Satellite communication network. Satellite connection

G. Karvovsky. Satellite connection. The main issues of the construction and operation of a satellite communication system. Part 1.

G. Karvovsky

The world of communication. Connect! No. 1, 2002

The signal transmitted on October 4, 1957 by the radio beacon of the first Soviet artificial Earth satellite and received by the radio stations of the world, marked not only the beginning of the space era, but also marked the direction in which the development of satellite communications went. Later were created satellite systems communications (CCC), which ensured the transmission and reception of programs of the Central Television and Radio Broadcasting practically throughout the entire territory of our country. Today satellite communications are an important component of the Interconnected Communications Network of Russia.

Satellite communication systems

The SCS itself consists of two basic components (segments): space and ground (Fig. 1).

Rice. one. Satellite communication system

Space component (segment) SSS includes ISS, launched into certain orbits, the ground segment includes a communication system control center (CUSS), earth stations (ES) located in the regions (regional stations - RS), and subscriber terminals (AT) of various modifications.

Deployment and maintenance of the CCC in a working state - difficult task, which is solved not only by the means of the communication system itself, but also by the rocket and space complex. This complex includes cosmodromes with launch sites for launching carrier rockets, as well as radio-technical command-measuring complexes (KIMS) that monitor the movement of ISS, control and correct the parameters of their orbits.

CCS can be classified according to such features as: system status, type of ISS orbits and system belonging to a particular radio service.

The status of the system depends on its purpose, the area served, the location and ownership of the earth stations. Depending on the status, CCC can be divided into international(global and regional), national and departmental.

By the type of orbits used, systems with ISS on geostationary orbit (GEO) and on non-geostationary orbit: elliptical(HEO), low-orbit(LEO) and medium-altitude(MEO). According to the Radio Regulations, CCCs can belong to one of three main services - fixed satellite service (FSS), movable satellite service (MSS) and broadcasting satellite service (RCC).

Space segment

Orbits

The choice of the ISS orbit parameters depends on the purpose, the required communication service area and some other factors. (table 1,).

Most beneficial for placement of ISS geostationary orbits(fig. 2).

Rice. 2. ISS orbits

Their main advantage is the possibility of continuous round-the-clock communication in the global service area. Geostationary satellites in this orbit, moving in the direction of the Earth's rotation with the same speed, remain stationary relative to the "sub-satellite" point on the equator. With an omnidirectional antenna, signals relayed from the ISS are received on the Earth's surface at any points that lie within the radio visibility angle. Three ISS, evenly placed in orbit, provide continuous communication practically throughout the entire territory of the Earth, with the exception of the polar zones (above 76.50 ° N and S) for 12-15 years (the orbital resource of modern geostationary spacecraft).

The disadvantage of relaying the radio signal through the ISS, located at a distance of 36 thousand km, is the signal delay. For radio and television broadcasting systems, a delay of 250 ms (in each direction) does not affect the quality of the signals. Radiotelephone communication systems are more sensitive to delays, and with a total delay (taking into account the processing and switching time in terrestrial networks) exceeding 600 ms, high communication quality is not ensured. All the more, the so-called "double" hop, when the communication channel provides for two satellite sections, is unacceptable in these systems.

The number of ISS that can be placed in a geostationary orbit is limited by the permissible angular orbital separation between adjacent satellites. The minimum angular separation is determined by the spatial selectivity of the onboard and ground antennas, as well as the accuracy of the spacecraft holding in orbit. It should be 1-3 ° by international standards. Consequently, no more than 360 ISS can be placed in a geostationary orbit.

Under the influence of a number of geophysical factors, the ISS "drifts" - its orbit is distorted, so it becomes necessary to correct it.

Elliptical orbits, on which the ISS are displayed, are selected so that the duration of the day is a multiple of the satellite's orbital period (Fig. 2). For ISS, synchronous elliptical orbits of certain types are used. (Table 2,).

Since the speed of the satellite at the apogee of the elliptical orbit is much less than at the perigee, the time spent by the ISS in the visibility zone increases as compared to the circular orbit. For example, ISS "Molniya", launched into orbit with parameters: apogee 40 thousand km, perigee 460 km, inclination 63.5 °, provides communication sessions lasting 8-10 hours. The orbital constellation (OG) of three satellites maintains global round-the-clock communication ...

To ensure continuous round-the-clock communication of the ISS in Borealis orbits, at least 8 spacecraft will be required (located in two orbital planes, four satellites in each plane).

When choosing elliptical orbits, account is taken of the influence of the inhomogeneities of the Earth's gravitational field, which leads to changes in the latitude of the sub-satellite point at the apogee, as well as the dangerous effects of stable belts of charged particles trapped by the Earth's magnetic field (Van Allen radiation belts), crossed by the ISS when moving in orbit.

A medium high-altitude orbit (MEO) ISS covers a smaller area than a geostationary ISS (Fig. 3). The duration of the stay of the ISS in the radio visibility zone of earth stations is 1.5-2 hours. Therefore, in order to provide communication for the most populated regions of the world and navigable water areas, it is necessary to create an OG of 8-12 satellites. When choosing an orbit for them, it is necessary to take into account the effects of the Van Allen radiation belts located in the equatorial plane. The first stable belt of high radiation begins at about 1.5 thousand km and extends up to several thousand kilometers, its "span" is about 300 km on both sides of the equator. The second belt of equally high intensity (10 thousand imp./s) is located at altitudes from 13 to 19 thousand km, covering about 500 km on both sides of the equator. Therefore, the ISS routes must pass between the first and second Van Allen belts, i.e., at an altitude of 5 to 15 thousand km.

Rice. 3. ISS Earth coverage areas in different orbits

The total signal delay during communication via medium-altitude satellites is no more than 130 ms, which makes it possible to use them for high-quality radiotelephone communication. The ICO, Spaceway NGSO, Rostelesat systems, in which the OG is created at approximately the same altitude (10352-10355 km) with similar orbital parameters, can serve as an example of a CCC in medium-altitude orbits.

Low circular orbits depending on the inclination of the orbital plane relative to the equatorial plane, they are divided into low equatorial (inclination 0 °, altitude 2000 km), polar (90 °, 700-1500 km) and inclined (700-1500 km) orbits (Fig. 4). Low-Earth Orbit (LEO) communication systems are subdivided into data transmission systems (little LEO), radiotelephone systems (big LEO) and broadband communication systems (mega LEO, sometimes the designation Super LEO).

ISS in these orbits are most often used to organize mobile and personal communications. The orbital period of the satellite in these orbits is from 90 minutes to 2 hours, the time spent by the ISS in the radio visibility zone does not exceed 10-15 minutes, the ISS communication area in these orbits is small, therefore, to ensure continuous communication, it is necessary that the OG includes at least 48 ISS ...

Artificial communication satellites

ISS is a spacecraft on which relay equipment is installed: transceivers and antennas operating at different frequencies. They receive signals from an earth transmitting station (ES), amplify them, carry out frequency conversion and retransmit the signals simultaneously to all ES located in the satellite's radio visibility zone. The satellite is also equipped with equipment for controlling its position, telemetry and power supply. The stability and orientation of the antenna is supported by the stabilization system. Satellite telemetry equipment is used to transmit information about the position of the ISS to the Earth and receive commands for position correction.

Retransmission of the received information can be carried out without storing and with storing, for example, until the ISS enters the zone of visibility of the AP.

Frequencies

The frequency ranges for the organization of satellite communications are allocated by the "Radio Regulations" taking into account the "radio transparency windows" of the earth's atmosphere, natural radio interference and a number of other factors (Table 3). The distribution of frequencies between radio communication services is strictly regulated and controlled by the state. There are internationally agreed rules for the use of allocated bands, which is necessary to ensure electronic compatibility of radio equipment operating in these or adjacent bands. A pair of frequencies is allocated to the ISS transceiver: the upper one for signal transmission from the ES to the satellite (upstreams), the lower one - from the satellite to the ES (downstreams).

Table 3. Frequency ranges for the organization of satellite communications

A satellite communication channel operating at the allocated receiving and transmitting frequencies occupies a certain frequency band (bandwidth), the width of which determines the amount of information transmitted over the channel per unit of time. A typical satellite transceiver operating at frequencies from 4 GHz to 6 GHz covers a bandwidth of 36 MHz. Is it a lot or a little? For example, to transmit a television signal in the digital MPEG-2 standard, a channel with a bandwidth of 6 MHz is required, for a telephone channel - 0.010 MHz. Therefore, with the help of such a transceiver, it is possible to organize 6 television or 3600 telephone channels. Usually, 12 or 24 transceivers are installed on the ISS (in some cases more), which results in 432 MHz or 864 MHz, respectively.

Ground segment

The satellite communications control center (TsUSS) monitors the state of the on-board ISS systems, plans work on the deployment and replenishment of the orbital constellation, calculates the radio visibility zones and coordinates the work of the SSS.

Earth stations

Earth stations SSS (ZS) transmit and receive radio signals on the "Earth - ISS" section, multiplex, modulate, signal processing and frequency conversion, organize access to ISS channels and terrestrial networks of subscriber terminals.

The communication time between the ES and the ISS is limited by the time the ISS is in the zone of its radio visibility (Fig. 5). This zone is determined by the length of the AB arc, which depends on the altitude of the satellite orbit and the minimum elevation angle of the ES antenna tracking the ISS while it is in the radio visibility zone.

Rice. 5. Radio visibility area

In the CCC, multifunctional transceiving, transmitting, receiving and control ES are used. These stations are equipped with radio transmitting equipment, receiving and transmitting antennas, as well as a tracking system providing communication with the ISS.

Multifunctional fixed stations have very high throughput. They are located at specially selected sites, usually outside the city limits in order to avoid mutual radio interference with terrestrial communication systems. These ESs are equipped with high-power radio transmitters (from several to ten or more kW), high-sensitivity radio receivers and transmit-receive antennas, which have a radiation pattern with a very narrow main lobe and very low side lobes. ES of this type are intended for servicing developed communication networks; that they can provide normal access to the ES, fiber-optic communication lines are required.

ES with an average throughput can be very diverse, and their specialization depends on the type of transmitted messages. ES of this type are serviced by corporate CCS, which most often support the transmission of video, voice and data, video conferencing, e-mail.

Some APs serving corporate CCCs include several thousand micro-terminals (VSATs - Very Small Aperture Terminal). All terminals are connected to one main ES (MES - Master Earth Station), forming a network that has a star topology and supports data reception / transmission, as well as the reception of audio and video information.

There are also STS-based CCSs that can receive one or more types of messages (data, audio and / or video information). The topology of such networks is also star-shaped.

The most important element of the network - the monitoring and diagnostics system, performs the following functions:

radio monitoring of satellite communication channels;

testing of satellite communication channels during repair and restoration work and maintenance of APs, during the deployment of APs and putting them into operation;

analysis of the functional state of the CVS, on the basis of which recommendations for the operating modes of the ES are developed.

Radio monitoring allows checking the correct use of the ISS frequency resource, tracking interference and detecting attempts of unauthorized access to satellite communication channels. In addition, the parameters of the ES radiation are monitored and the deterioration of the quality of satellite communication channels due to weather and climatic conditions is recorded.

From the history of CCC

The first artificial Earth satellite (AES), launched into near-earth orbit in October 1957, weighed 83.6 kg and had a beacon radio transmitter on board that transmitted signals that were used to control the flight. The results of this first launch and the first experiments in transmitting radio signals from space have clearly shown the possibility of organizing a communication system in which the satellite will act as an active or passive radio signal repeater. However, for this it is necessary to create satellites on which it is possible to install equipment of a sufficiently large mass, and to have powerful rocket systems capable of putting these satellites into near-earth orbit.

Such launch vehicles were created, and in a short time a large mass satellites were developed, capable of carrying complex scientific, research, special equipment, as well as communication equipment. The foundation was laid for the creation of satellite systems for various purposes: meteorological, navigation, reconnaissance, communications. The importance of these systems can hardly be overestimated. The satellite communication system takes the leading place among them.

Immediately after the launch of the first satellite, experiments began on the use of satellites in the country's communications system and a satellite communications system began to be created. Earth transceiver stations equipped with parabolic antennas with a mirror diameter of 12 m were built. On April 23, 1965, an artificial communications satellite (ISS) "Molniya" was launched into a high elliptical orbit.

A high elliptical orbit with an apogee of 40 thousand km, located above the northern hemisphere, and a twelve-hour orbital period made it possible for the ISS to provide relaying of the radio signal to almost the entire territory of the country twice a day for 9 hours. The first practically significant result was obtained in 1965, when the exchange of television programs between Moscow and Vladivostok was carried out through the ISS. In October 1967, the world's first satellite communications system "Orbit" was put into operation.

In 1975, the Raduga ISS was launched into a circular equatorial, or geostationary, orbit with an altitude of 35786 km with a period of revolution around the Earth equal to 24 hours. The direction of rotation of the satellite coincided with the direction of rotation of our planet, it remained motionless in the sky and was, as it were, "suspended" above the surface of the Earth. This provided constant communication through such a satellite and made it easier to track it. Subsequently, the ISS "Horizon" was launched into geostationary orbit.

Operating experience of the Orbita SCS has shown that further development systems associated with the construction of earth stations of this type to serve cities and towns with a population of several thousand people is not economically justified. In 1976, a more economical satellite communication system "Ekran" was created, the ISS of which was launched into geostationary orbit. Simpler and more compact terrestrial transceiver stations of this system were installed in small settlements, villages, at meteorological stations located in Siberia, regions of the Far North, partly the Far East, and brought the programs of the Central Television to their population.

In 1980, the operation of the Moskva SCS began, the earth stations of which operated through the Gorizont ISS. The earth transmitting stations of this SSS were similar to the SSS stations "Orbita" and "Ekran", but it had small-sized earth receiving stations, which made it possible to place them at communication centers, on low-power repeaters and in printing houses. The radio signal received by the terrestrial receiving station was transmitted to a low-power television repeater, with the help of which the television program was delivered to the subscribers. CCC "Moscow" made it possible to transmit programs of the Central Television and pages of central newspapers to the most remote corners of the country and to Soviet institutions of practically all European, North American and border Asian countries.

Satellite communication - today

At present, an orbital constellation is used in the federal civil satellite communications system, which includes 12 state spacecraft (SC) operated by the State Enterprise "Space Communications". The orbital constellation includes two spacecraft of the Express series launched in 1994 and 1996, seven spacecraft of the Gorizont series developed in the 1970s, one of the Ekran-M series, and two new modern satellites of the Express-A series. In addition to these ISS, ISS of the Yamal-100 type (operator - OAO Gazkom), Bonum-1 and some others are in orbit. The production of new generation spacecraft (Express-AM, Yamal-200) is underway. There are about 65 satellite communication companies operating in Russia, which is about 7% of the total number of telecommunication operators. These companies provide their clients with a wide range of telecommunication services: from renting digital channels and paths to the provision of telephony services, television and radio broadcasting, multimedia.

Today, CCS have become an important component of the Interconnected Communication Network of Russia (BCC). The "Program of emergency measures for state support for the preservation, replenishment and development of Russian satellite communication and broadcasting systems for state purposes" (Decree of the Government of the Russian Federation of February 1, 2000 No. 87) and "Federal Space Program of Russia for 2001-2005 have been developed and are being implemented. "(Resolution of the Government of the Russian Federation of March 30, 2000 No. 288).

Directions for the development of CCC

The development of satellite communications for civilian purposes is addressed at the governmental, interdepartmental (GKRCH) and departmental (Ministry of Communications and Informatization of the Russian Federation, Rosaviakosmos, etc.) levels. Russian satellite communication systems are under the jurisdiction of the state and are operated by domestic state (GP KS) or private commercial operators.

In accordance with the adopted concept for the development of VSS in Russia, a prospective VSS should include three subsystems:

fixed satellite communications for servicing the Interconnected communications network of Russia, as well as overlaid and corporate networks;

satellite television and radio broadcasting, including direct broadcasting, which is a new stage in the development of modern electronic media;

mobile personal satellite communications in the interests of mobile and remote subscribers in Russia and abroad.

Fixed satellite communications

The fixed-satellite service is a radiocommunication service between earth stations at a given location (a fixed point located in certain areas).

The main directions of using fixed communications:

organization of backbone, intra-zone and local communication lines as part of the Armed Forces of Russia;<

providing a resource for creating data transmission networks;

development of corporate communication and data transmission networks using modern VSAT technologies, including Internet access;

development of the international communication network;

distribution of federal, regional, local and commercial television and radio programs throughout the country;

development of transmission networks for central newspapers and magazines;

redundancy of the backbone primary network of the VSS of Russia.

The system of fixed satellite communications in the coming years will be based on the operating satellites "Gorizont", the new satellites "Express-A", "Yamal-100" and the satellite LMI-1 of the international organization "Intersputnik". Later, new satellites "Express K" and "Yamal 200/300" will be put into operation.

Satellite communication networks will play a major role in the modernization of communication systems in the north-eastern regions of Russia.

The "General Scheme of the Satellite Component of the Primary Network of the Russian Armed Forces", developed by OJSC Giprosvyaz by order of OJSC Rostelecom and the State Enterprise "Space Communications", defines the procedure for using satellite systems for the Armed Forces of Russia.

It is envisaged that the development of corporate networks will be carried out mainly on the basis of Russian satellites in accordance with the priorities determined by the Decree of the Government of the Russian Federation No. 1016 of 09/02/98.

The modernized digital TV broadcasting system "Moscow" / "Moscow Global" should become the basis for the transmission of television programs using the satellite fixed service. This will make it possible to transmit socially significant state and all-Russian television programs (RTR, "Kultura", ORT) to all zone broadcasting zones, with three satellites instead of the current ten.

Broadcast service

The broadcasting service is based on direct television broadcasting satellites, such as ISS "Bonum-1", which is placed at 36 ° E. and provides transmission of more than two dozen television programs in the European part of Russia.

Further expansion of the satellite TV broadcasting system (with the possibility of broadcasting up to 40-50 commercial TV programs) is envisaged to create a TV distribution network in the sparsely populated eastern regions of Russia, as well as to meet the needs for regional TV programs. This CCS will provide such new services as digital high-definition TV, Internet access, etc. In the future, it can completely replace the existing satellite TV distribution system based on the use of the fixed satellite service.

Mobile satellite communications

The Russian mobile satellite communication system is deployed on the basis of the Horizont satellites and is used to organize government communications and in the interests of Morsvyaz-Sputnik State Enterprise. The systems "Inmarsat" and "Eutelsat" (subsystems "Evteltraks") can also be used.

In accordance with the Decree of the Government of the Russian Federation of September 2, 1998, No. 1016, during the implementation of projects of promising satellites, measures should be taken to preserve the mobile satellite communications network in the amount necessary to maintain the system of government and presidential communications.

Personal mobile communication system

In our country, several mobile personal satellite communications projects are being developed (Rostelesat, Signal, Molniya Zond).

Russian enterprises are involved in several international personal satellite communications projects (Iridium, Globalstar, ICO, etc.). At present, specific conditions are being worked out for the use of mobile communication systems in the territory of the Russian Federation and their interfacing with the Air Force of Russia. The following are involved in the development and creation of SSS complexes: State operator SE "Space Communications", Krasnoyarsk NPO / PM named after Reshetnev and Alcatel (creation of three new-generation "Express A" satellites), NIIR, TsNIIS, Giprosvyaz LLC, GSP RTV, Rostelecom OJSC, etc.

Conclusion

Satellite communication and data transmission systems are able to provide the necessary speed of deployment and reconfiguration of the system, reliability and quality of communication, independence of tariffs from distance. Almost all types of information are transmitted via satellite channels with a high availability factor.

Today, satellite communication systems have become an integral part of the world's telecommunication backbones, linking countries and continents. They are successfully used in many countries of the world and have taken their rightful place in the Interconnected communication network of Russia.

Literature

Timofeev V. V. About the concept of development of satellite communications in Russia. - "Bulletin of communications", 1999, No. 12.

Vasily Pavlov (Head of the Department of Radio, Television and Satellite Communications of the Ministry of Communications of the Russian Federation). From a speech at a meeting on the Russian CCS and its role in meeting the needs of departmental and corporate operators. - "Networks", 2000, No. 6.

Durev V.G., Zenevich F.O., Kruk B.I. et al. Telecommunications. Introduction to the specialty. - M., 1988.

Radio regulations for radio communications of the Russian Federation. Official edition. Approved and put into effect from 01.01.1999 by the decision of the State Committee for Radio Frequencies of 09.28.1998. 1999.

Leonid Nevdyaev. Satellite systems Part 1. Orbits and parameters. - "Networks", 1999, №1-2.

Engineering handbook of space technology. - M., 1977.

MOU Parabel Gymnasium

abstract

Satellite communication systems

Completed

Goroshkina Ksenia

11th grade student

Checked

Borisov Alexander Vladimirovich

Parabel

2010 year

Introduction 3

1. Principles of organizing satellite communication channels 4

2. Orbits of communication satellites 5

3. Typical scheme of the organization of satellite communication services 6

4. Fields of application of satellite communications 6

4.1. VSAT satellite communication principles 7

4.2. Principles of organizing mobile satellite communications 7

5. Technologies used in satellite communications 8

6. History of creation of satellite communication systems 11

6.1. The first satellite communication and broadcasting lines through the "Molniya-1" satellites 12

6.2. The world's first satellite system "Orbita" for the distribution of TV programs 13

6.3. The world's first direct TV broadcasting system Ekran 14

6.4. TV program distribution systems "Moscow" and "Moscow-Global 15

6.5. Satellite TV broadcasting system in the 12 GHz range 16

6.6. Creation of the Intersputnik system 16

6.7. Creation of a satellite link for government communications 17

6.8. In conclusion ... 17

List of used literature 20

Introduction

Satellite communication systems (SSS) have been known for a long time, and are used to transmit various signals over long distances. Since its inception, satellite communications have developed rapidly, and with the accumulation of experience, the improvement of equipment, the development of signal transmission methods, there has been a transition from individual satellite communication lines to local and global systems.

Such rates of development of CCS are explained by a number of advantages that they possess. These include, in particular, high bandwidth, unlimited overlapping spaces, high quality and reliability of communication channels. These advantages, which determine the broad possibilities of satellite communications, make it a unique and effective means of communication. Satellite communications are currently the main form of international and national communications over long and medium distances. The use of artificial earth satellites for communication continues to expand as existing communication networks develop. Many countries are setting up their own national satellite communications networks.

A unified automated communication system is being created in our country. For this, various technical means of communication are developing, improving and finding new areas of application.

In my essay, I will consider the principles of the organization of satellite systems, the scope, the history of the creation of the CCS. Nowadays, much attention is paid to satellite broadcasting, so we must know how the system works.

1. Principles of organizing satellite communication channels

Satellite communication is one of the types of radio communication based on the use of artificial earth satellites as repeaters.

Satellite communication is carried out between earth stations, which can be both fixed and mobile. Satellite communication is a development of traditional radio relay communication by placing a repeater at a very high altitude (from hundreds to tens of thousands of kilometers). Since the zone of its visibility in this case is almost half of the Earth, there is no need for a chain of repeaters. For transmission via satellite, the signal must be modulated. Modulation is performed at the earth station. The modulated signal is amplified, transferred to the desired frequency and fed to the transmitting antenna.

In the early years of research, passive satellite repeaters were used, which were a simple reflector of a radio signal (often a metal or polymer sphere with a metal coating), which did not carry any transmitting and receiving equipment on board. Such satellites have not become widespread. All modern communications satellites are active. Active repeaters are equipped with electronic equipment for signal reception, processing, amplification and retransmission. 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. The satellite can use several independent channels performing these operations, each of which works with a certain part of the spectrum (these processing channels are called transponders).

The regenerative satellite demodulates the received signal and re-modulates it. As a result, 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.

2. Orbits of communication satellites

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

1 - equatorial, 2 - oblique, 3 - polar

An important type of equatorial orbit is geostationary orbit, on which the satellite rotates with an angular velocity equal to the angular velocity of the Earth, in the direction coinciding with the direction of rotation of the Earth. The obvious advantage of 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 launch all satellites into it. Its other disadvantage is its high altitude, and hence the higher cost of launching a satellite into orbit. In addition, a satellite in geostationary orbit is unable to serve earth stations in the circumpolar region.

Inclined orbit allows you to solve 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- the limiting case of oblique.

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

3. Typical scheme of the organization of satellite communication services

the satellite segment operator creates a communications satellite at its own expense, placing an order for the manufacture of a satellite with one of the satellite manufacturers, and carries out its launch and maintenance. After the satellite is put into orbit, the satellite segment operator begins to provide services for leasing the frequency resource of the relay satellite to the satellite communication service companies.

a satellite communications service operator concludes an agreement with a satellite segment operator for the use (lease) of capacities on a communications satellite, using it as a repeater with a large service area. An operator of satellite communications services builds the terrestrial infrastructure of its network on a specific technological platform produced by the companies that manufacture ground equipment for satellite communications.

4. Spheres of application of satellite communications:

Backbone satellite communications: Initially, the emergence of satellite communications was dictated by the need for the transmission of large amounts of information. Over time, the share of voice transmission in the total volume of backbone traffic has been steadily decreasing, giving way to data transmission. With the development of fiber-optic networks, the latter began to displace satellite communications from the backbone market.

VSAT systems: VSAT (Very Small Aperture Terminal) systems provide satellite communication services to customers (usually small organizations) that do not require high bandwidth. The data transfer rate for a VSAT terminal usually does not exceed 2048 kbps. The words "very small aperture" refer to the size of the terminal antennas relative to the size of the older backbone antennas. VSATs operating in the C-band usually use antennas with a diameter of 1.8-2.4 m, in the Ku-band - 0.75-1.8 m. VSAT systems use on-demand channel technology.

Mobile satellite communication systems: A feature of most mobile satellite systems is the small size of the terminal antenna, which makes signal reception difficult.

4.1. The principles of organizing satellite communication VSAT:

The main element of the satellite VSAT network is the NCC. It is the Network Control Center that provides access to client equipment from the Internet, public telephone network, other terminals of the VSAT network, and implements traffic exchange within the client's corporate network. The NCC has a broadband connection to backbone communication channels provided by backbone operators and provides information transfer from a remote VSAT terminal to the outside world.

4.2. Principles of organizing mobile satellite communications:

In order for the signal strength reaching the mobile satellite receiver to be sufficient, one of two solutions is used:

The satellites are located in geostationary orbit. Since this orbit is at a distance of 35,786 km from the Earth, a powerful transmitter must be installed on the satellite.
Many satellites are located in inclined 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 ground switches.

The client's equipment (mobile satellite terminals, satellite phones) interacts with the outside world or with each other through a relay satellite and interface stations of a mobile satellite service operator, which provide connection to external terrestrial communication channels (public telephone network, Internet, etc.)

5. Technologies used in satellite communications

M multiple use of frequencies in satellite communications. Since radio frequencies are a limited resource, it is necessary to ensure that the same frequencies can be used by different earth stations. This can be done in two ways:

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

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

H frequency ranges.

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

Range name	Frequencies	Application
		Mobile satellite communications
		Mobile satellite communications
	4 GHz, 6 GHz	Fixed satellite communications
	Frequencies are not defined for satellite communications in this range. For radar applications, the specified range is 8-12 GHz.	Fixed satellite communications (for military purposes)
	11 GHz, 12 GHz, 14 GHz
		Fixed satellite communications, satellite broadcasting
		Fixed satellite communications, inter-satellite communications

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

M modulation and error-correcting coding

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

considerable remoteness of the receiver from the transmitter,
limited satellite power

Satellite communications are poorly suited to transmitting analog signals. Therefore, to transmit speech, it is pre-digitized using pulse-code modulation.
To transmit digital data over a satellite communication channel, they must first be converted into a radio signal occupying a certain frequency range. For this, modulation is used (digital modulation is also called keying).

Due to the low signal power, there is a need for error correction systems. For this, various error-correcting coding schemes are used, most often various versions of convolutional codes, as well as turbo codes.

6. The history of the creation of satellite communication systems

The idea of creating global satellite communication systems on Earth was put forward in 1945. Arthur Clarke, who later became a famous science fiction writer. The implementation of this idea became possible only 12 years after ballistic missiles appeared, with the help of which October 4, 1957 the first artificial Earth satellite (AES) was launched into orbit. To control the flight of the satellite, a small radio transmitter was placed on it - a beacon operating in the range 27 MHz... After few years April 12, 1961... for the first time in the world on the Soviet spacecraft "Vostok" Yu.A. Gagarin made a historical flight around the Earth. At the same time, the cosmonaut had regular radio communication with the Earth. This is how systematic work began on the study and use of outer space for solving various peaceful tasks.

The creation of space technology has made it possible to develop very effective systems for long-distance radio communication and broadcasting. In the United States, intensive work began on the creation of communication satellites. Such works began to unfold in our country. Its vast territory and poor communication development, especially in the sparsely populated eastern regions, where the creation of communication networks using other technical means (radio relay links, cable lines, etc.) is associated with high costs, made this new type of communication very promising.

At the origins of the creation of domestic satellite radio systems were outstanding domestic scientists and engineers who headed large scientific centers: M.F. Reshetnev, M.R. Kaplanov, N.I. Kalashnikov, L. Ya. Cantor

The main tasks assigned to scientists were as follows:

Development of satellite repeaters for television broadcasting and communications (Ekran, Raduga, Gals), since 1969 satellite repeaters have been developed in a separate laboratory headed by M.V. Brodsky ;

Creation of system projects for the construction of satellite communications and broadcasting;

Development of equipment for satellite communication earth stations (ES): modulators, threshold-lowering demodulators of FM (frequency modulation) signals, receiving and transmitting devices, etc .;

Comprehensive work on equipping satellite communication and broadcasting stations with equipment;

Development of the theory of tracking FM demodulators with a reduced noise threshold, multiple access methods, modulation methods and error-correcting coding;

Development of normative and technical documentation for channels, paths of television and communication equipment of satellite systems;

Development of control and monitoring systems for AP and satellite communication and broadcasting networks.

NIIR specialists many national satellite communication and broadcasting systems were created, which are still in operation... The transmitting and receiving ground and airborne equipment of these systems was also developed at NIIR. In addition to the equipment, the specialists of the institute proposed design methods for both the satellite systems themselves and the individual devices included in their composition. The experience of designing satellite communication systems of NIIR specialists is reflected in numerous scientific publications and monographs.

6.1. The first satellite communication and broadcasting lines through the "Molniya-1" satellites

The first experiments on satellite communications by reflecting radio waves from the American reflecting satellite "Echo" and the Moon, used as passive repeaters, were carried out by NIIR specialists in 1964... The radio telescope at the observatory in the village of Zimenki, Gorky Region, received telegraph messages and a simple drawing from the British Jodrell Bank Observatory.

This experiment proved the possibility of the successful use of space objects for organizing communications on Earth.

Several system projects were prepared in the satellite communications laboratory, and then she took part in the development of the first domestic satellite communications system "Molniya-1" in frequency range below 1 GHz. The head organization for the creation of this system was the Moscow Research Institute of Radio Communication (MNIIRS). The chief designer of the Molniya-1 system is M.R. Kaplanov- Deputy Head of MNIIRS.

In the 60s, NIIR was developing a transceiver complex for the Gorizont tropospheric radio relay system, which also operates in the frequency range below 1 GHz. This complex was modified and the created equipment, named "Gorizont-K", was used to equip the first satellite communication line "Molniya-1", which connected Moscow and Vladivostok. This line was intended for the transmission of a TV program or group spectrum of 60 telephone channels. With the participation of NIIR specialists, two earth stations (ES) were equipped in these cities. MNIIRS developed an onboard repeater of the first artificial communications satellite "Molniya-1", which was successfully launched April 23, 1965... It was launched into a highly elliptical orbit with an orbital period of 12 hours. Such an orbit was convenient for servicing the territory of the USSR located in northern latitudes, since for eight hours at each orbit the satellite was visible from any point of the country. In addition, launching into such an orbit from our territory is carried out with less energy consumption than into a geostationary one. The orbit of the "Molniya-1" satellite has retained its significance to this day and is used, despite the prevailing development of geostationary satellites.

6.2. The world's first satellite system "Orbit" for the distribution of TV programs

After the completion of research on the technical capabilities of the "Molniya-1" satellites by the specialists of NIIR N.V. Talyzin and L. Ya. Cantor it was proposed to solve the problem of supplying TV programs of central television to the eastern regions of the country by creating the world's first satellite broadcasting system "Orbit" in in the range of 1 GHz on the basis of the "Horizon-K" equipment.

In 1965-1967. In a record short time, in the eastern regions of our country, 20 earth stations "Orbit" and a new central transmitting station "Reserve" were simultaneously built and put into operation. The Orbita system has become the world's first circular, television, distribution satellite system in which the capabilities of satellite communications are most effectively used.

It should be noted that the range in which the new Orbit system operated at 800-1000 MHz was not in line with that allocated under the Radio Regulations for the fixed-satellite service. The work on transferring the Orbita system to the 6/4 GHz C-band was carried out by NIIR specialists in the period 1970-1972. The station operating in the new frequency range was named "Orbit-2". A full set of equipment was created for it for operation in the international frequency range - on the Earth-Space section - in the 6 GHz range, on the Cosmos-Earth section - in the 4 GHz range. Under the direction of V.M. Tsirlina a system for pointing and tracking antennas with a software device was developed. This system used an extreme automaton and a conical scan method.

Station "Orbit-2" began to be implemented since 1972., a by the end of 1986... about 100 of them were built. Many of them are still operating transceiving stations.

Later, for the operation of the Orbit-2 network, the first Soviet geostationary satellite "Raduga" was created and launched into orbit; I. Ostrovsky, Yu.M. Fomin, etc.) At the same time, manufacturing technology and methods of ground processing of space products were created and mastered.

For the Orbit-2 system, new Gradient transmitting devices were developed (I.E. Mach, M.Z. Zeitlin, etc.), as well as parametric amplifiers (A.V. Sokolov, E.L. Ratbil, BC Sanin, V.M. Krylov) and signal receiving devices (V.I.Dyachkov, V.M.Dorofeev, Yu.A. Afanasyev, V.A.Polukhin, etc.).

6.3. The world's first direct TV broadcasting system "Ekran"

The widespread development of the Orbita system as a means of supplying TV programs in the late 70s became economically unjustified due to the high cost of the AP, which makes it inexpedient to install it in a point with a population of less than 100-200 thousand people. The Ekran system turned out to be more effective, operating in the frequency range below 1 GHz and having a high power of the onboard repeater transmitter (up to 300 W). The purpose of creating this system was to cover sparsely populated areas with TV broadcasting in the regions of Siberia, the Far North and part of the Far East. For its implementation, the frequencies 714 and 754 MHz were allocated, at which it was possible to create fairly simple and cheap receiving devices. The Ekran system became, in fact, the world's first direct satellite broadcasting system.

Receiving installations of this system had to be cost-effective both for servicing small settlements and for individual reception of TV programs.

The first satellite of the Ekran system was launched October 26, 1976 . into geostationary orbit at 99 ° E A little later in Krasnoyarsk, collective reception stations "Ekran-KR-1" and "Ekran-KR-10" were released with a power of the output television transmitter of 1 and 10 watts. The earth station transmitting signals to the Ekran satellites had an antenna with a mirror diameter of 12 m, it was equipped with a 5 kW Gradient transmitter operating in the 6 GHz band. The receiving installations of this system, developed by NIIR specialists, were the simplest and cheapest receiving stations of all those implemented in those years. By the end of 1987, the number of installed Ekran stations reached 4,500.

6.4. TV program distribution systems "Moscow" and "Moscow-Global"

Further progress in the development of satellite TV broadcasting systems in our country is associated with the creation of the Moskva system, in which the technically obsolete ES of the Orbita system were replaced by small ESs. Development of small ESs began in 1974 on the initiative N.V. Talyzin and L. Ya. Cantor.

For the "Moskva" system on the "Horizon" satellites, an increased power barrel was provided, operating in the 4 GHz band to a narrow-beam antenna. The energy ratios in the system were chosen in such a way that they ensured the use of a small parabolic antenna with a mirror diameter of 2.5 m at the receiving ES without automatic guidance. A fundamental feature of the "Moscow" system was the strict observance of the norms for the spectral power flux density at the Earth's surface, established by the Regulations for the sake of communications for systems of the fixed service... This made it possible to use this system for TV broadcasting throughout the USSR. The system provided high quality reception of the central TV and radio programs. Subsequently, another channel was created in the system, intended for the transmission of newspaper pages.

These stations have also become widespread in domestic institutions located abroad (in Europe, in northern Africa and a number of other territories), which made it possible for our citizens abroad to accept domestic programs. When creating the "Moscow" system, a number of inventions and original solutions were used, which made it possible to improve both the construction of the system itself and its hardware complexes. This system served as a prototype for many satellite systems, created later in the United States and Western Europe, in which medium-power satellites operating in the fixed-satellite service band were used to deliver TV programs to small-sized and moderate-cost ESs.

During 1986-1988. the development of a special system "Moscow-Global" with small APs was carried out, intended for supplying central TV programs to domestic representative offices abroad, as well as for transmitting a small amount of discrete information. This system is also in operation. It provides for the organization of one TV channel, three channels for the transmission of discrete information at a rate of 4800 bit / s and two channels at a rate of 2400 bit / s. Discrete information channels were used in the interests of the Committee on Television and Radio Broadcasting, TASS and APN (Political News Agency). To cover almost the entire territory of the globe, it uses two satellites located in geostationary orbit at 11 ° W. and 96 ° E. Receiving stations have a mirror with a diameter of 4 m, the equipment can be located both in a special container and indoors.

6.5. Satellite TV broadcasting system in the 12 GHz range

Since 1976... at NIIR, work began on the creation of a fundamentally new satellite television system in those years in the 12 GHz frequency range (STV-12) allocated for such satellite TV broadcasting, which would not have the restrictions on the radiated power inherent in Ekran systems and Moscow could provide coverage of the entire territory of our country with multi-program TV broadcasting, as well as the exchange of programs and the solution of the problem of republican broadcasting. In the creation of this system, NIIR was the parent organization.

The specialists of the institute carried out studies that determined the optimal parameters of this system, and developed multi-barreled onboard repeaters and equipment for the transmitting and receiving ES. At the first stage of the development of this system, the domestic satellite "Gals" was used, the signals were transmitted in analog form, imported receiving equipment was used. Later, a transition was made to digital equipment based on a foreign satellite, as well as transmitting and receiving equipment.

6.6. Creation of the Intersputnik system

In 1967 g. the development of international cooperation of the socialist countries in the field of satellite communications began. Its purpose was to create international satellite system "Intersputnik", designed to meet the needs of Bulgaria, Hungary, Germany, Mongolia, Poland, Romania, the USSR and Czechoslovakia in telephone communications, data transmission and exchange of TV programs ... In 1969 g. the project of this system was developed, the legal basis of the organization "Intersputnik", and in 1971 an agreement on its creation was signed.

The Intersputnik system has become the world's second international satellite communications system (after Intelsat). NIIR specialists have developed projects of the ZS, which with the assistance of the USSR were built in many countries of the socialist community. The first air station abroad was created in Cuba, and the second in Czechoslovakia. In total, NIIR has supplied more than ten air stations abroad for receiving TV, air and special-purpose programs.

Initially, Intersputnik used the Molniya-3 satellites in a highly elliptical orbit, and since 1978, two multilateral geostationary satellites of the Horizon type with station points at 14 ° W. and 53 ° (and then 80 °) east longitude. Initially, the ZS was equipped with the Gradient-K transmitter and the Orbit-2 receiving complex.

All system and technical solutions for the creation of the Intersputnik system, as well as the AP hardware were created by NIIR specialists together with the NIIR Promsvyazradio pilot plant and co-executing organizations. The Intersputnik system is still in operation today, leasing the trunks of the Russian space constellation, as well as using its geostationary satellite LMI-1, located at 75 ° E. The work was carried out in cooperation with the Iskra Production Association (Krasnoyarsk), the Moscow and Podolsk radio engineering plants.

The work supervisor was S.V. Borodich .

6.7. Creation of a satellite link for government communications

In 1972... an intergovernmental agreement was concluded between the USSR and the United States on the creation of a direct line of government communication (LPS) between the heads of state in case of emergency. The implementation of this important government agreement was entrusted to NIIR specialists. The chief designer of the LPS development was V.L. Bykov, and the responsible executors - I.A. Yastrebtsov, A.N. Vorobiev.

On the territory of the USSR, two ZS were created: one (in Dubna near Moscow), the second (in Zolochev near Lvov). The LPS was put into operation in 1975... It operates through the ZS "Dubna" to date. This was the first experience in the creation of a satellite line by domestic specialists in the Intelsat international system.

6.8. In custody…

In 1960-1980. NIIR specialists were solving very important for our state and technically complex problems of creating national satellite communication and broadcasting systems.

· Were created systems for the distribution of TV programs on the vast territory of our country, including direct satellite TV broadcasting. Many systems created at NIIR were the first in the world: Orbit, Ekran, Moskva, etc. The equipment of the ground part of these systems, as well as onboard equipment, was also developed by NIIR, it was produced by the domestic industry.

· Satellite communication and broadcasting systems made it possible to meet the needs of tens of millions of citizens of our country, especially those who lived in sparsely populated regions of Western Siberia and the Far East. With the creation of satellite systems in these regions, citizens for the first time had the opportunity to receive central television programs in real time.

· The introduction of satellite systems was extremely important for the economic and social development of both remote regions of Siberia and the Far East, and the entire country.

· The population of Sakhalin, Kamchatka, Khabarovsk Territory and many other remote areas gained access to the public telephone network.

· Scientists of NIIR carried out original research aimed at creating methods for calculating various kinds of devices used in satellite communication systems. They also created methodologies for designing satellite communication systems and wrote a number of fundamental monographs and scientific articles on satellite communication problems.

Conclusion

Modern organizations are characterized by a large volume of various information, mainly electronic and telecommunications, which passes through them every day. Therefore, it is important to have high quality output to the switching nodes that provide access to all important communication lines. In Russia, where the distances between settlements are enormous, and the quality of land lines is poor, the optimal solution to this issue is the use of satellite communication systems (SSS).

Initially, CCCs were used to transmit a TV signal. Our country is characterized by a vast territory that needs to be covered by means of communication. It became easier to do this after the advent of satellite communications, namely the Orbit-2 system. Later, satellite phones appeared, the main advantage of which is independence from the presence of any local telephone networks. High-quality telephone communication is available from almost anywhere in the world.

Within the framework of the presidential program "Universal Communication Service", payphones were installed in each settlement, and satellite payphones were used in particularly remote areas.

According to the federal target program "Development of TV and Radio Broadcasting in the Russian Federation for 2009-2015", digital broadcasting is being introduced in Russia. The program is fully funded, including the funds will go to the creation of multifunctional satellites.

Bibliography

1. Internet resource "History of satellite communications" http://sviazist.nnov.ru/modules/myarticles/article.php?storyid=1026

2. Internet resource "Principles of organizing satellite communications" http://vsatinfo.ru/index.php?option=com_sobi2&catid=30&Itemid=0

3. Internet resource "Free Encyclopedia"

http://ru.wikipedia.org

Review

for the abstract "Satellite communication systems"

Pupils 11 grades MOU Parabel Gymnasium

Goroshkina Xenia

The topic of the abstract is fully disclosed. The material in all sections is interesting, presented in an accessible and clear manner. Nice illustrations. The structure of the abstract is followed. The work can be used as a teaching aid for students.

Rating "EXCELLENT"

Expert: Borisov A.V. physics teacher

Engineers work on the world's first commercial communications satellite Early Bird

By today's standards, the Early Bird satellite ( INTELSAT I) had more than modest capabilities: with a bandwidth of 50 MHz, it could provide up to 240 telephone communication channels. At any given time, communication could be carried out between an earth station in the United States and only one of three earth stations in Europe (in the UK, France or Germany), which were interconnected by cable communication lines.

Later, the technology stepped forward, and the satellite INTELSAT IX already had a bandwidth of 3456 MHz.

For a long time in the USSR, satellite communications were developed only in the interests of the USSR Ministry of Defense. Due to the greater secrecy of the space program, the development of satellite communications in the socialist countries proceeded differently than in the Western countries. The development of civil satellite communications began with an agreement between 9 countries of the socialist bloc on the creation of the Intersputnik communications system, which was signed only in 1971.

Satellite repeaters

Passive communication satellite Echo-2. The metallized inflatable sphere served as a passive repeater

In the early years of research, passive satellite repeaters were used (examples are the Echo and Echo-2 satellites), which were a simple radio signal reflector (often a metal or polymer sphere with metal sputtering) that did not carry any transmitting and receiving equipment on board. ... Such satellites have not become widespread. All modern communications satellites are active. Active repeaters are equipped with electronic equipment for signal reception, processing, amplification and retransmission. 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. The satellite can use several independent channels performing these operations, each of which works with a certain part of the spectrum (these processing channels are called transponders).

Satellite repeater orbits

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

equatorial,
inclined,
polar.

An important variety equatorial orbit is a geostationary orbit in which a satellite rotates with an angular velocity equal to the angular velocity of the Earth, in a direction that coincides with the direction of rotation of the Earth. The obvious advantage of 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 launch all satellites into it. Its other disadvantage is its high altitude, and hence the higher 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.

Polar orbit- the limiting case of oblique (with an inclination of 90º).

Frequency reuse. 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. This can be done in two ways:

spatial separation- 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 used twice (for each of the planes).

A typical geostationary satellite coverage map includes the following components:

global beam- communicates with earth stations throughout the entire 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 the A plane, and the same frequency range is used in the western and eastern hemispheres.

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

In this case, all frequencies (except for 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 TV (Ku-band)

Satellite dish for C-band

Frequencies used in satellite communications are divided into ranges, indicated by letters. Unfortunately, in different literature, the exact boundaries of the ranges may not coincide. Guide values are given in ITU Recommendation V.431-6:

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	Frequencies are not defined for satellite communications by ITU-R recommendations. For radar applications, the specified range is 8-12 GHz.	Fixed satellite communications (for military purposes)
Ku	11 GHz, 12 GHz, 14 GHz
K	20 GHz	Fixed satellite communications, 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 in this band have a significant impact on the transmission quality.

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

Modulation and Anti-Noise Coding

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

considerable remoteness of the receiver from the transmitter,
limited satellite power (inability to transmit at high power).

As a result, satellite communications are poorly 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. For this, modulation is applied (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.

Modulation is performed at the earth station. The modulated signal is amplified, transferred to the desired frequency and fed to the transmitting antenna. The satellite receives the signal, amplifies, sometimes regenerates, transfers it to another frequency and, using a certain transmitting antenna, transmits it to the ground.

Multiple access

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

Frequency Division Multiple Access - giving each user a separate frequency range.

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 are 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 at the same frequencies.

In addition, many users do not require constant access to satellite communications. These users are assigned a communication channel (timeslot) on demand using DAMA (Demand Assigned Multiple Access) technology.

Satellite communication applications

Backbone satellite communications

Initially, the emergence of satellite communications was dictated by the need for the transmission of 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 steadily decreasing, giving way to data transmission.

With the development of fiber-optic networks, the latter began to displace satellite communications from the backbone market.

VSAT systems

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

VSAT systems use on-demand channel technology.

Mobile satellite communication systems

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

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 ground switches. A similar method is used by operators Iridium and Globalstar.

Mobile operators compete with personal satellite operators. Characteristically, both Globalstar and Iridium experienced serious financial difficulties, which brought Iridium to reorganization 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 is used in the organization of the "last mile" (communication channel between the Internet provider and the client), especially in places with poorly developed infrastructure.

The features of this type of access are:

Separation of incoming and outgoing traffic and attracting additional technologies to combine them. Therefore, such compounds are called asymmetrical.
Simultaneous use of the incoming satellite channel by several (for example 200) users: data is simultaneously transmitted through the satellite for all clients "interspersed", the client terminal is engaged in filtering unnecessary data (for this reason, "Fishing from a satellite" is possible).

The type of outgoing channel is distinguished:

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

In either case, data from the provider to the client is transmitted, as a rule, in accordance with the DVB digital broadcasting standard, which makes it possible to use the same equipment both for accessing the network and for receiving satellite television.

Disadvantages of satellite communications

Weak noise immunity

The huge distances between earth stations and a 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, since they have restrictions on the size of the antenna and, as a rule, on the power of the transmitter.

Influence of the atmosphere

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

Tropospheric absorption

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 (that is, starting from the Ku-band). In addition to absorption, during the propagation of radio waves in the atmosphere, there is a fading effect, which is caused by the difference in the refractive indices of different layers of the atmosphere.

Ionospheric effects

The effects in the ionosphere are due to fluctuations in the distribution of free electrons. The ionospheric effects affecting the propagation of radio waves include flicker, absorption, propagation delay, variance, frequency change, rotation of the plane of polarization... All of these effects diminish with increasing frequency. For signals with frequencies above 10 GHz, their effect is small.

Relatively low frequency signals (L-band and partly C-band) suffer from ionospheric scintillation arising from irregularities in the ionosphere. The result of this flickering is an ever-changing signal strength.

Signal 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 finite propagation speed of radio waves is about 250 ms, and taking into account multiplexing, switching and signal processing delays, the total delay can be up to 400 ms.

Propagation delay is most undesirable in real-time applications such as telephony. Moreover, if the signal propagation time through the satellite communication channel is 250 ms, the time difference between the subscribers' replicas cannot be less than 500 ms.

In some systems (for example, VSAT systems using a star topology), the signal is transmitted twice over the 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 (edit)

Vishnevsky V.I., Lyakhov A.I., Portnoy S.L., Shakhnovich I.V. Historical sketch of the development of network technologies // Broadband information transmission networks. - 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. eighteen
Sklyar B. Digital communication. Theoretical foundations and practical application. Ed. 2nd, rev .: Per. from English - M .: Publishing house "Williams", 2004
Intersputnik official website
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 tasks - new solutions // Journal on 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. Afanasyeva. - 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
Yamal satellite communication and broadcasting system
VSAT FAQ
Dennis Roddy. Satellite Communications. McGraw-Hill Telecommunications, 2001, p. 68
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.

Literature

INTELSAT Satellite Earth Station Handbook
Dennis Roddy. Satellite Communications. - McGraw-Hill Telecommunications, 2001.
Bruce R. Elbert. The Satellite Communication Applications Handbook. - Artech House, Inc., 2004. - ISBN 1-58053-490-2
Ascent to Orbit, a Scientific Autobiography: The Technical Writings of Arthur C. Clarke. - New York: John Wiley & Sons, 1984.

The painful problems are being solved by a chain of space stations with an orbital period of 24 hours, occupying an altitude of 42,000 km relative to the center of the Earth ... in the equatorial plane.

A. Clark, 1945.

In the Stone Age, a coherent network works by repeating actions to regulate the amount of smoke emitted by a fire. The earth knew runners, Little Muk became the best. The modern system uses spacecraft. The advantage of the satellite is the large coverage of the territory. Waves are used mainly short, capable of propagating in a straight line. The world is one - prices are everywhere ...

Prerequisites for use

The idea of rebroadcasting was conceived by Emile Guarini-Foresio in 1899. The concept of mediated signal transmission was published by the German Journal for Electrical Engineering (volume 16, 35-36). Arthur Clarke in 1945 voiced the concept of a communication system between geostationary spacecraft. The writer refused to take a patent, rejecting two conclusions:

Low likelihood of the idea being implemented.
The need to give the idea to humanity as a whole.

At the same time, the scientist indicated the coordinates of the best coverage of areas of the planet's surface:

30 degrees East - Africa, Europe.
150 degrees East - China, Oceania.
90 degrees W. - America.

The writer lowered the operating frequency, expressing his intention to use 3 MHz by reducing the hypothetical reflectors (a few feet).

Ground-based microwave systems

The Anglo-French consortium, led by André Clavier, went further. The first successful attempts to use the microwave range of communication date back to 1931. The English Channel demonstrated the transmission of information at the frequency of 1.7 GHz (modern cellular band) for 64 kilometers by stations equipped with 3 meters diameter dishes, connecting Dover and Calais.

Interesting! The first commercial VHF television channel used 300 MHz.

Historians tend to view World War II as the horse that brought the industry to the top. The invention of the klystron and the improvement of technologies for the manufacture of paraboloids made an invaluable contribution. The heyday of transatlantic relations dates back to the 1950s.

For reference! The first relay line, formed by eight repeaters, New York - Boston, was built in 1947.

America and Europe have established the transmission of information by repeaters (radio communication, called relay). Commercial broadcasting began immediately. A feature of microwave communication is called the ability to accurately predict the result already at the stage of system design.

For reference! Relay communication is a technology for transmitting digital, analog signals between receivers in the field of view.

Spacecraft

The first Soviet satellite (1957) carried communication equipment. Three years later, the Americans raised an inflatable balloon to a height of 1,500 km, which served as a passive repeater, thanks to the metallized coating of the sphere. On August 20, 1964, 11 countries, including the USSR, signed an agreement on the creation of Intelsat (international communications). The Soviet bloc followed the path of secrecy while the West made money. The Eastern Bloc created its own program in 1971.

The satellites were a real find, allowing you to connect the opposite shores of the ocean. Optical fiber is an alternative.

The military was the first to launch the dark horse along with tropospheric communication, which used the effect of wave reflection by the upper layers. The Soviet microwave communications were intercepted by the celestial group Rhyolite. A system developed for the CIA (USA). The device took up a position captured by a ground beam of Soviet relay communications, recording messages. The territories of China and Eastern Europe were controlled. The diameter of the umbrella-like reflectors reached 20 meters.

The US leadership has always known the intentions of the leaders of the USSR, listening to everything, including phone calls. Today, satellite systems allow, thanks to the Doppler effect, to remotely attend any "confidential" conversations held in rooms equipped with a typical double-glazed window.

The first attempts to implement Nikola Tesla's ideas in space are registered: wireless transmission of electricity by satellite antennas. The epic started in 1975. Now the concept has returned home. The Wardencliffe Tower has long since been destroyed, but the main island of Hawaii received its 20 watts wirelessly.

For reference! The use of space communications has proven to be an economically viable alternative to optical fiber.

Signal features

No wonder the use of satellites, with that said.

Transparency windows

The phenomenon of absorption of waves by the atmosphere has been known for a long time. Scientists, having studied the phenomenon, concluded:

Signal attenuation is determined by frequency.
Transparency windows are observed.
The phenomenon is modulated by weather conditions.

For example, the millimeter range (30-100 GHz) is heavily suppressed by rain. The vicinity of the 60 GHz frequency absorbs oxygen molecules, 22 GHz - water. Frequencies below 1 GHz are cut off by radiation from the galaxy. Temperature noise of the atmosphere has a negative impact.

The foregoing explains the choice of modern space communication frequencies. A complete list of the characteristics of the Ku-band signal is shown in the figure.

The C-band is also used.

Reception areas

The beam, crossing the surface of the Earth, forms isotropic curves of equivalent reception. The total losses are:

200 dB - C-band.
206 dB - Ku-band.

Solar interference can interfere with bagging. The worst conditions lasting 5-6 days are created by the off-season (winter, autumn). The luminary's interference provides ground station technicians with guaranteed work. Tracking systems are turned off for the duration of a natural phenomenon. Otherwise, the saucers can catch the Sun, giving the wrong commands to the on-board stabilization systems. Banks, airports receive a warning: communications will be temporarily disrupted.

Fresnel zones

Obstacles around the communication tower provoke the addition of waves, forming zones of attenuation / rise of the signal. The phenomenon explains the need for a clean space near the transceiver. Fortunately, microwave ovens are devoid of this disadvantage. Thanks to an important feature, every summer resident catches NTV + with a plate.

Flicker

Unpredictable changes in the atmosphere cause the signal to constantly change. Fluctuations up to 12 dB in amplitude affect a 500 MHz bandwidth. The phenomenon lasts 2-3 hours maximum. Flickering prevents ground stations from tracking the satellite, requiring preventive action.

Beam linearity

A feature of the microwave is considered to be a rectilinear ray trajectory. The phenomenon allows you to concentrate power, lowering the requirements for on-board systems. Surely the first task was espionage. Later, antennas ceased to be narrowly directed, covering vast territories, such as Russia.

Engineers call the property a disadvantage: it is impossible to go around mountains, ravines.

Features of wave addition

There is practically no interference pattern. It is possible to significantly compact adjacent frequency channels.

Capacity

Kotelnikov's theorem defines the upper limit of the spectrum of the transmitted signal. The threshold is directly set by the carrier frequency. Microwave, due to its high values, contain up to 30 times more information than VHF.

The possibility of regeneration

The development of digital technologies has opened the way for error correction techniques. Artificial satellite:

received a weak signal;
decoded;
fixed bugs;
coded;
passed on.

The excellent quality of satellite communications has become a "proverbial".

Terrestrial antennas

Satellite dishes are called paraboloids. The diameter reaches 4 meters. In addition to the above, there are 2 types of relay communication antennas (both terrestrial):

Dielectric lenses.
Horn antennas.

Paraboloids provide high selectivity, allowing a beam to communicate over thousands of kilometers. A typical cymbal is not capable of transmitting a signal; higher performance is required.

Operating principle

Spy satellites constantly moved, providing relative invulnerability and secrecy of surveillance. The use of peaceful technologies took a different path. Clark's concept implemented:

The equatorial orbit is home to hundreds of geostationary satellites.
The stability of the position provides ease of pointing ground equipment.
The orbital altitude (35786 meters) is fixed, since it is necessary to balance the earth's gravity by the centrifugal force.

The device covers part of the planet's territory.

The Intelsat system is formed by 19 satellites grouped into four regions. The subscriber sees 2-4 at the same time.

The lifetime of the system is 10-15 years, then the obsolete equipment is changed. The gravitational effects of the planets and the Sun reveal the need to use stabilization systems. The correction process significantly reduces the fuel resource of the vehicles. The Intelsat complex allows position deviations of up to 3 degrees, extending the life of the orbital swarm (over three years).

Frequencies

The transparency window is limited to the 2-10 GHz range. Intelsat uses the 4-6 GHz region (C-band). The increase in load caused the transition of part of the traffic to the Ku-band (14, 11, 12 GHz). The working area is distributed in portions to transponders. The terrestrial signal is received, amplified, emitted back.

Problems

The high cost of launching. Overcoming 35 thousand kilometers takes a lot of resources.
The signal propagation delay exceeds a quarter of a second (reaching 1 s).
A small angle of inclination of the line of sight of an artificial aircraft increases energy costs.
The reception area is covered ineffectively. Giant spaces are devoid of subscribers. Broadcast efficiency is extremely low.
The transparency windows are narrow, ground stations have to be scattered geographically, to change polarization.

Solutions

Partially the disadvantages are eliminated by the introduction of an inclined orbit. The satellite ceases to be geostationary (see above Cold War spy satellites). At least three equidistant devices are required to ensure communication around the clock.

Polar orbit

The polar orbit alone is capable of covering the surface. However, several orbital periods of the spacecraft will be required. A swarm of satellites, spaced around the corner, is able to solve the problem. Polar orbits have bypassed commercial broadcasting, becoming a faithful assistant to the systems:

navigation;
meteorology;
ground control stations.

Inclined orbit

Tilt was successfully used by Soviet satellites. The orbit is characterized by the following parameters:

circulation period - 12 hours;
tilt - 63 degrees.

Visible for 8/12 hours, three satellites provide communication to polar regions inaccessible from the equator.

Satellite phone

The mobile gadget directly catches space, bypassing ground towers. The first Inmarsat of 1982 provided access to seafarers. The terrestrial species was created seven years later. Canada was the first to recognize the benefits of equipping desert areas with rare inhabitants. Following the program, the United States mastered.

The problem is solved by launching low-flying satellites:

The circulation period is 70..100 minutes.
Height 640..1120 km.
The coverage area is a circle with a radius of 2800 km.

Considering the physical parameters, the duration of an individual communication session covers the range of 4-15 minutes. Maintaining performance requires a certain amount of effort. A couple of US merchants went bankrupt in the 90s, unable to get enough subscribers.

Weight and dimensions are continuously improving. Globalstar offers proprietary smartphone software that uses Bluetooth to catch the signal of a relatively bulky satellite receiver.

Satellite phones require a powerful receiving antenna, preferably a fixed antenna. They mainly equip buildings and transport.

Operators

ACeS covers Asia with a single satellite.
Inmarsat oldest operator (1979). Equips yachts, ships. With 11 aircraft, the company is slowly expanding into the mobile market with the help of ACeS.
Thuraya serves Asia, Australia, Europe, Africa, the Middle East.
MSAT / SkyTerra is an American provider using equipment equivalent to Inmarsat.
Terrestar covers North America.
IDO Global Communications is inactive.

Networks

Commercial projects are limited.

GlobalStar

GlobalStar is a joint brainchild of Qualcomm and Loral Corporation, later backed by Alcatel, Vodafone, Hyundai, AirTouch, Deutsche Aerospace. The launch of 12 satellites was disrupted, the first call took place on November 1, 1998. The initial cost (Feb 2000) was $ 1.79 / min. After going through a series of bankruptcies and transformations, the company provides clients in 120 countries.

Provides 50% of US traffic (over 10,000 calls). Operation is supported by terrestrial repeaters. 40 in total, including 7 accommodated by North America. Territories devoid of terrestrial repeaters form a zone of silence (South Asia, Africa). Although the devices regularly ply the heavenly heights.

Subscribers receive US phone numbers, excluding Brazil, where they assign the code +8818.

List of services:

Voice calls.
Positioning systems with an error of 30 km.
9.6 kbps Internet packet access.
Mobile communication CSD GSM.
Roaming.

The phones use Qualcomm CDMA technology, excluding Ericsson and Telit, which accept traditional SIM cards. Base stations are forced to support both standards.

Iridium

The provider uses polar orbit, providing 100% planetary coverage. The organizers went bankrupt, and the company was revived in 2001.

It is interesting! Iridium is the culprit behind nighttime sky flares. Flying satellites are clearly visible to the naked eye.

The company's fleet includes 66 satellites using 6 low-earth orbit trajectories with an altitude of 780 km. The devices communicate using the Ka-band. The lion's share was run by former bankruptcy companies. As of January 2017, 7 units have been updated. Regeneration continues: the first group (10 pieces) flew away on January 14, the second on June 25, and the third on October 9.

It is interesting! The satellite Iridium 33 on February 10, 2009 rammed Russian Cosmos 2251. Heavenly debris is flying over Siberia today.

The company continues to provide services to 850 thousand subscribers. 23% of the profit was paid by the state. The cost of the call is $ 0.75 - $ 1.5 / min. Callbacks are comparatively expensive at $ 4 / min (Google Voice). Typical areas of employment for employers:

Oil production.
Marine fleet.
Aviation.
Travelers.
Scientists.

Inhabitants of the Amundsen-Scott South Polar Station asked to give special thanks. The company sells call packages with a duration of 50-5000 minutes everywhere. The validity of the former leaves much to be desired, expensive ones (5000 minutes = 4000 dollars) remain operational for 2 years. Monthly renewal - $ 45:

75 minutes cost $ 175 and can be used for 1 month.
500 minutes - $ 600-700, the term of use is 1 year.

Telephones

The former owners supplied their customers with telephone sets from two manufacturers:

Motorola 9500 became a companion of the first commercial trial of the company. The mobile shock-resistant version 9575, which is still in existence, was born in 2011, supplemented with an emergency GSM call button, an advanced location interface. The device sets up a Wi-Fi hotspot, allowing users of ordinary smartphones to send emails, SMS, and browse the Internet.

Kyocera equipment has been abandoned by the manufacturer. Models are sold by dealers. The KI-G100, based on a 900 MHz GSM phone, is equipped with a case equipped with a powerful antenna that picks up the broadcast. The ability to receive SMS is provided, only certain models can be poisoned (9522). The SS-66K is equipped with an atypical ball antenna.

The 9575 is a shockproof, waterproof phone with a dustproof casing. Withstands temperatures from minus 20 to plus 50 degrees Celsius.
9555 - equipped with a built-in headset, USB interface, an adapter to a serial RS-232 port.
The 9505A is a hefty brick-shaped gadget. Equipped with native RS-232 interface.
SS-55K is a limited edition. Incredible size, sold by eBay resellers.

Other company equipment included:

Pagers.
Payphones.
Equipment for yachts, airplanes.

Buoys

Floating buoys, reminiscent of a tsunami tracking system, are capable of receiving / transmitting short messages. The interface will allow you to use the functionality of a branded phone that refuses to catch satellites.

Introduction. 2

Purpose of work .. 3

1. Development of a satellite communication network. 4

2. The current state of the satellite communication network. 7

3. Satellite communication system. 12

3.1. Satellite repeaters .. 12

3.2. Orbits of satellite repeaters. thirteen

3.3. Coverage areas. 15

4. Application of satellite communications. sixteen

4.1. Trunk satellite communications. sixteen

4.2. VSAT system. sixteen

4.3. Central control station. 17

4.4. Satellite repeater. 17

4.5. Subscriber VSAT terminals .. 18

5. VSAT technology. eighteen

6. Global satellite communication system Globalstar 20

6.1. Ground segment Globalstar 21

6.2. Ground segment of Globalstar in Russia. 22

6.3. Technology of the Globalstar 23 system

6.4. Applications of the Globalstar 23 system

7. Designing a satellite communications network. 24

7.1. Calculation of capital costs for launching a satellite and installing the necessary equipment. 24

7.2. Calculation of operating costs. 25

7.3. Payroll .. 25

7.4. Insurance premiums .. 26

7.5. Depreciation deductions. 26

7.6. Electricity costs for production needs. 26

7.7. Calculation of income. 27

7.8. Calculation of performance indicators. 28

7.9. Calculation of the efficiency of an investment project. 31

Conclusion. 35

List of sources used. 40

Introduction

Modern realities are already talking about the inevitability of replacing conventional mobile and, moreover, landline telephones with satellite communications. The latest satellite communications technologies offer effective technical and cost-effective solutions for the development of both all-available communications services and direct audio and TV broadcasting networks. Thanks to the outstanding achievements in the field of microelectronics, satellite phones have become so compact and reliable in use that they make all the demands of various groups of users, and the service of renting satellite devices 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. This indicates significant prospects for the development of satellite communications services, especially for regions with a low population density over a large area.

Objective

To get acquainted with the history of satellite communications, features and prospects for the development and design of satellite communications.

1. Development of satellite communication network

The history of the development of satellite communications

The forty-five-year history of the development of CVS has five characteristic 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, and the second. This happened in the midst of the Cold War and the rapid arms race, so, naturally, satellite technology became primarily the property of the military. The stage under consideration is characterized by the launch of early experimental satellites, including communication satellites, which were predominantly 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, the SYN-COM (Synchronous Communications Satellite) series of US military communications satellites was developed.

The first two satellites were launched into geosynchronous elliptical orbits. The geostationary satellite of this series SYNCOM-3 was launched into orbit in February 1963 and was the prototype of the first civilian commercial GSR INTELSAT-1 (also called EARLY BIRD), which became the first CP of the international organization Intelsat (International Telecommunications Satellite Organization), established in August 1964 of the year. During this period, commercial satellite communication services were not yet available, but the possibility of production, launch and successful communication through satellites in low-earth orbit was experimentally proven.

1965-1973 The period of development of global CCS based on geostationary repeaters. The year 1965 was marked by the launch in April of the geostationary SR INTELSAT-1, which marked the beginning of the commercial use of satellite communications. The early INTELSAT series satellites provided transcontinental communications and mainly supported backbones between a small number of national gateway earth stations, providing an interface to national public terrestrial networks.

Trunk channels provided connections that carried telephone traffic, TV signals, and telex communications. In general, CCC Intelsat supplemented and backed up the submarine transcontinental cable communication lines that existed at that time. Until the early 1970s, virtually all existing CCSs were used to transmit international telephone traffic and broadcast television programs.

1973-1982 Stage of widespread dissemination of regional and national CCS. During this period, regional ones, for example, Eulelsat, Aussat and national satellite communication networks, for example, Skynet in the United States, were quite intensively deployed, the main services of which were still telephony and television, as well as a small amount of data transmission. But now these services were provided to a large number of terrestrial terminals, and in some cases the transmission was carried out directly to user terminals.

On this stage of the historical development of the CCC, the international organization Inmarsat was created, which deployed the Inmarsat global communication network, the main goal of which was to provide communication with sea-going ships. In the future, Inmarsat expanded its services to all types of mobile users.

1982-1990 Period of rapid development and spread of small terrestrial terminals. In the 1980s, advances in the technology and technology of the key elements of CCC, as well as reforms to liberalize and demonopolize the communications industry in a number of countries, allowed the use of satellite channels in corporate business communications networks, called VSAT. At first, these networks, with the availability of communication channels with an average bandwidth (no more than 64 kbit / s), provided the only information transfer of data, a little later, digital voice transmission was implemented, and then video.

VSAT networks made it possible to install compact earth stations for satellite communications in close proximity to user offices, thereby solving the problem of the "last mile" for a huge number of corporate users, creating conditions for a comfortable and efficient exchange of information, and relieving the burden of public terrestrial networks.

Use of "smart" communication satellites.

· Since the first half of the 90s, CCS have entered a quantitatively and qualitatively new stage of their development.

A large number of global and regional satellite communications networks were in operation, production or design. Satellite communication technology has become an area of significant interest and business activity. During this time period, there has been an explosive growth in the speed of general-purpose microprocessors and the volume of semiconductor memory devices, while increasing reliability, as well as reducing power consumption and cost of these components. Semiconductor electronics for space applications must be radiation resistant. which is achieved by special technological methods and careful shielding of electronic circuits.

The emergence of radiation-resistant microprocessors with a clock frequency of (1-4) MHz and high-speed RAM circuits with a volume of (10 ^ 5-10 ^ 6) Mbit served as a technological basis for the practical implementation of truly "intelligent" BR "GCs with capabilities and characteristics that at first glance seemed fantastic.

2. The current state of the satellite communication network

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

Due to the use of relatively low frequency ranges, the system allows providing low-speed data transmission services to simple low-cost subscriber devices, such as e-mail, two-way paging, and remote control services. 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 famous 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. Three MSS systems compete for Inmarsat, in particular 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. Thuraya is slated to go global in 2007 with the launch of a third geostationary (GSO) satellite to cover the American continent, where it is currently unavailable. All three systems provide telephony and low-speed data services to receivers comparable in weight and size to GSM mobile phones.

Also in the world there are four regional MSS systems. In North America, this is Mobile Satellite Ventures (MVS) using two MSAT satellites. In 2000, the Asia Cellular Satellite (Indonesia) began operating with the Garuda satellite, providing MSS services in the Asian region. In the same year, two N-Star satellites began serving maritime MSS subscribers in Japan's 200-mile coastal zone. Australia has a similar maritime MSS system, Optus.

The International Telecommunication Union (ITU) defines the MSS perspective as the satellite segment of the third generation mobile service systems IMT-200. Satellite networks can provide coverage to service areas where it is economically inefficient to develop a terrestrial network, particularly in remote and rural areas, and create hot spares for it.

The MSS development strategy is based on the creation of the so-called Ancillary Terrestrial Component (ATC) in the USA and the Complementary Ground Component (CGC) in Europe) - this is a part of the MSS that includes ground stations that have a fixed position and are used to improve availability of MSS network services in service areas where satellite stations cannot provide the required quality.

Subscriber devices in the coverage area of base stations will work with a terrestrial network, and upon exiting it will switch to work with a satellite using the same frequency band allocated for the MSS. At the same time, the MSS systems must maintain their functionality and provide the required services independently of the ATC. It is also envisaged that the satellite component of IMT-2000 will provide feeder links, core networks and hot spares in the event of an accident or terrestrial network congestion.

ITU predicts that by 2010, the satellite segment of IMT-2000 will require about 70 MHz in both directions to operate. In accordance with the Radio Regulations, the band 1980-2010 / 2170-2200 MHz should be used as the root band. If additional frequencies need to be used, administrations may choose any of the frequencies allocated to the MSS in the 1-3 GHz range, in particular:

1525-1544 / 1626.5-1645.5 MHz;

1545-1559 / 1646.5-1660.5 MHz;

1610-1626.5 / 2483.5-2500 MHz;

2500-2520 / 2670-2690 MHz.

To date, programs have already been identified for the implementation of development concepts for existing MSS systems. In December 2005, Inmarsat announced the deployment of its broadband global network (BGAN). The system provides services to mobile and portable subscriber devices with a transmission rate of up to 432 kbps and will be compatible with terrestrial mobile networks. Globalstar, Iridium and MVS propose by 2012-2013. complete update of the grouping.

All three companies are planning to create an additional ground component. Nevertheless, several facts should be taken into account that can significantly affect the general conclusions regarding the economic efficiency and development prospects of the PSS:

MSS services are in demand mainly by specialized groups of subscribers, in particular by maritime and aviation companies, various government departments and special services. For example, the US Department of Defense is the largest corporate user of Iridium, with a two-year, $ 72 million contract providing unlimited connectivity for 20,000 users. Globalstar Announces 300% Increase in Daily Connections During Rescue and Recovery Operations Following Recent US Hurricanes and Tsunami in Southeast Asia;

Globalstar and Iridium went through bankruptcy proceedings, thus the economic efficiency of projects in practice was achieved due to the ruin of investors;

technological development is making it possible to significantly improve the performance of satellite subscriber receivers. Nevertheless, due to the need to provide high energy on-board receivers and the limited spectrum used, it will be economically unprofitable or technically impossible to provide the same services to a mobile subscriber unit as when working with a terrestrial mobile network.

Thus, satellite technologies cannot be seen as viable competitors for terrestrial mobile networks. The implementation of such projects can be economically justified only in the case of government funding. The deployment of the ATC segment in practice will only mean that operators of terrestrial networks will be able to develop their networks in the bands allocated for the MSS.

MSS systems will continue to play an important role for the work of law enforcement agencies and in the elimination of the consequences of natural disasters and various disasters. The International Telecommunication Union, for example, has a special agreement on the terms of use of Thuraya terminals to provide connectivity to assist affected countries in such cases.

A commercially promising direction in the development of MSS may be not speech or data transmission to subscriber receivers, but the provision of various broadcast services. In this case, superimposed networks for terrestrial mobile networks will be created, which can efficiently, both in terms of economics and spectrum use, provide services in a point-to-multipoint topology. This may include broadcasting sound and television programs and broadcasting various types of data to all or specific categories of subscribers.

Britain's largest satellite TV operator BSkyB, for example, has signed an agreement with Vodafon to create a SKY Mobile TV package, offering mobile subscribers to receive a variety of broadcast programs. A similar project, Unlimited Mobile TV, involving the creation of a hybrid terrestrial-satellite broadcasting network, has been launched by Alcatel and SFR in France.

Another particular application for MSS services, which is currently being investigated in Europe, could be the provision of all types of services to group receivers installed on high-speed vehicles such as intercity and international trains and buses.

3. Satellite communication system

3.1. Satellite repeaters

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

All modern communications satellites are active. Active repeaters are equipped with electronic equipment for signal reception, processing, amplification and retransmission. 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. The satellite can use several independent channels performing these operations, each of which works with a certain part of the spectrum (these processing channels are called transponders).

3.2. Satellite repeater orbits

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

Equatorial

Inclined

Polar

An important type of 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 rotation of the Earth. The obvious advantage of 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 launch all 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 unable to serve earth stations in the circumpolar region.

An inclined orbit can solve 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 - an orbit that has an inclination of the orbit to the equatorial plane at ninety degrees.

3.3. 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. This can be done in two ways: spatial separation - each satellite antenna receives a signal only from a certain area, while different regions can use the same frequencies, polarization separation - different antennas receive and transmit a signal in mutually perpendicular polarization planes, while the same and 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. Western and Eastern Hemisphere Beams - These beams are polarized in the A plane, with the same frequency range used in the Western and Eastern hemispheres. Zone beams are polarized in the B plane (perpendicular to A) and use the same frequencies as the beams of the hemispheres. Thus, an earth station located in one of the zones can also use hemispherical beams and a global beam.

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

4. Application of satellite communications

4.1. Backbone satellite communications

4.2. VSAT system

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

On the basis of VSAT equipment, it is possible to build multiservice networks that provide almost all modern communication services: Internet access; telephone communication; combining 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 ATC-1 satellite, an experimental network was created, consisting of 25 earth stations, satellite telephone communications in Alaska. Linkabit, one of the first to develop Ku-band VSATs, merged with M / A-COM, which later became a leading supplier of VSAT equipment. Hughes Communications acquired the division from M / A-COM, transforming it into Hughes Network Systems. Today, Hughes Network Systems is the world's leading provider of broadband satellite communications. The satellite communication network based on VSAT includes three key elements: central control station (NCC), satellite relay and subscriber VSAT terminals.

4.3. Central control station

The NCC includes receiving and transmitting equipment, antenna-feeder devices and a complex of equipment that performs the functions of monitoring and controlling the operation of the entire network, redistributing its resources, identifying malfunctions, billing for network services and interfacing with land lines. To ensure the reliability of communication, the equipment has at least 100% redundancy. The central station is interfaced with any terrestrial trunk communication lines and has the ability to switch information flows, thereby supporting information interaction of network users with each other and with subscribers of external networks (Internet, cellular networks, PSTN, etc.).

4.4. Repeater satellite

VSAT networks are based on geostationary relay satellites. The most important characteristics of a satellite are the power of onboard transmitters and the number of radio frequency channels (trunks or transponders) on it. The standard trunk has a bandwidth of 36 MHz, which corresponds to a maximum throughput of about 40 Mbps. On average, the power of the transmitters ranges from 20 to 100 watts. In Russia, the Yamal communication and broadcasting satellites can be cited as examples of relay satellites. They are intended for the development of the space segment of OJSC Gazkom and were installed in orbital positions 49 ° E. d. and 90 ° east. etc.

4.5. Subscriber VSAT terminals

Subscriber VSAT terminal is a small satellite communication station with an antenna of 0.9 to 2.4 m in diameter, designed mainly for reliable data exchange via satellite channels. The station consists of an antenna-feeder device, an external external radio frequency unit and an internal unit (satellite modem). The outdoor unit is a small transceiver or just a receiver. The indoor unit connects 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 (also called a return channel). The satellite channel is used as a direct channel for receiving data to the subscriber terminal (the DVB standard is used). A standard set consisting of a receiving parabolic antenna, a converter and a satellite DVB receiver in the form of a PCI card installed in a computer or an external USB block is used as the receiving equipment.

When organizing two-way access, VSAT equipment can be used for both forward and reverse channels. The presence of land lines in this case is not required, but they can also be used (for example, for the purpose of redundancy).

The direct channel is usually formed in accordance with the specifications of the DVB-S standard and is broadcast via a communication satellite to all subscriber stations of the network located in the working area. On the return channel, separate relatively low-rate TDMA streams are formed. At the same time, to increase the network capacity, the so-called multi-frequency TDMA technology (MF-TDMA) is used, which provides for frequency hopping when one of the reverse channels is overloaded.

VSAT networks can be organized in the following topologies: fully meshed (each with each), radial (star), and radial-node (combined) topologies. Each topology has its own advantages and disadvantages, the choice of one or another topology must be carried out taking into account the individual characteristics of the project. Satellite communication is a type of radio communication. Satellite signals, especially in the high-frequency Ku and Ka bands, are susceptible to attenuation in humid atmospheres (rain, fog, clouds). This disadvantage is easily overcome when designing the system.

Satellite communications are subject to interference from other radio equipment. However, for satellite communications, frequency bands are allocated that are not used by other radio systems and, in addition, narrow-beam antennas are used in satellite systems to completely get rid of interference. Thus, most of the disadvantages of satellite communication systems are eliminated by competent network design, choice of technology and antenna installation location.

VSAT technology is a very flexible system that allows you to create networks that meet the most stringent requirements and provide a wide range of data transmission services. Reconfiguration of the network, including changing exchange protocols, adding new terminals or changing their geographic location, is carried out very quickly. The popularity of VSAT in comparison with other types of communication when creating corporate networks is explained by the following considerations: for networks with a large number of terminals and with significant distances between subscribers, operating costs are significantly lower than when using terrestrial networks

6. Global satellite communication system Globalstar

The Globalstar system is a consortium of Globalstar L. P of international telecommunications companies Loral Space & Telecommunications, Qualcomm, Elsag Baily, Space Systems / Loral, Daimler-Benz Aerospace, Alenia, Alcatel, Hyundai, Dacom and telecom operators - France Telecom, Vodafone Goup. The consortium was founded in 1991. The Globalstar system was formed as a system designed to interoperate with existing cellular networks, complementing and expanding their capabilities by providing communications outside of coverage areas. In addition, the system provides an opportunity to use it as an alternative for fixed communications in remote areas where the use of cellular communications or the public network for some reason is impossible.
In Russia, the operator of the Globalstar satellite communications system is the Closed Joint Stock Company GlobalTel. As an exclusive provider of global mobile satellite communications services for the Globalstar system, CJSC GlobalTel provides communications services throughout the Russian Federation. Thanks to the creation of CJSC GlobalTel, residents of Russia have one more opportunity to communicate via satellite from anywhere in Russia with almost anywhere in the world.

The Globalstar system provides satellite communications of high quality to its subscribers using 48 working and 8 spare LEO satellites located at an altitude of 1410 km. (876 miles) from the surface of the Earth. The system provides global coverage of almost the entire surface of the globe between 700 North and South latitude with an expansion up to 740. Satellites are able to receive signals up to 80% of the Earth's surface, that is, from almost anywhere in the world with the exception of the polar regions and some zones of the central part of the oceans ... The satellites of the system are simple and reliable.

6.1. Ground segment Globalstar

The ground segment of the Globalstar system consists of spacecraft control centers, communications control centers, a network of regional ground gateway stations and a data exchange network.
Gateway stations are designed to organize radio access for users of the Globalstar system to the switching centers of the system when establishing communication between users of the system, as well as with users of terrestrial and satellite networks of fixed and mobile communications, with operators of which interconnection is carried out. Gateways are part of the Globalstar system and provide reliable telecommunications services for fixed and mobile subscriber terminals throughout the global service area. Ground control centers plan communication schedules for gateways and control the allocation of satellite resources to each gateway. The satellite segment control center monitors the satellite system. Together with the means of the reserve Center, it controls the orbits, processes telemetric information and issues commands to the satellite constellation. The satellites of the Globalstar system continuously transmit telemetry data, which monitor the health of the system, as well as information about the general condition of the satellites. The center also monitors satellite launches and the process of their deployment in space. The satellite segment control center and ground control centers maintain constant contact with each other via the Globalstar data network.

6.2. Ground segment of Globalstar in Russia

The Russian ground segment of the Globalstar system includes 3 gateways located near Moscow, Novosibirsk and Khabarovsk. They cover the territory of Russia from the southern border to 74 gr. With. sh. and from the western border to the 180th meridian, providing guaranteed quality of service south of the 70th parallel.

Russian gateway stations Globalstar are connected to the PSTN network through automatic switching nodes, have connecting lines with international switching centers, and are also interconnected by digital paths "each to each". Each gateway is integrated with existing fixed and cellular networks in Russia. Gateway stations have the status of an intercity station of the national network of the Russian Federation. At the same time, the Russian segment of the Globalstar satellite system is considered as a new communication network on the territory of the Russian Federation.

6.3. Technology of the Globalstar system

The satellites operate according to the bent-pipe architecture - receiving a subscriber's signal, several satellites, using CDMA technology, simultaneously broadcast it to the nearest ground gateway. The ground gateway selects the strongest signal, authorizes it and routes it to the called subscriber.

6.4. Areas of application of the Globalstar system

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

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

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 Russian state structures - ministries and departments (for example, the Ministry of Emergency Situations), can actively use satellite communications in their activities. Special kits for installation on vehicles can be effective when used on commercial vehicles, on fishing and other types of sea and river vessels, on railway transport, etc.

7. Designing a satellite communications network.

7.1. Calculation of capital costs for launching a satellite and installing the necessary equipment.

Table 1.1.- Initial data for the calculation of capital costs

K about - capital investments for the purchase of equipment for servicing the satellite;

K s - capital investments for the acquisition of a satellite;

K m - equipment installation costs;

K tr - transportation costs;