Dependence Balance Based Outer Bounds for Gaussian Networks with Cooperation and Feedback

We obtain new outer bounds on the capacity regions of the two-user multiple access channel with generalized feedback (MAC-GF) and the two-user interference channel with generalized feedback (IC-GF). These outer bounds are based on the idea of dependence balance which was proposed by Hekstra and Willems [1]. To illustrate the usefulness of our outer bounds, we investigate three different channel models. We first consider a Gaussian MAC with noisy feedback (MAC-NF), where transmitter k, k = 1, 2, receives a feedback YFk , which is the channel output Y corrupted with additive white Gaussian noise Zk. As the feedback noise variances 2 Zk , k = 1, 2, become large, one would expect the feedback to become useless. This fact is not reflected by the cut-set outer bound. We demonstrate that our outer bound improves upon the cut-set bound for all non-zero values of the feedback noise variances. Moreover, in the limit as 2 Zk , k = 1, 2, our outer bound collapses to the capacity region of the Gau...

• Type: Journal
• Year: 2008
• Where: CORR
• Authors: Ravi Tandon, Sennur Ulukus
• Keywords: CORR 2008, Education, Feedback, Gaussian MAC, Outer Bound