1 A Comparative Study of Periodic Broadcasting Scheme for Large-Scale Video Streaming Prepared by Nera Liu

2 Agenda Introduction Four Dimensions of Design Spaces Periodic Broadcasting Schemes Comparisons Analysis of Design Spaces in Optimal Scheme Customized Optimal Scheme Customized Poly-harmonic Broadcasting Scheme Q & A

3 Introduction TV System –Broadcasting TV programs are pre-scheduled –All viewers enjoy the programs with the same channel Video-on-Demand (VOD) System –Broadcasting video are not pre-scheduled –The viewers request the video on demand –Provides a flexible way of enjoying video Why is there not a large deployment of VOD System?

4 Introduction - Problems TV System Antenna VOD System Viewers Servers Viewers

5 Introduction - Problems Problems –The cost of VOD system increases as the number of viewers increases –The system does not benefit from economical efficiency –It competes with some cheap operating competitors, like video rental shop Solutions –Multicast A group of viewers can share one channel for enjoyment –Reactive solutions It transmits the data in response to the user requests It is suitable to small traffic, say 10 requests/sec Example: Batching, Patching –Proactive solutions It transmits the data with a pre-defined schedule, irregardless of user requests. It is designed for large traffic Example: Periodic Broadcasting Scheme K. A. Hua, Y. Cai, and S. Sheu, "Patching: A Multicast Technique For True Video-on-Demand Services," Proc. 6th International Conference on Multimedia, Sept 1998 Page(s): A. Dan, D. Sitaram, and P. Shahabuddin, "Scheduling Policies for an On-Demand Video Server with Batching," Proc. 2nd ACM International Conference on Multimedia, 1994 Page(s):

6 Notation of Symbols SymbolDescription LThe length of the movie (sec) bThe playback rate of the movie (Mbit/sec) KThe no. of logical channels NThe no. of movie segments DiDi The size of the i-th movie segment measured at the play back rate (sec) BsBs The total server bandwidth (Mbit/sec) DcDc The client access bandwidth (Mbit/sec) CThe client buffer to movie size ratio TThe maximum access latency MThe total no. of movie fifi The movie partition function gigi The bandwidth partition function B Ti The broadcast period of movie segment D i Some of them will be introduced later

7 The simplest - NVOD Near Video-on-Demand (NVOD) The access latency = The client access bandwidth = 1 channel (b Mbit/sec) The client buffer requirement = 0 Mbit A user arrives at time t, the maximum access latency is L/K sec A Movie with length L The movie is broadcasting every L/K sec Time

8 Analysis of Design Spaces Movie Partition Algorithm Bandwidth Partition Algorithm Broadcasting Schedule Reception Schedule

9 Movie Partition Algorithm This governs how to partition the movie into a number of segment The access latency depends on the frequency of the movie broadcast Partition the first portion of movie into small segment, so as to increase the frequency of this small segment broadcast Trade off? –The viewer needs to download movie from more than one logical channel. –The viewer may need buffer. –The scheme must guarantee continuous playback.

10 Bandwidth Partition Algorithm This is an algorithm of how to divide the total server bandwidth into a group of logical channels for broadcasting different movie segments Play a critical factor in server bandwidth requirement and continuous playback in the client Client access bandwidth Vs Client buffer requirement Time to play back the movie segment It does not guarantee continuous playback The movie segment is streamed with high data rate The movie segment is streamed with low data rate The time the viewer enters the system

11 Broadcasting Schedule This schedule governs –The broadcast period of the movie segments –The broadcast schedule on which logical channel broadcasts which movie segments It also play a critical factor in the server bandwidth efficiency and continuous play back. The time the viewer enters the system The time to play back the movie segment D The broadcast period of the movie segment Time

12 Reception Schedule This governs how the viewer receives the movie segments from the logical channels The flexibility of this dimension of design space is due to the server bandwidth inefficiency introduced by the broadcasting schedule. A Movie with length L Time Inefficient NVOD System

13 Pyramid Broadcasting Scheme (PB) Motivation: Movie Partition Algorithm Initiative Movie Partition: –The movie is partitioned according to a geometric series –D i+1 =  D i Bandwidth Partition: –The bandwidth is partitioned equally (control by the parameter  ) The shape of pyramid Time The movie is partitioned with  = 2 Access latency = The size of the first movie segment Client access bandwidth = 2 channels (for  = 2, 4b Mbit/sec) Client buffer requirement = About 90% of movie size S. Viswanathan, and T. Imielinski, "Metropolitan area video-on-demand service using pyramid broadcasting," Multimedia Systems, vol. 4, pp , 1996.

14 Permutation-based Pyramid Broadcasting Scheme (PPB) Motivation: Streaming the segments with low data rate to reduce the client buffer requirement in PB. Movie Partition: –The movie is partitioned according to a geometric series –D i+1 =  D i Bandwidth Partition: –The bandwidth is partitioned equally (control by the parameter  ) –Each logical channel is partitioned into p sub-channels Access latency = The size of the first movie segment Client access bandwidth = 2 channels Client buffer requirement = C.C. Aggarwal, J.L. Wolf, and P.S. Yu, "A permutation-based pyramid broadcasting scheme for video-on-demand systems," IEEE Proceedings of the International Conference on Multimedia Computing and Systems, pp , Jun Time Each logical channel is partitioned into p sub-channels

15 Skyscraper Broadcasting Scheme (SB) Principle: Solve the client buffer requirement in PB by a parameter W Movie Partition: –The movie is partitioned according to a pre-defined function –Introduced a parameter W to confine the movie segment size Bandwidth Partition: –The bandwidth is partitioned into equal size logical channel (b Mbit/sec) The shape of skyscraper Time Access latency = The size of the first movie segment Client access bandwidth = 2 channels (2b Mbit/sec) Client buffer requirement = D 1 b(W – 1) Mbit K.A. Hua, and S. Sheu, "Skyscraper Broadcasting A New Broadcasting Scheme for Metropolitan Video-on-Demand Systems," ACM SIG- COMM. Sept

16 Greedy Disk Conserving Broadcasting Scheme (GDB) Aims: Minimize the server bandwidth so as to guarantee a given access latency under a given client I/O bandwidth Movie Partition: –The movie is partitioned according to a given function –Introduced a system parameter to constrain the size of movie Bandwidth Partition: –The bandwidth is partitioned into equal size logical channel (b Mbit/sec) Access latency = the size of the first movie segment Client access bandwidth = can be set by a system parameter Client buffer requirement = same as SB L. Gao, J. Kurose, D. Towsley, "Efficient Schemes for Broadcasting Popular Videos," Proceedings of NOSSDAV '98, Cambridge, UK, July 1998.

17 Harmonic Broadcasting Scheme (HB) Motivation: Bandwidth Partition Algorithm Initiative Movie Partition: –The movie is partitioned into equal size segment Bandwidth Partition: –The bandwidth is partitioned into K logical channels ( Mbit/sec) Channel 1 with b (Mbit/sec) Channel 2 with b/2 (Mbit/sec) Channel 3 with b/3 (Mbit/sec) Channel 4 with b/4 (Mbit/sec) Time L1 L2 Access latency = the size of the first movie segment Client access bandwidth = Total server bandwidth Client buffer requirement = Bounded by 37% of movie size L. S. Juhn, and L. M. Tseng, "Harmonic Broadcasting for Video-on-Demand Service," IEEE Transactions on Broadcasting, vol. 43(3), Sep 1997, Page(s):

18 Variants of Harmonic Broadcasting Scheme Cautious Harmonic Broadcasting Scheme (CHB) Quasi Harmonic Broadcasting Scheme (QHB) J. F. Paris, S.W. Carter, and D. D. E. Long, "Efficient Broadcasting Protocols for Video on Demand," Proc. 6th International Symposium on Modeling, Analysis and Simulation of Computer and Telecommunication Systems (MASCOTS '98), July 1998, Page(s):

19 Poly-harmonic Broadcasting Scheme (PHB) Movie Partition: –It partitions the movie into equal size segment Bandwidth Partition: –It partitions the bandwidth into K logical channels ( Mbit/sec) J. F. Paris, S.W. Carter, and D. D. E. Long, "A Low Bandwidth Broadcasting Protocol for Video on Demand," Proc. 7th International Conference on Computer Communications and Networks (IC3N '98), Oct 1998, Page(s): Time L1 L2 L1 L2 L1 L2 L1 L2 Access latency = Client access bandwidth = Total server bandwidth Client buffer requirement = Bounded by 37% of movie size

20 Staircase Data Broadcasting Scheme (SDB) Principle: Complicated Reception Schedule Movie Partition: –It partitions the movie into equal size segment Bandwidth Partition: –The bandwidth is partitioned into equal size logical channel (b Mbit/sec) L. S. Juhn and L. M. Tseng, "Staircase Data Broadcasting and Receiving Scheme for Hot Video Service," IEEE Transactions on Consumer Electronics, vol.43(4), Nov 1997, Page(s): Access latency = the size of the first movie segment Client access bandwidth < 2 channels (2b Mbit/sec) Client buffer requirement = Bounded by 25% of movie size Time L(1) L1 L(1) L(2,1) L(3,1) L(1) L(2,2)L(2,1)L(2,2)L(2,1)L(2,2) L(3,2)L(3,1)L(3,2)L(3,1)L(3,2) The shape of staircase

21 Fast Data Broadcasting Scheme (FB) Movie Partition: –It partitions the movie into equal size segment Bandwidth Partition: –The bandwidth is partitioned into equal size logical channel (b Mbit/sec) L.S. Juhn, and L.M. Tseng, " Fast Broadcasting for Hot Video Access," RTCSA'97: the proceedings of the 4th international workshop on real- time computing systems and applications, pp , Oct Access latency = the size of the first movie segment Client access bandwidth = At most the total server bandwidth Client buffer requirement = Time L(1) L(2) L(4) L(3) L(5) L(2) L(6) L(3) L(7) L(2) L(4) L(3) L(5)

22 Hybrid Broadcasting Scheme (HYB) Motivation: Broadcasting Schedule Initiative Movie Partition: –It partitions the movie into equal size segment Bandwidth Partition: –The bandwidth is partitioned into equal size logical channel (b Mbit/sec) J.F. Paris, S.W. Carter, and D.D.E. Long, "A hybrid broadcasting protocol for video on demand," Proc Multimedia Computing and Networking Conference (MMCN'99), San Jose, CA, Jan 1999, pp Access latency = the size of the first movie segment Client access bandwidth = At most the total server bandwidth Client buffer requirement = Bounded by 46% of movie size Time L(1) L(2) L(3) L(4) L(6) L(2) L(8) L(5) L(3) L(2) L(7) L(4) L(9) L(1) L(2) L(3) L(5) L(6)

23 Comparison Aim: find out the practicability of deploying difference broadcasting scheme under current network infrastructures. 1 st Comparison –Study the access latency of each scheme under a range of server bandwidth requirement 2 nd Comparison –Study the access latency of each scheme under client access bandwidth constraint 3 rd Comparison –Study the access latency of each scheme under client buffer constraint

24 1 st Comparison The access latency of difference scheme

25 2 nd Comparison – client access bandwidth constraint The client access bandwidth

26 2 nd Comparison The access latency of difference scheme

27 3 rd Comparison – client buffer constraint The access latency under different client buffer constraint Server bandwidth = 9Mbit/sec Client Access bandwidth = 2b Mbit/sec

28 3 rd Comparison – client buffer constraint The access latency under different client buffer constraint Server bandwidth = 30Mbit/sec Client Access bandwidth = 2b Mbit/sec

29 Analysis of Design Spaces for Optimal Scheme Broadcasting Scheme: –Broadcast Period Design: –In designing a broadcasting schedule of an optimal periodic broadcasting scheme, each movie segment must be broadcasted with broadcast period B Ti of t + T, where t is the start play point of movie segments. The time the viewer enters the system, t = 0 The time to play back the movie segment D The broadcast period of the movie segment Time

30 Analysis of Design Spaces for Optimal Scheme Movie Partition Algorithm –The size of the movie segment Design: –In designing an optimal periodic broadcasting scheme, the movie must be partitioned into movie segments as small as possible, so that each movie play point t can be broadcasted with its broadcast period B Ti of t + T The time the viewer enters the system, t = 0 The time to play back the movie segment D The broadcast period of the movie segment Time The broadcast period of this play point t is t + T The broadcast period of this play point t +  t is t + T

31 Analysis of Design Spaces for Optimal Scheme Broadcast Partition Algorithm –Data rate of streaming Design: –In designing an optimal periodic broadcasting scheme with a guarantee access latency T, each movie segment must be broadcasted as low rate as possible with a guarantee of continuous playback.

32 Analysis of Design Spaces for Optimal Scheme Reception Schedule –The flexibility of this dimension of design space is due to the server bandwidth inefficiency introduced by the broadcasting schedule. For an optimal broadcasting scheme, there is no room for designing this schedule Design: –In designing an optimal periodic broadcasting scheme with a guarantee access latency T, each viewer is required to download all the movie segments from all the

33 Optimal Periodic Broadcasting Scheme Theoretical Limitation of optimal periodic broadcasting scheme Server bandwidth requirement: Client buffer requirement:, where t’ is the time after the viewer enters the system

34 Optimal Periodic Broadcasting Scheme - PHB

35 Optimal Periodic Broadcasting Scheme - PHB

36 Customized Optimal Broadcasting Scheme PHB fails to pass the 2 nd comparison because of its large client access bandwidth. So as to optimal broadcasting scheme Relax the requirement of design point 1 –Broadcasting period

37 Customized Optimal Broadcasting Scheme T The total server bandwidth requirement The client access bandwidth T + L The play point t dtdt T The total server bandwidth requirement T + L The play point t dtdt The client access bandwidth

38 Practical Implementation – Customized PHB Client access bandwidth constraint S 1,1 S 1,2 S 2,3 S 2,1 S 2,2 S 3,1 S 3,2 S 3,4 S 3,3 S 1,1 S 1,2 S 2,3 S 2,1 S 2,2 S 1,1 S 1,2 S 3,1 S 3,2 S 4,1 S 4,2 S 5,3 S 5,1 S 5,2 S 4,3 S 4,1 S 6,1 S 6,2 Time where the client entering the system S 2,1 S 3,4 S 3,3 S 1,1 S 1,2 S 2,4 S 2,2 S 2,3 S 1,1 S 1,2 S 3,1 S 3,2 S 5,1 S 6,1 S 6,3 S 4,2 S 4,3 S 5,1 S 5,2 S 5,3 S 4,1 S 4,2 S 6,2 S 6,3 S 7,1 S 8,1 S 9,1 S 7,2 S 7,3 S 8,1 S 8,2 S 8,3 S 7,1 S 7,2 S 9,2 S 9,3 S 2,1 S 3,3 S 1,1 S 5,2 S 6,1 S 4,3 S 8,2 S 9,1 S 7,3 S1S1 S2S2 S3S3 S4S4 S5S5 S6S6 S7S7 S8S8 S9S9

39 Future work Evaluate the performance of customized PHB with the theoretical limitation

40 Q & A Thank you