The rapid adoption of Internet of Things (IoT) technologies and digital twins (DTs) is revolutionizing smart cities by facilitating improved real-time monitoring, simulation, and optimization of urban infrastructures. In data centers, digital twins offer virtual representations of physical infrastructure, enabling real-time monitoring, optimization of energy consumption, cooling efficacy, and resource utilization. This integration seeks to improve energy efficiency and sustainability in smart cities. In this context, edge computing is becoming essential solutions to mitigate latency, bandwidth, and privacy issues linked to centralized cloud system. A significant challenge in utilizing digital twins for edge-enabled data centers is attaining accurate time synchronization between the digital twin and its physical equivalent. Precise synchronization is crucial for real-time state representation, facilitating efficient monitoring, control, and optimization. The distributed characteristics of edge devices, varying network conditions, and constrained computational resources present considerable synchronization challenges. Factors such as clock drift, network jitter, and protocol constraints can result in temporal inconsistencies, compromising the reliability of digital twin applications. This paper offers an extensive examination of time synchronization issues in digital twins for edge-enabled data centers within smart city contexts. The study examines essential factors affecting synchronization accuracy and reliability, identifies significant bottlenecks, and suggests strategies to alleviate their impact. The results aid in the creation of effective synchronization mechanisms, facilitating the implementation of dependable digital twin systems.

The demand for enhanced flexibility in automation systems, dictated by initiatives as the Industry 4.0 in Europe or the Industrial Internet Consortium in the United States, can be satisfied inheriting solutions of the information technology (the so called IT-OT convergence). Other than communication and cloud technologies, virtualization will play a relevant role in the next future. The use of lightweight virtualization, e.g., in the form of containers for implementing the edge computing paradigm, is a promising tool to dynamically provide services depending on the actual production needs. However, requirements of industrial automation applications are different from those of office-like counterparts. For this reason, methodologies for evaluating obtainable performance are needed. In this work, an industrial-grade framework, the Siemens Industrial Edge, is considered. A reference testbed is setup to evaluate latencies when information is exchanged between two user applications. Experiments demonstrate that round trip time in the order of 10 ms is feasible, compatible with the requirements of both process control systems and supervision applications.

LPWAN, an acronym for Low Power Wide Area Network, addresses all the wireless communication solutions aiming at maximize the lifetime of battery powered end devices by means of high-sensitivity radios and sporadic data transactions. Among the different members of the LPWAN family, LoRaWAN is an emerging solution satisfying requirements of many Internet of Things (IoT) related applications. LoRa WAN supports both public and private deployments, operating in unlicensed frequency bands. Handling critical messages, e.g., originated after emergency events in industrial plants, is out of the original LoRaWAN scope. For this reason, the LoRa-REP replication scheme was proposed to increase reliability and to reduce latency of confirmation. In this work, obtainable performance are further improved allowing frame overlaps in time and frequency, exploiting LoRa virtual channels. In particular, Software Defined Radio paradigm is exploited for implementing a proof-of-concept to be used in real-world trials. The preliminary results, supported by simulations as well, are discusses, confirming the feasibility and effectiveness of the proposed approach.

Low Power Wide Area Networks (LPWANs) are wireless technologies well accepted in the Internet of Things (IoT) scenarios because they operate in both public and private infrastructure using unlicensed frequency bands. Differently from other wireless standards, the LPWAN target applications are low-rate, sporadic-transmission, low-energy systems. Surely, fast response time and high reliable communication are out of the original LPWAN scope. In this work, a first investigation about the use LoRaWAN (one the most diffused LPWAN protocols) for notification of emergency messages across industrial plants is reported. The opportunity of using recently proposed low-cost repeaters, and the creation of a clever replication pattern of radio messages are the keys of the proposed approach. The results of the preliminary analytical feasibility assessment are presented, confirming the possibility to increase success ratio of notification and respective confirmation in case of emergencies.

Recently, designers of the home automation framework are looking to the Internet of Things (IoT) model to make it easier to deploy devices capable of gathering data from various plants. This situation is pushing a further evolution: from the conventional building automation, where the logic is determined by the installer or by the customer, to a cognitive system, capable of learning from the customers' preferences what the best plant configuration would be. The aim of this research work is to identify issues related to the implementation of cognitive solutions during the renovation process of buildings. The paper proposes a cognitive framework to help the operation and management phases of buildings, by means of the digitalization of the supply chain of the construction industry, from the single building aspect to the entire construction cycle. The paper presents the design of smart building elements with integrated capability to generate a massive amount of data for monitoring the energy and maintenance status of renovated buildings. The IoT paradigm has been used to link the physical word of building elements with the cognitive layer. The proposed approach has been applied and validated into a real test case.

The LoRaWAN technology, an example of low power wide area network, is considered a possible IoT-derived solution for realizing private cellular (single-hop) communications in the industrial domain. However, despite LoRaWAN promises long range and dense environments with many obstacles (as the industrial ones), it may suffer from coverage issue. Additionally, the inverse relationship between data rates and range may be unacceptable for many industrial applications. In this article, an innovative LoRaWAN range extender (based on an enhanced LoRaWAN node) is described, and its integration in the infrastructure of industrial Internet of Things (IIoT)-enabled industrial wireless networks is presented. A frame relay strategy is suggested, thus avoiding to tradeoff the highest data rates against an increased sensitivity. The feasibility of the solution is formally verified and the features of the realized proof-of-concept prototype, based on commercially available hardware, are discussed. The experimental results, obtained with a purposely designed test bench, show the effectiveness of the proposed approach. In particular, the range extender is transparent for legacy LoRaWAN networks as confirmed by correct relaying of uplink and downlink for different types of LoRaWAN message.