Congestion Control and Adaptive Retransmission for Multimedia Streaming over Wireless Networks

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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

• Overview
• Congestion control for Video Flows
• Adaptive retransmissions and wireless loss
  estimation
• Results
• Conclusion and Future Work

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Agenda

• 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
Video Streaming anywhere in the cell
Hotspots with high bandwidth
Users of Voice, TCP,
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Overview Wireless Problems in the context of
Video Streaming

• Problems due to the use of IP
• IP doesnt support real time streaming
  requirements
• Problems due to radio conditions
• Scarce and time varying bandwidth
• Congestion, wireless losses large delay

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Overview Video Streaming

• Video Streaming

constraints

• Delay Jitter
• Bandwidth, Congestion
• Packet loss

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Overview Video Streaming

• Video Streaming

• Underflow
• No Playout

• Packet losses will cause
• quality distortion

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Agenda

• 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

• Motivation

• Variable bandwidth, delay
• Congestion, packet losses

How can applications adapt to the network
conditions?
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Existing Schemes

• Congestion control for video
• TCP Retransmissions, rate oscillations,
• TFRC Floyd 2000
• Sending Rate is calculated by a TCP model
• Better Rate Stability
• TCP Friendly

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Problems Wireless Losses

• Problem Two types of losses in wireless Networks
• Packet drops due to congestion
• Packet drops due to bad channel conditions

Wireless network
IP Packets
IP Queue
Router
Node B
Wireless loss
Congestion loss
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Problems

• Inefficiency for TCP, TFRC
• Cannot distinguish between these losses.
• Reduce their sending rate on loss.
• How to distinguish Wireless losses from
  congestion losses?
• 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
• ARC How to calculate w ?

,
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Wireless Loss Estimation (Background DiffServ)

• Differential dropping in the DiffServ Assured
  Forwarding (Green, Yellow Red)
• Video applications mark their packets

Increasing Congestion
Drop Red packets
Drop Red Yellow packets
Rarely drop Green packets
I B P B P
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Wireless Loss Estimation

• Wireless Loss Estimation in DiffServ (WLED)
  Networks VTC 2006
• 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

• WLED
• Improves
• link utilization
• There is no change in other properties
• TCP friendliness, loss rate, rate stability
• But, works only with DiffServ aware applications

WLED
TFRC
TCP
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Agenda

• 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

• 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

• Retransmission Scheme
• 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

• Depending on
• Available Bandwidth shown by Congestion Control
  scheme
• Amount of I, P and B frames in video files
• Retransmit either
• I frames
• I P frames or
• All frames
• WLED scheme integrated

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Adaptive retransmissions and wireless loss
estimation Transport protocol

• DCCP (Datagram Congestion Control Protocol)
• 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

• NS2
• 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

• 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

• 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

• Used a wireless loss estimation scheme integrated
  with a retransmission scheme
• Obtained better video quality
• Future Work
• Performance of WLED retransmission in real
  network
• Congestion control and adaptive retransmission
  for MPEG4-scalable video codec (SVC)

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Thank You !