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Enhancing Multimedia Streaming Performance in Wireless Classroom Networks

This study explores the performance of media streaming in a portable wireless classroom network, focusing on multimedia traffic characteristics, capacity limitations, and the impact of the "Bad Apple" phenomenon. Results show the potential of wireless LAN technology for online education, highlighting challenges related to network capacity and client protocol efficiency.

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Enhancing Multimedia Streaming Performance in Wireless Classroom Networks

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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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