1. 1 Dynamic Skyscraper broadcasts for Video-on-demand Derek L. Eager and Mary K. Vernon

2. 2 Outline Introduction Introduction Skyscraper Broadcast Skyscraper Broadcast Dynamic Scheduling of Skyscraper Broadcasts Dynamic Scheduling of Skyscraper Broadcasts Experimental Results Experimental Results Conclusion Conclusion

3. 3 Introduction Divide objects to Two set (hot and cold) Divide objects to Two set (hot and cold) Hot Set : SB Hot Set : SB Cold Set : FCFS Cold Set : FCFS The particular objects (hot set) that are most popular may change with the time of day The particular objects (hot set) that are most popular may change with the time of day Dynamically scheduling all objects on all available channels Dynamically scheduling all objects on all available channels

4. 4 Skyscraper Broadcasts Constraint Constraint For any initial unit segment broadcast, there must be a sequence of segments that the client can receive that will support continuous playback to the viewer For any initial unit segment broadcast, there must be a sequence of segments that the client can receive that will support continuous playback to the viewer Clients are required to receive data on no more than two channels simultaneously Clients are required to receive data on no more than two channels simultaneously

5. 5 Skyscraper Broadcasts Progression Progression we use W to restrict the segments from becoming too large. we use W to restrict the segments from becoming too large. EX ： W= 12 EX ： W= 12 [ 1, 2, 2, 5, 5, 12, 12, 12, 12 … ] [ 1, 2, 2, 5, 5, 12, 12, 12, 12 … ]

6. 6 Skyscraper Broadcasts a bb Channel 0 Channel 1 Channel 2 a bb aaa Playback 456123 456123 Case 1Case 2

7. 7 Skyscraper Broadcasts A BB BB Channel 0 Channel 1 Channel 2 Playback 456123 Channel 3 A A A A A

8. 8 Dynamic Scheduling of Skyscraper Broadcasts Skyscraper Transmission Clusters Skyscraper Transmission Clusters The Basic Dynamic Scheme The Basic Dynamic Scheme Temporary Channel Stealing Temporary Channel Stealing

9. 9 Skyscraper Transmission Clusters Non-Overlapping transmission cluster Non-Overlapping transmission cluster SB => K Channels SB => K Channels DSB => Transmission Cluster DSB => Transmission Cluster Start with earliest reception sequence Start with earliest reception sequence Each new cluster begins on channel 0 precisely W unit after the previous sequence Each new cluster begins on channel 0 precisely W unit after the previous sequence

10. 10 Skyscraper Transmission Clusters

11. 11 The Basic Dynamic Scheme The segment size progression is the same as Skyscraper broadcast The segment size progression is the same as Skyscraper broadcast All channels be organized into N groups of K channels each All channels be organized into N groups of K channels each A new transmission cluster starts on different group every (W x T1)/N A new transmission cluster starts on different group every (W x T1)/N Request that require a new transmission cluster are scheduled in FCFS Request that require a new transmission cluster are scheduled in FCFS

12. 12 The Basic Dynamic Scheme 21112 211 21112 211 2 2 2 2 W=4 N=4 ? GROUP 1 GROUP 2 3 3 Channel 0 Channel 1 Channel 0 Channel 1......

13. 13 Temporary Channel Stealing Optimization of dynamic skyscraper scheme Optimization of dynamic skyscraper scheme The requests in an active transmission cluster can only be served early if The requests in an active transmission cluster can only be served early if 1) the two unit broadcast on channel 1 will begin at the same time as the next unit segment broadcast in their group 1) the two unit broadcast on channel 1 will begin at the same time as the next unit segment broadcast in their group 2) channel 1 in the transmission cluster that is doing the stealing is ready 2) channel 1 in the transmission cluster that is doing the stealing is ready

14. 14 Temporary Channel Stealing 12 12 1 1 Channel 0 Channel 1 Channel 2 Channel 3 2 3 3 2 3

15. 15 Transmission Clusters definition definition (1) Use the same segment broadcast on channel K (1) Use the same segment broadcast on channel K (2) Do not use any broadcast periods on channels 0 through K-1 that are in the next transmission cluster (2) Do not use any broadcast periods on channels 0 through K-1 that are in the next transmission cluster The diagonally striped segment on channel 0 are not a member of any transmission cluster The diagonally striped segment on channel 0 are not a member of any transmission cluster

16. 16 Alternative Segment Size Progressions additional requirements additional requirements The relative segment size on channels 1 and 2 is two The relative segment size on channels 1 and 2 is two The segment size increases by at most a factor of three at each other step in progression The segment size increases by at most a factor of three at each other step in progression The transmission cluster of width W on a given channel k>0 starts just after channel k- 1 broadcasts its first segment of the transmission cluster The transmission cluster of width W on a given channel k>0 starts just after channel k- 1 broadcasts its first segment of the transmission cluster

17. 17 Alternative Segment Size Progressions Example Example A(1,2,2,4,4,8,8,16,16 … ) A(1,2,2,4,4,8,8,16,16 … ) B(1,2,2,6,6,12,12,24,24 … ) B(1,2,2,6,6,12,12,24,24 … ) C(1,2,2,6,6,12,12,36,36) C(1,2,2,6,6,12,12,36,36) A is the fastest increasing progression that avoids holes between transmission clusters and that also requires simultaneous reception on at most two channels A is the fastest increasing progression that avoids holes between transmission clusters and that also requires simultaneous reception on at most two channels

18. 18 Alternative Segment Size Progressions

19. 19 Alternative Segment Size Progressions The storage requirement for the new progressions is W – 1 (occurs W-1 time units after the first unit-segment broadcast) The storage requirement for the new progressions is W – 1 (occurs W-1 time units after the first unit-segment broadcast) The new segment size progression also simplify the server disk layout problem The new segment size progression also simplify the server disk layout problem

20. 20 Experimental Results We consider systems in which objects are divided two classes (hot set and cold set) We consider systems in which objects are divided two classes (hot set and cold set) Static sky/FCFS Static sky/FCFS Dynamic sky/FCFS Dynamic sky/FCFS Dynamic sky/Dynamic sky Dynamic sky/Dynamic sky SB progression:{ 1, 2, 2, 5, 5, 12, 12 … } SB progression:{ 1, 2, 2, 5, 5, 12, 12 … } DSB progression:{1, 2, 2, 4, 4, 8, 8 … ) DSB progression:{1, 2, 2, 4, 4, 8, 8 … )

21. 21 Experimental Results

22. 22 Conclusion Performance better than skyscraper broadcast (average client waiting time) Performance better than skyscraper broadcast (average client waiting time) The new progression improve dynamic scheduling, simplify disk layout, and all clients with inexpensive settops to receive the skyscraper broadcasts The new progression improve dynamic scheduling, simplify disk layout, and all clients with inexpensive settops to receive the skyscraper broadcasts