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

A network of base stations provides wireless communication to a cell phone.

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 comes the term "cellular communication". When a subscriber moves, his phone is serviced by one or another base station, and the switching (cell change) occurs automatically, completely unnoticed by the subscriber, and does not affect the quality of communication. This approach allows, using low-power radio signals, to cover large areas with a mobile communication network, which provides this type of communication, in addition to efficiency, also high level environmental friendliness.

The operating company not only technically provides mobile communications, but also enters into economic relationships with subscribers who purchase from it a certain set of basic and additional services. Since there are a lot of types of services, prices for them are combined into sets called tariff plans. The billing system (software and hardware system that keeps records of the 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, those providing the subscriber with roaming services (the ability to use mobile communications in other cities and countries). All mutual settlements for mobile communication, including roaming, the subscriber makes with his operator, which is a single settlement center for him.

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

While roaming, the subscriber usually keeps his phone number, continues to use his cell phone, making and receiving calls in the same way as in home network. All actions necessary for this, including inter-operator traffic exchange and attraction, as necessary, of the resources of other communication companies (for example, those providing transcontinental communications), 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: a subscriber can be given another device for the duration of the trip, while keeping his phone number and automatically routing calls.

History of cellular communication.

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 communication everywhere and everywhere.

Networks on the first civil cellular standard - NMT-450 - appeared in 1981. Although the name of the standard is an abbreviation of the words Nordic Mobile Telephony (“mobile telephony of the northern countries”), the first cellular network on the planet was deployed in Saudi Arabia. In Sweden, Norway, Finland (and other Nordic countries), NMT networks went online a few months later.

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

The NMT and AMPS standards, which are commonly referred to as the first generation of cellular communication systems, provided for the transmission of data in analog form, which did not allow for the proper level of noise immunity and protection against unauthorized connections. Subsequently, they had modifications improved through the use of digital technologies, for example, DAMPS (the first letter of the abbreviation owes its appearance to the word Digital - “digital”).

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

As early as 1982, the European Conference of Postal and Telecommunications Administrations (CEPT) set up a group to develop a single digital cellular standard. The brainchild of this group was GSM (Global System for Mobile Communications).

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

For the operation of GSM equipment, several frequency bands are allocated - they are indicated by 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 the standard was approved 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:

– protection from interference, interception and "twins";

- 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 transfer from high speeds;

- the presence on the market of a large number telephone sets 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 acquired the possibility of expansion due to some "add-ons" over the existing infrastructure that provide high-speed data transmission. GSM networks with GPRS (General Packet Radio Service) support are called 2.5G, and GSM networks with support for the EDGE (Enhanced Data rates for Global Evolution) standard are sometimes called 2.75G networks.

In the late 1990s, third-generation (3G) networks appeared in Japan and South Korea. The main difference between the standards on which 3G networks are built and their predecessors is the enhanced capabilities of high-speed data transfer, 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 3G networks currently exist only in a number of regions of the world, work is already underway in the engineering and technical laboratories of the largest companies to create standards for cellular communication. fourth generation. At the same time, not only a further increase in the data transfer rate is put at the forefront, but also an increase in the efficiency of using the bandwidth of the frequency bands allocated for mobile communications in order to access services for a large number of subscribers located in a limited area (which is especially important for megacities) .

Other mobile communication systems.

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

The DECT microcellular communication standard, which is used for communications in a limited area, is becoming increasingly popular. The base station of the DECT standard is capable of providing handsets (up to 8 of them can be serviced simultaneously) with each other, call forwarding, and also access to the public telephone network. The potential of the DECT standard makes it possible to provide mobile communications within urban microdistricts, individual companies or apartments. They turn out to be optimal in regions with low-rise buildings, whose subscribers need only voice communication and can do without mobile transmission data 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 a radio signal from one terminal to another when they are at a considerable 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 on large technological sites (along highways, at a construction site, on the territory of factories, etc.), then trunking terminals do not have entertainment capabilities and design frills in design.

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

Paging provides receiving short messages to subscriber terminals - pagers. At present, paging communications in civil communications are practically not used; due to their limitations, they are pushed into the field 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 subspecies of mobile communications 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. Subscriber terminals in this case are computers - both laptops and PDAs. They can also provide two-way voice communication over the Internet, but this feature is used extremely rarely, the connection is mainly used to access the most common Internet services - e-mail, websites, instant messaging systems (for example, ICQ), etc. .

Where is mobile communication going?

In developed regions, the main direction in the development of mobile communications for the near future is convergence: providing subscriber terminals with automatic switching from one network to another in order to effective use capabilities of all communication systems. Saving money for subscribers and improving the quality of communication will allow automatic switching, for example, from GSM to DECT (and vice versa), with satellite communications to the "ground", and when providing wireless transmission data - 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 was higher than the number of inhabitants. This means that some people used more than one "mobile" - for example, two cell phones serviced by different operators, or a phone for voice communication and a wireless modem for mobile Internet access. In addition, more and more modules wireless communication required to provide technological communications (in these cases, subscribers are not people, but specialized computers).

Currently, cellular operators provide full coverage of the territory of all economically developed regions of the planet, however, the extensive development of networks continues. New base stations are being installed to improve reception in places where the existing network cannot provide stable reception for some reason (for example, in long tunnels, in the metro area, etc.). In addition, cellular networks are gradually penetrating into low-income regions. 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.

The production of cell phones is one of the most dynamically developing areas of the high-tech industry.

The mobile phone service industry is also growing rapidly, offering accessories for personalizing devices: from original ringtones (ringtones) to key fobs, graphic screen savers, stickers on the case, interchangeable panels, covers and laces for carrying the device.

Phone types.

Cellular (mobile) phone - a subscriber terminal operating in a cellular network. Essentially, each cellular telephone is a specialized computer that is focused primarily 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 earlier existing division of devices into "inexpensive", "functional", "business" and "fashion" models is increasingly losing its meaning - business devices acquire the features of fashion models and entertainment functions, as a result of using accessories, inexpensive phones become fashion, and fashion phones functionality grows rapidly.

The miniaturization of handsets, which peaked in 1999-2000, was completed for quite objective reasons: the handsets have reached the 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: to develop appearance devices attract leading designers, 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, and as the main one (the time battery life, screens are being improved, etc.), and their additional features (digital cameras, voice recorders, MP3 players and other "related" devices are built into the devices).

Almost all modern devices, with the exception of some models of the lower price range, allow you to download programs. Most devices can run Java applications, and 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 called smartphones (from a combination of the English words "smart" and "phone" - "smart phone").

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

Non-voice services of cellular networks.

Available to subscribers of cellular networks whole line non-voice services, the “range” of which depends on the capabilities of a particular phone and on the range of offers of the operator company. 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 weather forecasts 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, there are more and more services that are "at the junction", for example, most games and lotteries are paid, there are games that use mobile positioning technologies, etc.

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

– SMS – Short Message Service – transmission of short text messages;

– MMS – Multimedia Messaging Service – transmission of multimedia messages: photos, videos, etc.;

– automatic roaming;

– identification of the caller's number;

– ordering and receiving various means of personalization directly via cellular communication channels;

– access to the Internet and viewing specialized (WAP) sites;

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

– data transfer using the built-in modem (it can be carried out using various protocols, depending on which technologies are supported by a particular device).

Mobile communications in Russia.

There were no civilian mobile communication systems in the USSR. With some stretch, “civilian” can be called the Altai mobile telephony system, built on the basis of the MRT-1327 standard, which at the turn of the 1970s and 80s was created to provide communications for representatives of the party, state and economic leadership. "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 communications for mobile units of urban emergency services, installing telephones in summer cafes, etc.

The first commercial cellular networks built according to the NMT standard were created in Russia in the autumn 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, 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 mobile operators in Russia that provide services in the GSM standard: MTS, BeeLine and MegaFon. The range and quality of the telecommunications services they offer, as well as their prices, are about the same. By 2005, the number of base stations in the networks of the leading metropolitan operators in Moscow and the Moscow suburbs was about 3,000, and the coverage area exceeded that of most European countries. In addition to them, numerous local operators exist and work quite effectively - both subsidiaries of the "Big Three" and independent companies.

Operators are actively developing the market by 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 segments 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 ahead of most European companies. At present, all three federal GSM operators are preparing for the deployment of 3G commercial networks.

In addition to GSM networks of federal and local mobile operators, networks of other standards continue to be used in Russia: DAMPS, IS-95, NMT-450, DECT and IMT-MC-450. The latter standard has the status of a federal one, and the networks built on its basis (for example, SkyLink) are developing very actively. However, neither in terms of coverage area, nor in terms of the number of subscribers served, networks of all standards other than GSM cannot create significant competition for the top 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. Current state, transition to third generation networks("MTS Library"). M., Eco-Trends, 2004
Popov V.I. Basics of GSM cellular communication("Engineering Encyclopedia of the Fuel and Energy Complex"). M., Eco-Trends, 2005



Do you know what happens after you dial a friend's number on your mobile phone? How does the cellular network find it in the mountains of Andalusia or on the coast of distant Easter Island? Why does the conversation sometimes suddenly stop? Last week I visited Beeline and tried to figure out how cellular communication works ...

A large area of ​​the populated part of our country is covered by Base Stations (BS). In the field, they look like red and white towers, and in the city they are hidden on the roofs of non-residential buildings. Each station picks up a signal from mobile phones at a distance of up to 35 kilometers and communicates with a mobile phone via service or voice channels.

After you have dialed a friend's number, your phone contacts the nearest Base Station (BS) via a service channel and asks you to select voice channel. The base station sends the request to the controller (BSC), which forwards it to the switch (MSC). If your friend is on the same cellular network, the switch will check the Home Location Register (HLR) to find out where in this moment the called subscriber is located (at home, in Turkey or in Alaska), and will transfer the call to the appropriate switchboard, from where it will forward it to the controller and then to the Base Station. The Base Station will contact the mobile phone and connect you with a friend. If your friend is a subscriber of another network or you call a landline phone, then your switch will contact the corresponding switch of another network. Difficult? Let's take a closer look. The Base Station is a pair of iron cabinets locked in a well-air-conditioned room. Given that in Moscow it was +40 on the street, I wanted to live in this room for a while. Usually, the Base Station is located either in the attic of the building or in a container on the roof:

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The Base Station antenna is divided into several sectors, each of which "shines" in its own direction. The vertical antenna communicates with phones, the round one connects the Base Station with the controller:

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Each sector can serve up to 72 calls at the same time, depending on the setup and configuration. A Base Station can consist of 6 sectors, so one Base Station can serve up to 432 calls, however, there are usually fewer transmitters and sectors installed in the station. Cellular operators prefer to install more BS to improve the quality of communication. The Base Station can operate in three bands: 900 MHz - the signal at this frequency spreads further and penetrates better inside buildings 1800 MHz - the signal spreads over shorter distances, but allows you to install more transmitters on 1 sector 2100 MHz - 3G Network This is how the cabinet looks like with 3G equipment:

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900 MHz transmitters are installed at Base Stations in fields and villages, and in the city, where Base Stations are stuck like needles in a hedgehog, communication is mainly carried out at a frequency of 1800 MHz, although transmitters of all three bands can be present at any Base Station at the same time.

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A 900 MHz signal can reach up to 35 kilometers, although the "range" of some Base Stations along the routes can reach up to 70 kilometers, by reducing the number of simultaneously served subscribers at the station by half. Accordingly, our phone, with its small built-in antenna, can also transmit a signal up to 70 kilometers... All Base Stations are designed to provide optimum ground level radio coverage. Therefore, despite the range of 35 kilometers, the radio signal is simply not sent to the altitude of the aircraft. However, some airlines have already begun installing low-powered base stations on their aircraft that provide coverage inside the aircraft. Such a BS is connected to the terrestrial cellular network using satellite channel. The system is complemented by a control panel that allows the crew to turn the system on and off, as well as certain types of services, such as turning off the voice on night flights. The phone can measure signal strength from 32 Base Stations simultaneously. It sends information about the 6 best (by signal level) over the service channel, and the controller (BSC) decides which BS to transmit current call(Handover) if you are on the move. Sometimes the phone can make a mistake and transfer you to the BS with worst signal, in which case the conversation may be interrupted. It may also turn out that at the Base Station that your phone has selected, all voice lines are busy. In this case, the conversation will also be interrupted. I was also told about the so-called "top floor problem". If you live in a penthouse, then sometimes, when moving from one room to another, the conversation may be interrupted. This is because in one room the phone can "see" one BS, and in the second - another, if it goes to the other side of the house, and, at the same time, these 2 Base Stations are at a great distance from each other and are not registered as " neighboring" mobile operator. In this case, the transfer of a call from one BS to another will not occur:

Communication in the metro is provided in the same way as on the street: Base Station - controller - switch, with the only difference that small Base Stations are used there, and in the tunnel coverage is provided not by an ordinary antenna, but by a special radiating cable. As I wrote above, one BS can make up to 432 calls at the same time. Usually this power is enough for the eyes, but, for example, during some holidays, the BS may not be able to cope with the number of people who want to call. This usually happens on New Year when everyone starts to congratulate each other. SMS are transmitted through service channels. On March 8 and February 23, people prefer to congratulate each other via SMS, sending funny rhymes, and phones often cannot agree with the BS on the allocation of a voice channel. I was told an interesting story. From one district of Moscow, complaints began to come from subscribers that they could not get through anywhere. Technicians began to understand. Most of the voice channels were free, and all service channels were busy. It turned out that next to this BS there was an institute where exams were taking place and students were constantly exchanging text messages. The phone divides long SMS into several short ones and sends each one separately. Employees of the technical service are advised to send such congratulations using MMS. It will be faster and cheaper. From the Base Station, the call goes to the controller. It looks as boring as the BS itself - it's just a set of cabinets:

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Depending on the equipment, the controller can serve up to 60 Base Stations. Communication between the BS and the controller (BSC) can be carried out via a radio relay channel or via optics. The controller controls the operation of radio channels, incl. controls the movement of the subscriber, signal transmission from one BS to another. The switch looks much more interesting:

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Each switch serves from 2 to 30 controllers. It already occupies a large hall filled with various cabinets with equipment:

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The switch performs traffic control. Remember the old movies where people first called the “girl”, and then she connected them with another subscriber, rewiring the wires? Modern switches do the same:

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To control the network, Beeline has several cars, which they affectionately call "hedgehogs". They move around the city and measure the signal level of their own network, as well as the level of the network of colleagues from the "Big Three":

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The entire roof of such a car is studded with antennas:

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Inside there is equipment that makes hundreds of calls and captures information:

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Round-the-clock control over switches and controllers is carried out from the Mission Control Center of the Network Control Center (NCC):

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There are 3 main areas for monitoring the cellular network: accident rate, statistics and feedback from subscribers. Just like in airplanes, all cellular network equipment has sensors that send a signal to the MCC and output information to the dispatchers' computers. If some equipment is out of order, then the light on the monitor will “blink”. The MSC also keeps track of statistics for all switches and controllers. He analyzes it by comparing it with previous periods (hour, day, week, etc.). If the statistics of one of the nodes began to differ sharply from the previous indicators, then the light on the monitor will again begin to “blink”. Feedback accepted by subscriber service operators. If they cannot solve the problem, then the call is transferred to a technical specialist. If he turns out to be powerless, then an “incident” is created in the company, which is solved by engineers involved in the operation of the corresponding equipment. The switches are monitored around the clock by 2 engineers:

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The graph shows the activity of Moscow switches. It is clearly seen that almost no one calls at night:

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Control over the controllers (sorry for the tautology) is carried out from the second floor of the Network Control Center:

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Surely, you often hear the expression "cell phone". Have you ever wondered why a mobile phone is called a cell phone? In this material, we will talk about the history of the emergence of cellular communications and the principles of its operation.

The history of cell phones

American journalist Robert Sloss predicted the advent of "mobile phones" as early as 1910. First new technology the police got into service - in 1921, law enforcement officers in Detroit received information from dispatchers via radio communications in the 2 MHz band, and by 1940, mobile phones were already in 10,000 police cars across the country. And in 1946, the first public mobile radiotelephone appeared in St. Louis. Communication was carried out in two bands - 150 and 450 MHz.

In 1957, the Moscow engineer Kupriyanovich introduced the LK-1 mobile phone. The prototype "mobile phone" weighed three kilograms and made it possible to call 25-30 km in the district.

The very next year, Kupriyanovich introduced a noticeably more advanced model LK-1 - weighing only half a kilogram and the size of a box of cigarettes.

At about the same time, specialists from the Voronezh Research Institute of Communications developed the world's first automatic (before that, subscribers were connected manually) Altai mobile communication system. By 1970, she worked in 30 cities of the USSR at a frequency of 150 and 330 megahertz. Each city was served by one base station, the range was from 50 to 100 km, calls were made to Altai, urban and long-distance / international numbers.

Modern cellular communication systems appeared in the USA in 1978, when tests of the first such system for 2 thousand subscribers in the 800 MHz band began in Chicago. The city's residents received their first commercial cellular communication system in October 1983 from AT&T. And the first commercially successful cellular network was the Finnish Autoradiopuhelin (ARP, "Automobile Radiotelephone"). By 1986, more than 30 thousand subscribers used it.

How Cellular Works

A modern cellular network consists of base stations - multi-frequency VHF transceivers, evenly distributed throughout the coverage area. Outwardly, they look like huge red or white towers with special equipment.

The vertical parts of the antenna are responsible for mobile communications, the round ones provide communication with the controller. Radius of action base station- 35 kilometers (but this is not the limit, see below). Each base station has six service sectors, one sector receives up to 70 telephone calls at the same time. Multiply 6 by 70 and you will understand why no one can get through on the New Year :). Base stations operate in four bands:

900 MHz. The smallest number of subscribers served and the maximum coverage area. If there are not so many subscribers in the coverage area of ​​the base station (for example, rural areas), the coverage radius reaches 70 km.
-1 800 MHz. Largest number serviced subscribers, low coverage, good signal penetration through thick walls. Such stations are installed in cities.
-2 100 MHz. Stations with a connection of the previous generation - 3G.
-2 500 MHz. Stations with a new generation of communication - 4G.

Nearby stations never operate in the same range - otherwise interference interference cannot be avoided.

Where did the name "cellular" come from?

What about hundreds? A lot of basic networks are used, circles-radii are superimposed on each other and together form a network resembling a honeycomb. Hence the name of the technology - "cellular communication". A group of seven cells is called a cluster.

This approach gives the mobile subscriber several advantages at once. First, the “dense” arrangement of cells of mobile communication ensures uninterrupted communication - in contrast to fixed communication, we are not tied to one line. Secondly, a mobile (aka cell) phone automatically moves away from the station with the greatest signal attenuation to the smallest, i.e. provides best quality connections. The handover controller is responsible for the "seamless" transition from the old station to the new one.

Now let's look at how everything works from the subscriber side. A working cell phone is always scanning the air for a base station signal. When a signal is found, the cell sends its unique identification code to the station. Next, a periodic exchange of radio packets begins through an analog or digital protocol (for example, CDMA, GSM, UMTS). The communication channel from the station to the subscriber is called DownLink (“downlink”), from the subscriber to the station - UpLink (“uplink”) When you call someone, the phone contacts the station and asks to allocate a voice channel. The station forwards the signal to the controller, which - to the switch. If the subscriber uses another cellular operator, the request goes to "his" switch, if he is in the same network as you, the switch will find the subscriber himself and direct the call to him.



The development of cellular communications began in 1888. It was then that Heinrich Hertz invented the installation, and then with its help the fact of the existence of electromagnetic waves, as well as the possibility of their detection, was proved.

Then, on April 25, 1895, Alexander Stepanovich Popov made a report on the possibility of using electromagnetic waves for signal transmission. It was then that he was the first to demonstrate a device used to register electrical oscillations - a coherer. Of course, before modern technologies, allowing them to be used for tariffs with unlimited traffic, was still far away, but the start was given.

At the same time, in the same 1895, the researcher Guglielmo Marconi conducted an experiment with electromagnetic waves. His goal at that time was the possibility of creating a device for transmitting messages. In March 1896, Popov, using the same device of his own design, managed to transmit a short radiogram consisting of only two words: “Heinrich Hertz” to a distance of 250 meters.

A little later, in 1897, Marconi became the owner of a patent for a device very similar to Popov's. Then, in 1901, Marconi installed a kind of radio on board the Thornisroft steam car and thus conducted the first “mobile” communication. It was from that time that the truly rapid development of radio communications began, and, above all, these achievements were used with might and main in the navy.

A sharp and significant turning point in the history of the formation of modern cellular communications occurred in 1946 in the United States. At that time, AT&T provided mobile services for the first time to individuals. Then the cell phone was located only in the car, it weighed about 12 kilograms (26.5 pounds), and, in fact, combined both the phone and the transceiver, and in it the reception and transmission were carried out on completely different radio frequencies. Communication, thus, was carried out through a repeater or a base station.

The "base station - phone" channel was called "uplink" (that is, "uplink"), but the "phone - base station" channel itself was called "downlink" (in other words, "downlink").

With such a radiotelephone system, the whole city was served by one antenna mounted on a tower, and thus about 25 channels were available. For a car antenna, a wave transmitter was needed that would be capable of transmitting a radio wave over a distance of up to 70 kilometers. Thus, with such a system, not everyone could enjoy mobile communication - after all, there would simply not be enough for all channels.

But the device now known as a walkie-talkie is already a half-duplex device. Such a system means that if two people communicate on the same radio wave (that is, on the radio wave of the same frequency), then they can only talk in turn. Well, a mobile phone, in turn, is a full duplex network. This system means that you will use one frequency to talk and another frequency when you listen. In this order of things, both interlocutors, of course, can talk at the same time.

The idea of ​​the cellular principle of communication inherently implies the following:

Base stations with all their coverage areas form a kind of cells, the size of which is already determined, in turn, by the territorial density of network subscribers. For example, in a network that covers an entire country, the number of cells can be really very large.

So, the antenna is placed in the center of each such cell. In order to reduce interference interference, different frequencies are used in neighboring cells. That is why the same frequencies can only be used in cells located at a sufficient distance from one another. A group of seven cells is called a "cluster". In addition, the maximum cell radius is limited by its technical capabilities and is 35 kilometers (approximately 22 miles).

Thus, the cell size in a real network may depend on some of the following factors:

First, it is the geographical location. Of course, the radius of the cells on the hills and on the flat terrain is slightly larger than on the hilly terrain.

Second, the number of users. It is clear that the telephone load on the same cellular node is limited by the bandwidth of this node, because there is a finite number of calls that it can handle simultaneously.

In addition, the frequency channels that are used for the operation of one of the base stations of the network can also be used by other base stations of this network.

Among other things, the concept of “handoff” is also implied. This means that a network subscriber, for example Beeline, moving from one coverage area of ​​​​a base station to another, will be able to maintain constant, uninterrupted communication, both with a mobile subscriber and with a subscriber of a fixed, wired network.

The networks also cover fairly large areas, so the subscriber, being in the coverage area of ​​absolutely any of these base stations, can either independently get in touch, or another subscriber can call him, and absolutely regardless of his location. It is on this that the roaming service is based, or, for example, the ability to maintain the same Megafon phone numbers outside the country.

Aspects of modern radio communications.

At the present stage, the following frequency ranges have been allocated for mobile networks in Europe. So, frequencies 890 - 915 MHz (GSM band), 1710 - 1785 MHz (DCS band) are used to establish communication in the forward direction, that is, from a mobile phone to a base station (in other words, "uplink").

But the frequencies 935 - 960 MHz (in the GSM band), 1805 - 1880 MHz (in the DCS band) are already used to establish communication in the opposite direction, that is, from the base station to the mobile phone (in other words, "downlink "). Thus, we can assume that the entire GSM band is located within the 2–25 MHz band, while the DCS band is located within the 2–75 MHz band.

Modern mobile phones use a very low power transmitter. So, many devices have two signal values: 0.6 W and 3 W (for example, most radio transmitters consume 4 W or more). Due to the incredibly low power consumption of mobile phones, they can run primarily on batteries. Based on the fact that small power means small batteries, this is what makes cell phones mobile.

Of course, the use of cellular communications requires an extremely large number of base stations in any city, regardless of its size.

For example, in a typical metropolitan area, hundreds of substations are used. This requires sufficient investment, but due to the incredibly large number of people using mobile phones, the cost of communication is not very expensive for one particular person.

Cellular communication is considered one of the most useful inventions of mankind - along with the wheel, electricity, the Internet and the computer. And in just a few decades, this technology has experienced a number of revolutions. How wireless communication began, how cells work and what opportunities the new mobile standard will open 5G?

The first use of mobile phone radio dates back to 1921 when the US Detroit police used one-way dispatch communication in the 2 MHz band to transmit information from a central transmitter to receivers in police cars.

How did the cell phone come about

For the first time, the idea of ​​cellular communication was put forward in 1947 - engineers from Bell Labs Douglas Ring and Ray Young worked on it. However, the real prospects for its implementation began to emerge only by the beginning of the 1970s, when the company's employees developed a working architecture for the cellular communication hardware platform.

So, American engineers suggested placing transmitting stations not in the center, but at the corners of the "cells", and a little later a technology was invented that allows subscribers to move between these "cells" without interrupting communication. After that, it remains to develop operating equipment for such a technology.

Motorola successfully solved the problem - its engineer Martin Cooper demonstrated the first working prototype of a mobile phone on April 3, 1973. He called the head of the research department of a competitor company right off the street and told him about his own successes.

Motorola's management immediately invested $100 million in the promising project, but the technology entered the commercial market only ten years later. This delay is due to the fact that at first it was required to create a global infrastructure of cellular base stations.

In the United States, AT&T took over this work - the telecommunications giant obtained licensing from the federal government of the necessary frequencies and built the first cellular network that covered the largest American cities. The famous Motorola DynaTAC 8000 was the first mobile phone.

The first cell phone went on sale on March 6, 1983. It weighed almost 800 grams, could work on a single charge for 30 minutes of talk time and charged for about 10 hours. At the same time, the device cost $ 3,995 - a fabulous amount at that time. Despite this, the mobile phone instantly became popular.

Why is it called cellular

The principle of mobile communication is simple - the territory on which the connection of subscribers is provided is divided into separate cells or "cells", each of which is served by a base station. At the same time, in each "cell" the subscriber receives identical services, so he himself does not feel the crossing of these virtual boundaries.

Typically, a base station in the form of a pair of iron cabinets with equipment and antennas is placed on a specially built tower, but in the city they are often placed on the roofs of high-rise buildings. On average, each station catches a signal from mobile phones at a distance of up to 35 kilometers.

To improve the quality of service, operators are also installing femtocells - low-power and miniature cellular communication stations designed to serve a small area. They allow you to dramatically improve coverage in those places where it is needed. Cellular communications in Russia will be combined with space

A mobile phone on the network listens to the air and finds a signal from the base station. In addition to the processor and RAM, a modern SIM card has a unique key sewn into it that allows you to log in to the cellular network. Communication between the phone and the station can be carried out using different protocols - for example, digital DAMPS, CDMA, GSM, UMTS.

Cellular networks of different operators are connected to each other, as well as to the fixed line. telephone network. If the phone leaves the coverage area of ​​the base station, the device establishes communication with others - the connection established by the subscriber is imperceptibly transmitted to other "cells", which ensures continuous communication when moving.

In Russia, three bands are certified for broadcasting - 800 MHz, 1800 MHz and 2600 MHz. The 1800 MHz band is considered the most popular in the world, as it combines high capacitance, long range and high penetrating power. It is in it that most mobile networks now operate.

What mobile communication standards are

The first mobile phones worked with 1G technologies - this is the very first generation of cellular communications, which relied on analog telecommunication standards, the main of which was NMT - Nordic Mobile Telephone. It was intended exclusively for the transmission of voice traffic.

By 1991, the birth of 2G is attributed - the main standard of the new generation has become GSM (Global System for Mobile Communications). This standard is still supported today. Communication in this standard has become digital, it has become possible to encrypt voice traffic and send SMS.

The data transfer rate within GSM did not exceed 9.6 kbps, which made it impossible to transmit video or high-quality sound. The GPRS standard, known as 2.5G, was intended to solve the problem. For the first time, he allowed mobile phone owners to use the Internet.

This standard has already provided data transfer rates up to 114 Kbps. However, it soon also ceased to satisfy the ever-increasing demands of users. To solve this problem, the 3G standard was developed in 2000, which provided access to Internet services at a data transfer rate of 2 Mbps.

Another difference with 3G was the assignment of an IP address to each subscriber, which made it possible to turn mobile phones into small computers connected to the Internet. The first commercial 3G network was launched on October 1, 2001 in Japan. In the future, the throughput of the standard has been repeatedly increased.

The most modern standard is fourth-generation 4G communication, which is intended only for high-speed data transfer services. Bandwidth 4G networks are capable of reaching 300 Mbps, which gives the user almost unlimited opportunities to surf the Internet.

Cellular communication of the future

The 4G standard is designed for the continuous transmission of gigabytes of information, it does not even have a channel for voice transmission. Due to extremely efficient multiplexing schemes, downloading a high-definition movie on such a network will take the user 10-15 minutes. However, even its capabilities are already considered limited.

In 2020, the official launch of a new generation of 5G communications is expected, which will allow the transfer of large amounts of data at ultra-high speeds up to 10 Gbps. In addition, the standard will allow you to connect to high speed internet up to 100 billion devices.

It is 5G that will allow the real Internet of Things to appear - billions of devices will exchange information in real time. According to experts, network traffic will soon grow by 400%. For example, cars will be constantly on the global network and receive traffic data.

Low latency will ensure real-time communication between vehicles and infrastructure. A reliable and always-on connection is expected to open the way for the first time to launch fully autonomous vehicles on the roads.

Russian operators are already experimenting with new specifications - for example, Rostelecom is working in this direction. The company signed an agreement on the construction of 5G networks in the Skolkovo innovation center. The implementation of the project is included in the state program "Digital Economy", recently approved by the government.