Adaptive Tuning of IEEE 802.11 MAC Access Delay for Improving Control Performance in Cyber-Physical Systems

Abstract

In this paper, we study the problem of tuning medium access control (MAC) parameters in IEEE 802.11 to improve control performance in cyber-physical systems (CPS). Our main idea is to propose an algorithm that guarantees control performance and to adjust MAC parameters that affect the delay distribution. In addition, we exploit the fact that control performance depends more on delay distribution than just on the average delay. In legacy networked control systems (NCS) design, the network delay is mostly considered as a random delay distribution, whereas the real network delay has different distribution features like the long-tailed characteristic in IEEE 802.11, so the system model cannot be accurate in the real world. We make two contributions to this field of research: i) Through the analysis of the IEEE 802.11 MAC access delay model, we control the MAC parameters by reducing the delay variance, that can be critical to control performance as well as the average delay. We propose a MAC controller that controls the MAC parameters with our algorithm. ii) In order to validate our approach, we implement a CPS testbed, in which a remote controller controls a drone via an IEEE 802.11 network. A CPS testbed based simulation is also completed with experiments. We examine the absolute average tracking error of the controller for a given reference. Our results show that the proposed approach can significantly improve control performance. ⓒ 2016 DGIST