SPEAKER: Surendar Chandra, University of Notre Dame
DATE: Monday, October 1, 2007
TIME: 3:30 – 4:30 p.m.
PLACE: Computer Science Conference Room, Harold Frank Hall Room 1132
Wireless laptops are gradually replacing desktops as the primary computing platform for many users. Traditionally laptops were dependent on services provided by a wired infrastructure. Mobile laptops may be offline for long durations making dependence on infrastructure problematic. Our goal was to understand the viability of collaboration among wireless users without depending on the wired infrastructure. Earlier research efforts did not have the benefit of the critical mass of available wireless devices for their analysis.
We used the observed mobile user behavior in two medium sized universities, Notre Dame and Dartmouth, as the basis for our study. We observed that wireless devices tended to exhibit short durations during which they were available followed by extended durations when they were not available. The churn frequency itself was not high. The node availability exhibited diurnal distribution with far fewer nodes available early in the morning. However, the temporal consistency values were high: both for analyzing the same users availability behavior or for any two pairs of users. Users who were part of the high consistency set can provide better collaborative services.
Next, we analyzed the epidemic propagation rates for varying group sizes. We showed that the propagation can exhibit large delays. On average, a single update can reach about 60\% of the collaborators in about 24 hours while reaching 90\% of the members in over ten days. We improved these propagation durations by carefully selecting the forwarding peers using local information. Unlike Vahdat et al. who used a random node mobility model, our realistic analysis could not achieve 100\% propagation rates even after ten days.
Surendar Chandra is an assistant Professor in the Computer Science and Engineering department at the University of Notre Dame. His research interests are directed towards operating system topics in multimedia, storage, security, networks and sensor systems. He received his Ph.D. in Computer Science from Duke University under the supervision of Carla Schlatter Ellis. He spent 2000-2002 as a faculty member at the University of Georgia. His work was supported by Defense Intelligence Agency, HP, National Science Foundation and Yamacraw. He is the recipient of an NSF CAREER award.
HOST: Kevin Almeroth