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The adoption of dense wireless sensor networks in industrial plants is mandatorily paired with the development of methods and tools for connectivity prediction. These are needed to certify the quality (or reliability) of the network information flow in industrial scenarios which are typically characterized by harsh propagation conditions. Connectivity prediction must account for the possible coexistence of heterogeneous radio-access technologies, as part of the Industrial Internet of Things (IIoT) paradigm, and easily allow postlayout validation steps. The goal of this paper is to provide a practical evaluation of relevant coexistence problems that may occur between industrial networks employing standards such as Wireless HART IEC 62591, IEEE 802.15.4, and IEEE 802.11. A number of coexistence scenarios are experimentally tested using different radio platforms. For each case, experimental results are analyzed to assess tolerable interference levels and sensitivity thresholds for different configurations of channel overlapping. Finally, the problem of over-the-air spectrum sensing is investigated in real scenarios with heterogeneous industrial networks to enable a cognitive resource allocation that avoids intolerable interference conditions.

Wireless telemetry systems for remote monitoring and control of industrial processes are now becoming a relevant topic in the field of networked control. Wireless closed-loop control systems have stricter delay and link reliability requirements compared to conventional sensor networks for open-loop monitoring and call for the development of advanced network architectures. By following the guidelines introduced by recent standardization, this paper focuses on the most recent technological advances to enable wireless networked control for tight closed-loop applications with cycle times below 100 ms. The cooperative network paradigm is indicated as the key technology to enable cable replacing even in critical control applications. A cooperative communication system enables wireless devices placed at geographically separated locations to act as a virtual ensemble of antennas that creates a virtual multiple-antenna-distributed system. A proprietary link-layer protocol/based on the IEEE 802.15.4 physical layer has been developed and tested in an indoor environment characterized by non-line-of-sight (NLOS) propagation and dense obstacles. The measurements obtained from the testbed evaluate experimentally the benefits (and the limitations) of cable replacing in critical process control.

Wireless sensor networks for critical industrial applications are becoming a remarkable technological paradigm. Large-scale adoption of the wireless connectivity in the field of industrial monitoring and process control is mandatorily paired with the development of tools for the prediction of the wireless link quality to mimic network planning procedures similar to conventional wired systems. In industrial sites, the radio signals are prone to blockage due to dense metallic structures. The layout of scattering objects from the existing infrastructure influences the received signal strength observed over the link and thus the quality of service (QoS). This paper surveys the most promising wireless technologies for industrial monitoring and control and proposes a novel channel model specifically tailored to predict the quality of the radio signals in environments affected by highly dense metallic building blockage. The propagation model is based on the diffraction theory, and it makes use of the 3D model of the plant to classify the links based on the number and density of the obstructions surrounding each individual radio device. Accurate link classification opens the way to the optimization of the network deployment to guarantee full end-to-end connectivity with minimal on-site redesign. The link-quality prediction method based on the classification of propagation conditions is validated by experimental measurements in two oil refinery sites using industry standard ISA SP100.11a compliant devices operating at 2.4 GHz.