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. Existing wireless technologies fall short of meeting the stringent performance requirements of closed-loop control. This paper presents a novel wireless solution, called $\mathsf{\text{GALLOP}}$, for realizing closed-loop control over multi-hop or single-hop networks. $\mathsf{\text{GALLOP}}$ adopts a pragmatic design approach for addressing the challenges of wireless closed-loop control. Key design aspects of $\mathsf{\text{GALLOP}}$ include control-aware bi-directional scheduling for cyclic exchange, robust retransmission techniques based on cooperative multi-user diversity and low-overhead signaling for scalable operation. $\mathsf{\text{GALLOP}}$ has been specifically designed for control loops that are closed over the whole network with dynamics on the order of few milliseconds. Performance evaluation based on extensive system-level simulations and hardware implementation on a Bluetooth 5 testbed demonstrates that $\mathsf{\text{GALLOP}}$ 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.