Co-Design of Communication and Control Based on Age of Loop Information in Industrial IoT

In the Industrial Internet of Things (IIoT), timely and precise information exchange by communication system is crucial. However, the performance of communication system and control system are always deeply coupled. Therefore, it is of great significance to explore the co-design of communication and control to optimize the performance of the entire system. In this work, to capture the timely and precise information exchange in IIoT, we propose an indicator that can simultaneously reflect the passage of time and changes in transmission rounds during the transmission of uplink and downlink - Age of Loop Information (AoLI). Our goal is to minimize the AoLI, by finding out the optimal communication parameters (i.e., block length and maximum transmission rounds) and control convergence rate while meeting reliability requirements. To solve this problem, we first convert the communication reliability requirement into a control convergence rate constraint, and thus the control convergence rate can be resolved. Then, we obtain a closed-form expression for the upper bound of the average AoLI. Finally, we propose an iterative algorithm to find the optimal communication parameters. The numerical results show that our proposed communication and control co-design method has significant performance improvements in terms of delay and control cost.