1 Overview of wireless sensor networks
Wireless Sensor Network (WSN) is a new type of information acquisition system. It is a multi-hop self-organizing network system formed by a large number of inexpensive micro sensor nodes deployed in the monitoring area. The purpose is to collaboratively monitor, sense, and collect information about various perceptual objects in the network coverage area, and process the information and ultimately send it to the observer. A wireless sensor network is a low-power, self-organizing network. It is generally composed of one or more base stations (Sink nodes) and a large number of wireless network nodes deployed in the monitoring area and equipped with various types of sensors. Each node has low cost, low power consumption, and has certain computing processing power and communication capability. Although the data collected by a single node is not accurate or reliable, a large number of nodes cooperate to form a highly unified network structure, which improves the accuracy of data collection and the reliability of operation. It can be deployed in enemy-occupied areas, disaster areas, and nuclear reactors. Data collection, transmission, etc. are carried out in special areas where human resources are unreachable, and have characteristics unmatched by other networks, and can be widely used in the fields of national defense, environmental monitoring, and smart home.
2 Significant features of wireless sensor networks
Compared with other wireless communication networks such as cellular networks and wireless LANs, wireless sensor networks have their own distinctive features:
1) Distributed, self-organizing. A wireless sensor network is a network of peer nodes that does not have central control. Management and networking are very simple and flexible. Independent of a fixed infrastructure, each node has a routing function that can form a network through self-coordination and automatic placement, without the need for additional ancillary facilities and artificial means.
2) Robustness. Due to factors such as energy limitation, environmental interference and human damage, the sensor nodes will be damaged, resulting in some sensor nodes not working properly, but a large number of randomly distributed nodes can coordinate and complement each other to ensure that the damage of some sensor nodes will not affect the overall situation. task.
3) Scalability. When a new wireless sensor node is added to the network, other external conditions are not needed. The original wireless sensor network can effectively integrate the newly added nodes, so that the newly added nodes can quickly integrate into the network and participate in the global work.
4) Dynamic topology. A wireless sensor network is a dynamic network. Nodes in the network may exit the network due to exhausted energy or other faults; some nodes may be in working state, some nodes may be in a closed state, and no network communication is involved; it may also be added. A large number of nodes are integrated into the network, which will change the topology of the network at any time.
5) Application related. Wireless sensor networks are used to perceive the objective physical world and acquire physical world information. Different sensor network applications are concerned with different physical quantities, so different application backgrounds will result in different node hardware platforms, software systems, and network protocols. Wireless sensor networks cannot have a unified communication protocol platform like the Internet, and sensor network technology must be studied for specific applications. This is also a distinguishing feature of wireless sensor networks that distinguish them from traditional network systems.
6) Large scale. In order to improve the reliability of the network, a large number of sensor nodes are usually deployed in the target area, and the sensor network may contain thousands or even tens of thousands of sensor nodes. The large-scale nature of sensor networks can also achieve greater signal-to-noise ratios through different spatial perspectives, thereby improving monitoring accuracy.
7) High redundancy. The large-scale deployment of nodes makes wireless sensor networks usually have higher node redundancy, network link redundancy and data redundancy, which makes the system highly fault tolerant.
8) Spatial location addressing. Wireless sensor networks generally do not need to support point-to-point communication between any two sensor nodes. The sensor nodes do not have to have a globally unique identifier and do not have to use IP addressing of the Internet. Users often do not care which node the data is collected on, but care about the spatial location of the data, so space location addressing can be adopted. In this sense, the sensor network usually uses the data itself as a query or transmission thread, so the sensor network is a data-centric network.
3 Application Analysis of Wireless Sensor Networks
Due to technical constraints, large-scale commercial use of wireless sensor networks will take time. However, with the shrinking of microprocessors and the improvement of performance, small and medium-sized WSNs have begun to be put into commercial use in the industrial market. Its applications are mainly concentrated in the following areas:
1 Environmental monitoring
As people pay more and more attention to environmental issues, more and more environmental data needs to be collected. The emergence of wireless sensor networks facilitates the acquisition of random research data, and can also avoid the traditional data collection methods. Invasive damage caused by the environment. For example, Intel Research Lab researchers have connected 32 small sensors to the Internet to read the climate on Maine Island in Maine to evaluate the conditions of a sea Swallow's Nest. Wireless sensor networks can also track the migration of migratory birds and insects, study the effects of environmental changes on crops, and monitor the composition of the ocean, atmosphere, and soil. In addition, it can also be used in precision agriculture to monitor pests in crops, soil pH and fertilization status.
2 medical care
Scientists at the University of Rochester use wireless sensors to create a smart medical room that uses dust to measure important signs of occupants (blood pressure, pulse and breathing), sleeping posture, and activity 24 hours a day. Intel also introduced home care technology based on WSN. The technology was developed as part of the Center for Aging Services Technologies (CAST), a technology project to address the aging society. The system helps elderly people, Alzheimer's patients, and people with disabilities to live in the home by embedding semiconductor sensors in homes and equipment such as shoes and furniture. Networking of sensors with wireless communication can efficiently deliver the necessary information to facilitate care. It also reduces the burden on the caregiver.
3 military fields
Due to the dense and random distribution of wireless sensor networks, it is very suitable for use in harsh battlefield environments, making it ideal for use in harsh battlefield environments, including reconnaissance of enemy forces, monitoring of forces, equipment and supplies, and judgment of organisms. Chemical attack and other uses. The US Department of Defense's Vision Research Bureau has invested tens of millions of dollars to help universities develop "smart dust" sensor technology.
4 target tracking
The DARPA-supported Sensor IT project explores how WSN technology can be applied to the military to achieve so-called "over-the-horizon" battlefield monitoring. Sensor Web, hosted by UCB's professor, is a sub-project of Sensor IT. The technical feasibility of applying WSN to battlefield target tracking is verified in principle. The UAV carrying the WSN node under the wing flies to the target area and then drops the node. Finally, it is randomly removed from the monitored area and installed at the node. The seismic wave sensor can detect external Japanese standards, such as tanks, armored vehicles, etc., and estimate the distance according to the strength of the signal, synthesize the observation data of multiple nodes, finally locate the target, and draw the trajectory of its movement.
5 other uses
WSN is also used in some hazardous industrial environments such as wells, nuclear power plants, etc., through which staff can implement safety monitoring. It can also be used in the transportation field as a powerful tool for vehicle monitoring. In addition, in the industrial automation production line and other fields, Intel is testing a wireless network in the factory, which consists of 210 sensors on 40 machines, so that the monitoring system will greatly improve the operating conditions of the factory. . It can significantly reduce the cost of inspection equipment, and because it can identify problems ahead of time, it will reduce downtime, increase efficiency, and extend equipment life. It is believed that with the development and advancement of related technologies, wireless sensor technology will certainly get more applications.
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