# Technical Program

## Paper Detail

 Paper ID S.3.4 Paper Title New Formulas of Ergodic Feedback Capacity of AGN Channels Driven by Stable and Unstable Autoregressive Noise Authors Christos Kourtellaris, Charalambos D. Charalambous, University of Cyprus, Cyprus; Sergey Loyka, University of Ottawa, Canada Session S.3: Channels with Feedback Presentation Lecture Track Shannon Theory Manuscript Click here to download the manuscript Virtual Presentation Click here to watch in the Virtual Symposium Abstract In this paper we characterize the feedback capacity of Additive Gaussian Noise (AGN) channels driven by stable and unstable autoregressive noise, for time-invariant feedback codes (channel input distributions). For stable (resp. unstable) channel noise we identify necessary and sufficient conditions for the optimal input process to induce asymptotic stationarity and ergodicity of the channel output (resp. innovations) process. We call this the {\emph{ergodic feedback capacity}}. From our characterization follows the surprising result: for a time-invariant unit memory Gaussian autoregressive noise AR($c$), $c\in (-\infty,\infty)$, (i) feedback does not increase capacity for the region with $c\in (-1,1)$ and certain unstable $c$, and total transmit power $\kappa \in [0,\infty)$, and (ii) feedback increases capacity for the compliment of the region of values of $(c, \kappa)$, not covered in (i).