Wireless sensor network is composed of temperature, humidity, pressure, position, vibration, sound and other nodes. These nodes can be used in a variety of real-time applications to complete intelligent detection, neighbor node discovery, data processing and storage, data acquisition, target tracking, monitoring and storage tasks, and control, synchronization, node positioning and effective routing between base stations and nodes.

In recent years, the technology of wireless sensor network (WSN) in processor, communication and low-power embedded computing devices is developing continuously, which is the most standard service in commercial and industrial applications. Wireless sensor network is composed of temperature, humidity, pressure, position, vibration, sound and other nodes. These nodes can be used in a variety of real-time applications to complete intelligent detection, neighbor node discovery, data processing and storage, data acquisition, target tracking, monitoring and storage tasks, and control, synchronization, node positioning and effective routing between base stations and nodes.

At present, wireless sensor networks are beginning to be organized in an enhanced way. It is expected that in 10 to 15 years, the world will be protected by wireless sensor networks and provide services to them through the Internet, which can be measured by the Internet becoming a physical network. This technology has unlimited potential in many application fields, such as medical treatment, environment, transportation, military, entertainment, national defense, crisis management and intelligent space.

Wireless sensor network (WSN) is a kind of wireless network, including a large number of cyclic, self-directed, micro and low-power devices, which are called sensor nodes. These networks of course cover a large number of spatially distributed, small, battery powered embedded devices. These devices collect and process data through the network, and transmit the data to the operators, which controls the computing and processing capabilities. Nodes are microcomputers that work together to form networks.

Sensor node is a multi-functional and energy-saving wireless device. Nodes are widely used in industry. The collection of sensor nodes collects data from the environment to achieve specific application goals. In wireless sensor networks, the number of nodes can be hundreds. Compared with sensor networks, ad hoc networks have fewer nodes without any structure.

As for the architecture of wireless sensor networks, the most common WSN architecture follows the OSI architecture model. The architecture of wireless sensor network includes five layers and three cross layers. In sensor networks, we mainly need five layers: application layer, transport layer, network layer, data link layer and physical layer. The three cross planes are power management, mobility management and task management. These layers of wireless sensor networks are used to complete wireless sensor networks, and make sensors work together to improve the overall efficiency of wireless sensor networks.

application layer

The application layer is responsible for traffic management and provides software for many applications that transform data in a clear form to find positive information. Sensor networks are widely used in agriculture, military, environment, medical and other fields.

Transport layer

The function of transport layer is to provide congestion avoidance and reliability. These protocols use different mechanisms to identify and recover losses. When a system plans to connect to other networks, the transport layer is absolutely necessary.

Providing a reliable loss recovery is more energy-efficient, which is one of the main reasons why TCP is not suitable for wireless sensor networks. Generally speaking, transport layer can be divided into packet driven and event driven. There are some popular protocols in the transport layer, namely STCP (sensor transmission control protocol), port (price oriented reliable transport protocol) and psfq (pump slow acquisition protocol).

network layer

The main function of the network layer is routing. It has many application-based tasks, but in fact, the main tasks are energy saving, partial memory and buffer. The sensor has no common ID and must be self-organized.

The simple idea of routing protocol is to explain reliable lanes and redundant lanes according to a certainty scale called metric, which varies from protocol to protocol. There are many existing network layer protocols, which can be divided into plane routing and hierarchical routing, as well as time driven, query driven and event driven.

data link layer

The data link layer is responsible for multiplexing data frame detection, data flow, MAC and error control, and confirming the point to point (or) point to multipoint reliability.

physical layer

The physical layer provides edges for transmitting bitstreams over the physical medium. This layer is responsible for frequency selection, carrier frequency generation, signal detection, modulation and data encryption. IEEE 802.15.4 is considered as a typical low rate specific area and wireless sensor network, which has the advantages of low cost, low power consumption, low density and communication range, and can improve the service life of battery. CSMA / CA is used to support star to point topology. There are several versions of IEEE 802.15.4. V.

The characteristics of wireless sensor networks include the following aspects: power consumption limitation of nodes with batteries; the ability to deal with node failures; some mobility and heterogeneity of nodes; scalability of large-scale distribution; the ability to ensure strict environmental conditions; the advantages of simple use, cross layer design and wireless sensor networks.

The advantages of wireless sensor network include: the network arrangement can be carried out without fixed infrastructure; it is suitable for mountainous areas, sea, rural areas, forests and other places that are difficult to reach; if additional workstations are needed, it will be more flexible in case of temporary situation; it is cheap to carry out pricing; it avoids a lot of wiring; it can provide accommodation for new equipment at any time; it can be used for wireless sensor network Open by using centralized monitoring, etc.

Wireless sensor networks can be composed of many different types of sensors, such as low sampling rate, seismic, magnetic, thermal, visual, infrared, radar and acoustic. These sensors can well monitor various environmental conditions. Sensor nodes are used for constant sensing, event ID, event detection and local control of actuators. The applications of wireless sensor networks mainly include military applications, health applications, environmental applications, home applications, commercial applications, regional monitoring, health care monitoring, environment / earth sensing, air pollution monitoring, forest fire detection, landslide detection, water quality monitoring, industrial monitoring and other commercial fields.

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