Closing the Loop: A High-Performance Connectivity Solution for Realizing Wireless Closed-Loop Control in Industrial IoT Applications

High-performance real-time wireless connectivity is at the heart of the Industrial Internet of Things (IIoT). Realizing wireless closed-loop control is crucial for various mission-critical IIoT systems. The existing wireless technologies fall short of meeting the stringent performance requirements of the closed-loop control. This article presents a novel wireless solution, called generalized closed-loop control of processes (GALLOP), for realizing closed-loop control over multihop or single-hop networks. GALLOP adopts a pragmatic design approach for addressing the challenges of wireless closed-loop control. The key design aspects of GALLOP include control-aware bidirectional scheduling for cyclic exchange, robust retransmission techniques based on cooperative multiuser diversity, and low-overhead signaling for scalable operation. GALLOP has been specifically designed for control loops that are closed over the whole network with dynamics on the order of a few milliseconds. The performance evaluation based on extensive system-level simulations and hardware implementation on a Bluetooth 5 testbed demonstrates that GALLOP provides high-performance connectivity with very low and deterministic latency, very high reliability and high scalability, to meet the stringent requirements of wireless closed-loop control for versatile IIoT applications.