Modern satellite communications satellite systems. Satellite communications, types, system, equipment, facilities, orbits, satellite communications ranges
Space or satellite communication is essentially a kind of radio relay (tropospheric) communication and differs in that its repeaters are not on the surface of the Earth, but on satellites in outer space.
For the first time an idea satellite communications Introduced in 1945 by the Englishman Arthur Clarke. In a radio engineering journal, he published an article on the prospects of rockets like the V-2 for launching Earth satellites for scientific and practical purposes. The last paragraph of this article is significant: “An artificial satellite at a certain distance from the Earth will make one revolution in 24 hours. It will remain motionless over a certain place and within optical visibility from almost half of the earth's surface. Three repeaters, placed in a well-chosen orbit with an angular separation of 120°, will be able to cover the entire planet with TV and VHF radio broadcasts; I am afraid that those who plan post-war work will not consider this a simple matter, but I consider this way to be the final solution to the problem.
On October 4, 1957, the USSR launched the world's first artificial Earth satellite, the first space object whose signals were received on Earth. This satellite marked the beginning of the space age. The signals emitted by the satellite were used not only for direction finding, but also for transmitting information about the processes on the satellite (temperature, pressure, etc.). This information was transmitted by changing the duration of the messages emitted by the transmitters (pulse width modulation). On April 12, 1961, for the first time in the history of mankind, a manned flight into outer space was carried out in the Soviet Union. The spacecraft "Vostok" with pilot-cosmonaut Yu. A. Gagarin on board was put into orbit as an Earth satellite. Numerous measuring and radiotelemetric equipment were installed on board to measure the parameters of the orbit of the satellite and control the operation of its onboard equipment. For the direction finding of the ship and the transmission of telemetric information, the Signal radio system was used, operating at a frequency of 19.955 MHz. The astronaut's two-way communication with the Earth was provided by a radiotelephone system operating in the ranges of short (19.019 and 20.006 MHz) and ultrashort (143.625 MHz) waves. The television system transmitted the astronaut's image to Earth, which made it possible to have visual control over his condition. One of the television cameras transmitted the image of the pilot from the front, and the other from the side.
The achievements of domestic science in the field of space exploration made it possible to realize the predictions of Arthur C. Clarke. At the end of the 1950s, experimental studies began in the USSR and the USA on the possibilities of using artificial Earth satellites as radio repeaters (active and passive) in terrestrial communication systems. Theoretical developments in the field of energy capabilities of satellite communication lines made it possible to formulate tactical and technical requirements for satellite repeater devices and ground devices, based on real characteristics technical means that existed at that time.
Given the identity of the approaches, we will present experimental studies in the field of creating satellite communication lines using the example of the United States. The first active radio repeater "Score" was launched on December 18, 1958 into an inclined elliptical orbit with an apogee of 1481 km, a perigee of 177 km. The satellite equipment consisted of two transceivers operating at frequencies of 132.435 and 132.095 MHz. The work was carried out in the slow relay mode. The storage of the signal sent by the ground transmitting station was carried out by recording on magnetic tape. Silver-zinc batteries with a capacity of 45 ampere-hour at a voltage of 18 volts were used as power sources. The duration of communication was approximately 4 min per 1 revolution of the satellite. Retransmission of 1 telephone or 7 teletype channels was carried out. The lifetime of the satellite was 34 days. The satellite burned up on re-entry on January 21, 1959. The second active radio relay "Courier" was launched on October 4, 1960 into an inclined elliptical orbit with an apogee of 1270 km and a perigee of 970 km. The satellite equipment consisted of 4 transceivers (frequency 150 MHz for transmitting commands and 1900 MHz for communication), a magnetic memory device and power sources - solar cells and chemical batteries. Silicon solar cells in the amount of 19,152 pieces were used as the primary power source. Nickel-cadmium batteries with a capacity of 10 amperes - hour at a voltage of 28-32 volts were used as a buffer stage. The duration of the communication session was 5 min per one revolution of the satellite. The service life of the satellite was 1 year. On July 10, 1962, the Telstar active relay was launched into an inclined elliptical orbit with an apogee of 5600 km and a perigee of 950 km, which was intended for active relaying of radio signals in real time. At the same time, it relayed either 600 simplex telephone channels, or 12 duplex telephone channels, or one television channel. In all cases, the work was carried out according to the method of frequency modulation. Communication frequencies: on the satellite-Earth line 4169.72 MHz, on the Earth-satellite line 6389.58 MHz. The duration of the communication session on the US-Europe line via this satellite was about 2 hours per day. The quality of the transmitted television images varied from good to excellent. The project provided for a very significant satellite service life of 2 years, but after four months of successful operation, the command line failed. It was found that the cause of the failure was surface damage due to the action of radiation when the satellite passed through the inner radiation belt.
On February 14, 1963, the first synchronous satellite of the Sinkom system was launched with orbital parameters: apogee height 37,022 km, perigee height 34185, orbital period 1426.6 minutes. The operating frequency on the Earth-satellite line is 7360 MHz, on the satellite-Earth line is 1820 MHz. 3840 solar cells with a total power of 28 W at a voltage of 27.5 volts were used as the primary power source on the satellite. Communication with the satellite was maintained for only 20,077 seconds, after which observations were made by astronomical methods.
On April 23, 1965, the first communications satellite Molniya-1 was launched in the USSR. With the launch of the second communication satellite "Molniya-2" on October 14, 1965, regular operation of the long-distance communication line through satellites began. Later, the Orbita deep space communication system was created. It consisted of a network of ground stations and artificial Earth satellites "Lightning", "Rainbow", "Horizon". Below, in Chapter 7, it will be shown that modifications of the Horizon satellites continue to function in the 21st century. This indicates the high reliability of domestic equipment compared to foreign ones.
The first satellite communication stations were built, tested and put into operation in the town of Shchelkovo near Moscow and in Ussuriysk. By cable and relay communication lines, they were connected, respectively, with television centers and telephone long-distance stations in Moscow and Vladivostok.
The TR-60/120 tropospheric communication equipment, which, as is known, used high-power transmitters and highly sensitive receivers with low-noise parametric amplifiers, turned out to be the most suitable for the equipment of earth stations of the satellite system. On its basis, a receiver-transmitter complex "Horizont" is being developed, which is installed at ground stations of the first satellite communication line between Moscow and Vladivostok.
Transmitters were specially developed for communication and command-measuring lines, parametric amplifiers with a noise temperature of 120 K for installation in an antenna under the mirror cabin, as well as completely new equipment that provides docking with local television centers and long-distance telephone exchanges.
In those years, earth station designers, fearing the influence of powerful transmitters on receivers, installed them on different antennas and in different buildings (receiving and transmitting). However, the experience of using one common antenna for receiving and transmitting, obtained on tropospheric communication lines, made it possible in the future to transfer the receiving equipment to the transmitting antenna, which greatly simplified and cheapened the operation of satellite communication stations.
In 1967, through the Molniya-1 communications satellite, an extensive television network of receiving earth stations "Orbita" was created with a central transmitting station near Moscow. This made it possible to organize the first communication channels between Moscow and the Far East, Siberia, Central Asia, to transmit the Central Television program to remote areas of our Motherland and to additionally cover more than 30 million viewers.
However, the Molniya satellites revolved around the Earth in elongated elliptical orbits. To track them, the antennas of ground receiving stations must constantly rotate. It is much easier to solve this problem by satellites rotating in a stationary circular orbit, which is located in the equatorial plane at an altitude of 36,000 km. They make one revolution around the Earth in 24 hours and therefore seem to a ground observer hanging motionless over one point of our planet. Three such satellites are enough to provide communications for the entire Earth.
In the 1980s, communication satellites "Raduga" and television satellites "Ekran" operating in stationary orbits effectively functioned. To receive their signals, complex ground stations were not needed. Television transmissions from such satellites are received directly on simple collective and even individual antennas.
In the 1980s, the development of personal satellite communications began. In this connection, a satellite phone is directly connected to a satellite in Earth orbit. From the satellite, the signal arrives at the ground station, from where it is transmitted to the conventional telephone network. The number of satellites required for stable communication anywhere in the world depends on the radius of the orbit of a particular satellite system.
The main disadvantage of personal satellite communications is its relative high cost compared to cellular communications. In addition, high power transmitters are built into satellite phones. Therefore, they are considered unsafe for the health of users.
The most reliable satellite phones operate on the Inmarsat network, established over 20 years ago. Inmarsat satellite phones are a flip-top case the size of early laptop computers. The cover of the satellite phone is also an antenna, which must be turned towards the satellite (the signal level is displayed on the phone display). These phones are mainly used on ships, trains or heavy vehicles. Every time you need to make or answer someone's call, you will need to install the satellite phone on some flat surface, open the lid and twist it, determining the direction of the maximum signal.
Currently, in the overall balance of communications on satellite systems still accounts for about 3% of world traffic. But the need for satellite links continues to grow, as satellite links become more cost-effective than other forms of long-distance communication at ranges in excess of 800 km.
In 1945, in the article "Extra-terrestrial Relays", published in the October issue of the magazine "Wireless World", the English scientist, writer and inventor Arthur Clark proposed the idea of creating a system of communication satellites in geostationary orbits that would allow organizing a global communication system.
Subsequently, Clarke, when asked why he did not patent the invention (which was quite possible), answered that he did not believe in the possibility of implementing such a system during his lifetime, and also believed that such an idea should benefit all of humanity.
The first studies in the field of civilian satellite communications in Western countries began to appear in the second half of the 1950s. In the United States, they were spurred on by the increased need for a transatlantic telephone connection.
Postal envelope dedicated to the 5th anniversary of the launch of the first Earth satellite
In 1957, the first artificial Earth satellite with radio equipment on board was launched in the USSR.
Balloon "Echo-1"
On August 12, 1960, US specialists launched an inflatable balloon into orbit at a height of 1500 km. This spacecraft was called "Echo-1". Its metallized shell with a diameter of 30 m served as a passive repeater.
Engineers are working on the world's first commercial communication satellite, Early Bird
On August 20, 1964, 11 countries signed an agreement on the creation of the international satellite communications organization Intelsat (International Telecommunications Satellite Organization), but the USSR was not among them for political reasons. On April 6, 1965, as part of this program, the first commercial communications satellite, Early Bird, was launched by the COMSAT Corporation.
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 moment in time, communication could be 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.
In the future, 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 closeness of the space program, the development of satellite communications in the socialist countries proceeded differently than in 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 communication system, which was signed only in 1971.
The first artificial earth satellite.
The launch of the world's first artificial Earth satellite was carried out in the Soviet Union on October 4, 1957 at 22:28. 34 s Moscow time. For the first time in history, hundreds of millions of people could observe in the rays of the rising or setting sun an artificial star moving across the dark sky, created not by gods, but by human hands. And the world community perceived this event as the greatest scientific achievement.
The first satellites with satellite communications.
On May 13, 1946, Stalin signed a decree on the creation in the USSR of the rocket branch of science and industry. In its development, in August 1946, Sergei Korolev (academician since 1958) was appointed chief designer of long-range ballistic missiles. At that time, none of us foresaw that, working with him, we would be participants in the launch of the world's first satellite, and shortly after that, the first half a hundred people into space - Yuri Gagarin.
In January 1956, a government decree was prepared and signed on January 30 on the creation of an unoriented satellite under the secret code "Object D" weighing 1000-1400 kg with equipment for scientific research weighing 200-300 kg.By July 1956, the project of the first satellite was completed, the radiation of the Sun, magnetic fields, cosmic rays, the thermal regime of the satellite, its deceleration in the upper atmosphere, the duration of existence in orbit, etc.
By the end of 1956, it became clear that the timing of the creation of artificial satellites would be disrupted due to the difficulties in manufacturing reliable scientific equipment. However, the project "Object D" was approved by a special committee of the Council of Ministers of the USSR. And earlier, on February 12, 1955, in the semi-desert, in the area of Tyuratam station, the army under the command of General Shubnikov began the construction of research and test site No. 5 (since 1961, this place has been known as the Baikonur cosmodrome).
During 1955-1956 the production of the first technological complex of the R-7 carrier rocket was completed, it was tested at the Leningrad Metal Plant together with a real launch system. On firing stands near Zagorsk (now the city of Peresvet), fire tests of individual rocket blocks began. Under the leadership of N. Pilyugin, modeling and comprehensive testing of the control system were carried out. (the height of the R-7 launcher is 342.2 meters)
They tried to launch a rocket into space 4 times, but due to malfunctions in the equipment and the unreliability of the rocket shell, a simplified version was proposed by Korolev. On September 17, 1957, the 8K71PS launch vehicle (M1-PS product) arrived at the test site. It was significantly lightened compared to regular missiles. The dummy head was removed and replaced with a satellite adapter. All the equipment of the radio control system was removed from the central unit - after all, accuracy was not required. Removed one of the telemetry systems. We simplified the automatic shutdown of the engine of the central unit. Thus, the launch mass of the rocket was lightened by 7 tons compared to the first samples.
October 4, 1957 at 22:28 3 from Moscow time, the start was carried out. After 295.4 s, the satellite and the central block of the launch vehicle went into orbit. For the first time, the first cosmic velocity was achieved, calculated by the founder of classical physics and the law of universal gravitation, the Englishman Isaac Newton (1643‑1727). It was 7780 m/s for the first satellite. The inclination of the satellite's orbit was 65.1 about , perigee height 228 km, apogee height - 947 km, orbital period 96.17 min
when the “BIP-BIP-BIP” signals, which became immediately known to all mankind, were received at the test site, the existence of satellite communications began.
The first satellite existed for 92 days (until January 4, 1958). During this time, he made 1440 revolutions, the central block worked for 60 days: it was observed with a simple eye as a star of the 1st magnitude.
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 stationary and mobile.
Satellite communication is the development of traditional radio relay communication by placing the 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 globe, there is no need for a chain of repeaters. For transmission via satellite, the signal must be modulated. The modulation is done at the earth station. The modulated signal is amplified, transferred to the desired frequency and fed to the transmitting antenna.
Research in the field of civilian satellite communications in Western countries began to appear in the second half of the 1950s. The impetus for them was the increased need for transatlantic telephone communications. The first artificial Earth satellite was launched in the USSR in 1957, however, due to the greater closeness of the space program, the development of satellite communications in the socialist countries proceeded differently than in Western countries. For a long time satellite communications developed only in the interests of the Ministry of Defense of the USSR. The development of civil satellite communications began with an agreement between 9 countries of the socialist bloc on the creation of the Intersputnik communication system, which was signed only in 1971.
In the early years of research, passive satellite repeaters were used, which were a simple radio signal reflector (often a metal or polymer sphere with a metal coating) that did not carry any transceiver equipment on board. Such satellites have not received distribution. All modern communication satellites are active. Active repeaters are equipped with electronic equipment for receiving, processing, amplifying and retransmitting a signal. Satellite repeaters can be non-regenerative and regenerative. A non-regenerative satellite, having received a signal from one earth station, transfers it to another frequency, amplifies and transmits it to another earth station. The satellite can use several independent channels that perform these operations, each of which operates with a certain part of the spectrum (these processing channels are called transponders. The regenerative satellite demodulates the received signal and re-modulates it. Due to this, error correction is performed twice: on the satellite and on the receiving terrestrial station The disadvantage of this method is the complexity (and therefore much more high price satellite), as well as increased signal transmission delay.
Orbits of communication satellites:
The orbits in which satellite transponders are located are divided into three classes:
1 - equatorial, 2 - oblique, 3 - polar
An important variation of the equatorial orbit is the geostationary orbit, in which the satellite rotates at an angular velocity equal to the angular velocity of the Earth, in a direction coinciding with the direction of the Earth's rotation. Obvious advantage geostationary orbit is that the receiver in the service area "sees" the satellite all the time. However, there is only one geostationary orbit, and it is impossible to put all the satellites into it. Its other disadvantage is its large height, 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.
An inclined orbit solves these problems, however, due to the movement of the satellite relative to the ground observer, it is necessary to launch at least three satellites per orbit in order to provide round-the-clock communication access.
Polar orbit - limiting case of oblique
When using inclined orbits, earth stations are equipped with tracking systems that point the antenna at the satellite. Stations operating satellites in geostationary orbit are also typically equipped with such systems to compensate for deviations from the ideal geostationary orbit. The exception is small antennas used for receiving satellite television: their radiation pattern is wide enough that they do not feel satellite vibrations near the ideal point. A feature of most mobile satellite communications systems is the small size of the terminal antenna, which makes signal reception difficult.
A typical scheme for organizing satellite communications services is as follows:
- - the operator of the satellite segment creates a communication satellite at his 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 launching the satellite into orbit, the operator of the satellite segment begins to provide services for leasing the frequency resource of the repeater satellite to companies operating satellite communications services.
- - a satellite communications services 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. A satellite communications service operator builds the ground infrastructure of its network on a specific technological platform produced by manufacturers of ground equipment for satellite communications.
Scope of satellite communications:
- - Backbone satellite communications: initially, the emergence of satellite communications was dictated by the needs of transmitting large amounts of information. The first satellite communication system was the Intelsat system, then similar regional organizations were created (Eutelsat, Arabsat and others). Over time, the share of voice transmission in the total volume of backbone traffic has been constantly decreasing, giving way to data transmission. With the development of fiber-optic networks, the latter began to displace satellite communications from the backbone communications market.
- - VSAT systems: 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 is typically less than 2048 kbps. The words "very small aperture" refer to the size of the terminal antennas compared to older backbone antennas. VSAT terminals operating in C-band usually use antennas with a diameter of 1.8-2.4 m, in Ku-band - 0.75-1.8 m. VSAT systems use on-demand channeling technology.
- - Mobile satellite systems: A feature of most mobile satellite systems is the small size of the terminal antenna, which makes it difficult to receive the signal.
VSAT satellite communications organization principles:
A typical scheme for organizing a VSAT satellite network is as follows:
- - relay satellite located in orbit (communications satellite)
- - network control center (NCC) of the VSAT network operator, serving the equipment of the entire network via a communication satellite
- - equipment (satellite modems or terminals) located on the client side and interacting with the outside world or with each other through the HUB of the VSAT operator in accordance with the network topology
The main element of the VSAT satellite network is the NCC. It is the Network Control Center that provides access to client equipment from the Internet, telephone network public, to other terminals of the VSAT network, implements the exchange of traffic within corporate network client. The NCC has a broadband connection to backbone communication channels provided by trunk operators and ensures the transfer of information from a remote VSAT terminal to external world. The NCC is equipped with a powerful transceiver complex that transmits all network information flows to a communication satellite. The NCC includes channel-forming equipment (satellite transceiver antenna, transceivers, etc.) and HUB (processing and switching center for all information in the VSAT network)
Technologies used in satellite communications:
frequency reuse 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. You can do this 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 applied twice (for each of the planes).
frequency ranges:
The choice of frequency for transmitting data from an earth station to a satellite and from a satellite to an earth station is not arbitrary. The 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 earth station-to-satellite transmissions occur are different from those used for satellite-to-earth station transmissions (generally the former is higher). The frequencies used in satellite communications are divided into ranges, denoted by letters:
|
Range name |
Application |
|
|
Mobile satellite communications |
||
|
Mobile satellite communications |
||
|
4 GHz, 6 GHz |
Fixed satellite communications |
|
|
For satellite communications in this range, frequencies are not defined. For radar applications, the 8-12 GHz range is specified. |
Fixed satellite communications (for military purposes) |
|
|
11 GHz, 12 GHz, 14 GHz |
||
|
Fixed satellite communication, 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 have a significant impact on transmission quality in this band. For data transmission by large users (organizations), the C-band is often used. This provides better reception quality, but requires a rather large antenna.
Mobile satellite communications
Introduction
Any communication system ultimately depends on some basic system parameters that determine the quality of communication.
So, if for cellular communication such a main parameter is the height of the base station antenna, then for satellite communication systems it is the type of orbit of its space segment and the characteristics of the orbit. In general, any satellite communication system consists of three segments, as mentioned above: space (or space constellation), ground (ground service stations, gateway stations) and user segment (directly terminals located at the consumer).
Figure 1 The structure of the satellite communication system on the example of the VSAT network of the State Enterprise "Cosmic" communication"
According to the type of orbits used, satellite communication systems are divided into two classes: systems with satellites in geostationary orbit (GEO) (altitude 36,000 km; the number of satellites for the GEO constellation is 3, one satellite covers 34% of the earth's surface; communications - 600 ms) and non-geostationary.
Figure 2. Orbits and coverage areas of the earth's surface on the example of the geostationary space constellation of the INMARSAT system
Non-geostationary satellite systems, in turn, are divided into medium-altitude MEO (height - 5000-15000 km; number of spacecraft - 8-12; coverage area of one satellite - 25-28%; delay in voice transmission for global communications - 250-400 ms) and low-orbit LEO (height - 500-2000 km; number of spacecraft - 48-66; coverage area of one satellite - 3-7%; voice transmission delay for global communication - 170-300 ms).
Most of the existing satellite communication systems have geostationary satellite constellations, which is easily explained: a small number of satellites, coverage of the entire surface of the earth. However, a large signal delay makes them applicable, as a rule, only for radio and television broadcasting. For radiotelephone communication systems, a large signal delay is highly undesirable, as it leads to poor quality communication and increasing the value of the user segment. Therefore, initially, most satellite communication systems provided mainly fixed satellite communications (communication between stationary objects), and only with the introduction digital methods communications and the launch of non-geostationary spacecraft, mobile satellite communications have been widely developed. Note that modern mobile satellite communication systems are, firstly, compatible with traditional terrestrial mobile communication systems (primarily with digital cellular), and, secondly, the interaction of mobile satellite radio networks with the public telephone network is possible at any level (local, intrazone, long distance).
The main global mobile satellite communications operators known in Russia
Iridium system (international consortium Iridium lls, Washington). The Iridium global mobile personal satellite communication system was intended to provide communication services with mobile and fixed objects located throughout the globe. The space segment of the system consisted of 66 main (orbit height 780 km above the Earth's surface) and 6 backup satellites (645 km). The system provided subscribers with the following services: voice transmission (2.4 Kbps), data transmission and telefax at the same speed, personal call and location determination.
Being a very expensive project (more than 5 billion dollars), Iridium set ultra-high prices for terminals and traffic at the initial stage of development, erroneously targeting only very rich consumers of the service. In addition, technical and financial problems unforeseen by the project arose during operation, which led the consortium to bankruptcy.
Globalstar system (Globalstar ltd., San Jose, California). The system of global mobile personal satellite communications "Globalstar" is designed to provide communication services with mobile and fixed objects located on the globe between 700 * north latitude. and 700* S
Portable terminals of the "Globalstar" system are produced in several modifications to ensure the possibility of their use both for organizing communication in the "Globalstar" system and in networks of terrestrial cellular communication of the GSM, AMPS, CDMA standards.
The space segment of the system is a constellation of 48 main and 8 standby satellites, weighing less than 450 kg, placed in circular orbits at an altitude of 1414 km above the Earth's surface. The first generation satellites are designed to operate in full load mode for at least 7.5 years.
To cover the populated territory of the globe, it is planned to build about 50 interface stations, providing maximum coverage (up to 85%) of the earth's surface with the space segment of the system. At the first stage of system development, 38 interface stations were built. There are 3 such stations in operation in Russia: in the Moscow region (Pavlov Posad), in Novosibirsk and in Khabarovsk. These stations provide mobile services with high quality service almost throughout Russia south of 700 N.S. Each of these stations is connected to the Russian public network. The Globalstar system has been in operation in Russia since May 2000.
ICO system (international company ICO Global Communications). The system of global mobile personal satellite communications "ICO" is designed to provide communication services with mobile and fixed objects throughout the globe, including polar regions. The company "ICO Global Communications" was established on the initiative of the international organization "INMARSAT". It is a truly international organization. None of the countries plays a dominant role in it. More than 60 companies around the world are ICO investors.
It is planned that the ICO system will work in conjunction with cellular communication systems, providing services to regions and zones not covered by cellular radio communication systems. According to the project, most of the subscriber terminals of the ICO system will be personal pocket telephones capable of operating in two modes (satellite/terrestrial cellular). The estimated cost of the subscriber terminal of the ICO system is $1,000, one minute of traffic is $1.
The space segment of the system will be represented by a constellation of 10 main and 2 backup satellites in the MEO orbit at an altitude of approximately 10,390 km above the Earth's surface.
A feature of this system will be a specially formed network "IcoNet", which will connect twelve satellite access nodes (SAN) located around the world with "intelligent" communication lines, and will provide a quick connection of public networks with mobile terminals and mobile terminals to each other, regardless from their location. On the territory of Russia, it is planned to build one USD. The infrastructure of the terrestrial segment of the ICO system is based on the proven architecture of GSM networks, as well as standard components used in large quantities to ensure the compatibility of the ICO system with other terrestrial cellular communication standards.
The ICO system plans to provide users with the following types of services: teleservices, transport environment services, services provided in the GSM system, messaging and roaming services.
Teleservices will provide such services as: digital telephony, emergency calls, group 3 fax transmission at speeds up to 14.4 kbps and short message services. At the same time, digital telephony will ensure the quality of voice transmission, like that, which is provided by existing land mobile radio standards.
In addition, the ICO system plans to provide services for the transmission of low-speed transparent and non-transparent data in asynchronous mode at speeds of 300, 1200, 2400, 4800 and 9600 bps and transparent data in synchronous mode at speeds of 1200, 2400, 4800 and 9600 bps. /With.
Due to the financial problems of the consortium, it was decided to merge ICO Global Communications with Teledesic Corporation, which would delay the start of services until 2003. One USD on the territory of Russia is supposed to be built by the same date. It is expected that 450,000 subscribers will use the ICO system in Russia.
System INMARSAT(company «INMARSAT ltd.», London). INMARSAT owns satellites installed in geostationary orbit at the following positions: 54*W, 15.5*W, 64.5*E, 178*E. This provides an almost global connection between 75 * S.l. and 75* s.l.
More than 50 earth stations operate in the INMARSAT system, providing communication with mobile equipment installed on sea and river vessels, drilling platforms, aircraft, vehicles (practically none in Russia), in business cases.
The following types of mobile stations are used: "INMARSAT-A", "INMARSAT-B", "INMARSAT-M", "INMARSAT-mini-M", "INMARSAT-C", "INMARSAT-D +" (pager with answer), " INMARSAT-aero" ( various types). The listed types of stations have different physical and electrical characteristics, which determines a large difference in the price of stations, the tariff for communication and its quality (information transfer rate, voice transmission quality).
Currently, about 170 thousand stations of all types operate in the INMARSAT system, of which about 10 thousand have Russian numbers (are Russian).
ORBCOM system (ORBCOM Global, Dallas, Virginia). The ORBCOM communication system is intended for two-way data transmission and object location determination using low-orbit artificial Earth satellites (from 28 to 48 satellites). Data transmission on the satellite-to-Earth line is carried out at a speed of 4.8 Kbps, and on the Earth-to-satellite line - 2.4 Kbps. The system was developed in the USA by ORBCOM Global to meet the needs for information exchange with areas remote from the existing terrestrial telecommunications infrastructure.
The main drawback of the system is the lack of a telephone service.
News from global satellite operators
One of the most sensational and well-known projects of global satellite communications is the project of the Iridium concern. In November 2000, the US Bankruptcy Court transferred control of Iridium to a venture capital firm. As a result, this seemingly long-lost company was awarded a $72 million project to equip the US Department of Defense with mobile satellite communications. This is all the more interesting because the tender was won against another large and most dynamically developing operator at the moment - the Globalstar company.
This year was generally unsuccessful for Globalstar (despite receiving a large order for equipping bus handsets in Brazil and launching the system in Russia). It began with the refusal of the main shareholders ("Loral Space & Communications Ltd" and "QUALCOMM"), from further participation in the Globalstar projects. However, a little later, the much needed $183 million was found, and the company continued its activities. In November, Globalstar announced its results for the third quarter of 2000. The company's revenues amounted to $1.4 million, losses - $97.5 million. Compared to the same period in 1999, the company's losses per share increased almost five times and amounted to $1 per share (in 1999 - 20 cents per share). share). At the end of the third quarter, the company served 21,300 subscribers, twice as many as at the end of the second quarter of 2000. The company's management believes that this is extremely small for the successful operation of the global satellite communications system, but on the whole evaluates the project as viable and claims that the company has the financial resources necessary for its activities until the end of May 2001.
At the same time, Globalstar's losses did not lead to a deterioration in the financial position of its major shareholder, QUALCOMM (a supplier of satellite data transmission systems, which is a competitor in this business to ORBCOMGlobal with services such as Trackmaile-, "Omni-track" and "Euteltrack"). This was mainly due to other projects of the concern. QUALCOMM owns major technology patents wireless communication CDMA standard, on 3G WCDMA technology ( mobile connection third generation, the standard was developed by European companies), on 3G technology of the cdma2000 standard (the standard was developed by QUALCOMM).
American Mobile Satellite Corp continued its course of developing fleet management communication services and data transmission systems over its ARDIS terrestrial network.
Japanese company NTT DoCoMo provides communications services for the national fleet. The Australian company "Optus" serves more than 9,000 subscribers. The European EMCAT network offers a full range of mobile services, while the Belgian mobile satellite network IRIS provides satellite data transmission.
The project of ICO Global Communications has been suspended. The commissioning of the system is scheduled for no earlier than 2003.
On October 20, 2000, Boeing Satellite Systems successfully launched the Thuraya 1 satellite as part of its own mobile satellite communications deployment project, which is expected to cover the Middle East, North and Central Africa, Europe, Central Asia and India (number of residents - up to 1, 8 billion people).
Mobile satellite operators in Russia. INMARSAT
After the termination of the activities of the Iridium company, two mobile satellite communications operators remained in Russia: INMARSAT and Globalstar.
The INMARSAT system was created in 1979 in the USSR to establish satellite communications with sea vessels and ensure the safety of navigation. INMARSAT currently manages a global satellite constellation that is used to provide voice, facsimile, telex and multimedia communication services to mobile users. Satellites of the INMARSAT system are located in geostationary orbit. Guaranteed communication is provided on average from 70°S. up to 70° N Each satellite covers approximately one third of the Earth.
However, although the INMARSAT system has quite a few subscribers in Russia, it cannot be said that its use is widespread. The main reason is the high price of user terminals and the high tariff for communication. For example, the tariff for 1 minute of telephone communication when using various types of subscriber stations is: for "INMARSAT-A" - about 6.0-6.5 dollars, for "INMARSAT-B" - about 4.0 dollars, for "INMARSAT- mini-M" - about 2.5 dollars, for "INMARSAT-aero" - about 6.0-6.5 dollars. The cost of terminals ranges from $3,000 to $15,000. So, the most common standard "INMARSAT-mini-M" has the dimensions of a "laptop", weight is about 2 kg, price is $3000.
Models of satellite portable terminals of the "INMARSAT-mini-M" type, available for sale in the Russian Federation
Figure 3.TT-3060A
Mobile phone TT-3060A of the INMARSAT satellite system is designed to transmit telephone and facsimile messages, data and e-mail. Built-in battery and voltage converter provide non-volatile operation for 48 hours in standby mode and 2.5 hours in talk mode. The handset, 2-wire RJ-11 fax connector, and a Hayes-compatible 2.4Kbps data port have personal phone numbers(total number - 4). The ability to protect against unauthorized access is provided by the built-in SIM card reader. It is possible to connect STU-IIB/STU-III cryptographic equipment and use image transfer software. Magnesium alloy body weighing less than 2.2kg.
Rice. 4. World Phone Hybrid
WorldPhone Hybrid provides access to the international telephone network with the ability to send faxes, data and Email. Key Features: 4.8Kbps Voice, 2.4Kbps Fax, 3 Hour Talk Time, Backlit LCD Display, Speakerphone, Short Message Service (SMS), Voice/Fax Mail, Call Forwarding, Notebook.
Mobile satellite operators in Russia. "Globalstar"
Subsidiary GlobalTel (a joint venture between Globalstar and Rostelecom) began to provide its services on the territory of the Russian Federation in May 2000. At the moment it is telephony (voice transmission) and call forwarding. The following services are also provided in the system, but have not yet been implemented: data transmission, facsimile communication, transmission and reception of short messages, global roaming, location determination, voice mail, call emergency services.
The space segment includes a constellation of 48 low-orbit (and 4 standby) satellites providing coverage from 70°N. up to 70° and placed by 6 satellites in 8 circular orbits at an altitude of 1414 km. The system of low-orbit satellites makes it possible to drastically reduce the cost of a subscriber terminal and a minute of conversation.
The user segment consists of portable mobile and stationary terminal devices. Devices can work in several modes (up to three). Dual- and tri-mode devices, in addition to accessing the Globalstar system, can also be used to access terrestrial cellular networks in GSM, AMPS, CDMA standards..
Prices for subscriber terminals: mobile $1000-1900 (depending on the manufacturer), stationary - from $3000. Tariff for 1 min. outgoing traffic within Russia — $1.2-2.0 (including the public network tariff).
Models of satellite portable mobile terminals available on the Russian market that support Globalstar services
Rice. 5. Ericsson portable subscriber mobile terminal
Dual mode Ericsson terminal. The contract for the production of handsets also includes the supply of car and / or stationary subscriber terminals. Working hours - Globalstar | GSM. Dimensions mm - 160 × 60 × 37. Weight - 350g. Talk time Globalstar /GSM hours - ?. The standby time of Globalstar /GSM hours is 5/36.
Rice. 6. Portable subscriber mobile terminal Telit
Telit terminal provides communication in Globalstar modes | GSM and has the following characteristics: dimensions mm - 220 × 65 × 45; weight - 300g; talk time Globalstar /GSM hours - ?; standby time Globalstar /GSM hours - 36/36.
Rice. 7. Qualcomm portable mobile subscriber terminal
Qualcomm Tri-Mode Terminal - Globalstar | AMPS | CDMA. Dimensions mm - 178 × 57 × 44. Weight - 357g. Talk time Globalstar /APMS/CDMA hours - 1/1/3. Standby time Globalstar /AMPS/CDMA hours is 5/7/25. Display 4×16 characters, address book for 99 numbers, fast auto redial, voice mail, message reception, caller ID.
Conclusion
At the moment, despite certain failures (the bankruptcy of the Iridium concern, the suspension of the ICO project, the losses of Globalstar), mobile satellite communications have occupied their (what?) Segment of the global communications market. Sales of user terminals are steadily growing, the number of telecom operators is increasing (satellite launches by Boeing, development of a new generation of small satellites by Intersputnik), and investor interest is not weakening. At the same time, it is necessary to constantly monitor developments in this market segment and keep a “hand on the pulse” so that users of mobile satellite phones in Russia do not find themselves in a situation similar to the one that developed in Russia with the termination of the Iridium concern, when the owners did not know what to do with the pipes, which in an instant turned into a pile of iron. Let's hope that in the foreseeable future such serious cataclysms will not repeat, and the cost of user terminals and traffic will gradually equal the cost of conventional cellular communications.
In contact with
Classmates
