A Study on Multiple Access Schemes for Wireless Control over the IEEE 802.15.4 Beacon-Enabled Mode

In wireless feedback control systems with multiple plants, state information and control information are sent over a shared communication channel. The IEEE 802.15.4 beaconenabled mode has a contention access period (CAP) and a contention free period (CFP). In the CAP, carrier sense multiple access/collision avoidance (CSMA/CA) is used. In the CFP, time division multiple access (TDMA) is used. This paper considers wireless control over the IEEE 802.15.4 beacon-enabled mode and discusses how to use the CAP and the CFP. We propose two schemes that assign the plants to the CAP and the CFP; one is based on communication success/failure and the other is based on control error between state information and the target value. We show that the proposed assignment schemes improve the quality of an overall plant control compared with random assignment. In addition, the scheme based on the control layer achieves better control quality than that based on the communication layer.