  In Wireless Networked Control Systems (WNCSs), the feedback control loops are
closed over a wireless communication network. The proliferation of WNCSs
requires efficient network resource management mechanisms since the control
performance is significantly affected by the impairments caused by network
limitations. In conventional communication networks, the amount of transmitted
data is one of the key performance indicators. In contrast, in WNCSs, the
efficiency of the network is measured by its ability to facilitate control
applications, and the data transmission rate should be limited to avoid network
congestion. In this work, we consider an experimental setup where multiple
control loops share a wireless communication network. Our testbed comprises up
to five control loops that include Zolertia Re-Mote devices implementing IEEE
802.15.4 standard. We propose a novel relevance- and network-aware transport
layer (TL) scheme for WNCSs. The proposed scheme admits the most important
measurements for the control process into the network while taking current
network conditions into account. Moreover, we propose a mechanism for the
scheme parameters adaptation in dynamic scenarios with unknown network
statistics. Unlike the conventional TL mechanisms failing to provide adequate
control performance due to either congestion in the network or inefficient
utilization of available resources, our method prevents network congestion
while keeping the control performance high. We argue that relevance- and
network-awareness are critical components of network protocol design to avoid
control performance degradation in practice.
