A new entropy power inequality
IEEE Transactions on Information Theory
Elements of information theory
Elements of information theory
On Cooperation Via Noisy Feedback
IZS '06 Proceedings of the 2006 International Zurich Seminar on Communications
Dependence Balance Based Outer Bounds for Gaussian Networks With Cooperation and Feedback
IEEE Transactions on Information Theory
Hi-index | 0.00 |
We provide a new outer bound on the capacity region of the two-user Gaussian multiple access channel (MAC) with AWGN-corrupted feedback. Our outer bound is based on the idea of dependence balance due to Hekstra and Willems [1]. Evaluating our outer bound is non-trivial as it involves taking a union over joint densities of three random variables, one of which is an auxiliary random variable. We resolve this difficulty by proving that it is sufficient to consider jointly Gaussian random variables when evaluating our outer bound. As the feedback noise variances become large, our outer bound collapses to the capacity region of the Gaussian MAC without feedback, thereby yielding the first non-trivial result for a Gaussian MAC with noisy feedback. Furthermore, as the feedback noise variances tend to zero, our outer bound collapses to the capacity region of the Gaussian MAC with noiseless feedback, which was established by Ozarow [2]. For all non-zero, finite values of the feedback noise variances, our outer bound strictly improves upon the cut-set outer bound.