In this talk, we present new techniques that leverage the wireless medium in facilitating secure communications in the presence of eavesdroppers. First, we consider the secure transmission of information over an ergodic fading channel with long coherence intervals. The secrecy capacity of such a system is characterized under different assumptions on the available channel state information. We then propose a low-complexity on/off power allocation strategy which becomes asymptotically optimal as the average SNR grows. Remarkably, our results reveal the positive impact of fading on the secrecy capacity and establish the critical role of rate adaptation in enabling secure communications over slow fading channels. In the second part of the talk, we discuss the utility of user cooperation in establishing secure communication links. More specifically, we construct novel cooperation strategies for the relay channel with an eavesdropper. One of the proposed strategies, i.e., noise forwarding, is used to illustrate the deaf helper phenomenon, where the relay is able to create a secure source-destination channel while being totally ignorant of the transmitted message. Throughout the talk, the gain offered by the proposed strategies is proved theoretically and validated by numerical examples.

This is a joint work with Lifeng Lai and Praveen Gopala Kumar.

Host: Ashu Sabharwal

Biography of Hesham El Gamal:
Hesham El Gamal received the B.S. and M.S. degrees in Electrical Engineering from Cairo University, Cairo, Egypt, in 1993 and 1996, respectively, and the Ph.D. degree in Electrical and Computer Engineering from the University of Maryland at College Park, MD, in 1999. From 1993 to 1996, he served as a Project Manager in the Middle East Regional Office of Alcatel Telecom. From 1996 to 1999, he was a Research Assistant in the Department of Electrical and Computer Engineering, the University of Maryland at College Park, MD. From February 1999 to December 2000, he was with the Advanced Development Group, Hughes Network Systems (HNS), Germantown, MD, as a Senior Member of the Technical Staff. In the Fall of 1999, he served as a lecturer at the University of Maryland at College Park. In January 2001 he joined the ECE Department at the Ohio State University where he is now an Associate Professor. He held visiting appointments at UCLA (Fall 2002, Winter 2003) and Institut Eurecom (Summer 2003).

He is a recipient of the HNS Annual Achievement Award (2000), the OSU College of Engineering Lumley Research Award (2003), the OSU Electrical Engineering Department FARMER Young Faculty Development Fund (2003-2008), and the National Science Foundation CAREER Award (2004). He holds 5 U.S. patents and has eight more patent applications pending. He is a Senior Member of the IEEE and currently serves as an Associate Editor for "Space-Time Coding and Spread Spectrum" for the IEEE Transactions on Communications.