CaSPR Lab


Where-Fi: Secure Synchronization of Periodic Transmissions in Ad Hoc Networks


Next generation mobile ad-hoc applications will revolve around the need of users to share content/presence information with co-located devices. Such information can be aggregated and presented to the user to allow for new experiences. Part of this project consists of two such ``social experiences'': MeCast and Zeitgeist. In MeCast, users can see what their neighbors are doing and can decide to ``follow'' their experience. This includes listening to the same songs, watching the same videos, etc. In Zeitgeist, users are presented with statistics of the most popular content around them, aggregated over desired intervals. The following paper provides more details of MeCast and Zeitgeist.



"Where-Fi: A Dynamic Energy-Efficient Multimedia Distribution Framework for MANETs"
Shivajit Mohapatra, Bogdan Carbunar, Michael Pearce, Rohit Chaudhri, Venu Vasudevan.
In Proceedings of the 15th SPIE/ACM Annual Multimedia Computing and Networking Conference (MMCN), San Jose, January 2008 [26%] [pdf]

Keeping metadata information from neighbors fresh requires frequent information exchanges. This can result in significant energy overheads. To address this issue, in the following papers we propose first a content dissemination protocol (called CPMP) for effectively distributing frequent small meta-data updates between co-located devices using multicast. We then present techniques for synchronizing nodes that periodically broadcast content and presence updates to co-located nodes over an ad-hoc network, where nodes may exhibit Byzantine malicious behavior. Instead of aligning duty cycles, our algorithms synchronize the periodic transmissions of nodes. This allows nodes to save battery power by switching off their network cards without missing updates from their neighbors. We propose several novel attack classes and show that they are able to disrupt synchronization even when launched by a single attacker. Finally, we devise a rating based algorithm (RBA) that rates neighbors based on the consistency of their behavior. By favoring well-behaved nodes in the synchronization process, we show that RBA quickly stabilizes the synchronization process and reduces the number of lost updates by 85\%. Our evaluation also shows that all our algorithms are computationally efficient and, for the setup considered, extend the device lifetime by 30\% over an always-on Wi-Fi scenario.

"Secure Synchronization of Periodic Updates in Ad Hoc Networks"
Bogdan Carbunar, Michael Pearce, Shivajit Mohapatra, Lorren Rittle, Venu Vasudevan, Octavian Carbunar.
IEEE Transactions on Parallel and Distributed Systems (TPDS), Volume 21, Number 8, August 2010 [pdf]

"Byzantine Resilient Synchronization for Content and Presence Updates in MANETs"
Bogdan Carbunar, Michael Pearce, Shivajit Mohapatra, Loren J. Rittle, Venu Vasudevan.
In Proceedings of the 16th IEEE International Conference on Network Protocols (ICNP)[16%], Orlando, October 2008 [pdf]