Simulation of control loops in wireless networks: Relating QoS with QoC

Considering the flexibility of network-based control systems and the wide adoption of wireless IP networks, the relationship between Quality of Service (QoS) and Quality of Control (QoC) parameters is studied in a simple control loop implemented over a wireless ad hoc network. This relationship is investigated using ns-2 simulator in three scenarios: static without packet loss, static with packet loss and mobile. The first scenario was compared to a case study for wired networks presented in the literature. Similar results were obtained, according to the prediction that different packet-switched technologies would present similar results because the concepts of QoS parameters are general enough. Results related to the other two scenarios qualitatively show QoC problems that appear due to the high utilization rate of the network and route disruption due to mobility. These problems can be summarized by the “inertia” of the controlled variable. A proof-of-concept experiment was also implemented to complement and to evaluate simulations.