Generic sensor network architecture for wireless automation (GENSEN)

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Synchronous wearable wireless body sensor network composed of autonomous textile nodes

A novel, fully-autonomous, wearable, wireless sensor network is presented, where each flexible textile node performs cooperative synchronous acquisition and distributed event detection. Computationally efficient situational-awareness algorithms are implemented on the low-power microcontroller present on each flexible node. The detected events are wirelessly transmitted to a base station, directly, as well as forwarded by other on-body nodes. For each node, a dual-polarized textile patch antenna serves as a platform for the flexible electronic circuitry. Therefore, the system is particularly suitable for comfortable and unobtrusive integration into garments. In the meantime, polarization diversity can be exploited to improve the reliability and energy-efficiency of the wireless transmission. Extensive experiments in realistic conditions have demonstrated that this new autonomous, body-centric, textile-antenna, wireless sensor network is able to correctly detect different operating conditions of a firefighter during an intervention. By relying on four network nodes integrated into the protective garment, this functionality is implemented locally, on the body, and in real time. In addition, the received sensor data are reliably transferred to a central access point at the command post, for more detailed and more comprehensive real-time visualization. This information provides coordinators and commanders with situational awareness of the entire rescue operation. A statistical analysis of measured on-body node-to-node, as well as off-body person-to-person channels is included, confirming the reliability of the communication system

Standards-Based Wireless Sensor Networking Protocols for Spaceflight Applications

Wireless sensor networks (WSNs) have the capacity to revolutionize data gathering in both spaceflight and terrestrial applications. WSNs provide a huge advantage over traditional, wired instrumentation since they do not require wiring trunks to connect sensors to a central hub. This allows for easy sensor installation in hard to reach locations, easy expansion of the number of sensors or sensing modalities, and reduction in both system cost and weight. While this technology offers unprecedented flexibility and adaptability, implementing it in practice is not without its difficulties. Recent advances in standards-based WSN protocols for industrial control applications have come a long way to solving many of the challenges facing practical WSN deployments. In this paper, we will overview two of the more promising candidates - WirelessHART from the HART Communication Foundation and ISA100.11a from the International Society of Automation - and present the architecture for a new standards-based sensor node for networking and applications research

Nodos sensores inalámbricos con antenas directivas de banda simple o doble para aplicaciones en agricultura

Abstract Introduction: This paper presents the design of two wireless sensor nodes, with communications systems that integrate in one case a broadband antenna for operation in the 900MHz and 2.4GHz bands, along with a circuit that allows to select the appropriate radio for operation in some of these bands with the same antenna and the other makes use of a high gain antenna for operation in the 2.4GHz band. The proposed design offers a solution to the problem of propagation of radio frequency (RF) signals in forests and plantations for applications in smart agriculture that make use of wireless sensor networks (WSN). Objective: Design of two wireless sensor nodes, with communications systems that integrate directive antennas in one case for dual band operation (900MHz-2.4GHz) and in the other with high gain antennas (2.4GHz) for applications in smart agriculture. Method: The design of the wireless nodes makes use of the PSoC (programmable chip system) model CY8CKIT-059 5LP, which integrates temperature, humidity, inclination, distance, light intensity and movement sensors that use ZigBee as a wireless communication protocol. The antennas are designed with appropriate electromagnetic simulators and the resulting prototypes from this process are characterized in impedance by means of a vector network analyzer (VNA) and radiation patterns in an anechoic chamber. The full operation of the nodes is validated in the laboratory and in open spaces. Results: The double-band node with logarithmic antenna allows packet transfer at distances of 4.1km (915MHz) and 938m (2.44GHz), along with a switching circuit that allows one of the bands to be selected depending on the propagation characteristics of the medium where the node will be installed. On the other hand, the node with SPA antenna allows transfer of packets up to 2.5km (2.44GHz). The antenna characterization results are as follows: The logarithmic antenna has a maximum gain of 2.74dBi (915MHz) and 3.06dBi (2.44GHz) respectively, with an impedance bandwidth of 3.196:1, for an S11 <-10dB. The SPA antenna resonates at a center frequency of 2.44 GHz with a gain of 7.2 dBi; an impedance bandwidth of 16.8%, for an S11 <-10dB. Conclusions: This proposal improves the performance in wireless sensor networks since the approaches allow modularity, versatility and application in different areas including agriculture, enabling longer reaches and a more extensive coverage compared to the nodes that make use of conventional XBee antennas.Introducción: Este artículo presenta el diseño de dos nodos de sensores inalámbricos, con sistemas de comunicaciones que integran en un caso una antena de banda ancha para operación en las bandas de 900MHz y 2.4GHz, junto con un circuito que permite seleccionar el radio apropiado para operación en alguna de estas bandas con la misma antena y el otro hace uso de una antena de alta ganancia para operación en la banda de 2.4GHz. El diseño propuesto ofrece una solución al problema de propagación de señales de radio frecuencia (RF) en bosques y plantaciones para aplicaciones en agricultura inteligente que hacen uso de redes de sensores inalámbricos (WSN). Objetivo: Diseñar dos nodos de sensores inalámbricos, con sistemas de comunicaciones que integran antenas directivas en un caso para operación en doble banda (900MHz-2.4GHz) y en el otro con antenas de alta ganancia (2.4GHz) para aplicaciones en agricultura inteligente. Metodología: El diseño de los nodos inalámbricos hace uso del PSoC (sistema programable en chip) modelo CY8CKIT-059 5LP, al cual se integran sensores de temperatura, humedad, inclinación, distancia, intensidad de luz y movimiento que utilizan ZigBee como protocolo de comunicación inalámbrica. Las antenas son diseñadas con simuladores electromagnéticos apropiados y los prototipos resultantes de este proceso son caracterizados en impedancia mediante un analizador de redes (VNA) y en diagrama en una cámara anecoica. La operación integral de los nodos se valida en el laboratorio y en espacios abiertos. Resultados: El nodo de doble banda con antena logarítmica permite transferencia de paquetes a distancias de 4.1km (915MHz) y de 938m (2.44GHz), junto con un circuito de conmutación que permite seleccionar una de las bandas dependiendo de las características de propagación del medio donde se instalará el nodo. Por otra parte, el nodo con antena SPA permite transferencia de paquetes hasta 2.5Km (2.44GHz). Los resultados de la caracterización de las antenas son: La antena logarítmica presenta una ganancia máxima de 2.74dBi (915MHz) y 3.06dBi (2.44GHz) respectivamente, con un ancho de banda de impedancia de 3.196:1, para un <-10dB. La antena SPA resuena a una frecuencia central de 2.44 GHz con una ganancia de 7.2 dBi; un ancho de banda de impedancia del 16.8%, para un <-10dB. Conclusiones: La propuesta consigue mejorar el desempeño en redes inalámbricas de sensores por su modularidad, versatilidad y su aplicación en diferentes áreas incluida la agricultura, lo que permite obtener mejores alcances y cobertura más amplia cuando se compara con los nodos que hacen uso de antenas XBee convencionales

Smart-antenna techniques for energy-efficient wireless sensor networks used in bridge structural health monitoring

Abstract: It is well known that wireless sensor networks differ from other computing platforms in that 1- they typically require a minimal amount of computing power at the nodes; 2- it is often desirable for sensor nodes to have drastically low power consumption. The main benefit of the this work is a substantial network life before batteries need to be replaced or, alternatively, the capacity to function off of modest environmental energy sources (energy harvesting). In the context of Structural Health Monitoring (SHM), battery replacement is particularly problematic since nodes can be in difficult to access locations. Furthermore, any intervention on a bridge may disrupt normal bridge operation, e.g. traffic may need to be halted. In this regard, switchbeam smart antennas in combination with wireless sensor networks (WSNs) have shown great potential in reducing implementation and maintenance costs of SHM systems. The main goal of implementing switch-beam smart antennas in our application is to reduce power consumption, by focusing the radiated energy only where it is needed. SHM systems capture the dynamic vibration information of a bridge structure in real-time in order to assess the health of the structure and to predict failures. Current SHM systems are based on piezoelectric patch sensors. In addition, the collection of data from the plurality of sensors distributed over the span of the bridge is typically performed through an expensive and bulky set of shielded wires which routes the information to a data sink at one end of the structure. The installation, maintenance and operational costs of such systems are extremely high due to high power consumption and the need for periodic maintenance. Wireless sensor networks represent an attractive alternative, in terms of cost, ease of maintenance, and power consumption. However, network lifetime in terms of node battery life must be very long (ideally 5–10 years) given the cost and hassle of manual intervention. In this context, the focus of this project is to reduce the global power consumption of the SHM system by implementing switched-beam smart antennas jointly with an optimized MAC layer. In the first part of the thesis, a sensor network platform for bridge SHM incorporating switched-beam antennas is modelled and simulated. where the main consideration is the joint optimization of beamforming parameters, MAC layer, and energy consumption. The simulation model, built within the Omnet++ network simulation framework, incorporates the energy consumption profiles of actual selected components (microcontroller, radio interface chip). The energy consumption and packet delivery ratio (PDR) of the network with switched-beam antennas is compared with an equivalent network based on omnidirectional antennas. In the second part of the thesis, this system model is leveraged to examine two distinct but interrelated aspects: Gallium Arsenide (GaAs) based solar energy harvesting and switched-beam antenna strategies. The main consideration here is the joint optimization of solar energy harvesting and switchedbeam directional antennas, where an equivalent network based on omnidirectional antennas acts as a baseline reference for comparison purposes.Il est bien connu que les réseaux de capteurs sans fils diffèrent des autres plateformes informatiques étant donné 1- qu’ils requièrent typiquement une puissance de calcul minimale aux noeuds du réseau ; 2- qu’il est souvent désirable que les noeuds capteurs aient une consommation d’énergie dramatiquement faible. La principale retombée de ce travail réside en la durée de vie allongée du réseau avant que les piles ne doivent être remplacées ou, alternativement, la capacité de fonctionner indéfiniment à partir de modestes sources d’énergie ambiente (glânage d’énergie). Dans le contexte du contrôle de la santé structurale (CSS), le remplacement de piles est particulièrement problématique puisque les noeuds peuvent se trouver en des endroits difficiles d’accès. De plus, toute intervention sur un pont implique une perturbation de l’opération normale de la structure, par exemple un arrêt du traffic. Dans ce contexte, les antennes intelligentes à commutation de faisceau en combinaison avec les réseaux de capteurs sans fils ont démontré un grand potentiel pour réduire les coûts de réalisation et d’entretien de systèmes de CSS. L’objectif principal de l’intégration d’antennes à commutation de faisceau dans notre application réside dans la réduction de la consommation énergétique, réalisée en concentrant l’énergie radiée uniquement là où elle est nécessaire. Les systèmes de CSS capturent l’information dynamique de vibration d’une structure de pont en temps réel de manière à évaluer la santé de la structure et prédire les failles. Les systèmes courants de CSS sont basés sur des senseurs piézoélectriques planaires. De plus, la collecte de données à partir de la pluralité de senseurs distribués sur l’étendue du pont est typiquement effectuée par le biais d’un ensemble coûteux et encombrant de câbles blindés qui véhiculent l’information jusqu’à un point de collecte à une extremité de la structure. L’installation, l’entretien, et les coûts opérationnels de tels systèmes sont extrêmement élevés étant donné la consommation de puissance élevée et le besoin d’entretien régulier. Les réseaux de capteurs sans fils représentent une alternative attrayante, en termes de coût, facilité d’entretien et consommation énergétique. Toutefois, la vie de réseau en termes de la durée de vie des piles doit être très longue (idéalement de 5 à 10 ans) étant donné le coût et les problèmes liés à l’intervention manuelle. Dans ce contexte, ce projet se concentre sur la réduction de la consommation de puissance globale d’un système de CSS en y intégrant des antennes intelligentes à commutation de faisceau conjointement avec une couche d’accès au médium (couche MAC) optimisée. Dans la première partie de la thèse, une plateforme de réseau de capteurs sans fils pour le CSS d’un pont incorporant des antennes à commutation de faisceaux est modélisé et simulé, avec pour considération principale l’optimisation des paramètres de sélection de faisceau, de la couche MAC et de la consommation d’énergie. Le modèle de simulation, construit dans le logiciel de simulation de réseaux Omnet++, incorpore les profils de consommation d’énergie de composants réels sélectionnés (microcontrôleur, puce d’interface radio). La consommation d’énergie et le taux de livraison de paquets du réseau avec antennes à commutation de faisceau est comparé avec un réseau équivalent basé sur des antennes omnidirectionnelles. Dans la deuxième partie de la thèse, le modèle système proposé est mis à contribution pour examiner deux aspects distrincts mais interreliés : le glânage d’énergie à partir de cellules solaire à base d’arséniure de Gallium (GaAs) et les stratégies liées aux antennes à commutation de faisceau. La considération principale ici est l’optimisation conjointe du glânage d’énergie et des antennes à commutation de faisceau, en ayant pour base de comparaison un réseau équivalent à base d’antennes omnidirectionnelles

Innovative energy-efficient wireless sensor network applications and MAC sub-layer protocols employing RTS-CTS with packet concatenation

of energy-efficiency as well as the number of available applications. As a consequence there are challenges that need to be tackled for the future generation of WSNs. The research work from this Ph.D. thesis has involved the actual development of innovative WSN applications contributing to different research projects. In the Smart-Clothing project contributions have been given in the development of a Wireless Body Area Network (WBAN) to monitor the foetal movements of a pregnant woman in the last four weeks of pregnancy. The creation of an automatic wireless measurement system for remotely monitoring concrete structures was an contribution for the INSYSM project. This was accomplished by using an IEEE 802.15.4 network enabling for remotely monitoring the temperature and humidity within civil engineering structures. In the framework of the PROENEGY-WSN project contributions have been given in the identification the spectrum opportunities for Radio Frequency (RF) energy harvesting through power density measurements from 350 MHz to 3 GHz. The design of the circuits to harvest RF energy and the requirements needed for creating a WBAN with electromagnetic energy harvesting and Cognitive Radio (CR) capabilities have also been addressed. A performance evaluation of the state-of-the art of the hardware WSN platforms has also been addressed. This is explained by the fact that, even by using optimized Medium Access Control (MAC) protocols, if the WSNs platforms do not allow for minimizing the energy consumption in the idle and sleeping states, energy efficiency and long network lifetime will not be achieved. The research also involved the development of new innovative mechanisms that tries and solves overhead, one of the fundamental reasons for the IEEE 802.15.4 standard MAC inefficiency. In particular, this Ph.D. thesis proposes an IEEE 802.15.4 MAC layer performance enhancement by employing RTS/CTS combined with packet concatenation. The results have shown that the use of the RTS/CTS mechanism improves channel efficiency by decreasing the deferral time before transmitting a data packet. In addition, the Sensor Block Acknowledgment MAC (SBACK-MAC) protocol has been proposed that allows the aggregation of several acknowledgment responses in one special Block Acknowledgment (BACK) Response packet. Two different solutions are considered. The first one considers the SBACK-MAC protocol in the presence of BACK Request (concatenation) while the second one considers the SBACK-MAC in the absence of BACK Request (piggyback). The proposed solutions address a distributed scenario with single-destination and single-rate frame aggregation. The throughput and delay performance is mathematically derived under both ideal conditions (a channel environment with no transmission errors) and non ideal conditions (a channel environment with transmission errors). An analytical model is proposed, capable of taking into account the retransmission delays and the maximum number of backoff stages. The simulation results successfully validate our analytical model. For more than 7 TX (aggregated packets) all the MAC sub-layer protocols employing RTS/CTS with packet concatenation allows for the optimization of channel use in WSNs, v8-48 % improvement in the maximum average throughput and minimum average delay, and decrease energy consumption