A wireless sensor network (WSN) is a distributed system composed of many battery-powered devices,... more A wireless sensor network (WSN) is a distributed system composed of many battery-powered devices, which operate with no human intervention for long periods of time. These devices are called sensor nodes or motes. Motes present features of both embedded and general-purpose systems (Han et al., 2005). Their tiny size, scarce resources, and their autonomous nature lead to strong restrictions of computation, communication, power, and storage. Typically, they are deployed in an ad-hoc fashion over a geographical area (e.g. a volcano, a glacier, an office), which is to be monitored. This means that-depending on the environment where they are installed-it could result very difficult to perform activities of maintenance such as the replacement of the node's batteries. Software built for the sensor nodes must be reliable and robust due to the difficulty for accessing sensor nodes, and sensor nodes must operate in an autonomous way even in presence of failures. Motes are interconnected through wireless links and they execute a simple, small application, which is developed using a sensor node-specific operating system. Typically, sensor network applications consist of sensing the environment through different type of sensors (e.g. temperature, humidity, GPS, imagers), transforming analogical data into digital data in the node itself, and forwarding the data to the network. Data is forwarded through a multi-hop protocol to a special node denominated gateway, which is intended to redirect all data from the wireless network to a base station (e.g. PC, laptop), where the data will be permanently stored in order to allow data post-processing and analysis. Figure 1 shows the three elements previously described: sensor nodes, gateway, base station. 1.1 Data classification in a WSN WSNs generate larger data sets as sampling frequency increase. Sensor nodes must manage data proceeding from different sources: internal data produced by the sensor node itself (e.g. sensor measurements, application data, logs), and external data transmitted by other nodes in the network (e.g. protocol messages, data packets, commands). Since the data
Precision agriculture is a field which provides one of the most suitable scenarios for the deploy... more Precision agriculture is a field which provides one of the most suitable scenarios for the deployment of wireless sensor networks (WSNs). The particular characteristics of agricultural environments -which may vary significantly with location -make WSNs a key technology able to provide accurate knowledge to farmers. This knowledge represents a valuable resource because it enables real-time decision making with regard to issues such as establishing water saving policies while providing adequate irrigation and choosing the right time to harvest the fruit based on its maturity. This article proposes a methodology consisting of a set of well-defined phases that cover the complete life cycle of WSN applications for agricultural monitoring. We have studied different existing real-world scenarios where WSNs are being applied. Based on this study we have discovered that there exist significant commonalities but no methodology that specifies the best practices that should be used in the general, crop-independent case. The lack of a general methodology negatively impacts the amount of effort, development time, and cost of developing applications.
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