# Industrial IoT Monitoring: Technologies and Architecture Proposal
## 1 Introduction
As a way of example, OEM manufacturers can build their products based on a single chip (comprising wireless communications and processing capabilities) [22], or separate microcontroller and radio (connected by SPI or UART) [23]. Furthermore, applications may be developed on \"bare metal\" (which makes them very hardware-specific), or using one of the available OSs (e.g., Contiki [24], RIOT [25], FreeRTOS [26]). Another important component is the network. For instance, despite the inclusion of security mechanisms in all of the referred standards, there are known attacks on WirelessHART, ZigBeePRO, ISA100.11a, and WIA-PA [27, 28, 29, 30]. Additionally, some of these technologies, namely WirelessHART, ZigBeePRO, and WIA-PA, are not immune to interference from equipment complying with other standards, such as IEEE 802.11, when operating in the ISM 2.4 Ghz frequency band. Such problems may lead to early sensor node energy depletion, and subsequent replacement, increasing the costs of network operation. Because of this, post-deployment tools are needed in order to adequately monitor IWSNs, thus contributing to the global system reliability. In the last decade, a wide range of WSN post-deployment tools [31] were developed. Some of them can improve the reliability of WSN by detecting network, firmware, and/or hardware problems. These tools help developers in both deployment and post-deployment environments by making several firmware- and hardware-related metrics accessible, and by detecting problems, using, for instance, sniffers or sink nodes. However, despite the effort to build such tools, most of them were designed for specific applications, require specific or dedicated hardware, consume non-negligible amounts of energy, do not implement security mechanisms, are complex to configure and/or to use, and do not allow the centralized management of multiple industrial standards like ZigBeePRO, WirelessHART, ISA100.11a, and WIA-PA. In this context, the contributions of this paper are the following: (i) a survey of ISWN standards (for process-automation) and their features per OSI layer; (ii) an overview of the reports and metrics made available by each of the IWSN standards; (iii) a survey of the main techniques for WSN monitoring at network, firmware, and hardware levels; (iv) a proposal for an industrial IoT monitoring architecture that builds on IEEE 802.15.4-based industrial standards (WirelessHART, ISA100.11a, ZigBeePRO and WIA-PA) to provide management functionality; and (v) a proof-of-concept implementation of the proposed architecture. It should be noted that the proposed architecture does not increase the cost of node manufacturing, has negligible impact on the main sensor node application, hardware components, and network bandwidth and, last but not least, does not significantly increase energy consumption. The remainder of this paper is organized as follows. Section 2 details the main industrial IoT technologies, and provides a revision of applicable management protocols. In Section 3, representative diagnostic tools for collecting hardware, firmware and network metrics are described. Section 4 presents the proposed architecture in detail and, at the same time, explains how technologies, approaches, and protocols can be used to implement it. Section 5 presents a proof-of-concept implementation in a testbed using the WirelessHART standard, with the aim of assessing the architecture's impact in terms of energy consumption, application latency, RAM and flash utilization, and network traffic. Section 6 compares the proposed architecture with related work in this domain. Lastly, Section 7 presents the conclusions and guidelines for future work.