  We consider an additive Gaussian channel with additive Gaussian noise
feedback. We derive an upper bound on the n-block capacity (defined by Cover
[1]). It is shown that this upper bound can be obtained by solving a convex
optimization problem. With stationarity assumptions on Gaussian noise
processes, we characterize the limit of the n-block upper bound and prove that
this limit is the upper bound of the noisy feedback (shannon) capacity.
