An Experimental Framework for Age of Information and Networked Control via Software-Defined Radios

Cyber-physical systems (CPS) classify the set of applications where a physical, real-time process is monitored and controlled over a communication network. In CPS, providing fresh information is essential to satisfy the requirements imposed by time-critical applications. In order to quantify information freshness, age of information (AoI) has been proposed and employed as a metric for cross-layer design. In contrast to the vast majority of AoI-research, there have been a few attempts to measure AoI in real deployment scenarios. However, those contain either unalterable communication stack or are not publicly available for possible extensions. In this work, we present an open-source, experimental framework that is using software-defined radios for wireless communication. Our implementation contains centralized resource allocation using beacon packets and various conventional packet management policies such as first come first serve and last come first serve. In a case study with multiple inverted pendulums sharing a wireless channel, we show how the communication stack can be tailored to keep the information fresh in the network. We present the performance of feedback control loops in relation to AoI and show the benefit of keeping the information fresh on realistic CPS applications.