  Networked control systems (NCSs) are feedback control loops that are closed
over a communication network. Emerging applications, such as telerobotics,
drones and autonomous driving are the most prominent examples of such systems.
Regular and timely information sharing between the components of NCSs is
essential to fulfill the desired control tasks, as stale information can lead
to performance degradation or even physical damage. In this work, we consider
multiple heterogeneous NCSs that transmit their system state over a shared
physical wireless channel towards a gateway node. We conduct a comprehensive
experimental study on selected MAC protocols using software-defined radios with
state-of-the-art (SotA) solutions that have been designed to increase
information freshness and control performance. As a significant improvement
over the SotA, we propose a novel contention-free algorithm that is able to
outperform the existing solutions by combining their strengths in one protocol.
In addition, we propose a new metric called normalized mean squared error that
maps the age of information to a dimensionless quantity that captures the
expected value of a control system's next transmission. We demonstrate its
adoption and effectiveness for wireless resource scheduling in a case study
involving multiple inverted pendulums. From our experimental study and results,
we observe that value-aware prioritization of the sub-systems contributes to
minimizing the negative effects of information staleness on control
performance. In particular, as the number of devices increases, the benefit of
control-awareness to the quality of control stands out when compared to
protocols that focus solely on maximizing information freshness.
