Cellular. Mobile cellular communications Cellular telephone communications

It is hardly possible today to find a person who has never used a cell phone. But does everyone understand how cellular communications work? How does what we have all become accustomed to work and work? Are signals from base stations transmitted through wires or does it all work somehow differently? Or maybe all cellular communications function only through radio waves? We will try to answer these and other questions in our article, leaving the description of the GSM standard outside its scope.

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

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

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

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

Of course, there may be several controllers in a populated area or region, so the controllers, in turn, are connected by cables to the switch. The purpose of the switch is to connect the networks of mobile operators with each other and with city lines of regular telephone communication, long-distance communication and international communication. If the network is small, then one switch is enough; if it is large, two or more switches are used. The switches are connected to each other by wires.

In the process of moving a person talking on a mobile phone along the street, for example: he is walking, riding in public transport, or driving a personal car, his phone should not lose the network for a moment, and the conversation cannot be interrupted.

Continuity of communication is obtained due to the ability of a network of base stations to very quickly switch a subscriber from one antenna to another as he moves from the coverage area of ​​one antenna to the coverage area of ​​another (from cell to cell). The subscriber himself does not notice how he ceases to be connected to one base station and is already connected to another, how he switches from antenna to antenna, from station to station, from controller to controller...

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

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

Next, our call goes to the switch, which is located on the side of the recipient of the call (the one we called). The “receiving” switch already has data about where the called subscriber is located, in what network coverage area: which controller, which base station. And so, a network survey begins from the base station, the recipient is located, and a call is received on his phone.

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

Andrey Povny

Operating principle of radio communication

Radio (lat. radio - I emit, I emit rays radius - ray) - a type wireless communication, in which radio waves, freely propagating in space, are used as a signal carrier.

Principle of operation
The transmission occurs as follows: a signal with the required characteristics (frequency and amplitude of the signal) is generated on the transmitting side. Next, the transmitted signal modulates a higher frequency oscillation (carrier). The resulting modulated signal is radiated into space by the antenna. On the receiving side of the radio wave, a modulated signal is induced in the antenna, after which it is demodulated (detected) and filtered by a low-pass filter (thus getting rid of the high-frequency component - the carrier). The resulting modulated signal is radiated by the antenna into space.
On the receiving side of the radio wave, a modulated signal is induced in the antenna, after which it is demodulated (detected) and filtered by a low-pass filter (thus getting rid of the high-frequency component, the carrier). Thus, the useful signal is extracted. The received signal may differ slightly from that transmitted by the transmitter (distortion due to interference and interference).

Frequency ranges
The frequency grid used in radio communications is conventionally divided into ranges:

• Long waves (LW) - f = 150-450 kHz (l = 2000-670 m)
• Medium waves (SW) - f = 500-1600 kHz (l = 600-190 m)
• Short waves (HF) - f = 3-30 MHz (l = 100-10 m)
• Ultrashort waves (VHF) - f = 30 MHz - 300 MHz (l = 10-1 m)
• High frequencies (HF-centimeter range) - f = 300 MHz - 3 GHz (l = 1-0.1 m)
• Extremely high frequencies(EHF - millimeter range) - f = 3 GHz - 30 GHz (l = 0.1-0.01 m)
• Hyper-high frequencies (HHF - micrometer range) - f = 30 GHz - 300 GHz (l = 0.01-0.001 m)

Depending on the range, radio waves have their own characteristics and propagation laws:

• LWs are strongly absorbed by the ionosphere; the main importance is ground waves that propagate around the earth. Their intensity decreases relatively quickly as they move away from the transmitter.
• SWs are strongly absorbed by the ionosphere during the day, and the area of ​​action is determined by the ground wave; in the evening, they are well reflected from the ionosphere and the area of ​​action is determined by the reflected wave.
• HF propagate exclusively through reflection by the ionosphere, so there is a so-called radio silence zone around the transmitter. During the day, shorter waves (30 MHz) travel better, and at night, longer waves (3 MHz). Short waves can travel long distances with low transmitter power.
• VHF propagates in a straight line and, as a rule, is not reflected by the ionosphere. They easily bend around obstacles and have high penetrating ability.
• HF does not bend around obstacles and propagates within the line of sight. Used in WiFi, cellular communications, etc.
• EHFs do not bend around obstacles, are reflected by most obstacles, and propagate within line of sight. Used for satellite communications.
• Hyper-high frequencies do not bend around obstacles, are reflected like light, and spread within the line of sight. Use is limited.

Radio propagation
Radio waves propagate in vacuum and in the atmosphere; the earth's surface and water are opaque to them. However, due to the effects of diffraction and reflection, communication is possible between points on the earth's surface that do not have a direct line of sight (in particular, those located at a great distance).
The propagation of radio waves from a source to a receiver can occur in several ways simultaneously. This propagation is called multipath. Due to multipath and changes in environmental parameters, fading occurs - a change in the level of the received signal over time. With multipath, a change in signal level occurs due to interference, that is, at the receiving point, the electromagnetic field is the sum of time-shifted radio waves of the range.

Radar

Radar- a field of science and technology that combines methods and means of detection, measuring coordinates, as well as determining the properties and characteristics of various objects based on the use of radio waves. A related and partly overlapping term is radio navigation, however, in radio navigation, a more active role is played by the object whose coordinates are measured, most often this is the determination of its own coordinates. The main technical device of radar is radar station(English Radar).

There are active, semi-active, active with a passive response and passive RL. They are divided according to the radio wave range used, the type of probing signal, the number of channels used, the number and type of coordinates being measured, and the location of the radar installation.

Operating principle

Radar is based on the following physical phenomena:

• Radio waves are scattered by electrical inhomogeneities encountered along the path of their propagation (objects with other electrical properties that differ from the properties of the propagation medium). In this case, the reflected wave, as well as the target radiation itself, makes it possible to detect the target.
• At large distances from the radiation source, we can assume that radio waves propagate rectilinearly and at a constant speed, due to which it is possible to measure the range and angular coordinates of the target (Deviations from these rules, which are valid only as a first approximation, are studied by a special branch of radio engineering - Radio wave propagation. In radar these deviations lead to measurement errors).
• The frequency of the received signal differs from the frequency of the emitted oscillations when the receiving and emission points move mutually (Doppler effect), which makes it possible to measure the radial speeds of the target relative to the radar.
• Passive radar uses the emission of electromagnetic waves from observed objects; this can be thermal radiation, which is characteristic of all objects, active radiation created by the technical means of the object, or side radiation created by any objects with operating electrical devices.

cellular

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

The network consists of spatially dispersed transceivers operating in the same frequency range, and switching equipment that makes it possible to determine the current location of mobile subscribers and ensure continuity of communication when a subscriber moves from the coverage area of ​​one transceiver to the coverage area of ​​another.

Operating principle of cellular communication

Main components cellular network- These are cell phones and base stations that are usually located on the roofs of buildings and towers. When turned on, the cell phone listens to the airwaves, finding a signal from the base station. The phone then sends its unique identification code to the station. The telephone and the station maintain constant radio contact, periodically exchanging packets. Communication between the phone and the station can be via an analog protocol (AMPS, NAMPS, NMT-450) or digital (DAMPS, CDMA, GSM, UMTS). If the phone leaves the range of the base station (or the quality of the radio signal from the service cell deteriorates), it establishes communication with another one. handover).

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

Cellular networks different operators connected to each other, as well as to the landline telephone network. This allows subscribers of one operator to make calls to subscribers of another operator, from mobile phones to landlines and from landlines to mobiles.

Operators can enter into roaming agreements with each other. Thanks to such agreements, a subscriber, being outside the coverage area of ​​his network, can make and receive calls through the network of another operator. As a rule, this is carried out at increased rates. The possibility of roaming appeared only in 2G standards and is one of the main differences from 1G networks.

Operators can share network infrastructure, reducing network deployment and operating costs.

Cellular services

Mobile operators provide the following services:

• Voice call;
• Autoresponder in cellular communications (service);
• Roaming;
• Caller ID (Automatic Caller ID) and Anti-Caller ID;
• Reception and transmission of short text messages (SMS);
• Reception and transmission multimedia messages- images, melodies, videos (MMS service);
• Mobile bank(service);
• Access to the Internet;
• Video call and video conference

A television

A television(Greek τήλε - far and lat. video- I see; from New Latin televisio- far vision) - a set of devices for transmitting moving images and sound over a distance. In everyday life it is also used to refer to organizations involved in the production and distribution of television programs.

Basic principles

Television is based on the principle of sequential transmission of image elements using a radio signal or wires. The image is decomposed into elements using a Nipkow disk, cathode ray tube or semiconductor matrix. The number of image elements is selected in accordance with the radio channel bandwidth and physiological criteria. To narrow the bandwidth of transmitted frequencies and reduce the noticeability of flickering on the TV screen, interlaced scanning is used. It also allows you to increase the smoothness of motion transmission.

The television channel in general includes the following devices:

1. Television transmission camera. Serves to convert the image obtained using a lens on the target of the transmitting tube or semiconductor matrix into a television video signal.
2. Video recorder. Records and plays back a video signal at the right time.
3. Video mixer. Allows you to switch between several image sources: video cameras, VCRs and others.
4. Transmitter. The radio frequency signal is modulated by the television video signal and transmitted by radio or wire.
5. Receiver - TV. With the help of synchronization pulses contained in the video signal, the television image is reproduced on the receiver screen (kinescope, LCD display, plasma panel).

In addition, to create a television broadcast, an audio path similar to the radio transmission path is used. Sound is transmitted at a separate frequency, usually using frequency modulation, using technology similar to FM radio stations. IN digital television audio, often multi-channel, is transmitted in a common data stream with the image.

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) to find out where in this moment the called subscriber is located (at home, in Turkey or in Alaska), and will transfer the call to the appropriate switch, from where it will forward it 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:

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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:

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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 - the signal at this frequency travels further and penetrates better inside buildings 1800 MHz - the signal travels over shorter distances, but allows you to install large quantity transmitters on 1 sector 2100 MHz - 3G network This is what a cabinet with 3G equipment looks like:

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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.

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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 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 “upper floor problem.” 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 when everyone starts congratulating each other. SMS are transmitted via service channels. On March 8 and February 23, people prefer to congratulate each other on via SMS, sending funny poems, and the 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 employees advise sending such congratulations on 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:

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

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

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Inside there is equipment that makes hundreds of calls and takes 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 accepted by subscriber 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:

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

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

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

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

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

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

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

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

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

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

How mobile communication works

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

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

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

How cellular communications work (for dummies)

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

The switching center is looking for a base station with the maximum signal strength cell phone cellular subscriber and switches the conversation to it.

Early telephone system architecture

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

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

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

An urban area is configured as a traditional mobile phone network with one powerful transmitter.

Mobile communication system using cellular concept

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

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

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

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

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

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

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

Cellular System Architecture

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

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

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

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

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

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

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

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

Obstacles in the development of cellular communications

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

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

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

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

Cellular System Components

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

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

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

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

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

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

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

Maliciousness of cell towers

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

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

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

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

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

Cellular communications in Russia

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

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

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

The service allows you to hide the identification of your mobile phone number when calling the numbers of other subscribers. The service works correctly when the calling and called subscribers are located in the Moscow region. The operation of the service is not guaranteed for outgoing calls to phones of subscribers of networks other than Rostelecom, including public city networks.

Automatic Caller ID (ANI) allows you to find out the name or number from which incoming call, find out the numbers of the latest incoming calls - received or missed, set different ringtones for the numbers. The service is connected to all subscribers free of charge.

Short Message Service - short message transmission service. The service provides the transmission and reception of short text messages via a digital cellular network.

Additional parameters that are not listed should be left at their default values. After manual settings phone, send an MMS to any recipient, for example, to your own number. This is necessary to register your number in the Rostelecom network as a user of the MMS service.

Basic settings mobile internet. To configure your phone to access the Internet or to work from a computer using the phone as a modem, you need to set the following parameters:

The service provides the opportunity to communicate with several interlocutors at the same time, which is convenient for conducting business negotiations when it is impossible to quickly gather all those responsible and interested in the discussion for a personal meeting. If you need to communicate with several friends at the same time. Up to 6 subscribers can participate in the conference simultaneously, including the call initiator.

The conference initiator has the ability to connect subscribers of both fixed and mobile networks to the conversation; switch the current conference to standby mode (in this case, participants will continue telephone communication). Make outgoing calls, answer incoming calls, join or remove participants from a conversation. These actions can be performed through the phone menu. Conference calling of incoming calls is available when the Call Waiting service is active.

Conference participants have the ability to make outgoing and receive incoming calls without interrupting the conference, leave the conference without interrupting the communication of other participants (if the initiator leaves, the remaining participants will be automatically disconnected).

You won't miss a single call. The service will report all missed calls during the time when the phone was out of network coverage or turned off.

The service is provided to Rostelecom subscribers when they are in the Moscow region and in roaming.

If the balance is close to zero and there is no way to top up your account, you can use the “Promised Payment” service to make a temporary payment and continue communication.

Receipt of the Promised Payment is possible immediately after the previously credited payment has been written off.

The service allows you not to miss an important call, even if it comes during a conversation with another interlocutor. A special sound signal will notify you of a new call. Following the phone prompts, you can choose who to talk to first, or communicate alternately with both interlocutors.

The service is included in the tariff.

"Social networks" is unlimited internet traffic to the most popular social networks “Facebook”, “VKontakte”, “Odnoklassniki”. Option included in subscription fee all new tariff plans valid from September 20, 2017, except for the “For Unlimited” tariff plan, the “Endless Story” tariff plan, and cannot be disabled.

“Messengers” - unlimited Internet traffic, the most popular instant messengers “WhatsApp”, “Viber”, “TamTam”. The option is included in the subscription fee of new tariff plans“SUPER SIM S”, “SUPER SIM M”, “SUPER SIM L”, “SUPER SIM XL” (from 09/20/17) and cannot be disabled.

The option is valid when you are in your home region and when traveling around Russia with the exception of the Republic of Crimea and the city of Sevastopol. If pages, links or videos are opened through the sites or applications “Facebook”, “VKontakte”, “Odnoklassniki”, the display of which requires a connection to other sites, Internet traffic is paid by the subscriber in accordance with the current tariff plan and options.

Can be connected to archived TPs via USSD command.

"Navigation" - unlimited Internet traffic when using the applications "Yandex.Maps", "Yandex.Navigator" and "Yandex.Transport". The option is valid when you are in your home region and when traveling around Russia with the exception of the Republic of Crimea and the city of Sevastopol. If pages, links or videos are opened through the sites or applications “Facebook”, “VKontakte”, “Odnoklassniki”, the display of which requires a connection to other sites, Internet traffic is paid by the subscriber in accordance with the current tariff plan and options.

It can be connected both to archived tariff plans and to new tariff plans, except for the “For Unlimited” tariff plan, the “Endless Story” tariff plan, via the USSD command.

Absolute forwarding (ALL CALLS) ensures that all incoming calls are transferred to a specified phone number.

Forwarding, when busy phone(IF BUSY), transfers incoming calls to the specified phone number when the subscriber's phone is busy.

Forwarding if the subscriber is unavailable (WHEN UNREACHABLE) ensures that incoming calls are transferred to a specified telephone number if the subscriber is out of the service area or has turned off his device.

Forwarding, if there is no answer (IF NO REPLY), transfers incoming calls to a specified telephone number if the subscriber pressed the end call button or did not answer the call within the time interval set by him: 5, 10, 15, 20, 25 or 30 seconds ( By default, the system sets the interval to 30 seconds).

Cancel all redirects.

The additional service “Exchange Minutes” is an opportunity to exchange your minutes for Internet traffic. The service is provided free of charge on tariff plans open for connection, subject to the charging of the subscription fee established for the subscriber’s chosen tariff.

Exchange rate:
1 minute = 10.24 MB
10 minutes = 102.4 MB
100 minutes = 1 GB

Peculiarities:
- You can exchange minutes both from the main package included in the tariff, and those received as part of the transfer of package balances from the previous month.
- You can exchange any number of minutes at any time after the main package is assigned, but no more than 10 times a month.
- Minutes cannot be exchanged while the “Add traffic”/ “500MB+”/ “1GB+” options are in effect
- Exchanged GB are included in the main package. First of all, Internet traffic from the transferred package is consumed, after it is exhausted - from the main Internet traffic package.
- Exchanged GB are transferred to the next billing period in an amount no more than the volume of two packages at the main tariff.
- When changing tariff plan unused Internet traffic is burned.
- Exchange of minutes is available in roaming, including the ability to use exchange traffic while roaming.
- The service can be used throughout Russia, with the exception of the Republic of Crimea and the city of Sevastopol.

The service is provided when you are in your home region. The subscription fee is charged only on the days when SMS is sent. The subscription fee includes 100 SMS messages per day. The service is not compatible with other SMS discounts.

CONNECTION	DISCONNECT	CHECKING STATUS	CONNECTION COST	SUBSCRIPTION FEE
*100*334*1# call	*100*334*0# call	*100*334*2# call	0 / 20 rub.	15 rub./day

Discount on international calls to certain directions - a single set of directions and cost in all regions.

Management and cost of service

Cost of a call with the option connected

Direction	Price
Uzbekistan, Europe and the Baltics, Vietnam, Thailand, Japan, Israel, Brazil, Argentina, Colombia	5 rub./min.
Kazakhstan (except prefix 876)	6 rub./min.
Tajikistan, Ukraine, Kyrgyzstan, Turkmenistan, Türkiye	9 rub./min.
Armenia, Georgia, Abkhazia, Azerbaijan, Moldova, Estonia	15 rub./min.
Belarus	25 rub./min.
Montenegro, Bosnia and Herzegovina, Serbia, Switzerland, Slovenia, Albania, Macedonia, Monaco, Andorra, Liechtenstein, San Marino, Vatican	Basic cost
China, USA and Canada	0.80 RUR/min
South Korea, India, Mongolia	1.5 rub./min.

Additional packages of Minutes and SMS are activated on the following package tariff plans: “Super SIM” line (M, L, XL), “For All” line (L, XL, 2XL).

Price

Tariff plan		First/subsequent connections	Subscription fee
TP "Supersimka M", TP "New history. Everywhere", TP "New history. In conversation"	100 minutes of outgoing calls to numbers of operators in your home region
TP "Supersimka L", TP "Supersimka XL", TP "On all L", TP "On all XL", TP "Whole history", TP "Family history"	100 minutes of outgoing calls to Russian operator numbers
TP "For the Internet everywhere", TP "For impressions everywhere"	50 minutes of outgoing calls to numbers of operators in your home region
TP "For Unlimited", TP "For Family", "TP "Endless Story"	50 minutes of outgoing calls to Russian operator numbers
All tariffs	100 SMS to home region

The package of minutes is not connected to the SuperSimka Free tariff plan, the SuperSimka S tariff plan, and the New History tariff plan. Online".
The SMS package is not connected to the SuperSimka Free and SuperSimka S tariff plans.

Control

X-number of simultaneously connected packages
The choice of available package of minutes will be determined by the tariff plan itself.

Features of use

If there are not enough funds on your personal account balance to pay for all packages in full, only the subscription fee for the tariff will be charged, and all additional packages will be disabled. To use packages in the next billing period, they must be activated.

Maximum amount connections of the available package of minutes per month – 5.

The maximum number of SMS package connections per month is 5.

The number of simultaneously connected packages of one type of service is not limited, but no more than 5.

The total available number of simultaneously connected packages is 10 (5 minute packages + 5 SMS packages).

Connection is possible even if the main package is not used up.

Not available for participants of the “Year Without Worries” campaign.

The "Exchange Minutes" option is available.

When the service is disconnected, the unused volume remains and can be used until the end of the subscriber's billing period.

Unused packages are carried over to the next month.

Additional packages of minutes are available for use only when you are in the connection region.

The SMS Package includes messages to subscriber numbers of all Russian telecom operators.

Select a package of the required volume, and if necessary, add the required number of SMS within the current month:

Connection cost:

Control:

	Team uniform	Connection	Shutdown	Checking status
Package 100 SMS
		390*1 to number 100	390*0 to number 100	390*2 to number 100
Package Plus 100 SMS
		392*1 to number 100	392*0 to number 100	392*2 to number 100
Package 300 SMS
		391*1 to number 100	391*0 to number 100	391*2 to number 100
Package Plus 300 SMS
		393*1 to number 100	393*0 to number 100	393*2 to number 100

The subscription fee for services is charged in full at the time access to the service is provided and then monthly as long as the service is active for the Subscriber.

If there are insufficient funds for the next debit of the subscription fee, the provision of the service is suspended. When you top up your account, the service is automatically resumed.

In case of deactivation of the “Package 100 SMS” or “Package 300 SMS” services before it is exhausted, the SMS provided under the Package can be used until the end of the billing period/month.

The volume of SMS provided under the Package that is not used in the current billing period is transferred to the next period, subject to timely payment of the subscription fee.

Outgoing SMS to short numbers, as well as to the numbers of content providers are not included in the Package and are charged in accordance with the terms of the subscriber’s connected tariff plan.

The service is incompatible with other discounts on SMS, except for the packages included in the subscription fee for the “Plus 100 SMS” and “Plus 300 SMS” tariff and services.

When connecting SMS packages to packaged TPs with included SMS volumes, spent on numbers of any operators in the home region, when sending SMS to numbers in the home region, the SMS package included in the TP is consumed first, after it is exhausted, SMS are consumed from the packages provided within the " 100 SMS", "300 SMS".

Features of using the services “Package 100 SMS” or “Package 300 SMS”:

You can additionally activate the “Plus 100 SMS” or “Plus 300 SMS” service. The packages are activated independently by the subscriber when the “100 SMS” or “300 SMS” Packages are exhausted and are valid until the volume of messages is exhausted or until the end of the current period in which they were connected.

The number of connections per month is unlimited.

Available for use only when located in the connection region.