INFOCOM, 2007

Chen Bin Kuo (20077202) Young J. Won (20063292)

DPNM Lab.

DPNM Lab.

Introduction Problem Description and Assumptions Mathematical Model Simulation Result Conclusions Discussion

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DPNM Lab.

Fiber optic access networks (fiber-to-the-premises and fiber-to-the-node) have boosted individual user’s broadband access speeds.

IP networks may soon become a delivery mechanism for broadcast television content.

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DPNM Lab.

IP data packets in FTTP network might include:◦ Broadcast video◦ Video-on-demand (VOD)◦ Web applications such as web surfing, online

gaming, and p2p file transfers

Demand of a video stream (under MPEG-2 encoding) ◦ Standard definition (SD) : 3.75 Mbps◦ High definition (HD) : 15 Mbps

Evaluating bandwidth demand is necessary. 04/19/23 4

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Core Router

Edge Router

Optical Line Terminal (OLT)

Passive Optical Network (PON)

Optical Network Terminal (ONT)

Portion of a FTTP network

How big do these links need to be?

Core router and edge router

deliver content to the edge of the

network .An OTL forwards the content over a PON to an ONT

at each subscriber’s

premise.

32 subscribers

2000 subscribers

DPNM Lab.

Steady state demand◦ Analytical methods for engineering links often

assume stationary (steady state) busy hour traffic.

◦ All viewers have settled into channels◦ Using multicast to satisfy demand

Channel surfing◦ Disrupting the steady state at every commercial

break◦ Significant additional bandwidth demand is

required.04/19/23 6

DPNM Lab.

If there exist two viewers watch the same channel (5 different in total)

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If all viewers watch different channels (6 different channels)

6 video stream required5 video stream required

Viewers

OTL

Edge Router

The network needs to deliver only one video stream for the same channel to the OLT where it must divide the stream for two viewers.

DPNM Lab.

The way to make channel changes fast is to send surfers unicast (one per viewer) streams at higher rates.

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Channel change server

Channel change server

Playout buffer (in the set top box)

Playout buffer (in the set top box)

Higher rate Usual rate

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Settled in one channel (steady

state)

Channel surfing (commercial break)

Bandwidth

Time

Bandwidth planning issue• What is the demand?• How to model the traffic?

Bandwidth planning issue• What is the demand?• How to model the traffic?

DPNM Lab.

A viewer: a device capable of receiving an IPTV stream

Each set top box always remains on and receives some video stream

This paper only to characterize broadcast IP TV’s contribution (from edge router to an OLT)

Homogeneous viewers

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DPNM Lab.

The program definition is independent of the renewal process

The number of active viewers is constant during commercial break

Commercial breaks on all channels begin at the same time and all active viewers begin surfing at the same time

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Steady State Multicast Model

Steady State Multicast Model

Channel Surfing Model – Single UserChannel Surfing Model – Single User

Extend to multiple

users

Extend to multiple

users

Focusing on the viewers who are not

surfing

Focusing on the viewers who are not

surfing

The Time to Fill the Playout Buffer

The Time to Fill the Playout Buffer

Single Viewer Behavior

Single Viewer Behavior

Combined Model (Multiple Users)Combined Model (Multiple Users)Bandwidt

h Demand

Bandwidth

Demand

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/iz c i (1)

( , ) ( , )

( , )i

di

p i SD p i HD z

p i d p

Assume that ( , ) i dp i d z p

(2)

i Label a channel

iz The probability that a viewer will choose the ith most popular program

s = (i,d) i is channel number and d is the program definition ( ) ( , )p s p i d The steady state probability that a viewer will pick stream s

= (i,d)

d SD or HD

c is constant, is close to 1

Channel i, probability that a viewer

will choose

Channel i, probability that a viewer

will choose

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Sr Rate at which SD content plays out of buffer, and Hr

denotes HD content

CSr Rate at which channel change server delivers SD content to the buffer for a channel change, and CHr denote HD

content

Sb SD buffer size in seconds

St The time the bandwidth must stay high after a single channel change

1( )R t A random variable, which is the bandwidth demand of a viewer at time t

kH Time, where min( , ) for 1k kH Y k

( )H t The system in a “high” state while the channel change server is working, and ( )L t denotes the “low” state while

server is finished with this cannel change

kD The programming definition that the viewer switches to at time kT , where k = 1, 2, 3, …

kT The renewal epoch, where 0 1k kT Y Y

kY The times between renewals (channel changes), where k = 0, 1, 2, 3, …

DPNM Lab. 04/19/23 15

1

/ 1S

S S SCS S CS S

rt b b

r r r r

(3)

0 1

1

1

for

( ) for , 1

for , 1k

k

D

CD k k k

D k k k

r t T

R t r T t T H k

r T H t T k

(4)

1

with probability ( ( )) ( )

with probability ( ( )) ( )( )

with probability ( ( )) ( )

with probability ( ( )) ( )

S

H

CS

CH

r P L t P D SD

r P L t P D HDR t

r P H t P D SD

r P H t P D HD

(5)

The time the bandwidth must stay high after a single channel change

The time the bandwidth must stay high after a single channel change

A random variable, which is the bandwidth demand of a viewer at

time t

A random variable, which is the bandwidth demand of a viewer at

time t

DPNM Lab. 04/19/23 16

1

( ) ( ) ( ) ( 0)a

U j j jj

B t R t I L t I L

,

( ) ( ( ) 0)d

M d sd SD HD s S

B t r I N t

( ) ( ) ( )U MB t B t B t

a The number of active viewers, which are watching the associated device

( )jR t Viewer j’s demand, where 1 j a

jL The time that surfing viewer j changes channels for the last time (the termination epoch of the renewal process)

( )UB t The total (unicast) demand from surfers ( )MB t The multicast demand

I An indicator function ( )sN t The number of viewers watching multicast stream s jumps

by 1 whenever a surfer stops surfing and joins multicast group s.

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M = 400 Total viewers

A = 200 Active viewers

500 channels offered 3.75, 15,

2.5 , 2.5S H

CS S CH H

r r

r r r r

Mbps

1Sb SD buffer size in seconds

0.67

(seconds) the playout buffer fill time when the channel change server is running

90%,

10%SD

HD

p

p

The probability that a stream is SD or HD

Mean time between renewals is 4

seconds

Which means the average time for a viewer who will change the channel is 4 seconds

Mean number of channel changes is 10

DPNM Lab. 04/19/23 18

The time to start channel surfing when

commercial break starts

The time to start channel surfing when

commercial break starts

The channel surfing endsThe channel surfing ends

DPNM Lab.

The paper developed a model to quantify bandwidth demand during the transition from surfing to steady state viewing.

The example with 400 viewers shows mean demand during surfing peaking at almost two times the steady state level if the service provider offers fast IP TV channel changes.

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DPNM Lab.

Assumptions of the mathematical model

How to model the user behavior more realistic?

What else can we contribute to the IP TV filed?

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