# Toronto Networking Seminar

## Connectivity Properties of Cooperative Wireless Ad Hoc Networks

### Abstract:

Extensive research has demonstrated the potential improvement in physical layer performance when multiple radios transmit concurrently in the same radio channel. We consider here how such cooperation affects the required node density for full connectivity and percolation for different values of the path loss exponent, $\alpha$ in large wireless ad hoc networks. For one-dimensional (1-D) extended networks, in contrast to non-cooperative networks, full connectivity occurs for any node density when $\alpha$ <= one. Conversely, there exist unconnected nodes with probability one when $\alpha$ > 1, and the network does not percolate for any node density if $\alpha$ > 2. The existence of percolation remains an open problem for 1 < $\alpha$ <= 2 in the one-dimensional (1-D) case. In two-dimensional (2-D) extended networks with non-coherent cooperation, full connectivity is achieved for any node density with $\alpha$ <= 2. Conversely, there exist disconnected nodes with probability one when $\alpha$ > 2; however the cooperative network percolates for node densities above a threshold which is strictly less than that of the non-cooperative network.

The above results hold in the presence of receiver cooperation. We also present results for the case that senders cooperate but receivers do not.

Joint work with D. Goeckel, B. Liu, L. Wang, C. Westphal

### Bio:

Don Towsley received a B.A. degree in physics and a Ph.D. degree in computer science, both from University of Texas University. He is currently a Distinguished University Professor in the Department of Computer Science at the University of Massachusetts - Amherst, where he co-directs the Networking Research Laboratory. Professor Towsley has been a Visiting Scientist at AT&T Labs - Research, IBM Research, INRIA , Microsoft Research Cambridge, and the University of Paris 6.

Dr. Towsley's research interests include network measurement, modeling, and analysis. He served as Editor-in-Chief of the IEEE/ACM Transactions on Networking and is on the editorial boards of Journal of the ACM and IEEE Journal of Selected Areas in Communications. He is also currently Chair of the IFIP Working Group 7.3 on computer performance measurement, modeling, and analysis. He has also served on numerous editorial boards including those of IEEE Transactions on Communications and Performance Evaluation. He has been active in the program committees for numerous conferences including IEEE Infocom, ACM SIGCOMM, ACM SIGMETRICS, and IFIP Performance conferences for many years, and has served as Technical Program Co-Chair for ACM SIGMETRICS and Performance conferences.

Dr. Towsley has received the 2007 IEEE Koji Kobayashi Computer and Communications Award , the 2007 ACM SIGMETRICS Achievement Award, the 1999 IEEE Communications Society William Bennett Award, and several conference and workshop best paper awards. He is also the recipient of the University of Massachusetts Chancellor's Medal and the Outstanding Research Award from the College of Natural Science and Mathematics at the University of Massachusetts. He is one of the founders of the Computer Performance Foundation. He has twice received IBM Faculty Fellowship Awards, and is a Fellow of the IEEE and the ACM.

### Host of the talk

Peter Marbach (marbach@cs.toronto.edu)