Comments on "Feedback stabilization over signal-to-noise ratio constrained channels

The above-named paper obtains in closed-form the infimal signal-to-noise ratio (SNR) required for stabilization of finite-dimensional linear time invariant (LTI) feedback loops, in continuous and discrete-time, for state feedback and output feedback control. The objective of the present note is to prove that the discrete-time output feedback infimal SNR result for stabilization reported in [1, Theorem III.2] is missing a term in delta, the component due to the relative degree of the plant model.