Elza Erkip
Associate Professor of Electrical and Computer Engineering
Wireless communication systems suffer from fading and multipath distortion, as well as interference caused by multiple users operating over a limited bandwidth. Cooperation of users, by enabling wireless terminals to assist each other in transmitting information to their desired destinations, provides a good solution to the problems that current wireless technologies face. At the physical layer, terminals overhear one another’s signals, process and retransmit to form a virtual antenna array. Through cooperation, it is possible to obtain the spatial diversity benefits of multi-input multi-output (MIMO) systems without necessarily having a physical antenna array at each terminal. Furthermore, unlike MIMO systems, cooperation is able to successfully mitigate shadow fading. Cooperative communication techniques can easily adapt to the changing environment by opportunistically redistributing network resources such as energy and bandwidth. Incorporating the notion of cooperation at the medium access control (MAC) layer extends the benefits to large networks resulting in high throughput, low delay, reduced interference, low transmitted power and extended coverage. Cross-layer design between the application layer and the physical layer enables high quality multimedia transmission over cooperative wireless links.
Our work in this area spans multiple layers of the protocol stack including physical, MAC, networking and application layers as well as cross-layer design. We are interested the theory of cooperative networking (such as information theoretic aspects) as well as implementation (such as a cooperative networking testbed). Our paper “User cooperation-diversity: Part I and II” won 2004 Communications Society Stephen O. Rice Paper Prize in the Field of Communications Theory, as the best original paper published in IEEE Transactions on Communications in 2003. The paper “Diversity-multiplexing tradeoff in half-duplex relay systems” was selected as the best paper of the Communication Theory Symposium of ICC 2007.
This research is partially funded by NSF, Philips, WICAT, CATT and Othmer Institute for Interdisciplinary Studies.
