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Media Streaming Performance in a Portable Wireless Classroom Network

Media Streaming Performance in a Portable Wireless Classroom Network. Presenter: Jean Cao Supervisor: Carey Williamson TRLabs & Dept. of Computer Science UoC April 14, 2005. Outline. Motivations Media Traffic Characterization Classroom Measurements Extended Experiments: Capacity

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Media Streaming Performance in a Portable Wireless Classroom Network

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  1. Media Streaming Performance in a Portable Wireless Classroom Network Presenter: Jean Cao Supervisor: Carey Williamson TRLabs & Dept. of Computer Science UoC April 14, 2005

  2. Outline • Motivations • Media Traffic Characterization • Classroom Measurements • Extended Experiments: • Capacity • Bottleneck • The “Bad Apple” Phenomenon • Conclusions • Current and Future Work

  3. Motivations On-Line Education Wireless LAN Sniffer Server Portable Wireless Classroom Network [7, 8, 11] Multimedia Streaming [1, 2, 3, 4] Feasible? Client A French Cinematography Class Test Client Client Protocol Efficiency? Performance Issues? Note: Citation numbers are referred to the corresponding references of the paper.

  4. Motivations On-Line Education Wireless LAN Sniffer Server Portable Wireless Classroom Network [7, 8, 11] Multimedia Streaming [1, 2, 3, 4] Feasible? Client A French Cinematography Class Test Client Client Protocol Efficiency? Performance Issues? Note: Citation numbers are referred to the corresponding references of the paper.

  5. Motivations On-Line Education Wireless LAN Sniffer Server Portable Wireless Classroom Network [7, 8, 11] Multimedia Streaming [1, 2, 3, 4] Feasible? Client A French Cinematography Class Test Client Client Protocol Efficiency? Performance Issues? Note: Citation numbers are referred to the corresponding references of the paper.

  6. Motivations On-Line Education Wireless LAN Sniffer Server Portable Wireless Classroom Network [7, 8, 11] Multimedia Streaming [1, 2, 3, 4] Feasible? Client A French Cinematography Class Test Client Client Protocol Efficiency? Performance Issues? Note: Citation numbers are referred to the corresponding references of the paper.

  7. Motivations On-Line Education Wireless LAN Sniffer Server Portable Wireless Classroom Network [7, 8, 11] Multimedia Streaming [1, 2, 3, 4] Feasible? Client A French Cinematography Class Test Client Client Protocol Efficiency? Performance Issues? Note: Citation numbers are referred to the corresponding references of the paper.

  8. Motivations On-Line Education Wireless LAN Sniffer Server Portable Wireless Classroom Network [7, 8, 11] Multimedia Streaming [1, 2, 3, 4] Feasible? Client A French Cinematography Class Test Client Client Protocol Efficiency? Performance Issues? Note: Citation numbers are referred to the corresponding references of the paper.

  9. Media Traffic Characteristics • Digitized 8 min clip from movie “Au Revoir Les Enfants (1998)” • Converted to MPEG-4 • Audio @ 128 kbps and 43 fps • Video @ 400 kbps and 30 fps • Total 14,854 video frames • Mean frame size 1,641 bytes • 90% frames are [1 KB, 2 KB] • 1.4% > 4 KB

  10. Media Traffic Characteristics • Video Source Traffic Profile at Different Granularities: (a) 1 second (b) 3 seconds (c) 30 seconds (d) 1 minute Variable Bit Rate @ finer-grain time scale Constant Bit Rate @ coarse-grain time scale

  11. Classroom Measurements • French cinematography class • System setup • IEEE802.11b Ad Hoc Network (11Mbps theoretical bandwidth) • 8 laptops as Clients (mpeg4player) • 1 laptop as Server (Apache http server and Darwin Streaming server) • 1 laptop as channel monitor (Sniffer software) • Procedure: • Watch the 8 minute movie clip • Complete the Web based multiple-choice quiz • Review 2 short movie clips while answering questions

  12. Classroom Measurements • Results • Conducted successfully • Feedbacks from students are positive

  13. Classroom Measurements 4.6 Mbps UDP (RTP) UDP (RTP) • Observations • 469,778 packets tx over the channel • 99.3% of UDP and 0.7% of TCP • 0.025% CRC errors • 0.43% MAC retransmissions • First 200 seconds: TCP (RTSP) • UDP (RTP) data packets • After 10 minutes: TCP (HTTP) • Heaviest demand from multimedia streaming • Max throughput is about 4.6 Mbps (vs. 5-6 Mbps effective BW of 11b) Time TCP (HTTP) TCP (RTSP) Time

  14. Additional Experiments • 8 clients saturate the network; and the 9th client degrades the performance of all clients equally. • Bottleneck – the wireless channel

  15. The Bad Apple Phenomenon Client 1 Client 2 Client 3 Server

  16. The Bad Apple Phenomenon Client 1 Client 2 Client 3 X Server

  17. The Bad Apple Phenomenon Client 1 Client 2 Client 3 X Server

  18. The Bad Apple Phenomenon Client 1 Client 2 Client 3 One Bad Apple Spoils the Batch! X Server

  19. The Bad Apple Phenomenon

  20. The Bad Apple Phenomenon Client 1 Client 2 Server Wireless Network Interface Queue MAC Protocol X Client 3 Wireless Channel Drop

  21. The Bad Apple Phenomenon

  22. The Bad Apple Phenomenon Playback Stats at Clients

  23. Conclusions • Portable Wireless Classroom Network is a promising technology for education • Currently, 802.11b network can support limited number of streaming clients, and the bottleneck is at the wireless channel • When system is overloaded, degrading performance for all clients • The “bad apple” phenomenon can seriously degrade multimedia delivery in wireless environments; can a security problem

  24. Current and Future Work • More elegant solutions to the “bad apple” problem • Adaptive MDMI (Multiplicative Decrease and Multiplicative Increase) algorithm • Multi-Channel Multi-Rate algorithm • QoS support in Wireless LAN -- keep “bad apple” problem in mind

  25. QUESTIONS?

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