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Role of Feedback in Interference Networks

Changho Suh, UC Berkeley January 19, 2:00pm. EEB 248

Abstract: Abstract: Traditionally, it is believed that feedback has had little impact on increasing capacity. This is mainly due to Shannon's original result on feedback capacity, where he showed that feedback cannot increase the capacity in point-to-point communication links. Hence the use of feedback has been so far limited to improving the reliability of communication, usually in the form of ARQ.

In this talk, I will present a promising role of feedback in networks. What we have shown is that when there are two interfering point-to-point links, not only can feedback increase capacity of each link, but it can in fact provide an unbounded increase in capacity as the signal-to-noise ratio of the links increases. In the process of deriving this conclusion, we characterize the feedback capacity of the two-user Gaussian interference channel to within 2 bits, an open problem for more than 30 years.

Furthermore, I will show the potential impact of using feedback on practical systems that take feedback cost into account. Specifically, I will present an interesting scenario in the context of multiple (more than 3) interfering point-to-point links, where 1 bit of feedback can provide a capacity increase of an arbitrarily large number of bits. Finally, I will present a striking connection between our problem and many other interesting problems in network information theory field.


Changho Suh received the B.S. and M.S. degrees in electrical engineering from Korea Advanced Institute of Science and Technology in 2000 and 2002, respectively. Since 2006, he has been with the Department of Electrical Engineering and Computer Science in the University of California at Berkeley, where he is pursuing the Ph.D. degree under the supervision of Prof. David Tse. Prior to that, he had been with the Telecommunication R&D Center, Samsung Electronics.

He is a recipient of the Best Student Paper Award of the IEEE International Symposium on Information Theory 2009 and the Outstanding Graduate Student Instructor Award in 2010. He awarded several fellowships: the Vodafone U.S. Foundation Fellowship in 2006 and 2007; Kwanjeong Educational Foundation Fellowship in 2009; and Korea Government Fellowship from 1996 to 2002.

Host: Alex Dimakis, dimakis [at]

Summary of Role of Feedback in Interference Networks

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