[Colloq] REMINDER: PhD Thesis Defense by Xin Liu - **MONDAY, SEPTEMBER 17, 2PM**

[Rachel Kalweit]

College of Computer and Information Science
presents
PhD Thesis Defense by:
Xin Liu

Thesis Title:
Cross Layer Design for Cooperative and Adversarial Wireless Networks

Monday, September 17, 2007
2:00pm
366 West Village H

Abstract
This thesis focuses on developing novel techniques to improve the performance of wireless networks under two communication models: (1) cooperative communication, and (2) communication in the presence of adversaries. The proposed approaches rely on a cross-layer communication paradigm where multiple layers of protocols coordinate to achieve a common goal - e.g. to increase throughput, to improve resiliency to jamming attacks, or to reduce energy consumption.

Wireless communication is broadcast by nature. The positive aspect of this broadcasting property is that it provides an opportunity for wireless nodes to cooperate so that the global performance can be improved significantly. The first part of our work is in such a cooperative setting. The objective is to minimize the energy consumption of delivering information through multihop over the network, since energy efficiency is crucial to extend wireless networks' lifetime. We propose a solution based on a novel communication model which allows wireless nodes to accumulate energy from partially overheard packets. Multiple layers, from the physical layer to the routing layer, are involved in searching for the optimal transmission strategy. We provide a thorough analysis of the minimum energy routing problem under this new model in this thesis.

The negative aspect of this sharing medium characteristic of wireless networks is that it is very easy for adversaries to attack the communication by means of monopolizing, eavesdropping, or jamming. Therefore, the second part of our research aims at increasing wireless networks' resiliency to cross-layer jamming attacks. We propose a novel cross-layer communication architecture in conjunction with fine-designed mechanism-hopping techniques to improve the network robustness against adversaries. Just as the spread spectrum technique thwarts malicious attackers by hopping frequencies in a pseudo-random fashion, our approach foils jamming attacks by adaptively and dynamically switching between different mechanisms at different layers of the stack. We demonstrate the effectiveness of our approach by deriving countermeasures against various cross-layer attacks following the proposed framework and justify them through extensive simulations. We also present multiple mathematical mod
 els for analyzing the impact of jamming, and the interaction between communicating nodes and the jammer.

Thesis committee:
Prof. Ravi Sundaram,  Advisor
Prof. Guevara Noubir, Advisor
Prof. Rajmohan Rajaraman
Prof. Agnes Chan
Dr. Tushar Saxena, Verizon Communications


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