The communication of mobile, or, as they are also called, cell phones, is carried out not with the help of wires, as in a conventional telephone system, but through radio waves. To make a call on a mobile phone, you need to dial the number as usual. Thus, the radio message arrives at the base station operated by the cellular telephone company.

At the station that handles all calls within a given radius or zone, the controller device determines the call to a free radio channel. In addition, it sends a signal to the automatic telephone exchange of cellular communication. By reading the special codes transmitted by the phone,

ATS monitors the movement of the car in the zone of the first station. If during a call the machine bypasses the zone and enters the next one, the call is automatically transferred to the base station operating in that zone. When calling from a mobile phone, the caller is connected to an automatic telephone exchange for cellular communication, which determines the location mobile phone, requests a free radio channel from the circuit controller and communicates - through the base station - with the desired number. Then the mobile phone rings. When the driver picks up the phone, the circuit is completed.

Base station operation

Each base station receives signals emitted within a radius of three to six miles. To avoid noise, base stations with matching boundaries should operate on different frequency channels. But even within the same city is enough remote friend stations can easily operate on the same channel from each other.

The local telephone system, which serves both homes and offices, is based on wires that run above and below the ground and are connected to an automatic exchange.

Location and channel

The PBX determines the location of the moving vehicle while the circuit controller routes the call to the communication channel.

Call area

When the car leaves the area of ​​the most remote base station, the driver can no longer use cellular communication. If a call is made on the way to the edge of the zone, the signal gets weaker and weaker and eventually disappears altogether.

On the way from station to station

All over mobile call An automatic telephone exchange for cellular communications fixes the location of a moving car by the strength of the radio signals emanating from it. When the signal becomes too weak, the automatic telephone exchange alerts the base station, which in turn transfers the call to serve the neighboring exchange.

In the theoretical part, I will not delve into the history of the creation of cellular communications, about its founders, the chronology of standards, etc. To whom it is interesting - there is plenty of material both in print publications and on the Internet.

Consider what a mobile (cellular) phone is.

The figure shows the principle of operation in a very simplified way:

Fig.1 The principle of operation of a cell phone

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

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

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 Authentication Center (AuC) database upon receipt of the manufactured SIM cards by the telecom operator. When registering a phone in the network, the identifiers are transmitted by the BS, namely AuC. Then AuC (Identification Center) sends a random number to the phone, which is the key to perform calculations using a special algorithm. This calculation takes place simultaneously in the mobile phone and AuC, after which both results are compared. If they match, then the SIM card is recognized as genuine and the phone is registered on the network.

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

This number is stored in the phone's non-volatile memory. In older models, this number can be changed using special software (software) and the corresponding 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 the duplicate is stored in the OTP (One Time Programming) memory area, which is programmed by the manufacturer once and cannot be reprogrammed.

So, even if you change the number in the first memory area, then the phone, when turned on, compares the data of both memory areas, and if different IMEI numbers are found, the phone is blocked. Why change all this, you ask? In fact, the laws of most countries prohibit this. Phone by IMEI number tracked on the web. Accordingly, if the phone is stolen, it can be tracked and seized. And if you have time to change this number to any other (working) number, then the chances of finding a phone are reduced to zero. These issues are dealt with by 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 moment 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 incorrect update, and then the phone is absolutely unusable. This is where all the means come to the rescue to restore the IMEI and the device's performance. This point will be discussed in more detail in the software repair section of the phone.

Now briefly about voice transmission 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. Digital DECT radiotelephones are somewhat similar, but the implementation is still different.

The fact is that the subscriber's voice, before it is broadcast, undergoes many transformations. analog signal is divided into segments with a duration of 20ms, after which it is converted to digital, after which it is encoded by 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) - discontinuous speech transmission. Its usefulness lies in the fact that it controls the phone's transmitter, turning it on only at the moment when speech begins and turning it off in the pauses between conversations. All this is achieved with the help of the VAD (Voice Activated Detector) included in the codec - a speech activity detector.

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

Mobile phone device and its main functional nodes(modules).

Any mobile phone is complex technical device, consisting of many functionally complete modules that are interconnected and generally ensure the normal operation of the device. The failure of at least one module entails a minimum - a partial malfunction of the device, a maximum - the phone is completely inoperative.

Schematically, a mobile phone looks like this:

Fig.2 Cell phone device

Purpose and operation of individual nodes.

1. Rechargeable battery (battery)- the main (primary) power source of the phone. During operation, it has one unpleasant property - aging, i.e. loss of capacitance, increase in internal resistance. This is an irreversible process and the rate of battery aging depends on many factors, the key of which is proper operation and storage.

Previously, the bulk of batteries for phones were produced using NiCd (nickel and cadmium-based), NiMH (nickel metal hydride) technologies. These batteries are currently discontinued. With the spread of batteries based on Li-Ion (lithium-ion) technology, the latter showed the best price-quality ratio, and also had a number of advantages, in particular, the absence of the so-called. "memory effect". The service life is approximately 3-4 years. Not so long ago, Li-Pol (lithium polymer) batteries appeared on the market. They are cheaper than lithium-ion ones, but they also have a shorter service life - about 2 years.

Modern batteries are recognized as efficient if they have retained at least 80% of the nominal capacity. In practice, there are batteries with 50% or less. That is, many users try to “squeeze” the last milliamps out of the battery, which is why they themselves then suffer, since a worn-out battery often begins to swell, which can lead to breakdowns of the phone case, and sometimes even to failure of the network charger, circuits phone charging, power controller. So, it's not worth saving money on the battery. The phone needs good power too

Batteries do not require special care. The main thing is to prevent hypothermia in winter (up to -10 ° C), because. accelerated discharge and aging. As well as heating up to 50-60 ° C and above. This is dangerous - the battery can simply swell and even explode (this is critical for lithium batteries) !!!

The battery of a mobile phone consists of 2 parts: the battery itself and a small electronics-automatic board.

Fig.3 Device battery

In the figure, for clarity, I showed an already damaged swollen battery. Most often this happens as a result of using cheap chargers, with malfunctions of the phone charging circuit, as well as with high charging currents selected by the manufacturer (to reduce battery charging time). And, of course, cheap non-original batteries “get fat” very quickly.

As for the electronics board, it performs a protective function, preventing both the battery itself and the phone from emergency situations, such as:

Short circuit (short circuit) of the battery supply terminals;

Battery overheating during charging and operation;

Battery discharge below the established minimum allowable rate;

Battery recharge;

When one of them occurs, the so-called. the electronic relay and the battery output terminals are de-energized.

As a rule, a modern battery has at least 3 contact terminals for connecting to a mobile phone's battery connector. These are respectively “+”, “-”, and “TEMP” (temperature sensor, with which the battery controller, together with the phone’s power controller, control the battery charging process, reducing or increasing the charging current, and in case of overheating or short circuit, disconnect the battery from the board terminals altogether electronics).

Fig.4 Location of battery contacts

It should be noted that the location of the contacts may differ for different manufacturers !!!

The main characteristics of the battery are:

Rated voltage - usually 3.6 - 3.7 Volts. For a fully charged battery 4.2 - 4.3 volts.

- capacity - for modern phones from about 700mA to 2000mA and more.

Internal resistance - the lower the better (up to about 200 milliohms)

2. Power controller- serves to convert the battery voltage into several types of voltage to power individual components and devices of the phone, such as the CPU (central processing unit), RAM and ROM (memory chips), all kinds of amplifiers, sometimes keyboard and display backlights, etc., and also controls the battery charging process. Together with the processor, it activates the built-in or external sound amplifiers of the conversational speaker, microphone, buzzer (polyphonic loudspeaker). Plus, it provides data exchange with a SIM card.

Structurally made in the form of a separate chip. Sometimes it can be combined with the processor ( Chinese fakes well-known brands such as Nokia N95, etc.)

During normal use of the phone, the power controller rarely fails. Most often this happens during overheating charging or when using a non-original or faulty charger (charger). Less often - if the phone was exposed to moisture, it was hit hard.

The appearance is shown in Fig. 2 and may differ (depending on specific model phone and its manufacturer).

3. SIM-holder (sim - connector) - SIM card holder. Based on the name, it is used to connect the SIM card to the phone. The design is almost the same for all phones, since modern SIM cards are brought to the same standard. It has 6 (rarely 8) spring-loaded contacts, through which the electrical connection of the SIM card and the power controller or processor is carried out. They differ only in the design of fastening (holding) the SIM card. Breakdowns include breaking contacts when frequently changing SIM cards or inept (incorrect) removal of them, when the user begins to use improvised means to pick a SIM card for further capture with fingers and removal from the holder. Often our beautiful ladies resort to this, using their long, expensively manicured nails. As a result, both the phone and manicure suffer.

The connector does not require special care. But there are cases (again, it depends on the user) when the contacts are oxidized, clogged, lose their springy properties. In this case, be VERY CAREFUL!!! wipe them with an eraser (eraser) and VERY CAREFULLY !!!, slightly bend the contacts up with a needle or a wooden toothpick.

With the SIM-holder (holder) malfunctions described above, the phone will not “see” your SIM-card and will constantly display a message like: “Insert SIM-card”. Broken holders cannot be repaired and must be replaced with new ones.

4. Microphone- serves to convert the user's voice into weak electrical signals in order to further amplify, convert and send them on the air. There are two types of cell phones: analog and digital. The latter have a more complex design and require more labor during dismantling and replacement.

Microphones lose their performance or break down mainly when they get dirty, get water, or get hit by the phone (this is especially true for digital microphones, because they themselves are very fragile).

If the microphone malfunctions in the phone, there may be such defects:

The second subscriber does not hear the user at all;

The second subscriber hears the user very weakly;

In the auditory (conversational) speaker, a crackling is heard (the so-called pickup of the GSM signal). The same noise can be heard by bringing cellular telephone in talk mode or sending sms to a working radio, amplifier, computer speakers, etc. As a rule, microphones are not repairable and must be replaced (except in cases of clogging of holes, sound ducts of a mobile phone case. They should simply be cleaned of dust, dirt, etc.)

5. Speaker ( speaker) - serves to convert electrical signals into sound vibrations. That is, it works in the reverse order of the microphone. One caller speaks into a microphone that converts the voice to email. signals, then these signals are converted (see the description above), radiated into the air. The other party receives these signals on the phone and hears them on the phone's speaker.

Most phones have several speakers - separately conversational and separately polyphonic. The polyphonic speaker plays a melody when incoming call, sms, etc. But there are phones (mostly by Samsung), where the role of conversational and polyphonic is played by the same speaker. Only when playing a melody or other signals, the auxiliary audio power amplifier is activated. Speaker failures include partial failure and complete failure. Partial is the reproduction of speech or music very quietly, with wheezing and an unpleasant ringing. This can be eliminated, but only in those cases when, after an external examination, it will be seen that the speaker is clogged with foreign objects. For example, such as very small metal shavings that like to penetrate through specially designated holes for the sound of the speaker to exit. This is due to the fact that the speaker in its design contains a permanent magnet. So he magnetizes small metal objects to himself. Personally, I am a supporter of replacing such speakers with new ones. Firstly, it will save you time that you will spend on cleaning, and you will need a lot of it. Secondly, it rarely happens that after cleaning the speaker works just as cleanly, without distortion and just as loud. So, do not think - immediately change to a new one. Especially if this phone is not yours, but came in for repair.

Complete - no sound at all. The reason is a break in the wire of the voice coil of the speaker. The only solution is to replace the speaker. I will write about how to check the speaker for serviceability (integrity) below.

6. Speaker (buzzer, bell, polyphonic speaker - it's all the same)- the same speaker, only in most cases it is designed to play ringtones, sms, MP3, etc. But, as mentioned above, it can also be used for conversation. Faults and troubleshooting are the same as for the conversational speaker.

7. Central processing unit (CPU)- is the main device of the mobile phone. This is the same processor that is present in any personal computer, laptop, etc., only a little smaller and more primitive. Designed to execute machine commands, instructions and operations provided by the software (firmware-decomp.) of the phone, as well as clear interaction with other modules and devices and their subsequent control. In a word, the processor is the “brain” that completely controls the operation of the mobile phone. Structurally made in the form of a separate chip. Responsible for many processes that occur during the normal operation of the phone. The main ones are: displaying an image on the display, receiving and processing cellular network signals, receiving and processing keyboard module signals, controlling the operation of the camera, devices for receiving / transmitting information, the process of charging the battery (together with the power controller) and much more.

Under the condition of normal operation of the phone, the processor almost never fails and does not require any maintenance.

In modern phones, and especially smartphones (translated from English, a smartphone is a smart phone. The same phone, only has similarities with a computer due to the presence operating system and many installed programs to perform certain tasks) often 2 processors are installed. One of them performs the same functions as in a regular phone, and the second is designed for the operation of the operating system and the execution of its programs.

If the central processor fails, the phone is completely inoperative.

8. Flash - memory. A separate chip (microcircuit), which is designed to store the phone software (firmware, firmware), as well as user data (contacts, melodies, photos, etc.). Software (firmware, firmware) is a program developed by the phone manufacturer, which is processed and executed by the processor. For the user, this is what he sees on the screen of a mobile phone and the functions that are available to him in a particular phone model.

Flash memory also rarely fails under normal use. But it should be remembered that these chips have a large, but still limited number of read / write information cycles.

Flash memory is non-volatile and retains all data written to it even after disconnecting the power source (eg battery).

9. RAM - memory (RAM). Serves for temporary storage of data. It performs all processor calculations of the program code, and also stores the results of calculations and information processing at a specific current moment (for example, listening to music, playing videos, running applications, games, etc.) As unnecessary, the memory is cleared of some data and loads new ones and so constantly.

It should be remembered that RAM memory (random access memory) is volatile and in the event of a power outage, all data stored in RAM will be lost !!!

10. Keyboard module- a standard numeric keypad for dialing a subscriber's number, texting SMS messages + a set of additional buttons that perform functions defined by the phone software, such as adjusting the volume level, launching programs, a camera, a voice recorder, etc. For the normal operation of the keyboard module, the main task of the user is to keep the keyboard clean and prevent moisture, dirt and other objects from entering. Otherwise, the buttons have to be pressed with great effort, or the phone does not respond to pressing at all. You can restore the operation of the keyboard module by cleaning it from dirt. If the contact pads and the conductors connecting them were exposed to moisture or other liquids and were damaged, then such a keyboard module must be replaced with a new one.

11. LCD display- the actual display (screen) of the phone. The purpose is clear to everyone, so I will not delve into this. The main characteristics are parameters such as:

Resolution, that is, the number of reproduced pixels (dots). The higher this parameter, the clearer and better the picture will be. More or less modern phones are characterized by such screen resolutions: 220X176 pixels, 320X240. For phones with large touch screens: 400X240, 640X360, 800X400.

The number of reproduced (displayed) colors. Same thing, the more the better. In older phones with color displays, this value is mostly 4096 colors. With the improvement, this parameter increased to 65 thousand, then reached 262 thousand. Now all modern expensive phones are equipped with displays with a color depth of 16 million.

When used properly, the display does not require any maintenance. In some cases, when the phone is used in a dusty environment, or just over time, a lot of dust and debris have accumulated in the case, the display must be CAREFULLY wiped with microfiber (a special cleaning cloth that cleans well and leaves no marks and streaks. It can be purchased at sales outlets Some types of glasses are equipped with such cleaning microfiber.) When using the phone, do not allow physical impact on the display (impact, squeezing, strong bends), as well as expose it to direct sunlight and high temperatures. This will cause it to fail.

12. Transceiver- serves to receive and transmit a cellular GSM signal. It contains many functional elements (generators controlled by the voltage of the receiver and transmitter, bandpass filters, decoupling capacitors, inductances, etc.). It is controlled by a processor and a 26 MHz quartz resonator.

If the transceiver malfunctions, the phone will not be able to register in the cellular network and there will be no indicator of the GSM signal strength on the display.

13. Power amplifier– designed to amplify the signal generated by the transceiver to the power level required for the antenna to radiate on the air.

If the power amplifier malfunctions, the phone will receive a cellular network signal, but will not be able to register in it, since it will not be able to transmit a GSM signal.

14. Antenna switch (switch)– designed to interface (connect) the receiving and transmitting paths of the GSM module to the telephone antenna. This ensures that the phone has one common antenna for receiving and transmitting, and also excludes the influence of the power amplifier on the receiving path.

Structurally, the antenna switches are made on a fragile ceramic substrate and, when the phone falls, very often fail, because. the substrate is cracking. In such cases, the phone "does not see" the cellular network signal.

15. Antenna– designed to accumulate energy emitted by the base station and then transfer it to the receiving path circuit. When transmitting a signal, the opposite is true: from the transmitter, the signal is amplified by a power amplifier and fed into the antenna, which emits the signal on the air.

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

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

In order to learn about the operation of modern cellular communication 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, let me tell you a little about the history of the emergence 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 mobile radiotelephone was created in 1957, then scientists from other countries created similar devices from different characteristics, and only in the 70s of the last century in America were determined the modern principles of cellular communication, after which its development began.

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

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

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

Why is it called cellular? Because the territory on which communication is provided is divided into separate cells or cells, in the center of which there are base stations (BS). In each "cell" the subscriber receives the same set of services within certain territorial boundaries. This means that when 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 by the so-called handover, in which the connection established by the subscriber is as if picked up by neighboring cells in a relay race, 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 usually 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 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 only the third and fourth generation equipment - 3G / 4G, is installed on Tele2 BS towers, since the company decided to abandon the old formats in favor of new ones, which help to avoid breaks voice communication and provide more stable internet. Regulars of social networks will support me that in our time the speed of the Internet 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 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, which 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 placed 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 phones, then the round one connects the BS to the controller.

Depending on the characteristics, each sector can serve up to 72 calls at the same time. 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 modern equipment: Ericsson base stations, transport network - Alcatel Lucent.

From the subsystem of base stations, 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. To put it simply, the switch is It has the same functions as the female operators, who used to connect you with the subscriber by hand, only now it all happens automatically.

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

In addition to conventional towers, there are also mobile variants 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, due to problems in the legislation, they have not yet found wide application.

In order to provide 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 the flight altitude of aircraft. 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 the terrestrial cellular network using satellite channel. The system is complemented by a control panel that allows the crew to turn the system on and off, as well as certain types of services, such as turning off the voice on night flights.

I also looked into the Tele2 office to see how specialists control 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 (congestion, network failures, etc.), then over time, the need for such a number of monitors has disappeared.

Technology has evolved over time, and such a small room with a few specialists is enough to monitor the operation of the entire network in Moscow.

A few views from the Tele2 office.

At a meeting of company employees, plans are being discussed to capture the capital) From the beginning of construction to the present day, 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 area, it is very important to me. so that this network comes to my town as soon as possible.

The company plans for 2016 to provide 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, Delovoy Tsentr, Kotelniki, Lermontovsky Prospekt metro stations , Troparevo, Shipilovskaya, Zyablikovo, 3G: Belorusskaya (Koltsevaya), Spartak, Pyatnitskoye Highway, 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, BS stand at a distance of about 500 meters from each other) in order to provide more stable communication 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 the equipment for communication is installed. If you look closely, you will notice a little further to the left one more such mast, with the equipment of other cellular operators.

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

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

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

The company's specialists have a lot of work, given that in Moscow and the region the company has more than 7 thousand employees. base stations: about 5 thousand of them. 3G and about 2 thousand. LTE base stations, 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. 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, 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 r (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 without moving 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 station Tretyakovskaya. Signal reception - 5.82 Mbps, transmission - 3.22 Mbps.

And on m. Krasnogvardeiskaya. Reception - 6.22 Mbps, transmission - 3.77 Mbps. Measured at the exit of the subway. If we 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, given 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 quickly come to the region and I will be able to fully use 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, which will be seen not only by the readers of the community, but also by the site http://ikaketosdelano.ru

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Looking at them, I realized that it was time to update the material - the second article was written at a time when Yota was working on Wimax technology, and 4g had just appeared, the first one even earlier.

The new article is not only about modems, but about the mobile Internet in general. It is designed primarily for those who have just begun to understand this topic, that is, “experienced mobile Internet users” are unlikely to find something unknown here.

I want to chew on some of the fundamental subtleties associated with the mobile Internet, "put everything on the shelves", so to speak. Let's start.

What do you need to use mobile internet?

1. contract (and SIM card) with some mobile operator and a connected tariff (tariff option, package), which implies the presence of a certain amount of traffic or access to the network without restrictions;
2. a device that will work with this operator and allow you to directly “surf the Internet”, and (or) make it possible to connect other devices to the network;
3. everything should happen in the coverage area of ​​the network of the selected operator.

It seems simple, but in reality - there are enough subtleties, let's sort it out in order.

Where will mobile internet work?

It will work within the coverage area of ​​the network of your chosen operator. At the same time, the better the signal level, the better it will work. The signal level is not the only thing that determines the possible speed.

How will mobile internet work?

There are a number of technologies for transferring data over mobile networks - the speed depends on which technology is used at the moment. Each defined technology must be supported by both the device and the operator base station with which it operates. We also do not forget about the signal level.

The speed will depend on:

• what type of network the operator has in the place where you are;
• what data transfer technologies your device supports;
• what is the signal level in the place where you are (I wrote about it separately).

The speed depends on the current load on the network (primarily for cities) and on the weather (on the contrary, this is especially noticeable outside the city, when the distance to the base station is large).

What types of networks and data transmission technologies exist at the moment?

Second generation networks - 2g (GSM). Includes two data transfer technologies:

GPRS- the slowest option. If we are talking about a smartphone or tablet, then when working with GPRS, the “G” symbol lights up next to the signal strength indicator. The "ceiling" of this technology in ideal conditions is only 171.2 kbps. And conditions are rarely ideal. You can't do much with GPRS - e-mail, surfing (it's better with disabled image loading - otherwise you will wait for loading each page for a very long time), instant messengers. About YouTube, listening to music online and other delights modern internet feel free to forget.

EDGE- already better. When working with this technology, the smartphone or tablet will show the letter "E" next to the signal strength indicator. The theoretical "ceiling" for EDGE is 474 kbps. In real conditions, the speed will, of course, be lower, but still - you can count on 150 - 200 kilobits, and this will already allow you to surf (having angelic patience), play some games (many MMOs do not need a wide channel), and etc., but with multimedia content, as before, it will be hard.

Third generation networks - 3g (WCDMA):

This includes actually 3g (UMTS), and when working in such networks, the smartphone or tablet will show the symbols "3g" near the signal strength indicator. The theoretical maximum data transfer rate is 2048 kbps. This can already be called quite adequate network access speed. You can also talk on Skype and watch videos on YouTube.

HSDPA- a more advanced version. Theoretically possible speed is as much as 84.4 Mbps. In the "field" conditions, I was able to see numbers in the region of 5 - 15 megabits. The smartphone, when working with HSDPA, will show you the symbol "H" or "H +".

Fourth generation networks - 4g (LTE)

And so far, the only technology in this category is actually 4g, or, if you use the “official” and not the marketing name, LTE (although not only LTE. If you are interested, see Wikipedia). In theory, 4g supports speeds up to 173 megabits per second for receiving and 58 for uploading. In practice, I was able to “target” 40 megabit reception (although I often see talk about higher speeds on the net).

About devices

To access the network, you can use various devices. It could be:

Modem. Connects to a computer via USB, some tablets also support modem connection - also via USB using an OTG cable (if there is a full-fledged USB port, then without any OTG). Allows you to access the network on the device to which it is connected. If the Internet needs to be distributed, then there are several options. Connect the modem to the router (see the next paragraph). You can distribute from the computer to which the modem is connected, but this requires quite specific settings, especially if you plan to distribute via Wi-Fi. You can, if necessary, distribute via Bluetooth. Theoretically, the tablet to which the modem is connected can also distribute the Internet (additional programs may be required if there is no “portable hotspot” option in the settings).

If the modem was purchased in the salon of one or another operator and carries its identification marks on board, then, with a probability of 99.9%, the modem is "locked", that is, a software restriction is set, due to which the modem only works in the network of its operator. You can overcome this misfortune - the modem can be "unlocked". There is no universal recipe here, so we enter the modem model into Google, add the word “unlock”, and read what we found (most likely it will be all sorts of forums).

Turning not to a communication salon, but to a regular computer store, you can buy a modem that will work with the network of any operator. Keep in mind that it will cost more (maybe even much more) - operators, not infrequently, sell modems, which is called “at a loss” and earn money by selling traffic.

Router + modem. We connect the modem to the router, set up the router - it distributes the Internet - via Wi-Fi, by wire, etc. From the subtle points - the router must have a USB port, in addition, you must first clarify whether a particular router works with a particular modem. You need to look for a list of supported modems on the website of the router manufacturer, where you can also download the latest firmware, which can support new modem models.

Special mobile router. These are sold in communication stores, and are a device that already combines both a modem and a router. Still, not infrequently, there is a battery - so that it can be used in "field" conditions. Like modems, they can be "locked" to one operator. As is the case with modems, in computer stores you can find devices that are not tied to any particular operator.

Cellular telephone. Often, it can also provide Internet access by connecting to a computer or tablet with a wire, or via Bluetooth.

Smartphone or tablet. Most smartphones and tablets (of course, those that support 3g or 4g and have a slot for a SIM card) can act both as a modem, when connected to a computer via wire or Bluetooth, and as a router, distributing the Internet via Wi-Fi. Since we touched on this topic above, I will mention cheap smartphones, sold in communication stores under the brands of certain operators, are also often “locked”, in two-SIM cards only one SIM card is often “locked”.

Will a 3g modem work in a 4g network and vice versa?

The question is valid not only for modems, but also for any other devices.

Operator networks rarely support just one technology. Often they are supported by everything from 2g to 4g. In the outback there are base stations without 4g, and sometimes without 3g. That is, with rare exceptions (we will consider below), if you see some cell tower, then it is most likely "2g or higher".

Various devices, most often, also support everything, although it is still quite possible to buy a smartphone or modem in the store that “can” only 2g and 3g.

Other things being equal, there shouldn't be any problems. If you get to a place with a 4g modem (smartphone, tablet) where the operator has 3g coverage, it will simply work in 3g. And even in 2g it will work if you get to a place where there is only such coverage.

If you with a 3g modem (smartphone, tablet) get to a place where the operator has 4g coverage, the device will still work, but again only in 3g. Finally, if you take some old phone that does not even know how to 3g, then it will still work - just in 2g.

There are exceptions to what is described above. For example, the Tele2 network in Moscow and the region is implemented only in 3g and 4g. Or Yota modems - they work only in 4g. And even if you insert a Yota modem SIM-card into a “non-Yota” modem that “can” 3g, nothing will work - that's how everything is arranged with them.

Let's take a closer look at the situation with Tele2 in Moscow: if you insert a Tele2 SIM card into some device that can only work in 2g networks, then nothing will work for you.

More complex example- almost all dual SIM devices currently on the market have only one SIM card that can work in 3g \ 4g, while the second one will work only in 2g. This means that when using Tele2 in the Moscow region, you must give the privilege of using 3g \ 4g to this particular SIM card. Under these conditions, you can adequately use the Internet only through Tele2. If you want Internet through a SIM card of another operator, you will have to switch it to 3g \ 4g mode, while the Tele2 SIM will go into the “2g only” mode and simply stop working - I remind you, because Tele2 does not have a 2g network in Moscow.

Smartphones in which both SIM cards can simultaneously work in 3g \ 4g are still few (google and find out if you need one).

About SIM cards and different devices (will a SIM card from a modem work in a smartphone and vice versa)

Looking through the search queries through which visitors come to my site, I often see something like “is it possible to insert a SIM card from a smartphone into a modem” or vice versa “from a modem to a smartphone”. At the time of writing the previous articles, both questions could be answered in the affirmative, but now the situation has changed.

Technically, you can insert a SIM card from a smartphone into a modem without any problems - exactly the same SIM cards are used there and there. Even if you have a micro-SIM in your smartphone, and a full-size SIM in the modem, you can still insert it by simply pressing it against the contacts in the desired position, since the contact pad is the same size there and there. You probably noticed that SIM-cards are now sold universal - initially it is full-sized, and using pre-saddle cuts, it can easily be turned into micro- and nano-SIM. The piece of plastic remaining after this can be used as an adapter. Decided, from a technical point of view, there are no problems.

There are restrictions of a different nature - along with the advent of tariffs offering unlimited Internet for a smartphone / tablet, there was also a restriction on the part of operators who are not interested in using SIM cards with such tariffs in modems and routers. As a rule, this is stated in the tariff itself - something like "The SIM card is intended for use in a smartphone / tablet, when used in a modem, Internet access will be limited."

There are also modem tariffs, the use of which in smartphones is limited by the operator. And if not limited, then on some of them voice calls are generally impossible, on others high prices are set for “voice”. Be careful!

The final answer to the questions “is it possible to insert a SIM card from a smartphone into a modem” or “A SIM card from a modem into a smartphone” is as follows: depends on your carrier and tariff plan. If in doubt, call the operator and ask.

About distributing the Internet from a smartphone or tablet

If you have Internet access on your smartphone or tablet, using wire, Wi-Fi or Bluetooth, you can provide network access to other devices - say, a laptop. It is very convenient on the road. This is how I use the Internet at the dacha on weekends, and at home I use the Internet from my smartphone as a “backup channel” - if wired Internet disconnected, a couple of taps to start the access point on the smartphone - and I'm back online.

That's like all. I hope the article was useful to you 😉

If you sit on the Internet all the time, then you get the false impression that everyone around everyone owes everyone. Even if you don’t delve into politics, where in general everyone is like one expert and knows what needs to be done, but, as the hero of one joke said, there is no time to do something yourself, because you need to “taxi”, then we are surrounded by crowds of dissatisfied people. In general, everyone is dissatisfied with mobile communications as one. I don’t have a ready recipe for how to fix this dissatisfaction, but there is good news: if you understand how this damn mobile connection works, then you are much less nervous. For example, have you ever talked about the quality of communication with those who deal with it? I've said that quite a few times. And I have never met a dissatisfied specialist (although, of course, they also have problems with communication). They do not fuss, they are not nervous, because they almost always have a clear idea of ​​\u200b\u200bwhat (and why) is happening. And under what conditions the situation can change. Mastering this "kung fu" is actually not difficult, and you need to start by understanding how mobile communications work and what processes take place in it when we pick up the phone, make a call or use the phone for the Internet.

radio signal

And you need to start with the banal: mobile communications actually (that's news, right?) Uses a radio signal, which, by definition, cannot be as reliable a connection as a thick copper cable that is securely hidden from any influences (well, except for an excavator bucket, of course) from the outside. The radio signal is subject to a bunch of other things in this unfair world. If only because we are constantly surrounded by many transmissions invisible to the eye, passing at a variety of frequencies. Of course, we all know from a school physics course that a radio wave signal can be at different frequencies (and different powers, I’ll add, but for our understanding of the situation this is already too complicated, we won’t go so deep). And when we say that our phones operate at 900, 1800 and 1900 MHz, these are actually frequency bands. And a specific base station and your phone can work on others that are close to them: 1799 or 1801 GHz. It is this division of frequencies that allows thousands of people to use mobile communications at the same time in a modern city, and not wait until a free frequency is free. Which complicates the situation even more if you think about the fact that we have more mobile operators than one. And they all work at the same time.

We also remember from the physics course (after all, we remember, right?) that when passing through an obstacle, the signal weakens. Remember how things are with the Bluetooth signal if you go into the next room. But the distance is less than the declared standard of 10 meters. So, are you being lied to? No, there is an obstacle in the way, and if the wall is also load-bearing, then inside it is not drywall, but iron fittings, which definitely only worsens the signal and certainly does not improve it. The situation is similar with Wi-Fi and mobile communications. Because in both cases, a radio signal is used. Therefore, every time you enter the elevator or go down to the basement (for example, in a cafe), the connection may suddenly deteriorate. And this is normal, because it fully complies with the laws of physics, even if you do not know anything about them.

base stations

Somehow they set up a base station in one village.
After some time, the operator who installed the base station,
began to receive complaints from local residents
for worsening health.
"What's that," the representatives of the operator replied, -
"Look what happens when we turn it on"
A popular anecdote among operators

Some (not all, of course) realize that mobile communications also require base stations. These are quite complex (and expensive) complex structures, including a different set of communication (and not only) equipment. In the minimum configuration of the base station, you need power, connection to other similar base stations and / or network routers that can correctly route data and instantly connect two subscribers. This connection can be via an optical fiber cable (and then you won't even see it) or via a radio channel. And then you will see such large round radio relay antennas operating along a directional beam and connecting the base station with another (specific) same station. In the city, such base stations can be placed on the roofs of administrative (mainly, it is easier to get permission to install them) buildings. Why on rooftops? Because the higher - the more open space and fewer obstacles to the radio signal. Outside the city (or where there are no tall buildings), a separate mast is installed for the base station, which looks like power transmission masts. The base station itself is also a box with smart electronics serving all this economy, as well as an air conditioner that cools its operation (it is especially needed, as we all understand, in summer). In theory, each base station should also have a self-powered diesel generator that turns on automatically when there is a power outage. Otherwise, in case of any power grid failures, mobile communications will be immediately disabled, otherwise it will still be able to work for some time (ideally, until the repair team arrives or the power grid failure is eliminated). Checked out? And we have not yet moved on to transmitters that directly connect the base station with mobile phones. You see them most often - these are vertically installed panels, usually there are three of them - in a sector of 120 degrees each.

In order for all this to work like clockwork and different market players do not interfere with each other, there is state regulation. It concerns the power of the equipment used, the safety of mobile phones (which is why all legally sold phones undergo mandatory certification, which, albeit slightly, increases their cost). By the way, this is why phones bought abroad may not work as well as we would like - they are designed for other conditions and meet other requirements. This is especially true for cheap models (as a rule, such surprises do not occur with branded phones, because they are released by companies that carefully monitor the compliance of their devices with the standards of the countries where they are officially sold). About why the state does this, how and what benefits it brings to society, you can read in a separate article on this topic.

But we remember that radio communication and its quality still depends on many factors that are not constant. The data transfer rate at a specific location in a specific time period can change significantly if the source data changes. Therefore, consumer tests are subjective, but they can give information to the consumer in a certain geographical point about the quality of the service provided. The quality of the network can really be assessed only with the help of special equipment and a whole team of specialists (and in each city - a separate one).

In addition to natural causes (network load, for example), there is another problem: in the cities where we live, new facilities are constantly being built that can radically change the picture of network coverage and signal availability in a particular area. Therefore, the process of network radio planning is a continuous process. It never stops, and the introduction of 3G that we are seeing now is just one episode in a long chain of ongoing work that has been going on, is going on and will go on in the future. Is always.

In addition to rather slow changes (construction of a high-rise, you see, takes months or even years), there are also spontaneous bursts of mobile communication consumption that can create peak loads that many times exceed the network capacity in the current location. The simplest example is exhibitions, when thousands of people gather in one building or pavilion, each of whom has a mobile phone in his pocket. You have probably come across a situation where mobile communications did not work well at an exhibition (or stadium). Similar surges, for example, occur on the eve of the New Year, for which all operators are carefully preparing. Because for them this is not only a certain challenge and customer satisfaction, but also (why hide) additional income.

If the event is known in advance, so-called mobile base stations are used to increase the network capacity. They are a car, inside of which there is a bunch of expensive electronics that connects to the operator's network and increases the network capacity in a particular place. To deploy such a mobile base station, it takes from 3-4 hours to a day (depending on the complexity of the conditions - let me remind you that each operator has its own, and is determined by the presence of the nearest base stations, distance to them, line of sight, and so on). For example, according to Yuriy Grigoriev, head of lifecell's Central Region Mobile Network Operations Department, during the Euro-2012 football championship on Khreshchatyk, three mobile base stations worked in the fan zone at once in different parts of the street (the whole Khreshchatyk was then a fan- area with huge installed screens for spectators). Similar actions are carried out with seasonal events, such as city days. Vacation periods with resort places - seaside in summer and skiing in winter - also make their own adjustments. All these actions are carried out imperceptibly for the majority of mobile subscribers, who are not even aware of the technical difficulties (yes, between us, they should not be aware). But they are carried out by all operators, regardless of what you think about their work.

A separate discussion is the equipment used to improve communication indoors. In order not to complicate the story by listing different repeaters and femtocells, I’ll just say that indoors (it can be a cafe in the basement or a huge shopping center) equipment is installed that increases the network capacity in one way or another and transmits all traffic (voice and data) further to the network operator. In the subway, a special radio-radiating cable is used for this, so we can (or not have) mobile communications even in subway tunnels, although they are at a depth unattainable for conventional radio waves.

Reference network

At first glance, the question seems strange, but we never think about where the signal from a mobile phone goes next. No, it is clear that he goes online mobile operator but what is a "network"? In fact, a significant part of the mobile operator's network is in ... cable. Base stations connected to each other only by radio are not capable of transmitting the entire amount of voice communication and, moreover, data via radio signal. Moreover, the majority of mobile communication users are concentrated in separate cities that are not interconnected by radio communication. And the signal between them passes through the main fiber optic cables that form the basis of the telecommunications industry. There is the concept of "core network" or back bone, which can also be called a transmission due to its functions - the transfer of a huge data flow between key segments of the operator's network. Each city, in turn, can have its own "ring" that combines data flows from specific base stations or strongholds that accumulate traffic from several base stations. To manage the entire network, huge nodal switches serving entire regions are needed. These are huge data centers that manage all traffic and occupy a separate building. They, like any other data centers, have several independent connection channels, their own power consumption systems. In smaller cities, there are also "remote" switches, smaller in size, designed to serve their region.

Now you understand that the operator's mobile network is a very complex system. And at each stage, in each link of the chain - from the user's mobile phone to the base station, switch and core network, there may be a problem with the quality of communication. We talked about these problems in more detail in a separate article, so I will briefly remind you that the quality of communication depends on three factors: coverage, capacity, and the quality of the network itself. Roughly speaking, coverage is where the base station signal “finishes”, capacity is the ability of the network to receive large quantity calls and / or transfer more data (by the way, this is the main benefit from the introduction of 4G networks, which allows you to increase capacity and use more frequencies - this is its own separate problem, including the redistribution of frequencies and technological neutrality).

Billing

Speaking about mobile communications, how it works and where users may have problems, one cannot but touch upon the issue of billing. Technically this software determining the subscriber's tariff, taking into account all the user's costs included in it, and calculating his account balance. It is integrated into the operator's network and when performing any action on the part of the subscriber (call, SMS, Internet access), it first checks whether the user can perform this action, then either allows the system to provide the requested service to the subscriber, or gives him a message why this action should be performed impossible (for example, there are not enough funds in the account). All these numerous operations take place instantly and imperceptibly for the user, but for a general understanding of how mobile communications work, it is worth knowing about it.

How billing works was explained to us by Konstantin Zhilin, Head of Telecommunication Networks Operation Department of lifecell operator: “In order to make a call, the server defines a trigger: what needs to be done to give the subscriber the opportunity to call. The trigger can be "play some tune", sometimes it's the trigger "go check the billing". In order for the subscriber to make a call, the billing system first needs to ask if the subscriber has enough funds to make a call. The billing system looks at the subscriber's account and answers: "please allow me to make a call for such and such a duration." And only after that there is a connection of traffic, routing and so on. After the subscriber has used this call quota, for example, 150 seconds, the billing again makes a permission request and checks the balance on the account. The quota is issued based on the average time of making a call and the balance of money on the account and is calculated in minutes.

The very withdrawal of money from the account (sacred moment) occurs at the end of the call, when the billing system asks the system about the final duration of the call and charges it according to the actual duration, and not according to the volume of the allocated quota. From the point of view of the billing system, changing the subscriber's tariff plan simply means replacing one item in the operator's product catalog with another. The billing product plan contains a list of services available to the subscriber, some of which are basic (and provided within the tariff plan at no additional charge), and some are additional and, accordingly, paid separately. If one or the other changes, then for billing something free becomes paid, or vice versa. Or the cost of a particular service changes. That's how it works. All the talk about theft by money operators is actually a common misconception. That does not cancel the active marketing activities of most operators. But it is physically impossible to steal something from a subscriber.

As they say, knowledge is power, so in all disputable cases, you need to carefully read the terms of your tariff plan and do not hesitate to clarify all questions with the operator. Call center employees are stress-resistant, undergo special trainings and are always ready to calmly listen to the caller and try to help him. We'll talk more about this sometime next time.

For those who want to know more

Operators use their own slang words, which we found funny and worthy of your attention:

• "saucepan"- a radio relay antenna, which has a round shape and is designed to connect two base stations to each other via a radio channel
• "warm the air"- idle, as they say, when expensive equipment does not fully use its capabilities, has excess network capacity and, accordingly, does not bring the expected income for the operator
• "cabinet"- a cabinet of a mobile base station with equipment: a chassis with a transceiver (accommodates up to 4 shelves, which accommodate up to 12 transceivers) and the "brains" of the base station - electronics that ensure the operation of the network itself