Cellular communications over long distances. How does cellular communication work?

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

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

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

How to find out whether 2G/3G/4G will be available in place X (Russia)?

My life experience suggests that coverage maps on operator websites should not always be trusted. At times they slightly embellish reality. How do you know if your phone will work 100% in the places you are going to?

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

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

How can I find out if 2G/3G/4G will be available in place X (other countries)?

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

Which phone to take on a trip around the world?

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

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

Inmarsat has a slightly smaller coverage area. It will not work at the poles. Equipment for using the network is slightly cheaper than Iridium.

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

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

If none of the people with whom you are going on a trip have yet purchased a single satellite communication device, then you can save a lot by renting it.

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

How to find out if Wi-Fi is available in place X?

I already wrote about the wigle.net service in an article. Its database includes a quarter of a billion access points around the world. Their location can be seen on the map.

It is interesting to look at the statistics by country. One in five hotspots (53 million) are located in the United States. There are 2.5 million of them in Russia, but in Uzbekistan there are only 239 (I’m sure there are more in reality).

How to find out if there is Wi-Fi on an airplane?

You can check on routehappy.com whether there is Wi-Fi on board the flight you're planning to take (as well as whether you can charge your devices there and how far apart the seats are).

How to receive/send SMS online?

You already know how to make free calls via the Internet without me. And send free messages on operator sites too. Do you know how to receive SMS to a Russian number online?

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

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

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

Operating principle of cellular communication

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

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

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

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

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

"PHYSIOLOGY"

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

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

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

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

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

"ANATOMY"

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

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

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

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

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

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

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

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

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

In the article:

Mobile communications are an integral life attribute of every person, providing free communication, correspondence and access to the global network. It is impossible to overestimate the importance of cellular services, as well as to choose a more effective and convenient alternative for them.

At the same time, in the modern mobile communications market there are simultaneously several providers that compete with each other and constantly improve the quality and conditions of customer service. Based on official statistics, the most popular providers in Russia include Megafon, MTS, Beeline, Tele2, Yota. Each of them has its own advantages and disadvantages, which determine their overall and subjective usefulness for subscribers. But in order for you to be able to make the final choice and decide for yourself which cellular operator is better, you need to know these weaknesses and strengths of cellular companies.

Internet assistant Tarif-online.ru will help you understand the difficult issue of choosing the best mobile operator for you, pointing out the pros and cons of each of them.

Let us immediately note your suspicions about the marketing component of our article. We are not going to advertise to anyone, but will operate only with facts and objective opinions of experienced users. Still, making the final decision about whose SIM card will be installed in your device remains entirely yours.

Which cellular company is better: description of operator features

It is logical to assume that the entire complexity of choosing an operator is based precisely on determining complex competitive advantages both in terms of communication quality and coverage area size, as well as the variability of tariff plans and the level of technical support. Therefore, let's take a closer look at the characteristic features of each of the providers.

MTS

The mobile operator MTS has been providing high-quality communication services since 1993 and has established itself as a reliable and affordable provider. The company has the largest subscriber base (over 100 million people), promptly introduces advanced technologies, actively develops high-speed mobile networks, and provides the possibility of a single Internet for all devices.

Advantages:

• High quality communication. Thanks to extensive experience in customer service and the use of modern telecommunications equipment, the operator guarantees stable and high-quality communication among dense buildings, inside and outside buildings.
• Well-thought-out Internet tariff plans. MTS is always ready to offer favorable tariffs with a large volume of traffic for subscribers who need constant and uninterrupted Internet surfing. In addition, there is nightly unlimited or completely unlimited mobile Internet.
• Developed roaming network. Long-term partnerships with national and foreign mobile operators allow MTS to provide its users with comfortable communications anywhere in the country and the world.

Flaws:

• Relatively high tariffs for services. The issue of MTS communication prices is quite complex and confusing. In general, the company offers affordable and competitive rates. But some tariff plans that have similar functional content to competitors, nevertheless, cost the user more.
• Insufficient coverage area. The provider's own network coverage is the weak point. According to this indicator, the company loses to both Beeline and Megafon. At the same time, the affordable cost of roaming services largely compensates for this shortcoming.
• Low quality technical support. This problem is not unique to MTS, but is common to all operators. But it is in relation to MTS that it manifests itself most clearly due to its huge customer base. Getting through to a customer support center specialist is often not just difficult, but almost impossible. Those same users who actively use the provider’s self-service services (,) do not notice this problem. This suggests that against the backdrop of the growing popularity of online services, difficulties with dialing the MTS call center are gradually losing their significance and relevance.

Megaphone

Megafon is one of the undisputed leaders of the Russian telecommunications services market. The provider has almost 15 years of experience and during this time the number of subscribers has exceeded 90 million people.

Advantages:

• The largest coverage area in Russia. Each subscriber of the company does not have to worry that in some corner of the country he will face the problem of lack of mobile communications. Even remote and sparsely populated areas of Russia are equipped with Megafon base stations. It is clear that with a low number of users, the costs of maintaining equipment cannot be fully recovered. But the company purposefully does this in order to have a clear advantage over its competitors and become the No. 1 provider in Russia.
• Active implementation of advanced technologies. Megafon carefully monitors global trends in the telecommunications market and promptly introduces promising technologies and services. It was the first to provide mobile video capabilities and provide users with high-speed mobile Internet 4G+ at 300 Mbps. The reliability and stability of the company is also evidenced by the fact that Megafon became the official mobile service provider for the 2018 FIFA World Cup.
• High internet speed. We have already mentioned that broadband Internet access at high speed is becoming a signature feature of Megafon. True, the situation here is quite specific and unusual for Russian realities. No, high-speed Internet has not gone away, but almost all full-scale tariff plans associated with it have gone to the new Megafon brand - the Yota company.

Flaws:

• Weak technical support. Let's not dwell too much on this point. Let's say that the difficulties here are the same as those faced by MTS, as well as ways to solve them using online self-service services. After registering on the provider’s website, subscribers can use functionality that allows them to independently solve a huge list of problems in setting up communications, managing their account and tariff plan. The same features are also implemented in the Megafon mobile application. Personal Area".
• Confusion of tariff plans. Compared to other providers, Megafon has the most difficult tariff plan system for an untrained user to understand. The tariffs are quite confusing, payment varies greatly depending on the region, they provide for different tariff schemes when activating additional options, many of which have archival status. When choosing a provider, such a drawback may become key and force you to purchase a SIM card from another company.

Iota

Speaking about MegaFon, we cannot ignore its subsidiary brand Yota, which offers the best tariff plans in Russia with unlimited mobile Internet. Largely due to this, Megafon’s current tariffs do not have built-in Internet traffic packages. The calculation is simple: if you want high-quality and inexpensive Internet, buy a Yota SIM card, and Megafon will provide accessible communications throughout Russia. But recently, this advantage has been significantly reduced by the operator itself, which has already provided packages of minutes, traffic and SMS for new tariffs.

Advantages:

• High-speed Internet at low cost. For just 100-150 rubles a month you can get unlimited access to social networks and instant messengers. Data transfer speed reaches 20 Mbit/s.
• Affordable tariffs. Despite the bundling of services, Yota tariff plans remain inexpensive and well-filled. For example, 5GB of Internet traffic and 150 minutes of calls throughout Russia will cost only 250 rubles per month.
• Transparent prices. In this regard, Yota compares favorably with Megafon, offering clear descriptions of tariff plans.
• Roaming-free space throughout Russia. This is an important and necessary feature of Iota. When leaving your home region for up to 30 days, there is no need to worry about increased costs due to roaming. Throughout the month, the operator provides mobile communications and Internet services at prices in your home region, regardless of your place of stay.

Flaws:

• Virtual operator factor. Yota subscribers are completely dependent on the serviceability and workload of Megafon equipment. This must be taken into account when choosing a second SIM card in order to increase communication reliability.
• Insufficient coverage area. The Yota provider is a developing brand and is not yet able to cover the same regions as Megafon. But the significance of this disadvantage is decreasing every day as the service area expands.
• SIM card differentiation. It is impossible to use the same Yota SIM card in a smartphone, tablet, modem or router. Each type of device has its own separate card, and it is impossible to “deceive” the network, since the equipment is identified by the IMEI number.

Beeline

The Beeline company is also an old-timer in the domestic mobile services market, having started its activities back in 1993. The operator's customer base exceeds 60 million people and is constantly expanding due to favorable tariffs and new loyalty programs.

Advantages:

• Variety of tariff plans and service options. Each user can easily select the optimal tariff plan for themselves within the planned mobile budget.
• Promotions and bonuses. Beeline, like no other provider, constantly offers its customers various discounts, promotions and bonuses. For example, you can connect to the premium Viasat TV package with a 25% discount, purchase modern devices on credit without overpayments, receive an additional traffic package for replenishment or an individual tariff offer, etc.
• Timely and competent technical support. Despite the fact that it can be difficult to reach the Beeline call center, subscribers can always count on a high-quality and professional solution to their problems. In addition, a mobile online self-service service is always available to users.

Flaws:

• Malfunctions. Frequent negative reviews on the Internet indicate periodic technical failures of the provider’s equipment. It gets to the point where even checking the balance using the USSD command becomes unavailable. To be fair, we note that Beeline quickly fixes problems that arise.
• Expensive roaming. This is one of the main disadvantages of Beeline. When leaving the home region, the subscriber must be prepared for sharply increased costs for poor communication.
• Poor quality of communication far from cities. Beeline does not strive to install base stations in places that are unprofitable from a monetization point of view. Therefore, as you move away from the city, the network signal begins to weaken sharply.

Tele2

We will not particularly highlight the advantages and disadvantages of the Tele2 provider. It is a legacy of Swedish investors and is now owned by the Russian financial group VTB. The company has only one obvious drawback - a relatively small coverage area. As a result, subscribers had to constantly deal with rather expensive national roaming. Recently, this problem has been solved quite effectively through the connection of a special service “Zero Everywhere”.

Low price tariffs and high-quality communications allow Tele2 to constantly increase its subscriber base, which now numbers almost 25 million users and provides the operator with 3rd place in the ranking of the most popular mobile operators in the country.

Finally

We hope that this review of the online assistant site helped you in the difficult task of selecting a provider. The final choice depends on your personal preferences and the evaluation criteria you put forward for reliability, availability and variety of the required mobile services. We would like to add that many users use several SIM cards from different operators at once in order to receive the highest quality communications and Internet.

Video: choosing the best mobile operator

04-07-2017

(4 )

1. Catherine
2. Oleg
3. Marina
4. Alexei
5. @@@@@
6. Anonymous
7. Olga
8. Michael
9. Irina
10. Anonymous

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

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

How did cellular communication come about?

The idea of ​​cellular communications was first put forward in 1947 by Bell Labs engineers Douglas Ring and Ray Young. However, real prospects for its implementation began to emerge only in the early 1970s, when company employees developed a working architecture for the cellular hardware platform.

Thus, American engineers proposed placing transmitting stations not in the center, but in the corners of the “cells,” and a little later a technology was invented that allowed subscribers to move between these “cells” without interrupting communications. After this, it remains to develop operating equipment for such 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 straight from the street and told him about his own successes.

Motorola management immediately invested $100 million in the promising project, but the technology entered the commercial market only ten years later. This delay is due to the fact that it was first necessary 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 could be charged for about 10 hours. Moreover, the device cost $3,995 - a fabulous sum at that time. Despite this, the mobile phone instantly became popular.

Why is the connection called cellular?

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

Typically, a base station in the form of a pair of iron cabinets with equipment and antennas is placed on a specially built tower, but in the city they are often placed on the roofs of high-rise buildings. On average, each station picks up signals 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 can dramatically improve coverage in places where it is needed. Cellular communications in Russia will be combined with space

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

The cellular networks of different operators are connected to each other, as well as to the landline telephone network. If the phone leaves the range of the base station, the device establishes communication with others - the connection established by the subscriber is quietly transferred to other “cells”, which ensures continuous communication while 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 capacity, long range and high penetration. This is where most mobile networks now operate.

What mobile communication standards are there?

The first mobile phones worked with 1G technologies - this is the very first generation of cellular communications, which was based on analog telecommunications standards, the main one of which was NMT - Nordic Mobile Telephone. It was intended exclusively for transmitting 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 today. Communication in this standard has become digital, and it has become possible to encrypt voice traffic and send SMS.

The data transfer rate within GSM did not exceed 9.6 kbit/s, which made it impossible to transmit video or high-quality audio. The GPRS standard, known as 2.5G, was designed 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. Subsequently, the throughput of the standard was repeatedly increased.

The most modern standard is fourth-generation 4G communications, which is intended only for high-speed data services. The throughput of the 4G network can reach 300 Mbit/s, which gives the user almost unlimited possibilities for surfing the Internet.

Cellular communications of the future

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

In 2020, the official launch of the new generation of 5G communications is expected, which will allow the transfer of large amounts of data at ultra-high speeds of up to 10 Gbit/s. In addition, the standard will allow up to 100 billion devices to be connected to high-speed Internet.

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

Low latency will enable real-time communication between vehicles and infrastructure. Reliable, always-on connectivity is expected to open the door to fully autonomous vehicles on the road 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 implementation of the project is part of the state program “Digital Economy”, recently approved by the government.

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

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

After you have dialed a friend's number, your phone contacts the Base Station (BS) closest to you via a service channel and asks to allocate a voice channel. The Base Station sends a request to the controller (BSC), which forwards it to the switch (MSC). If your friend is a subscriber to the same cellular network, then the switch will check the Home Location Register (HLR), find out where the called subscriber is currently located (at home, in Turkey or Alaska), and transfer the call to the appropriate switch from where it was sent will be sent to the controller and then to the Base Station. The Base Station will contact your mobile phone and connect you to your friend. If your friend is on a different network or you are calling a landline, your switch will contact the corresponding switch on the other network.

Difficult? Let's take a closer look.

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

2.

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

3.

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

The Base Station can operate in three bands:

900 MHz - a signal at this frequency travels further and penetrates better inside buildings
1800 MHz - the signal travels over shorter distances, but allows you to install a larger number of transmitters in 1 sector
2100 MHz - 3G network

This is what a cabinet with 3G equipment looks like:

4.

900 MHz transmitters are installed at Base Stations in fields and villages, and in the city, where Base Stations are stuck like hedgehog needles, communication is mainly carried out at a frequency of 1800 MHz, although any Base Station may have transmitters of all three ranges simultaneously.

5.

6.

A signal with a frequency of 900 MHz can reach up to 35 kilometers, although the “range” of some Base Stations located along highways can reach up to 70 kilometers, due to the reduction in the number of simultaneously served subscribers at the station by half. Accordingly, our phone with its small built-in antenna can also transmit a signal over a distance of up to 70 kilometers...

All Base Stations are designed to provide optimal radio coverage at ground level. Therefore, despite a range of 35 kilometers, a radio signal is simply not sent to the aircraft’s flight altitude. However, some airlines have already begun installing low-power base stations on their aircraft that provide coverage within 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.

The phone can measure the signal strength from 32 Base Stations simultaneously. It sends information about the 6 best (in terms of signal strength) via the service channel, and the controller (BSC) decides which BS to transfer the current call (Handover) if you are on the move. Sometimes the phone may make a mistake and transfer you to a BS with a worse signal, in which case the conversation may be interrupted. It may also turn out that at the Base Station that your phone has selected, all voice lines are busy. In this case, the conversation will also be interrupted.

They also told me about the so-called “problem of the upper floors.” If you live in a penthouse, then sometimes, when moving from one room to another, the conversation may be interrupted. This happens because in one room the phone can “see” one BS, and in the second - another, if it faces the other side of the house, and, at the same time, these 2 Base Stations are located at a great distance from each other and are not registered as " neighboring" from the mobile operator. In this case, the call will not be transferred from one BS to another:

Communication in the metro is provided in the same way as on the street: Base Station - controller - switch, with the only difference being that small Base Stations are used there, and in the tunnel, coverage is provided not by an ordinary antenna, but by a special radiating cable.

As I wrote above, one BS can make up to 432 calls simultaneously. Usually this power is enough, but, for example, during some holidays the BS may not be able to cope with the number of people wanting to call. This usually happens on New Year's Day, when everyone starts congratulating each other.

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

I was told an interesting case. In one area of ​​Moscow, subscribers began to receive complaints that they could not get through to anyone. Technical specialists began to figure it out. Most voice channels were free, but all service channels were busy. It turned out that next to this BS there was an institute where exams were going on and students were constantly exchanging text messages.

The phone divides long SMS into several short ones and sends each one separately. Technical service staff advise sending such congratulations via MMS. It will be faster and cheaper.

From the Base Station the call goes to the controller. It looks as boring as the BS itself - it’s just a set of cabinets:

7.

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

The switch looks much more interesting:

8.

9.

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

10.

11.

12.

The switch controls traffic. Remember the old movies where people first dialed the “girl”, and then she connected them to another subscriber by switching wires? Modern switches do the same thing:

13.

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

14.

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

15.

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

16.

24-hour monitoring of switches and controllers is carried out from the Mission Control Center of the Network Control Center (NCC):

17.

There are 3 main areas for monitoring the cellular network: accident rates, statistics and feedback from subscribers.

Just like in airplanes, all cellular network equipment has sensors that send a signal to the central control system and output information to dispatchers’ computers. If some equipment fails, the light on the monitor will begin to “blink.”

The CCS also tracks statistics for all switches and controllers. He analyzes it, comparing it with previous periods (hour, day, week, etc.). If the statistics of any of the nodes began to differ sharply from previous indicators, then the light on the monitor will again begin to “blink”.

Feedback is received by customer service operators. If they cannot resolve the problem, the call is transferred to a technician. If he turns out to be powerless, then an “incident” is created in the company, which is resolved by the engineers involved in the operation of the relevant equipment.

The switches are monitored 24/7 by 2 engineers:

18.

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

19.

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

22.

21.

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

Tomorrow there will be a post about how a whale jumped out in front of me, but I didn’t have time to photograph it. Stay tuned!