Cellular telephone connection. Tariffs for mobile communications. Maliciousness of cell towers

Cellular communications have recently become so firmly established in our daily lives that it is difficult to imagine modern society without it. Like many other great inventions, the mobile phone has greatly influenced our lives and many areas of it. It is difficult to say what the future would be like if it were not for this convenient type of communication. Probably the same as in the movie "Back to the Future 2", where there are flying cars, hoverboards, and much more, but no cellular communications!

But today, in a special report for, there will be a story not about the future, but about how modern cellular communications are structured and work.

In order to learn about the operation of modern cellular communications in the 3G/4G format, I invited myself to visit the new federal operator Tele2 and spent the whole day with their engineers, who explained to me all the intricacies of data transmission through our mobile phones.

But first I’ll tell you a little about the history of cellular communications.

The principles of wireless communication were tested almost 70 years ago - the first public mobile radiotelephone appeared in 1946 in St. Louis, USA. In the Soviet Union, a prototype of a mobile radiotelephone was created in 1957, then scientists in other countries created similar devices with different characteristics, and only in the 70s of the last century in America were the modern principles of cellular communication determined, after which its development began.

Martin Cooper - inventor of the portable prototype cell phone Motorola DynaTAC weighs 1.15 kg and measures 22.5x12.5x3.75 cm

If in Western countries by the mid-90s of the last century, cellular communications were widespread and used by most of the population, then in Russia it just began to appear, and became available to everyone a little over 10 years ago.

Bulky, brick-shaped mobile phones that worked in the first and second generation formats have become history, giving way to smartphones with 3G and 4G, better voice communications and high Internet speeds.

Why is the connection called cellular? Because the territory in which communication is provided is divided into separate cells or cells, in the center of which base stations (BS) are located. In each “cell” the subscriber receives the same set of services within certain territorial boundaries. This means that moving from one cell to another, the subscriber does not feel territorial attachment and can freely use communication services.

It is very important that there is continuity of connection when moving. This is ensured thanks to the so-called handover, in which the connection established by the subscriber is, as it were, picked up by neighboring cells in a relay race, and the subscriber continues to talk or delve into social networks.

The entire network is divided into two subsystems: the base station subsystem and the switching subsystem. Schematically it looks like this:

In the middle of the "cell", as mentioned above, there is a base station, which usually serves three "cells". The radio signal from the base station is emitted through 3 sector antennas, each of which is aimed at its own “cell”. It happens that several antennas of one base station are directed at one “cell”. This is due to the fact that the cellular network operates in several bands (900 and 1800 MHz). In addition, a given base station may contain equipment from several generations of communications (2G and 3G).

But Tele2 BS towers only have third and fourth generation equipment - 3G/4G, since the company decided to abandon old formats in favor of new ones that help avoid interruptions voice communication and provide a more stable Internet. Regulars of social networks will support me in the fact that nowadays Internet speed is very important, 100-200 kb/s is no longer enough, as it was a couple of years ago.

The most common location for a BS is a tower or mast built specifically for it. Surely you could see red and white BS towers somewhere far from residential buildings (in a field, on a hill), or where there are no tall buildings nearby. Like this one, which is visible from my window.

However, in urban areas it is difficult to find a place to place a massive structure. Therefore, in large cities, base stations are located on buildings. Each station picks up signals from mobile phones at a distance of up to 35 km.

These are antennas, the BS equipment itself is located in the attic, or in a container on the roof, which is a pair of iron cabinets.

Some base stations are located in places you wouldn't even guess. Like, for example, on the roof of this parking lot.

The BS antenna consists of several sectors, each of which receives/sends a signal in its own direction. If the vertical antenna communicates with phones, then the round antenna connects the BS to the controller.

Depending on the characteristics, each sector can handle up to 72 calls simultaneously. A BS can consist of 6 sectors and serve up to 432 calls, but usually fewer transmitters and sectors are installed at stations. Cellular operators, such as Tele2, prefer to install more BS to improve the quality of communication. As I was told, the most used here is modern equipment: Ericsson base stations, transport network - Alcatel Lucent.

From the base station subsystem, the signal is transmitted towards the switching subsystem, where a connection is established in the direction desired by the subscriber. The switching subsystem has a number of databases that store subscriber information. In addition, this subsystem is responsible for security. To put it simply, the switch is complete It has the same functions as the female operators who used to connect you with the subscriber with their hands, only now all this happens automatically.

The equipment for this base station is hidden in this iron cabinet.

In addition to conventional towers, there are also mobile versions of base stations located on trucks. They are very convenient to use during natural disasters or in crowded places (football stadiums, central squares) during holidays, concerts and various events. But, unfortunately, due to problems in legislation, they have not yet found wide application.

To ensure optimal radio signal coverage at ground level, base stations are designed in a special way, therefore, despite the range of 35 km. the signal does not extend to aircraft flight altitude. However, some airlines have already begun installing small base stations on their boards that provide cellular communications inside the aircraft. Such a BS is connected to a terrestrial cellular network using a 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, for example, turning off the voice on night flights.

I also looked into the Tele2 office to see how specialists monitor the quality of cellular communications. If a few years ago such a room would have been hung to the ceiling with monitors showing network data (load, network failures, etc.), then over time the need for so many monitors has disappeared.

Technologies have developed greatly over time, and such a small room with several specialists is enough to monitor the work of the entire network in Moscow.

Some views from the Tele2 office.

At a meeting of company employees, plans to capture the capital are discussed) From the beginning of construction until today, Tele2 has managed to cover all of Moscow with its network, and is gradually conquering the Moscow region, launching more than 100 base stations weekly. Since I now live in the region, it is very important to me. so that this network comes to my town as quickly as possible.

The company's plans for 2016 include providing high-speed communications in the metro at all stations; at the beginning of 2016, Tele2 communications are present at 11 stations: 3G/4G communications at the Borisovo metro station, " Business center", "Kotelniki", "Lermontovsky Prospekt", "Troparevo", "Shipilovskaya", "Zyablikovo", 3G: "Belorusskaya" (Koltsevaya), "Spartak", "Pyatnitskoye Shosse", "Zhulebino".

As I said above, Tele2 abandoned the GSM format in favor of third and fourth generation standards - 3G/4G. This allows you to install 3G/4G base stations with a higher frequency (for example, inside the Moscow Ring Road, BSs are located at a distance of about 500 meters from each other) to provide more stable communications and high speed mobile internet, which was not the case in networks of previous formats.

From the company’s office, I, in the company of engineers Nikifor and Vladimir, go to one of the points where they need to measure the communication speed. Nikifor stands in front of one of the masts on which communication equipment is installed. If you look closely, you will notice a little further to the left another such mast, with equipment from other cellular operators.

Oddly enough, cellular operators often allow their competitors to use their tower structures to place antennas (naturally on mutually beneficial terms). This is because building a tower or mast is an expensive proposition, and such an exchange can save a lot of money!

While we were measuring the communication speed, Nikifor was asked several times by passing grandmothers and uncles if he was a spy)) “Yes, we are jamming Radio Liberty!”

The equipment actually looks unusual; from its appearance one can assume anything.

The company’s specialists have a lot of work to do, considering that the company has more than 7 thousand in Moscow and the region. base stations: about 5 thousand of them. 3G and about 2 thousand. LTE base stations, and recently the number of base stations has increased by about a thousand.
In just three months, 55% of the total number of new operator base stations in the region were put on air in the Moscow region. Currently, the company provides high-quality coverage of the territory where more than 90% of the population of Moscow and the Moscow region lives.
By the way, in December, Tele2’s 3G network was recognized as the best in quality among all capital operators.

But I decided to personally check how good Tele2’s connection is, so I bought a SIM card in the nearest shopping center on Voykovskaya metro station, with the simplest tariff “Very Black” for 299 rubles (400 SMS/minutes and 4 GB). By the way, I had a similar Beeline tariff, which was 100 rubles more expensive.

I checked the speed without going far from the cash register. Reception - 6.13 Mbps, transmission - 2.57 Mbps. Considering that I am standing in the center of a shopping center, this is a good result; Tele2 communication penetrates well through the walls of a large shopping center.

At metro Tretyakovskaya. Signal reception - 5.82 Mbps, transmission - 3.22 Mbps.

And on metro station Krasnogvardeyskaya. Reception - 6.22 Mbps, transmission - 3.77 Mbps. I measured it at the exit of the subway. If you take into account that this is the outskirts of Moscow, it’s very decent. I think that the connection is quite acceptable, we can confidently say that it is stable, considering that Tele2 appeared in Moscow just a couple of months ago.

There is a stable Tele2 connection in the capital, which is good. I really hope that they will come to the region as soon as possible and I will be able to take full advantage of their connection.

Now you know how cellular communication works!

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cellular

cellular, mobile network- one of the types of mobile radio communications, which is based on cellular network. Key Feature lies in the fact that the total coverage area is divided into cells (cells), determined by the coverage areas of individual base stations (BS). The cells partially overlap and together form a network. On an ideal (flat and undeveloped) surface, the coverage area of ​​one BS is a circle, so the network made up of them looks like a honeycomb with hexagonal cells (honeycombs).

The network consists of spatially dispersed transceivers operating in the same frequency range, and switching equipment that makes it possible to determine the current location of mobile subscribers and ensure 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 telephone radio in the United States dates back to 1921: Detroit police used one-way dispatch communications in the 2 MHz band to transmit information from a central transmitter to vehicle-mounted receivers. In 1933, the NYPD 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 it had completely replaced amplitude modulation. The first public mobile radiotelephone appeared in 1946 (St. Louis, USA; Bell Telephone Laboratories), it used the 150 MHz band. In 1955, an 11-channel system began operating in the 150 MHz band, and in 1956, a 12-channel system in the 450 MHz band began operating. 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, 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 device, weighing 0.5 kg and the size of a cigarette box. In the 1960s Hristo Bochvarov in Bulgaria demonstrates his prototype of a pocket mobile radiotelephone. At the Interorgtekhnika-66 exhibition, Bulgaria is presenting a kit for organizing local mobile communications from pocket mobile phones RAT-0.5 and ATRT-0.5 and a base station RATC-10, providing connection for 10 subscribers.

At the end of the 50s in the USSR, the development of the Altai car radiotelephone system began, 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 the 330 MHz range was allocated for it.

In a similar way, with natural differences and on a smaller scale, the situation developed in other countries. Thus, in Norway, public telephone radio has been used for maritime mobile communications since 1931; in 1955 there were 27 coast radio stations in the country. Ground mobile connection began to develop after the Second World War in the form of private networks with manual switching. Thus, by 1970, mobile telephone radio communications, on the one hand, had already become quite widespread, but on the other, it clearly could 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 due to reuse frequencies in a system with a cellular structure.

Cellular systems

Certain 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 when users manually switched channels at predetermined locations. However, the architecture of what is now known as the cellular communications system was not outlined until the Bell System technical report submitted to the FCC in December 1971. From this time on, the development of cellular communications itself began.

In 1974, the US Federal Communications Commission decided to allocate a frequency band of 40 MHz in the 800 MHz band for cellular communications; in 1986 another 10 MHz was added in the same range. In 1978, tests of the first experimental cellular communication system for 2 thousand subscribers began in Chicago. Therefore, 1978 can be considered the year of the beginning of the practical use of cellular communications. The first automated commercial cellular telephone system was introduced in Chicago in October 1983 by American Telephone and Telegraph (AT&T). In Canada, cellular communications have been used since 1978, in Japan - since 1979, in northern European countries (Denmark, Norway, Sweden, Finland) - since 1981, in Spain and England - since 1982. As of July 1997 cellular communications operated in more than 140 countries on 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 1971, it reached 100% coverage in Finland in 1978, and in 1986 it had more than 30 thousand subscribers. The network operated at a frequency of 150 MHz, the cell size was about 30 km.

Operating principle of cellular communication

Main components cellular network- These are cell phones and base stations that are usually located on the roofs of buildings and towers. When turned on, the cell phone listens to the airwaves, finding a signal from the base station. The phone then sends its unique identification code to the station. The telephone and the station maintain constant radio contact, periodically exchanging packets. Communication between the phone and the station can be via 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 from the service cell deteriorates), it establishes communication with another one. handover).

Cellular networks can consist of base stations of different standards, which allows optimizing network operation and improving its coverage.

The 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 enter into roaming agreements among themselves. Thanks to such agreements, a 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 carried out at increased rates. The possibility of roaming appeared only in 2G standards and is one of the main differences from 1G networks.

The head of the Regional Journalism Club, Irina Yasina, recalls:

By July 1997, the total number of subscribers in Russia was about 300 thousand. As of 2007, the main cellular communication protocols used in Russia are GSM-900 and GSM-1800. In addition, CDMA networks also operate in the CDMA-2000 standard, also known as IMT-MC-450. GSM operators are also making a smooth transition to the UMTS standard. In particular, the first fragment of a network of this standard in Russia was put into operation on October 2, 2007 in St. Petersburg by MegaFon.

IDC based on research Russian market cellular communications concluded that in 2005, the total duration of calls on a cell phone by residents of the Russian Federation reached 155 billion minutes, and text messages 15 billion units were shipped.

According to data from 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 among the G8 countries.

In December 2007, the number of cellular users in Russia increased to 172.87 million subscribers, in Moscow - to 29.9, in St. Petersburg - to 9.7 million. Penetration level in Russia - up to 119.1%, Moscow - 176%, St. Petersburg - 153%. In December 2011, the penetration level in Russia was up to 156%, Moscow - 212.1%, St. Petersburg - 215.6%. 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 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. This figure is due to the lack subscription fee on popular tariff plans at Russian operators cellular communications and low cost of network connection. In some cases, subscribers have SIM cards from different operators, but may not use them for a long time, or use one SIM card in a business mobile phone and the other for personal conversations.

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

The penetration level at the end of 2009 reached 162.4%.

As of April 2010, market share in Russia by subscribers: MTS - 32.9%, MegaFon - 24.6%, VimpelCom - 24.0%, Tele2 - 7.5%, other operators - 11.0%

Cellular services

Mobile operators provide the following services:

• Voice call;
• Caller ID (Automatic Caller ID) and Anti-Caller ID;
• Reception and transmission of multimedia messages - images, melodies, videos (MMS service);
• Access to the Internet ;
• Video call and video conference

see also

Notes

Links

• The basis of a cellular network - how base stations are built - review article on the website 3Dnews.ru (Russian)
• Cellular Communications Control Center - a view from the inside - review article on the website 3Dnews.ru (Russian)
• MAIN INDICATORS OF THE DEVELOPMENT OF PUBLIC TELEPHONE COMMUNICATIONS AND MOBILE COMMUNICATIONS (at the end of 2009)

cellular in Russia
Operators
...virtual
Sales networks
Standards

Wikimedia Foundation. 2010.

See what “Cellular communications” is in other dictionaries:

- (English cellular phone, mobile radio relay communication), a type of radiotelephone communication in which the end devices, mobile phones (see MOBILE PHONE) are connected to each other using a cellular network of a set of special transceivers... ... encyclopedic Dictionary

One of the types of mobile radio communications, which is based on a 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). Honeycombs partially... ... Dictionary of business terms

Third generation cellular communications- Third generation cellular networks (3rd Generation, or 3G) operate at frequencies in the range of about 2 gigahertz and provide data transmission at speeds of up to 2 megabits per second. Such characteristics allow you to use a mobile phone in... ... Encyclopedia of Newsmakers

LLC "Ekaterinburg 2000" Type Cellular operator Location... Wikipedia

The article contains errors and/or typos. It is necessary to check the content of the article for compliance with the grammatical norms of the Russian language... Wikipedia

Communication is called mobile if the source of information or its recipient (or both) move in space. Radio communication has been mobile since its inception. Above, in the third chapter, it is shown that the first radio stations were intended for communication with moving 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 it was possible to save this ship, lost in the ice of the Baltic Sea. However, in those years, this “mobile communication” required bulky radio transceiver devices, which did not contribute to the development of much-needed individual radio communications even in the Armed Forces, not to mention private clients.

On June 17, 1946, in St. Louis, USA, telephone business leader AT&T and Southwestern Bell launched the first radiotelephone network for private customers. The elemental 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 sources was 40 kg. Despite this, the popularity of mobile communications began to grow rapidly. This created a new problem, more serious than weight and size indicators. An increase in the number of radios, 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 one-hundred-kilometer separation in space between two groups of radio systems. That is why mobile communications were mainly used for the needs of special services. For mass implementation, it was necessary to change not only the weight and size indicators, but also the very principle of organizing communication.

As noted above, in 1947 a transistor was invented that performs the functions of vacuum tubes, but has a significantly smaller size. It was the advent of transistors that was of great importance for the further development of radiotelephone communications. The replacement of vacuum tubes with transistors created the preconditions for the widespread introduction of mobile phones. The main limiting factor was the principle of communication organization, which would eliminate or at least reduce the influence of mutual interference.

Studies of the ultrashort wave range, carried out in the 40s of the last century, revealed its main advantage over short waves - wide range, i.e. large frequency capacity and the main disadvantage - strong absorption of radio waves by the propagation medium. Radio waves in this range are not capable of bending around the earth's surface, so the communication range was provided only on the line of sight, and depending on the power of the transmitter, a maximum of 40 km was provided. This disadvantage soon turned into an advantage, which gave impetus to the active mass introduction of cellular telephone communications.

In 1947, an employee of the American company Bell Laboratories D. Ring proposed a new idea for organizing communications. It consisted of dividing space (territory) into small areas - cells (or cells) with a radius of 1–5 kilometers and separating radio communications within one cell (by rationally repeating the communication frequencies used) from communications between cells. Frequency repetition has significantly reduced the problems of using frequency resources. 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 basic receiving and transmitting radio station, which would provide radio communication within the cell with all subscribers. Cell sizes were determined by the maximum radio communication range telephone set with a base station. This maximum range is called the cell radius. During a conversation, the cellular radiotelephone is connected to the base station by a radio channel through which it transmits phone conversation. Each subscriber must have his own microradio station - a “mobile phone” - a combination of a telephone, a transceiver and a mini-computer. Subscribers communicate with each other through base stations, which 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, the central part of the mobile communication system is computers. They find a subscriber located 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 a “foreign” cellular network to “their” network. This happens at the moment when the “foreign” subscriber finds itself in the coverage area of ​​the new base station. Thus, roaming is carried out (which in English means “wandering” or “wandering”).

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 communication systems was difficult. Therefore, the practical use of cellular communications became possible only after the invention of microprocessors and integrated semiconductor chips.

The first cellular telephone, a prototype of a modern device, was designed by Martin Cooper (Motorola, USA).

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

On April 3, 1973, Martin Cooper dialed his boss and said the following words: “Imagine, Joel, that I am calling you from the world's first cell phone. I have it in my hands, and I’m walking down a New York street.”

The phone Martin called from was called Dyna-Tac. Its dimensions were 225x125x375 mm, and its weight was no less than 1.15 kg, which, however, is much less than the 30 kilogram devices of the late forties. Using the device, it was possible to make calls and receive signals, and negotiate with the subscriber. This telephone had 12 keys, of which 10 were digital for dialing the subscriber's number, and the other two ensured the start of a conversation and interrupted the call. Dyna-Tac batteries allowed talk time for about half an hour, and required 10 hours to charge.

Although much 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 band served 250 subscribers.

A little later, cellular communications began their triumphal march throughout the world. More and more countries realized the benefits and convenience it could bring. However, the lack of a unified international standard for the use of the frequency range eventually led to the fact that the owner of a cell phone, moving from one state to another, could not use the mobile phone.

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

In 1983, a network of the AMPS (Advanced Mobile Phone Service) standard, which was developed by Bell Laboratories, was launched in Chicago. 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 the sharply increased number of subscribers, the HTACS (Enhanced TACS) standard was adopted, adding new frequencies and partially correcting the shortcomings of its predecessor. France stood apart from everyone else and began using its own Radiocom-2000 standard in 1985.

The next standard was NMT-900, using frequencies 900 MHz range. A new version came into use 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 (FM) 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 of other subscribers and the inability to combat signal fading when the subscriber moves, as well as under the influence of the terrain and buildings. Congestion frequency ranges caused interference during conversations. Therefore, by the end of the 1980s, the creation of the second generation of cellular communication systems began, based on digital signal processing methods.

Previously, in 1982, the European Conference of Postal and Telecommunications Administrations (CEPT), uniting 26 countries, decided to create a special group Groupe Special Mobile. Its goal was to develop a single European standard digital cellular communication. The new communication standard was developed over the course of eight years, and was first announced only in 1990 - then the standard specifications 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 throughout the world, it was decided to allocate the 1800 MHz band for the new standard.

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

The first country to launch the GSM network is Finland, which launched this standard into commercial operation in 1992. The following year, the first DCS-1800 One-2-One network went live in the UK. From this moment on, the global spread of the GSM standard throughout the world begins.

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

In general, there were many communication standards, and by the mid-nineties, most civilized countries were smoothly switching to digital specifications. If the first generation networks allowed the transmission of only voice, then the second generation of cellular communication systems, which is GSM, allows the provision of other non-voice services. In addition to the SMS service, the first GSM phones made it possible to transmit other non-voice data. For this purpose, a data transfer protocol was developed, called CSD (Circuit Switched Data - data transfer over switched lines). However, this standard had very modest characteristics - the maximum data transfer rate was only 9600 bits per second, and then only under the condition of stable communication. However, such speeds were quite enough for transmitting a fax 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 satisfy 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 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 sizes display, low performance of telephone processors and low data transfer rates in mobile networks. However, this protocol did not allow viewing standard Internet pages; they had to be written in WML, which was adapted for cell phones. As a result, although subscribers of cellular networks received access to the Internet, it turned out to be very “stripped down” and uninteresting. Plus, to access WAP sites, the same communication channel was used as for voice transmission, that is, while you are loading or viewing a page, the communication channel is busy, and with personal account The same money is debited as during the conversation. As a result, a rather interesting technology was practically buried for some time and was used very rarely by subscribers of cellular networks of various operators.
Cellular equipment manufacturers urgently had to look for ways to increase data transfer speeds, and as a result, HSCSD (High-Speed ​​Circuit Switched Data) technology was born, which provided quite acceptable speeds of up to 43 kilobits per second. This technology was popular among a certain circle of users. But still, this technology did not lose the main drawback of its predecessor - the data was still transmitted over the voice channel. The developers again had to engage in painstaking research. The efforts of the engineers were not in vain, and quite recently a technology came into being called GPRS (General Packed Radio Services) - 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 does not pay for the duration of the connection, but only for the amount of data transmitted and received. In addition, GPRS has another advantage over earlier mobile data technologies - during a GPRS connection, the phone is still able to receive calls and SMS messages. On this moment Modern phone models on the market pause the GPRS connection when making a call, which automatically resumes when the call ends. Such devices are classified as class B GPRS terminals. It is planned to produce class A terminals that will allow you to simultaneously download data and conduct a conversation with the interlocutor. There are also special devices that are designed only for data transmission, and they are called GPRS modems or class C terminals. Theoretically, 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 reach this speed up to 48 kilobits per second. This is primarily due to the equipment of the operators themselves and, as a consequence, the lack of cell phones on the market that support higher speeds.

With the advent of GPRS, we again remembered the WAP protocol, since now, through 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 network resources for a small monthly subscription fee.
With the advent of GPRS, cellular networks ceased to be called second generation networks - 2G. We are currently in the 2.5G era. Non-voice services are becoming increasingly popular as the cell phone, computer and Internet are merging. Developers and operators are offering us more and more different additional services.
Thus, using the capabilities of GPRS, it was created new format messaging, which was called MMS (Multimedia Messaging Service), which, unlike SMS, allows you to send not only text, but also various multimedia information from your cell phone, for example, sound recordings, photographs and even video clips. Moreover, an MMS message can be transferred either to another phone that supports this format or to an email account.
Increasing power of phone processors now allows you to download and run various programs. The Java2ME language is most often used to write them. Owners of the majority modern phones Now it’s easy to connect to the website of Java2ME application developers and download to your phone, for example, a new game or another the necessary program. Also, no one will be surprised by the ability to connect the phone to personal computer, in order to, using a special software, most often supplied with the handset, save or edit on a PC address book or organizer; while on the road, using a mobile phone + laptop combination, access the full Internet and view your email. However, our needs are constantly growing, the volume transmitted information grows almost daily. And more and more demands are being placed on cell phones, as a result of which the resources of current technologies are becoming insufficient to satisfy our increasing demands.

It is precisely to solve these requests that the fairly recently created third generation 3G networks are designed, in which data transmission dominates over voice services. 3G is not a communication standard, but a general name for all high-speed cellular networks that will grow and are already growing beyond the existing ones. Huge data transfer rates allow you to transfer high-quality video images directly to your phone and maintain a constant connection to the Internet and local networks. The use of new, improved security systems makes it possible today to use a telephone 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. Current integration various types communications (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 even science fiction writers today are unlikely to be able to tell how this evolutionary development will end.

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

mobile connection- this is radio communication between subscribers, the location of one or more of which changes. One type of mobile communication is cellular communication.

cellular- one of the types of radio communications, which is based on a cellular network. Key Feature: The total coverage area is divided into cells determined by coverage areas base stations. The cells overlap and together form a network. On an ideal surface, the coverage area of ​​one base station is a circle, so the network made up of them looks like cells with hexagonal cells.

Operating principle of cellular communication

So, first, let's look at how a call is made on a mobile phone. As soon as the user dials a number, the handset (HS - Hand Set) begins searching for the nearest base station (BS - Base Station) - the transceiver, control and communication equipment that makes up the network. It consists of a base station controller (BSC - Base Station Controller) and several repeaters (BTS - Base Transceiver Station). Base stations are controlled by a mobile switching center (MSC - Mobile Service Center). Thanks to the cellular structure, repeaters cover the area with a reliable reception area in one or more radio channels with an additional service channel through which synchronization occurs. More precisely, the exchange protocol between the device and the base station is agreed upon by analogy with the modem synchronization procedure (handshacking), during which the devices agree on the transmission speed, channel, etc. When the mobile device finds a base station and synchronization occurs, the base station controller forms a full-duplex link to the mobile switching center through the fixed network. The center transmits information about the mobile terminal to four registers: the Visitor Layer Register (VLR), the Home Register Layer (HRL), and the Subscriber or Authentication Register (AUC). and equipment identification register (EIR - Equipment Identification Register). This information is unique and is located in the plastic subscription box. microelectronic telecard or module (SIM - Subscriber Identity Module), which is used to check the subscriber’s eligibility and tariffication. Unlike landline phones, for the use of which you are charged depending on the load (the number of busy channels) coming through a fixed subscriber line, the fee for using mobile communications is not charged from the telephone used, but from the SIM card, which can be inserted into any apparatus.

The card is nothing more than a regular flash chip, made using smart technology (SmartVoltage) and having the necessary front end. It can be used in any device, and the main thing is that the operating voltage matches: early versions used a 5.5V interface, while modern cards usually have 3.3V. The information is stored in the standard of a unique international subscriber identifier (IMSI - International Mobile Subscriber Identification), which eliminates the possibility of "doubles" - even if the card code is accidentally selected, the system will automatically exclude the fake SIM, and you will not have to subsequently pay for other people's calls. When developing the cellular communication protocol standard, this point was initially taken into account, and now each subscriber has its own unique and only identification number in the world, encoded during transmission with a 64-bit key. In addition, by analogy with scramblers designed to encrypt/decrypt conversations in analogue telephony, 56-bit coding is used in cellular communications.

Based on this data, the system’s idea of ​​the mobile user is formed (his location, status on the network, etc.) and the connection occurs. If during a conversation a mobile user moves from the coverage area of ​​one repeater to the coverage area of ​​another, or even between the coverage areas of different controllers, the connection is not interrupted or deteriorated, since the system automatically selects the base station with which the connection is better. Depending on the channel load, the phone selects between a 900 and 1800 MHz network, and switching is possible even during a conversation, completely unnoticed by the speaker.

A call from a regular telephone network to a mobile user is made in the reverse order: first, the location and status of the subscriber are determined based on constantly updated data in the registers, and then the connection and communication are maintained.

Mobile radio communication systems are built according to a point-multipoint scheme, since the subscriber can be located at any point in the cell controlled by the base station. In the simplest case of circular transmission, the power of a radio signal in free space theoretically decreases in inverse proportion to the square of the distance. However, in practice, the signal attenuates much faster - in the best case, proportional to the cube of the distance, since the signal energy can be absorbed or reduced by various physical obstacles, and the nature of such processes strongly depends on the transmission frequency. When the power decreases by an order of magnitude, the covered area of ​​the cell decreases by two orders of magnitude.

"PHYSIOLOGY"

The most important reasons for increased signal attenuation are shadow areas created by buildings or natural elevations in the area. Studies of the conditions for the use of mobile radio communications in cities have shown that even at very close distances, shadow zones provide attenuation of up to 20 dB. Another important cause of attenuation is tree foliage. For example, at a frequency of 836 MHz in the summer, when the trees are covered with leaves, the received signal level is approximately 10 dB lower than at the same place in the winter, when there are no leaves. The fading of signals from shadow zones is sometimes called slow in terms of the conditions for their reception in motion when crossing such a zone.

An important phenomenon that has to be taken into account when creating cellular mobile radio communication systems is the reflection of radio waves, and, as a consequence, their multipath propagation. On the one hand, this phenomenon is useful, since it allows radio waves to bend around obstacles and propagate behind buildings, in underground garages and tunnels. But on the other hand, multipath propagation gives rise to such difficult problems for radio communications as extended signal delay, Rayleigh fading and worsening of the Doppler effect.

Signal delay stretching occurs due to the fact that a signal passing along several independent paths of different lengths is received several times. Therefore, a repeated pulse can go beyond the time interval allotted for it and distort the next character. Distortion caused by extended delay is called intersymbol interference. At short distances, the extended delay is not dangerous, but if the cell is surrounded by mountains, the delay can extend for many microseconds (sometimes 50-100 μs).

Rayleigh fading is caused by the random phases with which the reflected signals arrive. If, for example, the direct and reflected signals are received in antiphase (with a phase shift of 180°), then the total signal can be attenuated almost to zero. Rayleigh fading for a given transmitter and a given frequency is something like amplitude “dips” that have different depths and are distributed randomly. In this case, with a stationary receiver, fading can be avoided simply by moving the antenna. When a vehicle is moving, thousands of such “dips” occur every second, which is why the resulting fading is called fast.

The Doppler effect manifests itself when the receiver moves relative to the transmitter and consists of a change in the frequency of the received oscillation. Just as the pitch of a moving train or car appears slightly higher to a stationary observer as the vehicle approaches and slightly lower as it moves away, the frequency of a radio transmission shifts as the transceiver moves. Moreover, with multipath signal propagation, individual rays can produce a frequency shift in one direction or another at the same time. As a result, due to the Doppler effect, random frequency modulation of the transmitted signal is obtained, just as random amplitude modulation occurs due to Rayleigh fading. Thus, in general, multipath propagation creates great difficulties in organizing cellular communications, especially for mobile subscribers, which is associated with slow and fast fading of the signal amplitude in a moving receiver. These difficulties were overcome with the help of digital technology, which made it possible to create new methods of coding, modulation and equalization of channel characteristics.

"ANATOMY"

Data transmission is carried out via radio channels. GSM network operates in the 900 or 1800 MHz frequency bands. More specifically, for example, in the case of considering the 900 MHz band, the mobile subscriber unit transmits on one of the frequencies lying in the range 890-915 MHz, and receives on a frequency lying in the range 935-960 MHz. For other frequencies the principle is the same, only the numerical characteristics change.

By analogy with satellite channels The direction of transmission from the subscriber unit to the base station is called upstream (Rise), and the direction from the base station to the subscriber unit is called downstream (Fall). In a duplex channel consisting of upstream and downstream transmission directions, frequencies differing by exactly 45 MHz are used for each of these directions. In each of the above frequency ranges, 124 radio channels are created (124 for receiving and 124 for transmitting data, spaced at 45 MHz) with a width of 200 kHz each. These channels are assigned numbers (N) from 0 to 123. Then the frequencies of the upstream (F R) and downstream (F F) directions of each channel can be calculated using the formulas: F R (N) = 890+0.2N (MHz), F F (N) = F R (N) + 45 (MHz).

Each base station can be provided with from one to 16 frequencies, and the number of frequencies and transmission power are determined depending on local conditions and load.

In each of the frequency channels, which is assigned a number (N) and which occupies a 200 kHz band, eight time division channels (time channels with numbers from 0 to 7), or eight channel intervals, are organized.

The frequency division system (FDMA) allows you to get 8 channels of 25 kHz, which, in turn, are divided according to the principle of the time division system (TDMA) into another 8 channels. GSM uses GMSK modulation and the carrier frequency changes 217 times per second to compensate for possible quality degradation.

When a subscriber receives a channel, he is allocated not only a frequency channel, but also one of the specific channel slots, and he must transmit in a strictly allotted time interval, without going beyond it - otherwise interference will be created in other channels. In accordance with the above, the transmitter operates in the form of individual pulses, which occur in a strictly designated channel interval: the duration of the channel interval is 577 μs, and the duration of the entire cycle is 4616 μs. Allocation to the subscriber of only one of the eight channel intervals allows the process of transmission and reception to be divided in time by shifting the channel intervals allocated to the transmitters of the mobile device and the base station. The base station (BS) always transmits three timeslots before the mobile unit (HS).

The requirements for the characteristics of a standard pulse are described in the form of a normative pattern of changes in radiation power over time. The processes of turning the pulse on and off, which are accompanied by a change in power by 70 dB, must fit into a time period of only 28 μs, and the working time during which 147 binary bits are transmitted is 542.8 μs. The transmission power values ​​​​indicated in the table earlier refer specifically to the pulse power. The average power of the transmitter turns out to be eight times less, since the transmitter does not radiate 7/8 of the time.

Let's consider the format of a normal standard pulse. It shows that not all discharges carry useful information: Here, a 26-bit training sequence is placed in the middle of the pulse to protect the signal from multipath interference. This is one of eight special, easily recognizable sequences in which the received bits are correctly positioned in time. Such a sequence is fenced with single-bit pointers (PB - Point Bit), and on both sides of this training sequence there is useful encoded information in the form of two blocks of 57 binary bits, fenced, in turn, with boundary bits (BB - Border Bit) - 3 bits each each side. Thus, a pulse carries 148 bits of data, which takes up a 546.12 µs time interval. To this time is added a period equal to 30.44 μs of protective time (ST - Shield Time), during which the transmitter is “silent”. In terms of duration, this period corresponds to the time of transmission of 8.25 bits, but no transmission occurs at this time.

The sequence of pulses forms a physical transmission channel, which is characterized by a frequency number and a time channel slot number. Based on this sequence of pulses, a whole series of logical channels are organized, which differ in their functions. In addition to channels transmitting useful information, there are also a number of channels transmitting control signals. The implementation of such channels and their operation require precise management, which is implemented by software.

Connection? This is a system that uses a large number of low-power wireless transmitters to create cells - the main geographic coverage area of ​​a wireless system. wired communication. Variable power levels allow cell sizes to be tailored to subscriber density and region-specific needs.

As mobile users move from cell to cell, their conversations are “handed off” between these zones to ensure uninterrupted service. Channels (frequencies) used in one such unit can be reused in another at some distance.

Cellular refers to Advanced Mobile Phone Service (AMPS), which divides a geographic region into sections called cells. The purpose of this division is to make maximum use of the limited number of transmission frequencies.

Cellular communication is a form of communication technology that enables the use of mobile phones.

A mobile phone is a two-way radio that allows simultaneous transmission and reception.

Based on the geographical division of the communication coverage area. Each cell is allocated a certain amount of frequencies (or channels) that allow a large number of subscribers to simultaneously carry on conversations.

A common element of all generations of mobile communication technologies is the use of certain radio frequencies (RF), as well as the reuse of frequencies. This makes it possible to provide services to a large number of subscribers while simultaneously reducing the number of channels (bandwidth). It also allows for the creation of wide networks, fully integrating the advanced capabilities of the mobile phone.

Increased demand and consumption, as well as the development of various types of services, have accelerated the rapid technological development of modern networks, as well as the continuous improvement of the cellular devices.

How mobile communication works

Each mobile phone uses a separate temporary radio channel to communicate with the cell site. This site supports communication with many phones simultaneously, using one channel per phone. The channels use a couple of cellular frequencies:

1. Direct line for transmission from a cell site.
2. A reverse line so that the cell site can receive calls from users.

Radio energy dissipates over distance, so cell phones must remain close to the base station to maintain communication. Basic structure mobile networks includes telephone systems and radio communication services.

How cellular communications work (for dummies)

The process begins by activating the chip by entering the PIN code of the inserted SIM card. Then the cellular signal is transmitted via control channels. The answer from the called number is sent via free channel control to the base station antenna, from where transmission occurs to the mobile switching center.

The switching center searches for the base station with the maximum signal strength of the cellular subscriber's cell phone and switches the conversation to it.

Early telephone system architecture

Traditional mobile service was structured similarly to television radio broadcasting: one very powerful transmitter, located at the highest point in the region, would broadcast over a radius of up to fifty kilometers.

The cellular concept structured the telephone network differently. Instead of using a single high-power transmitter, many low-power transmitters were placed throughout the cellular coverage area.

For example, by dividing an area into one hundred different areas (cells) with low-power transmitters using twelve conversations (channels), the system capacity could theoretically be increased from twelve conversations or voice channels using one high-power transmitter to twelve hundred conversations (channels). ), using hundreds of low-power transmitters.

The urban area is configured as a traditional mobile phone network with a single high-power transmitter.

Mobile communication system using cellular concept

Interference problems caused by mobile devices using the same channel in adjacent areas have proven that all channels cannot be reused in every cell. Although this affected the effectiveness of the original concept, frequency reuse has become a viable solution to the problems of mobile telephony systems.

Engineers discovered that the impact of interference was not related to the distance between zones, but to the ratio of the distance to the power (radius) of the zones' transmitters. By reducing the zone radius by fifty percent, service providers can increase the number potential clients in the zone four times.

Systems based on areas with a radius of one kilometer will have one hundred times more channels than systems with areas within a radius of ten kilometers. Speculation led to the conclusion that by reducing the zone radius to a few hundred meters, millions of calls could be handled.

The cellular concept uses variable low power levels, allowing cells to be selected according to subscriber density and the needs of a given area. As the population grows, cells can be added to accommodate this growth.

Cellular frequencies used in one cluster of cells can be reused in other cells. Conversations can be transferred from cell to cell to maintain constant telephone communication as the user moves between them.

Cellular radio equipment (base station) can communicate with mobile phones as long as they are within range. Radio energy dissipates over distance, so mobile phones must be within the operating range of the base station. Like the early mobile radio system, the base station communicates with mobile phones through a link.

A channel consists of two frequencies: one for transmitting to the base station and one for receiving information from the base station.

Cellular system architecture

Increased demand and low quality existing services encouraged suppliers mobile services Explore ways to improve the quality of service and support more users on your systems. Since the amount of frequency spectrum available for mobile cellular use was limited, efficient use of the required frequencies was necessary for communications coverage.

In modern cellular telephony, rural and urban areas are divided into districts according to specific service rules. Deployment parameters, such as number of divisions and cell sizes, are determined by engineers experienced in cellular system architecture.

Provision for each region is planned according to an engineering plan that includes cells, clusters, frequency reuse and handover.

A cell is the basic geographic unit of a cellular system. These are base stations that transmit signals across small geographic areas, which are represented as hexagons. The size of each varies depending on the landscape. Due to limitations imposed by natural terrain and man-made structures, the true shape of the cells is not a perfect hexagon.

A cluster is a group of cells. No channel is reused across the cluster.

Because only a small number of radio frequencies were available for mobile systems, engineers had to find a way to reuse radio channels to carry more than one conversation at a time. The industry's solution was called frequency scheduling or frequency reuse. Frequency reuse was realized by restructuring the mobile phone system architecture into a cellular concept.

Cellular standards are as follows: The concept of frequency reuse is based on assigning each cell a group of radio channels used within a small geographic area. Cells are assigned a channel group that is completely different from neighboring similar units. Their coverage area is called a fingerprint. This fingerprint is bounded by a boundary so that the same group of channels can be used in different cells that are far enough apart that their frequencies do not interfere.

Cells with the same number have the same set of frequencies. If the number of available frequencies is 7, the frequency reuse ratio is 1/7. That is, each cell uses 1/7 of the available cellular channels.

Obstacles in the development of cellular communications

Unfortunately, economic considerations made the concept of creating complete systems with many small areas. To overcome this difficulty, system operators developed the idea of ​​cell splitting. When a service area becomes crowded with users, this approach is used to divide one zone into smaller ones. In this way, urban centers can be broken down into as many areas as needed to provide an acceptable level of service in high-traffic areas, while larger, less expensive cells can be used to cover outlying rural areas.

The latest obstacle in the development of the cellular network stems from a problem that arose when a cellular subscriber moved from one cell to another during a call. Since adjacent areas do not share the same radio channels, a call must either be dropped or transferred from one radio channel to another when a user crosses the line between adjacent cells.

Because call drop is not acceptable, a handover process was created. Handover occurs when the mobile telephone network automatically transfers the call to another radio channel when mobile device intersects neighboring cells.

During a conversation, the two parties are on the same voice channel. When a mobile device leaves the coverage area of ​​a given cell site, reception becomes poor. At this point, the cell site being used requests handover. The system switches the call to a higher frequency channel at the new site without interrupting the call or alerting the user. The call continues as long as the user is talking and the caller does not notice the handover.

Cellular System Components

Cellular system offers mobile and portable telephone exchanges the same service as fixed exchanges over conventional wire loops. It is capable of serving tens of thousands of subscribers in a large metropolis. A cellular communications system consists of the following four main components that work together to provide mobile communications services to subscribers:

1. Telephone network public service network (PSTN).
2. Mobile telephone exchange(MTSO).
3. Cell site with antenna system.
4. Mobile subscriber unit (MSU).

PSTN consists of local networks, exchange area networks, and long-distance networks that connect phones and other communications devices around the world.

MTSO is the central office of mobile communications. It houses the communications switching center (MSC), field control and relay stations for switching calls from cell sites to wireline central offices (PSTN).

The term "cell site" is used to refer to the physical location of radio equipment that provides coverage in a cell. List hardware, located at the cell site, includes power supplies, interface equipment, radio frequency transmitters and receivers, and antenna systems.

The mobile subscriber unit consists of a control unit and a transceiver that transmits and receives radio transmissions to and from the cell site. Three types of MSU are available:

• Mobile phone (typical transmission power 4.0 W).
• Portable (typical transmit power 0.6 W).
• Transportable (typical transmission power is 1.6 W).

Maliciousness of cell towers

Cellular communications is a major breakthrough in the science and technology of its time, which was not without consequences. The cell phone industry continues to claim that cell towers pose no health risks, but fewer people believe this these days.

Are cell towers harmful? Unfortunately, the correct answer is yes. Microwaves can affect your body's electromagnetic fields, causing a variety of potential health problems:

1. Headache.
2. Memory loss.
3. Cardiovascular stress.
4. Low sperm count.
5. Birth defects.

There is compelling evidence that electromagnetic radiation from towers is harmful to health.

Example: A study on the effects of a cage tower on a dairy herd was carried out by the government of the state of Bavaria in Germany, the results were published in 1998. The construction of the tower caused adverse health effects, leading to a noticeable drop in milk production. The movement of cattle restored milk production. Moving them back to their original pasture recreated the problem.

Cellular communications in Russia

Of the 100 possible Russian cellular codes, 79 are in use and 21 are free. Free codes are in reserve and do not yet belong to any operator.

More than 80 cellular communication companies are registered in the Russian Federation and provide their services throughout the country. Mobile operators have telephone codes in 9xx format. ten digits and start with +79xx or 89xx.

To the very large operators include: MTS (" Mobile TeleSystems"), "Beeline" ("Vympel-Communications"), "MegaFon", "Tele2" (T2-Mobile). The Big Three operators (MTS, Beeline and MegaFon) own entire series of numbers.