User Association and Communication-Computation Co-Design for Wireless Control Networks

This paper studies a wireless networked control system with multiple base stations (BSs) cooperatively coordinating the wireless control of a number of subsystems each consisting of a plant, a sensor, and an actuator. In this system, each sensor first offloads the sensing data to its associated BS, which then employs mobile edge computing (MEC) to process the data and sends the command signals back to the actuator for remote control. We consider the time-division-multiple-access (TDMA) service protocol among different BSs, in which different BSs implement the uplink data collection and downlink command broadcasting over orthogonal time slots. We also employ the massive multiple-input multiple-output (MIMO) at BSs, based on which each BS serves its associated subsystems over the same time-frequency resources. We jointly design the BS-sensor/actuator associations and sensors/actuators as well as the joint communication and computation resource allocation to minimize the closed-loop control latency of the multiple subsystems while ensuring control stability. The optimization considers the transmission uncertainty caused by the hyper reliable and low-latency communications (HRLLC) and the inter-user interference, as well as the communication and computation resource constraints. To solve the non-convex problem, we develop an efficient algorithm by employing the techniques of alternating optimization and successive convex approximation (SCA). Numerical results show that the proposed joint BS-sensor/actuator association and resource allocation design significantly outperforms other benchmark schemes.