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

ZigBee-Based wireless sensor network topologies using one and multiple coordinators

Wireless Sensor Networks (WSN) have been a cost-effective and feasible solution for a wide range of applications, such as communications infrastructure, traffic networks, telecommunications systems, military operations and so forth. IEEE804.15.4 ZigBee network model is ideally suited to the constraints of WSN in terms of bandwidth, processing power and battery capacity. This paper investigated tree and mesh routing in WSN with multiple coordinators and the failure of single coordinator using OPNET Modeler v14 which is an efficient computational platform for data networks simulation. Throughput, delay, traffic received, MAC Load are studied in this system and the results showed that tree routing was better suited for WSN than mesh routing and mobility of end node in multiple coordinator network was the best

Performance assessment of mobility solutions for IPv6-based healthcare wireless sensor networks

This thesis focuses on the study of mobile wireless sensor networks applied to healthcare scenarios. The promotion of better quality-of-life for hospitalized patients is addressed in this research work with a solution that can help these patients to keep their mobility (if possible). The solution proposed allows remote monitoring and control of patients’ health in real-time and without interruptions. Small sensor nodes able to collect and send wirelessly the health parameters allow for the control of the patients' health condition. A network infrastructure, composed by several access points, allows the connection of the sensor nodes (carried by the patients) to remote healthcare providers. To ensure continuous access to sensor nodes special attention should be dedicated to manage the transition of these sensor nodes between different access points’ coverage areas. The process of changing an access point attachment of a sensor node is called handover. In that context, this thesis proposes a new handover mechanism that can ensure continuous connection to mobile sensor nodes in a healthcare wireless sensor network. Due to the limitations of sensor nodes’ resources, namely available energy (these sensor nodes are typically powered by small batteries), the proposed mechanism pays a special attention in the optimization of energy consumption. To achieve this optimization, part of this work is dedicated to the construction of a small sensor node. The handover mechanism proposed in this work is called Hand4MAC (handover mechanism for MAC layer). This mechanism is compared with other mechanisms commonly used in handover management. The Hand4MAC mechanism is deployed and validated through by simulation and in a real testbed. The scenarios used for the validation reproduces a hospital ward. The performance evaluation is focused in the percentage of time that senor nodes are accessible to the network while traveling across several access points’ coverage areas and the energy expenditures in handover processes. The experiments performed take into account various parameters that are the following: number of sent messages, number of received messages, multicast message usage, energy consumption, number of sensor nodes present in the scenario, velocity of sensor nodes, and time-to-live value. In both simulation and real testbed, the Hand4MAC mechanism is shown to perform better than all the other handover mechanisms tested. In this comparison it was only considered the most promising handover mechanisms proposed in the literature.Fundação para a Ciência e a Tecnologia (FCT

Application framework for wireless sensor networks [thesis]

Wireless Sensor Networks (WSNs) are based on innovative technologies that had revolutionized the methods in which we interact with the environment; i.e., through sensing the physical (e.g., fire motion, contact) and chemical (e.g., molecular concentration) properties of the natural surroundings. The hardware in which utilized by WSNs is rapidly evolving into sophisticated platforms that seamlessly integrate with different vendors and protocols (plug-n-play). In this thesis, we propose a WSN framework which provides assistance with monitoring environmental conditions; we focus on three main applications which include: a. Air-quality monitoring, b. Gas-leak detection, and c. Fire sensing. The framework involves four specifications: 1. Over the air programming (OTAP), 2. Network interconnections, 3. Sensors manageability, and 4. Alarm signaling. Their aim is to enhance the internetwork relations between the WSNs and the outside-world (i.e., main users, clients, or audience); by creating a medium in which devices efficiently communicate, independent of location or infrastructure (e.g., Internet), in order to exchange data among networked-objects and their users. Therefore, we propose a WSN-over-IP architecture which provides several renowned services of the Internet; the major functionalities include: live-data streaming (real-time), e-mailing, cloud storage (external servers), and network technologies (e.g., LAN or WLAN). WSNs themselves operate independently of the Internet; i.e., their operation involve unique protocols and specific hardware requirements which are incompatible with common network platforms (e.g., within home network infrastructure). Hybrid technologies are those which support multiple data-communication protocols within a single device; their main capabilities involve seamless integration and interoperability of different hardware vendors. We propose an overall architecture based on hybrid communication technology in which data is transmitted using three types of protocols: 802.11 (Wi-Fi), 802.15.4 and Digimesh (WSN)

The design and evaluation of Wireless Sensor Networks for applications in industrial locations

In manufacturing industries, there exist many applications where Wireless Sensor Networks (WSN\u27s) are integrated to provide wireless solution for the automated manufacturing processes. It is well known that industrial environments characterized by extreme conditions such as high temperature, pressure, and electromagnetic (EM) interference that can affect the performance of the WSN\u27s. The key solution to overcome this performance issue is by monitoring the received Signal Strength Index (RSSI) at the received sensor of the WSN device and track frame error rate of wireless packets. ZigBee is a wireless sensor network (WSN) standard designed for specific needs of the remote monitoring sensor system. Zigbee networks can be established by three different topologies: start, hybrid, and mesh. In this research project, the interest in analyzing the characteristics of the Zigbee performance was completed using a star topology network. Three performance parameters were obtained: the RSSI signal to monitor the received wireless packets from the sending node, path-lost exponent to determine the effect of industrial environment on wireless signals, and the frame error rate to know the discontinue time. The study was in three phases and took place in two settings: The first was at the manufacturing laboratory at the University of Northern Iowa, the second and the third were at the facility of a Midwestern manufacturing company. The study aimed to provide an analytical tool to evaluate the performances of Zigbee networks in industrial environments and compare the results to show that harsh environments do affect its performance. The study also involved testing the performance of WSN. This was done by simulating input/output Line passing with digital and analog data. Packets were sent from one node and counted at the receiving side to measure the packet error rate of WSN in industrial environment. In conclusion, investigating the WSN\u27s systems performance in industrial environment provides is crucial to identify the effects of the harsh conditions. It is necessary to run similar investigation to prevent the malfunction of the manufacturing applications. Testing a simple WSN in industrial environment can be capable of predicting the performance of the network. It is also recommended to have an embedded approach to WSN applications that can self-monitor its performance

Localization of nodes in wired and wireless networks

This thesis focuses on the implementation of algorithms for localization of nodes in wired and wireless networks. The thesis is organized into two papers. The first paper presents the localization algorithms based on time of arrival (TOA) and time difference of arrival (TDOA) techniques for computer networks such as the Internet by using round-trip-time (RTT) measurements obtained from known positions of the gateway nodes. The RTT values provide an approximate measure of distance between the gateway nodes and an unknown node. The least squares technique is then used to obtain an estimated position of the unknown node. The second paper presents localization of an unknown node during route setup messages in wireless ad hoc and sensor networks using a new routing protocol. A proactive multi-interface multichannel routing (MMCR) protocol, recently developed at Missouri S&T, was implemented on the Missouri S&T motes. This protocol calculates link costs based on a composite metric defined using the available end-to-end delay, energy utilization, and bandwidth, and it chooses the path that minimizes the link cost factor to effectively route the information to the required destination. Experimental results indicate enhanced performance in terms of quality of service, and implementation of this protocol requires no modification to the current IEEE 802.11 MAC protocol. Received signal strength indicator (RSSI) values are recorded from the relay nodes (gateway nodes) to the unknown node during route setup messages. The location of the unknown node is estimated using these values with some a priori profiling and the known positions of the relay nodes as inputs to the least squares technique --Abstract, page iv

Wireless Sensors for Health Monitoring of Marine Structures and Machinery

Remote structural and machinery health monitoring (SMHM) of marine structures such as ships, oil and gas rigs, freight container terminals, and marine energy platforms can ensure their reliability. However, the wired sensors currently used in these applications are difficult and expensive to install and maintain. Wireless Sensor Networks (WSN) can potentially replace them but there are significant capability gaps that currently prevent their long-term deployment in the harsh marine environment and the structurally-complex, compartmentalised, all-metal scenarios with high volume occupancy of piping, ducting and operational machinery represented by marine structures. These gaps are in sensing, processing and communication hardware and firmware capabilities, reduction of power consumption, hardware assembly and packaging for reliability in the marine environment, reliability of wireless connectivity in the complex metal structures, and software for WSN deployment planning in the marine environment. Taken together, these gaps highlight the need for a systems integration methodology for marine SMHM and this is the focus of the research presented in this thesis. The research takes an applied approach by first designing the hardware and firmware for two wireless sensing modules specifically for marine SMHM, one a novel eddy-current-based 3D module for measuring multi-axis metal structural displacement, the second a fully integrated module for monitoring of structure and machinery reliability. The research then addresses module assembly and packaging methods to ensure reliability in the marine environment, the development of an efficient methodology for characterising the reliability of wireless connectivity in complex metal structures, and development of user interface software for planning WSN deployment and for managing the collection of WSN data. These are then individually and collectively characterised and tested for performance and reliability in laboratory, land-based and marine deployments. In addition to the research outcomes in each of these individual aspects, the overall research outcome represents a systems integration methodology that now allows deployment, with a high expectation of reliability of marine SMHM WSNs