The principle of operation of GSM networks. How it is done, how it works, how it works

It is hardly possible today to find a person who would never use a cell phone. But does everyone understand how cellular communication works? How does something that we are all used to for a long time work and work? Are signals from base stations transmitted via wires or does it all work differently? Or maybe all cellular communication functions only due to radio waves? We will try to answer these and other questions in our article, leaving the description of the GSM standard outside its scope.

At the moment when a person tries to make a call from his mobile phone, or when they start calling him, the phone is connected via radio waves to one of the base stations (the most accessible), to one of its antennas. Base stations can be observed here and there, looking at the houses of our cities, at the roofs and facades of industrial buildings, at skyscrapers, and finally at the red and white masts specially erected for stations (especially along highways).

These stations look like rectangular boxes of gray color, from which various antennas (usually up to 12 antennas) stick out in different directions. The antennas here work both for reception and transmission, and they belong to the cellular operator. The base station antennas are directed to all possible directions (sectors) to provide “network coverage” to subscribers from all directions at a distance of up to 35 kilometers.

An antenna of one sector is able to simultaneously serve up to 72 calls, and if there are 12 antennas, then imagine: 864 calls can, in principle, serve one large base station at a time! Although usually limited to 432 channels (72 * 6). Each antenna is connected with a cable to the control unit of the base station. And already blocks of several base stations (each station serves its part of the territory) are connected to the controller. Up to 15 base stations are connected to one controller.

The base station, in principle, is capable of operating on three bands: the 900 MHz signal penetrates better into buildings and structures, spreads further, therefore this particular range is often used in villages and in the fields; the signal at a frequency of 1800 MHz does not spread so far, but more transmitters are installed in one sector, therefore, in cities such stations are more often installed; finally 2100 MHz is a 3G network.

There can be several controllers, of course, in a settlement or area, so the controllers, in turn, are connected by cables to the switch. The task of the switch is to connect the networks of mobile operators with each other and with city lines of ordinary telephone communication, long distance communication and international communication. If the network is small, then one switch is enough; if the network is large, two or more switches are used. Switches are interconnected by wires.

In the process of moving a person talking on a mobile phone down the street, for example: he walks, rides in public transport, or moves in a private car, his phone should not lose the network for a moment, the conversation should not be interrupted.

Continuity of communication is obtained due to the ability of a network of base stations to very quickly switch a subscriber from one antenna to another in the process of moving from the coverage area of \u200b\u200bone antenna to the coverage area of \u200b\u200banother (from cell to cell). The subscriber himself does not notice how he ceases to be associated with one base station, and is already connected to another, how he switches from antenna to antenna, from station to station, from controller to controller ...

At the same time, the switch provides optimal load distribution over a multi-layer network scheme to reduce the likelihood of equipment failure. A multi-level network is built like this: cell phone - base station - controller - switch.

Let's say we make a call, and now the signal has already reached the switchboard. The switch transfers our call to the destination subscriber - to the city network, to the international or long-distance communication network, or to the network of another mobile operator. All this happens very quickly using high-speed fiber optic cable channels.

Then our call goes to the switchboard, which is located on the side of the subscriber receiving the call (called by us). The "receiving" switch already has data on where the called subscriber is located, in which network coverage area: which controller, which base station. And so, the network polling starts from the base station, the addressee is found, and his phone “receives a call”.

The entire chain of described events, from the moment the number is dialed to the moment the call rang out on the receiving side, usually lasts no more than 3 seconds. So we can call anywhere in the world today.

Andrey Povny

In the theoretical part, we will not delve into the history of the creation of cellular communications, about its founders, the chronology of standards, etc. Who cares about it - there is plenty of material both in print media and on the Internet.

Let's consider what a mobile (cellular) phone is.

The figure shows a very simplified principle of operation:

Fig. 1 How a cell phone works

A cell phone is a transceiver operating at one of the frequencies in the range 850MHz, 900MHz, 1800MHz, 1900MHz. Moreover, the reception and transmission are separated in frequencies.

The GSM system consists of 3 main components, such as:

Base Station Subsystem (BSS - Base Station Subsystem);

Switching / switching subsystem (NSS –NetworkSwitchingSubsystem);

Operation and Maintenance Center (OMC);

In a nutshell, it works like this:

Cellular (mobile) phone interacts with a network of base stations (BS). BS towers are usually installed either on their ground masts, or on the roofs of houses or other structures, or on rented existing towers of all kinds of radio / TV repeaters, etc., as well as on high-rise pipes of boilers and other industrial structures.

After switching on, the phone monitors (listens, scans) the air for the presence of the GSM signal of its base station for the rest of the time. The phone determines the signal of its network by a special identifier. If there is one (the phone is within the coverage area of \u200b\u200bthe network), then the phone selects the best frequency in terms of signal strength and at this frequency sends the BS a request to register in the network.

The registration process is essentially an authentication (authorization) process. Its essence lies in the fact that each SIM card inserted into the phone has its own unique identifiers IMSI (International Mobile Subscriber Identity) and Ki (Key for Identification). These same IMSI and Ki are entered into the base of the Authentication Center (AuC) when the manufactured SIM-cards arrive to the telecom operator. When registering a phone in the network, the identifiers are transmitted to the BS, namely AuC. Then AuC (identification center) sends a random number to the phone, which is the key to perform calculations according to a special algorithm. This calculation takes place simultaneously in the mobile phone and the AuC, after which both results are compared. If they match, then the SIM card is recognized as genuine and the phone is registered in the network.

For a phone, the network identifier is its unique IMEI (International Mobile Equipment Identity) number. This number is usually 15 digits in decimal notation. For example 35366300/758647/0. The first eight digits describe the phone model and its origin. The rest are phone serial number and check number.

This number is stored in the phone's non-volatile memory. In outdated models, this number can be changed using special software (software) and an appropriate programmer (sometimes a data cable), and in modern phones it is duplicated. One copy of the number is stored in the memory area that can be programmed, and a duplicate - in the memory area OTP (One Time Programming), which is programmed by the manufacturer once and cannot be reprogrammed.

So, even if you change the number in the first memory area, the phone, when turned on, compares the data of both memory areas, and if different IMEI numbers are found, the phone is locked. Why change all this, you ask? In fact, the legislation of most countries prohibits this. Phone by IMEI number is tracked on the network. Accordingly, if a phone is stolen, it can be traced and seized. And if you manage to change this number to any other (work), then the chances of finding a phone are reduced to zero. These issues are dealt with by the special services with the appropriate assistance of the network operator, etc. Therefore, I will not delve into this topic. We are interested in the purely technical aspect of changing the IMEI number.

The fact is that, under certain circumstances, this number can be damaged as a result of a software failure or an incorrect update, and then the phone is absolutely unsuitable for use. This is where all the means come to the rescue to restore IMEI and the device's performance. This point will be discussed in more detail in the phone repair section.

Now, briefly about the transmission of voice from subscriber to subscriber in the GSM standard. In fact, this is a technically very complex process, which is completely different from the usual voice transmission over analog networks such as a home wired / radio telephone. Something remotely similar to digital DECT-radiotelephones, but the implementation is still different.

The fact is that the subscriber's voice undergoes many transformations before being broadcast. The analog signal is divided into 20 ms segments, after which it is converted into digital, after which it is encoded using encryption algorithms with the so-called. public key - the EFR system (Enhanced Full Rate - an advanced speech coding system developed by the Finnish company Nokia).

All codec signals are processed by a very useful algorithm based on the principle of DTX (Discontinuous Transmission). Its usefulness lies in the fact that it controls the transmitter of the phone, turning it on only at the moment when the pronunciation of speech begins and turns it off in the pauses between the conversation. All this is achieved using the included in the codec VAD (Voice Activated Detector) - a detector of speech activity.

For the received subscriber, all transformations occur in reverse order.

We all use mobile phones, but at the same time hardly anyone thinks - how do they work? In this article, we will try to figure out how, in fact, communication is implemented with respect to your mobile operator.

When you make a call to your interlocutor, or someone calls you, your phone connects over the radio channel to one of the antennas of the neighboring base station (BS, BS, Base Station).Each base station of cellular communication (in common people - cell towers) includes from one to twelve transceiver antennaswith directions in different directions in order to provide high-quality communication to subscribers within the radius of their operation. Specialists call such antennas in their own jargon "Sectors", which are gray rectangular structures that you can see almost every day on the roofs of buildings or special masts.

The signal from such an antenna goes through a cable directly to the control unit of the base station. The base station is a collection of sectors and a control block. In this case, a certain part of a settlement or territory is served by several base stations at once connected to a special block - local zone controller (abbreviated LAC, Local Area Controller or just "controller"). As a rule, one controller combines up to 15 base stations of a certain area.

For its part, controllers (there can also be several of them) are connected to the most important block - Mobile services Switching Center (MSC), which for ease of perception is usually called simply "Switch"... The switch, in turn, provides input and output to any communication lines - both cellular and wired.

If you display what is written in the form of a diagram, you get the following:
Small-scale GSM networks (usually regional) can use only one switch. Large ones, such as our operators of the "Big Three" MTS, Beeline or MegaFon, who simultaneously serve millions of subscribers, use several MSC devices connected to each other at once.

Let's see why such a complex system is needed and why it is impossible to connect the base station antennas to the switch directly? To do this, you need to talk about another term, called in technical language handover... It characterizes the handover of service in mobile networks on a relay basis. In other words, when you move along the street on foot or in a vehicle and talk on the phone, so that your conversation is not interrupted, you should promptly switch your device from one BS sector to another, from the coverage area of \u200b\u200bone base station or controller local zone to another, etc. Therefore, if the sectors of the base stations were directly connected to the switch, it would have to carry out this handover procedure for all its subscribers, and the switch already has enough tasks. Therefore, to reduce the likelihood of equipment failures associated with its overloads, the scheme for constructing GSM cellular networks is implemented according to a multi-level principle.

As a result, if you and your phone move from the coverage area of \u200b\u200bone BS sector to the coverage area of \u200b\u200banother, then this movement is carried out by the control unit of this base station, without touching more "high-end" devices - LAC and MSC. If handover occurs between different BSs, then LAC is taken over, etc.

The switch is nothing more than the main "brain" of GSM networks, so its operation should be considered in more detail. A cellular network switch undertakes approximately the same tasks as a PBX in the networks of wire operators. It is he who understands where you are making a call or who is calling you, regulates the work of additional services and, in fact, decides whether you can currently make your call or not.

Now let's see what happens when you turn on your phone or smartphone?

So, you pressed the "magic button" and your phone turned on. There is a special number on the SIM card of your mobile operator, which is called IMSI - International Subscriber Identification Number (International Subscriber Identification Number)... It is a unique number for each SIM card not only for your operator MTS, Beeline, MegaFon, etc., but a unique number for all mobile networks in the world! It is on him that operators distinguish subscribers from each other.

At the moment of turning on the phone, your device sends this IMSI code to the base station, which transmits it further to the LAC, which, in turn, sends it to the switch. In this case, two additional devices come into play, connected directly to the switch - HLR (Home Location Register) and VLR (Visitor Location Register)... Translated into Russian, this, respectively, Home subscribers register and Guest subscriber register... HLR stores the IMSI of all subscribers on its network. The VLR contains information about those subscribers who are currently using the network of this operator.

The IMSI number is transmitted to the HLR using an encryption system (another device is responsible for this process AuC - Authentication Center)... At the same time, HLR checks whether a subscriber with a given number exists in its database, and if the fact of its presence is confirmed, the system looks whether it can currently use communication services or, say, has a financial block. If everything is normal, then this subscriber goes to VLR and after that he gets the opportunity to call and use other communication services.

For clarity, we will display this procedure using the diagram:

Thus, we have briefly described how GSM cellular networks work. In fact, this description is rather superficial, since if we delve into the technical details in more detail, then the material would have turned out many times more voluminous and much less understandable for most readers.

In the second part, we will continue our acquaintance with the operation of GSM networks and consider how and for what the operator debits funds from our account.

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 in any way.

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 field of operation of the base station, the device establishes communication with others - the connection established by the subscriber is imperceptibly transmitted to other "cells", which ensures continuous communication when moving.

In Russia, three bands are certified for broadcasting - 800 MHz, 1800 MHz and 2600 MHz. The 1800 MHz band is considered the most popular in the world as it combines high capacitance, long range and high 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 communications, which was based 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 dates back 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 repeatedly increased.

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

In 2020, the official launch of a new generation of 5G 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 on 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 be launched 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.

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 life, 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, then in Russia it only began to appear, and became available to everyone a little over 10 years ago.

Bulky brick-like mobile phones that worked in the formats of the first and second generations went 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: the base station subsystem and the 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 may have equipment of several generations of communication (2G and 3G) at once.

But on the BS Tele2 towers there is only equipment of the third and fourth generation - 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 own 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, however, usually fewer transmitters and sectors are installed at the stations. 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, the 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 coverage with a radio signal at ground level, base stations are designed in a special way, therefore, despite a 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 (congestion, 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 operation of the entire network in Moscow.

Few views from the Tele2 office.

At a meeting of the company's employees, plans to capture the capital are discussed) 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 at 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 jam 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!

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