Research on Wireless Sensor Networks and Their Applications

Abstract: With the rapid development and increasing maturity of microelectronics technology, computer technology, wireless communication and sensor technology, wireless sensor networks have developed rapidly. Wireless sensor networks can monitor, sense, collect and process information of various monitored objects in real time, and have become one of the most cutting-edge topics in the field of scientific research. This article mainly introduces the concept, structure, characteristics and application of wireless sensor networks in some fields, and looks forward to the future development of wireless sensor networks. Keywords
: Wireless Sensor Network (WSN); Sensor Node; Self-organization; Application

The rapid development and increasing maturity of microelectronics technology, computer technology, wireless communication and sensor technology have promoted the development of low-cost, low-power wireless sensor networks (WSN). Wireless sensor network research has a wide range of application prospects: military reconnaissance, environmental science, medical health, industrial automation, commercial applications, etc. The research of sensor networks is very necessary. This article mainly introduces the concept, structure, characteristics, and application of wireless sensor networks in some fields, and looks forward to the future development of wireless sensor networks.

1 Wireless Sensor Network
A wireless sensor network is a wired or wireless network composed of a group of sensors in an Ad hoc manner. Its purpose is to collaboratively sense, collect and process information about objects in the geographic area covered by the sensor network and transmit it to observers. This sensor network integrates sensor technology, embedded computer technology and wireless communication technology, and can collaboratively sense, monitor and collect information about objects in various environments. Through collaborative information processing of this information, accurate information about the objects is obtained, and then transmitted to users who need this information in an Ad hoc manner.

2 Main features of WSN
As a new type of network, compared with traditional wireless networks, wireless sensor networks have the following characteristics:
1) Large-area spatial distribution For example, in military applications, wireless sensor networks can be deployed on the battlefield to track the enemy's military operations. Intelligent terminals can be installed in propaganda materials, bullets or shells in large quantities and dropped at the target location to form a large-area surveillance network.
2) Energy-constrained The power supply of each node in the network is limited. Most networks work in unmanned areas or harsh environments that are harmful to the human body. It is almost impossible to replace the power supply, which requires the network to have low power consumption to extend the life of the network. And try to save power consumption as much as possible.
3) Automatic network configuration and automatic node identification include automatic networking, identity authentication of terminals entering the network, and prevention of illegal user intrusion. Compared with sensor networks deployed in pre-specified locations, wireless sensor networks can be configured by referring to the Ad hoc method. Of course, the premise is that there must be a set of suitable communication protocols to ensure that the network runs automatically without human intervention.
4) Automatic management and high collaboration of the network In wireless sensor networks, data processing is completed by the nodes themselves. The data-centric feature is another feature of wireless sensor networks. Each node only knows the location and identity of its neighboring nodes. The sensor network processes signals and communicates through the cooperation between adjacent nodes, which is highly collaborative.
5) The topology of the sensor network changes quickly. The characteristics of the sensor network itself make the topology of the sensor network change very quickly, which poses a challenge to the effectiveness of various algorithms in the network. In addition, if the nodes have the ability to move, it may also bring about changes in the topology of the network.

3 Structure of WSN nodes
Sensor nodes are generally composed of four modules: sensing, data processing, wireless communication and power supply, as shown in Figure 1.

The sensing module includes sensors and analog-to-digital conversion modules, which are responsible for the collection and data conversion of information in the detection area; the data processing module is composed of an embedded system, including CPU, memory, embedded operating system, etc., which is responsible for controlling the operation of the entire sensor node, storing and processing the data collected by itself and the data sent by other nodes: the wireless communication module is composed of network, MAC, transceiver, etc., and is responsible for wireless communication with other sensor nodes, exchanging control information and sending and receiving collected data: the power supply module provides the energy required for the operation of the sensor node, usually using a micro battery.

4 Application fields of WSN
1) Military application WSN has the characteristics of rapid deployment, self-organization, strong concealment and high fault tolerance, so it is very suitable for military application. WSN can be used to monitor enemy forces and equipment, real-time monitoring of the battlefield, target positioning, battlefield assessment, monitoring and searching for nuclear attacks and biochemical attacks. By directly spreading sensor nodes to enemy positions through aircraft or artillery shells, battlefield information can be collected very covertly and accurately.
2) Agricultural and environmental applications Agricultural and environmental applications of wireless sensor networks include: monitoring of environmental conditions that affect crops (precision agricultural monitoring), tracking the movement of small animals such as birds and insects, detection of ocean, soil, and atmospheric components, forest fire monitoring, pollution monitoring. Rainfall monitoring, river water level monitoring, flood monitoring, etc.
3) Medical care With the popularization of indoor networks, wireless sensor networks have also shown their talents in medical research and nursing. The main applications include remote health management, care for critically ill patients or the elderly, life support equipment, real-time collection and management of pathological data, emergency rescue, etc.
4) Smart Home The design goal of the smart home system is to connect various home appliances in the house so that they can operate automatically and cooperate with each other to provide the residents with as much convenience and comfort as possible. Embedding sensor nodes in home appliances and furniture and connecting them to the Internet through wireless networks will provide people with a more comfortable, convenient and more humane smart home environment. Using the remote monitoring system, home appliances can be remotely controlled.
5) Smart Traffic Application The smart traffic monitoring system uses sound, image, video, temperature, humidity and other sensors. The nodes are deployed around the intersections, and the nodes deployed on the vehicles also include GPS global positioning devices. The aggregation node can be installed on roadside columns, bars and other traffic facilities, the gateway node can be integrated in the traffic signal controller at the intersection, the dedicated sensor terminal node can be buried under the road surface or installed on the roadside, and the moving vehicles on the road can also install sensor nodes to dynamically join the sensor network. Through the proprietary network of the signal controller, the collected data is sent to the traffic control center for further processing.

5 Conclusion
Wireless sensor networks have developed very rapidly, and have attracted widespread attention in the military, industrial and academic fields of many countries in the world. They have become one of the hot spots in international wireless network research. Judging from the current research status abroad, most of the research on wireless sensor networks is still in the stage of theoretical research and small-scale experiments, and there is still a certain distance from practical application. The research on wireless sensor networks in China is still in its infancy. Whether in theoretical research or commercial fields, there is a huge space for the research and development of wireless sensor networks, and it has great research and application prospects.