Post on 11-Jan-2016
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. 04/21/23 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.04/21/23 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
DPNM Lab. 04/21/23 13
/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
DPNM Lab. 04/21/23 14
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. 04/21/23 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. 04/21/23 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.
DPNM Lab. 04/21/23 17
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. 04/21/23 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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