  Age-of-Information (AoI) is a recently introduced metric for network
operation with sensor applications which quantifies the freshness of data. In
the context of networked control systems (NCSs), we compare the worth of the
AoI metric with the value-of-information (VoI) metric, which is related to the
uncertainty reduction in stochastic processes. First, we show that the
uncertainty propagates non-linearly over time depending on system dynamics.
Next, we define the value of a new update of the process of interest as a
function of AoI and system parameters of the NCSs. We use the aggregated update
value as a utility for the centralized scheduling problem in a cellular NCS
composed of multiple heterogeneous control loops. By conducting a simulative
analysis, we show that prioritizing transmissions with higher VoI improves
performance of the NCSs compared with providing fair data freshness to all
sub-systems equally.
