Simulation and experimental testbed for adaptive video streaming in ad hoc networks

[EN] This paper presents a performance evaluation of the scalable video streaming over mobile ad hoc networks. In particular, we focus on the rate-adaptive method for streaming scalable video (H.264/SVC). For effective adaptation a new cross-layer routing protocol is introduced. This protocol provides an efficient algorithm for available bandwidth estimation. With this information, the video source adjusts its bit rate during the video transmission according to the network state. We also propose a free simulation framework that supports evaluation studies for scalable video streaming. The simulation experiments performed in this study involve the transmission of SVC streams with Medium Grain Scalability (MGS) as well as temporal scalability over different network scenarios. The results reveal that the rate-adaptive strategy helps avoid or reduce the congestion in MANETs obtaining a better quality in the received videos. Additionally, an actual ad hoc network was implemented using embedded devices (Raspberry Pi) in order to assess the performance of the proposed adaptive transmission mechanism in a real environment. Additional experiments were carried out prior to the implementation with the aim of characterizing the wireless medium and packet loss profile. Finally, the proposed approach shows an important reduction in energy consumption, as the study revealed.This paper was performed with the support of the National Secretary of Higher Education, Science, Technology and Innovation (SENESCYT)–Ecuador Government (scholarship 195-2012) and the Multimedia Communications Group (COMM) belong to the Institute of Telecommunications and Multimedia Applications (iTEAM)-Universitat Politècnica de València.Gonzalez-Martinez, SR.; Castellanos Hernández, WE.; Guzmán Castillo, PF.; Arce Vila, P.; Guerri Cebollada, JC. (2016). Simulation and experimental testbed for adaptive video streaming in ad hoc networks. Ad Hoc Networks. 52:89-105. https://doi.org/10.1016/j.adhoc.2016.07.007S891055

Global disparities in surgeons’ workloads, academic engagement and rest periods: the on-calL shIft fOr geNEral SurgeonS (LIONESS) study

: The workload of general surgeons is multifaceted, encompassing not only surgical procedures but also a myriad of other responsibilities. From April to May 2023, we conducted a CHERRIES-compliant internet-based survey analyzing clinical practice, academic engagement, and post-on-call rest. The questionnaire featured six sections with 35 questions. Statistical analysis used Chi-square tests, ANOVA, and logistic regression (SPSS® v. 28). The survey received a total of 1.046 responses (65.4%). Over 78.0% of responders came from Europe, 65.1% came from a general surgery unit; 92.8% of European and 87.5% of North American respondents were involved in research, compared to 71.7% in Africa. Europe led in publishing research studies (6.6 ± 8.6 yearly). Teaching involvement was high in North America (100%) and Africa (91.7%). Surgeons reported an average of 6.7 ± 4.9 on-call shifts per month, with European and North American surgeons experiencing 6.5 ± 4.9 and 7.8 ± 4.1 on-calls monthly, respectively. African surgeons had the highest on-call frequency (8.7 ± 6.1). Post-on-call, only 35.1% of respondents received a day off. Europeans were most likely (40%) to have a day off, while African surgeons were least likely (6.7%). On the adjusted multivariable analysis HDI (Human Development Index) (aOR 1.993) hospital capacity > 400 beds (aOR 2.423), working in a specialty surgery unit (aOR 2.087), and making the on-call in-house (aOR 5.446), significantly predicted the likelihood of having a day off after an on-call shift. Our study revealed critical insights into the disparities in workload, access to research, and professional opportunities for surgeons across different continents, underscored by the HDI

Simulation and testbed evaluation for optimizing energy consumption in ad hoc networks based on OLSR protocol

This paper presents a proposal to optimize energy consumption in ad hoc networks based on the OLSR protocol. This approach focuses on the set up of routes with less congestion level and higher energy capacity. Therefore, in addition to the remaining energy of nodes, a new metric is introduced, the strategic value, which reports the importance of a specific node in the network based on the numbers of neighbors it has. In order to obtain valuable results, the evaluation was performed in a simulation environment (NS3) and on a real testbed. In that sense, an actual ad hoc network was implemented using embedded devices (Raspberry Pi). Results show a decrease in energy consumption, especially in zones with the highest device density, as well as an increase of the time of operation for nodes with higher amount of neighbors. Additionally, the performed evaluation shows a positive effect in the quality of traffic flows, avoiding route breakages and packet losses.Lisbo

Buffering technique for optimizing energy consumption in the transmission of multimedia traffic in Ad-Hoc networks

El significativo crecimiento en el uso de dispositivos móviles ha generado un gran interés en la investigación de nuevos escenarios de comunicación, por ejemplo el despliegue de redes oportunistas basadas en dispositivos de usuario como smartphones [1]. En ese sentido un modo de comunicación Ad-Hoc representa una potencial solución para este tipo de escenarios. Sin embargo uno de los principales desafíos que enfrenta el despliegue de redes Ad-Hoc, es la limitada capacidad de energía de los dispositivos debido al uso de baterías.Energy constraints on wireless nodes represent a current field of research. Such restrictions are particularly significant because of the great amount of features and applications currently available on devices, which contribute to dramatically increase energy consumption. However, when transmitting delay-sensitive data, such as multimedia streaming, a balance between energy optimization and quality of service is required. In this sense, there are many works that address this issue from different layers of network architecture separately; however, a more efficient solution could be achieved by combining the management capabilities of the different layers and the joint use of such information, which is called a cross-layer mechanism. Moreover, despite the fact that the IEEE 802.11 standard defines an energy management mechanism at MAC level, it is envisaged only for structured networks, leaving just general guidelines for other kind of networks, such as Ad-Hoc networks. Therefore, as a first step towards the design of a cross-layer scheme, this paper analyzes the flaws of IEEE 802.11 standard as regards the infrastructureless mode and proposes an optimization mechanism for energy management in Ad-Hoc networks. The proposed approach is based on a buffering mechanism, which is able to increase power-saving periods of time in Ad-Hoc nodes. Simulations using NS3 indicate that it is possible to obtain higher levels of residual energy at the end of a transmission using the proposed schem

Evaluation and comparison of algorithms for the automatic detection of seismic events

La detección temprana de eventos sísmicos permite reducir daños materiales, el número de personas afectadas e incluso salvar vidas. En particular, la actividad sísmica en Ecuador es alta, dado que se encuentra en el denominado Cinturón de Fuego del Pacífico. En tal contexto, el presente artículo tiene como objetivo comparar algoritmos para la detección automática de eventos sísmicos. Dicha comparación se realiza con respecto a la funcionalidad y configuración de los parámetros requeridos para cada algoritmo. Además, la implementación se lleva a cabo sobre una plataforma computacional tipo SBC (Single Board Computer) con la finalidad de obtener una herramienta portable, escalable, económica y de bajo costo computacional. Los métodos comparados son: Classic STA/LTA, Recursive STA/LTA, Delayed STA/LTA, Zdetector, Baer and Kradolfer picker y AR-AIC (Autoregressive-Akaike-Information-Criterionpicker). Para la evaluación y comparación se desarrollan múltiples experimentos empleando registros sísmicos reales proporcionados por la Red Sísmica del Austro (RSA), disponibles como fuente de entrada a los algoritmos. Como resultado se obtiene que el algoritmo Classic STA/LTA presenta el mejor rendimiento, ya que del total de eventos reales (58), solo un evento no fue detectado. Además, se consiguen 6 falsos negativos, logrando un 98,2% de precisión. Cabe recalcar que el software utilizado para la comparación de algoritmos de detección de eventos sísmicos está disponible de forma libre.Early seismic events detection might reduce the number of people affected and save lives. In particular, the seismic activity in Ecuador is high, given its location along the zone named the Pacific Belt of Fire. In this context, this paper presents a solution to compare algorithms for detecting seismic events. This comparison was performed both concerning the functionality and the configuration of the parameters required for each algorithm. This solution was implemented on an SBC platform (Single Board Computer) to obtain a portable, scalable, economical, and low-cost computational tool. The methods compared were: Classic STA/LTA, Recursive STA/LTA, Delayed STA/LTA, Z Detector, Baer and Kradolfer picker, and AR-AIC (Autoregressive-Akaike-Information-Criterion-picker). For the evaluation and comparison, multiple experiments were carried out using real data provided by the Regional Seismological Network (RSA). In particular, such registers were used as input data to the seismic algorithms. Results revealed that the algorithm with the best performance was the Classic STA/LTA, since from the total number of real events (58), only one was not detected. In addition, 6 false negatives were obtained, achieving 98,2% of precision. Finally, the software used for the comparison of the algorithms has been released for free usage, which represents another contribution of this work in the context of seismic analysis

A Low-Cost IoT Architecture Based on LPWAN and MQTT for Monitoring Water Resources in Andean Wetland

This paper describes the development of a monitoring system for water sources in the Tres Lagunas Andean high-altitude wetlands ecosystem (Ecuador), utilizing LoRa technology. The system design primarily involves an ATmega1284p microcontroller, LoRa transceiver, and physicochemical sensors. Data collected from the study site are transmitted to the server and then forwarded to the Node-RED platform using the MQTT protocol. Additionally, a graphical user interface has been created to facilitate the analysis of the data related to temperature, dissolved oxygen (DO), oxidation–reduction potential (ORP), and hydrogen potential (pH). Additionally, an analysis of LoRa parameters was conducted for the rural area and the wetlands, where SF9 and SF10 show a packet reception rate higher than 97%. This is complemented by an energy assessment in relation to the LoRa interface, obtaining proper operation of the node. This scheme arises from the work developed in González et al. (Smart Cities: 5th Ibero-American Congress, ICSC-CITIES 2022, Cuenca, Ecuador, November 28–30, 2022, Revised Selected Papers. Springer, 2023), and due to the satisfactory results, the data collection is further explored, and its behavior is detailed. In this sense, a comparison of the prototype’s measurements with a commercial equipment was performed, the experiments indicate that the temperature and pH sensors provide comparable data with the commercial equipment. The primary achievement of this study is the development of an affordable, portable, and open-source prototype aimed at transmitting hydrological information from Andean high-altitude lakes using IoT technologies

Altruistic networks: where every node matters

Traditionally, wireless ad hoc networks have been used for emergency situations due to the feasibility of fast deployment and connectivity. However, multimedia services are much demanded nowadays and bandwidth and delay requirements of this kind of services are very restrictive. Offering real-time video services in wireless ad hoc networks is not an easy task because of the difficulty of guaranteeing certain quality in a shared medium. In this kind of network, nodes should be ready to route and forward data packets coming from other nodes. The cooperation of every node is essential for the proper operation of the network because there are many factors that may cause video quality degradation, from radio interferences to node mobility, which causes link breakages until a new route is calculated, producing annoying video interruptions to the receiver. The variability in network capacity and link quality, together with the dynamic network topology, has clearly influenced emerging wireless mesh networks, which tend to maintain a static backbone in order to provide sufficient Quality of Service. Moreover, since wireless propagation nature allows any node to overhear any neighbor transmission, the way opportunistic and cooperative routing protocols take advantage of the broadcast nature of wireless medium can be adopted for new routing proposals. In this sense, this chapter proposes and describes a new cross-layer mechanism for recovering lost packets by means of caching overheard packets in neighbor nodes and retransmit them to destination. Additionally, a video-aware cache is implemented in order to recover full frames and prioritize more significant frames. On the other hand, energy consumption is critical in mobile nodes because they may rely on battery power, and the whole network connectivity may be affected if some of the routing nodes run out of battery eventually. Thus, energy consumption is also taken into account in the recovering algorithm design to ensure longer network connectivity life. Finally, results show the improvement in reception, increasing the throughput as well as video quality, and reduce large video interruptions considerably. Moreover, by being aware of nodes energy consumption, the proposed algorithm is able to maintain network lifetime longer

Energy optimization for video monitoring system in agricultural areas using single board computer nodes and wireless ad hoc networks

This paper presents the design and implementation of a set of prototype nodes that have the ability to establish communication links in ad hoc mode. The prototypes were implemented using low cost, single board computers with embedded Linux (Raspberry Pi devices). The implemented stations aim to set a wireless sensor network for the capture of variables applied to agricultural environments. In particular, a camera module has been included on a node for remote video monitoring of farming zones, and also a GPS module for the capture of geolocation information. Nodes can be accessed remotely by means of the developed web interface. The routing process between nodes is carried out using the S-OLSR mechanism (OLSR modification) in order to set up routes taking into account the energy limitations as well as the location of each device in the topology. Results describe the contribution of this work to the design of monitoring applications on agricultural zones by means of the deployment of autonomous ad hoc nodes and energy routing optimization.Bucaramang

Performance analysis of OLSR, DSDV and AODV protocols in a MANET Network

Este artículo presenta una propuesta de análisis y comparación entre los protocolos de enrutamiento proactivo OLSR y DSDV, y reactivo AODV en una red MANET. Se definen dos escenarios: el primero representando un equipo de fútbol atacando y el segundo defendiendo. Se varía el área de movimiento de los nodos para simular cada escenario. Para ello, se realiza una investigación sobre los problemas que presentan estos algoritmos de enrutamiento para redes Ad Hoc en diferentes ámbitos. De esta forma, obtener un panorama de las estrategias y soluciones que existen actualmente. A partir de la información recopilada, se propone realizar una simulación utilizando NS3, para obtener resultados que se asemejen a la realidad. La comparación se realiza a base de las métricas de throughput, PDR y Delay. En cada simulación, la velocidad de los nodos y la posición inicial se ajustan según el comportamiento de un jugador de fútbol real. Los nodos se mueven en una trayectoria aleatoria dentro del área específica, y uno de éstos envía datos a un nodo fijo situado en el borde del campo. El tráfico transmitido está caracterizado para simular datos biométricos realistas. A partir de los resultados, se concluye que AODV y DSDV tienen un mejor rendimiento que OLSR y el intervalo óptimo de transmisión es de 20 segundos. Además, con una potencia de transmisión de 10 dBm se garantiza el 100% del throughput en el receptor.This paper presents an analysis and comparison between the proactive routing protocols OLSR and DSDV and the reactive routing protocol AODV in a MANET network. Two scenarios were defined, the first one representing a soccer team attacking and the second one defending. To simulate each scenario the area of movement of the nodes (players) was varied. For this purpose, an investigation was carried out on the problems presented by these routing algorithms for Ad Hoc networks in different environments. In this way, an overview of the strategies and solutions that currently exist is obtained. Based on the information gathered, it is proposed to perform a simulation using NS3 in order to obtain results that resemble reality. The comparison is made based on throughput, PDR and Delay metrics. In each simulation, parameters such as node velocity and initial position are adjusted according to the behaviour of a real soccer player. The nodes move in a random trajectory within the specific area and one of them sends data to a fixed server node located at the edge of the area where the nodes move, simulating the bench where the receiver is located. The transmitted traffic is characterized to simulate realistic biometric data. From the results, it is concluded that AODV and DSDV have better performance than OLSR and the optimum transmission interval is 20 seconds. In addition, with a transmit power of 10 dBm, 100% throughput is guaranteed at the receiver

Evaluación y comparación de códecs de video para el despliegue de un sistema de comunicación resiliente

En escenarios de emergencia usualmente es difícil contar con una infraestructura de red, especialmente en lugares remotos o geográficamente complicados por el difícil acceso. Sin embargo, es necesario disponer de herramientas para comunicarse o realizar una valoración de la situación. En este sentido, las redes ad hoc surgen como una opción para solucionar esta problemática. En el presente artículo se propone el desarrollo de un sistema de comunicación de emergencia para la transmisión de tráfico multimedia en un escenario real, entre los diferentes pisos de un edificio. Para tal objetivo, se realizaron múltiples experimentos para determinar los valores de métricas fundamentales (v.g. packet loss, delay y throughput) para la transmisión de audio y video en tiempo real. En concreto, se desarrollaron herramientas de código abierto con capacidad de extraer las métricas requeridas y comparar de forma objetiva la calidad del video empleando mecanismos de codificación actuales (v.g. VP8, VP9, H.264, H.265). Los resultados obtenidos muestran que VP8 es el códec más adecuado para el escenario propuesto. Además, se desarrolló una herramienta de videoconferencia con capacidad de adaptar las características del video (v.g. bitrate) acorde a las condiciones de la red.In emergency scenarios, it is usually difficult to rely on network infrastructure, especially in remote or geographically difficult-to-access locations. However, it is necessary to have tools to communicate or assess the situation. Therefore, ad hoc networks emerge as an option to solve this problem. This paper proposes the development of an emergency communication system for the transmission of multimedia traffic in a real scenario, between the different floors of a building. For this purpose, multiple experiments were carried out to determine the values of fundamental metrics (e.g., packet loss, delay, and throughput) for real-time audio and video transmission. Specifically, open-source tools were developed with the ability to extract the required metrics and objectively compare video quality using current encoding mechanisms (e.g., VP8, VP9, H.264, H.265). The results obtained show that VP8 is the most suitable codec for the proposed scenario. In addition, a videoconferencing tool was developed with the ability to adapt the video characteristics (e.g., bitrate) according to the network conditions