The rapid expansion of Non-Terrestrial Networks for global IoT connectivity faces key challenges related to synchronization, latency, and energy efficiency under orbit-dependent satellite coverage. LoRaWAN Class B offers a potential solution by enabling deterministic downlink scheduling. However, its real-world performance remains largely unexplored, particularly regarding timing accuracy and energy consumption. This paper presents a comprehensive experimental evaluation of Class B synchronization accuracy and power consumption using a real testbed. Results show that absolute synchronization errors grow from 1.5 ms to 11.5 ms, while relative errors remain below 0.02%. Worst-case cumulative drift stays within the 30 ms reception window, reaching 23.6 ms. Current measurements indicate that idle consumption decreases from 16.80 mA to 6.40 mA, with Sleep mode reducing overall draw by approximately 62%. These findings provide an empirical characterization of Class B timing precision and energy efficiency, supporting the design of future hybrid terrestrial–Non-Terrestrial Networks architectures.

Smart solutions increasingly involve the use of sensor data to represent the physical world in the digital world and apply intelligence to such representation. The main approach is a vertical end-to-end solution from sensors to intelligence and back to actuators. Recently, a new holistic approach, the so-called Digital Twin, has emerged. This goes beyond traditional smart solutions by replicating, with high-fidelity cross-domain aspects, a physical object into the digital world. The key differentiation is the inclusion of semantics information in the digital replica in a form of knowledge graph. Further, analytics continuously enrich Digital Twin’s information with predictions and insights. In this article, we adopt the Digital Twin approach for the creation of a digital replica of Espinardo’s campus at the University of Murcia (Spain). The starting point is the existing sensor network deployment and the infrastructure under development of Fog–Edge–Cloud computing based on a 5G private network. The smart campus Digital Twin is formed by the Digital Twins of 23 buildings for which different sets of data features have been thoroughly selected. We implement the concept of Digital Twin by merging sensor data with external open data sources, analytics models implemented, and information processed by these analytics. We report our experience showing the issues encountered handling the data and producing various analytics models for predicting energy consumption, building occupancy, room usage, solar energy, and anomaly detection. From our experience, we highlight some lessons learned and directions toward the full operational smart campus Digital Twin.

The recent proliferation of the Industrial Internet of Things has revealed the potential of Low-Power Wide-Area Networks as a complementary solution to cellular technologies. In this context, the LoRaWAN standard has already been consolidated as one of the most extended technologies in academia and industry for lightweight machine-type communications under negligible energy and cost. As LoRaWAN’s Aloha-like nature is known to hinder its reliability, especially under high-traffic and large-scale deployments, numerous time-slotted approaches have been presented as a means to schedule LoRa transmissions accordingly. However, the online allocation of resources based on application constraints has received scant attention in the literature, despite having proved to be significant in real-world deployments. To shed light on this question, this paper proposes a multi-agent approach to efficient resource allocation in multi-SF LoRaWAN networks, addressing architecture design, logic implementation and scalability-oriented evaluation. The integration of agents in the system resulted in network-size improvements of up to 21.6% and 66.7% (for nearby or scatter node distributions within the gateway, respectively). The work provides a set of learned lessons regarding slot-length computation and end-node allocation strategies enabling large-scale collision-free channel access in LoRaWAN networks.

In the building context, there is a growing requirement for numerous data models and ontologies to coexist as a means to cover different perspectives and communities. While there are some well-known efforts, such as the Brick schema, to create an overall usable ontology, interlinking available ontologies and data models is still a challenge that can provide significant benefits towards interoperability of Building Information Models. To shed light on this matter, we provide a review of some of the most important ontologies in the building context, which we then match against Brick as a means to provide an interlinked data model. For finding matches, we propose TrioNet, an interactive ontology matcher utilizing weak supervision and active learning, which we compare in terms of precision and recall with two well-known state-of-the-art ontology matchers: AgreementMakerLight (AML) and LogMap. TrioNet outperforms them in finding more verified matches with only a few domain expert annotations, making it an ideal tool for the creation of interlinked data models to improve interoperability. With this paper, we contribute the following datasets: (i) the overall Brick data model interlinked to five other ontologies; (ii) the discovered pairwise ontology alignments; and (iii) the manually-annotated matches used for evaluation.

This paper addresses new challenges arising from the emergence of Bluetooth mesh and its rapid adoption in Internet of Things (IoT) and Industrial IoT. One of the main problems associated with Bluetooth mesh is the power consumption of the mesh nodes, since the network needs to be scanned constantly to receive and relay messages. In order to reduce the energy consumption in the nodes where possible, the friendship mechanism is provided as a solution by the Bluetooth mesh specification. The friendship mechanism enables Low Power Nodes (LPNs) to spend most of their lifetime in sleep mode without losing the messages addressed to them. For this purpose, a node that is constantly in scan mode, called friend node (FN), stores these messages, sending them on request. This mechanism works with a stop-and-wait protocol, resulting in inefficient channel utilisation. However, to the best of our knowledge, there are no proposals for the improvement of this mechanism, likely due to its novelty. This paper studies different approaches for the improvement of the friendship mechanism: improving the Bearer Layer, improving time synchronisation and improving advertising channel utilisation. The results of this study reveal that each of the proposals presents a limitation that makes its final implementation unfeasible, and thus the challenge arises of developing a proposal for its optimisation. Accordingly, this work presents a proposal to improve the friendship mechanism with Burst Transmissions and Listen Before Transmit (BTLBT), which has been evaluated and validated in real hardware platforms. The results obtained for 4 LPNs show a reduction in the time required to receive the FN messages, as well as a 66.65% reduction in the time required to scan for each message. Finally, a consumption study is presented, where the results show that our proposal achieves a 19.81% improvement in lifetime compared to the standard friendship mechanism.

While the Internet of Things continues to grow, the LoRaWAN standard is generating special interest due to its open-source nature, ultralow-power consumption and long-range connectivity. Recent works have explored the challenges of implementing LoRaWAN, with scalability being considered one of the major bottlenecks imposed by its Aloha-based medium access control (MAC) layer. Despite much on-going research on LoRaWAN scheduling aimed at alleviating this concern, experimental approaches are rarely found in the literature. In this work, we describe the steps taken and the technical issues overcome to move from a low-overhead synchronization and scheduling concept to its real-world implementation on top of LoRaWAN Class A. Accordingly, an end-to-end architecture was designed and deployed on top of STM32L0 MCUs, which communicate with a central entity responsible for providing synchronization metrics and allocating transmission slots on demand. The clock drift of devices was measured in a temperature-controlled chamber, which served as a basis to define slot lengths in the network. As a result, an operational end-to-end system was implemented and evaluated for different setup scenarios, with 10-ms accuracy being achieved. Our experimental results show significant improvements in packet delivery ratios with respect to Aloha-based setups, especially under high network loads (up to 29% for SF12), thereby demonstrating the feasibility of the presented approach.

This paper proposes an architecture for Wireless Sensor and Actuator Networks (WSAN) using the new standard Bluetooth Low Energy (BLE). This architecture can be used as reference for the deployment of real and flexible monitoring platforms based on Internet of Things (IoT) scenarios such as smart homes, making a multitude of tasks easier to the user. A general overview of the architecture is presented as well as a specific description of its different layers.

This paper shows the evaluation results with the new mesh topology for the Bluetooth Low Energy standard in IoT scenarios where users send values from different monitorization parameters. In this experimentation we have discovered as the user collaboration can increase the benefits of this topology. It is possible to expand the coverage area without adding new BLE nodes making use of the smart devices of users.

Abstract ZigBee is the primary standard solution for wireless sensor networks, implementing the Ad hoc On‐Demand Distance Vector (AODV) protocol in the network layer and supported by the standard IEEE 802.15.4. This study is focused on mesh topologies and the critical problems encountered when AODV is executed in conjunction with the Carrier Sense Multiple Access with Collision Avoidance protocol. These problems are mainly related to the packet overhead required to carry out route creation. To perform preliminary experiments to be able to implement AODV in a real network, a new metric is proposed herein. This metric uses fuzzy logic to help in the decision‐making process. The objective of the fuzzy routine is to determine, during the route‐discovery process, the best node to forward request/reply packets, with the aim of reducing packet overhead and energy consumption. Moreover, minor changes are also added to the discovery procedure of AODV to improve the performance of the route‐creation process. This intelligent version of AODV has provided promising experimental results, greatly reducing the number of packets required, with the consequent energy saving while selecting the best nodes to be part of the routes.

We consider reliable communications in Body Area Networks (BAN), where a set of nodes placed on human body are connected using wireless links. In order to keep the Specific Absorption Rate (SAR) as low as possible for health safety reasons, these networks operate in low transmit power regime, which however, is known to be error prone. It has been observed that the fluctuations of the Received Signal Strength (RSS) at the nodes of a BAN on a moving person show certain regularities and that the magnitude of these fluctuations are significant (5 - 20 dB). In this paper, we present BANMAC, a MAC protocol that monitors and predicts the channel fluctuations and schedules transmissions opportunistically when the RSS is likely to be higher. The MAC protocol is capable of providing differentiated service and resolves co-channel interference in the event of multiple co-located BANs in a vicinity. We report the design and implementation details of BANMAC integrated with the IEEE 802.15.4 protocol stack. We present experimental data which show that the packet loss rate (PLR) of BANMAC is significantly lower as compared to that of the IEEE 802.15.4 MAC. For comparable PLR, the power consumption of BANMAC is also significantly lower than that of the IEEE~802.15.4. For co-located networks, the convergence time to find a conflict-free channel allocation was approximately 1 s for the centralized coordination mechanism and was approximately 4 s for the distributed coordination mechanism.

Recent advances in communication networks have spurred interest on the definition of efficient self-configuration protocols. Such mechanisms are particularly of interest on the rapid deployment of wireless sensor networks whose nodes are characterized by their low computational and energy resources according to the green networking principles. In this paper, we introduce an adaptable fuzzy-logic assisted configuration mechanism for ZigBee networks; one of the most promising standards in the area of wireless sensor networks. Our results show that the use of fuzzy-logic principles can significantly improve the operation of tree-based routing mechanisms by reducing the set-up network time and the number of router nodes in the network, thus allowing a reduction in the energy consumed by nodes.

ZigBee in conjunction with IEEE 802.15.4 is considered the de facto standard for WSNs. The routing protocol for ZigBee mesh networks is AODV, an on-demand routing protocol which has been extensively used. However, it presents critical problems when it is used in large dense networks, mainly related to the high number of messages necessary to perform routing tasks, which causes a very high overhead. The high number of packet collisions, data loss, and its implicit energy expenditure, makes AODV unsuitable for certain applications that require efficient, fast and reliable communications. This study proposes the use of a novel fuzzy-logic-based metric to be used in the decision making process of AODV. This metric evaluates important node features during route creation and selects, hop by hop, the best option in order to obtain energy and delay efficient routes. The experiments with the improved AODV, AODV-FL show a reduction in the communication delay, number of packets and overhead, improving route efficiency and reducing packet overload.

The deployment of large-scale wireless sensor networks presents major challenges whose solution requires the design and development of robust and time-efficient protocols. In this work, we focus on the design of an efficient and robust protocol aiming to rapidly configure highly populated networks. Our main effort goes towards the definition of a fast collision resolution protocol for conveying the control packets for configuring the network. Through extensive simulation work we show that the proposed mechanism is capable of quickly resolving the conflicts arising during the set-up phase.

A large number of studies have been conducted to evaluate the benefits of using layered video coding schemes as a means to improve the robustness of video communications systems. In this article, we study a frame-aware layering scheme for the transport of DCT-based video over packet switched networks. Under this scheme, the relevance of the different elements of the video sequence is taken into account in order to compose the encoded video sequence. We conduct a detailed study over a large set of video streams encoded using the MPEG-2 video standard. Our results show that it is possible to reduce the video traffic while maintaining an acceptable video quality.

We introduce a set of control mechanisms at different levels of the protocol architecture to be used in MPEG-2-based video communications systems using ATM networks as their underlying transmission mechanism. Our results show the effectiveness of using a structured set of control mechanisms to overcome for the loss of cells carrying VBR video streams.

We propose the implementation of a MPEG encoder developed by the University of California at Berkeley on a multicomputer system. Since this application is in real time, we present a mapping of the video sequence between the EPs of the architecture, where the communication between EPs is minimized. We also propose the necessary load/store process with a simple mechanism input/output, where the global distribution process latency is compensated. Idonety of the topology of the system is analyzed, together with the most adequate commutation technique for the interconnection network. Finally the incidence of the frame format on the system communication performance is analyzed.