Satellite communications: principle of operation, coverage area, channel characteristics and tariff plans. modern satellites

Thanks to outstanding achievements in the field of microelectronics, satellite phones have become so compact and reliable in use that all the demands are being made by various user groups, and the satellite rental service is one of the most demanded 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 communication has the most important advantages necessary for building large-scale telecommunication networks. Firstly, it can be used to quickly form 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 possibility of delivering information to an almost unlimited number of consumers at the same time significantly reduce the cost of network operation. These advantages of satellite communication make it very attractive and highly efficient 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 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 40,000.

The time is approaching for the unification of terrestrial and satellite systems into a global communications system. Personal communication will become possible on a global scale, i.e., the reach of the subscriber anywhere in the world will be ensured by dialing him phone number, regardless of the location of the subscriber. But before this becomes a reality, satellite communications systems will need to successfully pass the tests and confirm the declared technical characteristics and economic indicators in the course of commercial operation. As for consumers, in order to make the right choice, they will have to learn how to navigate well in a variety of offers.

Project goals:

1. Study the history of the satellite communication system.

2. Get acquainted with the features and prospects for the development and design of satellite communications.

3. Get information about modern satellite communications.

Project objectives:

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

2. Get a complete understanding of modern satellite communications.

1. Development of a satellite communication network

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

American scientists became interested in theoretical research, who saw in the article a lot of advantages from a new type of connection:

no need to build a chain of terrestrial repeaters anymore;

one satellite is enough to provide a large coverage area;

the possibility of transmitting a radio signal to anywhere in the world, regardless of the availability of telecommunications infrastructure.

As a result, practical research and the formation of a satellite communications 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 equipment for satellite communications 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 apparatus (a passive repeater in the form of a metallized ball) into space in August 1960. Later, key satellite communication standards (operating frequency bands) were developed and are widely used throughout the world.

The history of the development of satellite communications and the main types of communications

ANDdevelopment history CtravelerWITHsystemsWITHtie has five stages:

1957-1965 The preparatory period, which began in October 1957 after the launch by the Soviet Union of the world's first artificial Earth satellite, and a month later, the second. This happened at the height of the Cold War and the rapid arms race, so, naturally, satellite technology became the property of the military in the first place. 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 in the interests of the US Army and launched into orbit in July 1962. During the same period of time, a series of US military communications satellites SYN-COM (Synchronous Communications Satellite) was developed.

1965-1973 The period of development of global SSN 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. Early satellites of the INTELSAT series provided transcontinental communications and mainly supported backbone communications between a small number of national gateway earth stations providing an interface to national public terrestrial networks.

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

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

1982-1990 The period of rapid development and spread of small earth terminals. In the 1980s, advances in the field of engineering and technology of the key elements of the CCC, 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 satellite earth stations in the immediate vicinity of user offices, thereby solving the “last mile” problem for a huge number of corporate users, created conditions for a comfortable and efficient exchange of information, and made it possible to offload public terrestrial networks. The use of “smart” satellites connections.

From the first half of the 1990s, the SSS entered a quantitatively and qualitatively new stage in 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. During this time period, there was an explosion in the speed of general purpose microprocessors and the volume of semiconductor storage devices, while improving the reliability, as well as reducing the power consumption and cost of these components.

Main types of communication

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

radio relay;

high frequency;

postal;

satellite;

optical;

control room.

Each type has its own technology and complex necessary equipment for full functionality. I will consider these categories in more detail.

Communication via satellite

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

The advantages of this type of connection are obvious:

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

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

increase in coverage area.

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

2. The current state of the satellite communication network

Of the many commercial MSS (Mobile Satellite) projects below 1 GHz, 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 bands, the system allows the provision of low-speed data transfer services, such as e-mail, two-way paging, remote control services, to simple, low-cost subscriber devices. The main users of Orbcomm are transport companies, for which this system provides a cost-effective solution for the control and management of cargo transportation.

The most well-known operator in the MSS market is Inmarsat. There are about 30 types of subscriber devices on the market, 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 is competing with three MSS systems, including 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 a third geostationary (GEO) satellite that will cover the Americas where it is currently unavailable. All three systems provide telephony and low-speed data services 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 single information space on the territory of the state and is closely related to federal programs to eliminate the digital divide, the development of nationwide infrastructure and social projects. The most significant Federal targeted programs on the territory of the Russian Federation are projects on "Development of television and radio broadcasting" and "Elimination of digital inequality". The main tasks of the projects are the development of digital terrestrial television, communication networks, systems of mass broadband access to global information networks and the provision of multi-service services at mobile and moving objects. In addition to federal projects, the development of satellite communication systems provides new opportunities for solving the problems of the corporate market. The fields 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 the Orbital Constellation of Civil Communication and Broadcasting Satellites, including satellites in highly elliptical orbits.

Development of satellite communication systems

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

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

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

entry of satellite operators into the mass market,

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

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 face of decreasing cost of satellite capacity implemented on Ka-band satellites with high bandwidth (High-Throughput Satellite - HTS).

Use of satellite communication systems

Satellite communication systems are designed to meet the needs of communication 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 in organizing multi-channel telephone communication.

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 communication stations.

Such communication systems make it possible to operate from autonomous power for a long time and be in call waiting mode, this happens due to the low energy performance of user equipment, light weight and an omnidirectional antenna.

Currently, there are many different satellite communication systems. All have their pros and cons. Additionally, each manufacturer offers users an individual set of services (Internet, fax, telex), defines 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.

Spheres of use of SSS (Satellite Communication Systems): navigation, ministries and departments, management bodies of state structures and institutions, the Ministry of Emergency Situations and rescue units.

Inmarsat

The world's first mobile satellite communications system offering a full range of advanced services to users around the world: at sea, on land and in the air.

Satellite communication system Inmarsat (Inmarsat) has a number of advantages:

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

the quality of the services provided

confidentiality

additional accessories (car kits, fax machines, etc.)

free incoming calls

availability in use

online system for checking account status (billing)

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

The main services of the satellite communication system Inmarsat (Inmarsat):

Data transfer (including high-speed)

Telex (for some standards)

Iridium (Iridium)

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

The satellite communication system Iridium (Iridium) has a number of advantages:

coverage area - the entire territory of the globe

low tariff plans

free incoming calls

The main services of the Iridium satellite communication system (Iridium):

Data transfer

Paging

Thuraya

A satellite operator that provides service to 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.

Thuraya satellite communication system has a number of advantages:

compact size

the ability to switch between satellite and cellular communications automatically

low cost of services and telephone sets

free incoming calls

The main services of the Thuraya satellite communication system:

Data transfer

3.Satellite communication system

Satellite repeaters

For the first time years of research, passive satellite transponders 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 received distribution.

Orbits of satellite transponders

The orbits in which satellite transponders 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 that coincides with the direction of the Earth's rotation.

An inclined orbit solves these problems, however, due to the movement of the satellite relative to the ground observer, it is necessary to launch at least three satellites per orbit in order to provide round-the-clock communication access.

Polar - an orbit that has an orbital inclination to the plane of the equator of ninety degrees.

4.VSAT system

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

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

A bit of history. The development of VSAT networks begins with the launch of the first communications satellite. In the late 60s, in the course of 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 original creators of Ku-band VSAT, merged with M/A-COM, which later became the leading supplier of VSAT equipment. Hughes Communications acquired the division from M/A-COM, transforming it into Hughes Network Systems. Hughes Network Systems is currently the world's leading provider of broadband satellite communications networks. A VSAT-based satellite communications network includes three key elements: a central control station (CCS), a repeater satellite, and subscriber VSAT terminals.

repeater satellite

VSAT networks are built on the basis of geostationary repeater satellites. The most important characteristics of the satellite are the power of the 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 Mbps. On average, the power of transmitters ranges from 20 to 100 watts. In Russia, Yamal communication and broadcasting satellites can be cited as examples of repeater satellites. They are intended for the development of the space segment of OAO Gascom and were installed in orbital positions 49°E. d. and 90 ° in. d.

Subscriber VSAT terminals

Subscriber VSAT terminal is a small satellite communication station with an antenna with a diameter of 0.9 to 2.4 m, designed mainly for reliable data exchange via satellite channels. The station consists of an antenna-feeder device, an outdoor external radio frequency unit and an indoor unit (satellite modem). The outdoor unit is a small transceiver or just a receiver. The indoor unit provides pairing 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, fiber optic, cellular networks, radio ethernet) is necessarily used, which is used as a request channel (it is also called a reverse channel).

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

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

Today in Russia there are several significant operators VSAT networks that serve about 80,000 VSATs. 33% of such terminals are located in the Central Federal District, 13% each in the Siberian and Ural Federal Districts, 11% in the Far East and 5-8% each in the other federal districts. Among the largest operators it is worth highlighting:

6.Global satellite communication system Globalstar

In Russia, the operator of the satellite communication system Globalstar is the Closed Joint Stock Company GlobalTel. As the exclusive provider of global mobile satellite communication services of the Globalstar system, CJSC GlobalTel provides communication services throughout the Russian Federation. Thanks to the creation of CJSC "GlobalTel", the inhabitants of Russia have another opportunity to communicate via satellite from anywhere in Russia to almost anywhere in the world.

The Globalstar system provides satellite communications High Quality for its subscribers with the help of 48 working and 8 spare low-orbit satellites located at an altitude of 1410 km. (876 miles) from the Earth's surface. The system provides global coverage of almost the entire surface of the globe between 700 North and South latitudes with an extension of up to 740. Satellites are capable of receiving signals 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 part of the oceans . The satellites of the system are simple and reliable.

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 communication, short message service, roaming, positioning, facsimile, data, mobile Internet.

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

The system is designed for a wide consumer: representatives of the media, geologists, workers in the extraction and processing of oil and gas, precious metals, civil engineers, power engineers. Employees of state structures of Russia - 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, fishing and other types of sea and river vessels, railway transport, etc.

satellite communication global mobile

7. Mobile satellite communication systems

A feature of most mobile satellite communications systems is the small size of the terminal antenna, which makes signal reception difficult. In order for the signal strength reaching the receiver to be sufficient, one of two solutions is applied:

The satellites are in geostationary orbit. Since this orbit is 35,786 km away from the Earth, a powerful transmitter is required on the satellite. This approach is used by the Inmarsat system (whose main task is to provide communication services to ships) and some regional operators personal satellite communications (eg Thuraya).

Satellite Internet

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

Access options

There are two ways to exchange data via satellite:

one-way (one-way), sometimes also called "asymmetric" - when a satellite channel is used for data reception, and available terrestrial channels 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 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 speed limited, etc.). Only requests to the Internet are transmitted through this channel.

Two way satellite Internet

Two-way satellite Internet means receiving data from the satellite and sending it back also via the satellite. This method is of very high quality, as it allows you to achieve high speeds during transmission and sending, but it is quite expensive and requires permission for radio transmitting equipment (however, the provider often takes care of the latter). High price two-way internet turns out to be fully 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 (other than power, of course).

A feature of "two-way" satellite Internet access is a sufficiently 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 trip back. Plus, the inevitable delays in signal processing and in order to go "over the Internet". As a result, the ping time on a two-way satellite link 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 chosen one operator working on a certain type of equipment (for example, ViaSat, Hughes, Gilat EMS, Shiron, etc.), then you can only go to the operator using the same equipment. An attempt to implement the compatibility of equipment from different manufacturers (DVB-RCS standard) was supported by a very small number of companies, and today it is more of a "private" technology than a generally accepted standard.

Equipment for one-way satellite Internet

8. Disadvantages of satellite communications

Weak noise immunity

The huge 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 provide an acceptable error probability under these conditions, it is necessary to use large antennas, low noise elements and complex error-correcting codes. This problem is especially acute in mobile communication systems, as they have a limit on the size of the antenna and, as a rule, on the power of the transmitter.

Influence of the atmosphere

The quality of satellite communication 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 are at 22.3 GHz (water vapor resonance) and 60 GHz (oxygen resonance). In general, absorption significantly affects the propagation of signals above 10 GHz (i.e., starting from the Ku-band). In addition to absorption, during the propagation of radio waves in the atmosphere, there is a fading effect, the cause of which is the difference in the refractive indices of different layers of the atmosphere.

Ionospheric effects

Propagation Delay

The problem of signal propagation delay, one way or another, affects all satellite communication systems. Systems using a satellite transponder in geostationary orbit have the highest latency. In this case, the delay due to the finiteness of the radio wave propagation speed 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. In this case, if the signal propagation time over the satellite communication channel is 250 ms, the time difference between subscribers' replicas cannot be less than 500 ms. In some systems (eg, VSAT systems using a star topology), the signal is transmitted twice via a satellite link (from a terminal to a central site, and from a central site to another terminal). In this case, the total delay is doubled.

Conclusion

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

At present, satellite communication stations are combined into data transmission networks. Combining a group of geographically distributed stations into a network makes it possible to provide users with a wide range of services and opportunities, as well as to effectively use satellite resources. In such networks, there is usually one or more control stations that provide operation of earth stations in both administrator-managed and fully automatic modes.

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

SSNs are constantly and jealously compared to fiber optic communication networks. The introduction of these networks is accelerating due to the rapid technological development of the relevant areas of fiber optics, which raises questions about the fate of the SSN. For example, development and planning, most importantly, the introduction of concatenating (composite) coding dramatically reduces the likelihood of an uncorrected bit error, which, in turn, allows you to overcome the main problem of CCC - fog and rain.

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1 Baranov V. I. Stechkin B. S. Extremal combinatorial problems and their

applications, M.: Nauka, 2000, p. 198.

2 Bertsekas D. Gallagher R. Data transmission networks. M.: Mir, 2000, p. 295.

3 Black Yu. Computer networks: protocols, standards, interfaces, M.: Mir, 2001, p. 320.

4 Bolshova G. "Satellite communications in Russia: Pamir", Iridium, Globalstar ..." "Networks" - 2000 - No. 9. - With. 20-28.

5 Efimushkin V. A. Technical aspects of satellite communication systems "Network" - 2000 - No. 7. - With. 19-24.

6 Nevdyaev L. M. Modern technologies of satellite communication // "Bulletin of Communications" - 2000 - No. 12. - p. 30-39.

7 Nevdyaev L. M. Odyssey at medium heights of the "Network" - 2000 - No. 2. - With. 13-15.

8 SPC "Elsov", Protocol on the organization and logic of the satellite data transmission network "Banker". - 2004, p. 235.

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Satellite repeaters

Passive communications satellite Echo-2. Metallized inflatable sphere served as a passive repeater

In the early years of research, passive satellite transponders 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 received distribution. All modern communication satellites are active. Active repeaters are equipped with electronic equipment for receiving, processing, amplifying and retransmitting a signal. Satellite repeaters can be non-regenerative And regenerative. A non-regenerative satellite, having received a signal from one earth station, transfers it to another frequency, amplifies and transmits it to another earth station. A satellite may use several independent channels that perform these operations, each of which operates with a certain part of the spectrum (these processing channels are called transponders).

The regenerative satellite demodulates the received signal and modulates it again. Due to this, error correction is performed twice: at the satellite and at the receiving earth station. The disadvantage of this method is the complexity (and hence the much higher cost of the satellite), as well as the increased signal transmission delay.

Orbits of satellite transponders

The orbits that host satellite transponders are divided into three classes:

equatorial,
oblique,
polar.

An important variety equatorial orbit is a geostationary orbit in which a satellite rotates at an angular velocity equal to that of the Earth, in a direction that is the same as the direction of the Earth's rotation. The obvious advantage of the geostationary orbit is that the receiver in the service area "sees" the satellite all the time.

However, there is only one geostationary orbit, and it is impossible to put all the satellites into it. Its other disadvantage is its high altitude, and hence the high cost of launching a satellite into orbit. In addition, a satellite in geostationary orbit is not capable of serving earth stations in the circumpolar region.

inclined orbit solves these problems, however, due to the movement of the satellite relative to the ground observer, it is necessary to launch at least three satellites into one orbit in order to provide round-the-clock access to communications.

polar orbit- limiting case of oblique (with inclination 90º).

When using inclined orbits, earth stations are equipped with tracking systems that point the antenna at the satellite. Stations operating 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 for receiving satellite television: their radiation pattern is wide enough that they do not feel satellite vibrations near the ideal point.

Reuse of frequencies. Coverage areas

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

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

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

A typical coverage map for a satellite in geostationary orbit includes the following components:

global beam- communicates with earth stations throughout the coverage area, it is allocated frequencies that do not intersect with other beams of this satellite.

rays of the western and eastern hemispheres- these beams are polarized in plane A, and the same frequency range is used in the western and eastern hemispheres.

zone rays- are polarized in plane B (perpendicular to A) and use the same frequencies as the rays of the hemispheres. Thus, an earth station located in one of the zones can also use hemispheric beams and a global beam.

In this case, all frequencies (with the exception of those reserved for the global beam) are used repeatedly: in the western and eastern hemispheres and in each of the zones.

Frequency bands

Antenna for receiving satellite television (Ku-band)

Satellite dish for C-band

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. For example, the absorption of radio waves in the atmosphere depends on the frequency, as well as the required dimensions of the transmitting and receiving antennas. The frequencies at which earth station-to-satellite transmissions occur are different from those used for satellite-to-earth station transmissions (generally the former is higher).

The frequencies used in satellite communications are divided into bands, denoted by letters. Unfortunately, in various literature, the exact boundaries of the ranges may not coincide. Indicative values are given in the ITU -R V.431-6 recommendation:

Range name	Frequencies (according to ITU-R V.431-6)	Application
L	1.5 GHz	Mobile satellite communications
S	2.5 GHz	Mobile satellite communications
WITH	4 GHz, 6 GHz	Fixed satellite communications
X	For satellite communications, ITU-R recommendations do not define frequencies. For radar applications, the 8-12 GHz range is specified.	Fixed satellite communications (for military purposes)
Ku	11 GHz, 12 GHz, 14 GHz
K	20 GHz	Fixed satellite communication, satellite broadcasting
Ka	30 GHz	Fixed satellite communications, inter-satellite communications

Higher frequencies are also used, but their increase is hampered by the high absorption of radio waves of these frequencies by the atmosphere. Ku-band allows reception with relatively small antennas, and therefore is used in satellite television (DVB), despite the fact that weather conditions have a significant impact on transmission quality in this band.

For data transmission by large users (organizations), the C-band is often used. This provides better reception quality, but requires a rather large antenna.

Modulation and noise-correcting coding

A feature of satellite communication systems is the need to work in conditions of a relatively low signal-to-noise ratio due to several factors:

a considerable distance between the receiver and the transmitter,
limited satellite power (inability to transmit at high power).

As a result, satellite communications are not well suited for transmitting analog signals. Therefore, to transmit speech, it is pre-digitized using, for example, pulse code modulation (PCM).

To transmit digital data over a satellite communication channel, they must first be converted into a radio signal occupying a certain frequency range. To do this, modulation is used (digital modulation is also called manipulation). The most common types of digital modulation for satellite communications applications are phase shift keying and quadrature amplitude modulation. For example, DVB-S2 systems use QPSK, 8-PSK, 16-APSK and 32-APSK.

The modulation is done at the earth station. The modulated signal is amplified, transferred to desired frequency and goes to the transmitting antenna. The satellite receives a signal, amplifies, sometimes regenerates, transfers to another frequency and, using a certain transmitting antenna, broadcasts to the ground.

Multiple Access

To ensure the simultaneous use of a satellite transponder by several users, multiple access systems are used:

Frequency division multiple access - whereby each user is given a separate frequency band.

time division multiple access - each user is given a certain time interval (timeslot) during which he transmits and receives data.

code division multiple access - in this case, each user is given a code sequence orthogonal to the code sequences of other users. User data is superimposed on the code sequence in such a way that the transmitted signals of different users do not interfere with each other, although they are transmitted on the same frequencies.

In addition, many users do not need constant access to satellite communications. For these users, a communication channel (timeslot) is allocated on demand using DAMA (Demand Assigned Multiple Access) technology.

Application of satellite communications

Backbone satellite communications

Initially, the emergence of satellite communications was dictated by the need to transmit large amounts 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 backbone traffic has been constantly decreasing, 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

The words "very small aperture" refer to the size of the terminal antennas compared to older backbone antennas. VSAT terminals operating in the C-band usually use antennas with a diameter of 1.8-2.4 m, in Ku-band - 0.75-1.8 m.

VSAT systems use on-demand channeling technology.

Mobile satellite communication systems

Many satellites are located on oblique or polar orbits. At the same time, the required transmitter power is not so high, and the cost of launching a satellite into orbit is lower. However, this approach requires not only a large number of satellites, but also an extensive network of terrestrial switches. A similar method is used by Iridium and Globalstar operators.

Cellular operators compete with operators of personal satellite communications. Characteristically, both Globalstar and Iridium experienced serious financial difficulties that brought Iridium to reorganizational bankruptcy in 1999

In December 2006, an experimental geostationary satellite Kiku-8 was launched with a record large antenna area, which is supposed to be used to test the technology of satellite communications with mobile devices no larger than cell phones.

Satellite Internet

Satellite communication finds application in the organization of the "last mile" (communication channel between the Internet provider and the client), especially in places with poorly developed infrastructure.

Features of this type of access are:

Separation of incoming and outgoing traffic and attraction of additional technologies for their combination. Therefore, these compounds are called asymmetrical.
Simultaneous use of an incoming satellite channel by several (for example, 200) users: data is simultaneously transmitted via satellite for all clients “mixed”, the client terminal is engaged in filtering unnecessary data (for this reason, “Satellite fishing” is possible).

According to the type of outgoing channel, there are:

Terminals that work only to receive a signal (the cheapest connection option). In this case, for outgoing traffic, you must have another Internet connection, the provider of which is called ground provider. To work in such a scheme, a tunneling software, usually supplied with the terminal. Despite the complexity (including the difficulty in setting up), this technology is attractive for its high speed compared to dial-up for a relatively low price.
Receiving and transmitting terminals. The outgoing channel is organized narrow (compared to the incoming one). Both directions are provided by the same device, and therefore such a system is much easier to set up (especially if the terminal is external and connected to the computer via an Ethernet interface). Such a scheme requires the installation of a more complex (receiving-transmitting) converter on the antenna.

In both cases, data from the provider to the client is transmitted, as a rule, in accordance with the standard digital broadcasting DVB, which allows you to use the same equipment for both network access and satellite TV reception.

Disadvantages of satellite communications

Weak noise immunity

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 are at 22.3 GHz (water vapor resonance) and 60 GHz (oxygen resonance). In general, absorption significantly affects the propagation of signals above 10 GHz (i.e., starting from the Ku-band). In addition to absorption, when radio waves propagate in the atmosphere, there is a fading effect, the cause of which is the difference in the refractive indices of different layers of the atmosphere.

Ionospheric effects

Effects in the ionosphere are due to fluctuations in the distribution of free electrons. Ionospheric effects that affect the propagation of radio waves include flicker, absorption, propagation delay, dispersion, frequency change, rotation of the plane of polarization. All these effects are attenuated with increasing frequency. For signals with frequencies greater than 10 GHz, their influence is small.

Relatively low frequency signals (L-band and partly C-band) suffer from ionospheric flicker arising from inhomogeneities in the ionosphere. The result of this flickering is a constantly changing signal strength.

Propagation Delay

The problem of signal propagation delay in one way or another affects all satellite communication systems. Systems using a satellite transponder in geostationary orbit have the highest latency. In this case, the delay due to the finiteness of the radio wave propagation speed 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. In this case, if the signal propagation time over the satellite communication channel is 250 ms, the time difference between subscribers' replicas cannot be less than 500 ms.

In some systems (eg, VSAT systems using a star topology), the signal is transmitted twice via a satellite link (from a terminal to a central site, and from a central site to another terminal). In this case, the total delay is doubled.

Influence of solar interference

Notes

Vishnevsky V. I., Lyakhov A. I., Portnoy S. L., Shakhnovich I. V. Historical essay on the development of network technologies // Broadband networks for information transmission. - Monograph (published with the support of the Russian Foundation for Basic Research). - M .: "Technosphere", 2005. - S. 20. - 592 p. - ISBN 5-94836-049-0
Communications Satellite Short History. The Billion Dollar Technology
Communications Satellite Short History. The Global Village: International Communications
INTELSAT Satellite Earth Station Handbook, 1999, p. 18
Sklyar B. Digital communication. Theoretical foundations and practical application. Ed. 2nd, corrected: Per. from English. - M.: Williams Publishing House, 2004
Official website of Intersputnik
Conceptual and legal issues of broadband satellite multiservice networks
Dennis Roddy. satellite communications. McGraw-Hill Telecommunications, 2001, p. 167
INTELSAT Satellite Earth Station Handbook, 1999, p. 2
INTELSAT Satellite Earth Station Handbook, 1999, p. 73
Dennis Roddy. satellite communications. McGraw-Hill Telecommunications, 2001, pp. 6, 108
INTELSAT Satellite Earth Station Handbook, 1999, p. 28
Recommendation ITU-R V.431-6. Nomenclature of the frequency and wavelength bands used in telecommunications
Dennis Roddy. satellite communications. McGraw-Hill Telecommunications, 2001, pp. 6, 256
Dennis Roddy. satellite communications. McGraw-Hill Telecommunications, 2001, p. 264
http://www.telesputnik.ru/archive/116/article/62.html DVB-S2 standard. New challenges - new solutions // Journal of satellite and cable television and telecommunications "Telesputnik"
Dennis Roddy. satellite communications. McGraw-Hill Telecommunications, 2001, p. 283
Morelos-Zaragoza R. The art of error-correcting coding. Methods, algorithms, application / per. from English. V. B. Afanasiev. - M .: Technosphere, 2006. - 320 p. - (World of communication). - 2000 copies. - ISBN 5-94836-035-0
Dr. Lin Nan Lee LDPC Codes, Application to Next Generation Communication Systems // IEEE Semiannual Vehicular Technology Conference. - October, 2003.
Bernard Sklar. Digital communication. Theoretical foundations and practical application = Digital Communications: Fundamentals and Applications. - 2nd ed. - M .: "Williams", 2007. - S. 1104. - ISBN 0-13-084788-7
Satellite communication and broadcasting system "Yamal"
VSAT FAQ
Dennis Roddy. satellite communications. McGraw-Hill Telecommunications, 2001, p. 68
Satellite Internet and VSAT Information Centrum
Satellite Communications and Space Weather
Dennis Roddy. satellite communications. McGraw-Hill Telecommunications, 2001, p. 91
Dennis Roddy. satellite communications. McGraw-Hill Telecommunications, 2001, p. 93
Bruce R. Elbert. The Satellite Communication Applications Handbook. - Artech House, Inc., 2004, p. 34.
Satellite Communications in the Global Internet: Issues, Pitfalls, and Potential

Mobile satellite communications

Introduction

Any communication system ultimately depends on some basic system parameters that determine the quality of communication.

So, if for cellular communication such a main parameter is the height of the base station antenna, then for satellite communication systems it is the type of orbit of its space segment and the characteristics of the orbit. In general, any satellite communication system consists of three segments, as mentioned above: space (or space constellation), ground (ground service stations, gateway stations) and user segment (directly terminals located at the consumer).

Figure 1 The structure of the satellite communication system on the example of the VSAT network of the State Enterprise "Cosmic" communication"

According to the type of orbits used, satellite communication systems are divided into two classes: systems with satellites in geostationary orbit (GEO) (altitude 36,000 km; the number of satellites for the GEO constellation is 3, one satellite covers 34% of the earth's surface; communications - 600 ms) and non-geostationary.

Figure 2. Orbits and coverage areas of the earth's surface on the example of the geostationary space constellation of the INMARSAT system

Non-geostationary satellite systems, in turn, are divided into medium-altitude MEO (height - 5000-15000 km; number of spacecraft - 8-12; coverage area of one satellite - 25-28%; delay in voice transmission for global communications - 250-400 ms) and low-orbit LEO (height - 500-2000 km; number of spacecraft - 48-66; coverage area of one satellite - 3-7%; voice transmission delay for global communication - 170-300 ms).

Most of the existing satellite communication systems have geostationary satellite constellations, which is easily explained: a small number of satellites, coverage of the entire surface of the earth. However, a large signal delay makes them applicable, as a rule, only for radio and television broadcasting. For radiotelephone communication systems, a large signal delay is highly undesirable, as it leads to poor communication quality and an increase in the cost of the user segment. Therefore, initially, most satellite communication systems provided mainly fixed satellite communications (communication between stationary objects), and only with the introduction digital methods communications and the launch of non-geostationary spacecraft, mobile satellite communications have been widely developed. Note that modern mobile satellite communication systems, firstly, are compatible with traditional terrestrial mobile communication systems (primarily with digital cellular), and, secondly, the interaction of mobile satellite radio networks with the public telephone network is possible at any level. (local, intrazonal, intercity).

The main global mobile satellite communications operators known in Russia

Iridium system (international consortium Iridium lls, Washington). The Iridium global mobile personal satellite communication system was intended to provide communication services with mobile and fixed objects located throughout the globe. The space segment of the system consisted of 66 main (orbit height 780 km above the Earth's surface) and 6 backup satellites (645 km). The system provided subscribers with the following services: voice transmission (2.4 Kbps), data transmission and telefax at the same speed, personal call and location determination.

Being a very expensive project (more than 5 billion dollars), Iridium set ultra-high prices for terminals and traffic at the initial stage of development, erroneously targeting only very rich consumers of the service. In addition, technical and financial problems unforeseen by the project arose during operation, which led the consortium to bankruptcy.

Globalstar system (Globalstar ltd., San Jose, California). The system of global mobile personal satellite communications "Globalstar" is designed to provide communication services with mobile and fixed objects located on the globe between 700 * north latitude. and 700*S

Portable terminals of the "Globalstar" system are produced in several modifications to ensure the possibility of their use both for organizing communication in the "Globalstar" system and in networks of terrestrial cellular communication of the GSM, AMPS, CDMA standards.

The space segment of the system is a constellation of 48 main and 8 standby satellites, weighing less than 450 kg, placed in circular orbits at an altitude of 1414 km above the Earth's surface. The first generation satellites are designed to operate in full load mode for at least 7.5 years.

To cover the populated territory of the globe, it is planned to build about 50 interface stations, providing maximum coverage (up to 85%) of the earth's surface with the space segment of the system. At the first stage of system development, 38 interface stations were built. There are 3 such stations in operation in Russia: in the Moscow region (Pavlov Posad), in Novosibirsk and in Khabarovsk. These stations ensure the provision of mobile services with high quality of service practically throughout Russia south of 700 north latitude. Each of these stations is connected to the Russian public network. The Globalstar system has been in operation in Russia since May 2000.

ICO system (international company ICO Global Communications). The system of global mobile personal satellite communications "ICO" is designed to provide communication services with mobile and fixed objects throughout the globe, including polar regions. The company "ICO Global Communications" was established on the initiative of the international organization "INMARSAT". It is a truly international organization. None of the countries plays a dominant role in it. More than 60 companies around the world are ICO investors.

It is planned that the ICO system will work in conjunction with cellular communication systems, providing services to regions and zones not covered by cellular radio communication systems. According to the project, most of the subscriber terminals of the ICO system will be personal pocket telephones capable of operating in two modes (satellite/terrestrial cellular). The estimated cost of the subscriber terminal of the ICO system is $1,000, one minute of traffic is $1.

The space segment of the system will be represented by a constellation of 10 main and 2 backup satellites in the MEO orbit at an altitude of approximately 10,390 km above the Earth's surface.

A feature of this system will be a specially formed network "IcoNet", which will connect twelve satellite access nodes (SAN) located around the world with "intelligent" communication lines, and will provide a quick connection of public networks with mobile terminals and mobile terminals to each other, regardless from their location. On the territory of Russia, it is planned to build one USD. The infrastructure of the terrestrial segment of the ICO system is based on the proven architecture of GSM networks, as well as standard components used in large quantities to ensure the compatibility of the ICO system with other terrestrial cellular communication standards.

The ICO system plans to provide users with the following types of services: teleservices, transport environment services, services provided in the GSM system, messaging and roaming services.

Teleservices will provide services such as: digital telephony, emergency calls, group 3 fax transmission at speeds up to 14.4 kbps and short message services. At the same time, digital telephony will provide voice quality similar to that provided by existing land mobile radio standards.

In addition, the ICO system plans to provide services for the transmission of low-speed transparent and non-transparent data in asynchronous mode at speeds of 300, 1200, 2400, 4800 and 9600 bps and transparent data in synchronous mode at speeds of 1200, 2400, 4800 and 9600 bps. /With.

Due to the financial problems of the consortium, it was decided to merge ICO Global Communications with Teledesic Corporation, which would delay the start of services until 2003. One USD on the territory of Russia is supposed to be built by the same date. It is expected that 450,000 subscribers will use the ICO system in Russia.

System INMARSAT(company «INMARSAT ltd.», London). INMARSAT owns satellites installed in geostationary orbit at the following positions: 54*W, 15.5*W, 64.5*E, 178*E. This provides an almost global connection between 75 * S.l. and 75* s.l.

More than 50 earth stations operate in the INMARSAT system, providing communication with mobile equipment installed on sea and river vessels, drilling platforms, aircraft, vehicles (practically none in Russia), in business cases.

The following types of mobile stations are used: "INMARSAT-A", "INMARSAT-B", "INMARSAT-M", "INMARSAT-mini-M", "INMARSAT-C", "INMARSAT-D +" (pager with answer), " INMARSAT-aero" (various types). The listed types of stations have different physical and electrical characteristics, which determines a large difference in the price of stations, the tariff for communication and its quality (information transfer rate, voice transmission quality).

Currently, about 170 thousand stations of all types operate in the INMARSAT system, of which about 10 thousand have Russian numbers (are Russian).

ORBCOM system (ORBCOM Global, Dallas, Virginia). The ORBCOM communication system is intended for two-way data transmission and object location determination using low-orbit artificial Earth satellites (from 28 to 48 satellites). Data transmission on the satellite-to-Earth line is carried out at a speed of 4.8 Kbps, and on the Earth-to-satellite line - 2.4 Kbps. The system was developed in the USA by ORBCOM Global to meet the needs for information exchange with areas remote from the existing terrestrial telecommunications infrastructure.

The main drawback of the system is the lack of a telephone service.

News from global satellite operators

One of the most sensational and well-known projects of global satellite communications is the project of the Iridium concern. In November 2000, the US Bankruptcy Court transferred control of Iridium to a venture capital firm. As a result, this seemingly long-lost company was awarded a $72 million project to equip the US Department of Defense with mobile satellite communications. This is all the more interesting because the tender was won against another large and most dynamically developing operator at the moment - the Globalstar company.

This year was generally unsuccessful for Globalstar (despite receiving a large order for equipping bus handsets in Brazil and launching the system in Russia). It began with the refusal of the main shareholders ("Loral Space & Communications Ltd" and "QUALCOMM"), from further participation in the Globalstar projects. However, a little later, the much needed $183 million was found, and the company continued its activities. In November, Globalstar announced its results for the third quarter of 2000. The company's revenues amounted to $1.4 million, losses - $97.5 million. Compared to the same period in 1999, the company's losses per share increased almost five times and amounted to $1 per share (in 1999 - 20 cents per share). share). At the end of the third quarter, the company served 21,300 subscribers, twice as many as at the end of the second quarter of 2000. The company's management believes that this is extremely small for the successful operation of the global satellite communications system, but on the whole evaluates the project as viable and claims that the company has the financial resources necessary for its activities until the end of May 2001.

At the same time, Globalstar's losses did not lead to a deterioration in the financial position of its major shareholder, QUALCOMM (a supplier of satellite data transmission systems, which is a competitor in this business to ORBCOMGlobal with services such as Trackmaile-, "Omni-track" and "Euteltrack"). This was mainly due to other projects of the concern. QUALCOMM owns the main patents for CDMA wireless technology, WCDMA 3G technology (third generation mobile communications, standard developed by European companies), 3G cdma2000 technology (standard developed by QUALCOMM).

American Mobile Satellite Corp continued its course of developing fleet management communication services and data transmission systems over its ARDIS terrestrial network.

The Japanese company NTT DoCoMo provides communications services for the national fleet. The Australian company "Optus" serves more than 9,000 subscribers. The European EMCAT network offers a full range of mobile services, while the Belgian mobile satellite network IRIS provides satellite data transmission.

The project of ICO Global Communications has been suspended. The commissioning of the system is scheduled for no earlier than 2003.

On October 20, 2000, Boeing Satellite Systems successfully launched the Thuraya 1 satellite as part of its own mobile satellite communications deployment project, which is expected to cover the Middle East, North and Central Africa, Europe, Central Asia and India (number of residents - up to 1, 8 billion people).

Mobile satellite operators in Russia. INMARSAT

After the termination of the activities of the Iridium company, two mobile satellite communications operators remained in Russia: INMARSAT and Globalstar.

The INMARSAT system was created in 1979 in the USSR to establish satellite communications with sea vessels and ensure the safety of navigation. INMARSAT currently manages a global satellite constellation that is used to provide voice, facsimile, telex and multimedia communication services to mobile users. Satellites of the INMARSAT system are located in geostationary orbit. Guaranteed communication is provided on average from 70°S. up to 70° N Each satellite covers approximately one third of the Earth.

However, although the INMARSAT system has quite a few subscribers in Russia, it cannot be said that its use is widespread. The main reason is the high price of user terminals and the high tariff for communication. For example, the tariff for 1 minute of telephone communication when using various types of subscriber stations is: for "INMARSAT-A" - about 6.0-6.5 dollars, for "INMARSAT-B" - about 4.0 dollars, for "INMARSAT- mini-M" - about 2.5 dollars, for "INMARSAT-aero" - about 6.0-6.5 dollars. The cost of terminals ranges from $3,000 to $15,000. So, the most common standard "INMARSAT-mini-M" has the dimensions of a "laptop", weight is about 2 kg, price is $3000.

Models of satellite portable terminals of the "INMARSAT-mini-M" type, available for sale in the Russian Federation

Figure 3.TT-3060A

The TT-3060A mobile phone of the INMARSAT satellite system is designed to transmit telephone and facsimile messages, data and e-mail. Built-in battery and voltage converter provide non-volatile operation for 48 hours in standby mode and 2.5 hours in talk mode. The handset, RJ-11 2-wire fax connector, and a Hayes-compatible 2.4Kbps data port all have personal telephone numbers (4 in total). The ability to protect against unauthorized access is provided by the built-in SIM card reader. It is possible to connect STU-IIB/STU-III cryptographic equipment and use image transfer software. Magnesium alloy body weighing less than 2.2kg.

Rice. 4. World Phone Hybrid

WorldPhone Hybrid provides access to international telephone network with the ability to send faxes, data and e-mail. Key Features: 4.8Kbps Voice, 2.4Kbps Fax, 3 Hour Talk Time, Backlit LCD Display, Speakerphone, Short Message Service (SMS), Voice/Fax Mail, Call Forwarding, Notebook.

Mobile satellite operators in Russia. "Globalstar"

A subsidiary of GlobalTel (a joint venture between Globalstar and Rostelecom) began to provide its services on the territory of the Russian Federation in May 2000. At the moment it is telephony (voice transmission) and call forwarding. The system also provides, but has not yet implemented the following services: data transmission, facsimile communication, transmission and reception of short messages, global roaming, object location, voice mail, emergency call.

The space segment includes a constellation of 48 low-orbit (and 4 standby) satellites providing coverage from 70°N. up to 70° and placed by 6 satellites in 8 circular orbits at an altitude of 1414 km. The system of low-orbit satellites makes it possible to drastically reduce the cost of a subscriber terminal and a minute of conversation.

The user segment consists of portable mobile and stationary terminal devices. Devices can work in several modes (up to three). Dual- and tri-mode devices, in addition to accessing the Globalstar system, can also be used to access terrestrial cellular networks in GSM standards, AMPS, CDMA..

Prices for subscriber terminals: mobile $1000-1900 (depending on the manufacturer), stationary - from $3000. Tariff for 1 min. outgoing traffic within Russia — $1.2-2.0 (including the public network tariff).

Models of satellite portable mobile terminals available on the Russian market that support Globalstar services

Rice. 5. Ericsson portable subscriber mobile terminal

Dual mode Ericsson terminal. The contract for the production of handsets also includes the supply of car and / or stationary subscriber terminals. Working hours - Globalstar | GSM. Dimensions mm - 160 × 60 × 37. Weight - 350g. Talk time Globalstar /GSM hours - ?. The standby time of Globalstar /GSM hours is 5/36.

Rice. 6. Portable subscriber mobile terminal Telit

Telit terminal provides communication in Globalstar modes | GSM and has the following characteristics: dimensions mm - 220 × 65 × 45; weight - 300g; talk time Globalstar /GSM hours - ?; standby time Globalstar /GSM hours - 36/36.

Rice. 7. Qualcomm portable mobile subscriber terminal

Qualcomm Tri-Mode Terminal - Globalstar | AMPS | CDMA. Dimensions mm - 178 × 57 × 44. Weight - 357g. Talk time Globalstar /APMS/CDMA hours - 1/1/3. Standby time Globalstar /AMPS/CDMA hours is 5/7/25. Display 4×16 characters, address book for 99 numbers, fast auto redial, voice mail, message reception, caller ID.

Conclusion

At the moment, despite certain failures (the bankruptcy of the Iridium concern, the suspension of the ICO project, the losses of Globalstar), mobile satellite communications have occupied their (what?) Segment of the global communications market. Sales of user terminals are steadily growing, the number of telecom operators is increasing (satellite launches by Boeing, development of a new generation of small satellites by Intersputnik), and investor interest is not weakening. At the same time, it is necessary to constantly monitor developments in this market segment and keep a “hand on the pulse” so that users of mobile satellite phones in Russia do not find themselves in a situation similar to the one that developed in Russia with the termination of the Iridium concern, when the owners did not know what to do with the pipes, which in an instant turned into a pile of iron. Let's hope that in the foreseeable future such serious cataclysms will not repeat, and the cost of user terminals and traffic will gradually equal the cost of conventional cellular communications.

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Project content:

Introduction

3.Satellite communication system

4. Application of satellite communication

5.VSAT technology

7.Mobile satellite communication systems

8. Disadvantages of satellite communications

9. Conclusion

Introduction

Modern realities are already talking about the inevitability of replacing conventional mobile and, moreover, landline phones with satellite communications. The latest satellite communication technologies offer viable technical and cost-effective solutions for the development of both universal communication services and direct voice and TV broadcasting networks. Thanks to outstanding achievements in the field of microelectronics, satellite phones have become so compact and reliable in use that all the demands are being made by various user groups, and the satellite rental service is one of the most demanded 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 communication today is 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. The satellite is the only technically feasible and cost-effective solution if the population density is lower than 1.5 people/km2.Satellite communication has the most important advantages necessary for building large-scale telecommunication networks. Firstly, it can be used to quickly form 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 possibility of delivering information to an almost unlimited number of consumers at the same time significantly reduce the cost of network operation. These advantages of satellite communication make it very attractive and highly efficient 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 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 40,000.

In recent years, modern types and means of communication have been increasingly introduced in Russia. But, if a cellular radiotelephone has already become familiar, then 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 daily use of personal satellite communication systems (SPSS). The time is approaching for the unification of terrestrial and satellite systems into a global communications system. Personal communication will become possible on a global scale, i.e., the reach of the subscriber anywhere in the world will be ensured by dialing his telephone number, regardless of the location of the subscriber. But before this becomes a reality, satellite communications systems will need to successfully pass the tests and confirm the declared technical characteristics and economic indicators in the course of commercial operation. As for consumers, in order to make the right choice, they will have to learn how to navigate well in a variety of offers.

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 a satellite communication system at all its stages.

2. Get a complete understanding of modern satellite communications.

1. Development of a satellite communication network

American scientists became interested in theoretical research, who saw in the article a lot of advantages from a new type of connection:

no need to build a chain of terrestrial repeaters anymore;

one satellite is enough to provide a large coverage area;

the possibility of transmitting a radio signal to anywhere in the world, regardless of the availability of telecommunications infrastructure.

As a result, practical research and the formation of a satellite communications 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 equipment for satellite communications improved. Now this method of information exchange has become available not only to large corporations and military companies, but also to individuals.

1.1 The history of the development of satellite communications and the main types of communications

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

1973-1982 The stage of wide dissemination of regional and national CCC. At this stage of the historical development of the CCC, the international organization Inmarsat was created, which deployed the Inmarsat global communications network, the main purpose of which was to provide communication with sea vessels in navigation. Later, Inmarsat extended its services to all types of mobile users.

From the first half of the 1990s, the SSS entered a quantitatively and qualitatively new stage in its development.

Main types of communication

Given the wide scope, I will highlight the most common types of communication 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-fledged functioning. I will consider these categories in more detail.

Communication via satellite

The advantages of this type of connection are obvious:

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

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

increase in coverage area.

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

2. The current state of the satellite communication network

Of the many commercial MSS (Mobile Satellite) projects below 1 GHz, one Orbcomm system has been implemented, which includes 30 non-geostationary (non-GSO) satellites providing Earth coverage.

The development of satellite communication systems plays a significant role in the formation of a single information space on the territory of the state and is closely related to federal programs to eliminate the digital divide, the development of nationwide infrastructure and social projects. The most significant Federal targeted programs in the territory of the Russian Federation are the projects on "Development of TV and Radio Broadcasting" and "Elimination of Digital Divide". The main tasks of the projects are the development of digital terrestrial television, communication networks, systems of mass broadband access to global information networks and the provision of multi-service services at mobile and moving objects. In addition to federal projects, the development of satellite communication systems provides new opportunities for solving the problems of the corporate market. The fields of application of satellite technologies and various satellite communication systems are rapidly expanding every year.

Development of satellite communication systems

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

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

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

entry of satellite operators into the mass market,

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

The general trend in the global satellite services market is the rapid growth of data transfer rates provided on satellite resources, which meets the basic requirements of modern multimedia applications and meets the development of software and the growth in the volume of data transmitted 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 face of decreasing cost of satellite capacity implemented on Ka-band satellites with high bandwidth (High-Throughput Satellite - HTS).

Use of satellite communication systems

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 communication stations.

Spheres of use of SSS (Satellite communication systems): navigation, ministries and departments, governing bodies of state structures and institutions, the Ministry of Emergency Situations and rescue units.

The world's first mobile satellite communication system offering a full range of modern services to users around the world:, and in the spirit.

Satellite communication system Inmarsat (Inmarsat) has a number of advantages:

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

the quality of the services provided

confidentiality

additional accessories (car kits, fax machines, etc.)

free incoming calls

availability in use

online system for checking account status (billing)

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

The main services of the satellite communication system Inmarsat (Inmarsat):

Telephone

Fax

Data transfer (including high-speed)

Telex (for some standards)

GPS

The satellite communication system Iridium (Iridium) has a number of advantages:

coverage area - the entire territory of the globe

low tariff plans

free incoming calls

The main services of the Iridium satellite communication system (Iridium) :

Telephone

Data transfer

Paging

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

Thuraya satellite communication system has a number of advantages:

compact size

the ability to switch between satellite and cellular communications automatically

low cost of services and telephone sets

free incoming calls

The main services of the Thuraya satellite communication system:

Telephone

Data transfer

GPS

3.Satellite communication system

3. 1. Satellite repeaters

3.2 Orbits of satellite transponders

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

equatorial

inclined

polar

Polar - an orbit that has an orbital inclination to the plane of the equator of ninety degrees.

4.VSAT system

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

4.1.Satellite repeater

4.2 Subscriber VSAT terminals

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, fiber optic, cellular networks, radio ethernet) is necessarily used, which is used as a request channel (it is also called a reverse channel).

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

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

Today, there are several significant VSAT network operators in Russia, which serve 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 East and 5-8% each in the other federal districts. Among the largest operators it is worth highlighting:

6.Global satellite communication system Globalstar

The Globalstar system provides high quality satellite communications for its subscribers with the help of 48 working and 8 spare low-orbit satellites located at an altitude of 1410 km. (876 miles) from the Earth's surface. The system provides global coverage of almost the entire surface of the globe between 700 North and South latitudes with an extension of up to 740. Satellites are capable of receiving signals 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 part of the oceans . The satellites of the system 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, facsimile, data, mobile Internet.

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

7.1. Mobile satellite communication systems

The satellites are in geostationary orbit. Since this orbit is 35,786 km away from the Earth, a powerful transmitter is required on the satellite. This approach is used by the Inmarsat system (whose main task is to provide communications services to ships) and some regional personal satellite communications operators (for example, Thuraya).

7.1. Satellite Internet

Satellite Internet - a way to provide 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 satellite internet

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

Two way satellite Internet

Two-way satellite Internet means receiving data from the satellite and sending it back also via the satellite. This method is of very high quality, as it allows you to achieve high speeds during transmission and sending, but it is quite expensive and requires permission for radio transmitting equipment (however, the provider often takes care of the latter). The high cost of two-way Internet is fully justified due to the much more reliable connection in the first place. Unlike one-way access, two-way satellite Internet does not require any additional resources (other than power, of course).

A feature of "two-way" satellite Internet access is a sufficiently large delay on the communication channel. Until the signal reaches the subscriber to the satellite and from the satellite to the Central satellite communication station, it will take about 250 ms. The same amount is needed for the trip back. Plus, the inevitable delays in signal processing and in order to go "over the Internet". As a result, the ping time on a two-way satellite link 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.

Equipment for one-way satellite Internet

8. Disadvantages of satellite communications

Weak noise immunity

Influence of the atmosphere

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

Absorption in the troposphere

Ionospheric effects

Propagation Delay

9. Conclusion

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

12. List of sources used

Baranov V. I. Stechkin B. S. Extremal combinatorial problems and their

applications, M.: Nauka, 2000, p. 198.

Bertsekas D. Gallagher R. Data transmission networks. M.: Mir, 2000, p. 295.

Black Yu. Computer networks: protocols, standards, interfaces, M.: Mir, 2001, p. 320.

Bolshova G. "Satellite communications in Russia: "Pamir", Iridium, Globalstar..." "Networks" - 2000 - №9. - With. 20-28.

Efimushkin V. A. Technical aspects of satellite communication systems "Networks" - 2000 - No. 7. - With. 19-24.

Nevdyaev L. M. Modern technologies of satellite communication // "Bulletin of Communications" - 2000 - No. 12. - p. 30-39.

Nevdyaev L. M. Odyssey at medium heights of the "Network" - 2000 - No. 2. - With. 13-15.

SPC "Elsov", Protocol on the organization and logic of the satellite data transmission network "Banker". – 2004, p. 235.

Smirnova A. A. Corporate satellite and HF communication systems Moscow, 2000, p.

Smirnova A. A. Personal satellite communication, Volume 64, Moscow, 2001, p.

Modern satellite communications is one of the directions in the development of radio relay communications. In this case, this is the use of orbiting satellites as repeaters.

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

All repeaters can be divided into two categories:

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

active. Such devices further 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

What is the working principle?

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

The main advantage was the huge coverage area that could be monitored 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 apparatus (a passive repeater in the form of a metallized ball) into space in August 1960.

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

Applications of satellite communications

Since the 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 conditional areas:

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

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.

For more information about the development of this area of communication, it is enough to visit the profile event. The international exhibition "Communication", which takes place on the territory of the Central Exhibition Complex "Expocentre", is the best industry event of the international level. This guarantees the presence of a wide exposition and the participation of well-known world and domestic specialized companies.

How modern satellite communication equipment works

Satellite communication is 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 the inhabitants.

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

It is due to the fact that modern satellite communications have such a wide coverage that the ability to make calls from the most remote corners of the world has become a reality. No serious tourist would dare to take 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 options for navigators were created for a wide variety of industries.

In fact, modern satellite communication consists of only three elements: a transmitter, a repeater and a receiver. Act as transmitter and receiver various devices A: mobile phones, computers, antennas and so on.

The repeater is presented in the form of a satellite that receives an incoming signal from an earth station (or device) and broadcasts it to the entire visible area in broadcast mode. Further, hardware and software come into force, which makes sure that this information gets exactly to the addressee. The exception is when all receivers must receive the signal. For example, satellite TV.

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

MD with frequency division. Each user gets their own frequency.

MD with time division. The user has the right to receive or transmit data only during a certain period of time.

MD code division. Each user is given a code. It is superimposed on the data so that the signals of different users do not mix even when transmitted on the same frequency.

In general, all of the above systems guarantee frequency reuse, which improves 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- This is a type of radio relay communication, which is based on the use of artificial earth satellites as repeaters. Communication takes place between stations located on the ground, which in turn are stationary and mobile. The technology allows you to transmit a radio signal to any distance, even the largest.

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

The beginning of such technology was laid by the English scientist Arthur Clark, who wrote the article "Extraterrestrial repeaters". The principle was that the antenna had to be brought to the maximum distance in Earth orbit, which would allow receiving signals from ground sources and transmitting 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 apparatus, which was launched into space in 1960. This marked the beginning of the further rapid development of international satellite communications.

Areas of application for 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 triumphantly supplanted home stationary ones), without video chats that help to 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, which serves to create a private channel);

mobile network;

Internet (with the help of this system most modern technologies work).

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;

networks for data transmission;

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 communication provides the following opportunities:

exchange information;

manage and coordinate air and sea vessels, as well as land transport;

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.

Novelties of 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 a market segment of satellite communications is unimaginable without communication with the terrestrial network system. Any changes in the network structure can fundamentally affect the quality of the satellites.

Satellite communication has the following latest innovations:

fiber-optic networks have led to the partial displacement of satellite backbones;

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

improvement of the power armament of space vehicles and their ability to transmit remote signals from points on the ground;

wide band satellites equipped with a repeater;

means with large frequency ranges;

development of orbits of average height.

All these innovative devices have led to the possibility of processing many signals in space through inter-beam switches.

Thanks to the latest image transfer mechanisms of video files, free online communication has become commonplace today.

Market segments of satellite communications of the Russian Federation

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

The first segment was founded thanks to 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 broadcasting devices. The satellites of the system are localized over the oceans for high-quality supply of 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.

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

In the third segment, satellites, small-format stations and their systems are invented and introduced into production, causing television and radio broadcasting, remote online communications. 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 in relation 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.

The signal from the RAT (Remote Administration Tool) network is divided into codes in CDMA (Code Division Multiple Access) channels and, by scanning, facilitates paging in cycles interconnected in a single RAT. With these areas it is advantageous to report places where there is no cellular signal reception.

Multi-mode terminals of wireless subscribers are able to improve the efficiency of inter-network switching, increase access to various services.

Modern equipment for receiving and transmitting satellite communications at the exhibition

Modern satellite communications serves as a wonderful way of transmitting information, but puts forward increased demands on the equipment.

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

Within the walls of Expocentre, a wide range of samples of various price categories is exhibited, so that anyone can find the best 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 area.

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Satellite repeaters

Orbits of satellite transponders

Reuse of frequencies. Coverage areas

Frequency bands

Modulation and noise-correcting coding

Multiple Access

Application of satellite communications

Backbone satellite communications

VSAT systems

Mobile satellite communication systems

Satellite Internet

Disadvantages of satellite communications

Weak noise immunity

Influence of the atmosphere

Absorption in the troposphere

Ionospheric effects

Propagation Delay

Influence of solar interference

see also

Notes

Links

Mobile satellite communications

Introduction

Figure 1 The structure of the satellite communication system on the example of the VSAT network of the State Enterprise "Cosmic" communication"

Figure 2. Orbits and coverage areas of the earth's surface on the example of the geostationary space constellation of the INMARSAT system

The main global mobile satellite communications operators known in Russia

News from global satellite operators

Mobile satellite operators in Russia. INMARSAT

Models of satellite portable terminals of the "INMARSAT-mini-M" type, available for sale in the Russian Federation

Figure 3.TT-3060A

Rice. 4. World Phone Hybrid

Mobile satellite operators in Russia. "Globalstar"

Models of satellite portable mobile terminals available on the Russian market that support Globalstar services

Rice. 5. Ericsson portable subscriber mobile terminal

Rice. 6. Portable subscriber mobile terminal Telit

Rice. 7. Qualcomm portable mobile subscriber terminal

Conclusion

History of satellite communications

Applications of satellite communications

How modern satellite communication equipment works

International satellite communications

Areas of application for international satellite communications

Possibilities of modern international satellite communications

Novelties of satellite communications of the Russian Federation

Market segments of satellite communications of the Russian Federation

Modern equipment for receiving and transmitting satellite communications at the exhibition

Satellite communications: principle of operation, coverage area, channel characteristics and tariff plans. modern satellites