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Congestion Control and Adaptive Retransmission for Multimedia Streaming over Wireless Networks

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. Agenda. Overview Congestion control for Video Flows

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Congestion Control and Adaptive Retransmission for Multimedia Streaming over Wireless Networks

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  1. 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

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

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

  4. Overview: Next Generation Wireless Network “Hotspots” with high bandwidth Video Streaming anywhere in the cell Users of Voice, TCP, …

  5. Overview: Wireless Problems in the context of Video Streaming • Problems due to the use of IP • IP doesn’t support real time streaming requirements • Problems due to radio conditions • Scarce and time varying bandwidth • Congestion, wireless losses & large delay

  6. Overview: Video Streaming constraints • Video Streaming • Delay & Jitter • Bandwidth, Congestion • Packet loss

  7. Overview: Video Streaming … • Video Streaming • Underflow • No Playout • Packet losses will cause • quality distortion

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

  9. Congestion Control for Video Flows • Motivation • Variable bandwidth, delay … • Congestion, packet losses How can applications adapt to the network conditions?

  10. 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

  11. 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

  12. 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 ? ,

  13. Differential dropping in the DiffServ Assured Forwarding (Green, Yellow & Red) Video applications mark their packets Wireless Loss Estimation (Background: DiffServ) Increasing Congestion Drop Red packets Drop Red + Yellow packets Rarely drop Green packets I B P B P

  14. 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

  15. 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

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

  17. 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.

  18. 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:

  19. 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

  20. 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

  21. 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

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

  23. Key Results • 10 WWW users in background

  24. Key Results … • Wireless loss probability 0.1 and varying WWW users

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

  26. 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)

  27. Thank You !

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