Opening Talk

Cognitive Networks: Throughput, Delay Bounds and Routing Issues


Cognitive Radio Networks (CRNs) are composed of frequency-agile radio devices that allow licensed (primary) and unlicensed (secondary) users to coexist, where secondary users opportunistically access channels without interfering with the operation of primary ones. From the perspective of secondary users, spectrum availability is a time varying network resource over which multi-hop end-to-end connections must be maintained.

Analytical bounds on throughput and transmission delay of secondary users under different assumptions on secondary and primary users traffic statistics in a single channel scenario will be presented.

Then it will be discussed the problem of routing secondary user flows in a CRN with the aim of characterizing optimal sequences of routes over which a secondary flow is maintained. The optimality is defined according to a novel metric that considers the maintenance cost of a route as channels and/or links must be switched due to the primary user activity. Different from the traditional routing problem, the proposed approach considers subsequent path selections. The problem can be formulated as an integer programming optimization model and shown to be of polynomial time complexity in case of full knowledge of primary user activity. The use of heuristic algorithms, to solve the minimum maintenance cost routing problem when information on primary user activity is not complete, will be discussed. Some numerical results will allow to assess the optimality gap of a proposed heuristic routing algorithm.

Speaker: Luigi Fratta

Luigi Fratta received the Doctorate in Electrical Engineering from the Politecnico di Milano, Milano, Italy, in 1966. From 1967 to 1970 he worked at the Laboratory of Electrical Communications, Politecnico di Milano. As a Research Assistant at the Department of Computer Science, University of California, Los Angeles, he participated in data network design under the ARPA project from 1970 to 1971. From November 1975 to September 1976 he was at the Computer Science Department of the IBM Thomas J. Watson Research Center, Yorktown Heights, NY, working on modeling analysis and optimization techniques for teleprocessing systems. In 1979 he was a Visiting Associate Professor in the Department of Computer Science at the University of Hawaii. In the summer of 1981 he was at the Computer Science Department, IBM Research Center, San José, CA, working on local area networks. During the summers of 1983, 1989 and 1992 he was with the Research in Distributed Processing Group, Department of Computer Science, U.C.L.A., working on fiber optic local area networks. During the summer of 1986 he was with Bell Communication Research working on metropolitan area networks. In 1994 he has been Visiting Scientist at NEC Network Research Lab, Japan. In 2000 he has been Visiting Professor at the University of Canterbury, New Zealand. Since 1980 he is a Full Professor at the Dipartimento di Elettronica e Informazione of the Politecnico di Milano. His current research interests include computer communication networks, packet switching networks, multiple access systems, modeling and performance evaluation of communication systems, local area networks, wireless cellular systems and integrated services over IP networks. Dr. Fratta is Fellow of IEEE.

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