Wireless sensor networks. Wireless distributed sensor networks. Wireless Sensor Network Software

Maxim Sergievsky

The latest wireless communication technologies and progress in the production of microcircuits have allowed over the past few years to move to the practical development and implementation of a new class of distributed communication systems - sensor networks.

Wireless sensor networks (wireless sensor networks) consist of miniature computing and communication devices - mots ( from English motes - dust particles), or sensors. A mote is a board usually no more than one cubic inch in size. The board houses the processor, memory - flash and operational, digital-to-analog and analog-to-digital converters, radio frequency transceiver, power supply and sensors. Sensors can be very diverse; they are connected via digital and analog connectors. More often than others, temperature, pressure, humidity, light, vibration sensors are used, less often - magnetoelectric, chemical (for example, measuring the content of CO, CO2), sound and some others. The set of used sensors depends on the functions performed by wireless sensor networks. The mot is powered by a small battery. Motes are used only for collection, primary processing and transmission of sensory data. The appearance of bots produced by various manufacturers is shown in Fig. 1.

The main functional processing of the data collected by the motes is carried out at the node, or gateway, which is a fairly powerful computer. But in order to process the data, you must first get it. For this purpose, the node must be equipped with an antenna. But in any case, only motes that are close enough to it are accessible to the node; in other words, the node does not receive information directly from each mote. The problem of obtaining sensory information collected by mots is solved as follows. Mots can exchange information with each other using radio frequency transceivers. This is, firstly, sensory information read from sensors, and secondly, information about the state of devices and the results of the data transfer process. Information is transmitted from some motes to others along the chain, and as a result, the motes nearest to the gateway discard all the accumulated information to it. If some of the motes fail, the sensor network should continue to work after reconfiguration. But in this case, naturally, the number of information sources decreases.

To perform the functions, a specialized operating system is installed on each motor. Most wireless sensor networks today use TinyOS, an OS developed at the University of Berkeley. TinyOS is open source software; it is available at www.tinyos.net. TinyOS is an event-driven real-time operating system designed to operate under limited computing resources. This OS allows motes to automatically establish connections with neighbors and form a sensor network of a given topology. The last release of TinyOS 2.0 appeared in 2006.

The most important factor in wireless sensor networking is the limited capacity of the batteries installed in the motes. It should be borne in mind that it is usually impossible to replace the batteries. In this regard, it is necessary to carry out on mots only the simplest primary processing, focused on reducing the amount of transmitted information, and, most importantly, to minimize the number of data reception and transmission cycles. To solve this problem, special communication protocols have been developed, the most famous of which are the protocols of the ZigBee alliance. This alliance (website www.zigbee.org) was created in 2002 specifically to coordinate work in the field of wireless sensor networks. It includes the largest developers of hardware and software: Philips, Ember, Samsung, IBM, Motorola, Freescale Semiconductor, Texas Instruments, NEC, LG, OKI and many others (more than 200 members in total). Intel is not a member of the alliance, although it supports its activities.

In principle, to develop a standard, including a protocol stack for wireless sensor networks, ZigBee used the previously developed IEEE 802.15.4 standard, which describes the physical layer and the level of access to the medium for wireless data transmission networks over short distances (up to 75 m) with low power consumption, but with a high degree of reliability. Some characteristics of radio data transmission for the IEEE 802.15.4 standard are given in table. 1.

Table 1. IEEE 802.15.4 radio transmission characteristics

At the moment, ZigBee has developed the only standard in this area, which is supported by the production of fully compatible hardware and software products. ZigBee protocols allow devices to hibernate b aboutmost of the time, which significantly extends battery life.

It is obvious that it is not so easy to develop data exchange schemes between hundreds and even thousands of mots. Among other things, it is necessary to take into account the fact that sensor networks operate in unlicensed frequency ranges, therefore, in some cases, interference caused by extraneous sources of radio signals may occur. It is also advisable to avoid repeated transmission of the same data, and in addition, take into account that due to insufficient energy intensity and external influences, the motes will fail forever or for some time. In all such cases, the communication schemes must be modified. Since one of the most important features of TinyOS is the automatic selection of the network layout and data transmission routes, wireless sensor networks are essentially self-configuring.

Most often, a mote should be able to independently determine its location, at least in relation to the other mote to which it will transmit data. That is, first, all motes are identified, and then a routing scheme is formed. In general, all motes - devices of the ZigBee standard - are divided into three classes according to the level of complexity. The highest of them - the coordinator - manages the operation of the network, stores data about its topology and serves as a gateway for transmitting data collected by the entire wireless sensor network for further processing. Sensor networks usually use one coordinator. A moto of medium complexity is a router, that is, it can receive and transmit data, and also determine the direction of transmission. Finally, the simplest moto can only transmit data to the nearest router. Thus, it turns out that the ZigBee standard supports a network with a cluster architecture (Fig. 2). The cluster is formed by a router and the simplest motes from which it requests sensory data. Cluster routers relay data to each other, and ultimately the data is passed to the coordinator. The coordinator usually has a link to the IP network, where the data is sent for final processing.

In Russia, developments related to the creation of wireless sensor networks are also being carried out. Thus, the High-Tech Systems company offers its hardware and software platform MeshLogic for building wireless sensor networks (website www.meshlogic.ru). The main difference between this platform and ZigBee is its focus on building peer-to-peer mesh networks (Fig. 3). In such networks, the functionality of each mote is the same. The possibility of self-organization and self-healing of mesh topology networks allows, in the event of a part of the motes out of operation, to spontaneously form a new network structure. True, in any case, you need a central functional unit that receives and processes all the data, or a gateway to transfer data to the processing unit. Spontaneously created networks are often called the Latin term Ad Hoc, which means "for a specific case."

In MeshLogic networks, each mote can perform packet relay, which is similar in function to a ZigBee router. MeshLogic networks are completely self-organizing: no coordinator node is provided. Various devices can be used as radio frequency transceivers in MeshLogic, in particular Cypress WirelessUSB, which, like ZigBee devices, operate in the 2.4 ... 2.4835 GHz frequency range. It should be noted that only the lower layers of the protocol stack exist for the MeshLogic platform. It is believed that the upper levels, in particular the network and application, will be created for specific applications. The configurations and basic parameters of two MeshLogic motes and one ZigBee mote are shown in Table. 2.

Table 2. Main characteristics of mots from different manufacturers

Note that there are no integrated touch sensors on these boards.

Let's point out what first of all distinguishes wireless sensor networks from conventional computing (wired and wireless) networks:

• complete absence of any cables - electrical, communication, etc .;
• the possibility of compact placement or even integration of mots into environmental objects;
• reliability of both individual elements and, more importantly, the entire system as a whole; in some cases, the network can function if only 10-20% of the sensors (mots) are operational;
• no need for personnel for installation and maintenance.

Sensor networks can be used in many application areas. Wireless sensor networks are a promising new technology and all related projects are mostly under development. Let's indicate the main areas of application of this technology:

• defense systems and security;
• environmental control;
• monitoring of industrial equipment;
• security systems;
• monitoring of the state of agricultural land;
• power supply management;
• control of ventilation, air conditioning and lighting systems;
• fire alarm;
• inventory control;
• tracking cargo transportation;
• monitoring the physiological state of a person;
• personnel control.

From a fairly large number of examples of using wireless sensor networks, we will single out two. The most famous is perhaps the deployment of the network aboard a BP oil tanker. There, using a network built on the basis of Intel equipment, the condition of the vessel was monitored in order to organize its preventive maintenance. BP has analyzed whether the sensor network can operate on board ships in the extreme temperatures, high vibration, and significant levels of radio frequency interference found in some areas of the ship. The experiment was successful, several times were automatically reconfigured and restored to the network.

An example of another pilot project that has been implemented is the deployment of a sensor network at a US Air Force base in Florida. The system has demonstrated good ability to recognize various metal objects, including moving ones. The use of the sensor network made it possible to detect the penetration of people and cars into the controlled area and track their movements. To solve these problems, we used motes equipped with magnetoelectric and temperature sensors. Currently, the scope of the project is expanding, and a wireless sensor network is already being installed on a 10,000x500 m test site. The corresponding application software is being developed by several American universities.

The advantages of wireless sensor network technologies can be effectively used to solve various applied problems related to distributed collection, analysis and transmission of information.

Building automation

In some building automation applications, the use of traditional wired data transmission systems is impractical for economic reasons.

For example, you want to implement a new or expand an existing system in an existing building. In this case, the use of wireless solutions is the most acceptable option, because no additional installation work is required in violation of the interior decoration of the premises, practically no inconvenience is caused to employees or residents of the building, etc. As a result, the cost of system implementation is significantly reduced.

Another example would be open-plan office buildings, for which it is impossible to specify the exact location of the sensors during the design and construction phase. At the same time, the layout of offices can be changed many times during the operation of the building, therefore, the time and money spent on reconfiguring the system should be minimal, which can be achieved by using wireless solutions.

In addition, the following examples of systems based on wireless sensor networks can be cited:

• monitoring of temperature, air consumption, presence of people and control of heating, ventilation and air conditioning equipment in order to maintain a microclimate;
• lighting control;
• power supply management;
• collection of readings from apartment meters for gas, water, electricity, etc .;
• monitoring of the condition of the bearing structures of buildings and structures.

Industrial automation

Until now, the widespread use of wireless communication in the field of industrial automation has been constrained by the low reliability of radio channels compared to wired connections in harsh industrial conditions, but wireless sensor networks are fundamentally changing the situation, since by their nature, they are resistant to various kinds of disturbances (for example, physical damage to the node, the appearance of interference, changing obstacles, etc.). Moreover, under some conditions, a wireless sensor network can provide even greater reliability than a wired communication system.

Solutions based on wireless sensor networks fully meet industry requirements:

• fault tolerance;
• scalability;
• adaptability to operating conditions;
• energy efficiency;
• taking into account the specifics of the applied problem;
• economic profitability.

Wireless sensor network technologies can be used in the following industrial automation tasks:

• remote control and diagnostics of industrial equipment;
• maintenance of equipment according to the current state (forecasting the safety margin);
• monitoring of production processes;
• telemetry for research and testing.

Other applications

The unique features and differences of wireless sensor networks from traditional wired and wireless data transmission systems make their use effective in a wide variety of areas. For instance:

• security and defense:
  • control over the movement of people and equipment;
  • operational communications and intelligence;
  • perimeter control and remote monitoring;
  • assistance in carrying out rescue operations;
  • monitoring of property and valuables;
  • security and fire alarm;
• environmental monitoring:
  • pollution monitoring;
  • agriculture;
• healthcare:
  • monitoring the physiological state of patients;
  • location control and notification of medical personnel.

Almost all areas of life in the 21st century depend on information and communication technologies (ICT). Data is exchanged not only between people, but also all kinds of intelligent systems, mobile phones, wearable devices, ATMs, sensors. At least 5 billion devices are already connected to the Internet of Things. The functioning of any large complexes - industrial, energy, agricultural, shopping centers, museums, offices, residential buildings - is associated with constant monitoring of the situation on their territory. Sensitive sensors in real time monitor the health of the equipment, the organization of the interaction of devices with each other, warn about the need to replace them or about emergency situations. With rapidly growing volumes of data, an easy and convenient way to exchange it between devices and data centers is needed.

Print version:

Wireless sensor networks (BSS, Wireless Sensor Networks), consisting of wireless sensors and control devices and capable of self-organization using intelligent algorithms, demonstrate large-scale prospects of use for monitoring human health, the state of the environment, the functioning of industrial and transport systems, accounting for various resources etc. This issue of the newsletter presents technological trends in the field of FSS related to ensuring continuous operation of wireless sensors and their application in two areas of the modern economy - advanced manufacturing and smart energy (smart grid).

Self-charging sensor devices

For the development of wireless sensor networks, it is important to solve the problem of their power supply. A promising trend is the creation of durable autonomous devices with minimal energy consumption - converted from external sources.

Wireless sensor devices can, for example, be powered by a radio signal sent to them by a transmitter (like radio frequency identification (RFID) devices or contactless smart cards). This energy is used by the device both for recharging the sensor and for generating a response signal with information about the current state of the controlled object.

Another way is the passive conversion of energy from the external environment (energy harvesting): solar energy (outside the room in a fairly clear weather), thermal energy, mechanical vibration energy (from devices operating nearby - assembly machines, conveyors, etc.), vibration energy of the sensor itself (in the case of wearable devices), background radio emissions from surrounding electrical appliances (including Wi-Fi).

Implementation of advanced production based on wireless sensor networks

Inappropriate use of resources and production facilities, generation of a large amount of polluting waste, lack of constant monitoring of the state of facilities at enterprises - these and other problems of modern industry stimulate the transition to the advanced manufacturing model. It is characterized by the use of new materials and environmentally friendly technologies (green technologies), as well as the widespread use of ICT and intelligent systems, in particular, robotics and wireless sensor networks.

Industrial wireless sensor networks (IBSS, Industrial Wireless Sensor Networks) - the most important factor in the implementation of advanced production. To control and monitor the state of objects at the enterprise (equipment, conveyors, assembly machines, reactors), a set of interconnected wireless sensors and information systems are used that process data from sensors and interact with controlled objects using control devices. Such an automated system reacts to any changes in indicators at the enterprise, notifies personnel about accidents and problem situations, analyzes the efficiency of equipment use, assesses the level of environmental pollution and the volume of waste generated.

Smart Grids

The global problem of irrational use of electricity is especially urgent for Russia. Large costs of generating electricity increase the cost of production, which puts a double burden on the end user. To improve the efficiency and reliability of energy systems, many countries are moving to the concept of smart grids (smart grid).

Such a network manages in real time all generating sources connected to it, transmission and distribution networks and facilities that consume electricity. To control the "smart" power grid, wireless sensor networks are used that control the volume of energy production and energy consumption in its various sections. With the help of information systems, the optimal distribution of energy in the network is calculated, forecasts are made for different seasons and periods of the day, energy production and delivery are synchronized, and the safety of power lines is monitored. To increase the efficiency of the power grid, its non-critical elements are switched off for the period of reduced activity.

Monitoring of global technological trends is carried out by the Institute for Statistical Studies and Economics of Knowledge of the Higher School of Economics () as part of the HSE Program of Fundamental Research.

When preparing the trendletter, the following sources were used: Forecast of the scientific and technological development of the Russian Federation until 2030 (prognoz2030.hse.ru), materials of the scientific journal "Foresight" (foresight-journal.hse.ru), data Web of Science, Orbit, idc.com, marketsandmarkets.com, wintergreenresearch.com, greentechmedia.com, greenpatrol.ru, etc.

Maxim Sergievsky

The latest wireless communication technologies and progress in the production of microcircuits have allowed over the past few years to move to the practical development and implementation of a new class of distributed communication systems - sensor networks.

Wireless sensor networks (wireless sensor networks) consist of miniature computing and communication devices - mots ( from English motes - dust particles), or sensors. A mote is a board usually no more than one cubic inch in size. The board houses the processor, memory - flash and operational, digital-to-analog and analog-to-digital converters, radio frequency transceiver, power supply and sensors. Sensors can be very diverse; they are connected via digital and analog connectors. More often than others, temperature, pressure, humidity, light, vibration sensors are used, less often - magnetoelectric, chemical (for example, measuring the content of CO, CO2), sound and some others. The set of used sensors depends on the functions performed by wireless sensor networks. The mot is powered by a small battery. Motes are used only for collection, primary processing and transmission of sensory data. The appearance of bots produced by various manufacturers is shown in Fig. 1.

The main functional processing of the data collected by the motes is carried out at the node, or gateway, which is a fairly powerful computer. But in order to process the data, you must first get it. For this purpose, the node must be equipped with an antenna. But in any case, only motes that are close enough to it are accessible to the node; in other words, the node does not receive information directly from each mote. The problem of obtaining sensory information collected by mots is solved as follows. Mots can exchange information with each other using radio frequency transceivers. This is, firstly, sensory information read from sensors, and secondly, information about the state of devices and the results of the data transfer process. Information is transmitted from some motes to others along the chain, and as a result, the motes nearest to the gateway discard all the accumulated information to it. If some of the motes fail, the sensor network should continue to work after reconfiguration. But in this case, naturally, the number of information sources decreases.

To perform the functions, a specialized operating system is installed on each motor. Most wireless sensor networks today use TinyOS, an OS developed at the University of Berkeley. TinyOS is open source software; it is available at www.tinyos.net. TinyOS is an event-driven real-time operating system designed to operate under limited computing resources. This OS allows motes to automatically establish connections with neighbors and form a sensor network of a given topology. The last release of TinyOS 2.0 appeared in 2006.

The most important factor in wireless sensor networking is the limited capacity of the batteries installed in the motes. It should be borne in mind that it is usually impossible to replace the batteries. In this regard, it is necessary to carry out on mots only the simplest primary processing, focused on reducing the amount of transmitted information, and, most importantly, to minimize the number of data reception and transmission cycles. To solve this problem, special communication protocols have been developed, the most famous of which are the protocols of the ZigBee alliance. This alliance (website www.zigbee.org) was created in 2002 specifically to coordinate work in the field of wireless sensor networks. It includes the largest developers of hardware and software: Philips, Ember, Samsung, IBM, Motorola, Freescale Semiconductor, Texas Instruments, NEC, LG, OKI and many others (more than 200 members in total). Intel is not a member of the alliance, although it supports its activities.

In principle, to develop a standard, including a protocol stack for wireless sensor networks, ZigBee used the previously developed IEEE 802.15.4 standard, which describes the physical layer and the level of access to the medium for wireless data transmission networks over short distances (up to 75 m) with low power consumption, but with a high degree of reliability. Some characteristics of radio data transmission for the IEEE 802.15.4 standard are given in table. 1.

Table 1. IEEE 802.15.4 radio transmission characteristics

At the moment, ZigBee has developed the only standard in this area, which is supported by the production of fully compatible hardware and software products. ZigBee protocols allow devices to hibernate b aboutmost of the time, which significantly extends battery life.

It is obvious that it is not so easy to develop data exchange schemes between hundreds and even thousands of mots. Among other things, it is necessary to take into account the fact that sensor networks operate in unlicensed frequency ranges, therefore, in some cases, interference caused by extraneous sources of radio signals may occur. It is also advisable to avoid repeated transmission of the same data, and in addition, take into account that due to insufficient energy intensity and external influences, the motes will fail forever or for some time. In all such cases, the communication schemes must be modified. Since one of the most important features of TinyOS is the automatic selection of the network layout and data transmission routes, wireless sensor networks are essentially self-configuring.

Most often, a mote should be able to independently determine its location, at least in relation to the other mote to which it will transmit data. That is, first, all motes are identified, and then a routing scheme is formed. In general, all motes - devices of the ZigBee standard - are divided into three classes according to the level of complexity. The highest of them - the coordinator - manages the operation of the network, stores data about its topology and serves as a gateway for transmitting data collected by the entire wireless sensor network for further processing. Sensor networks usually use one coordinator. A moto of medium complexity is a router, that is, it can receive and transmit data, and also determine the direction of transmission. Finally, the simplest moto can only transmit data to the nearest router. Thus, it turns out that the ZigBee standard supports a network with a cluster architecture (Fig. 2). The cluster is formed by a router and the simplest motes from which it requests sensory data. Cluster routers relay data to each other, and ultimately the data is passed to the coordinator. The coordinator usually has a link to the IP network, where the data is sent for final processing.

In Russia, developments related to the creation of wireless sensor networks are also being carried out. Thus, the High-Tech Systems company offers its hardware and software platform MeshLogic for building wireless sensor networks (website www.meshlogic.ru). The main difference between this platform and ZigBee is its focus on building peer-to-peer mesh networks (Fig. 3). In such networks, the functionality of each mote is the same. The possibility of self-organization and self-healing of mesh topology networks allows, in the event of a part of the motes out of operation, to spontaneously form a new network structure. True, in any case, you need a central functional unit that receives and processes all the data, or a gateway to transfer data to the processing unit. Spontaneously created networks are often called the Latin term Ad Hoc, which means "for a specific case."

In MeshLogic networks, each mote can perform packet relay, which is similar in function to a ZigBee router. MeshLogic networks are completely self-organizing: no coordinator node is provided. Various devices can be used as radio frequency transceivers in MeshLogic, in particular Cypress WirelessUSB, which, like ZigBee devices, operate in the 2.4 ... 2.4835 GHz frequency range. It should be noted that only the lower layers of the protocol stack exist for the MeshLogic platform. It is believed that the upper levels, in particular the network and application, will be created for specific applications. The configurations and basic parameters of two MeshLogic motes and one ZigBee mote are shown in Table. 2.

Table 2. Main characteristics of mots from different manufacturers

Note that there are no integrated touch sensors on these boards.

Let's point out what first of all distinguishes wireless sensor networks from conventional computing (wired and wireless) networks:

• complete absence of any cables - electrical, communication, etc .;
• the possibility of compact placement or even integration of mots into environmental objects;
• reliability of both individual elements and, more importantly, the entire system as a whole; in some cases, the network can function if only 10-20% of the sensors (mots) are operational;
• no need for personnel for installation and maintenance.

Sensor networks can be used in many application areas. Wireless sensor networks are a promising new technology and all related projects are mostly under development. Let's indicate the main areas of application of this technology:

• defense systems and security;
• environmental control;
• monitoring of industrial equipment;
• security systems;
• monitoring of the state of agricultural land;
• power supply management;
• control of ventilation, air conditioning and lighting systems;
• fire alarm;
• inventory control;
• tracking cargo transportation;
• monitoring the physiological state of a person;
• personnel control.

From a fairly large number of examples of using wireless sensor networks, we will single out two. The most famous is perhaps the deployment of the network aboard a BP oil tanker. There, using a network built on the basis of Intel equipment, the condition of the vessel was monitored in order to organize its preventive maintenance. BP has analyzed whether the sensor network can operate on board ships in the extreme temperatures, high vibration, and significant levels of radio frequency interference found in some areas of the ship. The experiment was successful, several times were automatically reconfigured and restored to the network.

An example of another pilot project that has been implemented is the deployment of a sensor network at a US Air Force base in Florida. The system has demonstrated good ability to recognize various metal objects, including moving ones. The use of the sensor network made it possible to detect the penetration of people and cars into the controlled area and track their movements. To solve these problems, we used motes equipped with magnetoelectric and temperature sensors. Currently, the scope of the project is expanding, and a wireless sensor network is already being installed on a 10,000x500 m test site. The corresponding application software is being developed by several American universities.

History and scope of use

One of the first prototypes of the sensor network can be considered the SOSUS system, designed to detect and identify submarines. Technologies of wireless sensor networks began to develop actively relatively recently - in the mid-90s. However, only at the beginning of the XXI century, the development of microelectronics made it possible to produce a fairly cheap element base for such devices. Modern wireless networks are mainly based on the ZigBee standard. A considerable number of industries and market segments (manufacturing, various types of transport, life support, security), ready for the implementation of sensor networks, and this number is constantly increasing. The trend is due to the increasing complexity of technological processes, the development of production, the expanding needs of individuals in the segments of security, resource control and the use of inventory. With the development of semiconductor technologies, new practical problems and theoretical problems appear associated with the application of sensor networks in industry, housing and communal services, and households. The use of inexpensive wireless sensor devices for parameter control opens up new areas for telemetry and control systems, such as:

• Timely identification of possible failures of actuators, by monitoring parameters such as vibration, temperature, pressure, etc .;
• Access control in real time to remote systems of the monitoring object;
• Automation of inspection and maintenance of industrial assets;
• Commercial asset management;
• Application as components in energy and resource saving technologies;
• Control of eco-parameters of the environment.

It should be noted that despite the long history of sensor networks, the concept of building a sensor network has not finally taken shape and has not been expressed in certain software and hardware (platform) solutions. The implementation of sensor networks at the current stage largely depends on the specific requirements of the industrial task. The architecture, software and hardware implementation is at the stage of intensive formation of technology, which draws the attention of developers in order to find a technological niche for future manufacturers.

Technology

Wireless sensor networks (WSN) consist of miniature computing devices - mots equipped with sensors (sensors for temperature, pressure, illumination, vibration level, location, etc.) and signal transceivers operating in a given radio range. Flexible architecture, reduced installation costs, distinguish wireless networks of smart sensors from other wireless and wired data interfaces, especially when it comes to a large number of interconnected devices, the sensor network allows you to connect up to 65,000 devices. The constant decrease in the cost of wireless solutions, an increase in their operational parameters allow us to gradually reorient ourselves from wired solutions to systems for collecting telemetry data, means of remote diagnostics, and information exchange. The "sensory network" is today an established term (eng. Sensor Networks), denoting a distributed, self-organizing, resistant to failure of individual elements network of unattended devices that do not require special installation. Each node of the sensor network can contain various sensors for monitoring the external environment, a microcomputer and a radio transceiver. This allows the device to take measurements, independently carry out initial data processing and maintain communication with an external information system.

802.15.4 / ZigBee short-range relay technology known as Sensor Networks (eng. WSN - Wireless Sensor Network), is one of the modern trends in the development of self-organizing fault-tolerant distributed systems for monitoring and managing resources and processes. Today, wireless sensor network technology is the only wireless technology that can be used to solve monitoring and control tasks that are critical to the operating time of sensors. The sensors combined into a wireless sensor network form a geographically distributed self-organizing system for collecting, processing and transmitting information. The main field of application is control and monitoring of measured parameters of physical media and objects.

• radio path;
• processor module;
• battery;
• various sensors.

A typical node can be represented by three types of devices:

• Network Coordinator (FFD - Fully Function Device);
  • carries out global coordination, organization and setting of network parameters;
  • the most complex of the three device types, requiring the most memory and power supply;

• Fully Functional Device (FFD);
  • support for 802.15.4;
  • additional memory and power consumption allows you to act as a network coordinator;
  • support for all types of topologies ("point-to-point", "star", "tree", "mesh");
  • the ability to act as a network coordinator;
  • the ability to access other devices on the network;
• (RFD - Reduced Function Device);
  • supports a limited set of 802.15.4 features;
  • support for topologies "point-to-point", "star";
  • does not act as a coordinator;
  • contacts the network coordinator and router;

Developers companies

Companies of various types are represented on the market:

Notes

Wikimedia Foundation. 2010.

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