Efforts to create modern wireless networks have occasionally suffered from approaches that seeks to replace static resource allocation schemes with fully dynamic schemes, failing to adequately compensate for the benefits associated with stable, predictable resource allocation, such as reduced communication overhead and computational complexity. In this talk, I describe ongoing research on channel assignment in multihop, multitransceiver wireless networks that demonstrates that many of the advantages of dynamic assignment are available via a hybrid approach that builds a static network topology and then enhances it dynamically in response to network traffic. Then, I will briefly describe future work that seeks to apply a broadly similar approach to spectrum assignment.

In the first portion of the talk, I describe a proposed channel assignment scheme for cognitive radio networks that balances the need for topology adaptation to maximize flow rate and the need for a stable baseline topology to support network connectivity. We focus on networks in which nodes are equipped with multiple radios or transceivers, each of which can be assigned to a channel. First, we assign channels independently of traffic, to achieve basic network connectivity and support light loads such as control traffic, and, second, we dynamically assign channels to the remaining transceivers in response to traffic demand. We formulate the problem as a two-stage mixed integer linear program (MILP) and show that with this two-stage approach we can achieve performance comparable to a fully dynamic channel assignment scheme while preserving a static, connected topology. I describe ongoing work to implement this strategy via distributed channel assignment algorithms.

In the second portion of the talk, I will describe a similar problem faced in the realm of spectrum assignment. Classical, static approaches to spectrum allocation are extremely inefficient, but provide a stable environment for wireless systems. Dynamic spectrum access (DSA) has been a popular research topic in the last five years, but deployment of DSA systems has been slowed by difficult technical challenges at multiple layers of the protocol stack and delayed adoption by spectrum regulators. I will briefly describe future research which will investigate hybrid approaches with the potential to offer both stability and improved efficiency.

Bio: Allen B. MacKenzie received his bachelor's degree in Electrical Engineering and Mathematics from Vanderbilt University in 1999. In 2003 he earned his Ph.D. in electrical engineering at Cornell University and joined the faculty of the Bradley Department of Electrical and Computer Engineering at Virginia Tech, where he is now an associate professor.

Prof. MacKenzie's research focuses on wireless communications systems and networks. His current research interests include cognitive radio and cognitive network algorithms, architectures, and protocols and the analysis of such systems and networks using game theory. His past and current research sponsors include the National Science Foundation, the Defense Advanced Research Projects Agency, and the National Institute of Justice.

Prof. MacKenzie is an associate editor of the IEEE Transactions on Communications and the IEEE Transactions on Mobile Computing. He also serves on the technical program committee of several international conferences in the areas of communications and networking, and is a regular reviewer for journals in these areas.

Prof. MacKenzie is a senior member of the IEEE and a member of the ASEE and the ACM. In 2006, he received the Dean's Award for Outstanding New Assistant Professor in the College of Engineering at Virginia Tech. He is the author of more than 45 refereed conference and journal papers and the co-author of the book Game Theory for Wireless Engineers.

The Computer Science Seminar Lecture Series is a collection of weekly lectures about topics at the forefront of contemporary computer science research, given by speakers knowledgeable in their field of study. These speakers come from a variety of different technical and geographic backgrounds, with many of them traveling from other universities across the globe to come here and share their knowledge. These weekly lectures were recorded with an HD video camera, edited with Apple Final Cut Pro X, and outputted in such a way that the resulting .mp4 video files were economical to store and stream utilizing the university's limited bandwidth and disk space resources.