CWT Research
VT Approaches the Problem by Treating the Radio as a Biological System
Like animals and people they seek their own kind (Other radios with which they want to communicate)
Avoid or outwit enemies (Interfering radios)
Find a place to live (Usable spectrum)
Conform to the etiquette of their society (The Federal Communications Commission)
Make a living (deliver the services that their user wants)
Deal with entirely new situations and learn from experience
History
Joseph Mitola [Mitola, 1999] [Mitola, 2002] invented the basic cognitive radio concept in the late 1990s when he envisioned a CR as a universal and highly intelligent wireless personal digital assistant, operating primarily at the application level. More recently the DARPA XG program extended the concept to allow the CR to operate as an intelligent agent [XG]. Recent work by the Virginia Tech Center for Wireless Telecommunications (VT-CWT) using learning algorithms extended cognition to the MAC (medium access control) and PHY (physical) layers. (See Fig. 2.)
The VT cognitive engine and our work in CR grew directly from NSF award 9987586, "Testbed for High-Speed 'End-to-End' Communications in Support of Comprehensive Emergency Management." In that project we researched communications networks for disaster response applications. A key problem was to develop radios that can find short-lived paths of opportunity and compensate for shortcomings of these paths to deliver optimum performance. An important path characteristic is a phenomenon called rough-surface scattering that takes short (nanosecond) radio pulses and smears them out in time, introducing "pulse stretching" and serious distortion. This had not previously been observed at the frequencies and time scales we use. To investigate these paths we subsequently built a new type of impulse channel sounder. Inspired by the needs of the public safety community and building upon the developments of the disaster response project, we conceived a CR that would make intelligent decisions based on the sounder output, and developed a cognitive engine that will indeed allow a radio to adapt intelligently to unanticipated situations. That cognitive engine is the basis of this proposal. Subsequently we built a proof-of-concept prototype that allows legacy Proxim Tsunami? 5 GHz radios to adapt to changing propagation and interference conditions. This prototype is installed at SAIC's Public Safety Integration Center near Washington, DC, and is available for demonstrations there.
This work under NSF award 9987586 is described in a U.S. patent application for cognitive radio in a network [Patent, 2004], a Ph.D. dissertation, [Rieser, 2004a], and several recent conference presentations and publications [Rondeau, 2004a], [Rieser, 2004b], [Rondeau, 2004b], [Bostian, 2004], [Bostian, 2002].
References
[Bostian, 2002] C.W. Bostian, S.F. Midkiff, W.M. Kurgan, L.W. Carstensen, D.G. Sweeney, and T. Gallagher, "Broadband Communications for Disaster Response", Space Communications, Vol. 18 Nos. 3-4 (double issue), pp. 167-177, 2002.
[Bostian, 2004] C.W. Bostian, S.F. Midkiff, T.M. Gallagher, C.J. Rieser, and T.W. Rondeau. "Rapidly Deployable Broadband Communications for Disaster Response," Sixth International Symposium on Advanced Radio Technologies (SAFECOM Session). Boulder , CO , March 2-4, 2004 .
[Mitola, 1999] J. Mitola, III and G.Q. Maguire, Jr., "Cognitive Radio: Making Software Radios More Personal," IEEE Personal Communications, vol. 6, no. 4, 1999.
[Mitola, 2002] J. Mitola, Software Radio Architecture: Object-Oriented Approaches to Wireless Systems Engineering. New York, NY: John Wiley and Sons, Inc., 2002.
[Patent, 2004] Cognitive Radio Engine Based on Genetic Algorithms in a Network. US Patent Application Serial Number 10/875,619, PCT Number is US04/020,400, Filed June 25, 2004.
[Rieser, 2004a] C.J. Rieser, "Biologically Inspired Cognitive Radio Engine Model Utilizing Distributed Genetic Algorithms for Secure and Robust Wireless Communications and Networking." Available online at http://scholar.lib.vt.edu/theses/available/etd-10142004-023653/.
[Rieser, 2004b] C.J. Rieser, T.W. Rondeau, and C.W. Bostian, "Cognitive Radio Testbed: Further Details and Testing of a Distributed Genetic Algorithm Based Cognitive Engine for Programmable Radios," IEEE MILCOM 2004, Monterey, CA, October 31-November 4, 2004.
[Rondeau, 2004a] T.W. Rondeau, B. Le, C.J. Rieser, and C.W. Bostian, "Cognitive Radios With Genetic Algorithms: Intelligent Control of Software Defined Radios," 2004 Software Defined Radio Forum, Phoenix, AZ. November 15-18, 2004.
[Rondeau, 2004b] T.W. Rondeau, C.J. Rieser, T.M. Gallagher, and C.W. Bostian. "Online Modeling of Wireless Channels with Hidden Markov Models and Channel Impulse Responses for Cognitive Radios," 2004 International Microwave Symposium, Fort Worth, TX, June 6-11, 2004.