  Networked control systems (NCSs) are an example of task-oriented
communication systems, where the purpose of communication is real-time control
of processes over a network. In the context of NCSs, with the processes sending
their state measurements to the remote controllers, the deterioration of
control performance due to the network congestion can be partly mitigated by
shaping the traffic injected into the network at the transport layer (TL). In
this work, we conduct an extensive performance evaluation of selected TL
protocols and show that existing approaches from communication and control
theories fail to deliver sufficient control performance in realistic network
scenarios. Moreover, we propose a new semantic-aware TL policy, which uses the
process state information to filter the most relevant updates and the network
state information to prevent delays due to network congestion. The proposed
mechanism is shown to outperform all the considered TL protocols with respect
to control performance.
