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

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

Fast broadcasting and Pagoda broadcasting S1 S2S3S2S3 S4S5S6S7 C1 C2 C3 S1 S2S4S2S5 S3S6S8S3 C1 C2 C3 S1 S2S4 S7S9 1/4 ≥ 1/7 1/6 ≥ 1/7 Fast Broadcast Pagoda Broadcast dd

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.

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

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

Optimal number of subchannels Let S i be the first segment assigned to channel C j, then channel C j is partitioned into subchannels. For example ( m = 9, i = 1) Waiting time = md First segment = S 1

The first channel for m = 9 C1C1 Subchannel 0Subchannel 1Subchannel 2 1/3 1 Repeat 4 segments = (1/3)/4 = 1/12 < 1/9 S1, S2, S3 S 1 = 1/9 (needs to be repeated at least once every 9 slots) Repeat 3 segments = (1/3)/3 = 1/9 ≥ 1/9

The first channel for m = 9 C2C2 Subchannel 0Subchannel 1Subchannel 2 1/3 1 S4, S5, S6, S7 S 4 = 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

The first channel for m = 9 S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S

The second channel for m = 9 C1C1 1 (m = 9, i = 13) Subchannel 0Subchannel 1Subchannel 2Subchannel 3Subchannel 4 1/5 Repeat 5 segments = (1/5)/5 = 1/25 < 1/21 Repeat 4 segments = (1/5)/4 = 1/20 ≥ 1/21 S13, S14, S15, S16 S 13 = 1/(9+13-1) = 1/21 (needs to be repeated at least once every 21 slots)

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

Result 7200 x 9 / 2046 = 32 seconds7200 x 10 / 2046 = 21.4 seconds New Pagoda : 44 seconds

4096 channels

Restricting the client bandwidth 1/230 S 566 = 1/( ) = 1/435 (needs to be repeated at least once every 435 slots)

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 S i need to be repeated at least once every m+i-1 slots

How many segments? C1C1 1 Repeat m segments= 1/m S 1 = 1/m (needs to be repeated at least once every m slots) S 1, S 2, …, S m

How many segments? C2C2 1 Repeat 2m segments = 1/2m S m+1 = 1/(m+1+m-1) = 1/2m (needs to be repeated at least once every 2m slots) S m+1, S m+2, …, S 3m

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

Algorithm

If m = 1, k = C1 C2 C3 C4

K = 7 channels

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.