Download Congestion Control and Adaptive Retransmission for Multimedia

Congestion Control and Adaptive
Retransmission for Multimedia
Streaming over Wireless Networks
Kamal Singh, Árpád Huszák, David
Ros, César Viho and Jeney Gábor
IRISA/INRIA, Rennes, France
BUTE, Budapest, Hungary
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Agenda
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Overview
Congestion control for Video Flows
Adaptive retransmissions and
wireless loss estimation
Results
Conclusion and Future Work
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Agenda
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Overview
Congestion control for Video Flows
Adaptive retransmissions and
wireless loss estimation
Results
Conclusion and Future Work
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Overview: Next Generation Wireless
Network
“Hotspots” with high
bandwidth
Video Streaming
anywhere in the cell
Users of Voice, TCP, …
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Overview: Wireless Problems in the
context of Video Streaming
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Problems due to the use of IP
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IP doesn’t support real time streaming
requirements
Problems due to radio conditions
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Scarce and time varying bandwidth
Congestion, wireless losses & large delay
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Overview: Video Streaming
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Video Streaming constraints
• Delay & Jitter
• Bandwidth, Congestion
• Packet loss
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Overview: Video Streaming …
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Video Streaming
• Underflow
• No Playout
• Packet losses will cause
quality distortion
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Agenda
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Overview
Congestion control for Video Flows
Adaptive retransmissions and
wireless loss estimation
Results
Conclusion and Future Work
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Congestion Control for Video Flows
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Motivation
• Variable bandwidth, delay …
• Congestion, packet losses
How can applications adapt to
the network conditions?
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Existing Schemes
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Congestion control for video
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TCP: Retransmissions, rate oscillations, …
TFRC [Floyd 2000]
 Sending Rate is calculated by a TCP model
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Better Rate Stability
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TCP Friendly
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Problems: Wireless Losses
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Problem: Two types of losses in
wireless Networks
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Packet drops due to congestion
Packet drops due to bad channel conditions
Wireless
network
IP Packets
IP Queue
Router
Node B
Congestion
loss
Wireless
loss
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Problems …
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Inefficiency for TCP, TFRC …
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How to distinguish Wireless losses from
congestion losses?
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Cannot distinguish between these losses.
Reduce their sending rate on loss.
Previous Work have used Round Trip Time
variations: May not be reliable
ARC [O. B. Akan et al. 04]: Sending Rate
(S) is calculated using w :
,
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ARC: How to calculate w ?
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Wireless Loss Estimation
(Background: DiffServ)
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Differential dropping in the DiffServ
Assured Forwarding (Green, Yellow & Red)
Increasing Congestion
Drop Red
packets
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Drop Red + Yellow
packets
Rarely drop Green
packets
Video applications mark their packets
I
B
P
B
P
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Wireless Loss Estimation
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Wireless Loss Estimation in DiffServ (WLED)
Networks: [VTC 2006]
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Red packets are dropped first on congestion
Wireless loss rate (w) is correlated with green
loss rate
 If loss of yellow packets is not significant
Estimate w for ARC using green loss rate
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WLED
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WLED:
Improves
link utilization
WLED
TFRC
TCP
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There is no change in other properties:
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TCP friendliness, loss rate, rate stability
But, works only with DiffServ aware applications
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Agenda

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Overview
Congestion control for Video Flows
Adaptive retransmissions and
wireless loss estimation
Results
Conclusion and Future Work
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Adaptive retransmissions and wireless
loss estimation
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We improved link utilization in case
of wireless losses.
But, lost data still deteriorates the
quality!
Solution: We integrate a scheme to
retransmit the lost data.
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Adaptive retransmissions and wireless
loss estimation …
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Retransmission Scheme
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If packet has the possibility to arrive before its
deadline
 No congestion  Enables retransmission schemes
 Congestion  Disable retransmission
Example Scenario:
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Adaptive retransmissions and wireless
loss estimation …
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Depending on:
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Retransmit either
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Available Bandwidth shown by Congestion
Control scheme
Amount of I, P and B frames in video files
I frames
I + P frames or
All frames
WLED scheme integrated
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Adaptive retransmissions and wireless
loss estimation : Transport protocol
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DCCP (Datagram Congestion Control Protocol)
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Sequence numbers
Feedback/ACK vectors
Useful for loss detection
Retransmissions done at the application layer
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Adaptive retransmissions and wireless
loss estimation : Simulation details
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NS2
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Dumbbell topology with 1Mbps of link
with 40ms delay
Packet losses simulated in the wireless
link
Reference Video: 360kbps “Mother
and Daughter” encoded using H.264
FTP and WWW flows as background
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Agenda
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Overview
Congestion control for Video Flows
Adaptive retransmissions and
wireless loss estimation
Results
Conclusion and Future Work
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Key Results
• 10 WWW users in background
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Key Results …
• Wireless loss probability 0.1 and varying WWW users
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Agenda
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Overview
Congestion control for Video Flows
Adaptive retransmissions and
wireless loss estimation
Results
Conclusion and Future Work
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Conclusion and Future Work
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Used a wireless loss estimation scheme
integrated with a retransmission scheme
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Obtained better video quality
Future Work
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Performance of WLED + retransmission in real
network
Congestion control and adaptive
retransmission for MPEG4-scalable video codec
(SVC)
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Thank You !
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