We explore the interplay between interference, cooperation and connectivity in heterogeneous wireless interference networks. Specifically, we consider a 4-user locallyconnected interference network with pairwise clustered decoding and show that its degrees of freedom (DoF) are bounded above by 125 . Interestingly, when compared to the corresponding fully connected setting which is known to have 83 DoF, the locally connected network is only missing interference-carrying links, but still has lower DoF, i.e., eliminating these interferencecarrying links reduces the DoF. The 125 DoF outer bound is obtained through a novel approach that translates insights from interference alignment over linear vector spaces into corresponding sub-modularity relationships between entropy functions.
Syed Ali Jafar received the B. Tech. degree in Electrical Engineering from the Indian Institute of Technology (IIT), Delhi, India in 1997, the M.S. degree in Electrical Engineering from California Institute of Technology (Caltech) , Pasadena USA in 1999, and the Ph.D. degree in Electrical Engineering from Stanford University, Stanford, CA USA in 2003. His industry experience includes positions at Lucent Bell Labs , Qualcomm Inc. and Hughes Software Systems. He is currently an Associate Professor in the Department of Electrical Engineering and Computer Science at the University of California Irvine, Irvine, CA USA. His research interests include multiuser information theory and wireless communications.
Dr. Jafar received the NSF CAREER award in 2006, the ONR Young Investigator Award in 2008, the IEEE Information Theory Society paper award in 2009 and the Engineering School Fariborz Maseeh Outstanding Research Award in 2010. He received the UC Irvine Engineering Faculty of the Year award in 2006 and the UC Irvine EECS Professor of the Year Award twice, in 2009 and 2011, for excellence in teaching. Dr. Jafar was the inaugural instructor for the First Canadian School of Information Theory in 2011, a plenary speaker for the IEEE Communication Theory Workshop 2010 and SPCOM 2010, and a Visiting Erskine Fellow to the University of Canterbury New Zealand. He served as Associate Editor for IEEE Transactions on Communications 2004-2009, for IEEE Communications Letters 2008-2009 and is currently serving as Associate Editor for IEEE Transactions on Information Theory.