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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
System ModelSystem Model
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
!/)/(
!/)/(
System ModelSystem Model
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
Multicast/BroadcastMulticast/Broadcast
Layer 4
Layer 3
Layer 1
Layer 2
client1 client2
Proxy server
Central server
Network
Broadcasting channels
Multicast/BroadcastMulticast/Broadcast
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
System ModelSystem Model
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
System ModelSystem Model
**
* 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
Results (2)Results (2)
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
Results (3)Results (3)
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
Results (4)Results (4)
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
Results (5)Results (5)
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
0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4Maximum Blocking Probability
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
0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4Maximum Blocking Probability
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?