How the telephone communication is carried out. mobile connection

The most widespread type of mobile communication today is cellular communication. Cellular services are provided to subscribers by operator companies.

Wireless communication to a cell phone is provided by a network of base stations.

Each station provides access to the network in a limited area, the area and configuration of which depends on the terrain and other parameters. Overlapping coverage areas create a honeycomb-like structure; from this image the term "cellular communication" comes from. When a subscriber moves, his phone is served by one or another base station, and the switching (cell change) occurs automatically, completely invisible to the subscriber, and does not affect the quality of communication in any way. This approach allows, using low-power radio signals, to cover large areas with a mobile network, which provides this type of communication, in addition to efficiency, also a high level of environmental friendliness.

The operator company not only provides technical support for mobile communications, but also enters into economic relations with subscribers who purchase a certain set of basic and additional services from it. Since there are a lot of types of services, the prices for them are combined into sets, called tariff plans. The billing system (software and hardware system that keeps records of the services and services provided to the subscriber) is responsible for calculating the cost of services rendered to each subscriber.

The operator's billing system interacts with similar systems of other companies, for example, providing a subscriber with roaming services (the ability to use mobile communications in other cities and countries). All settlements for mobile communications, including roaming, are made by the subscriber with his operator, which is a single settlement center for him.

Roaming - access to mobile services outside the coverage area of ​​the "home" operator's network with which the subscriber has a contract.

While in roaming, the subscriber usually keeps his phone number, continues to use his cell phone, making and receiving calls in the same way as in the home network. All the actions necessary for this, including the inter-operator traffic exchange and the attraction of the resources of other communication companies (for example, those providing transcontinental communications) as needed, are performed automatically and do not require additional actions from the subscriber. If the home and guest networks provide communication services in different standards, roaming is still possible: the subscriber can be given another device during the trip, while keeping his phone number and automatically routing calls.

The history of cellular communications.

Work on the creation of civilian mobile communication systems began in the 1970s. By this time, the development of conventional telephone networks in European countries had reached such a level that the next step in the evolution of communications could only be the availability of telephone communications everywhere and everywhere.

Networks based on the first civilian cellular standard, NMT-450, appeared in 1981. Although the name of the standard is an abbreviation for Nordic Mobile Telephony, the world's first cellular network was deployed in Saudi Arabia. In Sweden, Norway, Finland (and other Nordic countries), NMT networks went live a few months later.

Two years later, in 1983, the first AMPS (Advanced Mobile Phone Service) standard network, created at the Bell Laboratories research center, was launched in the United States.

NMT and AMPS standards, which are usually attributed to the first generation of cellular communication systems, provided for the transmission of data in analog form, which did not allow to provide the proper level of noise immunity and protection from unauthorized connections. Subsequently, they have improved modifications through the use of digital technologies, for example, DAMPS (the first letter of the abbreviation owes its appearance to the word Digital - "digital").

The standards of the second generation (the so-called 2G) - GSM, IS-95, IMT-MC-450, etc., originally created on the basis of digital technologies, exceeded the standards of the first generation in sound quality and security, and also, as it turned out later, in terms of to the standard of development potential.

Already in 1982 the European Conference of Post and Telecommunication Administrations (CEPT) set up a group to develop a unified standard for digital cellular communications. The brainchild of this group is GSM (Global System for Mobile Communications).

The first GSM network was launched in Germany in 1992. Today GSM is the dominant cellular standard both in Russia and around the world. In 2004, over 90% of cellular subscribers in our country served GSM-networks; in the world GSM was used by 72% of subscribers.

For the operation of equipment of the GSM standard, several frequency ranges are allocated - they are indicated by the numbers in the names. In the European region, GSM 900 and GSM 1800 are mainly used, in America - GSM 950 and GSM 1900 (at the time of the approval of the standard in the USA, “European” frequencies were occupied by other services there).

The popularity of the GSM standard was ensured by its significant features for subscribers:

- immunity from interference, interception and "doubles";

- the presence of a large number of additional services;

- the ability, in the presence of "add-ons" (such as GPRS, EDGE, etc.) to provide data transmission at high speeds;

- presence on the market of a large number of telephones operating in GSM networks;

- simplicity of the procedure for changing one device to another.

In the process of development, cellular networks of the GSM standard have acquired the possibility of expansion due to some "add-ons" over the existing infrastructure, providing high-speed data transmission. GSM networks supporting GPRS (General Packet Radio Service) are called 2.5G, and GSM networks supporting EDGE (Enhanced Data rates for Global Evolution) are sometimes called 2.75G networks.

In the late 1990s, third generation (3G) networks emerged in Japan and South Korea. The main difference between the standards on which the 3G networks are built from their predecessors is the expanded capabilities of high-speed data transmission, which makes it possible to implement new services in such networks, in particular, video telephony. In 2002-2003, the first commercial 3G networks began to operate in some countries of Western Europe.

Although at present 3G networks exist only in a number of regions of the world, in the engineering laboratories of the largest companies work is already underway to create fourth-generation cellular communication standards. In this case, the cornerstone is not only a further increase in the data transfer rate, but also an increase in the efficiency of using the bandwidth of the frequency ranges allocated for mobile communications, so that a large number of subscribers located in a limited area could access the services (which is especially important for megalopolises) ...

Other mobile communication systems.

In addition to cellular communication, today there are other civil communication systems that also provide mobile communication via radio channels, but built on different technical principles and focused on other subscriber terminals. They are less common than cellular communications, but find use when using cell phones is difficult, impossible, or economically unprofitable.

The DECT microcellular standard is becoming more and more popular, which is used for communications in a limited area. The base station of the DECT standard is capable of providing handsets (up to 8 of them can be served simultaneously) to communicate with each other, forward calls, as well as access to the public telephone network. The potential of the DECT standard makes it possible to provide mobile communications within urban neighborhoods, individual companies or apartments. They turn out to be optimal in regions with low-rise buildings, whose subscribers only need voice communication and can do without mobile data transmission and other additional services.

In satellite telephony, base stations are located on satellites in low-earth orbits. Satellites provide communication where the deployment of a conventional cellular network is impossible or unprofitable (at sea, in vast sparsely populated areas of tundra, deserts, etc.).

Trunking networks that provide subscriber terminals (they are usually called not telephones, but radio stations) communication within a certain territory are systems of base stations (repeaters) that transmit radio signals from one terminal to another at a significant distance from each other. Since trunking networks usually provide communication to employees of departments (Ministry of Internal Affairs, Ministry of Emergency Situations, Ambulance, etc.) or at large technological sites (along highways, at a construction site, on the territory of factories, etc.), trunking terminals do not have entertainment options and design delights in decoration.

Wearable radios communicate directly with each other without intermediate communication systems. This type of mobile communication is preferred by both state (police, fire brigade, etc.) and departmental structures (for communications within a warehouse complex, parking or construction site), and individuals (mushroom pickers, hunter-fishermen or tourists), in situations when it is easier and cheaper to use pocket radios for communication with each other than cell phones (for example, in remote areas where there is no cellular coverage).

Paging communication provides receipt of short messages to subscriber terminals - pagers. Currently, paging communications in civil communications are practically not used; due to their limitations, they have been pushed into the area of ​​highly specialized solutions (for example, they serve to notify personnel in large medical institutions, transfer data to electronic information boards, etc.).

Since 2004, a new subtype of mobile communication has become more and more widespread, providing the possibility of high-speed data transmission over a radio channel (in most cases, the Wi-Fi protocol is used for this). Areas with Wi-Fi coverage available for public use (paid or free) are called hotspots. In this case, subscriber terminals are computers - both laptops and PDAs. They can also provide two-way voice communication over the Internet, but this opportunity is used extremely rarely, mainly the connection is used to access the most common Internet services - e-mail, websites, instant messaging systems (for example, ICQ), etc. ...

Where mobile communications are heading.

In developed regions, the main direction of development of mobile communications for the near future is convergence: providing subscriber terminals with automatic switching from one network to another in order to make the most efficient use of the capabilities of all communication systems. Automatic switching, for example, from GSM to DECT (and vice versa), from satellite to terrestrial communication, will allow saving subscribers' funds and improving the quality of communication, and when providing wireless data transmission - between GPRS, EDGE, Wi-Fi and other standards, many of which (for example, WiMAX) are just waiting in the wings.

The place of mobile communications in the global economy.

Communications is the most dynamically developing branch of the world economy. But mobile communications, even in comparison with other areas of "telecom", are developing at a faster pace.

Back in 2003, the total number of mobile phones on the planet exceeded the number of stationary devices connected to public wired networks. In some countries, the number of mobile subscribers already in 2004 exceeded the number of inhabitants. This means that some people have used more than one “mobile” —for example, two cell phones with different carriers, or a voice phone and a wireless modem for mobile Internet access. In addition, more and more wireless modules were required to provide technological communications (in these cases, the subscribers are not people, but specialized computers).

Currently, mobile operators provide full coverage of the territory of all economically developed regions of the planet, but the extensive development of networks continues. New base stations are installed to improve reception in those places where the existing network for some reason cannot provide stable reception (for example, in long tunnels, on the territory of the subway, etc.). In addition, cellular networks are gradually penetrating regions with low incomes of the population. The development of mobile communication technologies, accompanied by a sharp reduction in the cost of equipment and services, makes cellular services available to an increasing number of people on the planet.

Cell phone manufacturing is one of the fastest growing areas of the high technology industry.

The mobile phone service industry is also growing rapidly, offering accessories for personalizing devices: from original bells (ringtones) to key fobs, graphic screensavers, body stickers, replaceable panels, covers and laces for carrying the device.

Types of telephones.

Cellular (mobile) telephone - a subscriber terminal operating in a cellular network. In fact, each cell phone is a specialized computer that is primarily focused on providing (in the coverage area of ​​a home or guest network) voice communication of subscribers, but also supports text and multimedia messaging, is equipped with a modem and a simplified interface. Modern mobile phones provide voice and data transmission in digital form.

The previously existing division of devices into “inexpensive”, “functional”, “business” and “fashion” models is losing its meaning more and more - business devices acquire the features of fashion models and entertainment functions, as a result of the use of accessories, inexpensive phones become fashion functionality is growing rapidly.

The miniaturization of pipes, which peaked in 1999–2000, was completed for quite objective reasons: the devices reached their optimal size, their further reduction makes it inconvenient to press buttons, read text on the screen, etc. But the cell phone has become a real piece of art: leading designers are attracted to the development of the appearance of the devices, and the owners are given ample opportunities to personalize their devices on their own.

Currently, manufacturers pay special attention to the functionality of mobile phones, both the main one (longer battery life, improved screens, etc.) and their additional capabilities (digital cameras, voice recorders, MP3 players and other "related "Device).

Almost all modern devices, with the exception of some models in the lower price range, allow downloading programs. Most devices can run Java applications, the number of phones using operating systems inherited from PDAs or ported from them is increasing: Symbian, Windows Mobile for Smartphones, etc. Phones with built-in operating systems are called smartphones (from a combination of the English words "smart" and "phone" - "smart phone").

Communicators - pocket computers equipped with a module supporting GSM / GPRS, and sometimes EDGE and third generation standards - can also be used today as subscriber terminals.

Non-voice services of cellular networks.

A number of non-voice services are available to subscribers of cellular networks, the “assortment” of which depends on the capabilities of a particular phone and on the range of offers of the operator. The list of services in the home network may differ from the list of services available in roaming.

Services can be communication (providing various forms of communication with other people), informational (for example, reporting the weather forecast or market quotes), providing Internet access, commercial (for paying for various goods and services from phones), entertainment (mobile games, quizzes , casinos and lotteries) and others (this includes, for example, mobile positioning). Today, more and more services appear at the interface, for example, most games and lotteries are paid, games that use mobile positioning technologies appear, and so on.

Almost all operators and most modern devices support the following services:

- SMS - Short Message Service - transfer of short text messages;

- MMS - Multimedia Messaging Service - transfer of multimedia messages: photos, videos, etc .;

- automatic roaming;

- determination of the number of the calling subscriber;

- ordering and receiving various means of personification directly through cellular communication channels;

- Internet access and viewing of specialized (WAP) sites;

- download ringtones, pictures, information materials from specialized resources;

- data transmission using the built-in modem (it can be carried out using various protocols, depending on what technologies a particular device supports).

Mobile communications in Russia.

There were no civilian mobile communication systems in the USSR. With some stretch of the imagination, the Altai mobile telephony system, based on the MRT-1327 standard, which was created at the turn of the 1970s-1980s to provide communication between representatives of the party, state and economic leaders, can be called the Altai mobile telephony system. Altai is successfully operated to this day. Of course, it cannot compete with cellular networks, but it finds application for solving some highly specialized tasks: providing communication for mobile units of city emergency services, providing telephones for summer cafes, etc.

The first commercial cellular networks built according to the NMT standard were created in Russia in the fall of 1991. The pioneers of mobile telephony in our country were Delta Telecom (St. Petersburg) and Moscow Cellular Communications. The first cell phone call was made on September 9, 1991 in St. Petersburg: Anatoly Sobchak, who was then the mayor of the city, called his colleague, the mayor of New York.

In July 1992, the first calls were made to the Beeline AMPS network.

The first Russian GSM network, created by MTS, began connecting subscribers in July 1994.

In 2005, there are three federal cellular operators in Russia providing services in the GSM standard: MTS, Beeline and MegaFon. The range and quality of telecommunication services they offer, as well as their prices, are approximately the same. By 2005, the number of base stations in the networks of the leading metropolitan operators in Moscow and the nearest Moscow region was about 3000, and the coverage area exceeded the area of ​​most European countries. In addition to them, there are numerous local operators that operate quite effectively - both subsidiaries of the Big Three and independent companies.

Operators are actively developing the market, increasing the coverage of their networks and popularizing mobile communications among various segments of the population. If in the mid-1990s a cell phone was available only to representatives of the wealthiest strata of the population, today almost everyone can use mobile communications. Russian operators implement the latest services in their networks and offer services built on their basis, often even outstripping most European companies. Currently, all three federal GSM-operators are preparing for the deployment of commercial third-generation networks.

In addition to GSM networks of federal and local cellular operators, networks of other standards continue to operate in Russia: DAMPS, IS-95, NMT-450, DECT and IMT-MC-450. The latter standard has federal status, and networks built on its basis (for example, SkyLink) are developing very actively. However, neither in terms of coverage, nor in terms of the number of subscribers served by networks of all standards other than GSM, they cannot create significant competition for the leading three federal operators.

Literature:

Malyarevsky A., Olevskaya N. Your mobile phone(popular tutorial). M, "Peter", 2004
Zakirov Z.G., Nadeev A.F., Faizullin R.R. Cellular communication of the GSM standard. State of the art, transition to third generation networks("MTS Library"). M., "Eco-Trends", 2004
Popov V.I. GSM Cellular Basics("The Engineering Encyclopedia of the Fuel and Energy Complex"). M., "Eco-Trends", 2005



Mobile cellular communication

cellular- one of the types of mobile radio communications, which is based on cellular network... The key feature is that the total coverage area is divided into cells (cells), determined by the coverage areas of individual base stations (BS). The honeycombs overlap partially and together form a network. On an ideal (even and without building) surface, the coverage area of ​​one BS is a circle, therefore, the network composed of them looks like honeycombs with hexagonal cells (honeycombs).

It is noteworthy that in the English version the communication is called "cellular" or "cellular" (cellular), which does not take into account the hexagonal nature of the honeycomb.

The network consists of spaced-apart transceivers operating in the same frequency range, and switching equipment that allows determining the current location of mobile subscribers and ensuring continuity of communication when a subscriber moves from the coverage area of ​​one transceiver to the coverage area of ​​another.

Story

The first use of mobile telephony in the United States dates back to 1921: Detroit police used one-way dispatch in the 2 MHz band to transmit information from a central transmitter to vehicle-mounted receivers. In 1933, the New York police began using a two-way mobile telephone radio system, also in the 2 MHz band. In 1934, the US Federal Communications Commission allocated 4 channels for telephone radio communications in the range of 30 ... 40 MHz, and in 1940, about 10 thousand police vehicles were already using telephone radio communications. All of these systems used amplitude modulation. Frequency modulation began to be used in 1940 and by 1946 completely replaced amplitude modulation. The first public mobile radiotelephone appeared in 1946 (St. Louis, USA; Bell Telephone Laboratories) using the 150 MHz band. In 1955, an 11-channel system began operating in the 150 MHz range, and in 1956 - a 12-channel system in the 450 MHz range. Both of these systems were simplex and used manual switching. Automatic duplex systems began operating in 1964 (150 MHz) and 1969 (450 MHz), respectively.

In the USSR In 1957, a Moscow engineer L. I. Kupriyanovich created a prototype of a portable automatic duplex mobile radiotelephone LK-1 and a base station for it. The mobile radiotelephone weighed about three kilograms and had a range of 20-30 km. In 1958, Kupriyanovich created improved models of the apparatus weighing 0.5 kg and the size of a cigarette box. In the 60s Hristo Bochvarov in Bulgaria demonstrates his prototype of a pocket mobile radiotelephone. At the Interorgtechnika-66 exhibition, Bulgaria presents a set for organizing local mobile communications from pocket mobile phones RAT-0.5 and ATRT-0.5 and a base station RATTs-10, which provides connection of 10 subscribers.

At the end of the 50s, the development of the Altai automobile radiotelephone system began in the USSR, which was put into trial operation in 1963. The Altai system initially operated at a frequency of 150 MHz. In 1970 the Altai system operated in 30 cities of the USSR and a 330 MHz band was allocated for it.

Similarly, with natural differences and on a smaller scale, the situation has developed in other countries. Thus, in Norway, public telephone radio communications have been used as maritime mobile communications since 1931; in 1955 there were 27 coastal radio stations in the country. Terrestrial mobile communications began to develop after the Second World War in the form of hand-switched private networks. Thus, by 1970, mobile telephone radio communication, on the one hand, had already become quite widespread, but on the other hand, it clearly did not keep up with the rapidly growing needs, with a limited number of channels in strictly defined frequency bands. A solution was found in the form of a cellular communication system, which made it possible to dramatically increase capacity by reusing frequencies in a cellular system.

Of course, as is usually the case in life, individual elements of the cellular communication system existed before. In particular, some semblance of a cellular system was used in 1949 in Detroit (USA) by a taxi dispatch service - with the reuse of frequencies in different cells with manual channel switching by users at predetermined locations. However, the architecture of the system that is today known as the cellular communication system was outlined only in the technical report of the Bell System company submitted to the US FCC in December 1971. And from that time the development of cellular communication itself begins, which has become truly triumphant since 1985 g., in the last ten years and a little.

In 1974, the FCC decided to allocate a 40 MHz frequency band for cellular communications in the 800 MHz range; in 1986, another 10 MHz was added to it in the same range. In 1978, tests of the first prototype cellular communication system for 2,000 subscribers began in Chicago. Therefore, 1978 can be considered the year of the beginning of the practical application of cellular communications. The first automatic commercial cellular system was also commissioned in Chicago in October 1983 by American Telephone and Telegraph (AT&T). In Canada, cellular communication has been used since 1978, in Japan - since 1979, in the Scandinavian countries (Denmark, Norway, Sweden, Finland) - since 1981, in Spain and England - since 1982. As of July 1997 g. cellular communication operated in more than 140 countries of all continents, serving more than 150 million subscribers.

The first commercially successful cellular network was the Finnish Autoradiopuhelin (ARP) network. This name is translated into Russian as "Car radiotelephone". Launched in the city, it has reached 100% coverage of the territory of Finland c. The cell size was about 30 km, and in the city there were more than 30 thousand subscribers. She worked at a frequency of 150 MHz.

The principle of cellular communication

The main components of a cellular network are cell phones and base stations... Base stations are usually located on rooftops and towers. When turned on, the cell phone listens to the air, finding a signal from the base station. The telephone then sends its unique identification code to the station. The telephone and the station maintain constant radio contact, periodically exchanging packets. The phone can communicate with the station using an analog protocol (NMT-450) or digital (DAMPS, GSM, eng. handover).

Cellular networks can consist of base stations of different standards, which allows you to optimize network performance and improve its coverage.

Cellular networks of different operators are connected to each other, as well as to the landline telephone network. This allows subscribers of one operator to make calls to subscribers of another operator, from mobile phones to landlines and from landlines to mobiles.

Operators from different countries can conclude roaming agreements. Thanks to such agreements, a subscriber, while abroad, can make and receive calls through the network of another operator (albeit at higher rates).

Cellular communication in Russia

In Russia, cellular communication began to be introduced in 1990, commercial use began on September 9, 1991, when the first cellular network in Russia was launched in St. Petersburg by Delta Telecom (it worked in the NMT-450 standard) and the first a symbolic call by the mayor of St. Petersburg, Anatoly Sobchak. By July 1997, the total number of subscribers in Russia was about 300 thousand. For 2007, the main cellular communication protocols used in Russia are GSM-900 and GSM-1800. In addition, UMTS works. In particular, the first fragment of the network of this standard in Russia was put into operation on October 2, 2007 in St. Petersburg by the MegaFon company. The Sverdlovsk Region continues to operate a DAMPS cellular network owned by the MOTIV Cellular Communications Company.

In December 2008, there were 187.8 million mobile users in Russia (based on the number of SIM cards sold). The penetration rate of cellular communications (the number of SIM-cards per 100 inhabitants) as of this date amounted to 129.4%. In the regions, excluding Moscow, the penetration rate exceeded 119.7%.

The market share of the largest cellular operators as of December 2008 was 34.4% for MTS, 25.4% for VimpelCom and 23.0% for MegaFon.

In December 2007, the number of cellular users in Russia increased to 172.87 million subscribers, in Moscow - up to 29.9, in St. Petersburg - up to 9.7 million.The penetration rate in Russia - up to 119.1%, in Moscow - 176% , St. Petersburg - 153%. The market share of the largest cellular operators as of December 2007 was: MTS 30.9%, VimpelCom 29.2%, MegaFon 19.9%, other operators 20%.

According to the British research company Informa Telecoms & Media for 2006, the average cost of a minute of cellular communication for a consumer in Russia was $ 0.05 - this is the lowest figure among the G8 countries.

IDC, based on a study of the Russian cellular market, concluded that in 2005 the total duration of conversations on a cell phone of residents of the Russian Federation reached 155 billion minutes, and 15 billion text messages were sent.

According to a study by J "son & Partners, the number of SIM cards registered in Russia as of the end of November 2008 reached 183.8 million.

see also

Sources of

Links

• Information site about generations and standards of cellular communication.
• Cellular communications in Russia 2002-2007, official statistics

cellular in Russia
Cellular operators	Utel Akos Altaysvyaz Baikalwestcom Beeline ETK MegaFon Motive MTS NSS NTK SMARTS Sky Link Sonnet Sotel SSB STEC GSM TomskTeleCom UUSS Digital expansion
Cell phone sales networks	Divizion Simphony AltTelecom Banzai Betalink Euroset ION Communication Spectrum Telefon.Ru Teleforum Point Ultra Tsifrograd Eldorado
Cellular standards	D-AMPS GSM IMT-MC-450 IS-95

Telephony is the transmission of voice information over long distances. With the help of telephony, people are able to communicate in real time.

If at the time of the emergence of technology there was only one method of data transmission - analog, then at the moment a variety of communication systems are successfully used. Telephone, satellite and mobile communications, as well as IP-telephony provide reliable contact between subscribers, even if they are in different parts of the world. How does telephony work with each method?

Good old wired (analog) telephony

The term "telephone" communication is most often understood as analog communication, a method of data transmission that has become familiar for nearly a century and a half. When using such, information is transmitted continuously, without intermediate encoding.

The connection of two subscribers is regulated by dialing a number, and then communication is carried out by transmitting a signal from person to person over wires in the most literal sense of the word. Subscribers are no longer connected by telephone operators, but by robots, which greatly simplified and made the process cheaper, but the principle of operation of analog communication networks remained the same.

Mobile (cellular) communication

Subscribers of mobile operators mistakenly believe that they have “cut the wire” connecting them to telephone exchanges. It looks like it is - a person can move anywhere (within the signal coverage) without interrupting the conversation and without losing contact with the interlocutor, and<подключить телефонную связь стало легче и проще.

However, if we look at how mobile communication works, we find not so many differences from the work of analog networks. The signal actually "is in the air", but from the caller's phone it gets to the transceiver, which, in turn, communicates with the similar equipment closest to the called subscriber ... via fiber-optic networks.

The stage of radio transmission of data only covers the signal path from the telephone to the nearest base station, which is connected to other communication networks in a completely traditional way. How cellular communication works is clear. What are the pros and cons?

The technology provides greater mobility compared to analog data transmission, but carries the same risks of unwanted interference and the possibility of wiretapping.

Cell signal path

Let us consider in more detail how the signal reaches the called subscriber.

1. The user dials the number.
2. His phone is establishing radio contact with the nearest base station. They are located in high-rise buildings, industrial buildings and towers. Each station consists of transmit-receive antennas (from 1 to 12) and a control unit. Base stations that serve the same territory are connected to the controller.
3. From the control unit of the base station, the signal is transmitted through the cable to the controller, and from there, also through the cable, to the switch. This device provides input and output of a signal to various communication lines: long-distance, city, international, and other mobile operators. Depending on the size of the network, it can involve either one or several switches connected to each other using wires.
4. From "own" switchboard, the signal is transmitted via high-speed cables to the switchboard of another operator, and the latter easily determines which controller's coverage area is the subscriber to whom the call is addressed.
5. The switch calls the desired controller, which forwards the signal to the base station, which "polls" the mobile phone.
6. The called subscriber receives an incoming call.

Such a multilayer network structure allows you to evenly distribute the load between all its nodes. This reduces the likelihood of equipment failure and ensures uninterrupted communication.

How cellular communication works is clear. What are the pros and cons? The technology provides greater mobility compared to analog data transmission, but carries the same risks of unwanted interference and the possibility of wiretapping.

Satellite connection

Let's see how satellite communications work, the highest stage in the development of radio relay communications today. A repeater placed in orbit is capable of covering a huge area of ​​the planet's surface on its own. A network of base stations, as in the case of cellular communications, is no longer needed.

An individual subscriber gets the opportunity to travel practically without restrictions, staying in touch even in the taiga or in the jungle. A legal subscriber can bind a whole mini-automatic telephone exchange to one repeater antenna (this is a familiar "dish"), however, one should take into account the volume of incoming and outgoing, as well as the size of files that need to be sent.

Cons of technology:

• serious weather dependence. A magnetic storm or other cataclysm can leave a subscriber without communication for a long time.
• if something physically breaks down on the satellite transponder, the time that will pass before the full functionality is restored will take a very long time.
• the cost of communication services without borders often exceeds the more usual bills. When choosing a communication method, it is important to consider how much you need such a functional connection.

Satellite communications: pros and cons

The main feature of the "satellite" is that it provides subscribers with independence from land lines. The advantages of this approach are obvious. These include:

• equipment mobility. It can be deployed in a very short time;
• the ability to quickly create extensive networks covering large areas;
• communication with hard-to-reach and remote areas;
• redundancy of channels that can be used in the event of a ground communication breakdown;
• flexibility of the technical characteristics of the network, allowing it to be adapted to almost any requirement.

Cons of technology:

• serious weather dependence. A magnetic storm or other cataclysm can leave a subscriber without communication for a long time;
• if something is physically out of order on the satellite repeater, the time that will pass before the system is fully restored will stretch for a long time;
• the cost of communication services without borders often exceeds the more usual bills.

When choosing a communication method, it is important to consider how much you need such a functional connection.

How radio communication works

Radio (Latin radio - radiate, emit rays - radius - ray) is a type of wireless communication in which radio waves are used as a signal carrier, freely propagating in space.

Principle of operation
Transmission occurs as follows: on the transmitting side, a signal with the required characteristics (frequency and amplitude of the signal) is generated. The transmitted signal then modulates the higher frequency oscillation (carrier). The received modulated signal is emitted by the antenna into space. On the receiving side, radio waves induce a modulated signal in the antenna, after which it is demodulated (detected) and filtered by a low-pass filter (thereby getting rid of the high-frequency component - the carrier). The received modulated signal is radiated by the antenna into space.
On the receiving side, the radio waves induce a modulated signal in the antenna, after which it is demodulated (detected) and filtered by a low-pass filter (thereby getting rid of the high-frequency component - the carrier).). Thus, a useful signal is extracted. The received signal may differ slightly from that transmitted by the transmitter (distortion due to interference and interference).

Frequency bands
The frequency grid used in radio communications is conventionally divided into ranges:

• Long waves (LW) - f = 150-450 kHz (l = 2000-670 m)
• Medium waves (MW) - f = 500-1600 kHz (l = 600-190 m)
• Short waves (HF) - f = 3-30 MHz (l = 100-10 m)
• Ultrashort waves (VHF) - f = 30 MHz- 300 MHz (l = 10-1 m)
• High frequencies (HF-centimeter range) - f = 300 MHz - 3 GHz (l = 1-0.1 m)
• Extremely high frequencies (EHF-millimeter range) - f = 3 GHz - 30 GHz (l = 0.1-0.01 m)
• Hyperhigh frequencies (HHF - micrometer range) - f = 30 GHz - 300 GHz (l = 0.01-0.001 m)

Depending on the range, radio waves have their own characteristics and propagation laws:

• LWs are strongly absorbed by the ionosphere; surface waves, which propagate around the earth, are of primary importance. Their intensity decreases relatively quickly with distance from the transmitter.
• SW are strongly absorbed by the ionosphere during the day, and the area of ​​effect is determined by the surface wave, in the evening they are well reflected from the ionosphere and the area of ​​effect is determined by the reflected wave.
• HF propagates exclusively through reflection by the ionosphere, so there is a so-called radio silence zone around the transmitter. During the day, shorter waves (30 MHz) propagate better, at night, longer ones (3 MHz). Short waves can travel long distances with low transmitter power.
• VHF propagates in a straight line and, as a rule, is not reflected by the ionosphere. They easily bend around obstacles and have a high penetrating power.
• HF does not go around obstacles, spreads within the line of sight. Used in WiFi, cellular, etc.
• EHF does not bend around obstacles, is reflected by most of the obstacles, and spreads within the line of sight. Used for satellite communications.
• Hyper-high frequencies do not bend around obstacles, are reflected like light, and propagate within the line of sight. Limited use.

Propagation of radio waves
Radio waves propagate in void and in the atmosphere; earthly solid and water are opaque for them. However, due to the effects of diffraction and reflection, communication is possible between points on the earth's surface that do not have a line of sight (in particular, those located at a great distance).
The propagation of radio waves from a source to a receiver can occur in several ways simultaneously. This spread is called multipath. Due to the multipath and changes in the parameters of the environment, fading occurs - a change in the level of the received signal over time. With multipath, the change in the signal level occurs due to interference, that is, at the point of reception, the electromagnetic field is the sum of time-shifted radio waves of the range.

Radar

Radar- the field of science and technology, combining methods and means of detection, measuring coordinates, as well as determining the properties and characteristics of various objects based on the use of radio waves. A close and somewhat overlapping term is radio navigation, however, in radio navigation, an object whose coordinates are measured plays a more active role, most often this is the determination of its own coordinates. The main technical device for radar is a radar station.

Distinguish between active, semi-active, active with a passive response and passive RL. They are subdivided according to the used range of radio waves, by the type of the probing signal, the number of channels used, the number and type of measured coordinates, the location of the radar.

Operating principle

Radar is based on the following physical phenomena:

• Radio waves are scattered by electrical inhomogeneities encountered along the path of their propagation (objects with other electrical properties that are different from the properties of the propagation medium). In this case, the reflected wave, as well as the actual radiation of the target, allows the target to be detected.
• At large distances from the radiation source, it can be assumed that radio waves propagate in a straight line and at a constant speed, due to which it is possible to measure the range and angular coordinates of the target (Deviations from these rules, which are valid only in the first approximation, are studied by a special branch of radio engineering - Radio wave propagation. these deviations lead to measurement errors).
• The frequency of the received signal differs from the frequency of the emitted oscillations with the mutual movement of the points of reception and radiation (Doppler effect), which allows you to measure the radial speeds of the target relative to the radar.
• Passive radar uses the emission of electromagnetic waves by the observed objects, it can be thermal radiation inherent in all objects, active radiation created by the technical means of the object, or spurious radiation created by any objects with working electrical devices.

cellular

cellular, mobile network- one of the types of mobile radio communications, which is based on cellular network... The key feature is that the total coverage area is divided into cells (cells), determined by the coverage areas of individual base stations (BS). The honeycombs overlap partially and together form a network. On an ideal (even and without building) surface, the coverage area of ​​one BS is a circle, therefore, the network composed of them looks like honeycombs with hexagonal cells (honeycombs).

The network consists of spaced-apart transceivers operating in the same frequency range, and switching equipment that allows determining the current location of mobile subscribers and ensuring continuity of communication when a subscriber moves from the coverage area of ​​one transceiver to the coverage area of ​​another.

The principle of cellular communication

The main components of a cellular network are cell phones and base stations, which are usually located on rooftops and towers. When turned on, the cell phone listens to the air, finding a signal from the base station. The telephone then sends its unique identification code to the station. The telephone and the station maintain constant radio contact, periodically exchanging packets. The phone can communicate with the station using an analog protocol (AMPS, NAMPS, NMT-450) or digital (DAMPS, CDMA, GSM, UMTS). If the phone leaves the range of the base station (or the quality of the radio signal of the service cell deteriorates), it establishes communication with another (eng. handover).

Cellular networks can consist of base stations of different standards, which allows you to optimize network performance and improve its coverage.

Cellular networks of different operators are connected to each other, as well as to the landline telephone network. This allows subscribers of one operator to make calls to subscribers of another operator, from mobile phones to landlines and from landlines to mobiles.

Operators can conclude roaming agreements with each other. Thanks to such agreements, the subscriber, being outside the coverage area of ​​his network, can make and receive calls through the network of another operator. As a rule, this is done at higher rates. The possibility of roaming appeared only in 2G standards and is one of the main differences from 1G networks.

Operators can share network infrastructure, reducing network deployment and operational costs.

Cellular services

Cellular operators provide the following services:

• Voice call;
• Answering machine in cellular communication (service);
• Roaming;
• Caller ID (Automatic Caller ID) and AntiAON;
• Reception and transmission of short text messages (SMS);
• Reception and transmission of multimedia messages - images, melodies, video (MMS service);
• Mobile bank (service);
• Internet access;
• Video call and video conferencing

The television

The television(Greek τήλε - far away and lat. video- I see; from Novolatinsky televisio- far-sightedness) - a set of devices for transmitting a moving image and sound over a distance. In common use, it is also used to designate organizations involved in the production and distribution of television programs.

Basic principles

Television is based on the principle of sequential transmission of picture elements by radio signal or by wire. The decomposition of the image into elements occurs using a Nipkov disk, a cathode-ray tube or a semiconductor matrix. The number of picture elements is selected in accordance with the radio channel bandwidth and physiological criteria. To narrow the band of transmitted frequencies and reduce the visibility of flickering on the TV screen, interlaced scanning is used. It also allows you to increase the smoothness of the transmission of motion.

The television path in general includes the following devices:

1. TV transmission camera. Serves for converting an image obtained with a lens on a target of a transmitting tube or semiconductor matrix into a television video signal.
2. Video recorder. Records and at the right time reproduces the video signal.
3. Video mixer. Allows you to switch between multiple image sources: camcorders, VCRs and others.
4. Transmitter. The RF signal is modulated by a television video signal and transmitted by radio or wire.
5. Receiver - TV. With the help of sync pulses contained in the video signal, the television image is reproduced on the receiver screen (kinescope, LCD, plasma panel).

In addition, an audio path similar to a radio transmission path is used to create a television transmission. Sound is transmitted on a separate frequency, usually using frequency modulation, a technique similar to FM radio stations. In digital television, soundtrack, often multichannel, is transmitted in a common data stream with an image.

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Date the page was created: 2016-04-11

Communication is called mobile if the source of information or its recipient (or both) move in space. Since its inception, radio communication has been mobile. Above, in the third chapter, it is shown that the first radio stations were intended for communication with mobile objects - ships. After all, one of the first radio communication devices A.S. Popov was installed on the battleship "Admiral Apraksin". And it was thanks to radio communication with him that in the winter of 1899-1900 this ship, lost in the ice of the Baltic Sea, was saved. However, in those years, this "mobile communication" required bulky radio transceiver devices, which did not contribute to the development of much-needed individual radio communication even in the Armed Forces, let alone private clients.

On June 17, 1946, in St. Louis, USA, telephone business leaders AT&T and Southwestern Bell launch the first private radiotelephone network. The elementary base of the equipment was tube electronic devices, so the equipment was very bulky and was intended only for installation in cars. The weight of the equipment without power supplies was 40 kg. Despite this, the popularity of mobile communications began to grow rapidly. This created a new, more serious problem than weight and dimensions. An increase in the number of radio facilities, with a limited frequency resource, led to strong mutual interference for radio stations operating on channels close in frequency, which significantly deteriorated the quality of communication. To eliminate mutual interference at repeating frequencies, it was necessary to ensure a minimum of a hundred-kilometer spacing in space between the two groups of radio systems. That is why mobile communications were basically used for the needs of special services. For mass implementation, it was required to change not only the weight and dimensions, but also the very principle of organizing communications.

As noted above, in 1947, the transistor was invented, performing the functions of vacuum tubes, but having a much smaller size. It was the appearance of transistors that was of great importance for the further development of radiotelephone communication. The replacement of electronic tubes with transistors has created the prerequisites for the widespread introduction of a mobile phone. The main deterrent was the principle of communication organization, which would eliminate or at least reduce the influence of mutual interference.

Studies of the ultrashort wavelength range of waves, carried out in the 40s of the last century, made it possible to reveal its main advantage over short waves - broadband, i.e. high frequency capacity and the main disadvantage - strong absorption of radio waves by the propagation medium. Radio waves of this range are not able to bend around the earth's surface, therefore, the communication range was provided only on the line of sight, and, depending on the transmitter power, a maximum of 40 km was provided. This disadvantage soon turned into an advantage that gave impetus to the active mass adoption of cellular telephony.

In 1947, D. Ring, an employee of the American company Bell Laboratories, proposed a new idea for organizing communications. It consisted in dividing space (territory) into small sections - cells (or cells) with a radius of 1–5 kilometers and in separating radio communication within one cell (by rational repetition of the communication frequencies used) from communication between cells. Frequency repetition has significantly reduced frequency resource utilization problems. This made it possible to use the same frequencies in different cells distributed in space. In the center of each cell, it was proposed to locate a base transmitting and receiving radio station, which provided radio communication within the cell with all subscribers. The dimensions of the cell were determined by the maximum communication range of the radiotelephone apparatus with the base station. This maximum range is called the cell radius. During the conversation, the cellular radiotelephone is connected to the base station by a radio channel, through which the telephone conversation is transmitted. Each subscriber must have his own micro-radio station - "mobile phone" - a combination of a telephone, a transceiver and a mini-computer. Subscribers communicate with each other through base stations that are connected to each other and to the public telephone network.

To ensure uninterrupted communication when a subscriber moves from one zone to another, it was necessary to use computer control over the telephone signal emitted by the subscriber. It was computer control that made it possible to switch a mobile phone from one intermediate transmitter to another within just a thousandth of a second. Everything happens so quickly that the subscriber simply does not notice it. Thus, computers are the central part of a mobile communication system. They search for a subscriber in any of the cells and connect him to the telephone network. When a subscriber moves from one cell (cell) to another, computers seem to transfer the subscriber from one base station to another and connect the subscriber of the "foreign" cellular network to "their" network. This happens at the moment when the “stranger” subscriber is in the coverage area of ​​the new base station. Thus, roaming is carried out (which in English means "wandering" or "vagrancy").

As noted above, the principles of modern mobile communications were an achievement already at the end of the 40s. However, in those days, computer technology was still at such a level that its commercial use in telephone systems was difficult. Therefore, the practical application of cellular communication became possible only after the invention of microprocessors and integrated semiconductor microcircuits.

The first cellular telephone was designed by Martin Cooper (Motorola, USA).

In 1973, in New York, on top of a 50-storey building by Motorola, under his leadership, the world's first cellular base station was installed. She could serve no more than 30 subscribers and connect them to land lines.

On April 3, 1973, Martin Cooper dialed his boss's number and said the following words: “Imagine, Joel, that I call you from the world's first cell phone. I have it in my hands, and I am walking along New York Street. "

The phone Martin called from was called Dyna-Tac. Its dimensions were 225 × 125 × 375 mm, and its weight was a little less than 1.15 kg, which, however, is much less than the 30 kilogram devices of the late forties. With the help of the device it was possible to call and receive a signal, to negotiate with a subscriber. This phone had 12 keys, of which 10 were digital for dialing the subscriber's number, and the other two provided the start of a conversation and interrupted the call. The Dyna-Tac batteries allowed a talk time of about half an hour, and it took 10 hours to charge them.

Although most of the development took place in the United States, the first commercial cellular network was launched in May 1978 in Bahrain. Two cells with 20 channels in the 400 MHz range served 250 subscribers.

A little later, cellular communication began its triumphant march around the world. More and more countries understood the benefits and convenience that it could bring. However, the lack of a single international standard for using the frequency range, over time, led to the fact that the owner of a cell phone, moving from one state to another, could not use a mobile phone.

In order to eliminate this major deficiency, since the late seventies Sweden, Finland, Iceland, Denmark and Norway have started joint research to develop a single standard. The result of the research was the NMT-450 (Nordic Mobile Telephone) communication standard, which was intended to operate in the 450 MHz range. This standard was first used in 1981 in Saudi Arabia, and only a month later in Europe. Various versions of the NMT-450 were adopted in Austria, Switzerland, Holland, Belgium, Southeast Asia and the Middle East.

In 1983, the AMPS (Advanced Mobile Phone Service) network was launched in Chicago, which was developed by Bell Laboratories. In 1985, in England, the TACS (Total Access Communications System) standard was adopted, which was a variation of the American AMPS. Two years later, due to a sharp increase in the number of subscribers, the HTACS (Enhanced TACS) standard was adopted, adding new frequencies and partially correcting the shortcomings of its predecessor. France, on the other hand, stood apart from everyone and began using its own Radiocom-2000 standard since 1985.

The next was the NMT-900 standard, using the frequencies of the 900 MHz range. The new version was introduced in 1986. It allowed to increase the number of subscribers and improve the stability of the system.

However, all of these standards are analog and belong to the first generation of cellular communication systems. They use an analog method of transmitting information using frequency (FM) or phase (PM) modulation - as in conventional radio stations. This method has a number of significant disadvantages, the main of which are the ability to listen to conversations by other subscribers and the impossibility of combating signal fading when the subscriber moves, as well as under the influence of the terrain and buildings. The congestion of the frequency ranges caused interference in conversations. Therefore, by the end of the 1980s, the creation of the second generation of cellular communication systems based on digital signal processing methods began.

Previously, in 1982, the European Conference of Administrations of Posts and Telecommunications (CEPT), uniting 26 countries, decided to create a special group, Groupe Special Mobile. Its goal was to develop a single European standard for digital cellular communications. The new communication standard took eight years to develop, and was first announced only in 1990, when the specifications of the standard were proposed. The special group initially decided to use the 900 MHz band as a single standard, and then, taking into account the prospects for the development of cellular communications in Europe and around the world, it was decided to allocate the 1800 MHz band for the new standard.

The new standard was named GSM - Global System for Mobile Communications. GSM 1800 MHz is also called DCS-1800 (Digital Cellular System 1800). The GSM standard is a digital standard for cellular communications. It implements time division multiplexing (TDMA - time division multiple access, message encryption, block coding, and GMSK modulation) (Gaussian Minimum Shift Keying).

The first state to launch a GSM network is Finland, which launched this standard into commercial operation in 1992. The following year, the first DCS-1800 One-2-One network was launched in the UK. From that moment on, the global spread of the GSM standard all over the world begins.

The next step after GSM is the CDMA standard, which provides faster and more reliable communication due to the use of code division. This standard began to emerge in the United States in 1990. In 1993, the United States began to use CDMA (or IS-95) in the 800 MHz frequency range. At the same time, the DCS-1800 One-2-One network was launched in England.

In general, there were many communication standards, and by the mid-nineties most of the civilized countries were smoothly moving to digital specifications. If the networks of the first generation allowed only voice to be transmitted, then the second generation of cellular communication systems, which is GSM, also allow providing other non-voice services. In addition to the SMS service, the first GSM phones allowed for the transmission of other non-voice data. For this, a data transfer protocol was developed, called CSD (Circuit Switched Data). However, this standard had very modest characteristics - the maximum data transfer rate was only 9600 bits per second, and then on condition of stable communication. However, such speeds were quite enough for the transmission of a facsimile message.

The rapid development of the Internet in the late 90s led to the fact that many cellular users wanted to use their handsets as modems, and the existing speeds were clearly not enough for this.
In order to somehow meet the needs of their customers for access to the Internet, engineers invent the WAP protocol. WAP is an abbreviation for Wireless Application Protocol, which translates to wireless application access protocol. In principle, WAP can be called a simplified version of the standard Internet protocol HTTP, only adapted for the limited resources of mobile phones, such as small display sizes, low performance of telephone processors and low data transfer rates in mobile networks. However, this protocol did not allow standard Internet pages to be viewed; they had to be written in WML, which was adapted for cell phones. As a result, although subscribers of cellular networks got access to the Internet, it turned out to be very "cut down" and of little interest. Plus, to access WAP-sites, the same communication channel was used as for voice transmission, that is, while you are downloading or viewing the page, the communication channel is busy, and the same money is debited from the personal account as during the conversation. As a result, quite an interesting technology was practically buried for some time and was used by subscribers of cellular networks of various operators very rarely.
Cellular equipment manufacturers urgently had to look for ways to increase the data transfer rate, and as a result, the HSCSD (High-Speed ​​Circuit Switched Data) technology was born, which provided a quite acceptable speed - up to 43 kilobits per second. This technology was popular with a certain circle of users. But still, this technology did not lose the main drawback of its predecessor - data was still transmitted via a voice channel. The developers again had to do painstaking research. The efforts of engineers were not in vain, and quite recently a technology called GPRS (General Packed Radio Services) appeared - this name can be translated as a packet radio data transmission system. This technology uses the principle of channel separation for voice and data transmission. As a result, the subscriber pays not for the duration of the connection, but only for the amount of transmitted and received data. In addition, GPRS has another advantage over earlier technologies for mobile data transmission - during the GPRS connection, the phone is still able to receive calls and SMS messages. At the moment, modern phone models on the market, when making a call, suspend the GPRS connection, which is automatically resumed at the end of the call. Such devices are classified as a class B GPRS terminal. It is planned to produce class A terminals, which will simultaneously download data and conduct a conversation with an interlocutor. There are also special devices that are designed only for data transmission, and they are called GPRS modems or class C terminals. In theory, GPRS is capable of transmitting data at a speed of 115 kilobits per second, but at the moment most telecom operators provide a communication channel that allows you to develop speed up to 48 kilobits per second. This is primarily due to the equipment of the operators themselves and, as a result, the lack of cell phones on the market that support higher speeds.

With the advent of GPRS, they again remembered the WAP protocol, since now, with the help of new technology, access to small-volume WAP-pages becomes many times cheaper than in the days of CSD and HSCSD. Moreover, many telecom operators provide unlimited access to WAP-resources of the network for a small monthly subscription fee.
With the advent of GPRS, cellular networks have ceased to be called second generation networks - 2G. We are currently in the 2.5G era. Non-voice services are becoming more and more in demand, the cell phone, computer and the Internet are merging. Developers and operators are offering us more and more different value-added services.
So, using the capabilities of GPRS, a new messaging format was created, which was called MMS (Multimedia Messaging Service), which, unlike SMS, allows you to send from a cell phone not only text, but also various multimedia information, for example, sound recordings, photos and even video clips. Moreover, an MMS message can be sent either to another phone that supports this format, or to an e-mail box.
The increase in the processor power of phones now allows you to download and run various programs on it. The Java2ME language is most often used to write them. Owners of most modern phones now have no difficulty connecting to the Java2ME application developers site and downloading to their phone, for example, a new game or other necessary program. Also, no one will be surprised by the possibility of connecting the phone to a personal computer in order to save or edit an address book or organizer on a PC using special software, most often supplied with the handset; while on the road, using a combination of mobile phone + laptop, go to the full-fledged Internet and view your e-mail. However, our needs are constantly growing, the volume of transmitted information is growing almost daily. And more and more demands are being made on cell phones, as a result of which the resources of current technologies are becoming insufficient to meet our growing demands.

It is for the solution of these requests that the rather recently created third-generation 3G networks are intended, in which data transmission dominates over voice services. 3G is not a communication standard, but the general name for all high-speed cellular networks that will grow and are already growing out of the existing ones. Huge data transfer rates allow you to transfer high-quality video images directly to your phone, to maintain a constant connection to the Internet and local networks. The use of new, improved security systems allows today to use the phone for various financial transactions - a mobile phone is quite capable of replacing a credit card.

It is quite natural that third generation networks will not become the final stage in the development of cellular communications - as they say, progress is inexorable. The ongoing integration of various types of communication (cellular, satellite, television, etc.), the emergence of hybrid devices, including a cell phone, PDA, video camera, will certainly lead to the emergence of 4G, 5G networks. And today, even science fiction writers are unlikely to be able to tell about how this evolutionary development will end.

Globally, there are now about 2 billion mobile phones in use, of which more than two-thirds are connected to the GSM standard. CDMA is the second most popular, while the rest represent specific standards used mainly in Asia. Now in developed countries there is a situation of "satiety", when demand stops growing.