Modern satellite communications satellite systems. Project "Modern Satellite Communication"

Main satellite.Initially, the emergence of satellite communications was dictated by the needs of transmitting large amounts of information. Intelsat system was the first satellite communication system, then similar regional organizations were created (Eutelsat, Arabsat and others). Over time, the proportion of speech transmission in the total volume of the main traffic has been constantly declining, giving way to data transfer.

With the development of fiber-optic networks, the latter began to push out satellite communications from the main communication market.

VSAT systems.VSAT (Very Small Aperture Terminal) is a small satellite ground station, that is, a terminal with a small antenna is used in satellite communications since the beginning of the 90s. VSAT systems provide satellite communications services to customers (usually small organizations), which do not need high channel bandwidth. The data transfer rate for the VSAT terminal usually does not exceed 2048 kbps.

Figure 3.14 - VSAT system

Consumers of the Russian VSAT market can be divided into four segments:

1. Public institutions 2. Large corporations with an extensive network of branches and representative offices. 3. Middle and small regional business. 4. Private users.

The words "very small aperture" refer to the size of the terminals antennas compared with the size of older antennas of the main communication systems. VSAT terminals operating in the C-band typically use antennas with a diameter of 1.8-2.4 m, in the KU-band - 0.75-1.8 m. Antenna is shown in Fig. 3.9.

In VSAT systems, the technology of providing channels on request is applied.

The VSAT satellite communications network includes three main elements: a central earth station (if necessary), a satellite repeater and subscriber VSAT terminals (Fig.3.14).

The central earth station on the satellite communications network performs the functions of the central node and ensures the management of the work of the entire network, the redistribution of its resources, identifying malfunctions, tariffing network services and interface with ground lines of communication. Usually the CCC is installed in the network node, which accounts for the greatest traffic. This may be, for example, the main office or computing center of the company in corporate networks, or a major city in the regional network.

Types of control. With a centralized management of such a network, the network management center (TSUS) performs service control and control functions necessary to establish a connection between network subscribers, but does not participate in traffic transmission. Usually, the TSUS is installed on one of the subscriber stations of the network, which accounts for the greatest traffic.

In a decentralized version of the network management, the TSUS is missing, and the elements of the control system are part of each VSAT station. Similar networks with a distributed control system are distinguished by increased "vitality" and flexibility due to the complication of equipment, expanding its functionality and higher prices of VSAT terminals. This control circuit is appropriate only when creating small networks (up to 30 terminals) with high traffic between subscribers.

Subscriber station VSAT Subscriber VSAT Terminal typically includes an antenna feeder device, an external external radio frequency unit and an internal block (modem). The external block is a small transceiver or receiver. The internal unit provides a satellite channel pairing with terminal user equipment (computer, LAN server, telephone, fax PBX, etc.).

Satellites VSAT network repeaters are built on the basis of geostationary repeater satellites. This allows you to simplify the design of subscriber terminals and supply them with simple fixed antennas without a satellite tracking system. The satellite takes a signal from the earth station, enhances it and sends back to the ground. The most important characteristics of the satellite are the power of onboard transmitters and the number of radio frequency channels (trunks or transponders) on it. To ensure work through small-sized subscriber stations of type VSAT, transmitters are required with an output power of about 40 W. Modern VSATs work as a rule in KU the range of 11/14 GHz frequency range (one frequency value for reception, other transmission), also have systems using a range of 4/6 GHz, also now masters a range of 18/30 GHz.

Modern vsat have one or more Ethernet ports and built-in router functions. Some models, by expansion, can be equipped with 1-4 telephone ports.

Satellite modem. DVB Map - Extension Computer Board, designed to receive data from a satellite, a kind of "satellite modem". It can be with a PCI, PCI-E or USB interface, the selection depends on what you are more convenient to connect to a computer.

The DVB card is installed in a free PCI slot or USB port of the computer and is connected by a coaxial cable to the satellite antenna converter, that is, performs the functions of the classic satellite receiver and transmits the received data to other components nodes. In general, the installation process and configuration of the DVB card is no different from the installation of any other device.

Basic VSAT manufacturers in the world:

Codan (Australia);

Hughes Network System (USA) - Hughesnet (DIRECWAY), HX;

Gilat (Israel) - Skyedge;

Viasat (USA);

iDIRECT (USA);

NdSatcom (Germany).

Typical value VSAT for the final customer is about 2500..3000 US dollars.

Brief list of VSAT services:

Internet via satellite

Distance learning

Rural communications

Telemedicine

Emergency service

Closed groups of users of public services

National and multinational networks

Broadband data transfer

Broadcast services

Government and corporate organizations

PSTN infrastructure expansion services

Collective Internet access

Figure 3.15 - DVB Map (PCI) TT-BUDGET S-1401

Mobile satellite communication systems.Mobile phone owners with all their capabilities can only ring where mobile communications stations are equipped. And what to do where there are no such stations? Exit only one - use satellite telephones, giving the opportunity to call almost anywhere in the world. As it is clear from the name of the communication, the connection is not taken through ground stations, but through satellites located at an near-earth orbit.

Satellite phone - Mobile phone transmitting information directly through a special communication satellite. Depending on the telecom operator, the coverage area may be or all the land, or only individual regions. This is due to the fact that either low-fat satellites are used, which, with sufficient quantities cover the coverage area all the land, or satellites on a geostationary orbit, where they do not move relative to the Earth and do not "see" it completely.

By size satellite telephone, we compare with the usual mobile phone released in the 1980s-1990s, but usually has an additional antenna. There are also satellite telephones in the stationary performance. Such phones are used to communicate in areas where there is no cellular communication.

Satellite telephone numbers usually have a special country code. Thus, in the INMARSAT system uses codes with +870 to +874, in iRidium +8816 and +8817. To date, satellite communications are presented in the world with various systems with their advantages and disadvantages. As for Russia, the Inmarsat, Turayia, Globalstar and Iridium systems are available on its territory.

Inmarsat (Inmarsat) is the first and so far the only mobile satellite operator offering all the services of a modern satellite connection on water spaces, on Earth and in the air.

Figure 3.16- Inmarsat Telephone

Turayia(Thuraya) is a mobile satellite connection that covers one third of the globe and offering inexpensive calls to its subscribers with a price from $ 0.25 per minute of the outgoing call and free incoming (by satellite).

Figure 3.17 - Thuraya satellite phones

Turay satellite phones are combined with cellular, in which there is a GPS receiver, which determines the location with an accuracy of up to 100 meters. Communication is available on 1/3 of Russia.

Globalstar(Globalstar) is a new generation satellite.

Figure 3.18 - Globalstar satellite phones

Globalstar provides telephone communications in those areas of the villages, where it was previously not possible at all or were serious restrictions in its use and makes it possible to call or share data in almost any area of \u200b\u200bthe planet.

Iridium(Iridium) - provides a wireless satellite network providing telephone everywhere and always. Communication from Iridium covers the entire surface of the Earth. In Russia, the Iridium network is available throughout, but so far on the license to provide services in the territory of the Russian Federation.

A feature of most mobile satellite systems is a small size of the terminal antenna, which makes it difficult to receive a signal.

In order for the power of the signal reaching the receiver, is sufficient, apply one of two solutions. Satellites are located on a geostationary orbit.

Figure 3.19 - Iridium satellite phones

Since this orbit is removed from the ground to a distance of 35786 km, the satellite requires a powerful transmitter. This approach is used by the INMARSAT system (the main task of which is the provision of communication services by sea ships) and some regional personal satellite telecommunication operators (for example, Thuraya).

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

Cellular operators compete with personal satellite operators. It is characteristic that both Globalstar and Iridium experienced serious financial difficulties that Iridium brought to the reorganization bankruptcy in 1999.

In December 2006, the experimental geostationary satellite of Kiku-8 was launched with a record-wide range of antenna, which is supposed to be used to work out the technology of satellite communications with mobile devices not exceeding cell phones.

Figure 3.20 - mobile circuit

Principles of organizing mobile satellite communications. In order for the signal power reaching a mobile satellite receiver, it is sufficient to use one of two solutions:

1. Satellites are located on a geostationary orbit. Since this orbit is removed from the ground to a distance of 35786 km, the satellite requires a powerful transmitter.

2. Many satellites are located on inclined or polar orbits. At the same time, the required power of the transmitter is not so high, and the cost of outputting the satellite into orbit is lower. However, this approach requires not only a large number of satellites, but also an extensive network of ground switches.

Client Equipment (Mobile Satellite Terminals, Satellite Phones) interacts with the outside world or otherwise via a repeater satellite and stations of pairing a mobile satellite service operator, providing connection to external ground communication channels (general telephone network, Internet, etc.)

Satellite Internet.Satellite communications is used in the organization "Last Mile" (communication channel between the Internet provider and the client), especially in places with a poorly developed infrastructure.

The features of this type of access are:

The separation of incoming and outgoing traffic and attracting additional technologies to align them. Therefore, such compounds are called asymmetric.

Simultaneous use of the incoming satellite channel by several (for example 200 mi) users: through the satellite simultaneously transmitted data for all customers "Interest", the client terminal is being filtered (for this reason, "fishing from the satellite" is possible).

By type of outgoing channel, distinguish:

Terminals working only on receiving the signal (the cheapest connection option). In this case, for outgoing traffic, you must have another Internet connection, the supplier of which is called the ground provider. To work in such a scheme, tunneling software is attracted, usually included in the terminal delivery. Despite the complexity (including the complexity in the setting), such a technology is attractive to high speed compared to the Dial-Up for a relatively small price.

Receiving transmitting terminals. The outbound channel is organized narrow (compared to the incoming). Both directions provide the same device, and therefore such a system is much easier to configure (especially if the terminal is external and connects to the computer via the Ethernet interface). Such a scheme requires installation on an antenna of a more complex (receiving-transmitting) converter.

In both cases, the data from the provider to the client is transmitted, as a rule, in accordance with the DVB digital broadcast standard, which allows using the same equipment for both access to the network and for receiving satellite television.

Disadvantages of satellite communications:

1. Weak noise immunity. The huge distances between the earth stations and the satellite are the reason that the signal-to-noise ratio on the receiver is very small (much less than for most radio relay communication lines). In order to provide an acceptable probability of error in these conditions, you have to use large antennas, low-noise elements and complex noise-resistant codes. Especially acute this problem is in mobile systems, as they have a limit on the size of the antenna and, as a rule, the transmitter power.

2. The effect of the atmosphere. The quality of satellite communications have a strong effect effects in the troposphere and ionosphere.

3. Absorption in the troposphere. The tomb of the signal is atmosphere depending on its frequency. The absorption maxima occurs by 22.3 GHz (resonance of water vapor) and 60 GHz (oxygen resonance). In general, the absorption significantly affects the spread of signals with a frequency above 10 GHz (that is, starting with the KU-band). In addition to the absorption, when distributing radio filters in the atmosphere there is a fading effect caused by which the difference in the refractive indices of various layers of the atmosphere.

4. Ionospheric effects. Effects in the ionosphere are due to fluctuations of the distribution of free electrons. The ionospheric effects affecting the propagation of radio waves include flickering, absorption, propagation delay, dispersion, change in frequency, rotation of the polarization plane. All these effects are weakened with increasing frequency. For signals with frequencies, large 10 GHz, their influence is small. Signals with a relatively low frequency (L-range and partially C-range) suffer from ionospheric flicker resulting from heterogeneity in the ionosphere. The result of this flicker is the constantly changing signal power.

5. Signal propagation delay. The problem of delaying the signal propagation is somehow affecting all satellite communication systems. Systems using a satellite repeater on geostationary orbit have the greatest delay. In this case, the delay due to the limb of the radio wave speed limit is approximately 250 ms, and taking into account the multiplexing, switching and signal processing delays, the overall delay can be up to 400 ms. The distribution delay is most undesirable in real-time applications, for example, in telephone communication. At the same time, if the signal distribution time on the satellite communication channel is 250 ms, the time difference between the replicas of subscribers cannot be less than 500 ms. In some systems (for example, in VSAT systems using the Star Topology), the signal is transmitted twice through the satellite communication channel (from the terminal to the central node, and from the central node to another terminal). In this case, the overall delay is doubled.

6. The effect of solar interference. When the sun approaches the satellite axis, the ground station radio station received from the satellite ground station is distorted as a result of interference.

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

Satellite communications technology allow you to use one or more repeaters to provide high-quality radio transmission over long distances.

All repeaters can be divided into two categories:

• passive. Currently practically not used. Initially used exclusively as a gear ratio between the ground station and the subscriber did not enhance the signal and did not transform it;


• active. Such devices additionally enhance the signal and correctly adjust before sending it to the subscriber. Most world satellite systems use just such a type of repeaters.

History of satellite communications

At the end of 1945, the world saw a small scientific article, which was devoted to the theoretical possibilities of improving communication (first of all, the distance between the receiver and the transmitter) due to the raising antenna to the maximum height.

What principle of work was meant?

Everything is quite simple - the scientist suggested to bring a large re-repeater antenna that would take signals from the ground source and transmit it further.

The main advantage was a huge coverage zone that only one satellite could control. This would significantly increase the quality of the signal, would remove the limit from the number of host stations and would additionally would not have to build ground repeaters. The United States became interested in the project as part of solving problems with transatlantic telephone communications.

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

Later, key satellite communications standards were developed (working frequency ranges), which are widely used throughout the world.

Scope of satellite communications

From the moment of successful implementation, the quality of satellite communications has grown significantly.

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

The use of satellite communications can be divided into several conditional directions:

• main link. Initially, the task was put in transmitting a large amount of information (in particular, voice messages), but over time, when switching to a digital format, such a need forged and today from this area, satellite communications displaces optical fiber networks;


• Vsat. The so-called "small" systems with an antenna diameter up to 2.4 meters. The technology is successfully developed, and serves to create private communication channels;


• mobile connection (the basis of telephony and television);


• access to the Internet.

For more information about the development of this direction of communication, it is sufficient to visit the profile event. The international exhibition "Communication", which runs on the territory of the Expocentre Fair, is the best sectoral event of the international level. This guarantees the availability of a wide exposition and participation of well-known world and domestic specialized companies.

How the equipment works modern satellite communications

Satellite bond is firmly associated in the consciousness of many people with GPRS navigators and telephony. In essence, this invention of humanity and finds its niche in these areas from the point of view of ordinary people.

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

It is due to the fact that modern satellite communications has such a wide coverage, the ability to make calls from the most remote corners of the world has become real. No serious tourist risk take a distant and dangerous journey without a satellite phone.

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

Using the resources and capabilities of satellite information, a variety of navigators for various industries have been created.

In fact, the modern satellite bond consists of only three elements: transmitter, repeater and receiver. The role of the transmitter and receiver performs various devices: mobile phones, computing machines, antennas and so on.

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

For greater bandwidth of the repeater, the following multiple access systems were introduced (MD):

1. MD with frequency division. Each user receives its frequency.


2. MD with temporary separation. The user has the right to receive or transmit data only at a certain period of time.


3. MD coded division. Each user is issued code. It is superimposed on the data so that the signals of various users are not mixed even when transmitted at one frequency.

In general, all the above systems guarantee repeated frequencies, which increases efficiency and bandwidth.

When transferring information, the absorption of waves in the atmosphere and the size of the receiving antenna - for each specific case, uses its frequency.

International satellite communications

International satellite communications - This is a type of radio relay communication, which is based on the use of artificial satellites of Earth, as repeaters. Communication occurs between stations located on Earth, which in turn is stationary and movable. The technology allows you to transfer a radio signal at any distance, even the most ample.

To date, the most common type is an active repeater. It enhances significantly and adjust the incoming signal before it comes to the subscriber. Most of the satellite systems of the world use just such a type of satellites.

The beginning of this technology was made by the English scientist Artur Clark, who wrote an article "extraterrestrial repeaters." The principle was that the antenna had to withdraw to the longest distance at the near-earth orbit, which would allow to receive signals from ground sources and transmit them further. The main feature was that one satellite could control a rather large coverage area of \u200b\u200bthe globe.

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

Applications of international satellite communications

From the moment the first artificial satellite was launched into space, the quality of technology has improved significantly. Today, humanity does not represent everyday life without a mobile phone (which victoriously suppressed homeproof), without video chats, helping to communicate with a person in real time, without television, etc.

The modern use of international satellite communications shares the following key areas:

• main Communication;


• mobile satellite communication system;


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


• mobile network;


• The Internet (with the help of this system, the majority of modern technologies).

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

Thematic diversity covers all categories of a coherent industry:

• internet technologies;


• software;


• networks for data transmission;


• startups;


• telecommunication infrastructure;


• services in the field of IT technologies;


• connector equipment and modern technologies.

The possibilities of modern international satellite communications

Modern high-tech international satellite communications provides opportunities:

• share information;


• manage and coordinate air and sea vessel, as well as land transport;


• the ability to transmit large amounts of information to another edge of light;


• receive high and stable signal quality;


• safety communications, etc.

New satellite communications of the Russian Federation

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

Today, the formation of a market segment of satellite communications is unimaginable without a message with a ground network system. Any changes in the network structure can thoroughly affect the quality of satellites.

Satellite communications has the following latest innovations:

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


• vSAT antenna stations distribution (Very Small Aperture Terminal);


• improving the energy armament of spacecraft and their ability to skip remote signals from the points of the Earth;


• satellites wide range of action, equipped with a repeater;


• funds with large frequency ranges;


• mastering the orbits of medium height.

All these innovative devices led to the ability to process a set of signals in space through radial switches.

Thanks to the latest video transmission transmission mechanisms, free online communication has become familiar for this time.

Market segments of satellite communications of the Russian Federation

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

1. The first segment is based due to the combination of ground stations in the state with developing in the positive dynamics of Global Star, Inmarsat, Ellipse satellite complexes. Of these, compact personal communication terminals are formed, conjugate with mobile devices of television and radio broadcasting. Satellites of the system are localized over the oceans for high-quality supplies with Internet signals of large radii. The system has a telephone that is configured to one of the satellites. Communication terminals with large antennas capture the signal and distribute it to subscribers anywhere in the Earth.


2. The second segment was focused on the production of small satellite terrestrial terminals (VSAT) intended to form corporate networks with protected access. Now in the territory of the Russian Federation, according to the National Satellite Union of Satellite Communications, there are such stations about 3.2% of the total in the world (500 thousand).


3. The third segment is invented and implemented in the production of satellites, a small format stations and their systems, which cause broadcasting, remote online communications. The cost of equipment for this market niche is at times below the terminals of the previous two segments. Given the geographical advantage of small settlements regarding the entire area of \u200b\u200bthe country, television infrastructure brings maximum profits among all types of contacts.

The Russian communication market is important for the economic development of the zone, where signals are processed by multi-mode terminals.

The RAT Remote Control Signal (Remote Administration Tool) is divided into codes in CDMA (Code Division Multiple Access) and scanning makes it easier to conduct search calls in cycles interconnected into a separate Rat. With these areas, it is advantageous to report places where there is no reception of a cellular signal.

Multi-mode terminals of wireless subscribers are able to increase the efficiency of firewalk, increase access to different services.

Modern equipment for the reception and transfer of satellite communications at the exhibition

Modern satellite communications He serves as a remarkable way to transfer information, but put forward increased requirements for equipment.

Exhibition "Communication" Provides the opportunity to get acquainted with the latest developments and suggestions from various satellite equipment manufacturers.

A wide range of samples of various price categories is set up in the "Expocentre" walls, so anyone can find the most optimal option in terms of quality and price.

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

Read the other our articles:

2.1 VSAT (Very Small Aperture Terminal)

The VSAT station is a satellite connection station with an antenna small diameter, about 1.8 ... 2.4 m. The VSAT station is used to exchange information between land points, as well as in data collection and distribution systems. SCCs with a network of VSAT type stations provide a telephone connection with digital speech transmission, as well as digital information transmission. When transmitting telephone traffic, satellite systems form group tracts (a set of technical means providing the passage of the group signal, i.e. Several telephone subchannels are combined into one satellite) and transmission channels (a set of means that ensure the transmission of signals from one point to another).

Channels and group tracts of the SCC are widely used in the plug-in and intra-zone telephone networks. In some cases, at the local communication lines of the SCCs allow: to organize direct fixed channels and paths between any connection points in the service area of \u200b\u200bthe USS. And also work in mode of loose channels, in which satellite channels and paths can quickly switch from some directions to others when changing the needs of traffic on the network, as well as the most efficient - complete bunches.

To date, several CCCs have been created using VSAT. One of the typical systems of this kind is a system organized on the basis of geostationary satellites. VSAT, working as part of this system, is established in a number of countries, including in Russia.

An attractive feature of VSAT stations is the ability to place them in close proximity to users, which, thanks to this, can do without landline lines.

In addition to systems with a fixed channel, effective in constant transmission of high speeds (10 kbps and more), there are systems using a temporary, frequency, code or combined channel separation between many subscriber CS.

Another parameter that allows you to classify the SCC, is the use of the protocol. The first satellite systems were missing and offered to the user a transparent channel. The disadvantage of such systems was, for example, the transfer of user information without, as a rule, confirming its delivery by the receiving party. In other words, the rules of the dialogue between the participants of the exchange of information are not stipulated in such systems. In this case, the quality of the CSS is determined by the quality of the satellite channel. With typical values \u200b\u200bof the probability of the error on the character within 10-6..10-7, the transfer of large files through satellite systems, even using various noise-resistant codes is difficult, if not to say that it is impossible.

The VSAT satellite station according to a constructive feature consists of a high-frequency (ODU) and low-frequency (IDU) module. ODU, consisting of an antenna and transceiver, is located outside the building, in which an IDU is installed, consisting of a modem and a multiplexer (channel-forming equipment).

The standard version of the configuration includes a parabolic antenna of a small diameter and a receptionist. Depending on the location of the satellite station in relation to the center of the satellite lighting zone and transmission rates in the channel, more powerful transmitters or larger diameter antennas are used. The room is installed modem and multiplexer. ODU and IDU are interconnected by radio frequency (RF) cables. There is an intermediate frequency (IF) signal. If there is 70 or 140 MHz.

External block. Outdoor, or how it is sometimes called the high-frequency block, consists of an antenna and a transceiver block that is installed on this antenna. The transceiver unit provides a low-frequency signal conversion, gain and "up". Also receiving a high-frequency signal from the satellite to its conversion to low-frequency and transmission to the inner block. Antenna. The single-siene antenna is usually performed according to the offset (with a shifted center). The offset scheme reduces the level of lateral petals going parallel to the Earth and giving maximum interference. Also, this scheme avoids the accumulation of atmospheric precipitation on the surface of the reflector. communication satellite digital signal

Antenna consists of:

• * reflector (mirrors);
• * irradiation systems;
• * Rotary base (OPO).

The main terminal consists of:

• * Microwave frequency conversion unit;
• * Power amplifier (SSPA or TWT);
• * low-noise converter (LNC);
• * Power unit (PS);
• * connecting cables.

The transceiver function is to convert, after the modulator, the IF signal, on the converter up, in the RF signal for transmission through the antenna and in converting the received RF signal into the IF signal, on the converter down, for the block used as a demodulator.

Internal block. The internal block is a 19 "rack with a satellite modem and multiplexer installed in it. Sometimes an additional equipment is installed in the rack, fans, UPS, etc. UPS can be installed outside the rack, separately.

Satellite modem. The satellite modem, in the portion of the modulator is intended for encoding the transmitted digital stream, which came from the multiplexer, modulating the IF signal, the necessary amplification and transmission of the signal to the external unit. And receiving an IF signal from an external block, enhancing it, demodulating into a digital signal, decoding and transmission to a multiplexer, in a demodulator part.

Multiplexer. The multiplexer is designed for multiplexing voice, fax information and data transmitted. The multiplexer allows you to combine daily telephone and fax messages with synchronous and asynchronous data transmission to one channel, betrayed by local networks, ground or satellite lines. This reduces telecommunication costs by increasing the possibilities of transmitting important information and simultaneously reduced channel bandwidth.

Satellite gateway. Satellite gateways are used to access network telecommunications (large stations to which are connected via the VSAT station satellite).

The gateway can provide:

• * access to telephone networks;
• * long-distance services with access to a common network;
• * services of international telephone;
• * access to special telephone networks, such as "Iskra-2";
• * Exit data network (Rosnet, Internet, Relcom, etc.);
• * Ability to rent a ground canal to any point.

High-speed output on the Internet and other data networks.

The gateway allows you to provide high-speed output on the Internet, up to 2 Mbps. In this embodiment, it is possible to access all Internet services (WWW, TELNET, E-Mail, FTP, etc.). All described above also applies to other global data networks. VSAT is a small satellite base with an antenna diameter of 0.9 - 3.7 m, designed mainly to reliably exchange data on satellite channels. It does not require maintenance and connects directly to the terminal equipment of the user, performing the role of a wireless modem.

How the VSAT network works. The VSAT satellite communications network includes three main elements: central earth station (if necessary), satellite repeater and subscriber VSAT terminals.

Central earth station (CCC). The central earth station in the satellite communications network on the database performs the functions of the central node and ensures the management of the work of the entire network, the redistribution of its resources, identifying malfunctions, network service bargaining and interface with ground lines. Usually the CCS is installed in the network node, which accounts for the greatest traffic (Fig.16).

The channel-forming equipment ensures the formation of satellite radio channels and docking them with ground lines. Each of the satellite communications suppliers applies its original solutions to this part of the CCC, which often eliminates the possibility of using equipment and subscriber stations of other firms to build a network. Usually, this subsystem is based on a modular principle, which allows the traffic and number of subscriber stations in the network to easily add new blocks to increase its bandwidth. The network management center provides control over the operation of the network, identifying malfunctions, the redistribution of its resources between subscribers, the billing of the services provided, etc.

Subscriber station VSAT. Subscriber VSAT Terminal typically includes an antenna-feeder, an external external radio frequency unit and an internal unit (modem). The external block is a small receiving transmitter or receiver. The internal unit provides a satellite channel pairing with terminal user equipment (computer, LAN server, telephone, fax PBX, etc.).

Satellite repeater. VSAT networks are built on the basis of geostationary repeater satellites. This allows you to simplify the design of subscriber terminals and supply them with simple fixed antennas without a satellite tracking system. The satellite takes a signal from the earth station, enhances it and sends back to the ground. The most important characteristics of the 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 the maximum bandwidth of about 40 Mbps. Transmitter power ranges from 20 to 100 or more watts. To ensure work through small-sized subscriber stations of type VSAT, transmitters are required with an output power of about 40 W. The current Russian satellites have less power transmitters, so a large number of Russian networks are built on the basis of foreign satellites.

2.2 SCPC (SINGLE CHANNEL PER CARRIER)

SCPC (Single Channel Per Carrier, one canal on the carrier) - classical satellite communication technology. The essence of it is very simple: for the connection of two earth stations A and in the satellite, two frequency bands are distinguished: one for transmission towards A-B, the other - for transmission in the direction in A.

These bands are "monopolis" are used only by stations A and B and cannot be used by someone else. Thus, SCPC is a dedicated physical communication channel.

In Russia and in Europe there are networks of VSAT stations operating on the SCPC principle. The standard SCPC communication option is used to use the "Point-to-Point" principle ("Point-to-point") - these are two VSAT stations connected by the satellite channel and the users are located.

If you have such a channel, users can communicate with each other at any time. More often, it is necessary to deal with the configuration of the "Star" network (the principle of "Center with each"), when there is one station in the head office (separation, representation, etc.) and several stations in remote branches, branches. When using this scheme, it is possible to organize digital information streams at a speed of 32 kbps to 8 Mbps and providing telephone, telefaxes between the center and the periphery. This system opens up an exit through satellite stations to international teleport in Berlin and further to any country in the world. In addition, it is possible to obtain a direct Moscow number and through teleport in Moscow it is possible to conduct telephone conversations on the countries of the former USSR. In general, it should be noted that the SCPC system is a very powerful alternative to the leased non-commutable channels, departmental lines, etc. It is very attractive as a means of transmitting large amounts of information at high speed. Due to the use of satellite digital channels, it is non-critical to the range and noise-protective.

Connecting a remote cellular base station. This is the only way to connect a remote base station of cellular communication through a satellite, which guarantees high-quality communication and operation of all cellular operator services in full. A pair of modem with sequential synchronous interfaces G.703 is used, through which the digital stream E1 (2048 kbps) is transmitted, full or fractional.

Channel Internet access. SCPC satellite channel can be used as an external Internet access channel for the provider assembly in the region. As a rule, in this case, the satellite communication channel "lands" to the node of a major telecom operator in Moscow. Usually, such an operator has a central earth station with an antenna large sizes and a powerful transmitter. Due to this, his client in the region can use a terrestrial station with an antenna somewhat smaller.

Satellite network of broadcasting. PC Audio-Classical technology delivery of network FM radio stations to its relay partners in other cities. Especially relevant to the use of SCPC for regional radio stations, which are not in Moscow. SCPC satellite channel rental is cheaper than renting the same channel speed of any other technology. True, the reception stations have to use quite expensive specific equipment. However, repeater stations are usually a bit, and the cost of once purchased equipment quickly pays off on the payments for communication. The satellite earth station installed in the studio works only on the transfer. It establishes an ordinary satellite modem with the RS-449 serial interface and the ComStream DAC700 encoder, which converts the sound to a serial digital stream at a speed of 128 ... 392 kbps. A digital compression of the MPEG-1 Layer3 sound is used. At repeater stations, ordinary receiving satellite antennas are installed - the same as for satellite television. A specific Comstream ABR202 receiver is connected to the antenna, which combines a unidirectional satellite modem and MPEG decoder. A router is installed between the Modem of the Earth Station and Network Equipment of the Provider.

The TES system is designed to exchange telephone and digital information on networks, which are built according to the "Mesh" principle ("each with each") or, in other words, in networks with full access. This means that a telephone connection is possible between any two network subscribers, in addition to this, subscribers provide access to the international public network through Teleport (Gateway) in Berlin. The simplest configuration provides communication on a single telephone or facsimile channel. The subscriber is provided with an additional opportunity to organize digital information between two stations included in the network. The network works on the DAMA principle - when the subscriber does not have a rigidly attached satellite channel, and this channel is provided to him on the first requirement, with a high (more than 99%) probability. This method allows to reduce the number of rented satellite channels and provide reasonable prices for subscribers. In general, the use of the TES system is the most prompt and effective way of accessing the international telephone network, as well as a good means of communication with those areas that have either undeveloped infrastructure of communication, or do not have such.

PERSONAL Earth Station System (Personal Earth Station) PES ™ is a satellite dialogue packet-switched network, intended for the exchange of telephone and digital information within the framework of the SCC with the Topology of the Star Topology, with the possibility of complete duplex. The system has a large and expensive central station (Hub Station) and many small and low-cost peripheral PES or REMOTE. A large efficient radiated power The high quality of reception of the central station makes it possible to use on PES small antennas with a diameter of 0.5-1.8 m and low-power transmitters with a capacity of 0.5-2 W.

This significantly reduces the cost of subscriber ZS. Unlike other above-mentioned systems, in this transmission of information always goes through Hub. From the point of view of energy system and its cost (respectively, the cost of the services offered) is the best location of the Central ZS in the center of the satellite lighting area. For example, in the network running through the Intelsat-904 satellite, the Central ZS is located in Moscow.

Advantages of SCS:

Satellite communication systems may also differ in the type of transmitted signal, which can be digital or analog. The transfer of information in digital form has a number of advantages compared to other transmission methods. These include:

• * Easy and efficiency of combining many independent signals and converting digital messages to "Packages" for the convenience of switching;
• * Smaller energy consumption compared to the transmission of analog signal;
• * relative insensitivity of digital channels to the effect of distortion accumulation during relayers, usually representing a serious problem in analog communication systems;
• * Potential opportunity to obtain very low probabilities of transmission errors and achieve high fidelity to play transmitted data by detecting and correcting errors;
• * Connection confidentiality;
• * Flexibility to implement digital equipment that allows the use of microprocessors, digital switching and the use of microcircuits with a greater degree of integration of components.

Disadvantages of SCS:

Weak noiselessness. The huge distances between the earth stations and the satellite are the reason that the signal-to-noise ratio on the receiver is very small (much less than for most radio relay communication lines). In order to provide an acceptable probability of error under these conditions, you have to use large antennas, low-noise elements and complex interference codes. Especially acute this problem is in mobile systems, as they have a limit on the size of the antenna and, as a rule, the transmitter power.

Effect of atmosphere. The quality of satellite communications have a strong effect effects in the troposphere and ionosphere. Absorption in the troposphere. The absorption of the signal atmosphere is depending on its frequency. The absorption maxima occurs by 22.3 GHz (resonance of water vapor) and 60 GHz (oxygen resonance). In general, the absorption significantly affects the spread of signals with a frequency above 10 GHz (that is, starting with the KU-band). In addition to the absorption, when distributing radio filters in the atmosphere there is a fading effect caused by which the difference in the refractive indices of various layers of the atmosphere.

Ionospheric effects. Effects in the ionosphere are due to fluctuations of the distribution of free electrons. The ionospheric effects affecting the propagation of radio waves include: flickering, absorption, propagation delay, dispersion, frequency change, rotation of the polarization plane. All these effects are weakened with increasing frequency. For signals with frequencies, large 10 GHz, their influence is small.

Signal propagation delay. The problem of delaying the signal propagation, one way or another, affects all satellite communication systems. Systems using a satellite repeater on geostationary orbit have the greatest delay. In this case, the delay due to the limb of the radio wave speed limit is approximately 250 ms, and taking into account the multiplexing, switching and signal processing delays, the overall delay can be up to 400 ms. The distribution delay is most undesirable in real-time applications, for example, in telephone communication. In this case, if the signal distribution time on the satellite communication channel is 250 ms, the time difference between the replicas of subscribers cannot be less than 500 ms.

In some systems (for example, in VSAT systems using the Star Topology), the signal is transmitted twice through the satellite communication channel (from the terminal to the central node, and from the central node to another terminal). In this case, the overall delay is doubled.

3 Generalized characteristics of the state and development trends of the CSS

For the organization of communication channels, spacecraft (ka) located on a geostationary orbit (GSO) are mainly used. The possibility of creating telecommunication networks based on satellites in non-geostationary orbits is limited by a minor service area, the inability to provide services on an ongoing basis and a number of other factors. Most of these factors can be eliminated when using the satellite grouping, but the need to track them appear. Preferably, such groupings are used to organize mobile communications and broadcasting. The greatest of them are iridium (88 ka), Globalstar (48 ka), orbcomm (31 ka). To provide telecommunication services, especially broadcasting, geostationary satellite communications systems are used.

Every year on GSO is excreted from 15 to 30 ka and 10-15 satellites are completed. Over the past 10 years, the annual average increase in the amount of ka amounted to about 3%. However, when considering the issue of growth in satellite channels, which causes the launches of ka, it should be considered not an absolute increase, but the capabilities of the satellites derived on GSO. There is a tendency to launch more effective regarding the profit / price of "heavy" ka, having a telecommunication payload of about 50 stems or more. Of the 83 working "heavy" ka 69, it was brought into orbit after 2000 (33% of the total number of launches).

As of the beginning of March 2011, 319 civilian seats in the Gestamentary Orbit (GSO) operates in various services. Telecommunications services provide 67 international and national operators who own 89 satellite communication systems. SCCs are registered in 35 countries, the list of which is given in Appendix A.

The list of countries given in Appendix A should include Kazakhstan, Nigeria, Argentina, who have lost its satellites, but restoring the functioning of the SCC. This year, Kazakhstan, within the framework of the National Satellite Communications System, KAZSAT will lead to GSO two ka, Nigeria within the framework of NigComat - three ka. Argentina builds a new ARSAT satellite communication system as part of three kats. Satellites on GSO have about eleven thousand transponders of different services, power and capacity, of which about 8,000 tables are involved. Since transponders are significantly different by the frequency band, then a more acceptable criterion for the distribution estimate is the total barrel frequency band.

As of the end of February 2011, the total frequency resource of transponders of the transponders of the GSO satellites reached about 450 GHz bands, from which more than half in the KU range (51.4%), 35.1% in the range of C and 12.0% in Range Ka.

With the annual increase in the number of valid 3%, the annual increase in frequency resource is noticeably more, approximately 13%, which is associated with the launch of the "heavy" ka. Over ten years, the total band of satellite channels has risen about twice. In the KU and C bands, there is almost a linear increase in total capacity, the KA range is introduced more intensive pace.

The trends towards monopolization in the satellite telecommunications market began to appear since 2001 after the merger of SES ASTRA with GE Americom and the Education of SES Global Corporation. In 2006, the Corporation acquired the SCS NSS, in 2009, part of the Protostar disbanded CSS, and in March 2010, the SIRIUS CSS completely bought. In addition, SES Global owns a 70% stake in CIEL and 49% of the QUETZSAT operator shares planning the launch of the first ka in 2011

Intelsat International Organization After purchased in 2003, the Telstar (4 ka) and mergers with Panamsat (2005) became the largest satellite operator. In addition, in 2009, the organization bought three cars Amos 1, Protostar 2 and JCSAT 4R.

The third largest operator Eutelsat showed interest in the acquisition of Satmex SATS, under its control there is about a third of the assets of the Hispasat operator.

The Canadian operator Telesat in 2007 acquired the remains of Telstar CCC (4 ka) and became the fourth international operator in the world.

In 2008, Japanese JSAT and SCC operators (Superbird SCS) were formed by JSAT Perfec Pro, which also includes the NSAT SCS and partly SCC Horizons.

In 2006, the CABLEVISION operator moved under the control of an Echostar operator, which is mostly part of the DISH Network corporation under the control of the DirectV Group, which owns the DTV SCS and the SPACEWAY controlling SCS. You can talk about the practical combination of three DTV, Echostar and Spaceway systems.

In 2010, three Chinese operators of Chinasat systems, Sinosat, Chinastar were united and created a new Chinasat organization.

In 2010, the formation of the new Sirius XM Radio organization was announced after the XM Satellite Radio and Sirius FM Radio merge. Space fleet of this operator except six geostationary satellites includes four low-bit quality.

The existing trend towards monopolization is not a restraining factor in the development of small on the number of CCC. It is planned not only to launch satellites for replacing their time spent, but also the creation of new systems, including national SCS.

Over the next three years, the list of countries create national satellite communications systems is expected:

• - 2011, Iran: Zohreh SCCs (2 ka);
• - 2011, UAE: Yachsat SCCs (2 ka);
• - 2011, the United Arab Emirates with Jordan: SCCs SmartSat (1 ka);
• - 2012, Ukraine: Lybid SCCs (1 ka);
• - 2012, Azerbaijan: Azerspace SCS, (2 ka), one ka together with Malaysia;
• - 2013, Qatar: EShail SCCs (1 ka), together with Eutelsat;
• - 2013, Bolivia: SCC Tupac Katani (1 ka);
• - 2013 u /? KFJC ^ CCC Laosat (1 RF)

Countries having satellite groupings, in accordance with the needs of the market create new systems:

• - 2011, Russia: SCS Luch (3 ka) for data transfer services;
• - 2011, USA: Viasat (2 ka) to provide high-speed access services;
• - 2011, Mexico: QUETZSAT SCS to provide broadcasting services and fixed communications;
• - 2012, USA: JUPITER CCC (1 kA) and OHO SCS (3 ka) to provide high-speed and high-definition television services;
• - 2012, Mexico: SCC MEXSAT (3 ka), which will work in mobile, fixed and broadcast services;
• - 2012, Australia: SCC Jabiru (1 ka) to provide broadcasting services and fixed communications;
• - 2013, UAE: S2M (1 ka) to provide broadcasting services to mobile users;
• - 2013, Canada: CANUK SCS (1 ka) for high-speed access system.

Within the framework of the inmarsat mobile communication system, the new series of fifth generation and two ka Alfasat and EUROPESAT are focused on a new service type for this operator - broadcasting to mobile objects.

Satellite broadcasting remains a priority type of service. In addition to the standard set of directly broadcast services, distribution programs on ground-air and cable broadcasting networks through ETS 8 and MBSAT satellites are already conducting experimental television broadcasting on moving objects. To provide this type of service, it was planned to launch three ka (Eutelsat 2a, Echostar 13 or CMBSTAR and S2M 1), of which Eutelsat 2a was launched, but the antenna deployment malfunction was not allowed to start implementing services in the European Region. Satellite channels are intensively used to provide high-quality and interactive broadcast services, 3D television has begun.

The second priority was the provision of high-speed access services. Functioning specialized satellites Wildblue 1, Spaceway 3, IPStar 1, newly rented on GSO, Eutelsat Kasat and Hylas add to these services Viasat satellites (2 ka), OHO (3 ka), Canuk, 3 ka inmarsat fifth generation, jupiter and Others.

The further direction of the development of satellite telecommunication systems is associated with the convergence of services and functions of systems that are far from the principles of action and appointments by interpenetration and use of general technical and technological solutions. The convergence will make more and more differences between certain types of services, all networks will provide any view of a significantly expanded nomenclature and in a larger volume on the basis of a single technological platform that ensures the development of interactive and direct broadcasting, high-quality broadcasting, high-speed access systems, distance learning, telemedicine systems , Telebanking and other multiservice applications. The corporate nature of these services from a single center to the user network makes satellite communication systems most suitable for their provision. New services will take up to 80% of satellite resource.

The overall increase in the volume of satellite channels in the fifth anniversary is 76%, and an increase in revenues for telecommunications services, respectively, is: CER - 82%, FSS - 97%, PSS - 29%. Note that the data provided in Table 2 belongs to broadcasting channels. This type of services is also largely provided by the fixed communication channels, which in the table separate graph due to the lack of information is not marked. The main share of the income of the SCS in 2009 (81%) is provided by the Satellite Service of Broadcasting (CER), which emphasizes the degree of its priority. The distribution of the level of profitability between the services on the Satellite Industry Association published over the past five years is given in Appendix B. It should be emphasized that telecommunication services on satellite channels determine the main income from the activities in the space industry of the industry. Of the total revenue of equal to $ 160.9 billion, the share of telecommunications revenues is 58.2%.

The energy transport increased. The power of the trunks in the most used ranges on average is: KU 120 - 150 W, C - 50 - 60 W. The specific power per unit strip reached 1.2 W / MHz, which makes it possible to use more efficient multi-position signals and high-speed cascade codes in the channel.

Mobile satellite communications

Introduction

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

So, if for a cellular communication, such a basic parameter is the height of the raising antenna of the base station, then for satellite communication systems is the type of orbit of its space segment and orbit characteristics. In general, any satellite communication system consists of three segments, as mentioned above: Space (or space grouping), ground (ground service stations, pairing stations) and a custom segment (directly terminals for consumer).

Figure 1 The structure of the satellite communication system on the example of the network VSAT GP "Space" communication "

By the type of orbits, satellite communications systems are divided into two classes: systems with satellites on geostationary orbit (GEO) (height 36,000 km; number of satellites for GEO-group - 3, one satellite covers 34% of the earth's surface, delay when transmitting speech for global Communications - 600 ms) and non-geostationary.

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

Neleostationary satellite systems in turn are divided into medieval MEO (height - 5000-15000 km; number of spacecraft - 8-12; coating zone with one satellite - 25-28%; delay in speech transmission for global communication - 250-400 ms) and Low-bit LEO (height - 500-2000 km; Number of spacecraft - 48-66; coating zone with one satellite - 3-7%; delay during speech transmission for global communication - 170-300 ms).

Most of the existing satellite communications systems have geostationary satellite groups, which is easily explained: a small amount 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 extremely undesirable, since it leads to poor quality of communication and an increase in the value of the user segment. Therefore, the initial majority of satellite communication systems were mainly fixed satellite communications (the relationship between stationary objects), and only with the introduction of digital communication methods and the launch of non-geostationary spacecraft was widely developed by mobile satellite. We note that modern systems of mobile satellite communications, firstly, are compatible with traditional car-based mobile systems (first of all - with digital cellular), and, secondly, the interaction of mobile satellite radio communications networks with a public telephone network is possible at any level. (local, intrazonal, long-distance).

Major world mobile satellite telecommunications operators known in Russia

Iridium system (International Consortium "Iridium LLS", Washington). The system of global mobile personal satellite communications "iRidium" was intended to provide communication services with mobile and fixed objects located throughout the entire territory of the globe. The space segment of the system consisted of 66 main (orbit height 780 km above the surface of the Earth) and 6 reserve satellites (645 km). The system provided the following services to subscribers: Speech transmission (2.4 kbps), data transmission and telefax at the same speed, personal call and location definition.

Being a very expensive project (more than $ 5 billion), Iridium in the initial stage of development installed ultra-high prices for terminals and traffic, erroneously focusing only on very rich consumers services. In addition, during operation, the technical and financial problems have arisen in the project, which led a bankruptcy consortium.

Globalstar system (Globalstar Ltd., San Jose, PC. California). The GlobalStar global mobile personal satellite communications system is designed to provide communication services with mobile and fixed objects located on the territory of the globe between 700 * S.Sh. and 700 * Yu.Sh.

Globalstar portable terminals are produced in several modifications to ensure that they are able to use both for the organization of communication in the Globalstar system and in the networks of ground cellular communication standards GSM, AMPS, CDMA.

The space segment of the system is a grouping of 48 basic and 8 backup satellites, weighing less than 450 kg placed on circular orbits at an altitude of 1414 km above the ground surface. First generation satellites are designed to work in full load mode at least 7.5 years.

To cover the populated territory of the globe, it is planned to build about 50 pairing stations that ensure the maximum coating (up to 85%) of the earth's surface with the space segment of the system. At the first stage of the development of the system, 38 pairing stations were built. In Russia, 3 such stations are in operation: in the Moscow region (Pavlov Posad), in Novosibirsk and in Khabarovsk. These stations ensure the provision of mobile services with high quality service practically throughout Russia South 700 S.Sh. Each of these stations is associated with a public network of Russia. The GlobalStar system is operated in Russia since May 2000.

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

It is planned that the ICO system will work in cooperation with cellular systems, providing maintenance of regions and zones that are not covered by cellular radio communications systems. According to the project, most of the subscriber terminals of the ICO system will make personal handheld telephones capable of working in two modes (satellite / ground cell). The estimated cost of the subscriber terminal of the ICO system is 1000 dollars, one minute of traffic - 1 dollar.

The space segment of the system will be represented by grouping from 10 major and 2 backup satellites on a melo-orbit at a height of about 10390 km above the ground surface.

The feature of this system will be a specially formed ICONET network, which connects the "intelligent" communication lines of twelve satellite access (DSD) nodes located worldwide, and will provide a quick connection of public networks with mobile terminals and mobile terminals. From their location. On the territory of Russia is expected to build one USD. The infrastructure of the Earth segment of the ICO system is based on the GSM standard architecture of the GSM network, as well as the standard components of the "ICO" system compatibility compatibility with other standards of ground cellular communication.

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

TV range will provide services such as: digital telephony, emergency calls, fax transmission of group 3 at speeds up to 14.4 kbps and short message transmission services. In this case, digital telephony will ensure the quality of transmission of speech, similar to that provided by the existing standards of ground mobile radio communications.

In addition, the ICO system plans to provide services for transferring low-speed transparent and opaque data in asynchronous mode at 300, 1200, 2400, 4800 and 9600 bps and transparent data in synchronous mode at speeds 1200, 2400, 4800 and 9600 bits /from.

In connection with the financial problems of the consortium, a decision was made to merge "ICO Global Communications" with Teledesic Corporation that it will be delayed by the provision of services until 2003. One USD on the territory of Russia is intended to build besides. It is expected that 450 thousand subscribers will be used in the ICO system.

System "Inmarsat" (Company "INMARSAT LTD.", LONDON). "Inmarsat" owns satellites installed on a geostationary orbit in the following positions: 54 * ZD, 15.5 * ZD, 64.5 * V.D., 178 * V.D. It provides almost the global relationship between 75 * Yu.Sh. and 75 * S.Sh.

In the Inmarsat system, more than 50 terrestrial stations operate with rolling equipment installed on marine and river ships, drilling platforms, aircraft, vehicles (in Russia there are practically no), in businessmen casahs.

The following types of mobile stations are used: "INMARSAT-A", "INMARSAT-B", "INMARSAT-M", "INMARSAT-MINI-M", "INMARSAT-C", "INMARSAT-D +" (pager with response), " Inmarsat-Aero »(Various Types). The listed types of stations have different physical and electrical characteristics, which determines the large difference in the price of the stations, the tariff for the connection and its quality (information transmission rate, as a transmission of speech).

Currently, in the Inmarsat system, about 170 thousand stations of all types work, about 10 thousand of them have Russian numbers (Russian).

The ORBCOM system (Orbcom Global, Dalas, PC. Virginia). The ORBCOM communication system is intended for bilateral data transfer and determining the location of objects using low-bit artificial earth satellites (from 28 to 48 satellites). The transfer of data on the line "Satellite Earth" is carried out at a speed of 4.8 kbps, and on the line "Earth-satellite" - 2.4 kbps. The system was developed in the United States by Orbcom Global to meet the needs for exchanging information with areas remote from the existing ground telecommunications infrastructure.

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

News from world satellite telecommunications operators

One of the most sensitive and well-known global satellite communications projects is the project "Iridium" concern. In November 2000, the US bankruptcy court handed the management of Iridium to one Venture Fund. As a result, this seemingly a long-running company got a project worth $ 72 million on the equipment of the mobile satellite communications by the US Department of Defense. This is the more interesting that the competition has been won from another major and most dynamically developing currently operator - the company "Globalstar".

This year, in general, "GlobalStar" was unsuccessful (despite receiving a major order to equipment with telephone tubes of buses in Brazil and the start of operation of the system in Russia). He began with the refusal of major shareholders ("Loral Space & Communications Ltd" and "Qualcomm"), from further participation in Globalstar projects. However, a little later, so necessary $ 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 of 1999, the company's losses in terms of one share increased almost five times and amounted to $ 1 per share (in 1999 - 20 cents per action). At the end of the third quarter, the company served 21,300 subscribers, which is twice as much as at the end of the second quarter of 2000. The company's management believes that it is extremely small for the successful functioning of the global satellite communication system, but as a whole assesses the project as viable and argues that the company has the necessary money to work up to the end of May 2001.

At the same time, the losses "Globalstar" did not affect the deterioration of the financial position of its major shareholder - the company "Qualcomm" (provider of satellite data transmission systems, the competitor of which in this business is Orbcomglobal with such services as "Trackmaile-", "Omni-Track" and "EutelTrack"). It was mostly related to other projects of the concern. Qualcomm owns the main patents on CDMA wireless technology, on the 3G WCDMA standard (third generation mobile communication, the standard is developed by European companies), on the 3G CDMA2000 standard (the standard developed by Qualcomm).

American Mobile Satellite Corp continued the course on the development of the communication services for the fleet management and data transmission systems on its landline "Ardis".

The Japanese company NTT Docomo delivers communication services for the National Fleet. The Australian company Optus serves more than 9,000 subscribers. The European network "EMSAT" offers a complete set of mobile services, and the Belgian network of mobile satellite communication "IRIS" provides satellite data transmission.

The project of the company ICO Global Communications is suspended. Entering commissioning is planned not earlier than 2003.

On October 20, 2000, Boeing Satellite Systems implemented the successful launch of the Thuraya 1 satellite within its own project deployment of a moving satellite communication system, 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).

Operators of mobile satellite communications in Russia. "Inmarsat"

After the termination of the activities of Iridium on the territory of Russia, there are two mobile satellite telecom operators: "Inmarsat" and "Globalstar".

The INMARSAT system was established in 1979 in the USSR to establish satellite communications with marine courts and ensuring the safety of navigation. "Inmarsat" is currently managing the global satellite group, which is used to provide voice, facsimile telecast and multimedia communication services for moving users. Inmarsat satellites are located on a geostationary orbit. The guaranteed communication is provided on average from 70 ° Yu.Sh. up to 70 ° S.Sh. Each satellite covers approximately the third part of the Earth.

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

Models of satellite portable terminals of the "INMARSAT-MINI-M" type, commercially available in the Russian Federation

Figure 3. TT-3060A

The TT-3060A mobile phone Inmarsat satellite system is designed to transmit telephone and fax messages, data and email. Built-in battery and voltage converter provide non-volatile operation for 48 hours in standby mode and 2.5 hours in talk mode. Phone tube, 2-wired RJ-11 connector for fax and hayes-compatible port for data transmission with a speed of 2.4 kbps have personal phone numbers (total number - 4). The ability to protect against unauthorized access is ensured by the built-in SIM card reader. There is the possibility of connecting the STU-IIB / STU-III cryptographic equipment and using image transmission software. The housing of the magnesium alloy weighing less than 2.2 kg.

Fig. 4. WORLDPHONE HYBRID

WORLDPHONE HYBRID provides access to an international telephone network with the ability to transmit faxes, data and email. Key Features: 4.8 Kbps - Voice, 2,4 Kbps - Fax, 3 hours of talking in talk mode, Liquid crystal display with backlit, Speakerphone, Short message service (SMS), voice / fax mail, redirection, Notebook.

Operators of mobile satellite communications in Russia. "Globalstar"

The subsidiary of Globaltel (Joint Enterprise "Globalstar" and "Rostelecom") began to provide its services in the territory of the Russian Federation since May 2000. Currently this telephony (voice transmission) and call forwarding. Also in the system are provided, but the following services are not implemented: data transfer, fax communication, transmission and reception of short messages, global roaming, definition of the location of the object, voice mail, call emergency services.

The space segment includes a grouping of 48 low-bit (and 4 reserve) satellites, providing a coating from 70 ° C.Sh. up to 70 ° and placed 6 satellites on 8 circular orbits at an altitude of 1414 km. The low-bit satellite system allows dramatically to reduce the cost of the subscriber terminal and a minute of conversation.

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

Prices for subscriber terminals: Mobile $ 1000-1900 (depending on the manufacturer), stationary - from $ 3000. Tariff for 1 min. Outgoing traffic in Russia is $ 1.2-2.0 (including common network tariff).

The models of satellite portable mobile terminals that support the Globalstar services are available on the Russian market.

Fig. 5. Portable Subscriber Mobile Terminal Ericsson

Dual-mode terminal Ericsson. The contract for the production of tubes also includes the supply of automotive and / or stationary subscriber terminals. Modes of operation - Globalstar | GSM. Sizes mm - 160 × 60 × 37. Weight - 350g. Operation time in the conversation mode Globalstar / GSM hours -?. Opening hours of standby GlobalStar / GSM hours - 5/36.

Fig. 6. Portable Subscriber Mobile Telit Terminal

Telit Terminal provides communication in Globalstar | GSM and differs in the following characteristics: mm dimensions - 220 × 65 × 45; Weight - 300g; Talk time GlobalStar / GSM hours -?; Opening hours of standby GlobalStar / GSM hours - 36/36.

Fig. 7. Portable mobile subscriber terminal Qualcomm

Qualcomm Triple Control Terminal - Globalstar | AMPS | CDMA. Dimensions mm - 178 × 57 × 44. Weight - 357g. Operating time Globalstar / APMS / CDMA hours - 1/1/3. Opening hours of standby GlobalStar / Amps / CDMA hours - 5/7/25. Display 4 × 16 characters, notebook for 99 numbers, accelerated auto flashlight, voice mail, receiving messages, number determinant.

Conclusion

At the moment, despite certain failures (the bankruptcy of the Iridium concern, the suspension of the project "ICO", the losses "Globalstar"), the mobile satellite communications occupied its (what?) The segment of the global communications market. Sales of custom terminals are growing consistently, the number of telecom operators increases (launch of satellites by Boeing companies, the development of a new generation of small satellites by the company Investors does not weaken. At the same time, it is necessary to constantly track the events in this market segment and keep the "hand on the pulse" so that the users of mobile satellite phones in Russia are not in a situation of such that in Russia, with the termination of the Iridium concern, when the owners did not know What to do with tubes, one moment turned into a bunch of iron. Let's hope that in the foreseeable future, such serious cataclysms are not repeated, and the cost of user terminals and traffic is gradually equal to the value of the usual cellular communication.

In contact with

Odnoklassniki.

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

According to today's standards, the Early Bird satellite ( Intelsat I.) possessed more than modest possibilities: possessing a bandwidth of 50 MHz, it could provide up to 240 telephone communication channels. At each specific point in time, the connection could be carried out between the Earth station in the United States and only one of the three Earth stations in Europe (in the UK, France or Germany), which were interconnected by cable lines of communication.

In the future, the technology stepped forward and satellite Intelsat IX. Already possessed a bandwidth of 3456 MHz.

In the USSR, for a long time, satellite communications developed only in the interests of the USSR Ministry of Defense. By virtue of greater closedness of the Space Program, the development of satellite communications in socialist countries was otherwise in western countries. The development of civilian satellite communications began its agreement between 9 countries of the socialist bloc on the creation of a communication system "Interspotnik" which was signed only in 1971

Satellite repeaters

Passive communication satellite ECHO-2. Metallized inflatable sphere performed the functions of a passive repeater

In the first years of research, passive satellite repeaters were used (examples - Echo and Echo-2 satellites), which were a simple radio signal reflector (often - a metal or polymer sphere with a metal spraying), not carrying any receiving equipment aboard . Such satellites did not get distribution. All modern communication satellites are active. Active repeaters are equipped with electronic equipment for receiving, processing, gaining and relaying the signal. Satellite repeaters can be irregular and regenerative . A non-generative satellite, adopting a signal from one earth station, transfers it to another frequency, enhances and transmits another earth station. The satellite can use several independent channels that carry out these operations, each of which works with a certain part of the spectrum (these processing channels are called transponders).

The regenerative satellite produces the demodulation of the received signal and re-modulates it. Thanks to this, the error correction is performed twice: on the satellite and on the host earth station. The disadvantage of this method is the complexity (and therefore a much higher satellite price), as well as an increased signaling delay.

Orbits of satellite repeaters

The orbits on which satellite repeaters are placed, are divided into three classes:

• equatorial,
• inclined
• polar.

An important variety equatorial orbit It is a geostationary orbit, on which the satellite rotates at an angular velocity equal to the angular velocity of the Earth, in the direction that coincides with the direction of rotation of the Earth. The obvious advantage of the geostationary orbit is that the receiver in the service zone "sees" the satellite constantly.

However, the geostationary orbit is one, and all satellites are not possible to bring it. Another disadvantage is a big height, which means a large price of the satellite in orbit. In addition, the satellite on the geostationary orbit is not able to serve earth stations in the indoor 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 run at least three satellites per orbit to provide round-the-clock access to communication.

Polar orbit - Land inclined case (with inclination 90º).

When using inclined orbits, earth stations are equipped with tracking systems carrying out antenna to satellite. Stations working with satellites located on a geostationary orbit are usually equipped with such systems to compensate for the deviation from the ideal geostationary orbit. The exception is small antennas used to receive satellite television: their directivity diagram is wide enough, so they do not feel the satellite oscillations near the perfect point.

Multiple frequency use. Coating zones

Since radio frequencies are a limited resource, it is necessary to ensure the possibility of using the same frequencies with 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 - Various antennas are taken and transmit a signal in mutually perpendicular polarization planes, while the same frequencies can be used twice (for each of the planes).

A typical coating card for a geostationary orbit, includes the following components:

• global beam - Communication with earth stations throughout the coating zone, it is highlighted frequencies that do not intersect with other rays of this satellite.

• rays of Western and Eastern Hemispheres - These rays are polarized in the plane A, and the same frequency range is used in Western and eastern hemispheres.

• zone rays - Polarized in plane B (perpendicular a) and use the same frequencies as the rays of the hemisphere. Thus, the earth station located in one of the zones can also use the rays of the hemisphere and a global beam.

At the same time, all frequencies (with the exception of reserved for the global beam) are used repeatedly: in Western and eastern hemisters and in each of the zones.

Frequency ranges

Antenna for receiving satellite television (KU-range)

Satellite antenna for C-band

The choice of frequency for transferring data from the earth station to the satellite and from the satellite to the earth station is not arbitrary. The frequency depends, for example, the absorption of radio waves in the atmosphere, as well as the necessary dimensions of the transmitting and receiving antennas. The frequencies on which the transfer from the earth's station to the satellite differ from the frequencies used to transmit from the satellite to the earth station (as a rule, the first above).

Frequencies used in satellite communications are divided into ranges indicated by letters. Unfortunately, in various literature, the exact boundaries of the ranges may not coincide. Approximate values \u200b\u200bare given in recommendation ITU -R V.431-6:

Name range	Frequencies (according to ITU-R v.431-6)	Application
L.	1.5 GHz	Mobile satellite communications
S.	2.5 GHz	Mobile satellite communications
FROM	4 GHz, 6 GHz	Fixed satellite communications
X.	For satellite communications, ITU-R recommendations are not defined. For radar applications, a range of 8-12 GHz is specified.	Fixed satellite (for military purposes)
Ku.	11 GHz, 12 GHz, 14 GHz
K.	20 GHz	Fixed satellite communications, satellite broadcasting
Ka.	30 GHz	Fixed Satellite Communication, Interpovers

Higher frequencies are used, but their increase is hampered by the high absorption of radio waves of these frequencies atmosphere. KU-range allows you to receive a relatively small antennas, and therefore used in satellite television (DVB), despite the fact that in this range the weather conditions have a significant impact on the quality of the transfer.

C-band is often used to transmit data by large users (organizations). It provides a higher quality of reception, but requires quite large antenna sizes.

Modulation and noise-resistant coding

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

• significant remoteness of the receiver from the transmitter,
• limited satellite power (inability to drive in high power).

In this regard, satellite communications is poorly suitable for transmitting analog signals. Therefore, it is pre-digitized to transmitting speech, using, for example, pulse-code modulation (ICM).

To transfer digital data on the satellite communication channel, they must first be converted to a radio signal that occupies a specific frequency range. This uses modulation (digital modulation is also called manipulation). The most common types of digital modulation for satellite communications applications are phase manipulation and quadrature amplitude modulation. For example, in DVB-S2 systems, QPSK, 8-PSK, 16-APSK and 32-APSK are used.

Modulation is made on the earth station. The modulated signal is amplified, transferred to the desired frequency and enters the transmitting antenna. The satellite takes the signal, enhances, sometimes regenerates, transfers to another frequency and using a specific transmitting antenna broadcasts to Earth.

Multiple access

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

• Multiple frequency separation access - with each user a separate frequency range is provided.

• multiple temporary separation access - each user is provided with a specific time interval (timecot) during which it transfers and receive data.

• multiple code separation access - with each user, a code sequence is issued, orthogonal code sequences of other users. User data is superimposed on the code sequence in such a way that the transmitted signals of various users do not interfere with each other, although transmitted on the same frequencies.

In addition, many users do not need permanent access to satellite communications. These users of the communication channel (Timeslot) stand out on demand using Dama technology (Demand Assigned Multiple Access - multiple access with the provision of channels on demand).

Application of satellite communications

Main satellite communications

Initially, the emergence of satellite communications was dictated by the needs of transmitting large amounts of information. Intelsat system was the first satellite communication system, then similar regional organizations were created (Eutelsat, Arabsat and others). Over time, the proportion of speech transmission in the total volume of the main traffic has been constantly declining, giving way to data transfer.

With the development of fiber-optic networks, the latter began to push out satellite communications from the main communication market.

VSAT systems

The words "very small aperture" refer to the size of the terminals antennas compared with the size of older antennas of the main communication systems. VSAT terminals operating in the C-range typically use antennas with a diameter of 1.8-2.4 m, in the KU-band - 0.75-1.8 m.

In VSAT systems, the technology of providing channels on request is applied.

Mobile satellite communication systems

A feature of most mobile satellite systems is a small size of the terminal antenna, which makes it difficult to receive a signal. In order for the power of the signal to reach the receiver, is sufficient, apply one of two solutions:

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

Cellular operators compete with personal satellite operators. It is characteristic that both Globalstar and Iridium experienced serious financial difficulties who brought iRidium to reorganization Bankruptcy in 1999

In December 2006, the experimental geostationary satellite of Kiku-8 was launched with a record-wide range of antenna, which is supposed to be used to work out the technology of satellite communications with mobile devices not exceeding cell phones.

Satellite Internet

Satellite communications is used in the organization "Last Mile" (communication channel between the Internet provider and the client), especially in places with a poorly developed infrastructure.

The features of this type of access are:

• The separation of incoming and outgoing traffic and attracting additional technologies to align them. Therefore, such compounds are called asymmetric.
• Simultaneous use of the incoming satellite channel by several (for example 200 mi) users: through the satellite simultaneously transmitted data for all customers "Interest", the client terminal is being filtered (for this reason, "fishing from the satellite" is possible).

By type of outgoing channel, distinguish:

• Terminals working only on receiving the signal (the cheapest connection option). In this case, for outgoing traffic, you must have another Internet connection, the supplier of which is called ground provider. To work in such a scheme, tunneling software is attracted, usually included in the terminal delivery. Despite the complexity (including the complexity in the setting), such a technology is attractive to high speed compared to the Dial-Up for a relatively small price.
• Receiving transmitting terminals. The outbound channel is organized narrow (compared to the incoming). Both directions provide the same device, and therefore such a system is much easier to configure (especially if the terminal is external and connects to the computer via the Ethernet interface). Such a scheme requires installation on an antenna of a more complex (receiving-transmitting) converter.

In both cases, the data from the provider to the client is transmitted, as a rule, in accordance with the DVB digital broadcast standard, which allows using the same equipment for both access to the network and for receiving satellite television.

Disadvantages of satellite communications

Weak noiselessness

The huge distances between the earth stations and the satellite are the reason that the signal-to-noise ratio on the receiver is very small (much less than for most radio relay communication lines). In order to provide an acceptable probability of error in these conditions, you have to use large antennas, low-noise elements and complex noise-resistant codes. Especially acute this problem is in mobile systems, as they have a limit on the size of the antenna and, as a rule, the transmitter power.

Effect of atmosphere

The quality of satellite communications have a strong effect effects in the troposphere and ionosphere.

Absorption in the troposphere

The absorption of the signal atmosphere is depending on its frequency. The absorption maxima occurs by 22.3 GHz (resonance of water vapor) and 60 GHz (oxygen resonance). In general, the absorption significantly affects the spread of signals with a frequency above 10 GHz (that is, starting with the KU-band). In addition to the absorption, when distributing radio filters in the atmosphere there is a fading effect caused by which the difference in the refractive indices of various layers of the atmosphere.

Ionospheric effects

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

Signals with a relatively low frequency (L-range and partially C-Range) suffer from ionospheric flickerarising due to inhomogeneities in the ionosphere. The result of this flicker is the constantly changing signal power.

Signal distribution delay

The problem of delaying the signal propagation is somehow affecting all satellite communication systems. Systems using a satellite repeater on geostationary orbit have the greatest delay. In this case, the delay due to the limb of the radio wave speed limit is approximately 250 ms, and taking into account the multiplexing, switching and signal processing delays, the overall delay can be up to 400 ms.

The distribution delay is most undesirable in real-time applications, for example, in telephone communication. At the same time, if the signal distribution time on the satellite communication channel is 250 ms, the time difference between the replicas of subscribers cannot be less than 500 ms.

In some systems (for example, in VSAT systems using the Star Topology), the signal is transmitted twice through the satellite communication channel (from the terminal to the central node, and from the central node to another terminal). In this case, the overall delay is doubled.

Influence of solar interference

see also

• OJSC "Information Satellite Systems" named after academician M. F. Reshetnyova "

Notes

1. Vishnevsky V.I., Lyakhov A. I., Torchnaya S. L., Shakhovich I. V. Historical Essay of Network Technology Development // Broadband Information Transmission Networks. - monograph (the publication was carried out with the support of the Russian Fundamental Research Foundation). - m .: "Technosphere", 2005. - P. 20. - 592 p. - ISBN 5-94836-049-0
2. Communications Satellite Short History. THE BILLION DOLLAR TECHNOLOGY
3. Communications Satellite Short History. THE GLOBAL VILLAGE: INTERNATIONAL COMMUNICATIONS
4. Intelsat Satellite Earth Station Handbook, 1999, p. eighteen
5. Square B. Digital communication. Theoretical foundations and practical application. Ed. 2nd, Act.: Per. from English - M.: Publishing House "Williams", 2004
6. Official website of the company "Interspotnik"
7. Conceptual legal issues of broadband satellite multiservice networks
8. Dennis Roddy. Satellite Communications. McGraw-Hill Telecommunications, 2001, p. 167.
9. Intelsat Satellite Earth Station Handbook, 1999, p. 2.
10. Intelsat Satellite Earth Station Handbook, 1999, p. 73.
11. Dennis Roddy. Satellite Communications. McGraw-Hill Telecommunications, 2001, PP. 6, 108.
12. Intelsat Satellite Earth Station Handbook, 1999, p. 28.
13. RECOMMENDATION ITU-R v.431-6. Nomenclature of the Frequency and Wavelength Bands Used in Telecommunications
14. Dennis Roddy. Satellite Communications. McGraw-Hill Telecommunications, 2001, PP. 6, 256.
15. Dennis Roddy. Satellite Communications. McGraw-Hill Telecommunications, 2001, p. 264.
16. http://www.telesputnik.ru/archive/116/article/62.html DVB-S2 standard. New tasks - new solutions // Magazine on satellite and cable television and telecommunications "Holder"
17. Dennis Roddy. Satellite Communications. McGraw-Hill Telecommunications, 2001, p. 283.
18. Morelos-Saragoza R. The art of noise-resistant coding. Methods, algorithms, application / trans. from English V. B. Afanasyev. - M.: Technosphere, 2006. - 320 p. - (peace of communication). - 2000 copies. - ISBN 5-94836-035-0
19. Dr. LIN-NAN LEE LDPC Codes, Application to NEXT Generation Communication Systems // Ieee Semiannual Vehicular Technology Conference. - October 2003.
20. Bernard Sklyar. Digital connection. Theoretical Basics and Practical Application \u003d Digital Communications: Fundamentals and Applications. - 2 ed. - m .: "Williams", 2007. - S. 1104. - ISBN 0-13-084788-7
21. Satellite communications system and broadcasting "Yamal"
22. VSAT FAQ.
23. Dennis Roddy. Satellite Communications. McGraw-Hill Telecommunications, 2001, p. 68.
24. Satellite Internet and VSAT Information Centrum
25. Satellite Communications and Space Weather
26. Dennis Roddy. Satellite Communications. McGraw-Hill Telecommunications, 2001, p. 91.
27. Dennis Roddy. Satellite Communications. McGraw-Hill Telecommunications, 2001, p. 93.
28. Bruce R. Elbert. The Satellite Communication Applications Handbook. - Artech House, Inc., 2004, p. 34.
29. Satellite Communications In The Global Internet: Issues, Pitfalls, and Potential

Links

• WTEC PANEL REPORT ON GLOBAL SATELLITE COMMUNICATIONS TECHNOLOGY AND SYSTEMS (English)
• About the Early Bird satellite on the site Boeing.com (English)
• Communications Satellites Short History (English)
• VSAT FAQ (English)