Multicasting for cascaded fault-tolerant Wireless Networked Control Systems in noisy industrial environments

This paper studies a Wireless Networked Control System based on IEEE´s 802.11b Wi-Fi standard protocol consisting of two identical workcells with zero meter inter-cell distance. It is first shown how to improve system performance and increase the amount of noise that the system can tolerate without violating delay requirements or dropping control packets. Different noise models were studied. It was proved that increasing the short retry threshold increases system tolerance to noise. It was then shown through OPNET simulations that the two cell model is fault-tolerant at the controller level when either unicasting or multicasting is used. However, for the system to operate correctly in the presence of noise, multicasting had to be used.