Energy-Efficient UAVs Deployment for QoS-Guaranteed VoWiFi Service

This paper formulates a new problem for the optimal placement of Unmanned Aerial Vehicles (UAVs) geared towards wireless coverage provision for Voice over WiFi (VoWiFi) service to a set of ground users confined in an open area. Our objective function is constrained by coverage and by VoIP speech quality and minimizes the ratio between the number of UAVs deployed and energy efficiency in UAVs, hence providing the layout that requires fewer UAVs per hour of service. Solutions provide the number and position of UAVs to be deployed, and are found using well-known heuristic search methods such as genetic algorithms (used for the initial deployment of UAVs), or particle swarm optimization (used for the periodical update of the positions). We examine two communication services: (a) one bidirectional VoWiFi channel per user; (b) single broadcast VoWiFi channel for announcements. For these services, we study the results obtained for an increasing number of users confined in a small area of 100 m2 as well as in a large area of 10,000 m2. Results show that the drone turnover rate is related to both users’ sparsity and the number of users served by each UAV. For the unicast service, the ratio of UAVs per hour of service tends to increase with user sparsity and the power of radio communication represents 14–16% of the total UAV energy consumption depending on ground user density. In large areas, solutions tend to locate UAVs at higher altitudes seeking increased coverage, which increases energy consumption due to hovering. However, in the VoWiFi broadcast communication service, the traffic is scarce, and solutions are mostly constrained only by coverage. This results in fewer UAVs deployed, less total power consumption (between 20% and 75%), and less sensitivity to the number of served users.Junta de Andalucía Beca 2020/00000172Unión Europea FEDER 2014-202

On the Reusability of User Interface Declarative Models

The automatic generation of user interfaces based on declarative models achieves a significant reduction of the development effort. In this paper, we analyze the feasibility of using two well-known techniques such as XInclude and Packaging in the new context of reusing user-interface model specifications. After analyzing the suitability of each technique for UI reutilization and implementing both techniques in a real system, we show that both techniques are suited to be used within the context of today’s existing model-based user interfaces

Reflexiones sobre la Gestión de Riesgos en la Evaluación Telemática dentro del contexto de la E.T.S.I de la Universidad de Sevilla

Es imposible suprimir el riesgo en un examen telemático, como también lo es en un examen presencial. De forma natural, lo exámenes telemáticos abren un mayor número de oportunidades a quién desea sortear las normas establecidas. Todos los actores deben ser conscientes de estos riesgos. Los profesores se enfrentan al desafío de implementar mecanismos de evaluación confiables, los alumnos tendrán que aceptar nuevas formas de implementar y monitorizar esta evaluación y la Universidad deberá dotarse no sólo a sí misma y a los profesores, sino también a los alumnos con necesidades especiales con la necesaria infraestructura técnica y soporte normativo. Está por ver si el coste será razonable para todos. El objetivo de este trabajo es ofrecer al profesor, especialmente de ingeniería, una reflexión sobre los riesgos inherentes a la evaluación telemática y sugerir algunas soluciones que lo ayuden a tomar una decisión bien fundada para su asignatur

On the Detection Capabilities of Signature-Based Intrusion Detection Systems in the Context of Web Attacks

Signature-based Intrusion Detection Systems (SIDS) play a crucial role within the arsenal of security components of most organizations. They can find traces of known attacks in the network traffic or host events for which patterns or signatures have been pre-established. SIDS include standard packages of detection rulesets, but only those rules suited to the operational environment should be activated for optimal performance. However, some organizations might skip this tuning process and instead activate default off-the-shelf rulesets without understanding its implications and trade-offs. In this work, we help gain insight into the consequences of using predefined rulesets in the performance of SIDS. We experimentally explore the performance of three SIDS in the context of web attacks. In particular, we gauge the detection rate obtained with predefined subsets of rules for Snort, ModSecurity and Nemesida using seven attack datasets. We also determine the precision and rate of alert generated by each detector in a real-life case using a large trace from a public webserver. Results show that the maximum detection rate achieved by the SIDS under test is insufficient to protect systems effectively and is lower than expected for known attacks. Our results also indicate that the choice of predefined settings activated on each detector strongly influences its detection capability and false alarm rate. Snort and ModSecurity scored either a very poor detection rate (activating the less-sensitive predefined ruleset) or a very poor precision (activating the full ruleset). We also found that using various SIDS for a cooperative decision can improve the precision or the detection rate, but not both. Consequently, it is necessary to reflect upon the role of these open-source SIDS with default configurations as core elements for protection in the context of web attacks. Finally, we provide an efficient method for systematically determining which rules deactivate from a ruleset to significantly reduce the false alarm rate for a target operational environment. We tested our approach using Snort’s ruleset in our real-life trace, increasing the precision from 0.015 to 1 in less than 16 h of work. View Full-TextMinisterio de Ciencias e Innovación (MICINN)/AEI 10.13039/501100011033: PID2020-115199RB-I00FEDER/Junta de Andalucía-Consejería de Transformación Económica, Industria, Conocimiento y Universidades PYC20-RE-087-US

Energy efficiency and quality of service optimization for constant bit rate real-time applications in 802.11 networks

In this paper, we propose a quality of service (QoS)‐sensitive energy efficiency optimization mechanism for 802.11 networks on the basis of the dynamic and simultaneous adjustment of the content window (W) and retry attempts limit (r) of the media access control (MAC) sublayer. The use of both operational variables let us not only find the optimum operational point regarding energy efficiency but also attain a positive impact on the QoS, which improves the results obtained with current single‐variable optimization strategies. The model under consideration includes external noise and does not impose the saturation condition in stations and as such is well suited for real‐time industrial applications under noisy channels. Results obtained from simulation confirm the advantages of adjusting simultaneously W and r versus adjusting either one separately, obtaining a slight improvement in energy efficiency and resulting in less loss and delay at the MAC sublaye

Sistema telemático de citas para la docencia

This work is licensed under a Creative Commons 4.0 International License (CC BY-NC-ND 4.0)En este trabajo presentamos un sistema de gestión de citas diseñado por el Dpto. de Ingeniería Telemática de la Universidad de Sevilla para satisfacer las necesidades de profesores y alumnos. Este servicio puede ser utilizado para concertar tutorías, seguimientos de proyectos o revisiones de exámenes. Durante un año de operación del sistema hemos podido probar sus efectos positivos en el desempeño docente y el aprendizaje de los alumnos. A los alumnos, les permite solicitar una cita en un horario que a ellos les sea más conveniente y tener la certeza de que el profesor estará esperándoles (presencialmente, o telemáticamente). También les permite reducir el tiempo de espera en las revisiones de exámenes. El profesorado puede saber con antelación cuándo vendrán los alumnos y qué tema desean tratar y así tener preparada la reunión, gestionando el tiempo de forma más eficaz. Además, le permite establecer los horarios disponibles para citas de forma flexible de manera que se adecúe a su disponibilidad dinámicamente (p.ej., semanalmente). También permite evitar aglomeraciones en las revisiones de exámenes. Finalmente, el sistema genera numerosos indicadores con los que el profesor puede gestionar el proceso de tutorías e integrarlo en una estrategia de mejora continua

CO-CAC: A new approach to Call Admission Control for VoIP in 5G/WiFi UAV-based relay networks

Voice over IP (VoIP) requires a Call Admission Control (CAC) mechanism in WiFi networks to preserve VoIP packet flows from excessive network delay or packet loss. Ideally, this mechanism should be integrated with the operational scenario, guarantee the quality of service of active calls, and maximize the number of concurrent calls. This paper presents a novel CAC scheme for VoIP in the context of a WiFi access network deployed with Unmanned Aerial Vehicles (UAVs) that relay to a backhaul 5G network. Our system, named Codec-Optimization CAC (CO-CAC), is integrated into each drone. It intercepts VoIP call control messages and decides on the admission of every new call based on a prediction of the WiFi network’s congestion level and the minimum quality of service desired for VoIP calls. To maximize the number of concurrent calls, CO-CAC proactively optimizes the codec settings of active calls by exchanging signaling with VoIP users. We have simulated CO-CAC in a 50 m 50 m scenario with four UAVs providing VoIP service to up to 200 ground users with IEEE 802.11ac WiFi terminals. Our results show that without CAC, the number of calls that did not meet a minimum quality level during the simulation was 10% and 90%, for 50 and 200 users, respectively. However, when CO-CAC was in place, all calls achieved minimum quality for up to 90 users without rejecting any call. For 200 users, only 25% of call attempts were rejected by the admission control scheme. These results were narrowly worse when the ground users moved randomly in the scenario

How much training data is enough?. A case study for HTTP anomaly-based intrusion detection

Most anomaly-based intrusion detectors rely on models that learn from a training dataset whose quality is crucial in their performance. Albeit the properties of suitable datasets have been formulated, the influence of the dataset size on the performance of the anomaly-based detector has received scarce attention so far. In this work, we investigate the optimal size of a training dataset. This size should be large enough so that training data is representative of normal behavior, but after that point, collecting more data may result in unnecessary waste of time and computational resources, not to mention an increased risk of overtraining. In this spirit, we provide a method to find out when the amount of data collected at the production environment is representative of normal behavior in the context of a detector of HTTP URI attacks based on 1-grammar. Our approach is founded on a set of indicators related to the statistical properties of the data. These indicators are periodically calculated during data collection, producing time series that stabilize when more training data is not expected to translate to better system performance, which indicates that data collection can be stopped. We present a case study with real-life datasets collected at the University of Seville (Spain) and a public dataset from the University of Saskatchewan. The application of our method to these datasets showed that more than 42% of one of trace, and almost 20% of another were unnecessarily collected, thereby showing that our proposed method can be an efficient approach for collecting training data at the production environment