What is a Wireless Sensor Network in IoT? Application Fields of Wireless Sensor Networks
Wireless sensor networks have many types of sensors that can detect a variety of phenomena in the surrounding environment, including seismic, electromagnetic, temperature, humidity, noise, light intensity, pressure, soil composition, size, speed, and direction of moving objects. Potential application fields can be summarized as: military, aviation, explosion-proof, disaster relief, environment, medical, health care, home, industry, business and other fields.
Compared with the traditional wired network, wireless sensor network technology has obvious advantages, the main requirements are: low energy consumption, low cost, versatility, network topology, security, real-time, data-centric and so on.
1. What is a wireless sensor network?
Wireless Sensor Network (WSN) is a self-organizing network composed of a large number of sensor nodes. These sensor nodes can not only sense the environmental information in the network, but also have simple computing power. Relevant information is transmitted in the network and has certain communication capabilities. Sensor node is the most important node in WSN, it is the foundation of the whole WSN, and has the functions of sensing data, processing data, storing data and transmitting data. Sensor nodes are responsible for sensing environmental information in the network, collecting monitoring data and reporting it to user nodes through the sink node.
2. Characteristics of Wireless Sensor Networks
Compared with other wireless communication networks, WSN has its own remarkable characteristics.
2.1 Large-scale: The large-scale nature of sensor networks is divided into two meanings. One is to deploy sensor nodes in some large-scale monitoring areas, such as forests, mountains and other areas to monitor fires or perform other environmental monitoring activities; The other is to deploy a large density of sensor nodes in a limited area.
2.2 Self-organization: WSN is a distributed self-organized wireless network, it has no central control and management, and is a network composed of peer nodes. This distributed structure can better adapt to changes in the network, and can be automatically configured and managed when the network changes, with high flexibility and practicability.
2.3 Routing multi-hop: Due to the large monitoring range of WSN, the data transmission distance between sensor nodes will be very long, so the multi-hop routing forwarding method is often used in WSN, so that each node has the routing and forwarding function, which can reduce the number of nodes. Transmit power and reduce network energy consumption.
2.4 Robustness: WSN is often used in wild areas with harsh environments such as mountains and forests. In this environment, the maintenance of sensor nodes is difficult to achieve, so the network needs to have a certain robustness. When the battery is exhausted and cannot work normally, other nodes in the network can be automatically adjusted to ensure the normal operation of the WSN.
2.5 Compared with wired products, wireless sensor network products have the characteristics of low cost, large range, flexible deployment, and mobile support. Industrial wireless sensor network products are used in mechanical parameter detection, industrial monitoring, smart power, mine safety, medical health, environmental monitoring and other industries. At the same time, industrial wireless sensor network products also face market challenges such as extending the working time of nodes, increasing the communication distance, miniaturization, standardization and other market challenges.
3. Application Fields of Wireless Sensor Networks
With the rapid development of science and technology, human beings have entered the information age, and sensor technology, which is the most important and basic technology for information acquisition, has also been greatly developed. The sensor information acquisition technology has gradually developed from the past simplification to the direction of integration, miniaturization and networking, and will bring about an information revolution.
Sensor nodes can continuously perform data collection, event detection, event identification, location monitoring and node control. These characteristics and wireless connection methods of sensor nodes make the application prospects of wireless sensor networks very broad, involving almost every social and economic activity. field.
3.1 Application in the military field
In the military field, because WSN has the characteristics of dense and random distribution, it is very suitable for application in harsh battlefield environment. Using WSN can monitor the strength and equipment in the enemy's area, monitor the battlefield situation in real time, locate the target, monitor nuclear attack or biochemical attack, etc.
3.2 Assisting agricultural production
WSN is especially suitable for production and scientific research in the following areas. For example, the monitoring of temperature, humidity and light in the greenhouse planting room and soil, the analysis and measurement of the growth law of precious commercial crops, the breeding and production of high-quality grapes, etc., can bring great help to rural development and farmers' income increase. Using WSN to build an automatic monitoring system for agricultural environment, using a set of network equipment to complete data collection and environmental control of wind, light, water, electricity, heat and pesticides, can effectively improve the degree of intensive agricultural production and improve the scientific nature of agricultural production and planting .
3.3 Application in ecological environment monitoring and forecasting
In environmental monitoring and forecasting, wireless sensor networks can be used to monitor crop irrigation conditions, soil air conditions, environmental and migration conditions of livestock and poultry, wireless soil ecology, large-area surface monitoring, etc., and can be used for planetary detection, meteorology and geography Research, flood monitoring, etc. Based on the wireless sensor network, several sensors can be used to monitor rainfall, river water level and soil moisture, and then predict flash floods to describe ecological diversity, so as to monitor animal habitat ecology. Population complexity studies, among other things, can also be done by tracking birds, small animals, and insects.
With the increasing attention to the environment, the scope of environmental science is getting wider and wider. Collecting raw data by traditional means is a difficult task. Wireless sensor networks provide convenience for the acquisition of randomness research data in the field, especially in the following aspects: Scattering millions of sensors in the forest can provide the fastest information for the determination of the location of forest fires; sensor networks can provide The location of chemical pollution and the determination of chemical pollution sources do not need to manually venture into the contaminated area; determine rainfall conditions to provide accurate information for flood control and drought relief; real-time monitoring of air pollution, water pollution and soil pollution; monitoring of ocean, atmosphere and soil composition.
3.4 Infrastructure Condition Monitoring System
WSN technology plays a positive role in the safe construction of large-scale projects and the monitoring of building safety conditions. By arranging sensor nodes, the conditions of buildings, bridges and other buildings can be observed in a timely and accurate manner, and dangerous situations can be detected and repaired in time to avoid serious consequences.
3.5 Application in the industrial field
In terms of industrial safety, sensor network technology can be used in dangerous working environments, such as arranging sensor nodes in coal mines, oil drilling, nuclear power plants and assembly lines, which can monitor the safety status of the working environment at any time and provide guarantees for the safety of workers. In addition, sensor nodes can also replace some staff to perform tasks in dangerous environments, which not only reduces the degree of danger, but also improves the accuracy and speed of response to dangerous situations.
Due to its convenient deployment and flexible networking, WSN is gradually playing a role in warehousing logistics management and smart homes.
The wireless sensor network enables sensors to form a local Internet of Things, exchange and obtain information in real time, and finally converge to the Internet of Things, forming an important information source and basic application of the Internet of Things.
3.6 Ensure safe and smooth traffic in intelligent transportation
Intelligent Transportation System (ITS) is a new type of transportation system developed on the basis of the traditional transportation system. —environment” organically combined.
The intelligent transportation system mainly includes several aspects, such as the collection of traffic information, the transmission of traffic information, traffic control and guidance. The wireless sensor network can provide an effective means for the information collection and transmission of the intelligent transportation system, which can be used to monitor the traffic flow, speed and other information in all directions on the road surface and intersection. And use the calculation method to calculate the optimal plan, and output control signals to the execution subsystem to guide and control the passage of vehicles, so as to achieve the preset goal.
3.7 Application in medical system and health care
At present, many countries are facing the problem of population aging, and my country's aging speed ranks first in the world. The number of elderly people over 60 years old in China has reached 160 million, accounting for about 12% of the total population, and the number of elderly people over 80 years old has reached 18.05 million, accounting for about 11.29% of the total elderly population. The emergence of a large number of families with a couple supporting four elderly people and having one child has further increased the pressure of supporting the elderly. The average proportion of "empty-nest elderly" in major cities has reached more than 30%, and even more than 50% in individual large and medium-sized cities. This poses a serious challenge to the traditional Chinese family pension system.
Wireless sensor network technology provides rich background information through continuous monitoring and makes early warning responses, which is not only expected to solve this problem but also greatly improve the quality and efficiency of medical care. The wireless sensor network integrates microelectronics technology, embedded computing technology, modern network and wireless communication and distributed information processing technologies, and can complete the real-time information of various environments or monitoring objects through the cooperation of various integrated micro-sensors. Monitoring, sensing and collection. It is one of the frontier hotspots that is currently attracting international attention, involving a high degree of interdisciplinary and highly integrated knowledge.
3.8 Application in Information Appliances
The gradual popularization of wireless sensor networks has promoted the rapid development of information appliances and network technology. The main equipment of the home network has been expanded from a single machine to a variety of home appliances. The smart home network control nodes based on the wireless sensor network are home and external networks. It provides a basic platform for the connection of information appliances and equipment between the internal network.
Sensor nodes are embedded in home appliances and connected to the Internet through a wireless network to create a more convenient and more humane smart home environment. The remote monitoring system can be used to realize the remote control of home appliances. The wireless sensor network enables residents to monitor the water meters, electricity meters, gas meters, electric water heaters, air conditioners, rice cookers, etc. in the home through the browser in any place where they can access the Internet, and the gas leakage of the security system Alarm system, outsider intrusion warning system, etc., and can set commands through the browser to remotely control home appliances.
Home security can also be monitored at any time through image sensing devices. Using sensor networks can build smart kindergartens, monitor children's early education environment, and track children's activity trajectories.
In short, the application prospect of wireless sensor network is very attractive. Wireless sensor network (WSN) is considered to be one of the important technologies affecting the future life of human beings. This emerging technology provides a new way for people to acquire and process information. Due to the characteristics of WSN itself, there is a big difference between it and the existing traditional network technology, which brings many new challenges to people.
4. The significance of wireless sensor network
4.1 Wireless sensor networks have attracted worldwide attention and are considered to be the second largest network after the Internet.
4.2 Wireless sensor network is known as one of the most influential technologies in the 21st century; it is the first of ten emerging technologies that change the world; it is one of the four major high-tech industries in the future of the world.
4.3 In the research and application of wireless sensor network, my country and developed countries started almost simultaneously, and it has become one of the few projects in the forefront of the world in the field of information in my country.
5. Seven concepts related to wireless sensor networks
Sensors in WSN communicate wirelessly, so network settings are flexible, device locations can be changed at any time, and wired or wireless connections to the Internet are possible. A multi-hop self-organizing network formed by wireless communication. Jixun Xiaobian has sorted out several concepts involved in wireless sensor networks.
5.1 WSN (Wireless Sensor Networks)
Wireless Sensor Networks is a distributed sensor network with sensors at the tip that sense and inspect the outside world. Sensors in WSN communicate wirelessly, so network settings are flexible, device locations can be changed at any time, and wired or wireless connections to the Internet are possible. A multi-hop self-organizing network formed by wireless communication.
5.2 WS (Wireless Sensor)
The component modules of the Wireless Sensor are encapsulated in a shell. When working, it will be powered by a battery or a vibration generator to form a wireless sensor network node. It consists of randomly distributed micro nodes integrated with sensors, data processing units and communication modules. The way of organization constitutes a network. It can collect the digital signal of the device and transmit it to the wireless gateway of the monitoring center through the wireless sensor network, and directly send it to the computer for analysis and processing. If desired, the wireless sensor can also transmit the entire time-history signal acquired in real time. The monitoring center can also wirelessly transmit control, parameter setting and other information to the nodes through the gateway. The data conditioning, acquisition and processing module sends the weak signal output by the sensor to the analog-to-digital converter after amplifying, filtering and other conditioning circuits, converts it into a digital signal, and sends it to the main processor for digital signal processing to calculate the effective value of the sensor, displacement value etc.
5.3 DTU (Data Transfer Unit)
The data transmission unit is a wireless terminal device specially used for converting serial port data into IP data or converting IP data into serial port data for transmission through a wireless communication network.
5.4 RTU (Remote Terminal Unit)
The full name of RTU is the remote terminal control system, which is responsible for the monitoring and control of on-site signals and industrial equipment. RTU (Remote Terminal Unit) is the core device that constitutes an enterprise's comprehensive automation system. It is usually composed of signal input/output modules, microprocessors, wired/wireless communication equipment, power supplies and housings. It is controlled by microprocessors and supports network systems. Through its own software (or intelligent software) system, it can ideally realize the functions of telemetry, remote control, remote signaling and remote adjustment of the primary instrument on the production site by the central monitoring and dispatching system of the enterprise.
5.5 GPRS (General Packet Radio Service)
GPRS is the abbreviation of General Packet Radio Service Technology. It is a mobile data service available to GSM mobile phone users and belongs to the data transmission technology in the second generation of mobile communication. GPRS can be said to be the continuation of GSM. GPRS is different from the previous way of continuous transmission on the channel. It transmits in the form of packets. Therefore, the cost borne by the user is calculated by the unit of transmission data, rather than using the entire channel, which is theoretically cheaper. The transmission rate of GPRS can be increased to 56 or even 114Kbps.
ZigBee is a low-power LAN protocol based on the IEEE802.15.4 standard. According to international standards, ZigBee technology is a short-range, low-power wireless communication technology. The name (also known as the Purple Bee Protocol) comes from the bee's figure-of-eight dance, because the bee (bee) communicates with its companions the location information of the pollen by the "dance" of flying and "zig" flapping its wings. That is to say, bees rely on this way to form a communication network in the colony. It is characterized by close proximity, low complexity, self-organization, low power consumption, and low data rate. Mainly suitable for automatic control and remote control field, can be embedded in various equipment. In short, ZigBee is a cheap, low-power short-range wireless networking communication technology. ZigBee is a low-speed short-distance wireless network protocol. ZigBee protocol from bottom to top is physical layer (PHY), media access control layer (MAC), transport layer (TL), network layer (NWK), application layer (APL) and so on. The physical layer and the media access control layer follow the provisions of the IEEE 802.15.4 standard.
5.7 Modbus Protocol
Modbus protocol is a common language applied to electronic controllers. Through this protocol, controllers can communicate with each other, with other devices via a network (eg, Ethernet). It has become a common industry standard. With it, control equipment produced by different manufacturers can be connected into an industrial network for centralized monitoring. This protocol defines a message structure that controllers recognize and use, regardless of the network over which they communicate. It describes the process of a controller requesting access to other devices, how to respond to requests from other devices, and how to detect and log errors. It establishes a common format for the format and content of message fields.
The above is the introduction of wireless sensor related knowledge. The development of WSN benefits from the rapid development of Micro-Electro-Mechanism System (MEMS), System on Chip (SoC), wireless communication and low-power embedded technology.
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