1 / 17

Enhancing Video Streaming Over Wireless Networks: Beyond TCP Limitations

Explore the shortcomings of TCP in video streaming over wireless networks, compare ideal solutions, address link speed heterogeneity, and propose improvements for better throughput. Learn about the impact of shared channel time and the necessity of understanding wireless link diversities.

lindavelez
Download Presentation

Enhancing Video Streaming Over Wireless Networks: Beyond TCP Limitations

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Video Streaming Over Wireless: Where TCP is Not Enough Xiaoqing Zhu, Jatinder Pal Singh and Bernd Girod Information Systems Laboratory Stanford University

  2. Wireless Home Networking 6 Mbps 24 Mbps 54 Mbps 12 Mbps

  3. Outline • TCP throughput over wireless • Demo: video streaming vs. file transfer • Comparison with ideal solution • What’s missing in TCP?

  4. Heterogeneity in Wireless Link Speeds CN C1 Cl … Channel Time

  5. Stream 1 ) ) ) ) ) 54Mbps 6 ~ 54 Mbps ) ) ) ) ) Stream 2 UDP Throughput over Wireless Simulation in NS2, for 802.11a network 30 Stream 1, alone 25 Stream 2, alone 20 Stream 1, shared Throughput (Mbps) 15 10 Stream 2, shared 5 0 10 20 30 40 50 Nominal Speed of Second Link (Mbps)

  6. Stream 1 ) ) ) ) ) 54Mbps 6 ~ 54 Mbps ) ) ) ) ) Stream 2 TCP Throughput over Wireless Simulation in NS2, for 802.11a network 20 Stream 1, alone 15 Stream 2, alone Throughput (Mbps) Stream 1, shared 10 Stream 2, shared 5 0 10 20 30 40 50 Nominal Speed of Second Link (Mbps)

  7. Overhead of TCP ACK

  8. Scenario A Demo: Two Nodes Video Source @ 2Mbps Link Speed: 11 Mbps Throughput : 4.4 Mbps Shared : 1.0 Mbps (~ 20 % channel time) Shared : 1.0 Mbps (~ 70% channel time) File Transfer Source: 3.7MB Link Speed: 2 Mbps Throughput : 1.4 Mbps

  9. TCP Performance Video Streaming @ 2 Mbps … ~ 30 s Rate File Transfer @ 1.0 Mbps Time

  10. What Could Have Happened … Video Streaming @ 2 Mbps … Rate File Transfer @ 0.7 Mbps ~ 42 s Time

  11. Scenario B Link Speed: 2 Mbps File Transfer Source: 3.7MB Throughput : 1.4 Mbps Shared : 1.2 Mbps (~ 85% Channel Time) Shared : 1.2 Mbps (~ 6% Channel Time) Link Speed: 54 Mbps Throughput : 20 Mbps Video Source @ 3 Mbps

  12. TCP Performance Video Streaming @ 3 Mbps … Rate ~ 25 s File Transfer @ 1.2 Mbps Time

  13. What Could Have Happened … Video Streaming @ 3 Mbps … Rate ~ 27 s File Transfer @ 1.2 Mbps Time

  14. What’s Missing in TCP? • Awareness of application’s utility function • For file transfer, aggregate rate matters • For video streaming, instantaneous rate matters • Video streams differ in their rate-quality tradeoffs • Utility function only needed at the source • Knowledge of wireless link heterogeneity • Channel time shared among competing links • Congestion due to neighboring transmissions • High rate over a fast link vs. low rate over a slow link • End-to-end measurement no longer suffices • Notion of fairness should be revisited

  15. Clean Slate Design or Evolution?

  16. TCP Throughput over Wireless • Per-packet fairness at the MAC layer • Similar end-to-end observations of p, and RTT for competing wireless links • Approximately equal rate, regardless of link speed packet size data rate [Heusse et al. 2003] packet loss rate round trip time [Mahdavi, Floyd 1997] [Floyd et al. 2000]

  17. Stream 1 Stream 2 TCP Throughput over Wireless Simulation in NS2, for 802.11a network ) ) ) ) ) 54Mbps 6 ~ 54 Mbps ) ) ) ) )

More Related