Principles of construction of cellular communication systems. Why is a mobile phone called a cellular phone

Mobile cellular

cellular- one of the types of mobile radio communications, which is based on cellular network. The key feature is 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 composed of them looks like honeycombs with hexagonal cells (honeycombs).

It is noteworthy that in the English version the connection is called "cellular" or "cellular" (cellular), which does not take into account the hexagonal cells.

The network consists of transceivers spaced apart in space operating in the same frequency range, and switching equipment that allows you to determine the current location of mobile subscribers and ensure communication continuity when a subscriber moves from the coverage area of ​​one transceiver to the coverage area of ​​another.

Story

The first use of mobile telephone radio in the United States dates back to 1921 when the Detroit police used one-way dispatch communication in the 2 MHz band to transmit information from a central transmitter to vehicle-mounted receivers. In 1933, the NYPD began using a two-way mobile telephone radio system, also on the 2 MHz band. In 1934, the US Federal Communications Commission allocated 4 channels for telephone radio communications in the range of 30 ... 40 MHz, and in 1940, about 10 thousand police vehicles were already using telephone radio communications. All of these systems used amplitude modulation. Frequency modulation began to be used in 1940 and by 1946 had completely supplanted amplitude modulation. The first public mobile radiotelephone appeared in 1946 (St. Louis, USA; Bell Telephone Laboratories), it used the 150 MHz band. In 1955, an 11-channel system began operating in the 150 MHz band, and in 1956, a 12-channel system in the 450 MHz band. Both of these systems were simplex and used manual switching. Automatic duplex systems began operating in 1964 (150 MHz) and 1969 (450 MHz) respectively.

In the USSR In 1957, a Moscow engineer L. I. Kupriyanovich created a prototype of a wearable automatic duplex mobile radiotelephone LK-1 and a base station for it. The mobile radiotelephone weighed about three kilograms and had a range of 20-30 km. In 1958, Kupriyanovich created improved models of the apparatus, weighing 0.5 kg and the size of a cigarette box. In the 1960s, Christo Bochvarov demonstrated his prototype of a pocket mobile radiotelephone in Bulgaria. At the Interorgtekhnika-66 exhibition, Bulgaria presents a set for organizing local mobile communication from PAT-0.5 and ATRT-0.5 pocket mobile phones and a RATC-10 base station that connects 10 subscribers.

At the end of the 50s, the development of the Altai car radiotelephone system began in the USSR, which was put into trial operation in 1963. The Altai system initially operated at a frequency of 150 MHz. In 1970, the Altai system operated in 30 cities of the USSR and a 330 MHz band was allocated for it.

Similarly, with natural differences and on a smaller scale, the situation developed in other countries. Thus, in Norway, public telephone radio has been used as maritime mobile communications since 1931; in 1955 there were 27 coastal radio stations in the country. Land mobile communications began to develop after World War II in the form of private hand-switched networks. Thus, by 1970, mobile telephone radio communication, on the one hand, had already become quite widespread, but on the other hand, it clearly did not keep pace with rapidly growing needs, with a limited number of channels in strictly defined frequency bands. The solution was found in the form of a cellular communication system, which made it possible to dramatically increase the capacity due to the reuse of frequencies in a system with a cellular structure.

Of course, as is usually the case in life, individual elements of the cellular communication system existed before. In particular, some semblance of a cellular system was used in 1949 in Detroit (USA) by a taxi dispatch service - with the reuse of frequencies in different cells with manual channel switching by users in predetermined places. However, the architecture of the system that is today known as a cellular communication system was only outlined in a technical report by the Bell System company, submitted to the US Federal Communications Commission in December 1971. And from that time, the development of cellular communication proper began, which became truly triumphant since 1985 in the last ten plus years.

In 1974, the US Federal Communications Commission decided to allocate a 40 MHz frequency band for cellular communications in the 800 MHz band; in 1986 another 10 MHz was added to it in the same range. In 1978, Chicago began testing the first experimental cellular communication system for 2,000 subscribers. Therefore, 1978 can be considered the year of the beginning of the practical application of cellular communications. The first automatic commercial cellular communication system was also put into operation in Chicago in October 1983 by American Telephone and Telegraph (AT&T). Cellular communication has been used in Canada since 1978, in Japan since 1979, in Scandinavian countries (Denmark, Norway, Sweden, Finland) since 1981, in Spain and England since 1982. As of July 1997 Cellular communications operated in more than 140 countries on all continents, serving more than 150 million subscribers.

The first commercially successful cellular network was the Finnish Autoradiopuhelin (ARP) network. This name is translated into Russian as "Car Radiotelephone". Launched in the city, it reached 100% coverage of the territory of Finland in. The size of the cell was about 30 km, in the city it had more than 30 thousand subscribers. She worked at a frequency of 150 MHz.

The principle of operation of cellular communication

The main components of the cellular network are cell phones and base stations. Base stations are usually located on the roofs of buildings and towers. When turned on, the cell phone listens to the air, 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 go on an analog protocol (NMT-450) or digital (DAMPS, GSM, eng. handover).

Cellular networks can consist of base stations of different standards, which allows you to optimize the network and improve its coverage.

Cellular networks of different operators are connected to each other, as well as to the fixed 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 from different countries can enter into roaming agreements. Thanks to such contracts, the subscriber, while abroad, can make and receive calls through the network of another operator (though at higher rates).

Cellular communication in Russia

In Russia, cellular communication began to be introduced in 1990, commercial use began on September 9, 1991, when in St. Petersburg, Delta Telecom launched the first cellular network in Russia (it worked in the NMT-450 standard) and a symbolic cellular call by the mayor of St. Petersburg, Anatoly Sobchak. By July 1997, the total number of subscribers in Russia was about 300,000. For 2007, the main cellular communication protocols used in Russia are GSM-900 and GSM-1800. In addition, UMTS also works. In particular, the first fragment of the network of this standard in Russia was put into operation on October 2, 2007 in St. Petersburg by MegaFon. In the Sverdlovsk region, the DAMPS standard cellular communication network, owned by the Motiv Mobile Communications company, continues to operate.

In December 2008, there were 187.8 million cellular users in Russia (according to the number of SIM cards sold). The penetration rate of cellular communications (number of SIM-cards per 100 inhabitants) on that date was thus 129.4%. In the regions, excluding Moscow, the penetration rate exceeded 119.7%.

The market share of the largest cellular operators as of December 2008 was: 34.4% for MTS, 25.4% for VimpelCom and 23.0% for MegaFon.

In December 2007, the number of cellular users in Russia increased to 172.87 million subscribers, in Moscow - up to 29.9, in St. Petersburg - up to 9.7 million. The level of penetration in Russia - up to 119.1%, Moscow - 176% , St. Petersburg - 153%. The market share of the largest cellular operators as of December 2007 was: MTS 30.9%, VimpelCom 29.2%, MegaFon 19.9%, other operators 20%.

According to the data of the British research company Informa Telecoms & Media for 2006, the average cost of a minute of cellular communication for a consumer in Russia was $0.05 - this is the lowest figure among the G8 countries.

Based on a study of the Russian cellular communications market, IDC concluded that in 2005 the total duration of conversations on the cell phone of the inhabitants of the Russian Federation reached 155 billion minutes, and 15 billion text messages were sent.

According to a study by J "son & Partners, the number of SIM cards registered in Russia at the end of November 2008 reached 183.8 million.

see also

Sources

Links

  • Information site about generations and standards of cellular communications.
  • Cellular communications in Russia 2002-2007, official statistics

Mobile communication, which operates today around the world, is traditionally considered a relatively new invention. However, the first concepts of mobile communications infrastructure organization appeared at the beginning of the 20th century. It is difficult to answer the question in which country the first mobile phones appeared and when. But if you try to do this - what facts about the development of telephone communications using radio equipment should be studied first of all? Based on what criteria should certain devices be classified as mobile phones?

The History of Mobile Phones: Basic Facts

To answer the question - who invented the first mobile phone in the world, we can, first of all, familiarize ourselves with the history of the creation of the corresponding communication devices.

Concepts and prototypes of communication devices, from a functional point of view, close to mobile phones, began to be discussed in various communities (scientific, engineering) as early as the beginning of the 20th century. But in the late 70s, the cell phone itself as a subscriber means of communication was proposed to be developed by the Bell Laboratories, which belonged to one of the largest American corporations, AT&T. Finland was one of the first states to successfully introduce commercial mobile communication systems. Mobile communication systems were also actively developed in the USSR.

But which state was ahead of the rest in terms of the introduction of mobile phones?

It will be useful to dwell in more detail on Soviet inventions - getting acquainted with the facts about them will help us understand when the first mobile phone appeared in the world and in which country.

During the Great Patriotic War, the idea of ​​creating a special device, a monophone, was proposed by the Soviet scientist Georgy Ilyich Babat. This device was supposed to be a portable telephone operating in automatic mode. It was assumed that it would operate in the range of 1-2 GHz. The principal feature of the apparatus proposed by G.I. Babat, was to provide voice transmission through an extensive network of special waveguides.

In 1946, G. Shapiro and I. Zakharchenko proposed to organize a radiotelephone communication system, in which devices for receiving and transmitting voice were to be placed in cars. In accordance with this concept, the basis of the mobile communication infrastructure should have been existing city stations, supplemented with special radio equipment. It was supposed to use special call signs as a subscriber identifier.

In April 1957, Soviet engineer Leonid Ivanovich Kupriyanovich created a prototype communication device - the LK-1 radiotelephone. This device had a range of about 30 km and had a significant weight - about 3 kg. He could provide communication through interaction with a special automatic telephone exchange, which could connect to city telephone lines. Subsequently, the phone has been improved. Is not it. Kupriyanovich significantly reduced the weight and dimensions of the device. In the updated version, the size of the apparatus was approximately equal to the size of 2 cigarette boxes stacked on top of each other. The weight of the radiotelephone was about 500 grams, including the battery. It was expected that the Soviet mobile phone would be widely used in the national economy, in everyday life and would become the subject of personal use of citizens.

Radiotelephone L.I. Kupriyanovich allowed not only making calls, but also receiving them - subject to the assignment of a personal number, as well as the use of infrastructure that allows you to transmit signals from the PBX to automatic telephone radio stations, and from them to subscriber devices.

Research in the field of mobile communications was also carried out in other socialist countries. For example, in 1959, the Bulgarian scientist Hristo Bachvarov developed a mobile device similar in basic principle to L.I. Kupriyanovich, and patented it.

Can we say that the world's first mobile phone was invented in this way in the USSR or in other socialist countries?

Criteria for classifying devices as mobile phones

First of all, it is worth deciding what to consider, in fact, a mobile phone. In accordance with the common definition, this should be considered a device that:

Compact (a person can carry it with him);

Works using radio channels;

Allows one subscriber to call another using a unique number;

Integrated in a certain way with wired telephone networks;

Publicly available (the ability to connect does not require permission from any competent authorities and is limited by the financial and infrastructural resources of subscribers).

From this point of view, a full-fledged mobile phone has not yet been invented. But, of course, the above criteria for determining a mobile phone cannot be considered universal. And if we remove from them, in particular, accessibility and compactness, then the rest may well correspond to the Soviet Altai system. Let's consider its features in more detail.

Soviet experience in the development of mobile communications: the Altai system

When studying the question of which is the very first mobile phone in the world, it is useful to familiarize yourself with the basic facts about the corresponding communication system. The devices connected to it had, in principle, all the signs of a mobile phone, except for general availability. This system is thus:

Allowed some subscribers to call others by numbers;

It was in a certain way integrated with city networks.

But it was not publicly available: subscriber lists were approved at the departmental level. The Altai system was launched in the 60s in Moscow, and in the 70s it was deployed in more than 100 cities of the USSR. It was actively used during the 1980 Olympics.

There were plans in the USSR to create a mobile communication system to which everyone could connect. But due to the economic and political difficulties of the mid-late 80s, work on the development of this concept was curtailed.

In post-Soviet Russia, Western cellular standards were introduced. By that time, they had been providing communications between devices for quite a long time, which could be called full-fledged mobile phones. Let us study how the corresponding standards developed in the West. This, again, will help us answer the question of where and when the world's first mobile phone appeared.

History of mobile communications in the United States

As we noted at the beginning of the article, prototypes of mobile phones in the West began to appear as early as the beginning of the 20th century. In the 1930s and 1940s, real developments began to take root. In 1933, NYPD vehicles could communicate using half-duplex radio transmitters. In 1946, a mobile network was deployed in which private subscribers could communicate with each other using radio equipment through the mediation of an operator. In 1948, an infrastructure was launched that allowed one subscriber to call another in automatic mode.

Is it possible to say that it was in the USA that the world's first mobile phone was thus invented? If we consider the above criteria for classifying a radiotelephone as a device of the appropriate type - yes, you can say so, but in relation to later American developments. The fact is that the principles of its functioning of American cellular networks of the 40s were very far from those that characterize modern

Systems like those deployed in Missouri and Indiana in the 1940s had significant frequency and channel limitations. This did not allow a sufficiently large number of subscribers to be connected to mobile networks at the same time. The solution to this problem was proposed by Bell specialist D. Ring, who proposed dividing the radio signal propagation area into cells or cells, which would be formed by special base stations operating at different frequencies. This principle, in general, is also implemented by modern cellular operators. The implementation of the concept of D. Ring in practice was carried out in 1969.

History of mobile communication in Europe and Japan

In Western Europe, the first telephone systems using radio equipment were tested in 1951. In the 1960s, work in this direction was actively carried out in Japan. It is noteworthy that it was the Japanese developers who found that the optimal frequency for deploying mobile communications infrastructure is 400 and 900 MHz. Today, these frequencies are among the main ones used by cellular operators.

Finland has become one of the leading countries in terms of introducing developments in the field of organizing the functioning of a full-fledged cellular network. In 1971, the Finns began to deploy a commercial cellular network, the coverage of which by 1978 reached the size of the entire country. Does this mean that the very first mobile phone in the world, functioning according to modern principles, appeared in Finland? There are certain arguments in favor of this thesis: in particular, the fact that Finnish telecommunications corporations are deploying the corresponding infrastructure across the country has been established. But in accordance with the traditional point of view, such a device nevertheless appeared in the United States. The main role in this, again, if we consider the popular version, was played by Motorola.

Cellular Concepts from Motorola

In the early 1970s, very tough competition developed between service and equipment providers in the United States in a promising market segment - in the field of cellular communications. The main rivals here are AT&T and Motorola. At the same time, the first company focused on the deployment of automotive communication systems - by the way, like the telecommunications corporations in Finland, the second - on the introduction of compact devices that any subscriber could carry with them.

The second concept won, and on its basis, Motorola Corporation began the deployment of a cellular network that is actually complete in the modern sense using compact devices. The world's first mobile phone within the Motorola infrastructure, again, in accordance with the traditional approach, was used as a subscriber device in 1973. After 10 years, a full-fledged commercial network was launched in the United States, to which ordinary Americans could connect.

Consider what was the world's first mobile phone, invented, in accordance with the popular point of view, the engineers of the American company Motorola.

The first cell phone: specifications

We are talking about the Motorola DynaTAC device. He weighed about 1.15 kg. Its size was 22.5 x 12.5 x 3.75 cm. It had number keys for dialing a number, as well as two special buttons for sending a call, as well as ending a call. The device had a battery, thanks to which it could function in call waiting mode for about 8 hours, and in talk mode for about 1 hour. It took more than 10 hours to charge the battery of the first cell phone.

What does the world's first mobile phone look like? A photo of the device is below.

Subsequently, Motorola released a number of upgraded versions of the device. If we talk about Motorola's commercial network, the first mobile phone in the world was made for the corresponding infrastructure in 1983.

We are talking about the device Motorola DynaTAC 8000X. This device weighed about 800 grams, its dimensions were comparable to the first version of the device. It is noteworthy that 30 subscriber numbers could be stored in his memory.

Who invented the first mobile phone?

So, let's try to answer our main question - who invented the world's first mobile phone. The history of the development of telephone communications using radio equipment suggests that the very first device that fully met the criteria for referring to mobile phones, which are still relevant today, was invented by Motorola in the USA and shown to the world in 1973.

However, it would be wrong to say that this corporation has introduced a fundamentally new development. Mobile phones - in the sense that they were radio equipment and provided communication between subscribers using a unique number - were used by that time in the USSR, Europe, and Japan. If we talk about when the world's first mobile phone was commercialized, the company that developed it launched the corresponding business in 1983, later than, in particular, similar projects were introduced in Finland.

Thus, Motorola Corporation can rightfully be considered the first to offer a mobile phone in the modern sense - in particular, functioning on the principle of distributing base stations over cells, and also having a compact format. Thus, if we talk about exactly where the world's first mobile phone was invented, in which country - as a portable, compact device that is part of the cellular communication infrastructure, then it would be legitimate to determine that the United States became this state.

At the same time, it is worth noting that the Soviet Altai system functioned quite successfully even without the introduction of American-style technologies. Thus, engineers from the USSR proved in principle the possibility of deploying a mobile communication infrastructure on a national scale, in fact, without using the principles of distribution of base stations over cells.

It is possible that without the economic and political problems of the 1980s, the USSR would have introduced its own mobile networks operating on the basis of alternative concepts to the American ones, and they would have worked no worse. However, the fact is that today Russia uses cellular communication standards developed in the Western world, which offered and commercialized the first mobile phones.

It is worth noting that the Altai system actually worked until 2011. Thus, Soviet engineering developments remained relevant for a long time, and this may indicate that, with the necessary refinement, they could compete with foreign concepts for building a cellular communication infrastructure.

Summary

So, who invented the world's first mobile phone? It is difficult to answer this question briefly. If a mobile phone is understood as a compact subscriber radio equipment integrated with city networks, operating on a cellular basis and available to everyone, then, probably, this infrastructure was first introduced by the American company Motorola.

Speaking of the first commercial cellular networks - those, probably on a national scale, were introduced in Finland, but with the use of devices focused on placement in cars. Non-commercial closed mobile networks were also successfully deployed, in fact, on a national scale, in the USSR.

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 Beeline and tried to figure out how cellular communication works ...

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 a signal from mobile phones at a distance of up to 35 kilometers and communicates with a mobile phone via service or voice channels.

After you dialed a friend's number, your phone contacts the nearest Base Station (BS) via a service channel and asks you to allocate a voice channel. The base station sends the request to the controller (BSC), which forwards it to the switch (MSC). If your friend is on the same cellular network, the switch will check the Home Location Register (HLR), find out where the called party is currently located (at home, in Turkey or Alaska), and transfer the call to the appropriate switch where he forward to the controller and then to the Base Station. The Base Station will contact the mobile phone and connect you with a friend. If your friend is a subscriber of another network or you call a landline phone, then your switch will contact the corresponding switch of another network. Hard? Let's take a closer look. The Base Station is a pair of iron cabinets locked in a well-air-conditioned room. Given that in Moscow it was +40 on the street, I wanted to live in this room for a while. Usually, the Base Station is located either in the attic of the 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 one connects the Base Station with the controller:

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Each sector can serve up to 72 calls at the same time, depending on the setup and configuration. A Base Station can consist of 6 sectors, so one Base Station can serve up to 432 calls, however, there are usually fewer transmitters and sectors installed in the station. 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 spreads further and penetrates better inside buildings 1800 MHz - the signal spreads over shorter distances, but allows you to install more transmitters on 1 sector 2100 MHz - 3G network This is how the cabinet looks like with 3G equipment:

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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 needles in a hedgehog, communication is mainly carried out at a frequency of 1800 MHz, although transmitters of all three bands can be present at any Base Station at the same time.

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A 900 MHz signal can reach up to 35 kilometers, although the "range" of some Base Stations along the routes can reach up to 70 kilometers, by reducing 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 up to 70 kilometers... All Base Stations are designed to provide optimum ground level radio coverage. Therefore, despite the range of 35 kilometers, the radio signal is simply not sent to the altitude of the aircraft. However, some airlines have already begun installing low-powered base stations on their aircraft that provide coverage inside the aircraft. Such a BS is connected to the terrestrial cellular network using a satellite channel. The system is complemented by a control panel that allows the crew to turn the system on and off, as well as certain types of services, such as turning off the voice on night flights. The phone can measure signal strength from 32 Base Stations simultaneously. It sends information about the 6 best (by signal level) via the service channel, and the controller (BSC) decides which BS to transmit the current call (Handover) if you are on the move. Sometimes the phone 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. I was also told about the so-called "top floor problem". If you live in a penthouse, then sometimes, when moving from one room to another, the conversation may be interrupted. This is because in one room the phone can "see" one BS, and in the second - another, if it goes to the other side of the house, and, at the same time, these 2 Base Stations are at a great distance from each other and are not registered as " neighboring” from a mobile operator. In this case, the transfer of a call from one BS to another will not occur:

Communication in the metro is provided in the same way as on the street: Base Station - controller - switch, with the only difference that small Base Stations are used there, and in the tunnel the coverage is provided not by an ordinary antenna, but by a special radiating cable. As I wrote above, one BS can make up to 432 calls at the same time. Usually this power is enough for the eyes, but, for example, during some holidays, the BS may not be able to cope with the number of people who want to call. This usually happens on New Year's Eve, when everyone starts to congratulate each other. SMS are transmitted through service channels. On March 8 and February 23, people prefer to congratulate each other via SMS, sending funny rhymes, and phones often cannot agree with the BS on the allocation of a voice channel. I was told an interesting story. From one district of Moscow, complaints began to come from subscribers that they could not get through anywhere. Technicians began to understand. Most of the voice channels were free, and all service channels were busy. It turned out that next to this BS there was an institute where exams were taking place and students were constantly exchanging text messages. The phone divides long SMS into several short ones and sends each one separately. Employees of the technical service are advised to send such congratulations using MMS. It will be faster and cheaper. From the Base Station, the call goes to the controller. It looks as boring as the BS itself - it's just a set of cabinets:

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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 movement of the subscriber, 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 already occupies a large hall filled with various cabinets with equipment:

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The switch performs traffic control. Remember the old movies where people first called the “girl”, and then she connected them with another subscriber, rewiring the wires? Modern switches do the same:

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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 colleagues from the "Big Three":

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

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

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

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There are 3 main areas for monitoring the cellular network: accident rate, statistics and feedback from subscribers. Just like in airplanes, all cellular network equipment has sensors that send a signal to the MCC and output information to the dispatchers' computers. If some equipment is out of order, then the light on the monitor will “blink”. The MSC also keeps track of statistics for all switches and controllers. He analyzes it by comparing it with previous periods (hour, day, week, etc.). If the statistics of one of the nodes began to differ sharply from the previous indicators, then the light on the monitor will again begin to “blink”. Feedback is received by subscriber service operators. If they cannot solve the problem, then the call is transferred to a technical specialist. If he turns out to be powerless, then an “incident” is created in the company, which is solved by engineers involved in the operation of the corresponding equipment. The switches are monitored around the clock by 2 engineers:

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

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

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Introduction

Algorithm for the functioning of cellular communication systems

Initialization and communication

Authentication and identification

Handoff (in routing)

Roaming

GSM call service

Conclusion

Introduction

The computerization of telecommunications equipment goes hand in hand with the processes of privatization of national communication systems, the emergence of large firms - operators on the market, which leads to increased competition. As a result, prices for telecommunication services are reduced, their range is expanding, and users have a choice.

Most industrialized countries are intensively moving to a digital communication standard, which allows you to instantly transfer huge amounts of information with a high degree of protection of its content. In world telecommunications, there is a clear trend towards the development of full-service networks built on the basis of packet switching technology.

Currently, the top ten countries that have the most developed communication and telecommunications systems that meet world standards include Singapore, Sweden, New Zealand, Finland, Denmark, the USA, Hong Kong, Turkey, Norway and Canada. Kazakhstan in the ranking of countries in terms of the level of development of telecommunication systems is inferior not only to industrialized, but also to many developing countries.

The demand for information technology, modern computers and office equipment in recent years has a significant impact on the dynamics and structure of the world economy. A real revolution in the field of information technology was the emergence and rapid development of the cellular communication system, which by the beginning of the third millennium had become one of the leading sectors of the world economy.

cellular roaming

1. Algorithm for the functioning of cellular communication systems

Algorithms for the operation of cellular communication systems of various standards are basically similar. When the mobile station is in idle mode, its receiver constantly scans either all channels or only control channels (CC). To call a subscriber, all BSs transmit a call signal over control channels. The PS of the called subscriber upon receipt of this signal responds to one of the free KU. The BS that received the response signal transmits information about its parameters to the switching center (CC), which switches the conversation to the BS where the maximum signal level of the called subscriber's PS is recorded.

During dialing, the PS occupies one of the free channels, the BS signal level in which is currently maximum. As the subscriber moves away from the BS or due to the deterioration of signal propagation conditions, the subscriber automatically switches to another free channel or another BS. A special procedure called handover (Handover) allows you to seamlessly switch the conversation to a free channel of another BS, in the coverage area of ​​\u200b\u200bwhich the subscriber is. To control such situations, the BS is equipped with a special receiver that periodically measures the signal level from the PS and compares it with an acceptable threshold. (Some PS models also periodically measure the level of the received signal and evaluate its quality). If the signal level is less than the threshold, then information about this is automatically transmitted to the switching center via the service communication channel. The switching center issues a command to measure the signal from this subscriber to other BSs (several at once) surrounding the PS subscriber. After receiving a response from these BSs, the switching center selects the most suitable BS.

If all BS channels are busy servicing subscribers and at this time a service request is received from the next subscriber, then, as a temporary measure(before the release of one of the channels), it is possible to use the handover principle even within the same cell. This does not block the call, but alternately switches all the subscribers participating in the connection from channel to channel. In such a process, you can alternately give some time from all channels to a new subscriber. A "reserve" channel is formed, as it were.

One of the most important services of a cellular network is the provision of a set of services for a subscriber from the same mobile station (radio telephone) in other cities, regions and even other countries, the so-called roaming (Roaming). To implement such a service, there must be an agreement between operators of cellular networks for the provision of roaming to subscribers coming from areas served by other operators.

2. Initialization and communication

In the operation of the PS in the service area of ​​its “own” network, four modes can be distinguished that are essentially similar for systems of different standards:

· Standby mode;

communication (call) establishment mode;

communication mode (telephone conversation).

If the PS is completely turned off (de-energized), then after turning on the power to the PS, the process is automatically performed initialization - initial start. During this mode, the PS is configured to work as part of the system - according to signals regularly transmitted by base stations via control channels (CC). Upon completion of initialization, the PS goes into standby mode. The specific content of initialization operations depends on the standard of the cellular communication system.

In standby, PS tracks:

Changes in information from the system, associated both with changes in the operation of the system, and in connection with the movements of the PS itself;

system commands (for example, confirm the operability, measure the level of the received signal, etc.);

receiving a call from the system;

call initialization by own subscriber.

In addition, the MS can periodically, for example, once every 10-15 minutes, confirm its operability by transmitting appropriate signals to the BS or transmit other messages for the system, regardless of the communication session. In the switching center (SC), for each of the included PSs, a cell is fixed in which it is “registered”, which facilitates the organization of the procedure for calling a mobile subscriber. If the PS does not confirm its operability within a certain time, then the Central Committee considers it switched off and the call arriving at this PS is not transmitted. Therefore, the power of the MS is usually not turned off and the MS is in standby mode.

Procedure communication is as follows. If from the system side or from the PSTN network a call to the mobile subscriber's number arrives at the CC, then the CC directs this call to the BS of the cell in which the MS was registered, or to several BSs in the vicinity of this cell (taking into account the possible movement of the subscriber). The BSs transmit the call on the appropriate call channels. If the MS is in standby mode, then it receives the call and answers it through its BS, simultaneously transmitting data for the authentication procedure. If the authentication result is positive, a traffic channel is assigned to the MS through the BS and the number of the frequency channel is reported. The mobile station tunes in to a dedicated channel and, together with the BS, performs the necessary actions to prepare for a communication session. At this stage, the PS, using synchronization signals, is tuned to a given slot number in the frame, specifies the time delay, adjusts the level of radiated power, etc. The choice of time delay is made for the purpose of temporal coordination of slots in the frame (for reception in the BS) when organizing communication with mobile stations located at different distances from the BS. In this case, the time delay of the packet transmitted by the PS is regulated by the commands of the BS.

Then the BS issues a call (call) message, which is acknowledged by the mobile station, and the calling subscriber hears a ring tone. When the called subscriber answers the call ("picks up the phone"), the MS issues a request to the BS to terminate the connection. With the completion of the connection, the actual communication session (conversation) itself begins.

During the conversation, the PS processes the transmitted and received speech signals, as well as the control signals transmitted simultaneously with the speech. At the end of the conversation, service messages are exchanged between the MS and the BS (request or command to turn off with confirmation), after which the PS transmitter turns off and the station goes into standby mode (standby mode).

If the call is initiated by the MS, i.e. the subscriber of the PS dials the called number, checks the display for correct dialing and presses the appropriate call button on the PS panel, then the PS sends a message through its BS indicating the number of the called subscriber and data for station authentication. After successful authentication, the BS assigns a traffic channel. The subsequent steps to prepare a communication session are performed in the same way as when a call is received from the system.

If communication is established between two mobile subscribers, then the procedure for establishing communication is practically no different from establishing communication with subscribers of the PSTN network, since all connections are established through the mobile communication switch Central Committee (MSC). If both mobile subscribers belong to the same cellular system, then communication is established through the CC without access to the PSTN network switches.

3. Authentication and identification

Authentication and identification procedures are performed every time a connection is established. Authentication - the procedure for confirming the authenticity (validity, legality, availability of rights to use the services of a cellular network) of a subscriber. Identification is the procedure for identifying the mobile unit (i.e. mobile station). At the same time, the affiliation of the PS to one of the groups with certain characteristics is determined, and faulty and stolen devices are also identified.

The idea of ​​the authentication procedure in a digital system is to encrypt some identifier passwords using quasi-random numbers periodically transmitted to the PS from the Central Committee and an encryption algorithm individual for each PS. Such encryption using the same initial data and algorithms is performed both at the PS and at the Central Committee (or at the authentication center). Authentication is considered successful if both results match.

4. Handover (in routing)

The base station, located approximately in the center of the cell, serves all MS within its cell. When the MS moves from one cell to another, its service is accordingly transferred to another BS. The handover process occurs without interruption of communication, i.e. going on handover service. If the MS moves from one cell to another in the standby mode, it simply tracks these movements according to the system information transmitted over the control channels, and at the right time changes to a stronger signal from another BS.

The handover decision is made by the switching center. A handover command is sent from the switching center to the “new” BS in order for this BS to be able to allocate the necessary channels, and then the necessary commands are transmitted to the PS through the “old” BS indicating the new frequency channel, working slot number, etc. The PS is automatically reconfigured to a new channel and is configured to work together with the new BS. The rebuilding process takes a fraction of a second and remains invisible to the subscriber.

5. Roaming

Roaming- this is a function or procedure for providing services of a cellular communication system to a subscriber of one operator in the system of another operator (of course, in compatible standards). When a subscriber moves to another network and connects, the central switch of the new network requests (via special communication channels) information about the subscriber from the original network where the user is registered. If the subscriber has confirmation of authority, the new network registers it with itself. The location data of the subscriber is constantly updated in the original network and all incoming calls there are automatically forwarded to the network where the subscriber is currently located.

To organize roaming, the networks participating in such an agreement must be of compatible standards. The switching centers of all networks must be interconnected by special communication channels (wire lines, telephone lines, radio communication, etc.) for the exchange of service data.

There are three types of roaming: manual, semi-automatic and automatic. With manual roaming, there may not be service connections between the CC. It's just that when a subscriber moves to another network, he exchanges his radiotelephone for another one connected to the new system. With the semi-automatic option, the subscriber must first notify his operator of the transition to the service system of another network.

Much more complex operations have to be performed with automatic roaming. A cellular network subscriber who finds himself in the territory of another network initiates a call in the usual way, as in his own network. The CC of the new network, after making sure that this subscriber does not appear in its home register HLR, perceives it as a roamer and enters it into the guest register VLR. At the same time (or with some delay) it requests the HLR of the "native" system of the roamer for information related to it, necessary for organizing the service (specified types of services, passwords, ciphers), and also reports in which system the roamer is currently located. The new location is fixed in the HLR of the "native" system. After that, the roamer uses cellular communication in the new system as at home. Calls originating from it are handled in the usual way, with the only difference that the information related to it is not recorded in the HLR. And in VLR. Calls to a roamer's "home" network number are forwarded by the "home" network to the system where the roamer is visiting. When the roamer returns home, the address of the system where the roamer was located is erased in the HLR of the “native” system, and information about the roamer is erased in the VLR of that system.

In the GSM standard, the roaming procedure is laid down as a mandatory element. In addition, the GSM standard has the ability to roam with SIM cards with the rearrangement of these cards from one device to another to support various versions of the GSM standard (GSM-900, GSM-1800? GSM-1900), since all three versions of the standard use unified SIM cards. The roaming procedure in the GSM standard becomes even more convenient with the advent of dual-mode, and in the future, tri-mode subscriber terminals that provide operation in all GSM frequency bands.

6. GSM call service

When considering cellular telephone networks within the global network, it should be borne in mind that the subscriber is connected not just to a mobile communication switch, but directly to a network that can combine not only several cellular networks within one country, but also networks of many countries. In general, the following service areas of the global telephone network can be distinguished:

honeycomb (Cell);

location or search area (Location Area);

service area of ​​the central switchboard for mobile communications (MSC Service Area);

· service area of ​​a cellular telephone network (STS) of general use with several switching centers (PLMN Service Area);

· Global system service area (GSM service Area).

A cell is understood here as the service area of ​​this BS (BTS). A location or search area combines a number of cells controlled by one or more controllers (BSCs) but within the same mobile switch (MSC). At the same time, within the location zone, the subscriber can move freely without updating data in the guest register (VLR). In addition, within this service area, an address is transmitted to search for a specific MS.

The switching center service area (MSC) is part of the overall system. The subscriber is registered in the VLR of a particular CC and he can freely move within this service area without transferring his subscriber data to another VLR and updating the data in the HLR.

The service area of ​​public cellular communication systems is determined by the service areas of each switching center included in this system and through which access to other telecommunication networks, including other service areas of public cellular telephone networks, is provided.

The service area of ​​the global cellular telephone network includes all service areas of national cellular telephone networks. This means that all national cellular networks must be built in accordance with the GSM standard.

This approach to the functional organization of the global network by zones also determines the network numbering system. Taking into account that the GSM cellular telephone network can provide communication of the PS with fixed PSTN subscribers (ISDN in the future), and through it with subscribers of other telecommunication networks, it should be included in the general numbering plan of the fixed PSTN network in accordance with the recommendations of the CCITT E.164.

At the same time, the mobile station number in the general MSISDN numbering plan (Mobile Station ISDN Number) contains: country code, network code, subscriber number. For Russia, such a number will be presented in the form: 7ABSavxxxxxx. However, the GSM STS is a dedicated one and can unite the STS of different countries. Therefore, in accordance with the recommendations of the GSM standard, a single numbering has been adopted within the GSM network, and upon registration, a subscriber is assigned a single international IMSI number, the length of which should not exceed 15 digits. The structure of the IMSI number is similar to the structure of the MSISDN number, but 3 digits are allocated for the country code in the GSM network; under the network code 1-2 digits; subscriber number up to 11 digits. In addition, a problem arises when routing incoming calls to the CC from the PSTN network due to the fact that the MS, moving freely, can change service areas (and, for example, end up in the area of ​​another PBX with a different numbering). As a result, unlike fixed telephone networks, the directory number (MSIDN IMSI) cannot contain a logical direction code that uniquely identifies the MSC in whose service area the called MS is currently located. In order to provide routing capability, each MSC (VLR) has a set of MSRNs at its disposal, which are provided on demand to the parent MSC (if the system has multiple MSCs) only while the call is routed to a particular MSC. Given this, the MSRN number, unlike the MSISDN number, does not contain a subscriber number, but a number that identifies the MSC. In the MSC (VLR), the assigned MSRN is one-to-one with the IMSI of the called MS. To determine the search area (location) in the GSM network, the LAI number is used, which differs from the IMSI number in that here the location area code is indicated instead of the subscriber number.

Along with the considered numbers used in the call routing process, the GSM standard provides a number for equipment identification IMEI and a temporary subscriber number TMSI used to ensure confidentiality. The IMEI number includes codes for the type of equipment and manufacturer, serial number. The TMSI number is determined by the network administration and should be no longer than 4 bytes.

Subscriber authentication, mobile station equipment identification and information closure

To ensure authentication and information closure during registration, the subscriber is assigned not only an IMSI number, but also an individual subscriber key Ki, which is stored in the Authentication Center (AUC), as well as in the mobile station equipment. The subscriber key Ki in the authentication center is used to form a triplet: the information closing key Kc, the tagged response SRES, and the random number RAND (Fig. 1). First, a random number RAND is generated. RAND and Ki are the initial data for calculating Kc and SRES. In this case, two different calculation algorithms are used. The generated triplets for each of the subscribers registered in the GSM network are transferred to the HLR register, and, if necessary, are provided to the guest register of the switching center. The calculation algorithm for Kc and SRES is implemented not only in the authentication center, but also in the mobile station.

Rice. 1. Formation of Kc, SRES, RAND

In the GSM standard, the authentication procedure is associated with the use of a Subscriber Identity Module (SIM). The SIM module is a removable plastic card inserted into the slot of the subscriber unit. This card has an electronic chip in which all the necessary information is "sewn up". The SIM module allows you to carry on a conversation from any device of the same standard, including a payphone. The module contains a subscriber PIN, an IMSI identifier, a Ki key, an individual subscriber authentication algorithm A3, and an encryption key calculation algorithm A8. The unique IMSI for the current job is replaced by a temporary TMSI assigned to the machine when it first registers in a particular region, identified by the LAI, and reset when the machine leaves that region. The PIN identifier is a code known only to the subscriber, which should serve as protection against unauthorized use of the SIM card. For example, when it is lost. After three unsuccessful attempts to dial the PIN - code, the SIM card is blocked. The blocking can be removed either by dialing an additional code (known only to the subscriber) - a personal unblocking code (PUK), or by command from the switching center.

The authentication procedure is as follows. When the MS requests network access, the Authentication Center AUC, through the MSC (switching center), transmits a random number RAND to the MS. The mobile station, having received the RAND number and using the subscriber key Ki stored by it, uses the A3 algorithm to calculate the tagged response SRES. Having generated the SRES, the mobile station transmits it to the MSC, where the received SRES is compared with the SRES calculated by the network. If they match, the MS is allowed access to the network. The authentication procedure is carried out when registering the MS, attempting to establish a connection, updating data, as well as when activating and deactivating additional services. The authentication procedure is shown in fig. 2.

Rice. 2. Authentication principle

Identification of the user equipment itself begins with a request from the PS for the IMEI number. The switching center (MSC) transfers the received IMEI number to the EIR (Equipment Identity Register) equipment identification register, where there are three lists of PS equipment: allowed for use, prohibited for use in the communication system and faulty. Based on the list information, it is determined to which group the PS with the IMEI number belongs). The results are sent to the switching center, where a decision is made on the access of the user equipment to the network.

The closure of user information transmitted over the radio channel is carried out in the BS and in the PS. Both use the same encryption algorithms for transmitted messages. To close the user information, the access cycle number and the information closing key Kc are used. In the BS, the key Kc from the triplet is used, and in the PS it is calculated based on the received random number RAND and the subscriber key Ki according to the A8 algorithm.

Algorithm A8 is used for calculation to calculate the message encryption key and is stored in the SIM module. After receiving RAND, the mobile station calculates, in addition to the SRAS response, also the encryption key Kc using RAND, Ki and algorithm A8 according to Fig. 2. In addition to RAND, the network sends to the MS a numerical sequence of the encryption key. This number is related to the value of Kc and avoids the formation of an incorrect key. The value of Kc is stored in the MS and is contained in every first message sent to the network.

Rice. 3. Setting the encryption mode

To set the encryption mode, the network sends a CMC (Ciphering Mode Command) command to the PS to switch to the encryption mode, after which the PS, using the Kc key, proceeds to encrypt and decrypt messages. The data stream is encrypted bit by bit or with a stream cipher using the encryption algorithm A5 and the key Kc. The procedure for setting the encryption mode is shown in fig. 3.

Conclusion

In each country, the management of the telecommunications industry has its own specifics. However, the emergence of digital technologies and the massive introduction of Internet access services have led to the fact that today almost any telecom operator operates not only in the local (regional or national), but also in the global telecommunications services market.

The advent of digital technologies has contributed to radical changes in the telecommunications industry. Traditional voice communication services have begun to be replaced by interactive services such as the Internet, data transmission, and mobile communications.

But, despite the changes, the domestic communication services market remains quite closed. On the one hand, this is due to the vast scale of the country's territory, due to which the main income of telecom operators is formed. On the other hand, Kazakhstan is still outside the world market for international traffic, which has so far been the result of an insufficiently high level of digitalization of the main channels and a lower quality of communication compared to world standards. increase.

Despite the high rates of introduction of modern technologies, the percentage of coverage of the population of the Republic of Kazakhstan with new types of communication, such as cellular communication, paging, the Internet, remains low.

List of sources used

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M. Mouly, M. B. Pautet. The GSM System for Mobile Communications. 1992.p.p. 702.

A. Mehrotra. Cellular Radio: Analog and Digital Systems. Artech House, Boston-London. 1994.p.p.460.

4. Yu.A. Gromakov. The structure of TDMA frames and the formation of signals in the GSM standard. "Electrocommunication". N10.1993.p.9-12.

5. W. Heger. GSM vs. CDMA. GSM Global System for Mobile Communications. Proceedings of the GSM Promotion Seminar 1994 GSM MoU Group in Cooperation with ETSI GSM Members. December 15, 1994. p.p. 3.1-1 - 3.1-18.

Sukachev E.A. Cellular radio networks with mobile objects: Textbook. - Ed. 2nd, rev. and additional - Odessa: UGAS, 2000. - 119s

Yu.A. Gromakov. Cellular systems of mobile radio communication. Technologies of electronic communications. Volume 48. Eco-Trends. Moscow. 1994.

Today, mobile Internet has become familiar to cellular users. Such opportunities appeared due to its progress, which in chronological order can be represented as follows:

1984 - 1G - an analog standard that provides only voice communication at a data transfer rate of 1.9 kbps;
1991 - 2G - these are already digital standards, they provide a speed of 9.6 kbps, it is possible to exchange SMS messages (the most common are CDMA, GSM);
1999 - GPRS standard, intermediate, is a continuation of GSM, packet transmission of digital information is implemented, and allows you to use the Internet at a theoretical speed of more than 100 kbps, in reality - 2-3 times slower due to network congestion;
2003 - Advanced EDGE technology for GSM and TDMA networks up to 384 kbps;
2002 - 3G, represented by standards - UMTS, a continuation of GSM, and CDMA2000, thanks to speeds up to 2 Mbps, provides video communication and video viewing;
2008-2010 - the emergence of 4G technology, focused specifically on the transfer of mega-volumes of data at speeds up to 1 Git / s, its most common WiMAX and LTE standards today provide 100-300 Mbit / s for reception.

What technologies are used by Russian mobile operators

At present, 2G generation networks using EDGE and GPRS are the best developed in Russia. They provide almost complete coverage of the territory of the Russian Federation, and provide Internet access, the possibility of voice communication and SMS exchange. Of the largest providers operating in 2G, most use the GSM standard, and SKYLINK uses CDMA.

3G networks operate using WCDMA technology, providing a speed of about 10 Mbps, sufficient for video calls. This service is provided by many major operators, providing coverage in large cities.

The 4G network was the first to appear in Novosibirsk. Today 4G networks operate in 79 regions of the Russian Federation. This service is provided by operators Yota Freshtel, MTS, Beeline, MegaFon. LTE technology in Russia is used only for accessing the Internet, not for voice communications. In this case, you need a special SIM card and a new generation mobile device.

When choosing a smartphone, they take into account the standard of the operator whose service you use. Usually, 2G networks are cheaper for calls, but they are too slow for the Internet. Therefore, it is advantageous to use a smartphone that supports the required standards for 2 SIM cards: one for talking, the second for the Internet.