Wireless sensor networks (WSNs) have been adopted in many fields of application, such as industrial, civil, smart cities, health, and the surveillance domain, to name a few. Fateway and sensor nodes conform to WSN, and each node integrates processor, communication, sensor, and power supply modules, sending and receiving information of a covered area across a propagation medium. Given the increasing complexity of a WSN system, and in an effort to understand, comprehend and analyze an entire WSN, different metrics are used to characterize the performance of the network. To reduce the complexity of the WSN architecture, different approaches and techniques are implemented to capture (model) the properties and behavior of particular aspects of the system. Based on these WSN models, many research works propose solutions to the problem of abstracting and exporting network functionalities and capabilities to the final user. Modeling an entire WSN is a difficult task for researchers since they must consider all of the constraints that affect network metrics, devices and system administration, holistically, and the models developed in different research works are currently focused only on a specific network layer (physical, link, or transport layer), making the estimation of the WSN behavior a very difficult task. In this context, we present a systematic and comprehensive review focused on identifying the existing WSN models, classified into three main areas (node, network, and system-level) and their corresponding challenges. This review summarizes and analyzes the available literature, which allows for the general understanding of WSN modeling in a holistic view, using a proposed taxonomy and consolidating the research trends and open challenges in the area.

Low Power Wide Area Networks (LPWAN) have emerged as an attractive Internet of Things (IoT) communication option. When deploying a communication network to support IoT applications, large coverage and low power consumption are critical requirements. Despite the fact that existing LPWAN technology solutions promote IoT requirements such as long communication range, energy efficiency, scalability, and low cost, network performance is a major concern. With so many LPWAN technologies available, there is a growing interest in evaluating them. Recent works have presented various comparison studies of LPWAN technologies, but the majority of them have approached the analysis from the standpoint of comparing technical specifications rather than presenting measurement results obtained from network deployment scenarios. We argue that by proposing a comparative evaluation from an experimental standpoint, the comparison discussion is deepened. This paper proposes an experimental comparative evaluation of LoRaWAN and SigFox, two emerging LPWAN technologies operating in sub-GHz Industrial, Scientific, and Medical (ISM) frequency bands, based on coverage and energy-efficiency test performance. The experimental evaluation was proposed first by identifying coverage and energy-efficiency as the two most important design goals for LPWAN applications. Second, by proposing test performance to evaluate those goals, where extensive measurements were made in network deployments, and finally, by highlighting the main performance findings in both networks for comparison purposes. The results show that in a fair-weather test, LoRaWAN outperformed SigFox in terms of coverage, achieving a higher packet delivery rate (PDR $\gtrsim ~80$ %), and having higher radio strength signal (RSSI $\gtrsim $ -110 dBm). Sigfox, on the other hand, shows better energy efficiency with 20% more sent messages under the same test conditions.

Atmospheric Water Generators (AWG) are a promising technology solution to the water scarcity in the world. However, their main drawback is the high power consumption. This paper presents the experimental optimization process of a Portable Atmospheric Water Generator (PAWG) prototype based on a thermometric cooler. This process was developed by an exhaustive search of the experimental solution space, which was generated by parametric sweeps of two parameters (i.e., control voltages in the PAWG), which are related to the power consumption of the PAWG and the physical variables involved in the water condensation process (i.e., the airflow and the temperature on the water condenser element). As a result, we found the existence of two optimal operation points under a constant value of relative humidity; one of them maximizes the amount of water generated, and the other one maximizes the system performance (i.e., the ratio between the generated water and consumed power in mL/Wh). The resulting Figures of Merit (FoMs) of the PAWG prototype were 0.33 mL/h of generated water and 0.22 mL/Wh for the system performance.

The design of a new broadband quasi Yagi-Uda antenna is presented. The antenna is composed of an electromagnetic band-gap (EBG)-truncated ground plane and a feeding network formed by a Marchand balun and a coupling network. The quasi Yagi-antenna was designed to work at a central frequency of 3.5 GHz using a 30-mil FR4 substrate. The simulated and measured results show a relative bandwidth better than 53%, a cross polarization lower than -19 dB in the main lobe, and a front-to-back ratio better than 12 dB in the entire bandwidth.

Decentralized desalination systems driven by renewable energy sources have surfaced as a feasible way to alleviate water scarcity in arid and rural areas. This bibliometric study aims to clarify the research trends, conceptual frameworks, and cooperative dynamics in the scientific literature on decentralized renewable-powered desalination techniques. Using a thorough search approach, 1354 papers were found. Duplicates, thematically unrelated works, and entries with poor information were removed using the PRISMA 2020 framework. A selected 832 relevant papers from a filtered dataset were chosen for in-depth analysis. Quantitative measures were obtained by means of Bibliometrix; network visualisation was obtained by means of VOSviewer (version 1.6.19) and covered co-authorship, keyword co-occurrence, and citation structures. Over the previous 20 years, the data show a steady rise in academic production, especially in the fields of environmental science, renewable energy engineering, and water treatment technologies. Author keyword co-occurrence mapping revealed strong theme clusters centred on solar stills, thermoelectric modules, reverse osmosis, and off-grid systems. Emphasizing current research paths and emerging subject borders, this paper clarifies the intellectual and social structure of the field. The outcomes are expected to help policy creation, cooperative projects, and strategic planning meant to hasten innovation in sustainable and decentralized water desalination.