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Impacts of a Poor Channel on Wireless LAN Performance

Explore the effects of a bad channel on overall WLAN performance, correlating performance for competing traffic and examining the impact on various network layers and applications. This study verifies Williamson's conclusion that poor channel conditions for one client can degrade overall performance, with a focus on streaming traffic at bad locations. Experimental methods, tools, and setup are detailed, with preliminary results and analysis presented. Relevant to the increasing deployment of streaming multimedia over wireless LANs, this research investigates how a poor channel affects performance at different layers in the network.

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Impacts of a Poor Channel on Wireless LAN Performance

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  1. Effects of a Bad Channel on the overall WLAN Performance. Ashish Samant, Jon Gretarsson, Feng Li {Asamant, jontg, lif}@cs.wpi.edu Computer Science Department Worcester Polytechnic Institute Worcester, MA, 01609 USA CS577 Advanced Networking Spring 05

  2. Outline • Introduction • Experimental Methods • Tools and Setup • Experimental Design • Preliminary Results and Analysis CS577 Advanced Networking Spring 2005

  3. Motivation • Increasingly, deployment of streaming multimedia over wireless LANs • Hardware price decreasing. • Wireless link capacity increasing: 11Mbps(802.11b), 54Mbps(802.11g). • Streaming techniques becoming mature. CS577 Advanced Networking Spring 2005

  4. Related Work • SWAN-PAM (Streaming over Wireless LAN) (PAM and NOSSDAV) • Disadvantage: Only study the video performance without competing traffic. • Mobility on Wireless Streaming Performance (Williamson paper). • Disadvantage: • Fake AP , IEEE 802.11b. • Need a further analysis for competing traffic. CS577 Advanced Networking Spring 2005

  5. Williamson’s conclusion In Infrastructure wireless network • “I Jumped, do you Jump? “ • Poor Channel condition for one client will degrade the performance of the client at good channel condition. • Access Point (AP) may be the Bottle neck. • The Queue in AP may be fill up by the packets when the wireless channel is poor. CS577 Advanced Networking Spring 2005

  6. Objectives • Correlate performance for Competing Traffic (streaming traffic and TCP Bulk Downloading). • Wireless Link Layer • Network Layer • Application Layer • Focus on • the effects on performance from the competing traffic streaming traffic at bad location (verifying Williamson’s paper) CS577 Advanced Networking Spring 2005

  7. Outline • Introduction • Experimental Methods • Tools and Setup • Experimental Design • Preliminary Results and Analysis CS577 Advanced Networking Spring 2005

  8. Wireless Layer • WRAPI • Signal Strength • Uplink fail/retry fraction • Downlink dup fraction • Typeperf.exe • WLAN capacity • CPU usage • Receiving bandwidth CS577 Advanced Networking Spring 2005

  9. Network Layer • UDP Ping • RTT • Packet loss rate • Wget.exe • TCP throughput • Throughput capacity CS577 Advanced Networking Spring 2005

  10. Application Layer • Media Tracker • Frame Rate • Loss Rate • Scaling Level CS577 Advanced Networking Spring 2005

  11. Experimental Setup • Three runs • Two laptops • Laptop A remains fixed in ‘Good’ Location • Laptop B is in ‘Good’ Location for one set of experiments, and is then moved to a ‘Bad’ Location • Media Server on 100 Mbps WLAN • Access Point serving 802.11g CS577 Advanced Networking Spring 2005

  12. Experimental Setup CS577 Advanced Networking Spring 2005

  13. Experimental Setup • Experiments were conducted during off-hours in the Fuller Sub-Basement • AP bottleneck ensured with preliminary tests • WRAPI used to ensure that ping-pong never occurs • Good Locations were within A21 • Bad Location was at the end of hallway, near service entrance CS577 Advanced Networking Spring 2005

  14. Laptop A Good Location Light UDP Traffic TCP Bulk Download Laptop B Good, Bad Location Light UDP Traffic TCP Bulk Download UDP Stream TCP Stream Experimental Design CS577 Advanced Networking Spring 2005

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