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Types of telecommunications. What are telecommunications and what do they consist of? What is not a means of telecommunication?

Telecommunications – communication at a distance (lat.)

Communication( the process of information exchange) is a necessary condition for the existence of living organisms, ecological communities and human society. Social development is accompanied by the development of telecommunications technologies. Telecommunication technologies have been developing especially intensively over the past few decades.

Telecommunications can be defined as technologies dealing with communication at a distance and this can be explained in various ways. Figure 8.2 shows one possible representation of the various sections of telecommunications.

Figure 8.2. Telecommunications: forms and types

Telecommunications are divided into two types: unidirectional and bidirectional. Unidirectional, such as mass radio and television broadcasting, involve the transmission of information in one direction - from the center to subscribers. Bidirectional supports dialogue between two subscribers.

Telecommunications use mechanical and electrical means because historically telecommunications have evolved from mechanical to electrical forms, using increasingly complex electrical systems. This is the reason why many traditional operators in telecommunications such as national postal, telegraph and telephone companies use both forms. The share of mechanical telecommunications such as mail and newspapers is expected to decrease, while the share of electrical, especially bidirectional, will increase and become dominant in the future. Already in our time, corporations and the press are interested, first of all, in electrical telecommunications (telecommunications) as a profitable business opportunity.

Along the edges of Figure 8.2. telecommunications services are shown, initially mechanical: press (newspaper forwarding), post office; then electrical: telegraph, telex (subscriber telegraph), telephone, radio, television, computer networks, leased networks, cable television and mobile telephone.

Telecommunications have historically developed approximately in this order.

Telecommunication system– a set of technical objects, organizational measures and subjects that implement processes consisting of: connection processes, transmission processes and access processes.

Telecommunication systems use natural or artificial environments to exchange information. Telecommunication systems, together with the medium that is used for transmission, form telecommunication networks. The most important telecommunication networks are (Fig. 8.2.): postal services; public telephone network (PSTN); mobile telephone networks; telegraph network; Internet – a global network of interaction of computer networks; wired radio broadcasting network; cable television networks; television and radio broadcasting networks; departmental communication networks that provide communication services to public service bodies, air and maritime traffic control systems, and large industrial complexes; global rescue and safety networks.

The telecommunication systems listed above, as a rule, closely interact with each other and use common resources to implement communications. To organize such interaction, in each state and on a global scale there are special bodies that regulate the use of common resources; determine the general rules of interaction (protocols) of telecommunication systems; developing promising telecommunications technologies.

To implement communication at a distance, telecommunication systems use: switching systems; transmission systems; access and control systems for transmission channels.

TELECOMMUNICATIONS

TELECOMMUNICATIONS, a set of technical means designed to transmit information over a distance. Information comes in a wide variety of forms: as digital signals, sounds, printed words or images. Transfer is carried out by means of TELEGRAPH, TELEPHONE and RADIO, by wire or RADIO WAVES; sometimes these methods are combined. The telegraph was developed in the mid-19th century, and radio appeared at the end of the century. TELEVISION originated in the 1930s. There are two main types of messages: DIGITAL SIGNALS, in which the message is converted into a series of coded pulses and then sent (as in MORSE CODE), and ANALOG SIGNALS, in which a message, such as voice speech, is directly converted into a series of transmitted electrical pulses, in a waveform. form similar to MODULATIONS of the original message. see also FAX, ARTIFICIAL SATELLITE.


Scientific and technical encyclopedic dictionary.

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Books

  • Computing systems, networks and telecommunications, Valery Pavlovich Shevchenko, A number of issues in the theory and practice of setting up and using computing information systems, networks and telecommunications are considered, including: the creation and research of virtual... Category: Networks and communications Series: Bachelor's degree Publisher: Knorus,
  • Telecommunications. World and Russia. State and development trends, Kleshchev T.N. , Some concepts of information theory and communication systems are presented. Issues of modern telecommunication technologies and modeling of telecommunication networks are covered. A brief overview is given... Category: Miscellaneous Publisher: RADIO AND COMMUNICATION, Manufacturer:

Telecommunication networks are divided into three main types according to their scale:

Local, referred to as Local Area Network (LAN). Subscribers are located at a short distance, up to ten (at most fifteen) kilometers from each other. The maximum is a WiMAX network with a transmitter on the roof of a tall building, serving a couple of city districts.

Regional, also known as the Metropolitan Area Network (MAN), they connect subscribers of a huge city or even a country. The most striking example is the cellular structure of a mobile operator's network.

Global, Wide Area Network (WAN) spans countries and continents. These are satellite communications, radio communications, telephone networks and, of course, the Internet.

The classification based on the principle of data transmission is as follows:

Serial networks, with relaying, when information moves from one node to another along the chain.

Broadcast networks without relaying, when one node (in computer systems - some kind of hub) sends something to all subscribers.

In practice, there are a lot of hybrid networks, branched, expanded and supplemented in various ways, depending on specific needs, so the classification is very arbitrary.

Trends

Telecommunications have long been part of the world of computer technology. Perhaps he will soon move into this world completely. Current trends are such that, apparently, the digitization of all telecommunications is coming in the near future.

With television, this process is already in full swing. More and more countries are introducing digital broadcasting, which will eventually completely replace analogue.

Along the way, the telecommunications industry makes money by selling digital set-top boxes for regular TVs, and also gets the opportunity to make most channels pay, as in satellite broadcasting.

It is likely that along with digitization will come total protection from copying, recording and distribution. All sorts of current DRM will seem like innocent pranks.

Conclusion

As you can see, the concept under discussion is too multifaceted to be able to cover the vastness within one article. If we try to formulate a more or less capacious definition, telecommunications is a complex industry that provides customers with different types of telecommunications, develops and implements innovations, creates, sells and uses equipment, and empties the wallets of citizens in various ways.

It is impossible to do without it in the civilized world, so you have to endure what you have: harmful radiation from numerous transmitters, tariffs, dubious quality and honesty of work. But, on the other hand, no one promised us that we would live in an ideal world.

Previous publications:

Currently, the management process cannot be imagined without the prompt exchange of various information. The current level of development of communications provides ample opportunities for organizing such information interaction.

By a telecommunications system we mean a set of means and communication channels that operate according to certain inherent principles (physical, organizational, technological, etc.) and are intended for transmitting information over long distances.

The following types of telecommunication systems are available:

  • telegraph communication;
  • telephone communications;
  • radio communication;
  • satellite connection;
  • computer networks.

Telegraph communication can rightfully be considered one of the oldest methods of transmitting information by technical means over long distances. Appeared at the beginning of the 19th century. The electrical telegraph system is still used to transmit data today. However, at present, telegraph communication is being replaced by other more modern, convenient and high-speed information exchange systems.

The invention of the telephone in 1876 marked the beginning of the development of telephone networks, which continue to improve to this day.

Nowadays, not only voice information (when two subscribers are talking), but also fax messages and digital data are transmitted through the public telephone network.

Generally speaking, telephone networks are designed to carry analog signals. The analog signal is continuous and can take values ​​over a certain range. For example, an analog signal is human speech; In a telephone, television, or radio, information also exists in analog form. The disadvantage of this form of information presentation is its susceptibility to interference.

The digital form of information representation is characterized by the presence of only two specific values. In a computer, information is encoded with two values: “1” - the presence of an electrical signal, “0” - its absence.

In order to transmit digital information using telephone communication channels, which is necessary, for example, for organizing computer networks, special devices must be used to convert signals of one type into another. Such devices are modems (modulators/demodulators), which allow you to convert a digital signal coming from a computer into an analog signal for transmitting it over telephone communication lines. On the receiving side, inverse transformations are performed.

Thus, telephone networks are the basis for building another type of telecommunications systems - computer networks.


Another direction in the development of telephone communication also arose at the junction of two different methods of data transmission: telephone communication itself and radio communication. This is how mobile telephone networks, also called “cellular” communications, emerged. This name arose in connection with some features of the organization of such communication networks. A cellular network is a system consisting of a large number of transmitters, each of them covering a certain limited area of ​​the entire communication zone - a “cell”.

Moving within the network, the subscriber enters the operating area of ​​one transmitter and then another, while the connection is not interrupted and the subscriber himself does not have to make any switching. It should also be noted that cellular communication systems can use and sections of the public telephone network, and satellite communications, etc. These channels are used for communication between various transmitting nodes of the network, while a radio channel is used to communicate between the end subscriber and the transmitter closest to him.

Modern mobile phones are convenient multifunctional devices. They not only allow you to communicate with another subscriber from almost anywhere in the world, but also have a lot of other useful features. Thus, using a mobile phone you can access the Internet and send text messages (SMS).

Radio communications in the activities of most organizations are rarely used directly to transmit information between two end subscribers. However, radio communication channels are an important component of computer networks - primarily the Internet and long-distance corporate networks.

Satellite communication systems have currently undergone great development. New satellite networks are constantly emerging. They are used as a data transmission channel in other communication systems (for example, when building global computer networks). Satellite systems are also widely used in organizing television broadcasting.

Satellite communication networks are built on the basis of three types of artificial satellites. These types differ in the type of orbit and the altitude at which the satellite is located. Thus, a distinction is made between satellites in low circular orbits (low-flying satellites); in elliptical orbits and geostationary satellites.

Low-flying satellites have an orbital altitude of no more than 2000 km. Since one such satellite is above a certain point on the Earth for a very short time, several dozen similar satellites are needed to ensure constant communication. When one of them leaves the reception zone, communication is carried out through the next satellite located in this zone. At any given time, there are two or three satellites in the “line of sight” zone.

Satellite communication systems in elliptical orbits allow radio and television broadcasting throughout Russia. The typical orbit of such satellites is an ellipse with the shortest distance to the Earth's surface being about 400-600 km and the greatest distance being up to 60,000 km. These satellites make it possible to provide communications over large areas. However, due to the elliptical orbit, they leave the hanging zone at a certain time, and communication with the satellites at this point in time is not carried out. When a satellite appears in the reception area, communication is restored.

Satellites in geostationary orbits allow stable communication with almost any point on the globe (except for areas close to the poles). To build such a system, three satellites are sufficient, which are located above the equator at an altitude of about 36,000 km and at each moment of time “hang” above a certain point on the Earth. However, the high orbit altitude allows such a satellite system to view almost the entire surface of the Earth. They do not cover only areas close to the poles (due to the curvature of the Earth).

Satellite communication systems are rarely used for direct communication between two network subscribers. Usually they are an intermediate link for the transmission of information that reaches the end user through other telecommunication networks (telephone, television, computer, etc.).

The main means of telecommunication, i.e., organizing information exchange, for modern enterprises are computer networks.

This type of telecommunications is currently experiencing a period of rapid development and growth. Nowadays, every reputable organization has its own local computer network, usually with Internet access.

In this regard, it is necessary to pay special attention to the consideration of issues of organization, construction and use of various computer networks.

Most often, networks are classified in terms of the territory they cover. It is on this basis that networks are divided into local and global.

Local networks(Local Area Network - LAN) consist of computers concentrated in a small area and, as a rule, belonging to one organization. Due to the fact that the distances between individual computers are small, there are ample opportunities for using expensive telecommunications equipment, which ensures high speed and quality of data transfer. Thanks to this, local network users can use a wide range of services. In addition, local networks, as a rule, use simple methods of interaction between individual computers on the network.

Global networks(Wide Area Network - WAN) consist of a large number of computer nodes located in different cities, regions, and countries. To create global networks, existing communication lines are usually used. This can significantly reduce the cost, since there is no need to lay special communication lines over long distances. In addition, this approach makes global networks accessible to a huge number of users.

However, the principle of using public communication systems also has significant drawbacks. Low speeds of the channels used significantly narrow the range of services offered. For stable data transmission over low-quality communication lines, special methods and means are used (in particular, complex procedures for monitoring integrity and data recovery). Such methods are the hallmarks of global networks.

The basis of the global network is made up of high-power computing systems designed for the simultaneous operation of many users - the so-called host nodes. Special computers - communication nodes - are also a necessary component of global networks.

City (regional) networks (Metropolitan Area Network - MAN) are designed to connect local networks within a single city, as well as connect local networks to global ones. Urban networks represent a kind of intermediate link between high-speed, but geographically limited local networks and long-distance, but low-speed global networks. The use of city networks will allow organizations to obtain high-quality and high-speed communications for much less money than when creating their own local network. In Russia, computer networks of this type have not yet become widespread.

Separately, we should highlight the so-called corporate networks. They are organized by enterprises that have a large number of branches located far from each other, between which it is necessary to organize rapid data exchange. Such networks are created for the own needs of a particular organization and to perform tasks within the framework of its activities. At the same time, the network itself is virtual, and direct data transmission is carried out through other networks: the public telephone network, local networks of the organization and its branches, the Internet, etc.

The telecommunications market is one of the most promising and rapidly growing areas of the communications industry. Currently, the telecommunications system is on the path of rapid development, generally focused on the entry of the Russian communication system into the world one as an equal partner for the provision of international, long-distance, city communication services, data transmission, Internet, mobile communications, etc.

What is telecommunication

The term "telecommunications" comes from the Latin communico, which means "form of communication", and the Greek tele, which means "operating over a long distance".

So, we can say that:

  • Telecommunications is a set of devices and programs that allow the transmission of information via cable and radio channels. These are devices for converting information, decoding it, and modern computer processing technologies.
  • Telecommunications means are a set of technical, software and organizational means for transmitting data over long distances. Solid-state output amplifiers are used to create satellite station transmitters.
  • Telecommunications are technical services that provide the transmission and reception of messages. Telecommunications specialists are technicians and engineers. They mainly work with codes, signals, noise.
  • Telecommunication is the exchange of any information using a computer. Information is transmitted through or exchange of information.
  • Telecommunication is the process of receiving and processing information using electronic, network, electromagnetic, information and computer technologies.

Promising areas of telecommunications technologies should be considered:

  1. Creation of new signal-code structures by using combined methods of signal manipulation and new signal coding methods in order to increase the capacity of transmission systems and improve their energy.
  2. Creation of smart antenna devices with improved energy.
  3. Creation of telecommunication systems in millimeter wave with an operating frequency of about 100 GHz.
  4. Development of design methods and production technology for telecommunications equipment, which ensures their optimal characteristics according to general criteria: minimum cost, maximum parameters, maximum reliability, minimum weight and size characteristics.
  5. Increasing the level of student education in the field of "Telecommunications", expansion and development in the field.

Technological method of signal encoding

To ensure optimal energy, the systems use the latest signal coding and modulation methods. It is the signal coding methods for combating errors in the presence of interference that provide energy gains in the system of up to 6-8 dB, even despite the expansion of the signal spectrum. In this case, block codes are used: Hamming, Reed-Solomon, BCH codes, as well as tree convolutional codes. It should be considered interesting to use codes that make it possible to implement triangular amplitude-phase keying and thus obtain additional energy gain in order to increase the signal transmission speed. In this case, the channel bandwidths use multi-position relative phase shift keying and quadrature amplitude-phase shift keying.

Satellite connection

Satellite communication systems are used in geostationary satellites to transmit television programs, including to individual receivers, and provide group information traffic. Of particular note is the international maritime satellite navigation system Inmarsat, which, in addition, has received widespread commercial use for operational communications and navigation using the GPS navigation satellite system in hard-to-reach areas, in emergency situations, as well as for monitoring cargo transportation. Small-sized ensures data transfer from anywhere in the world. In combination with a broadband pseudonoise signal, new technologies were implemented: a frequency microstrip antenna, a solid-state power amplifier, a two-channel filter on surface acoustic waves based on bismuth germanate, narrowband microwave filters on dielectric resonators, etc.

Telecommunications and communications

Today, mobile communication systems have developed particularly rapidly, the number of subscribers in most countries exceeding the number of subscribers of landline networks. So far, the leadership in the mobile communications market is held by the GSM-900/180 standard, the systems of which have reached the limit of perfection thanks to the use of the latest GPRS and EDGE technologies. CDMA mobile communication systems, which have unsurpassed confidentiality and energy performance, should be considered very promising. Today, to create a 3G mobile communication system in accordance with the MT-2000 standard developed by the International Telecommunications Union, three standards based on CDMA technology are used: CDMA ONE, CDMA 2000 and WCDMA. As part of the implementation of the IMT-2000 standard, work is being carried out to create satellite systems for personal mobile communications Orbocomm, Thuraya, Clobal Star, Iridium. So far, commercial operation of the systems has not been achieved due to problems of project financing and technical difficulties. The DECT radio system has proven itself well for creating enterprise information networks.

Fast signal transmission systems

Thanks to the achievements of microelectronics technologies, modern mobile and computer networks and telecommunications, such as Bluetooth, ZigBee, WiMax, WiFi, etc., are manufactured and used. In practice, exotic transmission systems are used, which are created using general principles and construction schemes and are distinguished by channel adapters for connection to the appropriate signal transmission channels. Hydroacoustic communication systems communicate underwater using ultrasonic vibrations at 8-20 kHz at a distance of up to 4 km. Laser communication systems use lasers with a wavelength of 1-10 microns and are used in space communication lines. The Ryazan Instrument-Making Plant (Russia) produces a laser transceiver device that provides signal transmission at a speed of about 200 Mbit/s over a distance of 2-10 km in terrestrial conditions and is used, for example, to transfer information between mobile communication systems. Communication systems in tunnels and subways use radio-emitting ones, for example, from EUPEN, in the frequency range 30-1800 MHz. US scientists have established the possibility of transmitting radio waves of a hectameter range in the bowels of the Earth. It is believed that by placing repeaters at a distance of up to 200 m, it is possible to create a communication line to transmit a signal with a spectrum of about 500 Hz.