Effects of a Bad Channel on the overall WLAN Performance.

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