# Invariance Properties of Controlled Stochastic Nonlinear Systems under Information Constraints

## TL;DR

This paper investigates the limits of stabilizing stochastic nonlinear systems over communication channels by developing new entropy-based bounds using ergodic theory, enhancing understanding of information requirements for stability.

## Contribution

It introduces a novel ergodic-theoretic approach and a new entropy concept to derive refined bounds on information transmission needed for system stabilization.

## Key findings

- Derived fundamental bounds on communication requirements for stability.
- Developed a new entropy measure tailored for AMS analysis.
- Provided more versatile and refined bounds compared to previous methods.

## Abstract

Given a stochastic nonlinear system controlled over a possibly noisy communication channel, the paper studies the largest class of channels for which there exist coding and control policies so that the closed-loop system is stochastically stable. The stability criterion considered is asymptotic mean stationarity (AMS). We develop a general method based on ergodic theory and probability to derive fundamental bounds on information transmission requirements leading to stabilization. Through this method we develop a new notion of entropy which is tailored to derive lower bounds for asymptotic mean stationarity for both noise-free and noisy channels. The bounds obtained through probabilistic and ergodic-theoretic analysis are more refined in comparison with the bounds obtained earlier via information-theoretic methods. Moreover, our approach is more versatile in view of the models considered and allows for finer lower bounds when the AMS measure is known to admit further properties such as moment bounds.