The use of a suitable propagation model for coverage prediction is key during the planning and dimensioning process of a digital terrestrial television (DTT) system. This study optimises one of the most detailed models for this purpose, i.e. Recommendation ITU‐R.P.1812‐4, with the aim of improving its accuracy in propagation path loss prediction for DTT systems in outdoor environments of Caracas city, Venezuela. For model adjustment, it is used the bioinspired technique particle swarm optimisation (PSO) and received signal level measurements performed in DTT systems in Caracas city under fixed reception conditions. The results, quantitatively analysed by RMS error and grey relation grade and mean absolute percentage error, shows a significant increase of the accuracy of optimised model in comparison with the original version and even with others propagation models.

In the present study, rainfall rate statistics for radio propagation applications collected during 1‐year measurement with a 1‐min integration time in three locations of Venezuela are presented and analyzed for the first time in the country. Specifically, the statistics of the worst‐month (WM) are assessed and compared with the Recommendation ITU‐R P.841‐7 prediction model. The results indicate that the model does not accurately predict the statistics of the WM in the country. Also, the performance of Recommendation ITU‐R P.837‐7 (Annex 1 and Annex 2) in estimating the rain rate for a 1‐min integration time at the three locations is examined, with the ITU‐R P.837‐7 Annex 1 exhibiting the best performance and providing results that encourage its use in the prediction of complementary cumulative distributions of rain rate in the country.

The rapid expansion of the IoT has led to increasing concerns about security, particularly in the early stages of communication where many IoT application-layer protocols, such as CoAP and MQTT, lack native support for secure key exchange. This absence exposes IoT systems to critical vulnerabilities, including dictionary attacks, session hijacking, and MitM threats, especially in resource-constrained environments. To address this challenge, this paper proposes the integration of OWL, a password-authenticated key exchange (PAKE) protocol, into existing IoT communication frameworks. OWL introduces a lightweight and secure mechanism for establishing high-entropy session keys from low-entropy credentials, without reliance on complex certificate infrastructures. Its one-round exchange model and resistance to both passive and active attacks make it particularly well-suited for constrained devices and dynamic network topologies. The originality of the proposal lies in embedding OWL directly into protocols like CoAP, enabling secure session establishment as a native feature rather than as an auxiliary security layer. Experimental results and formal analysis indicate that OWL achieves reduced authentication latency and lower computational overhead, while enhancing scalability, resilience, and protocol performance. The proposed solution provides an innovative, practical, and efficient framework for securing IoT communications from the foundational protocol level.

Predicting precipitation rate and rainfall attenuation are key aspects in planning and dimensioning of wireless communications systems operating at frequencies above 10 GHz, such as satellite communication systems at Ku and Ka bands. In this paper, contour maps of rainfall rate and rain attenuation are developed for the first time in Venezuela, based on 1-min rain rate statistics obtained from measurements carried out in Venezuela over at least 30 years period with a higher integration time and using Rice-Holmberg model, refined Moupfouma-Martin model and Recommendation ITU-R P.837-7, for rain rate estimation and Recommendation ITU-R P.618-13, Ramachandran-Kumar model, Yeo-Lee-Ong model and Rakshit-Adhikari-Maitra model, for rain attenuation prediction in “Simon Bolivar” satellite links in Venezuela. The overall results of both types of maps represent a useful tool for preliminary planning of those links in the country, specifically, in Ku and Ka bands

El control de la temperatura de los alimentos mediante la utilización de un equipo de congelación criogénico se torna complicado cuando se emplean técnicas de control clásico tipo PID (Proporcional + Integral + Derivativo), debido al fuerte acoplamiento entre las variables y las no linealidades propias del sistema. Actualmente, en la mayoría de las plantas procesadoras de alimentos que utilizan túneles de congelación criogénico, el control es llevado a cabo por medio del ajuste manual de los valores de consigna o setpoint de los lazos de control de velocidad y temperatura del túnel de congelación, lo que trae como consecuencia desviaciones en la salida del proceso, derivadas principalmente de la diferencia de criterios existentes entre los operadores y de la velocidad de respuesta de estos últimos ante variaciones en las condiciones del proceso. En este trabajo se tratan separadamente los lazos de control de velocidad y temperatura, se reconfiguran y entonan los lazos existentes, para luego desarrollar un controlador difuso tipo Takagi-Sugeno que permite ajustar el valor de consigna de la temperatura del túnel de congelación en función al producto y las condiciones de entrada del alimento al proceso. El comportamiento del sistema se comprueba mediante la simulación del mismo, verificándose que se mantiene la temperatura del producto en -18 °C, pese a que fue sometido a cambios en la masa de producto a enfriar (de 200 kg a 220 kg) y en el flujo másico del producto (de 650 kg/h a 700 kg/h).

Los sistemas UWB (ultra-wide band) transmiten señales a baja potencia a través de canales de comunicaciones que operan en entornos cerrados y en distancias cortas, lo que origina múltiples trayectorias de propagación. Además, el ruido que afecta a estos canales se puede caracterizar mediante el uso de modelos estadísticos de colas más pesadas que las exhibidas por la distribución gaussiana. En este artículo, se propone un enfoque robusto para la estimación de los parámetros de los canales UWB basado en la mediana ponderada. Específicamente, se desarrolla un algoritmo de búsqueda voraz que aprovecha la característica poco densa de la respuesta impulsiva del canal, donde las ganancias y los retardos de los canales relevantes se determinan aplicando la mediana ponderada sobre una versión escalada y desplazada de la señal recibida. El algoritmo propuesto se evalúa usando extensas simulaciones en las que el rendimiento del algoritmo propuesto supera el desempeño del algoritmo de búsqueda voraz tradicional para diferentes niveles de ruido impulsivo.