  In this paper we address the question of robustness of critical bit rates for
the stabilization of networked control systems over digital communication
channels. For a deterministic nonlinear system, the smallest bit rate above
which practical stabilization (in the sense of set-invariance) can be achieved
is measured by the invariance entropy of the system. Under the assumptions of
chain controllability and a uniformly hyperbolic structure on the set of
interest, we prove that the invariance entropy varies continuously with respect
to system parameters. Hence, in this case the critical bit rate is robust with
respect to small perturbations.
