Prof. Joerg Kliewer
Title: Network Equivalence for Arbitrarily Varying and Compound Channels
Abstract: We address the problem of finding the capacity of noisy networks with either independent point-to-point compound channels (CC) or arbitrarily varying channels (AVC). These channels model the presence of a Byzantine adversary which controls a subset of links or nodes in the network. We derive equivalence results showing that these point-to-point channels with state can be replaced by noiseless bit-pipes without changing the network capacity region. Exact equivalence results are found for the CC model, and for some instances of the AVC, including all nonsymmetrizable AVCs. These results show that a feedback path between the output and input of a CC can increase the equivalent capacity, and that if common randomness can be established between the terminals of an AVC (either by feedback, a forward path, or via a third-party node), then again the equivalent capacity can increase. We also analyze an example involving an AVC for which no fixed-capacity bit-pipe is equivalent. Finally, as a generalization we consider a joint CC-AVC model, where the adversary chooses k channels with a CC-type state and controls the state sequences for each of these channels in an AVC-type fashion. If the network is fully connected we provide a simple expression for the capacity region of the noisy network. We also provide a necessary and sufficient condition for full connectivity, making use of a new condition for an AVC termed overwritability.
Biography: Dr. Joerg Kliewer received the Dipl.-Ing. (MSEE) degree in Electrical Engineering from the Hamburg University of Technology, Hamburg, Germany, in 1993 and the Dr.-Ing. degree (Ph.D.) in Electrical Engineering from the University of Kiel, Kiel, Germany, in 1999, respectively. From 1993 to 1998 he was a Research Assistant at the University of Kiel, Germany, and from 1999 to 2004, he was a Senior Researcher and Lecturer with the same institution. In 2004, he visited the University of Southampton, Southampton, U.K., for one year, and from 2005 until 2007, he was with the University of Notre Dame, Notre Dame, IN, as a Visiting Assistant Professor. From August 2007 until December 2013 he was with New Mexico State University, Las Cruces, NM, as an as an Assistant and most recently as an Associate Professor. In January 2014 he joined the New Jersey Institute of Technology, Newark, NJ, as an Associate Professor. His research interests span coding and information theory, graphical models, and statistical algorithms, which includes application to networked communication and security, data storage, and biology. Dr. Kliewer was the recipient of a Leverhulme Trust Award and a German Research Foundation Fellowship Award in 2003 and 2004, respectively. He was Associate Editor of the IEEE Transactions on Communications from 2008-2014 and now serves as an area editor for the same journal since 2015. He is also member of the editorial board of the IEEE Information Theory Society Newsletter since 2010 and serves as chair of the outreach committee for the same society since 2012.