D/n) Divide into n equal segment (D/n) Segment S i at a transmission rate Segment S i at a transmission rate b i = b / (m + i - 1) b i = b / (m + i - 1) No client can start consuming the first segment of the video before having downloaded data from all n streams during a time interval of duration w = md No client can start consuming the first segment of the video before having downloaded data from all n streams during a time interval of duration w = md Segment Si will not be consumed until (m + i – 1 )d time units have elapsed. Segment Si will not be consumed until (m + i – 1 )d time units have elapsed.

15. 15 Polyharmonic Broadcasting (m=2)

16. 16 Polyharmonic Broadcasting The Bandwidth The Bandwidth If n = k * m If n = k * m Since w = md; d= D/n; w = D/k ; k 愈大 則 waiting time 愈小

17. 17 Polyharmonic Broadcasting

18. 18 Polyharmonic Broadcasting

19. 19 Polyharmonic Broadcasting

20. 20 Polyharmonic Broadcasting The Data Receive during time slot i The Data Consume during time slot i

21. 21 Polyharmonic Broadcasting

22. 22 Discussion First, Polyharmonic broadcasting requires m times more streams than other harmonic broadcasting protocols. First, Polyharmonic broadcasting requires m times more streams than other harmonic broadcasting protocols. Second, Polyharmonic broadcasting forces all customers to wait for the maximum waiting delay while other harmonic protocols only require few customers to wait that long. Second, Polyharmonic broadcasting forces all customers to wait for the maximum waiting delay while other harmonic protocols only require few customers to wait that long.

23. 23 Bandwidth vs Average Waiting Time

24. 24 Conclusion We have presented a new broadcasting protocol that provides the same maximum waiting time as the harmonic broadcasting protocol while consuming significantly less bandwidth. We have presented a new broadcasting protocol that provides the same maximum waiting time as the harmonic broadcasting protocol while consuming significantly less bandwidth. But All Client must wait the same time and the two more stream But All Client must wait the same time and the two more stream