Toronto
Networking Seminar


      



      

      



Understanding Congestion and Flash Crowds in WLANS


      


      
Elizabeth
Belding


      Department of Computer Science


University of California, Santa Barbara


      


      


      
      
Date: 
Friday, March 30,  2pm 


Location: BA1220 (Bahen Center)


      
      


      
Abstract:


      


      Flash
crowds and high concentrations of users in wireless LANs (WLANs) cause
significant interference problems and unsustainable load at access
points. This leads to poor connectivity for users, severe performance
degradation, and possible WLAN collapse.  To validate this
claim, we will discuss two case studies of large, heavily loaded
operational WLANs. These studies provide significant insight into the
degraded performance and collapse of a WLAN during heavy use. To
address these problems, we present IQU, a practical queue-based user
association management system for heavily loaded WLANs. IQU grants
users fair opportunities to access the WLAN while maintaining high
overall throughput, even when the WLAN is heavily loaded. The basic
premise of IQU is to control user associations with the WLAN through
request queues and work period allocations.  Through a
prototype implementation, we demonstrate that IQU significantly
improves network throughput under heavy load; the tradeoff is that
users have to wait for network access.  We explore the impact
of IQU parameters on system performance, and validate the robustness of
IQU under heavy load conditions. Through IQU, WLANs can be utilized
efficiently and network collapse prevented.


      
      
Bio:


      


      Elizabeth
M.
Belding is an Associate Professor in the Department of Computer Science
at the University of California, Santa Barbara.  Elizabeth's
research
focuses on mobile networking, specifically mesh networks, multimedia,
monitoring, and advanced service support.  She is the founder
of the
Mobility Management and Networking (MOMENT) Laboratory
(http://moment.cs.ucsb.edu) at UCSB.  Elizabeth is the author
of over
50 papers related to mobile networking and has served on over 40
program committees for networking conferences.  Elizabeth
served as the
TPC Co-Chair of ACM MobiCom 2005 and IEEE SECON 2005, and is currently
the TPC Co-Chair of ACM MobiHoc 2007.  She also serves on the
editorial
board for the IEEE Transactions on Mobile Computing. 
Elizabeth is the
recipient of an NSF CAREER award, and a 2002 Technology Review 100
award, awarded to the world's top young investigators.  See
http://www.cs.ucsb.edu/~ebelding for further details.