Control over Low-Power Wide-Area Networks

There has been a growing interest to adopt low-power wide-area network technology, specially LoRa, for industrial control applications. Its machine-to-machine communication capabilities can enable management of large-area applications (e.g., oil fields over hundreds of km
²
) or process plants that are often positioned far from the central operations center, at inconvenient or hazardous locations in difficult terrain or offshore. While recent works have studied real-time communication over LoRa, they have not considered optimizing control performance. To optimize control performance, industrial automation needs a co-design of real-time scheduling and control. Such a co-design, in general, is highly challenging due to complex dependencies between control performance, plant dynamics, and real-time communication. Existing co-design approaches for other wireless domains are not applicable to LoRa network. LoRa nodes are extremely power-constrained hindering frequent communication and scale. In this paper, we propose a highly energy-efficient and scalable framework for real-time scheduling and control co-design for a LoRa network. By taking into account LoRa characteristics, the co-design approach entails state-aware communication and control to dynamically update the sampling rates while meeting real-time constraints. To minimize communication and synchronization overhead, the co-design is decomposed through a partitioned scheduling. We consider co-design in each partition of the control loops by developing a new schedulability condition. The proposed scheduling-control co-design solution dynamically determines the sampling rates of the sensors to optimize control performance. Simulations based on NS-3 and a custom control script show that our co-design approach minimizes control cost at least by 80% as compared to the baselines.