Modern satellite communication systems. Satellite communication systems of the world. How modern satellite communications equipment works

Project content:

Introduction

3.Satellite communication system

4.Application of satellite communication

5.VSAT technology

7. Mobile satellite communication systems

8. Disadvantages of satellite communication

9. Conclusion

Introduction

Modern realities already speak of the inevitability of replacing conventional mobile and, even more so, landline phones with satellite communications. Newest technologies satellite communications offer effective technically and economically viable solutions for the development of both universally accessible communication services and direct audio and TV broadcasting networks. Thanks to outstanding achievements in the field of microelectronics, satellite phones have become so compact and reliable in use that they are increasingly in demand among various groups of users, and the satellite rental service is one of the most popular services in the modern satellite communications market. Significant development prospects, obvious advantages over other telephony, reliability and guaranteed uninterrupted communication - all this is about satellite phones.

Satellite communications today are the only cost-effective solution for providing communication services to subscribers in areas with low population density, which is confirmed by a number of economic studies. Satellite is the only technically feasible and cost-effective solution if the population density is lower than 1.5 people/km2.Satellite communications have the most important advantages necessary for building large-scale telecommunications networks. Firstly, with its help you can quickly create a network infrastructure that covers a large area and does not depend on the presence or condition of terrestrial communication channels. Secondly, the use of modern technologies for accessing the resource of satellite repeaters and the ability to deliver information to an almost unlimited number of consumers simultaneously significantly reduce the cost of operating the network. These advantages of satellite communications make it very attractive and highly effective even in regions with well-developed terrestrial telecommunications. Preliminary forecasts for the development of personal satellite communication systems show that at the beginning of the 21st century the number of their subscribers amounted to approximately 1 million, and over the next decade - 3 million. Currently, the number of users of the Inmarsat satellite system is 40 thousand.

In recent years, modern types and means of communication have been increasingly being introduced in Russia. But, if a cellular radiotelephone has already become commonplace, a personal satellite communication device (satellite terminal) is still a rarity. An analysis of the development of such means of communication shows that in the near future we will witness the everyday use of personal satellite communication systems (PSCS). The time is approaching to combine terrestrial and satellite systems into a global communications system. Personal communication will become possible on a global scale, i.e. the subscriber’s reach anywhere in the world will be ensured by dialing him phone number, independent of the subscriber's location. But before this becomes a reality, satellite communication systems will have to successfully pass tests and confirm the stated technical characteristics and economic indicators during commercial operation. As for consumers, what to do right choice, they will have to learn to navigate a variety of sentences well.

Project goals:

1. Study the history of the satellite communication system.

2. Familiarize yourself withfeatures and prospects for the development and design of satellite communications.

3. Get information about modern satellite communications.

Project objectives:

1. Analyze the development of the satellite communication system at all its stages.

2. Get a complete understanding of modern satellite communications.

1.Development of satellite communication network

At the end of 1945, the world saw a small scientific article that was devoted to the theoretical possibilities of improving communications (primarily the distance between the receiver and transmitter) by raising the antenna to its maximum height. The use of artificial satellites as radio signal relays became possible thanks to the theory of the English scientist Arthur C. Clarke, who published a note entitled “Extraterrestrial Relays” in 1945. He actually foresaw a new round in the evolution of radio relay communications, proposing to bring repeaters to the maximum accessible height.

American scientists became interested in theoretical research and saw in the article a lot of advantages from the new type of communication:

no more need to build a chain of terrestrial repeaters;

one satellite is enough to provide a large coverage area;

the ability to transmit a radio signal to anywhere on the planet, regardless of the availability of telecommunications infrastructure.

As a result, practical research and the formation of a satellite communication network around the world began in the second half of the last century. As the number of repeaters in orbit grew, new technologies were introduced and satellite communications equipment was improved. Now this method information exchange has become available not only to large corporations and military companies, but also to individuals.

The development of satellite communication systems began with the launch of the first Echo-1 device (a passive repeater in the form of a metallized ball) into space in August 1960. Later, key satellite communication standards were developed (working frequency ranges), which are widely used throughout the world.

1.1 History of the development of satellite communications and main types of communications

The history of the development of the Satellite Communication System has five stages:

1957-1965 The preparatory period, which began in October 1957 after the Soviet Union launched the world's first artificial Earth satellite, and a month later the second. This happened at the height of the Cold War and a rapid arms race, so, naturally, satellite technology became primarily the property of the military. The stage under consideration is characterized by the launch of early experimental satellites, including communication satellites, which were mainly launched into low Earth orbits.

The first geostationary relay satellite, TKLSTAR, was created for the US Army and launched into orbit in July 1962. During the same period of time, a series of American military communications satellites SYN-COM (Synchronous Communications Satellite) was developed.

1965-1973 The period of development of global network systems based on geostationary repeaters. The year 1965 was marked by the launch in April of the geostationary SR INTELSAT-1, which marked the beginning of the commercial use of satellite communications. The early INTELSAT series satellites provided transcontinental communications and primarily supported backhaul links between a small number of national gateway earth stations that interfaced with national public terrestrial networks.

The trunk channels provided connections through which telephone traffic, TV signals were transmitted and telex communications were provided. In general, the Intelsat SSS complemented and backed up the submarine transcontinental cable communication lines that existed at that time

1973-1982 The stage of widespread dissemination of regional and national SSS. At this stage in the historical development of the SSS, the international organization Inmarsat was created, which deployed the Inmarsat global communications network, the main purpose of which was to provide communications with ships at sea. Subsequently, Inmarsat extended its services to all types of mobile users.

1982-1990 A period of rapid development and proliferation of small earth terminals. In the 80s, advances in the field of technology and technology of key elements of the SSS, as well as reforms to liberalize and demonopolize the communications industry in a number of countries, made it possible to use satellite channels in corporate business communication networks, called VSAT.

VSAT networks made it possible to install compact earth stations for satellite communications in close proximity to user offices, thereby solving the “last mile” problem for a huge number of corporate users, created conditions for comfortable and rapid exchange of information, and made it possible to relieve the burden on public terrestrial networks. The use of “intelligent” satellites communications.

Since the first half of the 90s, the SSS entered a quantitatively and qualitatively new stage of its development.

A large number of global and regional satellite communications networks were in operation, production or design. Satellite communications technology has become an area of ​​significant interest and business activity. This period of time saw explosive growth in the speed of general-purpose microprocessors and the volume of semiconductor storage devices, while simultaneously increasing reliability, as well as reducing power consumption and the cost of these components.

Main types of communication

Given the wide scope of application, I will highlight the most common types of communications that are currently used in our country and around the world:

radio relay;

high frequency;

postal;

GSM;

satellite;

optical;

control room

Each type has its own technology and a set of necessary equipment for full operation. Let me consider these categories in more detail.

Communication via satellite

The history of satellite communications begins at the end of 1945, when English scientists developed the theory of transmitting a radio relay signal through repeaters that will be located at high altitude (geostationary orbit). The first artificial satellites began to be launched in 1957.

The advantages of this type of communication are obvious:

minimum number of repeaters (in practice, one or two satellites are enough to ensure high-quality communication);

improvement of basic signal characteristics (no interference, increased transmission distance, improved quality);

increasing the coverage area.

Today, satellite communications equipment is a complex complex that consists not only of orbital repeaters, but also base ground stations that are located in different parts of the planet.

2. Current state of the satellite communication network

Of all the numerous commercial MSS (mobile satellite communications) projects in the sub-1 GHz range, one Orbcomm system has been implemented, which includes 30 non-geostationary (non-GSO) satellites providing Earth coverage.

Due to the use of relatively low frequency ranges, the system allows the provision of low-speed data transmission services, such as Email, two-way paging, services remote control. The main users of Orbcomm are transport companies, for which this system provides economical effective solution to monitor and manage the transportation of goods.

The most famous operator in the MSS services market is Inmarsat. The market offers about 30 types of subscriber devices, both portable and mobile: for land, sea and air use, providing voice, fax and data transmission at speeds from 600 bps to 64 kbps. Inmarsat faces competition from three MSS systems, namely Globalstar, Iridium and Thuraya.

The first two provide almost complete coverage of the earth's surface through the use of large constellations, respectively consisting of 40 and 79 non-GSO satellites. Pre Thuraya went global in 2007 with the launch of the third geostationary (GS O) satellite, which will cover the American continent, where it is currently unavailable. All three systems provide services telephone communication and low-speed data transmission to receiving devices comparable in weight and size to GSM mobile phones.

The development of satellite communication systems plays a significant role in the formation of a unified information space on the territory of the state and is closely related to federal programs to eliminate the digital divide and develop nationwide infrastructure and social projects. The most significant Federal target programs on the territory of the Russian Federation are the projects on “Development of television and radio broadcasting” and “Elimination of digital inequality”. The main objectives of the projects are the development of digital terrestrial television, communication networks, mass broadband access systems to global information networks and the provision of multiservice services on mobile and mobile objects. Besides federal projects, the development of satellite communication systems provides new opportunities for solving the problems of the corporate market. The areas of application of satellite technologies and various satellite communication systems are rapidly expanding every year.

One of the key factors in the successful development of satellite technologies in Russia is the implementation of the Program for the Development of an orbital constellation of communications and broadcasting satellites for civil purposes, including satellites in highly elliptical orbits.

Development of satellite communication systems

The main drivers of development of the satellite communications industry in Russia today are:

launch of networks in the Ka-band (on the Russian satellites "EXPRES-AM5", "EXPRES-AM6"),

active development of the mobile and mobile communications segment on various transport platforms,

entry of satellite operators into the mass market,

development of solutions for organizing backbone channels for cellular networks in the Ka-band and M2M applications.

The general trend in the global satellite services market is the rapid increase in data transmission speeds provided on satellite resources, satisfying the basic requirements of modern multimedia applications and responding to the development of software and the growth in the volume of transmitted data in the corporate and private segments.
In satellite communication networks operating in the Ka-band, the greatest interest is associated with the development of services for the private and corporate segment in the context of reducing the cost of satellite capacity implemented on Ka-band satellites with high throughput (High-Throughput Satellite - HTS).

Use of satellite communication systems

Satellite communications systems are designed to meet the needs of communications and satellite Internet access anywhere in the world. They are needed where increased reliability and fault tolerance are required; they are used for high-speed data transmission when organizing multi-channel telephone communications.

Specialized communication systems have a number of advantages, but the key is the ability to implement high-quality telephony outside the coverage areas of cellular stations.

Such communication systems allow you to operate on autonomous power for a long time and be in call waiting mode, this is due to the low energy indicators of the user equipment, light weight and omnidirectional antenna.

Currently, there are many different satellite communication systems. Everyone has their pros and cons. Additionally, each manufacturer offers users an individual set of services (Internet, fax, telex), determines a set of functions for each coverage area, and also calculates the cost of satellite equipment and communication services. In Russia the key ones are:Inmarsat, Iridium and Thuraya.

Areas of use of SSS (Satellite Communication Systems): navigation, ministries and departments, government agencies and institutions, the Ministry of Emergency Situations and rescue units.

The world's first mobile satellite communications system offering full set modern services to users around the world:, and in the cart spirit.

The Inmarsat satellite communication system has a number of advantages:

coverage area – the entire territory of the globe, except for the polar regions

quality of services provided

confidentiality

additional accessories (car kits, faxes, etc.)

free incoming calls

accessibility in use

online system for checking account status (billing)

high level of trust among users, time-tested (over 25 years of existence and 210 thousand users worldwide)

Main services of the Inmarsat satellite communication system:

Telephone

Fax

Email

Data transmission (including high-speed)

Telex (for some standards)

GPS

The world's first global satellite communications system that operates anywhere in the world, including the South and North Poles. The manufacturer offers a universal service available for business and life at any time of the day.

The Iridium satellite communication system has a number of advantages:

coverage area – the entire territory of the globe

low tariff plans

free incoming calls

Basic services of the Iridium satellite communication system (Iridium) :

Telephone

Data transfer

Paging

A satellite operator that provides service on 35% of the globe. Services implemented in this system: satellite and GSM handsets, as well as satellite payphones. Inexpensive mobile connection for freedom of communication and movement.

The Thuraya satellite communication system has a number of advantages:

compact size

ability to switch between satellite and cellular communication automatically

low cost of services and telephones

free incoming calls

Main services of the Thuraya satellite communication system:

Telephone

Email

Data transfer

GPS

3.Satellite communication system

3. 1. Satellite repeaters

For the first time, years of research, passive satellite repeaters were used (examples are the Echo and Echo-2 satellites), which were a simple radio signal reflector (often a metal or polymer sphere with a metal coating) that did not carry any transceiver equipment on board. Such satellites have not become widespread.

3.2 Orbits of satellite relays

The orbits in which satellite relays are located are divided into three classes:

·equatorial

· inclined

polar

An important variation of the equatorial orbit is the geostationary orbit, in which the satellite rotates with an angular velocity equal to the angular velocity of the Earth, in a direction coinciding with the direction of rotation of the Earth

An inclined orbit solves these problems, however, due to the movement of the satellite relative to an observer on the ground, it is necessary to launch at least three satellites into one orbit to provide 24/7 access to communications.

Polar - an orbit with an inclination of the orbit to the equatorial plane of ninety degrees.

4.VSAT system

Among satellite technologies, the development of satellite communication technologies such as VSAT (Very Small Aperture Terminal) attracts special attention.

Based on VSAT equipment, it is possible to build multiservice networks that provide almost all modern communication services: Internet access; telephone communication; Union local networks(building VPN networks); transmission of audio and video information; reservation of existing communication channels; data collection, monitoring and remote control of industrial facilities and much more.

A little history. The development of VSAT networks begins with the launch of the first communications satellite. In the late 60s, during experiments with the ATS-1 satellite, an experimental network was created consisting of 25 earth stations, satellite telephone communications in Alaska. Linkabit, one of the first to create Ku-band VSAT, merged with M/A-COM, which subsequently became a leading supplier of VSAT equipment. Hughes Communications acquired the division from M/A-COM, transforming it into Hughes Network Systems. Currently, Hughes Network Systems is the world's leading supplier of broadband satellite communications networks. A VSAT-based satellite communication network includes three key elements: a central control station (CCS), a relay satellite and VSAT user terminals.

4.1.Relay satellite

VSAT networks are built on the basis of geostationary relay satellites. The most important characteristics of a satellite are the power of onboard transmitters and the number of radio frequency channels (trunks or transponders) on it. The standard trunk has a bandwidth of 36 MHz, which corresponds to a maximum throughput of about 40 Mbit/s. On average, transmitter power ranges from 20 to 100 watts. In Russia, examples of relay satellites include the Yamal communications and broadcasting satellites. They are intended for the development of the space segment of OJSC Gazcom and were installed in orbital positions of 49° East. d. and 90° east. d.

4.2 VSAT subscriber terminals

A VSAT subscriber terminal is a small satellite communication station with an antenna with a diameter of 0.9 to 2.4 m, designed primarily for reliable data exchange via satellite channels. The station consists of an antenna-feeder device, an external external radio frequency unit and an internal unit (satellite modem). The external unit is a small transceiver or only a receiver. The internal unit ensures the connection of the satellite channel with the user’s terminal equipment (computer, LAN server, telephone, fax, etc.).

5. VSAT technology

There are two main types of access to a satellite channel: two-way (duplex) and one-way (simplex, asymmetric or combined).

When organizing one-way access along with satellite equipment A terrestrial communication channel (telephone line, optical fiber, cellular networks, radio Internet) is required, which is used as a request channel (also called a return channel).

One-way access scheme using a DVB card and a telephone line as a return channel.

Two-way access diagram using HughesNet equipment (Hughes Network Systems).

Today in Russia there are several significant VSAT network operators that service about 80,000 VSAT stations. 33% of such terminals are located in the Central Federal District, 13% each in the Siberian and Ural Federal Districts, 11% in the Far Eastern and 5-8% each in the remaining federal districts. Among the largest operators we should highlight:

6.Global satellite communication system Globalstar

In Russia, the operator of the Globalstar satellite communication system is the closed joint-stock company GlobalTel. As the exclusive provider of global mobile satellite communication services of the Globalstar system, GlobalTel CJSC provides communication services throughout the entire Russian Federation. Thanks to the creation of the company CJSC GlobalTel, residents of Russia have another opportunity to communicate via satellite from anywhere in Russia with almost anywhere in the world.

The Globalstar system provides high-quality satellite communications to its subscribers using 48 operational and 8 spare low-orbit satellites located at an altitude of 1410 km. (876 miles) from the surface of the Earth. The system provides global coverage of almost the entire surface of the globe between 700 North and South latitudes with an extension to 740. The satellites are capable of receiving signals from up to 80% of the Earth's surface, i.e. from almost anywhere on the globe with the exception of the polar regions and some areas of the central oceans . The system's satellites are simple and reliable.

6.1. Areas of application of the Globalstar system

The Globalstar system is designed to provide high-quality satellite services to a wide range of users, including: voice, short message service, roaming, positioning, fax, data, mobile Internet.

Subscribers using portable and mobile devices can be business and private individuals working in areas that are not covered by cellular networks, or whose specific work involves frequent business trips to places where there is no connection or poor quality of communication.

The system is designed for a wide range of consumers: representatives of the media, geologists, workers in the production and processing of oil and gas, precious metals, civil engineers, and energy workers. Employees of Russian government agencies - ministries and departments (for example, the Ministry of Emergency Situations) can actively use satellite communications in their activities. Special kits for installation on vehicles can be effective when used on commercial vehicles, on fishing and other types of sea and river vessels, on railway transport, etc.

7.1. Mobile satellite communication systems

A feature of most mobile satellite communication systems is the small size of the terminal antenna, which makes signal reception difficult. To ensure that the signal power reaching the receiver is sufficient, one of two solutions is used:

· Satellites are located in geostationary orbit. Since this orbit is 35,786 km away from the Earth, a powerful transmitter must be installed on the satellite. This approach is used by Inmarsat (whose main mission is to provide communications services to ships) and some regional personal satellite communications operators (for example, Thuraya).

7.1. Satellite Internet

Satellite Internet is a method of providing access to the Internet using satellite communication technologies (usually in the DVB-S or DVB-S2 standard).

Access options

There are two ways to exchange data via satellite:

• one-way, sometimes also called “asymmetric” - when a satellite channel is used to receive data, and available terrestrial channels are used for transmission

  two-way (two-way), sometimes also called “symmetrical” - when satellite channels are used for both reception and transmission;

One-way satellite Internet

One-way satellite Internet implies that the user has some kind of existing method Internet connection. As a rule, this is a slow and/or expensive channel (GPRS/EDGE, ADSL connection where Internet access services are poorly developed and limited in speed, etc.). Only requests to the Internet are transmitted through this channel.

Two-way satellite Internet

Two-way satellite Internet involves receiving data from a satellite and sending it back also via satellite. This method is of very high quality, as it allows you to achieve high speeds when transmitting and sending, but it is quite expensive and requires obtaining permission for radio transmitting equipment (however, the latter is often taken care of by the provider). The high cost of two-way Internet turns out to be completely justified due to, first of all, a much more reliable connection. Unlike one-way access, two-way satellite Internet does not require any additional resources (except for power, of course).

A feature of “two-way” satellite Internet access is a fairly large delay on the communication channel. Until the signal reaches the subscriber to the satellite and from the satellite to the Central Satellite Communications Station, it will take about 250 ms. The same amount is needed for the return trip. Plus the inevitable delays for the signal to be processed and to pass through the Internet. As a result, the ping time on a two-way satellite channel is about 600 ms or more. This imposes some specifics on the operation of applications via satellite Internet and is especially sad for avid gamers.

Another feature is that equipment from different manufacturers is practically incompatible with each other. That is, if you have selected one operator that works on a certain type of equipment (for example, ViaSat, Hughes, Gilat EMS, Shiron, etc.), then you can only switch to an operator that uses the same equipment. An attempt to implement compatibility of equipment from different manufacturers (the DVB-RCS standard) was supported by a very small number of companies, and today it is more of another “private” technology than a generally accepted standard.

Equipment for one-way satellite Internet

8. Disadvantages of satellite communications

Weak noise immunity

The vast distances between earth stations and the satellite cause the signal-to-noise ratio at the receiver to be very low (much less than for most microwave links). In order to ensure an acceptable error probability under these conditions, it is necessary to use large antennas, low-noise elements and complex noise-resistant codes. This problem is especially acute in mobile communication systems, since they have restrictions on the size of the antenna and, as a rule, on the power of the transmitter.

Influence of the atmosphere

The quality of satellite communications is strongly influenced by effects in the troposphere and ionosphere.

Absorption in the troposphere

The absorption of a signal by the atmosphere depends on its frequency. The absorption maxima occur at 22.3 GHz (water vapor resonance) and 60 GHz (oxygen resonance). In general, absorption has a significant impact on the propagation of signals with frequencies above 10 GHz (that is, starting from the Ku-band). In addition to absorption, when radio waves propagate in the atmosphere, there is a fading effect, which is caused by the difference in the refractive indices of different layers of the atmosphere.

Ionospheric effects

Signal propagation delay

The problem of signal propagation delay, one way or another, affects all satellite communication systems. The greatest delay is experienced by systems that use a satellite repeater in geostationary orbit. In this case, the delay due to the finite speed of radio wave propagation is approximately 250 ms, and taking into account multiplexing, switching and signal processing delays, the total delay can be up to 400 ms. Propagation delay is most undesirable in real-time applications such as telephony. Moreover, if the signal propagation time over the satellite communication channel is 250 ms, the time difference between the subscribers’ replicas cannot be less than 500 ms. In some systems (for example, VSAT systems using a star topology), the signal is transmitted twice through the satellite link (from a terminal to a central node, and from a central node to another terminal). In this case, the total delay doubles.

9. Conclusion

Already at the very early stages of creating satellite systems, the complexity of the work ahead became obvious. It was necessary to find material resources, make the intellectual efforts of many teams of scientists, organize work at the stage practical implementation. But, despite this, transnational companies with free capital were actively involved in solving the problem. Moreover, not one, but several parallel projects are currently being implemented. Development companies are fiercely competing for future consumers and for global leadership in the field of telecommunications.

Currently, satellite communication stations are combined into data transmission networks. Integrating a group of geographically distributed stations into a network makes it possible to provide users with a wide range of services and capabilities, as well as to effectively use satellite resources. Such networks usually have one or more control stations that provide operation of the earth stations in both manual and fully automatic modes.

The advantage of satellite communications is based on serving geographically distant users without the additional costs of intermediate storage and switching.

SSNs are constantly and jealously compared to fiber optic communication networks. The adoption of these networks is accelerating due to rapid technological developments in the related areas of fiber optics, raising questions about the fate of SSNs. For example, development and planning, most importantly, the introduction of concatenating (composite) coding sharply reduces the likelihood of an uncorrected bit error, which, in turn, makes it possible to overcome main problem SSS - fog and rain.

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Communications satellites launched into space, as a rule, enter geostationary orbits, that is, they fly at the speed of rotation of the Earth and find themselves in a constant position relative to the surface of the planet. Orbiting 22,300 miles above the equator, one such satellite can receive radio signals from one-third of the planet.

The original satellites, such as Echo, launched into orbit in 1960, simply reflected radio signals aimed at them. Improved models not only receive signals, but also amplify them and transmit them to specified points on the earth's surface. Since the launch of the first commercial communications satellite, INTELSAT, in 1965, these devices have become much more sophisticated. The latest model of a satellite operating on solar energy, operates with 30,000 phone calls or serves four television programs simultaneously. The signals arrive from the antennas of the Earth-LA communication station and are received by the satellite transponder. This electronic device amplifies the signal and switches it to an antenna, which transmits it to the nearest LA-Earth communications station. To avoid interference, upstream and downstream signals are transmitted at different frequencies.

Launched into geostationary orbits, three INTELSAT satellites (left) transmit long-wave radio signals around the world. Serving the regions of the Pacific, Indian and Atlantic oceans, satellites make high-speed telephone, television and telegraph communications possible. High-frequency radio signals suffer in this regard because they are repelled by the charged particles that make up the E and F layers of the atmosphere.

This parabolic antenna can receive even very weak signals from a satellite; most similar systems can also serve for Earth-to-aircraft communications.

INTELSAT-6

Radio signals arriving at the satellite gradually weaken over the long journey to such a level that they can hardly be transmitted back to Earth. Satellites like INTELSAT, the model of which is shown above, amplify incoming signals using solar energy. Each satellite also has a supply of solid fuel, allowing it to maintain its orbit.

In the picture at the top of the article:

1. solar battery power supply element
2. parabolic reflectors
3. parabolic reflectors
4. parabolic reflectors
5. parabolic reflectors

Like terrestrial antennas, this satellite antenna consists of a tooth-shaped device called the primary emitter and a reflective parabolic shield. Two elements of this system ensure the acceptance of incoming radio waves and the destruction of foreign waves.

Stations located on the surface of the planet communicate with INTELSAT through huge, 30-foot-wide parabolic antennas like the one shown in Fig. above.

Space or satellite communication is essentially a type of radio relay (tropospheric) communication and is distinguished by the fact that its repeaters are not on the surface of the Earth, but on satellites in outer space.

The idea of ​​satellite communications was first introduced in 1945 by Englishman Arthur Clarke. He published an article in a radio engineering journal about the prospects of rockets like the V-2 for launching Earth satellites for scientific and practical purposes. The last paragraph of this article is significant: “An artificial satellite at a certain distance from the Earth will make one revolution in 24 hours. It will remain motionless over a certain place and within optical visibility from almost half of the earth’s surface. Three repeaters placed in a properly chosen orbit with an angular separation of 120° will be able to cover the entire planet with television and VHF radio broadcasting; I am afraid that those who plan post-war work will not consider this matter simple, but I consider this path to be the final solution to the problem.”

On October 4, 1957, the USSR launched the world's first artificial Earth satellite, the first space object whose signals were received on Earth. This satellite marked the beginning of the space age. The signals emitted by the satellite were used not only for direction finding, but also to transmit information about processes on the satellite (temperature, pressure, etc.). This information was transmitted by changing the duration of the messages emitted by the transmitters (pulse width modulation). On April 12, 1961, in the Soviet Union, for the first time in the history of mankind, a human flight into outer space was carried out. The Vostok spacecraft with pilot-cosmonaut Yu. A. Gagarin on board was launched into Earth satellite orbit. To measure the orbital parameters of the satellite ship and monitor the operation of its onboard equipment, numerous measuring and radio telemetry equipment was installed on it. To find the direction of the ship and transmit telemetric information, the Signal radio system was used, operating at a frequency of 19.955 MHz. Two-way communication between the astronaut and the Earth was provided by a radiotelephone system operating in the short (19.019 and 20.006 MHz) and ultrashort (143.625 MHz) wavelength ranges. The television system transmitted images of the astronaut to Earth, which made it possible to have visual control over his condition. One of the television cameras transmitted the image of the pilot from the front, and the other - from the side.

The achievements of Russian science in the field of space exploration have made it possible to realize the predictions of Arthur C. Clarke. At the end of the 50s of the last century, experimental studies began to be carried out in the USSR and the USA on the possibilities of using artificial Earth satellites as radio repeaters (active and passive) in terrestrial communication systems. Theoretical developments in the field of energy capabilities of satellite communication lines made it possible to formulate tactical and technical requirements for satellite repeater devices and ground-based devices, based on the actual characteristics of the technical means that existed at that time.

Considering the identity of the approaches, we will present experimental research in the field of creating satellite communication lines using the example of the United States. The first active radio repeater "Score" was launched on December 18, 1958 into an inclined elliptical orbit with an apogee height of 1481 km and a perigee height of 177 km. The satellite's equipment consisted of two transceivers operating at frequencies 132.435 and 132.095 MHz. The work was carried out in slow relay mode. The signal sent by the ground transmitting station was stored by recording onto magnetic tape. Silver-zinc batteries with a capacity of 45 amperes per hour at a voltage of 18 volts were used as power sources. The communication duration was approximately 4 minutes per satellite revolution. Retransmission of 1 telephone or 7 teletype channels was carried out. The service life of the satellite was 34 days. The satellite burned up upon re-entry on January 21, 1959. The second active radio repeater "Courier" was launched on October 4, 1960 into an inclined elliptical orbit with an apogee altitude of 1270 km and a perigee altitude of 970 km. The satellite's equipment consisted of 4 transceivers (frequency 150 MHz for transmitting commands and 1900 MHz for communication), a magnetic memory device and power sources - solar cells and chemical batteries. Silicon solar cells in the amount of 19,152 pieces were used as the primary power source. Nickel-cadmium batteries with a capacity of 10 amperes per hour at a voltage of 28-32 volts were used as a buffer cascade. The duration of the communication session was 5 minutes per satellite revolution. The service life of the satellite was 1 year. On July 10, 1962, the Telstar active repeater was launched into an inclined elliptical orbit with an apogee of 5600 km and a perigee of 950 km, which was intended for the active relay of radio signals in real time. At the same time, it relayed either 600 simplex telephone channels, or 12 duplex telephone channels, or one television channel. In all cases, the work was carried out using the frequency modulation method. Communication frequencies: on the satellite-Earth line 4169.72 MHz, on the Earth-satellite line 6389.58 MHz. The duration of a communication session on the US-Europe line via this satellite was about 2 hours a day. The quality of transmitted television images varied from good to excellent. The project provided for a very significant service life of the satellite - 2 years, but after four months of successful operation the command line failed. It was determined that the cause of the failure was surface damage due to radiation as the satellite passed through the inner radiation belt.

On February 14, 1963, the first synchronous satellite of the Sincom system was launched with orbital parameters: apogee altitude 37,022 km, perigee altitude 34,185, orbital period 1426.6 minutes. The operating frequency on the Earth-satellite line is 7360 MHz, on the satellite-Earth line 1820 MHz. The primary power source on the satellite was 3,840 solar cells with a total power of 28 W at a voltage of 27.5 volts. Communication with the satellite was maintained for only 20,077 seconds, after which observations were carried out using astronomical methods.

On April 23, 1965, the first communications satellite, Molniya-1, was launched in the USSR. With the launch of the second communications satellite “Molniya-2” on October 14, 1965, regular operation of a long-distance communication line through satellites began. Later, the Orbita long-distance space communication system was created. It consisted of a network of ground stations and artificial Earth satellites “Molniya”, “Rainbow”, “Horizon”. Below, in Chapter 7, it will be shown that modifications of the Horizon satellites continue to function in the 21st century. This indicates the high reliability of domestic equipment compared to foreign ones.

The first satellite communication stations were built, tested and put into operation in the town of Shchelkovo near Moscow and in Ussuriysk. They were connected by cable and relay communication lines, respectively, to television centers and long-distance telephone exchanges in Moscow and Vladivostok.

The most suitable equipment for equipping earth stations of the satellite system was the TR-60/120 tropospheric communication equipment, which, as is known, used high-power transmitters and highly sensitive receiving devices with low-noise parametric amplifiers. On its basis, the Gorizont receiving and transmitting complex is being developed, installed at ground stations of the first satellite communication line between Moscow and Vladivostok.

Transmitters were specially developed for the communication and command-measuring lines, parametric amplifiers with a noise temperature of 120 K for installation in the antenna's submirror cabin, as well as completely new equipment that ensures docking with local television centers and long-distance telephone exchanges.

In those years, earth station designers, fearing the influence of powerful transmitters on receivers, installed them on different antennas and in different buildings (receiving and transmitting). However, the experience of using one common antenna for reception and transmission, gained on tropospheric communication lines, made it possible to subsequently transfer the receiving equipment to the transmitting antenna, which significantly simplified and reduced the cost of operating satellite communication stations.

In 1967, an extensive television network of receiving earth stations “Orbit” with a central transmitting station near Moscow was created through the Molniya-1 communications satellite. This made it possible to organize the first communication channels between Moscow and the Far East, Siberia, and Central Asia, to transmit the Central Television program to remote areas of our Motherland and additionally reach more than 30 million television viewers.

However, the Molniya satellites orbited the Earth in elongated elliptical orbits. To track them, the antennas of ground receiving stations must constantly rotate. This problem is solved much more easily by satellites rotating in a stationary circular orbit, which is located in the equatorial plane at an altitude of 36,000 km. They make one revolution around the Earth in 24 hours and therefore appear to a ground observer to be hanging motionless over one point on our planet. Three such satellites are enough to provide communications to the entire Earth.

In the 80s of the last century, the Raduga communication satellites and the Ekran television satellites operating in stationary orbits operated effectively. Complex ground stations were not needed to receive their signals. Television broadcasts from such satellites are received directly on simple collective and even individual antennas.

In the 1980s, the development of personal satellite communications began. In this connection, the satellite phone is directly connected to a satellite in low Earth orbit. From the satellite, the signal arrives at a ground station, from where it is transmitted to the regular telephone network. The number of satellites required for stable communication anywhere on the planet depends on the orbital radius of a particular satellite system.

The main disadvantage of personal satellite communications is its relative high cost compared to cellular communications. In addition, high power transmitters are built into satellite phones. Therefore, they are considered unsafe for the health of users.

The most reliable satellite phones operate on the Inmarsat network, created more than 20 years ago. Inmarsat satellite phones come in the form of a flip-top case the size of early laptop computers. The lid of the satellite phone doubles as an antenna, which must be rotated towards the satellite (the signal level is displayed on the phone display). These phones are mainly used on ships, trains or heavy vehicles. Every time you need to make or answer someone's call, you will need to place the satellite phone on some flat surface, open the lid and twist it, determining the direction of the maximum signal.

Currently, in the overall communication balance, satellite systems still account for approximately 3% of global traffic. But the need for satellite links continues to grow, since with a range of over 800 km, satellite links become more cost-effective compared to other types of long-distance communications.

Modern satellite communications is one of the areas of development of radio relay communications. In this case, this is the use of orbiting satellites as relays.

Satellite communication technologies allow the use of one or more repeaters to ensure high-quality transmission of radio signals over long distances.

All repeaters can be divided into two categories:

• passive. Currently practically not used. Initially they were used exclusively as a transmission link between the ground station and the subscriber, they did not amplify the signal and did not convert it;


• active. Such devices additionally amplify the signal and correct it in every possible way before sending it to the subscriber. Most of the world's satellite systems use this type of repeater.

History of satellite communications

At the end of 1945, the world saw a small scientific article that was devoted to the theoretical possibilities of improving communications (primarily the distance between the receiver and transmitter) by raising the antenna to its maximum height.

What operating principle did you have in mind?

Everything is quite simple - the scientist proposed placing a large repeater antenna in low-Earth orbit, which would receive signals from a ground-based source and transmit it further.

The main advantage was the huge coverage area, which could be controlled by just one satellite. This would significantly improve the quality of the signal, remove the limit on the number of receiving stations, and additionally would not have to build terrestrial repeaters. The United States became interested in the project as part of solving problems with transatlantic telephone communications.

The development of satellite communication systems began with the launch of the first Echo-1 device (a passive repeater in the form of a metallized ball) into space in August 1960.

Later, key satellite communications standards (operating frequency bands) were developed and are widely used throughout the world.

Applications of satellite communications

Since its successful implementation, the quality of satellite communications has increased significantly.

Thanks to the introduction of mobile ground stations, the subscriber could receive a radio signal regardless of the location of the satellite at any time of the day, automatically moving from one coverage area to another, connecting to the nearest repeater in automatic mode.

The use of satellite communications can be divided into several conventional areas:

• trunk connection. Initially, the task was to transfer a large amount of information (in particular, voice messages), but over time, with the transition to a digital format, such a need disappeared and today satellite communications are being replaced from this area by fiber-optic networks;


• VSAT. So-called “small” systems with an antenna diameter of up to 2.4 meters. The technology is successfully developing and serves to create private communication channels;


• mobile communications (the basis of telephony and television broadcasting);


• Internet access.

To obtain more information about the development of this area of ​​communication, just attend a specialized event. The international exhibition “Communication”, which takes place on the territory of the Expocentre Fairgrounds, is the best industry event at the international level. This guarantees a wide exposure and participation of well-known global and domestic specialized companies.

How modern satellite communications equipment works

Satellite communications are strongly associated in the minds of many people with GPRS navigators and telephony. In fact, this is an invention of mankind and finds its niche in these areas from the point of view of ordinary people.

The concept of satellite communications itself originated in 1945, but at that time few people believed that such a data transmission channel could be implemented in life. However, the Earth is now surrounded by many satellites, providing continuous exchange of information between hundreds of people and devices.

It is thanks to the fact that modern satellite communications have such wide coverage that the ability to make calls from the most remote corners of the world has become real. No serious tourist would dare undertake a long and dangerous journey without a satellite phone.

There is also the concept of satellite Internet - it makes it possible to access the World Wide Web even where there is light only thanks to generators.

Using the resources and capabilities of satellite information transmission, many navigator options have been created for a wide variety of industries.

In fact, modern satellite communications consists of only three elements: a transmitter, a repeater and a receiver. The roles of transmitter and receiver are various devices: mobile phones, computers, antennas and so on.

A repeater is presented in the form of a satellite that receives an incoming signal from an earth station (or device) and transmits it in broadcast mode to the entire visible area. Further, the technical and software, which takes care that this information got right to the addressee. The exception is when all receivers must receive the signal. For example, satellite television.

For greater repeater throughput, the following multiple access (MA) systems were introduced:

1. Frequency division MD. Each user receives his own frequency.


2. Time division MD. The user has the right to receive or transmit data only within a certain period of time.


3. Code division MD. Each user is given a code. It is superimposed on the data so that signals from different users are not mixed, even when transmitted on the same frequency.

Overall, all of the above systems guarantee frequency reuse, which increases efficiency and capacity.

When transmitting information, the absorption of waves in the atmosphere and the size of the receiving antenna are also taken into account - for each specific case, its own frequency is used.

International satellite communications

International satellite communications is a type of radio relay communication that is based on the use of artificial earth satellites as repeaters. Communication occurs between stations located on the ground, which in turn are stationary and mobile. The technology allows you to transmit a radio signal over any distance, even the largest.

Today, the most common type is the active repeater. It significantly amplifies and corrects the incoming signal before it reaches the subscriber. Most of the world's satellite systems use this type of satellite.

The beginning of such technology was laid by the English scientist Arthur C. Clarke, who wrote the article “Extraterrestrial Repeaters.” The principle was that the antenna had to be placed as far as possible in low-Earth orbit, which would allow it to receive signals from ground-based sources and transmit them further. The main feature was that one satellite could control a fairly large coverage area of ​​the globe.

The first passive repeater was the Echo-1 device, which was launched into space in 1960. This marked the beginning of further rapid development international satellite communications.

Application areas of international satellite communications

Since the first artificial satellite was launched into space, the quality of technology has improved significantly. Today humanity cannot imagine everyday life without mobile phone(which victoriously replaced home landlines), without video chats that help communicate with a person at a distance in real time, without television, etc.

The modern use of international satellite communications is divided into the following key areas:

• trunk communication;


• mobile satellite communication system;


• VSAT (a small system with an antenna up to 2.4 m in diameter, used to create a private channel);


• mobile network;


• Internet (most modern technologies work using this system).

International satellite communications is one of the thematic areas of the thematic event, which takes place annually within the walls of the Expocentre Central Exhibition Complex.

Thematic diversity covers all categories of the communications industry:

• Internet technologies;


• software;


• data networks;


• startups;


• telecommunications infrastructure;


• services in the field of IT technologies;


• communication equipment and modern technologies.

Possibilities of modern international satellite communications

Modern high-tech international satellite communications provide the following opportunities:

• exchange information;


• manage and coordinate aircraft, ships, and ground transportation;


• the ability to transmit large amounts of information to the other side of the world;


• receive high and stable signal quality;


• carry out secure communications, etc.

New products in satellite communications of the Russian Federation

Satellite connection has an inevitable impact on the development of various industrial spheres, the economic growth of the state and the standard of living of nations.

Today, the formation of the satellite communications market segment is unimaginable without communication with terrestrial network system. Any changes to the network structure can fundamentally affect the quality of satellite performance.

Satellite communications has the following latest innovations:

• optical fiber networks have led to the partial displacement of satellite highways;


• distribution of VSAT (Very Small Aperture Terminal) antenna stations;


• improving the energy weapons of spacecraft and their ability to transmit remote signals from points on the earth;


• wide-band satellites equipped with a repeater;


• means with large frequency ranges;


• development of medium altitude orbits.

All these innovative devices have led to the ability to process multiple signals in space through inter-beam switches.

Thanks to the latest mechanisms for transferring images and video files, free online communication has become commonplace today.

Market segments of satellite communications in the Russian Federation

Satellite communications in the Russian Federation are economically divided into three large market segments information technologies and communications.

1. The first segment was founded through the connection of ground stations on the territory of the state with the satellite complexes Global Star, Inmarsat, Ellipse, which are developing in positive dynamics. They form compact personal communication terminals that interface with mobile devices television and radio broadcasting. The system’s satellites are located over the oceans to provide high-quality Internet signals to large radii of the earth. The system has a telephone that is tuned to one of the satellites. Communication terminals with large antennas pick up the signal and distribute it to subscribers anywhere in the world.


2. The second segment focuses on the production of small satellite ground terminals (VSAT), intended for the formation of corporate networks with secure access. Nowadays on the territory of the Russian Federation, according to the National Union of Satellite Communications, there are about 3.2% of such stations in the world (500 thousand).


3. In the third segment, satellites, small-format stations and their systems that support television and radio broadcasting and remote online communications are invented and put into production. The cost of equipment for this market niche is several times lower than the terminals of the previous two segments. Considering the geographical advantage of small settlements relative to the entire area of ​​the country, television infrastructure brings the maximum profit among all types of contacts.

In the Russian market, communications are of no small importance for the economic development of the zone where signals processed by multi-mode terminals are distributed.

Signal from the network remote control The RAT (Remote Administration Tool) is divided into codes in CDMA (Code Division Multiple Access) channels and, by scanning, facilitates the execution of paging calls in cycles connected to each other in a separate RAT. It is beneficial to communicate with these areas to places where there is no cellular signal reception.

Multi-mode subscriber terminals wireless communication can increase the efficiency of internetwork switching and increase access to various services.

Modern equipment for receiving and transmitting satellite communications at the exhibition

Modern satellite communications serves as an excellent way to transmit information, but places increased demands on the equipment.

Exhibition "Communication" provides an opportunity to get acquainted with the most latest developments and offers from various manufacturers of equipment for satellite communications.

Within the walls of Expocentre there is a wide range of samples of various price categories on display, so anyone can find the most optimal option in terms of quality and price.

Exhibition "Communication" has been carried out for more than three decades and serves as a powerful engine in the effective development of this technical field.

Satellite communications is one of the types of radio communications based on the use of artificial earth satellites as repeaters. Satellite communications are carried out between earth stations, which can be either stationary or mobile.

Satellite communications is a development of traditional radio relay communications by placing the repeater at a very high altitude (from hundreds to tens of thousands of km). Since its visibility area in this case is almost half of the globe, there is no need for a chain of repeaters. To be transmitted via satellite, the signal must be modulated. Modulation is performed at the earth station. The modulated signal is amplified, transferred to the desired frequency and sent to the transmitting antenna.

Research in the field of civil satellite communications in Western countries began to appear in the second half of the 50s of the 20th century. The impetus for them was the increased need for transatlantic telephone communications. The first artificial Earth satellite was launched in the USSR in 1957, however, due to the greater secrecy of the space program, the development of satellite communications in socialist countries proceeded differently than in Western countries. For a long time, satellite communications were developed only in the interests of the USSR Ministry of Defense. The development of civil satellite communications began with an agreement between 9 countries of the socialist bloc on the creation of the Intersputnik communication system, which was signed only in 1971.

In the first years of research, passive satellite repeaters were used, which were a simple reflector of a radio signal (often a metal or polymer sphere coated with metal), not carrying any transceiver equipment on board. Such satellites have not become widespread. All modern communications satellites are active. Active repeaters are equipped with electronic equipment for receiving, processing, amplifying and relaying the signal. Satellite repeaters can be non-regenerative or regenerative. A non-regenerative satellite, having received a signal from one earth station, transfers it to another frequency, amplifies it and transmits it to another earth station. A satellite can use several independent channels that carry out these operations, each of which works with a certain part of the spectrum (these processing channels are called transponders. A regenerative satellite demodulates the received signal and re-modulates it. Thanks to this, error correction is performed twice: on the satellite and on the receiving ground station The disadvantage of this method is complexity (and therefore a much higher price for the satellite), as well as an increased signal transmission delay.

Communication satellite orbits:

The orbits in which satellite relays are located are divided into three classes:

1 - equatorial, 2 - oblique, 3 - polar

An important variation of the equatorial orbit is the geostationary orbit, in which the satellite rotates with an angular velocity equal to the angular velocity of the Earth, in a direction coinciding with the direction of rotation of the Earth. The obvious advantage of the geostationary orbit is that the receiver in the service area “sees” the satellite constantly. However, there is only one geostationary orbit, and it is impossible to place all satellites into it. Another disadvantage is its high altitude, and therefore the higher cost of launching a satellite into orbit. In addition, a satellite in geostationary orbit is unable to serve earth stations in the polar region.

An inclined orbit solves these problems, however, due to the movement of the satellite relative to an observer on the ground, it is necessary to launch at least three satellites into one orbit to provide 24/7 access to communications.

Polar orbit - extreme case of inclined

When using inclined orbits, earth stations are equipped with tracking systems that point the antenna at the satellite. Stations operating with satellites in geostationary orbit are also typically equipped with such systems to compensate for deviations from the ideal geostationary orbit. The exception is small antennas used to receive satellite television: their radiation pattern is wide enough, so they do not sense satellite vibrations near the ideal point. A feature of most mobile satellite communication systems is the small size of the terminal antenna, which makes signal reception difficult.

A typical scheme for organizing satellite communication services is as follows:

• - a satellite segment operator creates a communications satellite at its own expense, placing an order for the manufacture of a satellite from one of the satellite manufacturers, and launches and maintains it. After the satellite is launched into orbit, the satellite segment operator begins providing services for leasing the frequency resource of the relay satellite to companies operating satellite communication services.
• - a satellite communications services operator enters into an agreement with a satellite segment operator for the use (rent) of capacity on a communications satellite, using it as a repeater with a large service area. A satellite communications service operator builds the ground infrastructure of its network on a specific technological platform produced by companies that manufacture ground-based equipment for satellite communications.

Areas of application of satellite communications:

• - Backbone satellite communications: initially, the emergence of satellite communications was dictated by the needs of transmitting large volumes of information. The first satellite communication system was the Intelsat system, then similar regional organizations were created (Eutelsat, Arabsat and others). Over time, the share of voice transmission in the total volume of trunk traffic has constantly decreased, giving way to data transmission. With the development of fiber-optic networks, the latter began to displace satellite communications from the backbone communications market.
• - VSAT systems: VSAT (Very Small Aperture Terminal) systems provide satellite communication services to clients (usually small organizations) who do not require high throughput channel. The data transfer rate for a VSAT terminal usually does not exceed 2048 kbit/s. The words "very small aperture" refer to the size of the terminal antennas compared to the sizes of older backbone communications system antennas. VSAT terminals operating in the C-band usually use antennas with a diameter of 1.8-2.4 m, in the Ku-band - 0.75-1.8 m. VSAT systems use the technology of providing channels on demand.
• - Mobile satellite communication systems: a feature of most mobile satellite communication systems is the small size of the terminal antenna, which makes signal reception difficult.

Principles of organizing VSAT satellite communications:

A typical VSAT satellite network organization diagram looks like this:

• - relay satellite located in orbit (communications satellite)
• - network control center (NCC) of the VSAT network operator company, servicing the equipment of the entire network via a communications satellite
• - equipment (satellite modems or terminals) located on the client side and interacting with the outside world or with each other through the HUB of the VSAT operator company in accordance with the network topology

The main element of the VSAT satellite network is the NCC. It is the Network Management Center that provides access to client equipment from the Internet, public telephone network, and other terminals of the VSAT network, and implements traffic exchange within the client’s corporate network. The NCC has a broadband connection to trunk communication channels provided by trunk operators and ensures the transfer of information from a remote VSAT terminal to the outside world. The NCC is equipped with a powerful transceiver complex that transmits all network information flows to a communications satellite. The NCC includes channel-forming equipment (satellite transceiver antenna, transceivers, etc.) and a HUB (processing and switching center for all information in the VSAT network)

Technologies used in satellite communications:

reuse of frequencies in satellite communications:

Since radio frequencies are a limited resource, it is necessary to ensure that different earth stations can use the same frequencies. You can do this in two ways:

spatial separation - each satellite antenna receives a signal only from a specific area, while different areas can use the same frequencies.

polarization separation - different antennas receive and transmit signals in mutually perpendicular polarization planes, while the same frequencies can be used twice (for each of the planes).

frequency ranges:

The choice of frequency for transmitting data from an earth station to a satellite and from a satellite to an earth station is not arbitrary. Frequency determines, for example, the absorption of radio waves in the atmosphere, as well as the required dimensions of the transmitting and receiving antennas. The frequencies at which transmission occurs from the earth station to the satellite are different from the frequencies used for transmission from the satellite to the earth station (usually the former being higher). Frequencies used in satellite communications are divided into ranges, designated by letters:

Ku-band allows reception by relatively small antennas, and is therefore used in satellite television(DVB), despite the fact that in this range weather conditions have a significant impact on transmission quality. For data transmission by large users (organizations), C-band is often used. This provides higher quality reception, but requires a fairly large antenna.