analysis of using broadcast and proxy for streaming layered encoded videos wilson, wing-fai poon and...

Analysis of Using Broadcast and Proxy for Streaming Analysis of Using Broadcast and Proxy for Streaming Layered Encoded VideosLayered Encoded Videos

Wilson, Wing-Fai Poon and Kwok-Tung Lo

ContentsContents

Introduction System Architecture Analytical Model of the system Results Conclusions

Introduction (1)Introduction (1)

Video-on-Demand system has not been commercial success

Two directions to provide a cost-effective VoD services: Multicast/broadcast techniques to share the system

resources Proxy servers to minimize the network transmission

cost

Multicast/broadcast Near VoD: Skyscraper, Fast Data, Poly-harmonic True (zero-delay) VoD: Patching, Stream Tapping

Introduction (2)Introduction (2)

Proxy If the proxy is congested or the requested video is not

stored in it, the customer will be served by the central server

Proxy pre-caches a portion/whole of a video to serve the local customers

There is a trade-off between the limited backbone bandwidth and the cost of the local storage

Heterogeneous EnvironmentHeterogeneous Environment

Improve the system performance under the homogeneous environment

Heterogeneous environment Use the layered video streams Flexibly provide different quality of videos by

transmitting different number of layers according to the available bandwidth between the server and customers

ObjectiveObjective

Build a large-scale VoD system in heterogeneous network environment

Explore hierarchical network architecture to provide VoD services

Evaluate the system performance if the network has multicast/broadcast capability

Videos are layered encoded store in the proxy server broadcast to the customers

System ArchitectureSystem ArchitectureCentral

Repository

Wide Area Network

ProxyServer

Local Area

56 kbps Clients

Video data

Local Area

1.5Mbps Clients 3 Mbps Clients

low quality videos

high quality videos

Local Area

rj is the probability of customers requesting the jth quality of the videos

The lower quality layers must be first stored before caching the enhancement layer qmj as the fraction of customers requesting the jth layer of

video m

Proxy ServerProxy Server

ml

jkkmj rq

bmj as the proxy map to describe the subsets of video layers in proxy set to 1 if layer j of video m is in proxy; otherwise, set

to 0

Proxy ServerProxy Server

ijij

M

i

l

ji bqp

i

1 1

Kbs ij

M

i

l

jij

i

1 1

ijs

K

il

ip

M

ij

i

i

videoof layer of size:

sizeproxy :

for video layers encoded ofnumber :

videoof popularity :

videosofnumber total:

Maximize:

Subject to

where

System ModelSystem Model

Requests go up to the central server can be found

M

i

l

jijjis

i

brp1 1

)1(

Average bandwidth requirement for a video request is equal to

M

i

l

j

ik

j

kk

s

jii

bCrp

R1 1 1

)(

ijij

k

bb

kC

of complement:

layer of rate streaming :where

rate arrival system :where


Model as M/M/N/N queuing system If B is the available bandwidth between the server

and the proxy, the number of channels is

R

BN

The service rate of the system is where T is the mean service time

PI: percentage of new requests blocked from the central server

T

1

Bs

I

PP where

N

j

js

Ns

B

j

NP

0

!/)/(

!/)/(


Proxy server can support some of these customers with lower quality of video streams

PII: proportion of new requests completely blocked from the system

B

M

i

l

j

j

k

ijjiII PbrpPi

1 1 1

Multicast/BroadcastMulticast/Broadcast

The proxy is not be able to serve the video requests Layers of the videos can be broadcast over the

backbone channels For example, a customer may receive the base layer of a

video from the broadcast channel and the enhancement layers from the dedicated channels

The customer thus at least receives the basic quality of the video even if the network is very congested


Layer 4

Layer 3

Layer 1

Layer 2

client1 client2

Proxy server

Central server

Network

Broadcasting channels


Dx as the number of channels required for the broadcasting protocol x

gm as the highest layer of video m using the broadcasting scheme jth layer of video m, where , is either broadcast to

the customers or stored in the proxy mgj

Bandwidth requirement for broadcasting

M

i

g

jijxjB

i

bDCR1 1

gm can be calculated such that rsvB BR


The arrival rate for the dedicated channels can be reduced because some video layers are being broadcast

M

i

g

jijji

M

i

l

jijjis

ii

brpbrp1 11 1

* )1(

The average streaming rate of the dedicated channels is equal to

M

i

l

gj

ik

j

gkk

s

jii

i i

bCrp

R1 1 1

** )(

M/M/N*/N* queue can be applied to calculate the blocking probability of the system

**

R

RBN B


**

* BsI

PP where

*

0

*

***

!/)/(

!/)/(N

j

js

Ns

B

j

NP

*

1 1

*B

M

i

l

jijjiII PrpP

i

01

j

kij

ij

b 0igwhere

otherwise

SimulationSimulation

Simulation Model client requests are modeled as the Poisson arrival

process video popularity is followed by Zipf’s distribution

Three scenarios of requesting quality pattern Scenario A (S-A): r5 = 1, r1 = r3 = r4 = r2 = 0

Scenario B (S-B): r2 = r5 = 0.5, r1 = r3 = r4 = 0

Scenario C (S-C): r1 = r2 = r3 = r4 = r5 = 0.2

Results (1)Results (1)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Arrival Rate /s

Blo

ckin

g P

roba

bilit

y

Math: (B, II) Math: (A, II) Math: (C, II)Sim: (B, II) Sim: (A, II) Sim: (C, II)Math: (B, I) Math: (A, I) Math: (C, I)

Number of videos: 200Video Length: 90 minProxy Size: 10 videosBandwidth: 100Mbps


0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 5 10 15 20 25 30 35 40

No of Videos in Proxy

Blo

ckin

g P

roba

bilit

y

Math: (B, II) Math: (A, II) Math: (C, II)Sim: (B, II) Sim: (A, II) Sim: (C, II)Math: (B, I) Math: (A, I) Math: (C, I)

Number of videos: 200Video Length: 90 minArrival Rate: 0.3/sBandwidth: 100Mbps


0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90 96 102

108

114

120

126

132

138

No of Broadcasting Layers

Typ

e I

Blo

ckin

g P

roba

bilit

y

M: 0.1 S: 0.1 M: 0.2 S: 0.2 M: 0.3S: 0.3 M: 0.4 S: 0.4 M: 0.5 S: 0.5M: 0.6 S: 0.6 M: 0.7 S: 0.7 M: 0.8S: 0.8 M: 0.9 S: 0.9 M: 1 S: 1

Number of videos: 200Video Length: 90 minProxy Size: 10 videosBandwidth: 100MbpsBroadcast: 10 channels


0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

4 6 8 10 12 14 16 18 20

Broadcasting Channels for Each Layer

Ser

ver

Ban

dwid

th (

100M

uni

t)

(0.5, 5)(1.0, 5)(0.5, 10)(1.0, 10)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

4 6 8 10 12 14 16 18 20

Broadcasting Channels for Each Layer

Pro

port

ion

of B

andw

idth

for

B

road

cast

ing

(0.5, 5)(1.0, 5)(0.5, 10)(1.0, 10)

Number of videos: 200Video Length: 90 minArrival Rate: 0.5 or 1.0/sProxy Size: 5 or 10 videos


0.00

2.00

4.00

6.00

8.00

10.00

12.00

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1Arrival Rate

Ser

ver

Ban

dwid

th (

100M

uni

t)

NoP_NoBP_NoBNoP_BP_B

0

0.1

0.2

0.3

0.4

0.5

0.6

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1Arrival Rate

Pro

port

ion

of B

andw

idth

for

B

road

cast

ing

NoP_NoBP_NoBNoP_BP_B

Number of videos: 200Video Length: 90 minProxy Size: 5 videosBroadcast: 10 channels

Result (6)Result (6)

0

0.05

0.1

0.15

0.2

0.25

0.3

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4Maximum Blocking Probability

Typ

e II

Blo

ckin

g P

roba

bilit

y

(0.5, 5) (1.0, 5)(0.5, 10) (1.0, 10)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1


Pro

port

ion

of B

andw

idth

for

B

road

cast

ing

(0.5, 5) (1.0, 5)(0.5, 10) (1.0, 10)

Number of videos: 200Video Length: 90 minArrival Rate: 0.5 or 1.0/sProxy Size: 5 or 10 videosBroadcast: 10 channels

0.00

1.00

2.00

3.00

4.00

5.00

6.00


Ser

ver

Ban

dwid

th (

100M

uni

t)

(0.5, 5) (1.0, 5)(0.5, 10) (1.0, 10)

ConclusionConclusion

One of the challenges to provide VoD service is how the video streams can be delivered in the heterogeneous environment

Scalability hierarchical architecture efficient broadcasting protocols

Heterogeneous Layered encoded videos

Bandwidth reserved for broadcasting? Caching policy if proxies can communicate with each

other?

analysis of using broadcast and proxy for streaming layered encoded videos wilson, wing-fai poon and...

Documents