All about cellular communication. The principle of cellular communication

Cellular communications are 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 gone through a number of revolutions. How did wireless communication begin, how cells work and what opportunities the new mobile standard will open 5G?

The first use of mobile telephone radio communications dates back to 1921, when Detroit police used one-way dispatcher communication in the 2 MHz band in the United States to transmit information from a central transmitter to receivers in police cars.

How cellular communication appeared

For the first time the idea of \u200b\u200bcellular communication was put forward in 1947 - worked on it by engineers from Bell Labs Douglas Ring and Ray Young. However, the real prospects for its implementation began to emerge only in the early 1970s, when the company's employees developed a working architecture for the cellular hardware platform.

For example, American engineers proposed to place transmitting stations not in the center, but at the corners of the "cells", and a little later a technology was invented that would allow subscribers to move between these "cells" without interrupting communications. After that, it remains to develop operating equipment for such a technology.

The problem was successfully solved by Motorola - 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 directly from the street and told him about his own successes.

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

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 $ 3995 - a fabulous sum for those times. Despite this, the mobile phone instantly became popular.

Why is the connection called cellular

The principle of mobile communication is simple - the territory where 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.

Usually 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 picks up 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 stations designed to serve a small area. They allow to dramatically improve coverage in places where it is needed. Cellular communications in Russia will be combined with space

The mobile phone in the network listens to the air and finds the signal of the base station. In addition to the processor and RAM, a modern SIM card has a unique key that allows you to log in to the cellular network. The phone can communicate with the station 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 landline telephone network. If the phone leaves the range of the base station, the device establishes communication with others - the connection established by the subscriber is invisibly 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 penetration. It is in it that most mobile networks now work.

What mobile communication standards are

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

The birth of 2G is related to 1991 - GSM (Global System for Mobile Communications) became the main standard of the new generation. This standard is still supported. Communication in this standard has become digital, it became 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 audio. The GPRS standard known as 2.5G was intended to solve the problem. For the first time, it allowed mobile phone owners to use the Internet.

Another difference of 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 increased repeatedly.

The most up-to-date standard is fourth-generation 4G communication, which is intended only for high-speed data services. The bandwidth of the 4G network is capable of reaching 300 Mbit / s, which gives the user almost unlimited opportunities to surf the Internet.

Cellular communication of the future

The 4G standard is sharpened for the continuous transfer of gigabytes of information, it does not even have a channel for voice transmission. Due to the 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 communication 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 connecting up to 100 billion devices to high-speed Internet.

It is 5G that will allow the true 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 start to constantly be in the global network and receive data on traffic conditions.

The low latency will ensure real-time communication between vehicles and infrastructure. A reliable and always-on connection is expected to open up the possibility for fully autonomous vehicles to run on the roads for the first time.

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 project is part of the state program "Digital Economy", recently approved by the government.

It's a little sad that the overwhelming majority of people answer the question: "How does cellular communication work?", Answer "by air" or in general - "I don't know."

In continuation of this topic, I had one funny conversation with a friend about the work of mobile communications. It happened exactly a couple of days before the event celebrated by all communications and telecom operators holiday "Radio Day".It so happened that due to his ardent position in life, my friend believed that mobile communication works without wires at all via satellite... Exclusively due to radio waves. At first, I could not convince him. But after a short conversation, everything fell into place.

After this friendly "lecture" the idea came up to write in simple language about how cellular communication works. Everything is as it is.

When you dial a number and start calling, well, or someone calls you, then your mobile phone communicates over the radiofrom one of the antennas of the nearest base station. Where are these base stations, you ask?

pay attention to industrial buildings, urban skyscrapers and special towers... On them are large gray rectangular blocks with protruding antennas of various shapes. But these antennas are not television or satellite, but transceivercellular operators. They are directed in different directions to provide communication to subscribers from all sides. After all, we do not know where the signal will come from and where it will bring the "unfortunate subscriber" with a telephone receiver? In professional jargon, antennas are also called "sectors". Typically, they are set from one to twelve.

From the antenna, the signal is transmitted via the cable directly to the control unit of the station... Together they form the base station [antennas and control unit]. Several base stations, whose antennas serve a separate territory, for example, a city district or a small town, are connected to a special block - controller... Up to 15 base stations are usually connected to one controller.

In turn, the controllers, which can also be several, are cabled to the "think tank" - switch... The switch provides output and input of signals to city telephone lines, to other mobile operators, as well as to long-distance and international operators.

In small networks, only one switch is used, in larger networks serving more than a million subscribers at once, two, three or more switches can be used, interconnected again by wires.

Why so much complexity? Readers will ask. It would seem, you can simply connect the antennas to the switch and everything will work... And then there are base stations, switches, a bunch of cables ... But, not everything is so simple.

When a person moves along the street on foot or by car, train, etc. while still talking on the phone, it is important to ensure continuity of communication. Communication workers call the process of handover in mobile networks by the term Handover.It is necessary to switch the subscriber's phone from one base station to another, from one controller to another, and so on in time.

If the base stations were directly connected to the switch, then all these switches would have to be managed by the switch... And he "poor" and so there is something to do. A multi-level network scheme makes it possible to evenly distribute the load on technical means... This reduces the likelihood of equipment failure and, as a result, loss of communication. Because we are all interestedin a seamless connection, right?

So, upon reaching the switch, our call is forwarded tofurther - to the network of another operator of mobile, city long-distance and international communications. Of course, this happens over high-speed cable communication channels. A call arrives at the switchanother operator. In this case, the latter "knows" in which territory [in the area of \u200b\u200baction, which controller] the required subscriber is now located. The switch transfers the phone call to a specific controller, which contains information about which base station the recipient of the call is located in. The controller sends a signal to this single base station, which in turn "polls", that is, calls the mobile phone. A tube starts ringing bizarrely.

This whole long and complex process in reality takes 2-3 seconds!

In the same way, phone calls are made to different cities in Russia, Europe and the world. For communication switches of various telecom operators use high-speed fiber-optic communication channels... Thanks to them, the telephone signal overcomes hundreds of thousands of kilometers in a matter of seconds.

Thanks to the great Alexander Popov for giving the world of radio! If not for him, perhaps we would now be deprived of many benefits of civilization.

Cellular communication has recently become so firmly established in our daily life 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 of its areas. It is difficult to say what the future would be like if it were not for this convenient form 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 connection!

But today in a special report for there will be a story not about the future, but about how modern cellular communication is arranged and works.

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

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

The principles of wireless communication were tried out 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 from other countries created similar devices with different characteristics, and only in the 70s of the last century in America the modern principles of cellular communication were determined, after which its development began.

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

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

Bulky brick-like mobile phones that worked in the first and second generation formats have gone down in history, giving way to smartphones with 3G and 4G, better voice communication and high Internet speed.

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 the 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 on the relay, and the subscriber continues to talk or dig in social networks.

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

In the middle of the "cell", as mentioned above, is the base station, which typically serves three "cells". The radio signal from the base station is radiated through 3 sector antennas, each of which is directed to its own "cell". It so happens that several antennas of one base station are directed to one "cell" at once. This is due to the fact that the cellular network operates in several bands (900 and 1800 MHz). In addition, this base station can have equipment of several generations of communication (2G and 3G) at once.

But on the BS Tele2 towers there is only third and fourth generation equipment - 3G / 4G, since the company decided to abandon old formats in favor of new ones, which help to avoid interruptions in 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 not enough anymore, as it was a couple of years ago.

The most common location for the BS is a tower or mast built specifically for it. Surely you could see the 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 that is visible from my window.

However, in urban areas it is difficult to find a place for a massive structure. Therefore, in large cities, base stations are located on buildings. Each station picks up a signal 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 where you would not even guess. Like on the roof of this parking lot.

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

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

From the base station subsystem, the signal is transmitted towards the switching subsystem, where the connection is established with the direction desired by the subscriber. The switching subsystem has a number of databases that store information about subscribers. In addition, this subsystem is responsible for security. Simply put, the switch is it has the same functions as the female operators who used to connect you with the subscriber by hand, 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 placed 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, because of problems in the legislation, they have not yet found wide application.

To ensure optimal radio coverage at ground level, base stations are designed in a special way, therefore, despite the range of 35 km. the signal does not apply to aircraft altitude. However, some airlines have already begun installing small base stations on their aircraft to 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 took a look at the Tele2 office to see how specialists control the quality of cellular communication. If a few years ago such a room would have been hung up to the ceiling with monitors showing network data (load, network failures, etc.), then over time the need for such a number of monitors has disappeared.

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

Few views from the Tele2 office.

At a meeting of the company's employees, plans are being discussed to capture the capital) From the beginning of construction until today, Tele2 has managed to cover the whole 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 plans for 2016 to provide high-speed communication in the metro at all stations, at the beginning of 2016 Tele2 communication is present at 11 stations: 3G / 4G communication on the Borisovo metro, Delovoy Tsentr, Kotelniki, Lermontovsky Prospekt , "Troparevo", "Shipilovskaya", "Zyablikovo", 3G: "Belorusskaya" (Koltsevaya), "Spartak", "Pyatnitskoe highway", "Zhulebino".

As I said above, Tele2 has abandoned the GSM format in favor of the third and fourth generation standards - 3G / 4G. This allows the installation of 3G / 4G base stations with a higher frequency (for example, within the Moscow Ring Road, BSs stand at a distance of about 500 meters from each other) in order to provide more stable communication and high speed of mobile Internet, which was not the case in the 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 opposite one of the masts on which communications equipment is installed. If you look closely, you will notice another such mast a little further to the left, with equipment from other cellular operators.

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

While we were measuring the speed of communication, Nikifor several times passers-by grandmothers and uncles asked if he was a spy)) "Yes, we are jamming Radio Liberty!).

The equipment actually looks unusual, from its appearance you can assume anything.

The specialists of the company have a lot of work, considering that in Moscow and the region the company has more than 7 thousand. base stations: of which about 5 thousand. 3G and about 2 thousand. base stations LTE, and recently the number of BS has increased by about a thousand more.
In just three months, 55% of the total number of new base stations of the operator in the region were put on the air in the Moscow region. At the moment, the company provides high-quality coverage of the territory where more than 90% of the population of Moscow and the Moscow region live.
By the way, in December the 3G Tele2 network was recognized as the best in quality among all metropolitan 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 "Very black" tariff for 299 rubles (400 SMS / minutes and 4 GB). By the way, I had a similar Beeline tariff, which is 100 rubles more expensive.

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

Tele2 has a stable 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!

If you have a production or service that you want to tell our readers about, write to me - Aslan ( [email protected] ) and we will make the best report that will be seen not only by the readers of the community, but also by the site http://ikaketosdelano.ru

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We remain in the access zone in non-standard situations.

There are many places in the world where a traditional smartphone with a Russian operator's SIM card does not work. This article will help you stay connected by answering three questions:

• How to find out which operators will work in the place where you are going
• How to choose an alternative to conventional mobile communications
• How to receive / send SMS via the Internet (and how to find it)

How to find out if it will catch 2G / 3G / 4G in place X (Russia)?

My life experience suggests that the coverage maps on the operators' sites are not always worth trusting. They sometimes embellish reality a little. How do you know if the phone will work 100% in the places you are going to travel to?

In January of this year, the Ministry of Telecom and Mass Communications took up the issue and created a service that displays information about the quality of signal reception by different operators. You can try it at geo.minsvyaz.ru.

The data is collected by volunteers. Any owner of an Android phone can become one if they install an application to monitor the quality of connection. On the map, you can compare four operators at the same time (choosing from 14). Lilac color indicates 4G coverage areas, green 3G, and orange 2G.

How to find out if it will catch 2G / 3G / 4G in place X (other countries)?

The Ministry of Telecom and Mass Communications is not the first who came up with such an application. For many years in a row, the research company Open Signal has been collecting information about communications in the same way.

Which phone to take around the world?

What to do if no cellular operators work in the place of interest? Be prepared to spend a little. For example, Fedor Konyukhov is always in touch. After all, he has several satellite phones.

The leader in this area is Iridium. Its coverage area is the entire planet. Prices for new phones start at 75 thousand rubles (the kit includes a charger with adapters for five sockets and a car antenna). A satellite router with the ability to connect no more than five devices will cost 65 thousand. You also need to pay directly for communication services: 1000 minutes of conversation / Internet access will cost 23,800 rubles.

Inmarsat has a slightly smaller coverage area. It will not work at the poles. Network equipment is marginally cheaper than Iridium.

Other operators offer phones from 25 thousand rubles and tariffs are more affordable. But before buying, you need to carefully check the coverage area with the map of your future travels, since in this parameter they lag behind the leaders. For example, Thuraya does not cover the huge (most interesting) northeastern part of Russia.

By the way, the provider just mentioned sells a very interesting thing - an attachment for the iPhone SatSteel (unfortunately, I found offers only for 4 and 4S), which allows you to use satellite communications on an Apple smartphone.

If none of those people with whom you are traveling on a trip have not yet bought a single satellite communication device, then you can save a lot by renting it.

In the absence of cellular communication, it is successfully replaced by the Internet.

How do I know if Wi-Fi is catching at X?

I have already written about the wigle.net service in the article. It has a quarter of a billion access points worldwide. You can see their location on the map.

It is interesting to see the statistics by country. Every fifth access point (53 million) is located in the United States. There are 2.5 million of them in Russia, while in Uzbekistan there are only 239 (I'm sure there are more in reality).

How do I know if there will be Wi-Fi on the plane?

On routehappy.com, you can check if there is Wi-Fi on board the flight you are going to fly (and also find out if you can charge your devices there and if the distance between the seats is great).

How to receive / send SMS online?

You know how to make free calls over the Internet without me. And send free messages to operators' sites too. Do you know how to receive SMS to a Russian number online?

This knowledge will come in handy if one day a site requires you to enter a confirmation code for registration, and you will be flying in an airplane or abroad, leaving your Russian SIM card at home. Or if you need another social network account, but you don't have a second phone.

Do you know what happens after you have dialed 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 the distant Easter Island? Why is the conversation sometimes interrupted unexpectedly? Last week I visited Beeline and tried to figure out how cellular communication works ...

A large area of \u200b\u200bthe 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 base station (BS) nearest to you via the service channel and asks to select a voice channel. The base station sends a request to the controller (BSC), and that forwards it to the switch (MSC). If your friend is a subscriber of the same cellular network, then the switch will check with the Home Location Register (HLR), find out where the called subscriber is at the moment (at home, in Turkey or in Alaska), and will transfer the call to the corresponding switch, where he is from. will forward to the controller and then to the Base Station. The Base Station will connect to your 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 turn to the corresponding switch of the other network.

Complicated? Let's take a closer look.

The Base Station is a pair of iron cabinets locked in a well-air-conditioned room. Considering that in Moscow it was +40 on the street, I wanted to live a little in this room. Typically, the Base Station is located either in the attic of a building or in a container on the roof:

2.

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

3.

Each sector can handle up to 72 calls simultaneously, depending on setup and configuration. A Base Station can have 6 sectors, so one Base Station can handle up to 432 calls, however, there are usually fewer transmitters and sectors installed on the station. Cellular operators prefer to install more base stations to improve the quality of communication.

The base station can operate in three bands:

900 MHz - the signal at this frequency travels further and better penetrates into buildings
1800 MHz - the signal spreads over shorter distances, but allows you to install more transmitters per sector
2100 MHz - 3G network

This is how a closet with 3G equipment looks like:

4.

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

5.

6.

A 900 MHz signal can hit up to 35 kilometers, although the "range" of some Base Stations along the routes can be up to 70 kilometers, by reducing the number of concurrently served subscribers at the station by half. Accordingly, our phone with its small built-in antenna can also transmit a signal over a distance of 70 kilometers ...

All Base Stations are designed to provide optimal RF coverage at ground level. Therefore, despite the range of 35 kilometers, the radio signal is simply not sent to the flight altitude of the aircraft. However, some airlines have already begun installing low-power base stations on their aircraft that provide coverage 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, 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 top 6 (by signal level) via the service channel, and the controller (BSC) decides which BS to transmit the current call (Handover) if you are on the move. Sometimes the phone can make a mistake and transfer you to the base station with the worst signal, in which case the conversation can be interrupted. It may also appear that all voice lines are busy at the Base Station that your phone has selected. In this case, the conversation will also be interrupted.

I was also told about the so-called "upper floors problem". If you live in a penthouse, sometimes, when moving from one room to another, the conversation can 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 located at a great distance from each other and are not registered as " neighboring "at the cellular 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 the 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 simultaneously. Usually this power is enough for the eyes, but, for example, during some holidays, the BS may not cope with the number of people who want to call. This usually happens on New Years, when everyone starts congratulating each other.

SMS are transmitted via service channels. On March 8 and February 23, people prefer to congratulate each other using SMS, sending funny rhymes, and the phones often cannot agree with the BS on the allocation of a voice channel.

I was told an interesting case. From one district of Moscow, subscribers began to receive complaints that they could not get through to anywhere. The technicians began to figure it out. Most of the voice lines were free, and all service lines were busy. It turned out that next to this BS there was an institute in which exams were being held and students constantly exchanged text messages.

The phone divides long SMS into several short ones and sends each one separately. The technical service staff advise sending such greetings 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:

7.

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 manages 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:

8.

9.

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

10.

11.

12.

The switch handles traffic control. Remember the old movies, where people first dialed to the "girl", and then she already connected them with another subscriber, poking wires? Modern switches do the same:

13.

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

14.

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

15.

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

16.

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

17.

There are 3 main areas of control over the cellular network: accidents, statistics and feedback from subscribers.

Just like in airplanes, all the equipment of the cellular network has sensors that send a signal to the CCS and output information to the dispatcher's computers. If some equipment is out of order, then the light on the monitor will start flashing.

The CSC 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 any of the nodes began to differ sharply from the previous indicators, then the light on the monitor will start flashing again.

Subscriber service operators receive feedback. If they cannot solve the problem, then the call is transferred to a technician. If he also turns out to be powerless, then an "incident" is created in the company, which is decided by the engineers who operate the corresponding equipment.

The switches are monitored by 2 engineers around the clock:

18.

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

19.

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

22.

21.

I understand that you still have a lot of questions about how the cellular network works. The topic is complex, and I asked a specialist from Beeline to help me respond to your comments. The only request is to stick to the theme. And questions like "Beeline radishes. They stole 3 rubles from my account" - address the subscriber service 0611.

Tomorrow there will be a post about how a whale jumped in front of me, but I did not have time to photograph it. Stay Tuned!