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

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A Comparative Study of Periodic Broadcasting Scheme for Large-Scale Video Streaming

Prepared by Nera Liu

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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

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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

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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): 191-200.• 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): 15-23.

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Notation of Symbols

Symbol Description

L The length of the movie (sec)

b The playback rate of the movie (Mbit/sec)

K The no. of logical channels

N The no. of movie segments

Di The size of the i-th movie segment measured at the play back rate (sec)

Bs The total server bandwidth (Mbit/sec)

Dc The client access bandwidth (Mbit/sec)

C The client buffer to movie size ratio

T The maximum access latency

M The total no. of movie

fi The movie partition function

gi The bandwidth partition function

BTi The broadcast period of movie segment Di

• Some of them will be introduced later

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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

K

L

8

Analysis of Design Spaces

• Movie Partition Algorithm• Bandwidth Partition Algorithm• Broadcasting Schedule• Reception Schedule

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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.

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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

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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

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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

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Pyramid Broadcasting Scheme (PB)• Motivation: Movie Partition Algorithm Initiative• Movie Partition:

– The movie is partitioned according to a geometric series– Di+1 = Di

• 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. 197-208, 1996.

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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– Di+1 = Di

• 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. 118-126, Jun 1996.

Time

Each logical channel is partitioned into p sub-channels

sB

bKML

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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 = D1b(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. 1997.

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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.

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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) i

b

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 L1 L1L1 L1 L1 L1L1 L1 L1 L1L1

L2 L2 L2 L2 L2 L2


• 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): 268-271.

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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): 127-132.

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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): 690-697.

1 im

b

Time

L1

L2

L1 L1

L2

L1

L2

L1 L1

L2

• Access latency =

• Client access bandwidth = Total server bandwidth

• Client buffer requirement = Bounded by 37% of movie size

N

Lm

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Staircase Data Broadcasting Scheme (SDB)

• Principle: Complicated Reception Schedule• Movie Partition:

– It partitions the movie into equal size segment


• 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): 1110-1117.


• Client access bandwidth < 2 channels (2b Mbit/sec)


Time

L(1)

L1

L(1)

L(2,1)

L(3,1)

L(1) L(1) L(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

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Fast Data Broadcasting Scheme (FB)

• Movie Partition:– It partitions the movie into equal size segment


• 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. 237-243, Oct 1997.


• Client access bandwidth = At most the total server bandwidth

• Client buffer requirement =

Time

L(1) L(1) L(1) L(1) L(1) 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)

bLK

K

)12

21(

1

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Hybrid Broadcasting Scheme (HYB)

• Motivation: Broadcasting Schedule Initiative• Movie Partition:

– It partitions the movie into equal size segment


• J.F. Paris, S.W. Carter, and D.D.E. Long, "A hybrid broadcasting protocol for video on demand," Proc. 1997 Multimedia Computing and Networking Conference (MMCN'99), San Jose, CA, Jan 1999, pp 317-326.


• Client access bandwidth = At most the total server bandwidth


Time

L(1) L(1) L(1) L(1) L(1) 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(1)

L(2)

L(3)

L(5)

L(6)

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Comparison

• Aim: find out the practicability of deploying difference broadcasting scheme under current network infrastructures.

• 1st Comparison– Study the access latency of each scheme under a range of server

bandwidth requirement

• 2nd Comparison– Study the access latency of each scheme under client access bandwidth

constraint

• 3rd Comparison– Study the access latency of each scheme under client buffer constraint

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1st Comparison

• The access latency of difference scheme

5 1 000 . 0 0 1

1 5 2 0

S e r v e r b a n d w i d t h ( M b i t / s e c )

1 0 0 0

1

Cli

ent’s

Acc

ess

Lat

ency

(se

c, L

og-s

cale

)

0 . 0 1

0 . 1

1 0

1 0 0

H B

P H B

S B

P B

N V O D

P P B ( u n c o n s t r a i n t )

P P B ( c o n s t r a i n t )

G D B , S D B , F B

C H B

H Y B

Q H B

5 1 000 . 0 0 1

1 5 2 0


1 0 0 0

1

Cli

ent’s

Acc

ess

Lat

ency

(se

c, L

og-s

cale

)

0 . 0 1

0 . 1

1 0

1 0 0

H B

P H B

S B

P B

N V O D



G D B , S D B , F B

C H B

H Y B

Q H B

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2nd Comparison – client access bandwidth constraint

• The client access bandwidth

5 1 010

1 5 2 0


1 2

Cli

ent

acce

ss b

andw

idth

(Mbi

t/sec

)

4

8

1 6

2 0

S D B

P B

N V O D


G D B , P H B , H B , C H B , Q H B , H Y B , F B

S B


5 1 010

1 5 2 0


1 2

Cli

ent

acce

ss b

andw

idth

(Mbi

t/sec

)

4

8

1 6

2 0

S D B

P B

N V O D


G D B , P H B , H B , C H B , Q H B , H Y B , F B

S B


26

2nd Comparison

• The access latency of difference scheme

5 1 000

1 5 2 0


3 0

Cli

ent

acce

ss l

aten

cy (

min

)

1 0

2 0

4 0

5 0

S D B G D B 3

P H B

S B

N V O D , P B

T h e s e a r e t h e c u t - o f f p o i n t s o f o p e r a t i o n u n d e r t h e c o n s t r a i n t s o f c l i e n t a c c e s s b a n d w i d t h

H B , C H B , Q H B , H Y B , F B

5 1 000

1 5 2 0


3 0

Cli

ent

acce

ss l

aten

cy (

min

)

1 0

2 0

4 0

5 0

S D B G D B 3

P H B

S B

N V O D , P B

T h e s e a r e t h e c u t - o f f p o i n t s o f o p e r a t i o n u n d e r t h e c o n s t r a i n t s o f c l i e n t a c c e s s b a n d w i d t h

H B , C H B , Q H B , H Y B , F B

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3rd Comparison – client buffer constraint

• The access latency under different client buffer constraint

• Server bandwidth = 9Mbit/sec

• Client Access bandwidth = 2b Mbit/sec

0.15 0.250.050

0.35 0.45

Client Buffer to Movie Size Ratio

6

Clien

t ac

cess

lat

ency (m

in)

2

4

8

SDB

GDB3

SB

0.15 0.250.050

0.35 0.45


6

Clien

t ac

cess

lat

ency (m

in)

2

4

8

SDB

GDB3

SB

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3rd Comparison – client buffer constraint

• The access latency under different client buffer constraint

• Server bandwidth = 30Mbit/sec

• Client Access bandwidth = 2b Mbit/sec

0.15 0.250.050

0.35 0.45


6

Clien

t ac

cess

lat

ency (m

in)

2

4

8

SDB

GDB3

SB

0.15 0.250.050

0.35 0.45


6

Clien

t ac

cess

lat

ency (m

in)

2

4

8

SDB

GDB3

SB

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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 BTi of t + T, where t is the start play point of movie segments.

The time the viewer enters the system, t = 0



Time

30


• 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 BTi of t + T

The time the viewer enters the system, t = 0



Time

The broadcast period of this play point t is t + T The broadcast period of this play point t + t is t + T

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• 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.

D1

D2

D3

D4

D5

D6

D1

D2

D3

D4

D5

D6

32


• 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

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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

)ln(T

TLbBs

LTtTwheret

TLbt

Tt

dtbt

TtwhereT

TLbt

Tt

dtbt

tBuffer L

Tt

L

')'

ln(''

'0)ln(''

)'(

'

0

34

Optimal Periodic Broadcasting Scheme - PHB

5 10 150

0.2

0.4

0.6

0.6

1

Server bandwidth (Mbit/sec)

Clie

nt acc

ess l

aten

cy (m

in) Optimal periodic broadcasting scheme

PHB

5 10 150

0.2

0.4

0.6

0.6

1


Clie

nt acc

ess l

aten

cy (m

in) Optimal periodic broadcasting scheme

PHB

35

Optimal Periodic Broadcasting Scheme - PHB

6 10 150

0.2

0.4

0.6

0.6

1


Clie

nt b

uffe

r to

mov

ie si

ze ra

tio

Optimal periodic broadcasting scheme and PHB overlap each other

6 10 150

0.2

0.4

0.6

0.6

1


Clie

nt b

uffe

r to

mov

ie si

ze ra

tio

Optimal periodic broadcasting scheme and PHB overlap each other

36

Customized Optimal Broadcasting Scheme

• PHB fails to pass the 2nd 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

dt

T

The total server bandwidth requirement

T + L

The play point tdt

The client access bandwidth

38

Practical Implementation – Customized PHBClient access bandwidth constraint

S1,1 S1,2

S2,3S2,1 S2,2

S3,1 S3,2 S3,4S3,3

S1,1 S1,2

S2,3S2,1 S2,2

S1,1 S1,2

S3,1 S3,2

m

b

1m

b

2m

b

S4,1 S4,2

S5,3S5,1 S5,2

S4,3 S4,1

S6,1 S6,2

1m

b

Time where the client entering the system

N

Lm

S2,1

S3,4S3,3

S1,1 S1,2

S2,4S2,2 S2,3

S1,1 S1,2

S3,1 S3,2

S5,1

S6,1S6,3

S4,2 S4,3

S5,1S5,2 S5,3

S4,1 S4,2

S6,2 S6,3

S7,1

1m

b

S8,1

S9,1

S7,2 S7,3

S8,1S8,2 S8,3

S7,1 S7,2

S9,2 S9,3

S2,1

S3,3

S1,1

S5,2

S6,1

S4,3

S8,2

S9,1

S7,3

S1 S2 S3 S4 S5 S6 S7 S8 S9

1m

b

1m

b

1m

b1m

b

39

Future work

• Evaluate the performance of customized PHB with the theoretical limitation

40

Q & A

• Thank you

Documents

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