1、附录 外文文献原文、译文 The realization of wireless sensor networks and applications in agriculture 1 Introduction Wireless sensor networks (Wireless Sensor Network, WSN) are deployed in the monitoring area by the large number of low-cost micro sensor nodes, wireless communication through the formation of a mu
2、lti-hop network self-organization. The aim is to perceive collaboration, collection and processing of network coverage in the perception of objects, and send observers. Sensors, sensing object and the observer, constitute the three elements of the network. Here that the sensor is not in the traditio
3、nal sense of the simple perception of physical signals and the sensor into a digital signal, which is the sensor module, data processing module and wireless communication module integrated in a small physical unit, that is , enhanced features than many traditional sensors can not only be aware of en
4、vironmental information, but also data processing and wireless communication capabilities. With the built-in sensor nodes in a variety of sensors, where the environment can measure heat, infrared, sonar, radar and seismic signals and other signals to detect temperature, humidity, noise, light intens
5、ity, pressure, soil composition, moving object the size, speed and direction, and so many physical phenomena of interest to us. Wireless sensor network is a new mode of information acquisition and information processing. Because of the shortage of water resources are at a considerable degree, plus 9
6、0% of the waste, untreated sewage or handling standards for direct discharge of water pollution, water quality is lower than 11% of agricultural water supply standards. Water is the lifeblood of agriculture, is the controlling element of the ecological environment, but it is also strategic economic
7、resources, extraction of groundwater by pump irrigation of farmland, rational use of water resources, development of water supply, improve the ecological environment in China is currently accurate Agriculture key, so use of irrigation water and energy supply in todays world is the general trend of t
8、echnological development. 2 Overview of wireless sensor networks 2.1 The system architecture of wireless sensor networks Wireless sensor network system architecture shown in Figure 1, typically include sensor nodes, aggregation nodes and management nodes. Clouds in the observation area sensor nodes
9、in order to constitute a network of self-organized manner. Sensor node processing the collected information, the way to multi-hop relay the information transmitted to the sink node. Then through the Internet or mobile communication network and other channels to reach management node. End-users throu
10、gh the management of wireless sensor network node management and configuration, release monitoring tasks or collect return data. 2.2 The characteristics of wireless sensor networks (1) self-organization. As the network and the network itself, the physical environment in which the unpredictability of
11、 factors, such as: can not pre-set exact location of the node can not know in advance the relationship between the nodes adjacent to some nodes because of energy depletion or other causes of death, newnodes join and so on, make the network deployment and expansion without the need to rely on any of
12、the default network infrastructure, layered protocol between nodes and distributed algorithms by coordinating their behavior, a node can quickly start automatically after the formation of a separatemulti-hop routing network. (2) multi-hop routing. Limited communication distance of nodes in the netwo
13、rk, the node can only communicate directly with its neighbors, if beyond the range of its RF communication nodes, you need to be routed through intermediate nodes. (3) the spatial distribution of a large area, node density, the number is huge. (4) data-center. In wireless sensor networks, people usu
14、ally only care about a region within a certain numerical observations, and not to the specific observations concerned a single node. (5) Node capacity constraints. The energy of sensor nodes, processing power, storage capacity and communication ability and so is very limited. Power energy restricted
15、. As the miniaturization of sensor nodes, node battery power is limited, and because physical constraints make it difficult for nodes to replace the battery, so battery power limitations of sensor nodes is the wireless sensor network design one of the most critical constraints, which directly determ
16、ines the networks worklife. computing and storage capacity is limited.Bring low-cost micro sensor nodes weak processor, memory capacity of small features, so it can not perform complex calculations, and the traditional Internet network protocols and algorithms on the relative maturity of wireless se
17、nsor networks, too costly, difficult to use,must therefore be simple, effective protocols and algorithms, such as the ZigBee protocol. communication is limited.Typically, the energy consumption of wireless communication and communication distance d E the relation: E = kdn.Where 2 n 4.N is usually ta
18、ken as 3. 2.3 The shortcomings of wireless sensor networks (1) energy is limited. Sensor nodes are usually powered by ordinary batteries or lithium batteries, the energy limited.In unattended environments, wireless sensor network applications is one of the bottlenecks. (2) node cost is higher. Curre
19、ntly on the market price in thousands of sensor nodes over the wireless sensor network nodes need many, limiting promote the use of wireless sensor networks. (3) The poor security. As a result of wireless channel, distributed control technology, the network more vulnerable to passive eavesdropping,
20、active intrusion and other attacks. (4) collaboration. Individual sensor nodes are often unable to complete the target of measurement, tracking and recognition, while the number of sensor nodes need to exchange information through the algorithm on data obtained for processing, aggregation and filter
21、ing, the final result. 3 the current wireless sensor network applications in agriculture View of the water shortage and the demand for farmland irrigation, irrigation equipment under the existing conditions of application fields of crops, soil, water distribution, etc., for precise analysis of the current agricultural solved key technical problems, we propose a use ofwireless sensor network technology, suitable for large areas of agricultural land Intelligent Irrigation Control. 3.1 The system works Of SCM system with multiple sensors on the humidity, temperature, rainfall, pH,
