Age of Information for Actuation Update in Real-Time Wireless Control Systems

In this paper, we introduce a generalized definition of age of information (AoI) for actuation update in real-time wireless control systems. In such a system, a general queueing model, i.e., M/M/1/1 queueing model, is used to describe the actuation update, in which the sampling packets arrive at the remote controller following the Poisson process, the process from the controller to the actuator follows the exponential distribution, and the actuation intends to update at the actuator at the predictive time. Then, the initial time of the AoI for the new actuation update is the predictive time for the latest update, which is significantly different from the traditional calculation in status update. By the relationship between communication time from the controller to the actuator and predictive time, the AoI calculation falls into two cases, where the conventional AoI in status update is a specific case in this paper. Simulation results show the performance of our method.