Satellite communications for technology. Technical Customer Support

Useful tips

Along with the means of mobile communication that have already become generally available (personal radio calls and cellular), in recent years modern personal satellite communication systems have been increasingly being introduced in Russia. Today and in the foreseeable future they are designed to develop and complement existing systems cellular communications where it is impossible or not effective enough:

– when transmitting information on a global scale;

– in the waters of the World Ocean;

– in areas with low population density;

– in places where ground infrastructure breaks, etc.

Mobile satellite communication systems are designed to provide services to the following user groups: subscribers cellular networks those who need roaming throughout the country (individuals, business representatives); subscribers who, due to the nature of their activities, require constant communication throughout the entire territory (top-level managers, administration representatives).

Depending on the type of services provided, satellite communication systems can be divided into 3 main classes:

1. Packet data transmission systems (delivery of circular messages, automated collection of data on the status of various objects, including vehicles, etc.)

2. Voice (radiotelephone) communication systems

3. Systems for determining the location (coordinates) of consumers

Packet data transmission systems are designed for transmission to digital form any data (telex, fax messages, computer data, etc.).

In radiotelephone communications in satellite systems, digital message transmission is used, and generally accepted international standards must be met.

SERVICES PROVIDED BY SATELLITE COMMUNICATION SYSTEMS:

– Voice transmission (telephone communication);

– Transmission of fax messages;

- Data transfer;

– Personal radio call (paging);

– Determining the location of the subscriber;

– Global roaming.

CLASSIFICATION OF SSS

1. By system status

2. By type of ISS orbits

3. According to the system’s affiliation with a specific radio service

Depending on the status, the SSS can be divided into international (global, regional), national and departmental.

According to the type of orbits used, ISS systems in geostationary orbit (GEO) and in non-geostationary orbit are distinguished:

– elliptical (HEO);

– low-orbit (LEO);

– medium-altitude (MEO).

In accordance with the radio regulations, satellite communication systems can belong to one of 3 services:

– fixed satellite service;

– mobile satellite service;

– broadcasting satellite service.

STRUCTURE OF SATELLITE COMMUNICATION SYSTEMS

The satellite communication system consists of two basic components - space and ground segments.

The space segment includes artificial communication satellites (ISS), launched into certain orbits (they are also called spacecraft - SC).

The ground segment includes a communications system control center, Earth stations (ES), regional stations (located in regions) and user terminals.

Figure 39 – Block diagram of a satellite communication network

Space segment.

It includes several relay satellites that are placed in certain orbits and form a space constellation.

In order to provide communications to subscribers not only in the visibility zone of one spacecraft, but throughout the entire territory of the Earth, neighboring satellites must communicate with each other and transmit information along the chain until it reaches the addressee. This task is performed by ground gateway stations, which transmit information from one spacecraft to another.

Ground segment.

System control center - monitors spacecraft, calculates their coordinates, reconciles and corrects time, transmits service information, etc.

Spacecraft launch center - determines the launch program, assembles the launch vehicle, checks it, as well as installs the payload (SC) and conducts pre-launch checks and tests.

Communications control center – plans the execution of the satellite resource, coordinating this operation with the system control center. Carries out analysis and control of communications, as well as management, through national gateway stations.

Gateway stations - consist of several transceiver complexes (³3), each of which has a tracking parabolic antenna. Gateway stations include switching equipment (communication interfaces) for connecting to various terrestrial communication systems. The main task of the gateway station is to provide duplex telephone communication, transmit fax messages, as well as large volumes of data.

Personal user segment.

To organize satellite communications, portable personal satellite terminals and mobile terminals. They establish a connection between subscribers in 2 seconds, just like in a cellular communication system.

The following types of satellite terminals exist:

– portable terminals (satellite phones);

– portable personal terminals;

– mobile terminals for vehicles, air and sea vehicles;

– small-sized paging terminals;

– terminals for collective use.

Personal satellite mobile terminals operate in the frequency ranges 137-900 and 1970-2520 MHz, which are practically no different from the cellular frequency range (450-1800) MHz.

Test questions on topic 4.3:

1. What is “mobility”?

2. What is called mobile communication?

3. How are communication systems with moving objects classified?

4. What is the scope of application of trunking systems?

5. What are the principles of organizing trunking communications?

6. By what criteria are trunked radio communication systems classified?

7. What is paging?

8. Describe the paging communication standards POCSAG, ERMES, FLEX.

9. What is a “cellular communication system”?

10. What does a cellular communication system include?

11. Explain the organization of the relay race.

12. What is roaming? Types of roaming.

13. What are the features of the NMT-450 and AMPS cellular communication standards?

14. Compare digital cellular communication standards D-AMPS and GSM-900/1800.

15. What is called cordless telephony?

17. Purpose and services of satellite communication systems.

18. How are satellite communication systems classified?

19. What is included in the satellite communication system?

Topic 4.4 Information communication networks

Information and computing network(possible name - computer networks) is a system of computers connected by data transmission channels.

The main purpose of information and computing networks (ICNs) is to ensure the effective provision of various information and computing services to network users by organizing convenient and reliable access to resources distributed in this network.

Information systems built on the basis of IVS ensure the effective implementation of the following tasks:

- data storage;

- data processing;

– organizing user access to data

– transfer of data and data processing results to users.

Types of information and computer networks

Information and computer networks (ICNs), depending on the territory they cover, are divided into:

– local (LAN or LAN – Local Area Network);

– regional (RVS or MAN – Metropolitan Area Network);

– global (WAN or WAN – Wide Area Network).

Local IVS is a network whose subscribers are located at a short (up to 10-15 km) distance from each other. A LAN unites subscribers located within a small area. The LAN class includes networks of individual enterprises, firms, banks, offices, and corporations. If such LANs have subscribers located in different premises, then they (networks) often use the infrastructure of the global Internet network and are usually called corporate networks or networks intranet(intranet).

Regional networks connect subscribers of a city, district, region or even a small country. Typically, the distances between subscribers of a regional IVS are tens to hundreds of kilometers.

Global networks unite subscribers located at considerable distances from each other, often located in different countries or on different continents. Interaction between subscribers of such a network can be carried out on the basis of telephone communication lines, radio communication systems and even satellite communications.

Topology is a way of organizing physical connections when building a computer network. Physical connections refer to the electrical connections between computers.

According to the geometry of construction (topology) IVS can be:

– bus (linear, bus);

– ring (loop, ring);

– radial (star-shaped, star);

– distributed radial (cellular, cellular);

– hierarchical (tree-like, hierarchy);

– fully connected (grid, mesh);

– mixed (hybrid).

Bus topology networks use a linear mono data transmission channel, to which all nodes are connected via interface boards using relatively short connecting lines. Data from the transmitting network node is distributed along the bus in both directions. Information arrives at all nodes, but only the one to which it is addressed receives it.

Bus topology is one of the simplest topologies. Such a network is easy to expand and configure, as well as adapt to various systems; it is resistant to possible failures of individual components. The bus topology network uses the well-known Ethernet network. An example of a bus topology is shown in Figure 40.

Workstation C

Server

Figure 40 – Network with bus topology

In a network with a ring topology, all nodes are connected into a single closed loop (ring) by communication channels. The output of one network node is connected to the input of another. Information is passed along the ring from node to node, and each node relays the sent message. For this purpose, each node has its own interface and transceiver equipment, which allows you to control the passage of data in the network. In order to simplify the transmitting and receiving equipment, data transmission over the ring is carried out only in one direction. The receiving node recognizes and receives only messages addressed to it.

Due to their flexibility and reliability, networks with a ring topology are also widely used in practice (for example, the Token Ring network). The conditional structure of such a network is shown in Figure 41.

Figure 41 – Network with ring topology

Consistent basis networks with radial topology amounts to special computer– a server to which workstations are connected, each via its own communication line. All information is transmitted through a central node, which relays, switches and routes information flows in the network.

The disadvantages of such a network include:

– high workload of central equipment;

– complete loss of network functionality when central equipment fails;

– large length of communication lines;

– lack of flexibility in choosing the path for transmitting information.

Serial radial networks are used in offices with clearly centralized control.

The conditional structure of the radial network is shown in Figure 42.

Figure 42 – Network with radial topology

In the network structure we can distinguish communication And subscriber's subnets

Communication subnet is the core computer network, connecting workstations and servers with each other. The links of the communication subnet (in this case, switching nodes) are interconnected by backbone communication channels with high throughput. In large networks, the communications subnetwork is often called the data network.

Links subscriber subnet(host computers, servers, workstations) are connected to switching nodes via subscriber communication channels - usually medium-speed telephone communication channels.

Depending on the communication medium used, networks are divided into monochannel networks; hierarchical, fully connected networks and networks with mixed topology.

In monolink networks, data can follow the same path; in them, subscribers' access to information is carried out on the basis of selection (selection) of transmitted frames or data packets according to the address part of the latter. All packages are available to all network users, but only the subscriber whose address is indicated in the package can “open” the package. Such networks are sometimes called networks with information selection.

Hierarchical, fully connected and networks with mixed topology in the process of data transmission require routing of the latter, that is, selection at each node of the path for further movement of information. Such networks are called networks with information routing.

ACCESS METHODS

There are two methods of accessing channels in the LCS: CSMA/CD and marker.

Carrier Sense Multiple Access with Collision Detection is called CSMA/CD (Carrier Sense Multiple Access with Collision Detection).

This standard is based on local Ethernet networks, developed by Xerox, and the names Ethernet and CSMA/CD are often considered synonymous. However, although they have a lot in common, they are still not exactly the same

CSMA/CD networks use a bus topology and the so-called Manchester coding. The physical transmission medium of such networks is built according to following standards:

· 10Base-5 – “thick” coaxial cable with a linear speed of 10 Mbit/s. This is the original version of Ethernet with a maximum segment length of 500 m;

· 10Base-2 – “thin” coaxial cable with a linear speed of 10 Mbit/s. This network is often called Cheapernet. It has a maximum segment length of 185 m;

· 1Base-5 – twisted pair with a linear speed of 1 Mbit/s and a physical star topology, but logically it acts as a bus;

· 10Base-T – twisted pair cable with a linear speed of 10 Mbit/s and a physical star topology;

· 10Base-F – optical fiber with a linear speed of 10 Mbit/s and a star topology.

In networks with a token access method, in order to provide stations with access to the physical medium, a frame circulates around the ring special format and destination – marker. The station always transmits data to its nearest downstream neighbor. Having received the marker, the station analyzes it and, if it does not have data to transmit, ensures its advancement to the next station.

A station that has data to transmit, upon receiving the token, removes it from the ring, which gives it the right to access the physical medium and transmit its data.

This access algorithm is used in Token Ring networks with an operating speed of 4 Mbit/s. The token access method is also used in FDDI, Arc Net, and MAP networks.

Send your good work in the knowledge base is simple. Use the form below

Students, graduate students, young scientists who use the knowledge base in their studies and work will be very grateful to you.

Posted on http://www.allbest.ru/

Satellite connection

Satellite communications have the most important advantages necessary for building large-scale telecommunications networks. Firstly, with its help you can quickly create a network infrastructure that covers a large area and does not depend on the presence or condition of terrestrial communication channels. Secondly, the use of modern technologies for accessing the resource of satellite repeaters and the ability to deliver information to an almost unlimited number of consumers simultaneously significantly reduce the cost of operating the network. These advantages of satellite communications make it very attractive and highly effective even in regions with well-developed terrestrial telecommunications. Moreover, at present, many companies with a geographically distributed structure are extremely interested in reducing the costs of paying for communication services and are increasingly abandoning public network services, preferring to create their own more cost-effective satellite communication networks. The modern market for satellite communications services and systems is replete with a wide range of technological solutions for building such networks, and choosing the right satellite technology for your enterprise becomes a very difficult task. How to approach it correctly? Who to entrust the construction of a corporate network to?

First of all, you need to clearly formulate the telecommunications needs of your enterprise - after all, the efficiency of the future network largely depends on the correctly drawn up technical specifications. It is necessary to determine the network topology - the connection diagram between its nodes, which most often are branches of the enterprise. It should be taken into account that communication via a geostationary satellite introduces a noticeable delay in signal propagation; therefore, in some cases it is extremely undesirable to use “double hops” of the signal, doubling this delay. In addition, redundant connections often add complexity and cost to the network.

In networks where communication between all branches must be carried out with minimal delay time during signal transmission, a fully connected topology should be implemented. In this case, each network node will be able to establish a direct connection with any other network node. This topology is used in corporate networks with large and multidirectional telephone traffic, as well as in data transmission systems with random connections between their nodes and strict requirements for time delays. The advantages of this topology are undeniable, however, its use is not economically justified in all cases.

For each telecommunications service your business requires (telephone, fax or data), it is very important to determine the optimal satellite communications network topology and technology and try to implement an integrated communications system that supports them.

So, we have decided on the network topology. Next, you need to estimate the volume of traffic transmitted over it - a rather difficult task, especially for enterprises that are currently developing intensively and plan to complete a complete re-equipment of their communication infrastructure over time. In such cases, it is recommended to use technologies that can develop “in step” with the growing needs of the enterprise, but it is still necessary to estimate the volumes of initial and future traffic. To do this, you can take the path of extrapolating data on the load of existing communication channels (which includes the size of typical messages transmitted, as well as the duration and frequency of telephone conversations over a certain period of time) taking into account the planned growth in the number of network users. When calculating network load, you need to use the amount of traffic during peak hours, when it is maximum. It is of no small importance to take into account changes in the volume of traffic depending on the direction of data transmission along each of the network channels, since with the help of satellite technologies it is possible to create channels with asymmetric throughput. Knowing the requirements for acceptable time delays for all types network traffic, you can use a system of their priorities, which increases the efficiency of network resource allocation.

Considering the high importance of the task of predicting the amount of traffic on a network, it is recommended to entrust its solution to specialists with extensive experience in planning and operating such networks.

Any satellite communication network includes one or more relay satellites, through which the interaction of earth stations (ES) is carried out. Currently, satellites operating in the C (4/6 GHz) and Ku (11/14 GHz) frequency bands are most widely used. As a rule, C-band satellites serve a fairly large area, and Ku-band satellites cover a smaller area, but have higher energy, which makes it possible to use satellites with small-diameter antennas and low-power transmitters to work with them. A communications satellite is selected based on two criteria: the configuration of the service area (it must coincide with the geography of the corporate network) and the cost of the channel (including the cost of the satellite repeater and satellite resource required for its formation). You should pay attention to the guaranteed service life of the selected satellite and the statistics of malfunctions of similar spacecraft.

Any ES includes radio frequency and channel-forming equipment. The first is the antenna and transceiver, which must match the type of satellite selected and ensure the operation of channel-forming equipment. As a rule, these two GS components are supplied as a set.

Channel-forming equipment determines the operating principle of the AP and the entire network. There are currently four main technologies for satellite communications networks. They all have their advantages and disadvantages, and none of them are universal. To improve operational efficiency, many modern networks successfully combine several technologies simultaneously. The main difference between them is the way the satellite repeater resource is used. Let's take a look at these technologies.

· ·SCPC (Single Channel Per Carrier) is actively used to build small networks with intense traffic. Each AP that implements SCPC has a dedicated permanent segment of satellite transponder capacity and maintains a persistent connection. The main advantage of this technology is that it guarantees the necessary throughput of the satellite communication channel, and the main disadvantage is the lack of the ability to dynamically redistribute the repeater resource between network nodes.

· DAMA (Demand Assigned Multiple Access) provides satellite repeater resource on demand. In networks with DAMA technology, a communication channel is allocated to the user only for the duration of the communication session, which significantly saves the resources of the satellite repeater. The channel structure in this network is similar to the SCPC channel structure. Some implementations of DAMA technology provide the ability to establish connections with different bandwidths for different communication sessions. DAMA is optimal for creating telephone networks with a fully meshed topology. The repeater resource is distributed by the central station of the network, which can be considered the main disadvantage of the technology, since the functioning of the entire network depends on the state of this one station.

· TDMA (Time Division Multiple Access) provides multiple stations with dynamic access to a common time division channel. Unlike DAMA technology with its sufficient big time establishing a connection, such access is provided much faster. However, TDMA networks are quite expensive, since any of these stations - even with the most minimal traffic - must transmit data at a speed equal to the total capacity of the time-shared channel. In TDMA networks, there is usually no central control station.

· TDM/TDMA (Time Division Multiplexing/Time Division Multiple Access) - a combined technology of networks with a star topology. In a TDM/TDMA network, the central station communicates with user stations using one or more assigned TDM channels (with time multiplexing), and user stations access the central station through TDMA channels. Since all user stations directly interact only with the central station, it becomes possible to use rather low-power stations, compensating for their lack of energy by using a large-diameter antenna and a powerful transmitter at the central station. Due to this imbalance of station parameters, it is possible to significantly reduce the cost of projects with a large number of user stations. The mandatory presence of a central station (which acts as a network hub) imposes high requirements on its readiness - after all, the functioning of the entire network depends on the state of this station.

In a TDM/TDMA network, data transmitted between any two user stations passes through the relay satellite twice (“double hop”). In this case, a significant (1--2 s) signal delay occurs, which makes this network unsuitable for using telecommunication applications that are sensitive to such delays.

Support for the core technologies discussed above is implemented in many modern satellite communications hardware. Very often it makes sense to use several technologies simultaneously on the same network. For example, to build a large-scale corporate telecommunications infrastructure, a combination of TDM/TDMA and DAMA technologies can be recommended. The latter of them will provide telephone and fax communications, make it possible to organize audio and video conferencing, while using the TDM/TDMA subnet it will be possible to transmit data.

Usually, in order to develop the optimal network solution, calculate the cost of several options for building a network (based on one or more technologies) under different loading modes. If you plan to develop a network, then in order to correctly select a technology (of course, from among those suitable for providing the telecommunications services required by the enterprise), in addition to the cost of implementing the initial version of the network, you should evaluate the total cost of ownership of one user station and the change in this indicator as their number increases. When constructing the graphs presented in the figure, it was assumed that user stations are equipped with one data port with a traffic of 10 MB per month and one telephone port with a traffic of 1000 minutes per month, and the network has a star topology. As can be seen in the figure, in a network with 10 user stations, if TDM/TDMA technology is used, the total cost of owning one such station for three years will be quite large - approximately $110,000, but with the growth of the network it will become very quickly decrease. In small networks it is much cheaper to use SCPC or TDMA terminals, however, when the number of such terminals becomes more than 50, they are more expensive than TDM/TDMA user stations. It should be noted that the total cost of ownership of a station is greatly influenced by its load.

I would like to give some general advice regarding the optimal choice of equipment and its manufacturers. Firstly, it is worth analyzing the experience of other companies that have already been operating the equipment you are interested in for at least one year. Secondly, collect as much as possible more information about the equipment manufacturer itself, including its experience in the market, current financial situation, quality of support provided in planning and operating the network. Please note that it is possible to provide various services communications within a single hardware platform of a particular manufacturer, the degree of its integration with other platforms of the same manufacturer and whether it has certificates of compliance with Russian and international standards. The absence of these certificates can lead to complete failure during the implementation of the network project.

Many enterprises take the path of creating their own telecommunications departments, entrusting the development, construction and further operation of the corporate network to their employees. At the same time, they gain full control over their networks and save on paying for third-party services. However, it is not always possible for enterprises to hire highly qualified personnel with knowledge of the technologies that are expected to be used in the future network, and the additional costs of training such personnel and solving complex problems that often arise during the implementation of the project can significantly exceed the amounts saved.

At the same time, operating the network will require obtaining various permits, and this is a rather labor-intensive, expensive and time-consuming procedure. It is easier, and often cheaper, to use the services of a well-known operator who has experience in implementing similar projects and the necessary licenses. If an enterprise wants to independently control and maintain its network, i.e. to be its operator, an external operator can only be used at the stages of development and implementation of a network project. During this time, the enterprise's own specialists will be able to receive the necessary training in order to then take over the administration and maintenance of the entire network.

However, an enterprise does not necessarily have to build its own network, since all the communication services it needs (including leasing user stations) can be provided by an operator that already operates a similar infrastructure. This will allow the enterprise to avoid the financial risk associated with large investments in the design and construction of its network. If ownership of the network is of fundamental importance for him, then over time he can buy out the stations and, when the network reaches a significant scale and the satellite technology used in it proves its effectiveness in meeting the telecommunications needs of users, rent the resource of a satellite repeater, build his own central station and switch user stations to it.

So, the network has been built and put into operation. However for successful work it must be properly maintained. The fact is that even the most reliable equipment sometimes breaks down. According to statistics, the maximum number of malfunctions occurs in the first year of its operation. Naturally, manufacturers provide warranty repair of your equipment, but this is a lengthy process - from a month or more. In this regard, the enterprise needs to have its own warehouse of spare parts for all types of electronic equipment of the network, and for this it is necessary to allocate premises and hire people who will sell these spare parts, store, transport them, etc. In addition, it will require qualified specialists who are ready to go to the installation site of faulty equipment with spare parts and measuring instruments as soon as possible. It should be noted that purchasing measuring equipment and maintaining it in working condition requires significant costs.

For an enterprise, maintaining the network on its own is economically justified only with a large (more than 100) number of stations. That is why many corporate clients around the world, including in Russia, prefer that this be done by operators who already service a large number of networks and have a staff of highly qualified service specialists, a warehouse of spare parts and the necessary measuring equipment. satellite communication telecommunication telephone

In conclusion, I would like to give one more piece of advice: when choosing satellite technology for your enterprise, try to develop a unified concept for the use of communication tools within offices, basic network software and infrastructure for information exchange between branches. This approach will allow you to select the optimal combination of communication technologies and ensure the flexible functioning of your communication infrastructure for many years to come.

Posted on Allbest.ru

Service maintenance.

After putting the satellite communication earth station (SECS) into operation, our company’s specialists will provide professional warranty and post-warranty service.

Technical Customer Support

For the first time, the client meets with a technical support engineer almost immediately after signing the contract, when a specialist from our company decides on the spot about the installation point of the satellite communication station and clarifies all the necessary details.

We pay close attention to the client not only at the project implementation stage. After the network is installed, our familiar team of specialists is always ready to help.

The technical support team will be sent to you as soon as possible in case of problems with the equipment.

Training your staff

As part of the project implementation, Iman DV specialists will conduct the necessary training for your personnel responsible for the operation of communication equipment.

Network maintenance

At the network creation stage, it is not always possible to foresee all the needs that may arise in the future. Iman DV specialists, using the capabilities of operator monitoring centers, analyze the customer’s network parameters, on the basis of which recommendations are made on making certain decisions.

Customer information support

We provide information support to clients. Our managers will keep in touch with you, inform you about new technologies and solutions that you need.

Information about our new services and events in the company, announcements of technical articles written by employees of our company will be sent to your email inbox.

What is VSAT?

Very Small Aperture Terminal (VSAT) is a device known as an earth station used to receive and transmit data through a satellite. The phrase "very small" in the VSAT acronym refers to the size of the VSAT antenna, typically 0.55-1.2 m in diameter, which is mounted on a roof or wall, or placed on the ground. This size corresponds to the Ku transmission band, which, as noted in the Satellites Basics section, is used primarily for operational systems. To transmit data in the C band, you need a slightly larger antenna - 1.8 m.

The antenna, along with the accompanying low noise converter unit, or LNB (which amplifies signals received from the satellite), and transmitter make up the VSAT outdoor unit (ODU), the first of two parts of the VSAT package.

The second part of the VSAT kit is the indoor unit (IDU). Indoor unit is a small desktop device that converts information passing between analog communications on a satellite and local devices such as telephones, computer networks, PCs, TVs, etc. In addition to the basic conversion programs, IDUs may also contain additional features such as security, network acceleration, and other features. The indoor unit is connected to the outdoor unit via 2 cables.

The main advantage of a VSAT earth station over a conventional terrestrial connection is that VSAT sets are not limited by the reach of cables running underground. A VSAT earth station can be installed anywhere - as long as there is clear visibility of the satellite. VSAT stations can transmit and receive any video, audio and other data at a constant high speed, regardless of their distance from ground communications stations and infrastructure.

How does the VSAT network work?

The VSAT network consists of three main components:

Central Earth Station (CZS or satellite HUB)
Satellite
Virtually unlimited number of VSAT earth stations in various locations - across the country or continent

The content mainly originates from the CZS. This is also where the equipment and software, used for monitoring satellite communications. The central station typically has a connection to a communications network, which is either the public telephone network in a large city, a company's central computer network, or an Internet backbone.

The most prominent part of the CZS is the large, 4.5-11 m (15-36 ft) antenna. Internal elements include a variety of devices that control two-way antenna transmissions, conversions between satellite and terrestrial protocols, and other technical issues. The network management system server controls the functioning of all devices and also distributes the order of message transmission to applications depending on the customer's quality of service requirements.

As described earlier, VSATs are devices used in remote locations to provide communication to a central communications location through a central earth station.

In the simplest design, the outgoing information (from the central station to the VSATs) is sent to the satellite transponder, which receives it, amplifies it and transmits it back to the ground for reception by a distant VSAT station. The remote VSAT station sends information (from the stations to the central station) via the same satellite transponder.

This mechanism, in which all network communications pass through the DSP processor, is called a "star", with the DSP at the center of the star. One of the most important advantages of this mechanism is that there is virtually no limit to the number of VSAT stations that can be connected to the central station.

Network topology

As noted above, a star topology is the easiest way to set up a satellite network. At the same time, it has one controversial issue that affects the characteristics. Remember that a satellite in geostationary orbit is 35,400 km from the Earth's surface. This means that message transmission takes certain time. Because of the distance, transferring 1 bit of information from one place to another (a single "hop") takes about a quarter of a second. If a transmission occurs from one VSAT station to another such station, the star topology requires two hops, resulting in a half-second delay.

This time delay is practically irrelevant when transferring data between two computers, for example, to update databases. In addition, the star topology allows VSAT stations to use smaller antennas and lower power transmitters because they operate from a single large central antenna.

However, the latency of a star topology may become noticeable during voice transmission. Therefore, a star topology is best used when messages are transmitted between the central system and remote stations in one hop, or when transmissions from one VSAT station to another do not require instantaneous response.

The mesh network topology allows VSAT to communicate directly with other VSAT stations, minimizing latency on multicast transmissions. This means, for example, that phone conversation between people talking on phones connected by a VSAT network have a single jump that is imperceptible to most people. Mesh IP supports one-hop data transmission for computer applications, such as client/server software that requires instantaneous two-way communication between computers at remote locations.

Multi-star topologies provide a combination of star and mesh topologies, in which the central station sends information to VSAT stations and the VSATs have the ability to transmit directly over the network. This makes it possible, for example, using a VoIP phone at one VSAT station to communicate directly with an available telephony network via a second VSAT station. In another example, a multinational company's corporate server could send database updates from the central command center to government headquarters via a single VSAT station, which could then relay the information to regional offices.

Due to differences in price and features, a cost-benefit analysis is required to understand which topology is applicable in each case in order to create the appropriate network topology for your needs.

iDirect technology

iDirect technology is one of the most efficient satellite systems on the VSAT market. iDirect provides efficient use bandwidth, both on the satellite segment and at the IP protocol level, which suggests a low cost of operating the system for a service provider or telecom operator.

iDirect technology is designed specifically for corporate clients transmitting or receiving large amounts of data. Technologies for efficient transmission of latency-critical Real-time traffic, such as VoIP and multimedia streams, have been fully implemented. The system is based on the new D-TDMA (Deterministic Time Division Multiple Access) technology, its essence is as follows - many remote VSAT terminals, sharing the same channel, “compete” for the available bandwidth necessary for receiving/transmitting information .

The technology, in its essence, is very close to Ethernet - when you add a large number of users, collisions begin to occur in the network, in which several users request the band at the same time. In practice, such collisions are transparent when using WWW, E-mail, FTP and similar information delivery applications, but VoIP and streaming tasks require a different approach to information transfer and “competition” for bandwidth.

The iDirect system offers the user a combined solution - D-TDMA technology and bandwidth reservation (CIR) for transmitting multimedia streams. D-TDMA technology, by providing a dedicated time slot to each client, allows iDirect remote terminals not to "compete" for available bandwidth, but to always receive it when the application requires it. The iDirect remote terminal receives a dedicated time slot every 1/8 second - this allows the data to be framed, avoiding the effects of jitter and providing guaranteed quality of a continuous real-time stream:

Another difference between iDirect and other TDMA systems is the use of a 125ms frame (versus 250ms in alternative solutions). This allows you to achieve minimal response time and ensure VoIP/Video transmission of guaranteed quality.

The equipment was developed using the results of many years of research and development in the field of TDMA access technology, satellite communications and software. As a result, iDirect equipment offers a unique combination of flexibility, operational reliability and cost-effectiveness. Compared to what providers of traditional satellite or terrestrial communication networks offer, the iDirect network has a number of undoubted competitive advantages.

Communication topologies

The iDirect technology used by MT supports all existing communication topologies. This allows you to organize the network most efficiently, using various hardware capabilities in accordance with the client’s tasks.

What is VSAT? This is a small satellite communication station with an antenna with a diameter of 0.9 - 3.7 m, designed primarily for reliable data exchange via satellite channels. It does not require maintenance and connects directly to the user's terminal equipment, acting as a wireless modem.

Example of a VSAT terminal.
How the VSAT network works

A VSAT-based satellite communication network includes three main elements: a central earth station (if necessary), a relay satellite and VSAT user terminals.
Central Earth Station (CES)
The central earth station in the satellite communications network at the base performs the functions of a central node and provides control of the operation of the entire network, redistribution of its resources, fault detection, tariffing of network services and interfacing with terrestrial communication lines. Typically, the central station is installed in the network node that receives the most traffic. This could be, for example, the main office or computer center of a company in corporate networks, or a large city in a regional network.

Example of a central earth station.
The transmitting and receiving equipment and the antenna-feeder device are usually built on the basis of standard equipment available on the market. The cost is determined by the size of the antenna and the power of the transmitter, which significantly depend on the technical characteristics of the relay satellite used. To ensure communication reliability, the equipment usually has 100% redundancy.
Channel-forming equipment ensures the formation of satellite radio channels and their connection with terrestrial communication lines. Each of the suppliers of satellite communication systems uses its own original solutions for this part of the central network, which often excludes the possibility of using equipment and subscriber stations from other companies to build a network. Typically, this subsystem is built on a modular basis, which makes it possible to easily add new blocks to increase its throughput as traffic and the number of subscriber stations in the network grow.

VSAT subscriber station
The VSAT subscriber terminal usually includes an antenna-feeder device, an external external
RF unit and internal unit (modem).
The external unit is a small transceiver or receiver. The internal unit ensures the connection of the satellite channel with the user's terminal equipment (computer, LAN server, telephone, fax PBX, etc.).

Satellite repeater
VSAT networks are built on the basis of geostationary relay satellites. This makes it possible to simplify the design of user terminals as much as possible and equip them with simple fixed antennas without a satellite tracking system. The satellite receives the signal from the earth station, amplifies it and sends it back to Earth.

The most important characteristics of a satellite are the power of onboard transmitters and the number of radio frequency channels (trunks or transponders) on it. To ensure operation through small subscriber stations such as VSAT, transmitters with an output power of about 40 W are required.

Traffic configuration

Point-to-point topology

A point-to-point network allows for direct duplex communication between two remote subscriber stations via dedicated channels. This communication scheme is most effective when the channels are heavily loaded (at least 30 - 40%).
The advantage of this architecture is the simplicity of organizing communication channels and their complete transparency for various exchange protocols. In addition, such a network does not require a management system.

Star topology

A star network is the most common architecture for constructing a network network with VSAT-class subscriber stations. Such a network provides multi-directional radial traffic between a central earth station (central earth station or HUB in English literature) and remote peripheral stations (terminals) according to an energy-efficient scheme: small earth station - large earth station, equipped with a large diameter antenna and a powerful transmitter.
The disadvantage of the star architecture is the presence of a double hop in communication between network terminals, which leads to noticeable signal delays. VSAT networks of similar architecture are widely used to organize information exchange between a large number of remote terminals that do not have significant mutual traffic, and the central office of the company, various transport, manufacturing and financial institutions.

Similarly, telephone communication networks are built to serve remote subscribers, who are provided with access to the public switched telephone network through a central station connected to a land-based switching center or automatic telephone exchange. Monitoring and management functions in a star network are usually centralized and concentrated in the central control station (CCS) of the network. The NCC performs service functions of establishing connections between network subscribers (both terrestrial and satellite terminals) and maintaining the operating status of all peripheral devices.
Typically, the functions of the central control center/central control center are combined in one complex, which serves as a traffic switch and an interface of the satellite network with terrestrial channels. In star-type networks created by large operators, one NCC resource can be provided to several autonomous VSAT subnetworks.

Topology type "each-with-everyone"

In the “everyone to everyone” network, direct connections are provided between any subscriber stations (the so-called “single-hop” communication mode).
The number of required duplex radio channels is N x (N - 1), where N is the number of subscriber stations in the network. In this case, each subscriber station must have N - 1 reception and transmission channels. This architecture is optimal for telephone networks created in hard-to-reach or remote areas, as well as for data networks with a relatively small number of remote terminals.
Due to the fact that VSAT requires greater energy resources to operate between two small terminals compared to a star network, in “each-to-each” networks at subscriber stations it is necessary to use more powerful transmitters and antennas of larger diameter, which significantly affects on their price. Each of these topologies has its own advantages and disadvantages. In real-world situations, there is often a need to provide a wide range of services, each of which is better implemented in different topologies. Therefore many
networks are built using mixed topologies.

Control type
With centralized management of such a network, the network control center (NCC) performs control and management functions necessary to establish connections between network subscribers, but does not participate in the transmission of traffic. Typically, the NCC is installed at one of the subscriber stations of the network, which receives the most traffic.
In the decentralized version of network management, there is no central control center, and elements of the management system are included in
each VSAT station. Similar networks with a distributed control system are characterized by increased “survivability” and
flexibility due to the complication of equipment, the expansion of its functionality and the rise in cost of VSAT terminals. This control scheme is appropriate only when creating small networks (up to 30 terminals) with high traffic between subscribers.

Advantages and disadvantages

Advantages

VSAT technology is very flexible and allows you to create networks that meet the most stringent requirements and provide a wide range of services for transmitting voice, video, data in any combination. In many cases, they have undeniable advantages over terrestrial networks:

low cost

fast deployment

high quality communication

architecture "star" and "everyone - with everyone"

ease of reconfiguration

high reliability.

Application:

image transfer

video conferences

Internet access

multimedia

Currently, the cost of one minute of conversation over a satellite communication channel ranges from 3 to 15 cents, and modern VSAT terminals cost from 3 to 5 thousand dollars in a basic configuration and provide transmission speeds from 16 kbit/s to 2 or more Mbit/s .
Installing and connecting a VSAT class terminal to the network takes several hours.
VSAT networks provide reliability of digital information transmission worse than 1* 10 -7, i.e. no more than one error per 10 million bits of information transmitted, which corresponds to approximately one error per 500 pages of text information.

Modern VSAT class terminals make it possible to build communication networks of various architectures and purposes. Network reconfiguration, including changing exchange protocols, adding new terminals or changing their geographical location, is carried out very quickly. VSAT class terminals provide reliability for up to 100 thousand hours.

The popularity of VSAT in comparison with other types of communication when creating corporate networks is explained by the following considerations: for networks with a large number of terminals and with significant distances between subscribers, operating costs are significantly lower than when using terrestrial networks:

Complete independence from terrestrial network operators

Speed of network deployment and reconfiguration

High reliability reaching 99.9%

Flaws

Satellite communications are a type of radio communications. Therefore, theoretically, any satellite station located in the satellite’s service area, if it is tuned to the right frequency, the right time interval, supports the right protocols and operates in the right standard, could intercept signals. But, firstly, it is necessary to fulfill all the listed conditions (at the same time!). Secondly, satellite communication systems use powerful signal coding systems, which makes interception almost impossible. We should also not forget that the same problems arise in any other communication channel, not just satellite. Satellite signals, especially high-frequency Ku and Ka bands, are susceptible to attenuation in humid atmospheres (rain, fog, clouds). This drawback is easily overcome when designing the system; as a result, the average availability of a satellite communication channel is usually no worse than 99.9%. The reliability of terrestrial channels is often lower.

Like any other radio communication system, satellite communications are subject to interference from other radio media. However, on the one hand, frequency bands are allocated for satellite communications that are not used by other radio systems. On the other hand, satellite systems use highly directional antennas to completely eliminate interference.

Thus, most of the shortcomings of satellite communication systems are eliminated through proper network design, choice of technology and antenna installation location. It should be noted that any communication system has its disadvantages and advantages, and the choice of a particular technology depends on many factors.

History of VSAT networks
The history of networks begins with the launch of the first communication satellites. In the late 60s, during experiments with the ATS-1 satellite, an experimental satellite telephone network was created in Alaska. The network consisted of 25 earth stations installed in small villages. The experiment was successful, and it was decided to create a commercial satellite telephone network of 100 terminals using channels to the Intelsat satellite.

At that time, the “smallest” satellite station had an antenna with a diameter of 9 m and cost about 500 thousand dollars. The customers set the condition: the antennas of the earth stations of the network should be no more than 4.5 m, and the price should not exceed 50 thousand dollars. And Such earth stations were created by California Microwaves.

The idea of creating even smaller and cheaper satellite communication stations attracted the interest of a group of developers working on a project in Alaska. In 1979, they created the Equatorial Communications Company, which became the world's first company to develop VSAT systems.

When creating a low-cost portable VSAT earth station, two major problems had to be solved. The first of them is, in fact, its dimensions, primarily the diameter of the antenna. At that time, commercial communications satellites did not have enough power to operate with standard earth stations with an antenna mirror diameter of less than 3 m. The second problem was the creation of inexpensive, highly stable electronic equipment.

The company's engineers coped with the tasks very gracefully, using the latest advances in the field of electronics and telecommunications. The first problem was solved by using channel division code using a wideband noise-like signal. Stability problem electronic equipment was solved by replacing conventional highly stable, and therefore expensive, electronic components with an inexpensive microprocessor circuit with an automatic frequency and phase adjustment system. A prototype of a purely receiving satellite station, developed on these principles, was ready in 1979. Even today it represents an example of the perfection of technical thought. It had an antenna with a diameter of only 60 cm and cost about $2,000. The first several thousand of these receiving stations were used in the network for distributing stock exchange and price information.
Work on interactive small-sized satellite communication stations began in 1982. It was then that the term VSAT appeared. The first prototypes were tested at the end of 1983. In 1984, an experimental VSAT network was established, and commercial VSAT deliveries began in 1985. The first interactive VSATs had 1.8 m diameter antennas and cost about $6,000. They were designed to support transactions, and the network's first customer was Farmers Insurance.
The first successes of Equatorial in creating cost-effective satellite communication systems based on VSAT gave
spurred the emergence of several new firms offering VSAT equipment. The market began to develop rapidly and
Competition on it has increased sharply.
Finally, the whales of the telecommunications business paid attention to the market and, without further ado, began
buy companies that are successfully developing in the market. American telecommunications giant AT&T acquired Tridom. Ku-band VSAT pioneer Linkabit has merged with M/A-COM, which has become a leading supplier of VSAT equipment. Hughes Communications subsequently acquired the division from M/A-COM.
This is how Hughes Network Systems was born. Scientific-Atlanta, a manufacturer of large satellite communications stations, entered the VSAT equipment business with the acquisition of Adcom. GTE Spacenet initially provided VSAT services using equipment from other suppliers. Equatorial merged with Contel in 1987, which simultaneously acquired the VSAT division of Comsat. And in 1991, GTE Sapacenet acquired Contel. In 1987, the company's founders created a new company - Gilat Satellite Networks Ltd. for VSAT production.
Thus, a main pool of players in the VSAT production market was formed, which continues to this day.

VSAT Generations
There are several types of VSAT earth stations. They can be roughly divided into three generations. Everyone's appearance
new generation VSAT became possible as new technologies emerged, more powerful
communication satellites and the development of new frequency ranges.
The first generation VSATs operated in the C-band and were used only in broadcast-type networks, i.e. subscriber terminals could only receive data streams from the central station, and the transmission mode was not provided for in them. Broadcast-type networks are still widely used for the distribution of financial and business information, stock market reports, transmission of newspaper strips, and in asymmetric Internet access systems. For example, the well-known DirecPC high-speed Internet access system is essentially a satellite broadcast network.
The second generation of VSAT earth stations is characterized by the fact that they can support two-way (duplex)
connection. These terminals are used by banking and financial organizations in various computer networks for data exchange, retail and wholesale trade networks, industrial enterprises for communication with branches and suppliers. They have also found wide application for organizing high-speed two-way access in
Internet. VSAT stations are also used by telecom operators to create dedicated trunk channels between remote nodes with a large volume of data exchange between them. Most of them operate in Ku-band, although in some countries networks still use C-band.
Third-generation terminals with antennas with a diameter of 1.2 m or less have become widespread. They are used in large networks with low levels of traffic between them. At the same time, traffic is sporadic (unstable) in nature. Such terminals are simple in design, low in price and operate exclusively in the Ku-band.
In recent years, the fourth generation of VSAT for multimedia applications has appeared on the market. They work in
Ku- and Ka-bands and provide speeds of up to several megabits per second. Moreover, the size of their antennas (in the Ka-band) is approximately 70 cm, and the price is in the range of 500-1000 dollars.

Corporate satellite networks

Recently, there has been a growing need for large enterprises to create extensive corporate networks connecting central offices with branches in the regions of the country. Today, not only stable data transmission is required, but also high-quality telephone communications, video conferencing services, and Internet access. Due to the vast geography of our country and the lack of terrestrial communications in many regions of Siberia and the Far East, to solve these problems it is necessary, and sometimes the only possible way, to use satellite communications.
Satellite communications make it possible to create autonomous corporate networks for companies with geographically distributed office infrastructure. Modern VSAT technologies offer multifunctional and effective solutions for organizing the transmission of corporate information.
To create corporate satellite network projects, Stratos-MT uses the most advanced technologies available on the international market. This is the classic technology of dedicated channels using Comtech satellite modems, as well as the latest broadband access technologies from iDirect and ND Satcom. Before offering any technology as part of a solution, Stratos-MT conducts thorough testing of new developments from equipment suppliers.
Unlike manufacturers who offer equipment only from their own production, Stratos-MT provides optimal solutions using various technologies and platforms.
The selection of technologies is based on an analysis of the customer’s traffic and needs, as well as based on the prospects for the development of his business.
The solution offered to the customer can be based on various interrelated technologies. Moreover, the solution may include the ability to migrate from one technology to another.
This approach allows us to determine the most cost-effective and efficient solution that meets the customer's requirements, moreover, it allows the customer's network to grow along with his business.

Stratos-MT offers clients the following solutions for building corporate networks:

Corporate network using Stratos-MT Central Station

A corporate network of this type allows the customer to quickly organize the exchange of information in its distributed structure and gain access to the main telecommunications nodes in Moscow (MMTS-9, MMTS-10, Main Control Center MS). This will allow the corporate network to use international and transcontinental channels, as well as connect to the Internet and VoIP service providers.
The number of terminals in the network ranges from a few to hundreds. A network of this type can be dedicated, or be part of a public multiservice network centered in Moscow.
The network can be built using star and fully connected topologies.

Local corporate network with a center at the Customer’s office

A local corporate network differs from the previous one in that the central station of the network is located at the switching center or the central office of the customer. The client receives an autonomous solution and flexible management own network.
This network organization allows for more efficient use of satellite resources and, accordingly, is more economical for traffic between the center and remote stations if the central station is not located in Moscow.
The organization of a local satellite network is optimal for communication between 2-30 remote stations, when solving problems is extremely necessary corporate telephony, conference calls, real-time or high-intensity traffic transit.
The network can be built using star, fully connected, mixed topologies. In networks of this type, a common bandwidth resource is allocated, which can be quickly distributed between remote stations.
At the customer's request, for individual network nodes, including the central one, it is possible to organize a channel to the Stratos-MT central station in Moscow to provide high-speed Internet access and other services.

Corporate network using mobile stations

Many customers set the task of building local corporate networks using mobile stations. A typical example is a company, usually in the oil and gas sector, that needs a corporate network connecting the central office with the fields being developed. The use of VSAT terminals with antennas with a diameter of 1.2 and 1.8 meters allows you to quickly move a station within the service area of the satellite in use, without carrying out an expensive and sometimes lengthy permitting procedure.
The network can be either local or centered in Moscow and is built using star and fully connected topologies. fully connected.

Backup corporate network

One of the most important parameters organization of a corporate network is its reliability. But even organizing a network via terrestrial channels does not guarantee 100% reliability. One of the most effective ways to increase reliability is to organize a satellite backup network.
Organizing a backup corporate network allows you to back up not only the entire network, but also its individual directions. The resources of the backup network can also be used when the main network is overloaded. Since the total network capacity can be quickly distributed between directions, this resource can be significantly less than the main resource. Thus, the costs of operating a backup network are usually low and can be significantly lower than the damage associated with failures of the main network

Technologies used

To create a corporate satellite communications network, we offer technologies and platforms based on effective ways to use satellite resources:

TechnologyMCPC (Multichannel Per Carrier)

Each station implementing MCPC has a dedicated segment of satellite transponder capacity and maintains a persistent connection.
The main advantage of these technologies is that they guarantee the necessary throughput of the satellite communication channel at any time.
This technology is effective in networks with a star topology for organizing fixed channels in several directions.
Typically, MCPC technology is used for high-bandwidth, high-load networks.

Specifications:

Optimal number of network nodes using the technology: up to 10
Data transfer rate from the interstationary station: up to 10 Mbit/s Method of access to the space segment - MCPC, rokadal communications - DAMA
Transport protocol: Frame Relay, IP
QoS, IP header and payload compression
The terminal consists of an antenna (1.2 - 3.8 meters), a transceiver (from 2 W), a satellite modem and a router (can be part of the client’s equipment)

Technologistand TDMA (Time-Division Multiple Access)

Using the ND SATCOM platform (SKYWAN®)

SkyWAN® technology is a flexible and universal system for organizing satellite corporate Frame Relay and IP networks focused on various types of applications.
The system operates on the principle of dynamic distribution of satellite resources. The resource is redistributed as efficiently as possible between network stations in accordance with their needs. The distribution of different types of traffic is carried out continuously in accordance with the quality of service and a multi-level traffic prioritization system. SkyWan technology is most effective for networks with a fully meshed topology.

Specifications:

Optimal number of network nodes: 10 – 50
Data transfer rate from MZS: up to 8 Mbit/s
Data transfer rate to MZS: up to 8 Mbit/s
Network topology: star, mesh, hybrid
Transport protocols: Frame Relay, IP
Space segment access method: TDMA with frequency hopping implementation
PVC organization with individual meaning CIR
Terminal components: antenna (1.8 - 3.8 meters), transceiver (from 2 W), TDMA modem, router or FRAD (may be part of the user equipment)

Using the platformiDirect

iDirect equipment offers a unique combination of flexibility, reliability and cost-effectiveness.
Basic operating principles:
Data streams in the iDirect network channels from the central station to the remote ones (DownStream) are formed using TDM (time division) technology, which allows several remote stations to share the throughput of the downstream channel.
The iDirect system assigns and reallocates bandwidth to each remote station based on its traffic demand and quality of service limitations set by the network operator. The central station analyzes the needs of all remote stations and assigns the frequency band they need.
The remote station can transmit data in its allocated time slots for primary traffic. If a large frequency band is required, it can be provided with a frequency band in another return channel, which has a free frequency band of the required width (“frequency hopping”).
Most effective for networks with a star topology and low overall throughput

Specifications:

Optimal number of network nodes: 5 – 200
Data transfer rate from remote station: up to 4 Mbit/s
Data transfer rate to remote station: up to 18 Mbit/s
Network topology: star, Mesh for RTP traffic
Transport protocols: TCP, UDP, ICMP, IGMP, etc., RIP v.2 routing
The D-TDMA method of access to the space segment works on the principle of dynamically assigning time slots to remote devices for transmitting information, depending on the current requirements of the remote party for bandwidth and quality of service
Advanced QoS service prioritization
TCP acceleration and data compression
The terminal consists of: antenna (1.2 - 2.4 meters), transceiver (from 2 W), TDMA modem, additional equipment for organizing VoIP and videoconferencing if necessary.

Composition of the service and commercial terms of provision

Obtaining permits
Commissioning of the AP
Providing satellite resource
Renting a gateway station resource in Moscow
24/7 technical user support
VSAT service throughout the entire period of service provision.

A one-time initial payment includes the provision of equipment to the AP, inspection of the installation site, installation, commissioning, registration of the AP, allocation of the resource of the central station.

Monthly payments include servicing of the AP, spare parts, rental of satellite resource, central station resource, monitoring of the AP and 24-hour Hotline technical support service.

Certification
The activities of Stratos-MT are licensed by the Ministry of Telecom and Mass Communications. All provided equipment is certified for use on the territory of the Russian Federation. Registration of the client's earth station is carried out as soon as possible in strict accordance with the current legislation of the Russian Federation.

Selecting a satellite determined at the network planning stage based on an analysis of the customer’s requirements and infrastructure.

Central gateway station Stratos-MT can be used to access the central office network or external Russian and international networks, and also provides high-speed access to the national M9 traffic exchange node. It can also host the customer’s network management and monitoring system.

To ensure the operation of the network, Stratos-MT resources can be used. Our specialists technical support services and 24x7 Hotline provide consultations, perform remote configuration and travel to places where faults occur in the shortest possible time. Located in Moscow spare parts warehouse, which may contain the client's spare parts.

As part of the project implementation, our specialists carry out the necessary training of customer personnel , responsible for the operation of communication equipment. If the client decides to independently maintain the functionality of his network, he is trained in network maintenance.

New network support service . At the network creation stage, it is not always possible to foresee all the needs that may arise in the future. Stratos-MT specialists, based on data from our monitoring center, systematically analyze the customer’s network parameters, on the basis of which recommendations are made for activating certain applications.

Dedicated satellite channels

The organization of satellite communication channels allows regional operators and other users to quickly connect to modern digital networks anywhere in the country, as well as connect between any points in Russia, the CIS, and the world. The service for providing a satellite communication channel allows you to get modern communications without large initial investments.

Main characteristics

The service is based on technology SCPC (Single Channel Per Carrier). The channel is organized according to a point-to-point scheme, and one of the points may be the MT Central Gateway Station (CS), located in Moscow. This technology is used both for public telephone and data networks and for private networks.

Modern modulation methods (QPSK/8PSK/16QAM) and noise-resistant coding of the transmitted signal (TPC, LDPC) used in the service significantly reduce operating costs and expand the service area.

The main advantage of SCPC technology is that the channel resource is dedicated and is not redistributed among other users.

Currently, Stratos-MT offers the latest Carrier-in-Carrier (CnC) technology for use. This technology allows you to use the same frequencies for the forward and return channels. At the same time, savings in the used satellite resource compared to SCPC can reach 40% and are especially effective for symmetric channels with a data transfer rate of more than 1 Mbit/s.

Composition of the service

Supply and installation of equipment

Obtaining permits

Provision of satellite resource for rent

Renting a resource for the Stratos-MT gateway station

24-hour technical customer support and VSAT service throughout the entire service period

To organize this service, modern communication satellites with high energy performance are used, such as:

Intelsat-904

Standing point - 60 east.

Band used - Ku

EIRP max - 53 dBW

Territory - Russia from Kaliningrad to

Irkutsk, CIS countries

Yamal-201

Standing point - 90 east.

Range used - Ku, C

EIRP max - 49 dBW

Territory - Russia from Petrozavodsk to

Magadan, CIS countries

Express-AM3

Standing point - 140 east.

Range used - C, Ku

EIRP max - 47 dBW

Territory - Russia: Far East and

Northeast region

Express-AM33

Standing point - 96.5° east.

Band used - Ku, C

EIRP max - 55 dBW and 48 dBW

Territory - Russia: Central part

and Western Siberia for Ku band; from

Moscow to Magadan for C band

Express-AM44

Standing point - 11° west.

Band used - Ku, C

EIRP max - 55 dBW and 48 dBW

Territory – Europe, Western part

Russia, Africa

Satellite Internet access channel

The use of satellite communication channels allows regional operators and Internet providers to obtain broadband Internet access in the shortest possible time and anywhere in the country, regardless of the availability and condition of terrestrial telecommunications infrastructure.

Description and benefits of the service

This service can be implemented based on the following technologies: SCPC (Single Channel Per Carrier) and TDM/TDMA (Time Division Multiplexing/Time Division Multiply Access).

When using TDM/TDMA technology, quality of service (QoS) control is provided by means of the CA traffic management system, which allocates to each user a certain guaranteed throughput (CIR) in the group Internet access channel. The channel's free resource (PIR) at a specific point in time is distributed among users in proportion to the CIR specified for them. The sum of CIR of concurrent users does not exceed the total channel capacity (thus, overbooking is prevented), which guarantees all users of this service an access speed not lower than the CIR value at any time.

Ensuring uninterrupted operation of the client’s station is provided by the 24x7 Hotline service and technical support service.

Main characteristics

Composition of a transceiver earth station

Parabolic antenna from 1.2 m or more

Up converter and power amplifier (transmitter) from 3 W or more

Low noise amplifier and down converter (converter)

Intermediate frequency cable

Satellite modem

Router (optional)

Central station-gateway in Moscow

Access to telecommunication networks

IP telephony support

Network management and monitoring system

The service does not impose restrictions on the use of Internet protocols and services and does not require additional filtering of user traffic.

Satellite communications for the fuel and energy sector

The geographically distributed structure of fuel and energy enterprises, hard-to-reach and sparsely populated areas of fuel production and transportation, undeveloped infrastructure - such features have made satellite communications for companies in this sector of the economy not just preferable, but often the only one available.

CJSC "Moscow Teleport" is ready to provide fuel and energy enterprises with various solutions for both fixed and mobile satellite communications, allowing them to create connectivity and a “mobile office” almost all over the world.

Fixed satellite communications

Today, VSAT technologies are used by oil and gas companies that need constant control over a pipeline over a large area, pumping stations and storage facilities, companies that own gas station networks that require constant control over fuel consumption, timely delivery of products to gas stations, connection of cash registers, ATMs, payphones , and all this in real time. In this case, your own dedicated network via satellite is more efficient than communications serviced by different operators.

Stratos-MT has extensive experience in providing reliable and efficient communications to oil and gas companies operating in various industry segments.

At the stage of geological and geophysical research, Stratos-MT provides:

Operational communication (telephony, e-mail) with the head office
Access to corporate network information servers (databases, etc.)
Prompt transfer of received measurements to the information processing center
Video conferencing for operational guidance and situation analysis

At the stage of production and transportation (UpStream), Stratos-MT provides:

Operational communication (telephony, e-mail) for drilling rigs;
Video conferencing;
Management and collection of data from raw material production and transportation facilities
Reservation of communication channels for production facilities, primary preparation of oil transportation;

At the stage of processing and sales (DownStream), Stratos-MT provides:

Construction of data transmission networks for gas stations and oil depots
Video conferencing
Reservation of communication channels in corporate networks
Management and collection of data from processing facilities
Modern telecommunications (Internet, long-distance telephony) for remote sites.

The Stratos-MT service portfolio covers all modern VSAT applications and includes:

Corporate networks using the Stratos-MT central station in Moscow
Local corporate networks with a center in the Customer’s office
Local networks using mobile stations
Backup corporate networks

Dedicated point-to-point channels
Access to the Internet
Channels for redundancy of terrestrial communication infrastructure

For small and medium-sized fuel and energy companies, Stratos-MT offers its new product - MTek.

MTek, based on the iDirect platform, is a cost-effective, IP-based solution that provides constant high-speed Internet connection, organization of internal corporate and telephone network. MTek can use mobile terminals, which is a radical departure from traditional satellite broadband services offered. Mobile terminals can be installed on mobile oil platforms, cars, and other mobile objects.

AdvantagesMTek

Full range of services from one operator
Flexible, economically optimal approach to customer requirements
Reliable broadband solution
Full scalability
Technical support 24x7

Thus, MTek is a completely independent solution from ground infrastructure, combining reliable secure communications, global service area, flexibility and scalability, which meets almost any requirements of our customers.

Mobile satellite communication

An alternative fixed satellite communications option is provided by Inmarsat's BGAN mobile satellite communications.

BGAN Inmarsat satellite communication system was created from the very beginning for users on the move or in areas with a lack of traditional communications.

Over thirty years of successful operation of the system A number of systems have been created to meet the various needs of mobile users for communication services.

BGAN Inmarsat

Broadband in Action

Use of Inmarsat BGAN in the early stages of exploration work is a typical area of its application. It is most likely that exploration specialists will be constantly on the move and will not be able to carry bulky equipment to analyze samples in the field, as they will need to send raw data back to the base for more complex analysis. The faster they receive processed data, the faster they know where to conduct further exploration. BGANInmarsat provides them with the opportunity to communicate with colleagues at the base or anywhere in the field at any time.

TInmarsat's BGAN can also play an important role once new fields are operational. Certification engineers and inspectors who travel between remote sites and along pipelines to troubleshoot problems or report on repair progress can use this system as their primary means of communication. They can maintain constant contact with head office and with colleagues at sites who also have an Inmarsat BGAN terminal.

ServicesBGAN Inmarsat:

Principal capabilities provided by the Inmarsat BGAN system:

Batch and streaming data transfer (speed up to 492 kbps)
Access to private corporate networks (VPN)
Internet, Email
Telephony, fax, possibility of simultaneous data transfer
Direct text messages (SMS) from a terminal without using a laptop

Benefits of BGAN Inmarsat

Security of information (BGAN meets all security requirements and supports the most stringent information security standards)

Mobile satellite communication services BGAN Inmarsat

The worldwide communications system BGAN (Broadband Global Area Network) includes satellites and coast earth stations providing reception/transmission speeds of up to 492 kbit/s. Mobile terminals are used as client equipment in the Inmarsat BGAN network, through which the user connects to Inmarsat high-speed satellite channels.

To work in the BGAN Inmarsat network New terminals have been developed to meet the increased capabilities of the network. In addition, Inmarsat's new BGAN terminals allow parallel telephone communications. A line of terminals has been developed for use in the BGAN network EXPLORER 300, EXPLORER 500, EXPLORER 700.

BGAN Inmarsat is an excellent solution for providing redundancy to an organization's existing terrestrial and satellite telecommunications infrastructure.

AdvantagesBGAN Inmarsat:

Global coverage of the earth's surface (about 82%)
High data transfer speed (up to 492 kbps)
Portability (full laptop size)
Ease of use (fast deployment, simple and user-friendly interface)
Security of information ( BGAN meets all security requirements and supports the most stringent information security standards

ServicesBGAN Inmarsat:

Fundamental capabilities provided by the Inmarsat BGAN system:

Batch and streaming data transfer (speed up to 492 kbps) - regardless of location, the user can be sure that downloading a 10-MB file will take no more than 5-6 minutes. In the packet data transfer mode, the user is constantly connected with payment for communication services according to the transmitted (and received) volumes of data without payment downtime.

Access to private corporate networks (VPN) - virtual private networks (VPN connections) provide convenient and quick access to corporate information, secure data exchange, make modern means of communication available, and ensure full-fledged operation of office programs and IT applications

Internet, email- mobile high-speed access to the Internet and e-mail to corporate networks through a compact and lightweight portable satellite Internet modem (user terminal).

Telephony, fax, possibility of simultaneous data transfer - all models of BGAN terminals provide simultaneous transmission of voice telephony and IP data transmission.

Direct text messages (SMS) from a terminal without using a laptop

BGAN coverage areaInmarsat

Composition of Services

The service includes:

Sales of subscriber equipment
Providing subscriber equipment for rent
Connecting equipment according to the selected tariff plan
Service support for equipment during the warranty period

Tariff plans for the Inmarsat BGAN system

"Standard"
"Base"
"Russia"

Package plans for the Inmarsat BGAN system

"Starting"
"Average"
"Super"
"Super+"

Wide range tariff plans for the BGAN system allows users to make maximum use of the system's extensive capabilities at optimal cost.

VSAT based solution for river and sea vessels

The increase in the volume of information in the modern world could not but affect the development of satellite communication systems, both on land and at sea.
To organize reliable communications at sea, VSAT technology, already well-proven and well-known on shore, is used today. Unlike mobile satellite communication systems provided by Inmarsat and GlobalStar, the initial installation of a satellite terminal is quite expensive, these investments quickly pay off due to savings on traffic. In addition, the client is provided with services not only voice communication, but also the ability to transmit video, as well as the Internet on the ship and monitoring systems for various types of floating objects using the VSAT system.

Marine VSAT

The main function of marine VSAT is the organization of full-fledged high-speed communications on sea and river vessels via a satellite channel. The use of broadband satellite communications equipment based on VSAT technology in currently meets all the requirements for modern, high-speed, permanent communication with ships and floating structures:

Based on the IP protocol
Provides high speed information transfer
Provides the ability to integrate communication services
Uses C or Ku band frequency spectrum
Allows the use of satellites with a large coverage area
Does not require lengthy installation of a set of ship equipment
Provides quick payback on equipment costs
Helps reduce operating costs
Provides continuous, reliable and high-quality communication with ships

Services are implemented on the basis of high-speed satellite channels to solve the following problems:

Increasing efficiency in the activities of shipping companies, using the integration of company vessels into a single corporate network with the implementation of modern communication services
Introduction of modern information technologies into management systems for the entire fleet and individual vessels
Exchange of information between the head office, control panel, ships
Carrying out remote monitoring of equipment and ship automation systems, providing real-time consultations, receiving and transmitting information
Providing backup communications for main radio navigation systems
Maintaining a high professional level of ship crews
Ensuring the safety of navigation in all areas of the World Ocean
Promotion technical level electrical power systems and electrical equipment of ships and floating structures
Introduction of modern technologies into the practice of oceanographic and hydrometeorological research
Detection and prevention of acts of maritime piracy
Ensuring the personal needs of passengers and ship crews for constant, affordable, high-speed and high-quality communications.

Benefits of a Marine VSAT solution

Constant monitoring of vessels
High network reliability
Cost optimization
Possibility of working with guaranteed communication speed
Easy to install and maintain equipment
Equipment taking into account sea conditions: ensuring the stability of the terminal in the direction of the satellite in waves up to 5 points
Possibility of constant crew contact with the ground
Ensuring high-quality communication in emergency situations

VSAT based services

Telephony
Internet access
Video conferencing
Unified information network
Monitoring and transmission of telemetry data
Monitoring the location of the vessel, transmitting operational data on the route
Service for clients of passenger shipping companies: paid Internet access, cabin equipment

Typical service organization diagram

Shymkent kalasyndagy AK "Khimpharm" plant kurylymyna taldau.

Shymkent(previously Shymkent, Kaz. Shymkent) is the regional center of the South Kazakhstan region, one of the three largest cities in Kazakhstan and is one of the largest industrial and commercial centers in the country. Shymkent kalasynyn ozіnde halyk sany 700 myn, al zhalpy Ontustik Kazakhstan obaldy boyynsha 2.5-3 million halyk bar.

JSC "Khimpharm" is high-quality medicines, the largest volume of production, sales and a wide range of products in Central Asia, unique licenses, latest generation equipment, many years of experience in the production of medicines.

The Shymkent Chemical and Pharmaceutical Plant, one of the oldest pharmaceutical enterprises in the world, was founded in 1882 by merchants Ivanov and Savinkov. Starting with the release of santonin. With the advent of Soviet power, the plant became the main pharmaceutical enterprise of the country and received the name “Chemical-Pharmaceutical Plant No. 1 named after. F.E. Dzerzhinsky". For a long time, the plant specialized exclusively in the production of pharmaceutical substances. Raw materials for future medicines were supplied to enterprises in Russia, Belarus, Ukraine, the Baltic republics and non-CIS countries, where finished drugs were produced. Therefore, plant No. 1 itself named after. F.E. Dzerzhinsky, was practically unknown to ordinary consumers, despite its more than century-old history. After Kazakhstan gained independence, the need arose to develop its own pharmaceutical industry in the country. This was especially true for the production of finished dosage forms. Therefore, the company’s management developed and confidently implemented a program to create a large modern production facility for the production of finished medicines on the basis of Khimpharm JSC (as the plant was renamed in 1993). Cooperation with foreign partners made it possible to quickly master the most modern equipment. A scientific approach to management, an emphasis on professionalism and high technology - all this allowed the plant to quickly go from the production of primary substances to the creation of a modern pharmaceutical enterprise for the production of finished medicines that meet international standards under the new SANTO brand. Currently, the plant continues to develop and expand the list of medicines produced with modern drugs.

Bugingi kuni "Khimpharm" plant 1000 nan asa adamdar zhumys istidi.

Location of the financial consultant:

JSC "VISOR Capital" (VISOR Capital), 050059, Almaty, Al-Farabi Ave., 5, Business Center

“Nurly Tau”, Building 2a, 10th floor.

Branches and representative offices

“Representative office of the joint stock company “Khimpharm” in the Republic of Uzbekistan.”

Location and postal address of the representative office: Uzbekistan, Tashkent, Yaksarai

district, st. Glinka, house 35

Workshop No. 1 Production from raw opium (morphine, codeine, stipticin...

Workshop No. 3 Production from plant raw materials (celanidi, etc.).

Fourth workshop. Production of ephidrine, in the USSR - anobazina, etc.

Fifth workshop. Production of nicotinic acid.

APPLICATION OF SATELLITE STATIONS IN CORPORATE COMMUNICATION SYSTEMS

Satellite communications have the most important advantages necessary for building large-scale telecommunications networks. Firstly, with its help you can quickly create a network infrastructure that covers a large area and does not depend on the presence or condition of terrestrial communication channels. Secondly, the use of modern technologies for accessing the resource of satellite repeaters and the ability to deliver information to an almost unlimited number of consumers simultaneously significantly reduce the cost of operating the network. These advantages of satellite communications make it very attractive and highly effective even in regions with well-developed terrestrial telecommunications. Moreover, at present, many companies with a geographically distributed structure are extremely interested in reducing the costs of paying for communication services and are increasingly abandoning public network services, preferring to create their own more cost-effective satellite communication networks. The modern market for satellite communication services and systems is replete with a wide range of technological solutions for building such networks, and choosing the satellite technology suitable for a particular enterprise becomes a very difficult task.

Satellite communication systems, depending on the services provided, can be divided into the following classes.

Packet data transmission systems are designed for digital transmission of any data (telex, fax, computer). The speed of packet data transmission in space communication systems ranges from units to hundreds of kilobytes per second. These systems do not have strict requirements for the speed of message delivery. For example, in the “email” mode, the received information is remembered on-board computer and is delivered to the correspondent at a certain time of the day.

Voice (radiotelephone) satellite communication systems use digital message transmission in accordance with international standards: the signal delay along the propagation path should not exceed 0.3 s, subscriber service should be continuous and occur in real time, and negotiations during a communication session should not interrupt.

Systems for determining the location (coordinates) of consumers, such as vehicles, aircraft and sea vehicles. In the foreseeable future, satellite communication systems should complement cellular communication systems where the latter are impossible or insufficiently effective in transmitting information, for example: in marine areas, in areas with low population density, as well as in places where there are breaks in the terrestrial telecommunications infrastructure.

Main characteristics of satellite communication systems

The characteristics of satellite communication systems largely depend on the parameters of the satellite's orbit. A satellite's orbit is the trajectory of the satellite's movement in space.

The diagram of the relative position of the Earth and the satellite is shown in the figure

The earth station is located at point A. If point A is on the tangent AB to the circle, then for the ground station the satellite is visible on the horizon. The elevation angle of the satellite in this case is zero, and the service area of such a satellite reaches its maximum value. However, at zero elevation angles, there may be trees, buildings, uneven terrain, etc. between the antennas of ground and space stations, limiting the line of sight. In addition, as the elevation angle decreases, the signals become more attenuated as they travel longer distances in the atmosphere. Therefore, the actual service area is determined by the minimum permissible satellite elevation angle, usually not less than 5°.

An essential feature of satellite communications is the propagation delay of signals caused by the passage of fairly large distances. This delay varies from a minimum value when the satellite is at the zenith to a maximum value when the satellite is at the horizon. For the triangle ABO shown in Figure 8.8, the following relation is valid:

sin(∠ OAB)/OB=sin(∠ AOB)/AB

Considering that the angle ∠ OAB=∠ AOD+∠ DAB, and the angle ∠ OAB=π/2(AD - tangent to the circle at point A) and, designating the segments: AB - distance from the satellite to the earth station (|AB| = d), BC - minimum distance from the satellite to the earth's surface (|BC| = h, |OB| = R+h), after simple transformations we get:

cos(∠ DAB)/(R+h)=sin(∠ AOB)/d

From expression (8.8) it is easy to express the distance from the satellite to any ground station d in terms of the orbital height h, the elevation angle ∠DAB and the coverage angle of the earth's surface ∠AOD. The angle of coverage of the earth's surface ∠AOD is understood as the solid angle within which part of the surface with ground-based satellite communication stations is visible from the center of the Earth. At minimum elevation angle ∠ AOD=Θ time t3 delay of signal propagation to the satellite and back varies within:

Coefficient 2 reflects the signal propagation delay on the upstream and downstream sections of the path.

A geostationary satellite is located at a high altitude, from which more than a quarter of the surface of the globe is visible. This is one of the advantages of the geostationary orbit. Since a geostationary satellite appears stationary to an observer on earth, pointing the antennas of ground stations is simplified (no need to track the position of the satellite in orbit). But the high orbital altitude also has disadvantages: the signal propagation delay is about 1/4 of a second, and the signal receives significant attenuation on such long paths. In addition, in northern latitudes the satellite is visible at small angles to the horizon, but in the subpolar regions it is not visible at all. There are several hundred satellites in geostationary orbit, serving different regions of the Earth, including the domestic satellites “Horizon” and “Ekran”.

To service territories in northern latitudes, satellites are used in a high elliptical orbit with a large inclination angle. In particular, domestic Molniya satellites have an elliptical orbit with an apogee height over the northern hemisphere of about 40 thousand kilometers and a perigee height of about 500 kilometers. The inclination of the orbital plane to the plane of the earth's equator is 63° and the orbital period is 12 hours. The satellite's movement in the apogee region slows down, and radio communication sessions are possible for 6...8 hours. This type of satellite also makes it possible to serve large areas. But the disadvantage of using them is the need for antenna systems to track slowly drifting satellites and reorient them from the incoming satellite to the ascending one.

Low-orbit satellites are launched into circular orbits with an altitude of about 500...1500 kilometers and a large orbital inclination angle (polar and circumpolar orbits). Light communication satellites are launched using inexpensive launchers. In communication systems with low-altitude satellites, signal propagation delay times are small, but the coverage area is significantly reduced. The speed of the satellite's movement relative to the Earth's surface is quite high, and the duration of the communication session from satellite sunrise to sunset does not exceed tens of minutes. Therefore, to ensure communications over large areas, dozens of satellites must simultaneously be located in low-altitude orbits.

Satellite communication systems (SCS) typically support radio traffic between multiple earth stations. Earth stations are connected to sources and consumers of television and radio broadcasting programs, to switching nodes of communication networks, for example, long-distance telephone exchanges. For example, consider the option of duplex communication between two earth stations. The block diagram of such a SSS is shown in Figure 8.9.

The signal U1, intended for transmission in the communication system, arrives at the transmitter Пд1 of the first earth station. In the transmitter Pd1, the necessary transformations of the carrier wave with frequency f1 are carried out (modulation, amplification, etc.) and the radio signal generated by the transmitter through the separation filter RF1 enters the antenna of earth station 1, which emits it towards the relay satellite. Signal U2, arriving for transmission in the communication system to the second earth station, undergoes similar transformations in similar nodes and is emitted towards the space station with a frequency equal to f2.

Radio signals with frequencies f1 and f2, induced in the space station antenna, are sent through the separation filter RF0 to signal receivers Pm01 and Pm02. The received signals receive the necessary processing in these receivers (frequency conversion, amplification, some communication systems provide signal demodulation or other transformations provided by the signal processing algorithm). Then, in transmitters Pd01 and Pd02, the signals are transferred to the frequencies of downstream channel signals and amplified to the required level. As a result of these transformations, a signal with frequency f1 at the output of the chain consisting of receiver Pm01 and transmitter Pd01 is converted into a signal with frequency f3, and a signal with frequency f3 at the output of chain Pm02 - Pd02 is converted into a signal with frequency f4. Through the RF0 separation filter, these signals arrive at the space station antenna and are radiated towards earth stations.

On Earth, signals with frequencies f3 and f4 reach the antennas of earth stations and enter the inputs of the corresponding receivers. Receiver PM2 is tuned to frequency f3; accordingly, the signal U1 supplied to the input of the communication system from earth station 1 will be restored at the output of the receiver. In turn, the signal U2 transmitted by earth station 2 will be restored at the output of receiver PM1.

For satellite communication systems, frequency bands are allocated separately for uplink and downlink channels in the frequency range from 0.6...86 GHz.

To build satellite communication systems, mainly three types of orbits are used: geostationary orbit, high elliptical orbit and low-altitude orbit. Approximate diagrams of these orbits are shown in the figure.

The area of the earth's surface on which satellite ground stations can be located is called the service area. The characteristics of the communication system are determined by the position of the satellite in orbit. One of the important parameters of satellite communications is the elevation angle of the satellite for an earthly observer - this is the angle between the direction to the satellite and the tangent to the circle at the location of the earth station.

Topology

First of all, you need to clearly formulate the telecommunications needs of your enterprise, because the efficiency of the future network largely depends on the correctly drawn up technical specifications. It is necessary to determine the network topology and the connection diagram between its nodes, which most often are branches of the enterprise. It should be taken into account that communication via a geostationary satellite introduces a noticeable delay in signal propagation; therefore, in some cases it is extremely undesirable to use “double hops” of the signal, doubling this delay. Additionally, redundant connections often add complexity and cost to the network.

In networks with a single information processing center, the services of which are used by many remote branches that weakly interact with each other, a star topology is used. In such a network, communication between branches is carried out through a central node. In cases where the exchange of information between individual branches occurs particularly intensively, it is advisable to implement a mixed network topology, where these branches will be directly connected. This topology can often be found in banking networks and in factories with centralized management and a wide network of regional branches, distributors or product suppliers. In these networks, regional subnetworks with their own specific technological features are often formed. In networks where communication between all branches must be carried out with minimal delay time during signal transmission, a fully connected topology should be implemented. In this case, each network node will be able to establish a direct connection with any other network node. This topology is used in corporate networks with large and multidirectional telephone traffic, as well as in data transmission systems with random connections between their nodes and strict requirements for time delays. The advantages of this topology are undeniable, however, its use is not economically justified in all cases. For each required telecommunications service (telephone, fax or data), it is very important to determine the optimal topology and technology of the satellite communication network and try to implement an integrated communication system that supports them

Formulation of the problem

In this thesis project, we are considering the possibility of using satellite technologies such as SkyEdge for Khimpharm JSC. And also for Kazakh and other foreign companies that have their enterprises in the territory of the Republic of Kazakhstan. The company's head office is located in Shymkent.

As you know, Kazakhtelecom has not yet completed the modernization of the existing telecommunications network. Despite the great achievements in this direction, it will take 5-15 years to completely modernize the entire network in the country. Rural communications in the republic will require especially large expenses. And as you know, in such areas it is very difficult to reach not only the capital, but the nearest village. For prompt communication with the head office and branches, we recommend the use of the VSAT satellite system. The financial condition of the companies is consistently stable; in addition, partners, large national companies, are interested in increasing sales of their products. In connection with the above, we consider it possible for the airline and a group of domestic companies to create their own satellite communication system.

Kazakhtelecom offers all domestic and foreign national companies services in creating their own corporate satellite communication systems to serve their enterprises, both in the Republic of Kazakhstan and abroad.

Technical solution

Satellite communications systems (SCS) are widely used in many regions of the world and have become an integral part of the telecommunications infrastructure of most countries. New satellite applications enable the rapid creation of new broadcast services and private networks.

Although commercial use of geostationary communications satellites began almost 25 years ago, their widespread use in communications networks only became possible in the early 1980s. Television, telephony, and broadband data transmission continue to dominate the list of satellite communications system services. Modern satellite communication systems provide unprecedented opportunities for the development of private networks, the organization of point-to-point and point-to-multipoint communication services:

A satellite is a communication device that receives signals from an earth station (ES), amplifies and transmits in broadcast mode simultaneously to all ES located in the satellite’s visibility range. The satellite does not initiate or terminate any user information with the exception of control and correction signals that arise technical problems and its positioning signals. A satellite transmission starts at a certain station, passes through the satellite, and ends at one or more station.

Advantages and limitations of SSS.

SSS have unique features that distinguish them from other communication systems. Several features provide advantages that make satellite communications attractive for a number of applications. Others create restrictions that are unacceptable when implementing some application tasks. SSS has a number of advantages:

Sustainable costs. The cost of transmission via satellite over one connection does not depend on the distance between the transmitting and receiving stations. Moreover, all satellite signals are broadband. The cost of satellite transmission therefore remains the same regardless of the number of receiving stations.

Wide bandwidth;

Low probability of error. Due to the fact that bit errors are very random in digital satellite transmission, efficient and reliable statistical schemes are used to detect and correct them.

We also highlight a number of limitations in the use of SSS:

Significant delay. The large distance from the ES to the satellite in geostationary orbit leads to a propagation delay of almost a quarter of a second. This delay is quite noticeable during a telephone connection and makes the use of satellite channels extremely ineffective when data transmission is not adapted for CCC;

Dimensions of the ZS. The extremely weak satellite signal reaching the station at some frequencies (especially for satellites of older generations) forces the diameter of the station antenna to be increased, thereby complicating the station placement procedure;

Protection against unauthorized access to information. Broadcasting allows any station tuned to the appropriate frequency to receive information broadcast by satellite. Only signal encryption, often quite complex, ensures information protection from unauthorized access;

Interference. Satellite signals operating in the Ku-band frequencies are extremely sensitive to bad weather. Satellite networks operating in the C-band frequencies are susceptible to microwave signals. Interference due to bad weather degrades Ku-band transmission efficiency for periods ranging from a few minutes to several hours. Interference in the C-band frequencies limits the deployment of ES in residential areas with a high concentration of residents.

The decision to use SNS rather than distributed terrestrial networks must always be economically justified.

Space segment

Modern communications satellites used in commercial satellite systems occupy geostationary orbits, in which the orbital period is equal to the period of the mark on the Earth's surface. This becomes possible when the satellite is placed above a given location on the Earth at a distance of 35,800 km in the equatorial plane.

The high altitude required to maintain a satellite's geostationary orbit explains the insensitivity of satellite networks to distance. The length of the path from a given point on Earth through a satellite in such an orbit to another point on Earth is four times more distance along the surface between its two most distant points.

The main components of a satellite are its structural elements; position control systems, power supply, telemetry, tracking, commands, transceivers and antenna.

The structure of the satellite ensures the functioning of all its components. Left to its own devices, the satellite would eventually spin randomly, rendering it useless for communications. The stability and desired orientation of the antenna is maintained by a stabilization system. The size and weight of the satellite are limited primarily by vehicle capabilities, solar panel requirements, and the amount of fuel to sustain the satellite (usually for ten years).

The satellite's telemetry equipment is used to transmit information about its position to the ground. If position correction is necessary, the corresponding commands are transmitted to the satellite, upon receipt of which the power equipment is turned on and the correction is carried out.

Signal part

The bandwidth of a satellite channel characterizes the amount of information it can transmit per unit of time. A typical satellite transceiver has a bandwidth of 36 MHz at frequencies between 11 GHz and 14 GHz.

Frequency spectrum

Communication satellites must convert the frequency of signals received from the earth station before relaying them to the earth station, therefore the frequency spectrum of a communication satellite is expressed in pairs. Of the two frequencies in each pair, the lower one is used for transmission from the satellite to the ES (downstreams), the upper one is used for transmission from the ES to the satellite (upstreams). Each pair of frequencies is called a band.

Modern satellite channels most often use one of two bands: Ku-band (from satellite to satellite in the 14 GHz region and back in the 12 GHz region). Each frequency band has its own characteristics aimed at different communication tasks.

Ku-band transmission: Ku-band transmission has a strong, narrow beam, making transmission ideal for point-to-point or point-to-multipoint connections. Terrestrial microwave signals do not interfere with Ku-band signals in any way, and Ku-band terrestrial stations can be located in city centers. The natural high power of Ku-band signals makes it possible to get by with smaller, cheaper terrestrial antennas. Unfortunately, Ku-band signals are extremely sensitive to atmospheric conditions, especially fog and heavy rain. Although such weather events are known to affect a small area for a short time, the results can be quite severe if such conditions coincide with the BHH (busy hour, eg 4 pm, Friday afternoon).

Ground segment

Technological development has led to a significant reduction in the size of the ES. At the initial stage, the satellite did not exceed several hundred kilograms, and the satellites were giant structures with antennas more than 30 meters in diameter. Modern satellites weigh several tons, and antennas often do not exceed 1 meter in diameter and can be installed in a wide variety of places; the trend of reducing the size of the satellite, together with simplifying the installation of equipment, leads to a reduction in its cost. Today, the cost of ES is perhaps the main characteristic that determines the widespread use of SSS. The advantage of satellite communications is based on serving geographically distant users without the additional costs of intermediate storage and switching. Any factors that reduce the cost of installing a new AP will definitely contribute to the development of applications focused on the use of SSS. The relatively high costs of deploying terrestrial networks allow terrestrial fiber-optic networks to successfully compete with SSNs in some cases.

Consequently, the main advantage of satellite systems is the ability to create communication networks that provide new communication services or expand existing ones, while from an economic point of view, the advantage of satellite systems is inversely proportional to the cost of the satellite.

Depending on the type, the station has transmission and/or reception capabilities. As already noted, virtually all intelligent functions in satellite networks are carried out in the satellite station. Among them are the organization of access to satellite and terrestrial networks, multiplexing, modulation, signal processing and frequency conversion. Note that most problems in satellite transmission are solved by satellite equipment.

Currently, there are four types of ES.

The most complex and expensive are those aimed at high user load intensity, with very high throughput. Stations of this type are designed to serve user populations that require fiber-optic communication lines to ensure normal access to the AP. Such APs cost millions of dollars;

Medium-capacity stations are effective for servicing private corporate networks. The sizes of such ES networks can be very diverse depending on the implemented applications (speech, data, video transmission). There are two types of corporate CCC;

A mature, capital-intensive enterprise network typically supports services such as video conferencing, email, video, voice, and data. All stations of such a network have equally high throughput, and the cost of a station reaches up to $1 million;

A less expensive type of corporate network is a network of a large number (up to several thousand) micro terminals (VSAT-VerySmallApertureTerminal) connected to one main station (MES - MasterEarthStation). These networks are usually limited to receiving/transmitting data and speech in digital form. Micro terminals communicate with each other through transit with processing through the main terminal or bypassing it. The topology of such networks is star-shaped (STAR or MESH);

The AP is limited by its reception capabilities. This is the cheapest station option, since its equipment is optimized to provide one or more specific services. This ES can be oriented towards receiving data, audio signal, video or their combinations. The topology here is star-shaped.

Network components

The network consists of a network control center, a load terminal and remote stations (Figure 1.2).

Network Control Center

The control center (Figure 1.3) controls all access to the satellite system and actually acts as a switchboard for users at remote terminals. The CC control center provides automatic network operation, monitoring and control functions, provides the network operator with reports on capacity utilization, collects load statistics and manages the distribution of satellite resources. The Network Operations Center also performs routing and switching functions, such as destination selection based on an unlimited numbering plan, automatic circuit routing changes, and switching protocol conversions. The network control center can be located anywhere in the network and should not be tied to any other component, including load stations.

Network Control Center contains:

Standard RF equipment, antenna and RF transceiver for communication with the satellite.

Network management equipment. Network management equipment (Figure 1.3) consists of:

Control channel modules, which provide satellite communications between network management equipment and remote stations via control channels.

DAMA workstation and call processing, which contains all real-time control software. Network management stations, which are used to view network status, change network configuration, and store call data records.

Figure 1.2 – VSAT network components

Figure 1.3 – Network Control Center

Load terminal

A load terminal is a station at which traffic directed to a node is concentrated. This terminal can be located either near the Network Control Center or anywhere else in the network. There may be several load terminals in the network, for example, to concentrate traffic directed to regional centers.

Remote station

The main function of the remote station equipment (Figure 3) is to connect the satellite circuits to the ground equipment. To perform these functions, the remote station equipment provides line and signaling interfaces, as well as interfaces to subscriber equipment; There is constant communication with network management equipment to distribute satellite circuits, monitor events and manage station resources.

The remote station contains:

RF equipment: antenna and RF transceiver (transceiver) used to communicate with the satellite.

Channel-forming equipment, which consists of:

a satellite modem responsible for the physical layer of communication via satellite between the remote station and the network control center;

one or more user interface modules that are responsible for the physical connection to a group of user interfaces, as well as signaling detection and voice signal processing functions. These user interface modules can be either voice or data;

remote station controller, which is the station's main processor and routing device for all intra-station communications and message flow between the remote station and the NCC.

Figure 1.4 – Remote station

SkyEdge technology son of negіzi

SkyEdge- satellite communication technology VSAT from company GilatNetworkSystems, designed to create multiservice communication networks. Developed in 2005. Networks based on SkyEdge technology provide speeds of up to 100 Mbit/s, satellite Internet, email, telephony, video conferencing, database synchronization, high degree of protection of transmitted data. The SkyEdge technology platform provides advanced circuitry and architectural solutions that can be used to create networks of any arbitrary topology.

The new SkyEdge satellite communications platform is the first of its kind - a cohesive system that supports multiple VSATs on a single HUB with many advanced features such as built-in virtual private network (VPN), built-in acceleration technologies, and VoIP support over a mesh network. The SkyEdge family of products delivers premium switched voice and data services on a single, flexible, reliable and easy-to-manage platform. SkyEdge represents a true breakthrough in satellite network technology that has the potential to revitalize service offerings and revenue streams for network operators and service providers.

Network overview

The SkyEdge system is a unique platform for data and voice transmission.

Improved architecture

Topologies support: star, multi-star, mesh

Supports simultaneous work with several satellites on one HUB.

Data services - IP, legacy, meshIPtrunking

Several Outbound carriers of the DVB-S standard - up to 66 Mbit/s per carrier

Optional support for small networks, from 340 Kbps

Carrier Inbound - from 60 Kbps to 2 Mbps.

Various schemes for accessing satellite resources.

The Figure shows a network diagram.

SkyEdge Technology(Gilat Network Systems) - VSAT satellite communication technology from Gilat Network Systems, designed to create multi-service communication networks. Developed in 2005. Networks based on SkyEdge technology allow you to provide speeds of up to 100 Mbit/s, Satellite Internet, email, telephony, video conferencing, database synchronization, and a high degree of protection of transmitted data. The SkyEdge technology platform provides advanced circuitry and architectural solutions that can be used to create networks of any arbitrary topology.

A large selection of network interfaces in the SkyEdge platform allows you to design and build universal multiservice networks of the latest generation. SkyEdge makes it easy to integrate VSAT into existing networks built on Cisco technologies and equipment by installing the Cisco VSAT NM module directly into existing routers.

The SkyEdge technology platform has built-in solutions to support GSM and CDMA2000 technologies, which are 80% more efficient in using the satellite segment compared to SCPC and other channels. The solutions connect cells to the network in a transparent and efficient manner while maintaining high quality voice and data services.

SkyEdge technology supports a variety of different IP applications, implementing different topologies of central terminal-to-remote terminal and remote terminal-to-remote terminal connections.

Features of SkyEdge technology:

high performance (high quality data transfer speed);

scalability;

various connection topologies (star, mesh and multi-star);

built-in acceleration of TCP and HTTP traffic;

QoS support;

support for any multicast IP broadcasting and data transmission applications (Internet, VoIP, IP multicast, video conferencing);

quick installation and installation;

low cost of maintenance and operation.

The SkyEdge system was developed and manufactured by the world leader in the VSAT technology industry - GilatSateliteNetworks Ltd (Israel). SkyEdge is the ideal technology for:

organizing access to the Internet or local network based on modern web technologies;

building private and dedicated networks (the head office can even be connected to tens of thousands of geographically remote branches);

remote work with high-speed IP applications.

There are an infinite number of ways to connect computers.

Network topology is the geometric shape and physical arrangement of computers in relation to each other. Network topology allows you to compare and classify different networks. There are three main types of topology:

1) Star;

2) Ring;

BUS TOPOLOGY

When building a network using a bus scheme, each computer is connected to a common cable, at the ends of which terminators are installed.

The signal passes through the network through all computers, reflecting from the end terminators.

Fig. 1 - Bus topology.

The bus carries a signal from one end of the network to the other, and each workstation checks the address of the message, and if it matches the address of the workstation, it accepts it. If the address does not match, the signal goes further along the line. If one of the connected machines does not work, this does not affect the operation of the network as a whole, however, if the connections of any of the connected machines are disrupted due to a damaged contact in the connector or a broken cable, a faulty terminator, then the entire network segment (the section of cable between two terminators ) loses integrity, which leads to disruption of the entire network.

RING TOPOLOGY

This topology is serial connection computers when the latter is connected to the former. The signal travels along the ring from computer to computer in one direction. Each computer acts as a repeater, amplifying the signal and transmitting it further. Since the signal passes through each computer, the failure of one of them leads to disruption of the entire network.

Fig.2 - “Ring” topology.

STAR TOPOLOGY

Star topology is a connection scheme in which each computer is connected to the network using a separate connecting cable. One end of the cable is connected to the network adapter socket, the other is connected to central device, called a hub.

Fig.3 - Star topology.

Installing a Star topology network is easy and inexpensive. The number of nodes that can be connected to a hub is determined by the number of ports available on the hub itself, but there is a limit on the number of nodes (maximum 1024). A working group created according to this scheme can function independently or can be associated with other working groups.

NETWORK HARDWARE.

Network equipment - devices necessary for the operation of a computer network, for example: router, switch, hub, patch panel, etc. Active and passive network equipment can be distinguished.

1.Router- a specialized network computer that has two or more network interfaces and forwards data packets between different network segments. A router can connect heterogeneous networks of different architectures. To make decisions about packet forwarding, information about the network topology and certain rules set by the administrator are used.

Principle of operation.

Typically, a router uses the destination address specified in the packet header and determines from the routing table the path along which the data should be sent. If there is no described route in the routing table for an address, the packet is discarded.

There are other ways to determine the forwarding route of packets using, for example, the source address, the upper layer protocols used, and other information contained in the packet headers network layer. Often, routers can translate the addresses of the sender and recipient, filter the transit data stream based on certain rules to limit access, encrypt/decrypt transmitted data, etc.

Application.

Routers help reduce network congestion by dividing the network into collision domains or broadcast domains, and by filtering packets. They are mainly used to combine networks of different types, often incompatible in architecture and protocols, for example, to combine local Ethernet networks and WAN connections using xDSL, PPP, ATM, Frame relay, etc. protocols. A router is often used to provide access from local network to the global Internet, performing the functions of address translation and firewall.

A router can be either a specialized (hardware) device or a regular computer that performs the functions of a router. There are several software packages (Linux kernel-based, BSD-based operating systems) that can turn a PC into a high-performance and feature-rich router, such as Quagga, IPFW or easy-to-use PF

Devices for home and small office.

IN household sector typically low-port routers/routers are used to provide connectivity home network computers to the communication channel of the Internet provider. As a rule, the router provides IP addressing of local network devices via DHCP protocol, and itself receives an IP address from an external provider. Typically a modern router has a number of auxiliary functions and built-in features: a Wi-Fi access point for connecting mobile devices, a firewall to protect the network from external attacks, Internet backup from several providers, a web interface to simplify device setup, a USB port for connecting a printer or disk storage, and others. Household routers have different network bandwidths; simple, cheap models can limit the Internet connection speed on high-speed tariffs.

2.Network switch- a device designed to connect several nodes of a computer network within one or more network segments. The switch operates at the data link (second) layer of the OSI model. Switches have been designed using bridge technologies and are often thought of as multiport bridges. Routers (OSI layer 3) are used to connect multiple networks based on the network layer.

Unlike a hub (OSI layer 1), which distributes traffic from one connected device to all others, a switch transmits data only directly to the recipient (the exception is broadcast traffic to all network nodes and traffic for devices for which the outgoing switch port is unknown). This improves network performance and security by freeing other network segments from having to (and being able to) process data that was not intended for them.

					Sheet

Change	Sheet	Document no.	Signature	date

The principle of operation of the switch.

The switch stores in memory (the so-called associative memory) a switching table, which indicates the correspondence of the host MAC address to the switch port. When the switch is turned on, this table is empty and it operates in learning mode. In this mode, data arriving on any port is transmitted to all other ports of the switch. In this case, the switch analyzes the frames (frames) and, having determined the MAC address of the sending host, enters it into the table for some time. Subsequently, if one of the switch ports receives a frame intended for a host whose MAC address is already in the table, then this frame will be transmitted only through the port specified in the table. If the destination host's MAC address is not associated with any port on the switch, then the frame will be sent to all ports except the port from which it was received. Over time, the switch builds a table for all active MAC addresses, resulting in localized traffic. It is worth noting the low latency (delay) and high forwarding speed on each interface port.

Switching modes.

There are three switching methods. Each of them is a combination of parameters such as latency and transmission reliability.

With intermediate storage (Store and Forward). The switch reads all the information in the frame, checks it for errors, selects a switch port, and then sends the frame to it.

Cut-through. The switch reads only the destination address in the frame and then performs the switching. This mode reduces transmission delays, but does not have an error detection method.

Fragment-free or hybrid. This mode is a modification of the pass-through mode. The transmission is carried out after filtering collision fragments (the first 64 bytes of the frame are analyzed for the presence of an error, and if there is no error, the frame is processed in end-to-end mode).

The "switch decision" latency is added to the time it takes a frame to enter and exit a switch port and together determines the overall switch latency.

Symmetrical and asymmetrical switching.

The symmetry property of switching allows you to characterize a switch in terms of bandwidth for each of its ports. A symmetric switch provides switched connections between ports with the same bandwidth, for example when all ports have a bandwidth of 10 Mbps or 100 Mbps.

Memory buffer.

For temporary storage of frames and their subsequent sending via to the right address The switch may use buffering. Buffering can also be used when the destination port is busy. A buffer is a memory area in which the switch stores transmitted data.

The memory buffer can use two methods for storing and sending frames: port buffering and shared memory buffering. With port buffering, packets are stored in queues that are associated with individual input ports. A packet is transmitted to the output port only when all frames ahead of it in the queue have been successfully transmitted. In this case, it is possible that one frame delays the entire queue due to the busy port of its destination. This delay may occur even though other frames may be forwarded to open ports at their destinations.

Shared memory buffering stores all frames in a shared memory buffer that is shared by all ports on the switch. The amount of memory allocated to a port is determined by the amount it requires. This method is called dynamic buffer memory allocation. After this, the frames that were in the buffer are dynamically distributed to the output ports. This allows you to receive a frame on one port and send it on another port without having to queue it.

The switch maintains a map of ports to which frames need to be sent. This map is cleared only after the frame has been successfully sent.

Because the buffer memory is shared, the frame size is limited to the entire buffer size rather than the portion allocated to a specific port. This means that large frames can be transmitted with less loss, which is especially important in asymmetric switching, that is, when a port with a bandwidth of 100 Mb/s must send packets to a port of 10 Mb/s.

3.Network adapter- an additional device that allows the computer to interact with other network devices. Currently, in personal computers and laptops, the controller and components that perform the functions of a network card are quite often integrated into motherboards for convenience, including unifying the driver and reducing the cost of the entire computer as a whole.

Types

Based on their design, network cards are divided into:

internal - separate cards inserted into an ISA, PCI or PCI-E slot;

external, connected via LPT, USB or PCMCIA interface, mainly used in laptops;

built into the motherboard.

On 10-megabit network cards To connect to the local network, 4 types of connectors are used:

8P8C for twisted pair;

BNC connector for thin coaxial cable;

15-pin transceiver AUI connector for thick coaxial cable.

optical connector (en:10BASE-FL and other 10 Mbit Ethernet standards)

These connectors can be present in different combinations, but only one of them is working at any given time.

100 Mbit boards have either a twisted pair connector (8P8C, erroneously called RJ-45) or an optical connector (SC, ST, MIC).

One or more information LEDs are installed next to the twisted pair connector, indicating the presence of a connection and the transfer of information.

One of the first mass-produced network cards was the NE1000/NE2000 series from Novell with a BNC connector.

Network adapter settings.

When configuring a network adapter card, the following options may be available:

request line number hardware interrupt IRQ

DMA channel number (if supported)

base I/O address

RAM memory base address (if used)

support for auto-negotiation duplex/half-duplex standards, speed

support for tagged VLAN packets (802.1q) with the ability to filter packets of a given VLAN ID

WOL (Wake-on-LAN) parameters

Auto-MDI/MDI-X function automatic selection of operating mode for straight or cross-crimped twisted pair

Link Layer MTU

Depending on the power and complexity of the network card, it can implement computing functions (mainly counting and generating frame checksums) either in hardware or software (by a network card driver using a central processor).

Functions and characteristics of network adapters .

The network adapter (Network Interface Card (or Controller), NIC) together with its driver implements the second, data link layer of the open systems model (OSI) in the final network node - the computer. More precisely, in a network operating system, the adapter and driver pair performs only the functions of the physical and MAC layers, while the LLC layer is usually implemented by an operating system module that is common to all drivers and network adapters. Actually, this is how it should be in accordance with the IEEE 802 protocol stack model. For example, in Windows NT, the LLC level is implemented in the NDIS module, common to all network adapter drivers, regardless of what technology the driver supports.

The network adapter together with the driver performs two operations: frame transmission and reception. Transmitting a frame from a computer to a cable consists of the following steps (some may be missing, depending on the encoding methods adopted):

Reception of LLC data frame through the cross-layer interface along with MAC layer addressing information. Typically, communication between protocols within a computer occurs through buffers located in random access memory. Data for transmission to the network is placed in these buffers by upper-layer protocols, which retrieve them from disk memory or from the file cache using the operating system's I/O subsystem.

Formatting a MAC layer data frame into which the LLC frame is encapsulated (with the 01111110 flags discarded). Filling destination and source addresses, calculating checksum.

Formation of code symbols when using redundant codes of type 4B/5B. Scrambling codes to obtain a more uniform spectrum of signals. This stage is not used in all protocols - for example, 10 Mbit/s Ethernet technology does without it.

Output of signals into the cable in accordance with the accepted linear code - Manchester, NRZI, MLT-3, etc.

Receiving a frame from a cable to a computer includes the following actions:

Receiving signals from the cable that encode the bit stream.

Isolating signals from noise. This operation can be performed by various specialized chips or DSP signal processors. As a result, a certain bit sequence is formed in the adapter receiver, which with a high degree of probability coincides with the one sent by the transmitter.

If the data was scrambled before being sent to the cable, it is passed through a descrambler, after which the code symbols sent by the transmitter are restored in the adapter.

Checking the frame checksum. If it is incorrect, the frame is discarded, and the corresponding error code is sent to the LLC protocol through the inter-layer interface to the top. If the checksum is correct, then an LLC frame is extracted from the MAC frame and transmitted through the cross-layer interface upward to the LLC protocol. The LLC frame is placed in a RAM buffer.

The distribution of responsibilities between a network adapter and its driver is not defined by standards, so each manufacturer decides this issue independently. Typically, network adapters are divided into adapters for client computers and adapters for servers.

In adapters for client computers, a significant part of the work is shifted to the driver, making the adapter simpler and cheaper. The disadvantage of this approach is high degree loading the computer's central processor with routine work on transferring frames from the computer's RAM to the network. The central processor is forced to do this work instead of performing the user's application tasks.

Therefore, adapters designed for servers are usually equipped with their own processors, which independently perform most of the work of transferring frames from RAM to the network and vice versa. An example of such an adapter would be network adapter SMC EtherPower with integrated Intel i960 processor.

Depending on which protocol the adapter implements, adapters are divided into Ethernet adapters, Token Ring adapters, FDDI adapters, etc. Since the Fast Ethernet protocol allows, through the auto-negotiation procedure, to automatically select the operating speed of the network adapter depending on the capabilities hub, then many Ethernet adapters Today they support two operating speeds and have the prefix 10/100 in their name. Some manufacturers call this property autosensitivity.

The network adapter must be configured before installation in the computer. When configuring an adapter, you typically specify the IRQ number used by the adapter, the DMA channel number (if the adapter supports DMA mode), and the base address of the I/O ports.

If the network adapter, computer hardware, and operating system support the Plug-and-Play standard, then the adapter and its driver are configured automatically. Otherwise, you must first configure the network adapter and then repeat its configuration settings for the driver. In general, the details of the procedure for configuring a network adapter and its driver largely depend on the adapter manufacturer, as well as on the capabilities of the bus for which the adapter is designed.

If a network adapter is not working correctly, its port may flop.

4.Network hub or hub(from the English hub - center) - a device for connecting computers into an Ethernet network using twisted pair cable infrastructure. Currently being replaced by network switches.

Network hubs could also have connectors for connecting to existing networks based on thick or thin coaxial cable.

Principle of operation.

The hub operates at the first (physical) level of the OSI network model, relaying the incoming signal from one of the ports to a signal on all other (connected) ports, thus implementing the common bus topology characteristic of Ethernet, with the division of network bandwidth between all devices and work in half duplex mode. Collisions (that is, an attempt by two or more devices to start transmitting at the same time) are processed similarly to Ethernet on other media - devices independently stop transmitting and resume the attempt after a random period of time; in modern parlance, a hub unites devices in one collision domain.

A network hub also ensures uninterrupted operation of the network when a device is disconnected from one of the ports or the cable is damaged, unlike, for example, a network on a coaxial cable, which in this case stops working entirely.

When more input blocks arrive than the concentrator can “accumulate,” the concentrator discards some of them.

5. Modem(an acronym made up of the words modulator and demodulator) is a device used in communication systems to physically interface an information signal with its propagation medium, where it cannot exist without adaptation.

The modulator in the modem modulates the carrier signal when transmitting data, that is, changes its characteristics in accordance with changes in the input information signal, the demodulator carries out the reverse process when receiving data from the communication channel. The modem serves as the terminal equipment of the communication line. The very formation of data for transmission and processing of received data is carried out by the so-called. terminal equipment (a personal computer can also play this role).

Modems are widely used to connect computers through a telephone network (telephone modem), cable network (cable modem), radio waves (en:Packet_radio, radio relay communication). Previously, modems were also used in cell phones (until they were superseded digitally data transmission).

Story .

AT&T Dataphone Modems in the United States of America was part of SAGE (air defense systems) in the 1950s. It connected terminals at various air bases, radars, and control centers to SAGE command centers scattered throughout the United States and Canada. SAGE used leased lines, but the devices at each end of those lines were the same in principle as modern modems.

The first modem for personal computers was the Micromodem II device for the Apple II personal computer, released in 1979 by Hayes Microcomputer Products. The modem cost $380 and operated at 110/300 bps.

In 1981, Hayes released the Smartmodem 300 bps modem, whose command system (Hayes commands) became the de facto standard in the industry.

Types of computer modems.

By execution

external - connected via a COM, LPT, USB or Ethernet port, usually have a separate power supply (there are also USB modems powered by the USB bus).

internal - additionally installed inside the system unit or laptop (in the ISA, PCI, PCI-E, PCMCIA, AMR/CNR slot).

built-in - are part of the device where they are built in ( motherboard, laptop or docking station).

According to the operating principle

hardware - all signal conversion operations and support for physical exchange protocols are performed by a computer built into the modem (for example, using a DSP or microcontroller). The hardware modem also contains ROM, which contains the firmware that controls the modem.

modems without ROM - work entirely in hardware, but at the beginning of operation the driver must load the firmware into the modem.

semi-programmatic (modem with a simplified controller, controller based soft-modem) - modems in which part of the functions of the modem is performed by the computer to which the modem is connected. For example, the modem equipment deals with modulation and demodulation, and the driver supports high-level protocols.

software (soft modems, modems without a controller, host based soft-modem) - all operations on signal encoding, error control and protocol management are implemented in software and are performed by the computer’s central processor. The modem contains only input/output analog circuits and converters (DAC and ADC), as well as an interface controller (for example, USB).

By network and connection type

Modems for telephone lines:

ISDN - modems for digital dial-up telephone lines.

DSL - used to organize dedicated (non-switched) lines using a regular telephone network. They differ from dial-up modems in that they use a different frequency range, and also in that the signal is transmitted via telephone lines only to the telephone exchange. Usually they allow the use of a telephone line for negotiations simultaneously with data exchange.

Cable modems - are used to exchange data over specialized cables - for example, through a collective television cable using the DOCSIS protocol.

Radio modems - operate in the radio range, use their own sets of frequencies and protocols:

Wireless modems - operate using cellular protocols (GPRS, EDGE, 3G, LTE) or Wi-Fi. They often come in the form of a USB keychain. Mobile communication terminals are also often used as such modems.

Satellite modems- used to organize satellite Internet. Receive and process the signal received from the satellite.

PowerLine modems (HomePlug standard) - use technology for transmitting data over the wires of a household electrical network.

TYPES OF CABLES.

Twisted pair.

Twisted pair is a type of communication cable. It is one or more pairs of insulated conductors, twisted together (with a small number of turns per unit length), covered with a plastic sheath.

Twisting of conductors is carried out in order to increase the degree of connection between the conductors of one pair (electromagnetic interference equally affects both wires of the pair) and subsequent reduction of electromagnetic interference from external sources, as well as mutual interference when transmitting differential signals.

To reduce the coupling of individual cable pairs (periodic bringing together of conductors of different pairs) in UTP cables of category 5 and higher, the wires of the pairs are twisted with different pitches. Twisted pair is one of the components of modern structured cabling systems. Used in telecommunications and computer networks as a physical signal transmission medium in many technologies such as Ethernet, Arcnet and Token ring. Currently, due to its low cost and ease of installation, it is the most common solution for building wired (cable) local networks.

The cable connects to network devices using an 8P8C connector (mistakenly called RJ45).

Shielding.

To protect against electrical interference when using high-frequency signals, cables of categories 6a-8 use shielding. Shielding is applied both to individual twisted pairs, which are wrapped in aluminum foil (aluminium-metalized polyethylene tape), and to the cable as a whole in the form of an overall shield made of foil and/or braided copper wire. The shield may also be connected to a bare drain wire, which serves as a grounding wire and mechanically supports the shield in the event of sectioning due to excessive bending or stretching of the cable.

According to the international standard ISO/IEC 11801 Annex E, a combination of three letters is used to designate the construction of a shielded cable: U - unshielded, S - metal braid (general shield only), F - metallized tape (aluminum foil). These letters form an abbreviation of the form xx/xTP, indicating the type of general screen and the type of screen for individual pairs.

F/UTP cable

S/FTP cable

The following types of screen construction are common:

Unshielded cable (U/UTP)

Individual screen (U/FTP)

Shielding with foil for each individual pair. Protects against external interference and crosstalk between twisted pairs.

General screen (F/UTP, S/UTP, SF/UTP)

A common screen made of foil, braid, or foil with braid. Protects against external electromagnetic interference.

Individual and shared screen (F/FTP, S/FTP, SF/FTP)

Individual foil shields for each twisted pair, plus a common shield made of foil, braid, or foil with braid. Protects against external interference and crosstalk between twisted pairs.

Category 5e, 6/6A and 8/8.1 shielded cables most often use F/UTP (shared foil shield) construction, while Category 7/7A and 8.2 shielded cables use S/FTP (shared metal braid and foil each) construction. pairs).

Coaxial cable.

Coaxial cable (from the Latin co - together and axis - axis, that is, coaxial; colloquial coax from the English coaxial) is an electrical cable consisting of a coaxially located central conductor and screen, separated by insulating material or an air gap. Used to transmit radio frequency electrical signals. Different from shielded wire used for DC transmission electric current and low-frequency signals, a more uniform cross-section in the direction of the longitudinal axis (the cross-sectional shape, dimensions and values of the electromagnetic parameters of materials are normalized) and the use of higher quality materials for electrical conductors and insulation. Invented and patented in 1880 by British physicist Oliver Heaviside.

Device.

The coaxial cable (see figure) consists of:

4 (A) - shells (served for insulation and protection from external influences) made of light-stabilized (that is, resistant to ultraviolet radiation from the sun) polyethylene, polyvinyl chloride, fluoroplastic tape or other insulating material;

3 (B) - external conductor (screen) in the form of a braid, foil, film coated with a layer of aluminum and their combinations, as well as a corrugated tube, a layer of metal tapes, etc. made of copper, copper or aluminum alloy;

2 (C) - insulation made in the form of solid (polyethylene, foamed polyethylene, solid fluoroplastic, fluoroplastic tape, etc.) or semi-air (cord-tubular layer, washers, etc.)

Due to the coincidence of the axes of both conductors in an ideal coaxial cable, both components of the electromagnetic field are completely concentrated in the space between the conductors (in dielectric insulation) and do not extend beyond the cable, which eliminates the loss of electromagnetic energy through radiation and protects the cable from external electromagnetic interference. In real cables, limited radiation output and sensitivity to interference are caused by geometry deviations from ideality. All useful signal is transmitted through the internal conductor.

Classification.

By purpose - for cable television systems, for communication systems, aviation, space technology, computer networks, household appliances etc.

In terms of characteristic impedance (although the characteristic impedance of the cable can be any), the standard values are five according to Russian standards and three according to international ones:

50 Ohm is the most common type, used in various fields of radio electronics. The reason for choosing this rating was, first of all, the possibility of transmitting radio signals with minimal losses in a cable with a solid polyethylene dielectric, as well as readings of electrical strength and transmitted power close to the maximum achievable

75 Ohm - common type:

in the USSR and Russia it is used mainly with a solid dielectric in television and video equipment. Its widespread use was due to the acceptable ratio of cost and mechanical strength when pulling, since the footage of this cable is significant. In this case, losses are not of decisive importance, since high-power signals are usually not transmitted through such cables.

In the USA it is used for cable television networks - with a foamed dielectric. These cables have a central core made of copper-plated steel, so their cost depends slightly on the diameter of the central core. Therefore, the authors speculate that the reason for choosing this rating in the US was a trade-off between cable loss and cable flexibility.

Also previously important was the matching of such a cable with the characteristic impedance of the most common [source not specified 939 days] type of antenna - a half-wave dipole (73 ohms). But since a coaxial cable is asymmetrical, and a half-wave dipole is symmetrical by definition, a balancing device is required for matching, otherwise the cable braid (feeder) begins to act as an antenna.

100 Ohm - rarely used, in pulse technology and for special purposes;

150 Ohm - rarely used, in pulse technology and for special purposes, not provided for by international standards;

200 Ohm - used extremely rarely, not provided for by international standards;

There are other denominations; In addition, there are coaxial cables with non-standardized [source not specified 1793 days] wave impedance: they are most widespread in analog audio engineering.

By insulation diameter:

subminiature - up to 1 mm;

miniature - 1.5-2.95 mm;

medium-sized - 3.7-11.5 mm;

large-sized - more than 11.5 mm.

By flexibility (resistance to repeated bending and mechanical bending moment of the cable): rigid, semi-rigid, flexible, extra flexible.

According to the degree of shielding:

with full screen

with metal tube screen

with tinned braid screen

with regular screen

with single layer braid

with two- and multi-layer braiding and with additional shielding layers

radiating cables having an intentionally low (and controlled) degree of shielding .

"Thin" Ethernet.

It was the most common cable for building local networks. The diameter of approximately 6 mm and considerable flexibility allowed it to be laid in almost any place. The cables were connected to each other and to the network card in the computer using a BNC T-connector. The cables could be connected to each other using a BNC I connector (direct connection). Terminators must be installed at both ends of the segment. Supports data transfer up to 10 Mbps over a distance of up to 185 m.

"Thick" Ethernet.

The cable was thicker than the previous one - about 12 mm in diameter, and had a thicker central conductor. It did not bend well and had a significant cost. In addition, there were some difficulties when connecting to a computer - AUI (Attachment Unit Interface) transceivers were used, connected to network card using a branch piercing the cable, the so-called. "vampires".

Due to the thicker conductor, data transmission could be carried out over a distance of up to 500 m at a speed of 10 Mbit/s. However, the complexity and high cost of installation did not allow this cable to become as widespread as the RG-58. Historically, the proprietary RG-8 cable was yellow, which is why you sometimes see the name “Yellow Ethernet.”

3. Fiber optic cable.

Fiber optic cable (English: optic fiber cable) is a cable based on optical fibers, designed for transmitting optical signals in communication lines.

The design of the cable is determined by its purpose and location of installation: from the simplest (shell, plastic tubes with fibers) to multilayer (for example, an underwater communication cable) containing reinforcing and protective elements.

A fiber optic cable consists of the following elements:

Supporting cable, rod made of fiberglass or metal coated with a polyethylene sheath. Serves for centering tubes - modules (see below) and imparting rigidity to the cable, clamped under a screw to secure the cable in the coupling/cross.

Double-layer glass or plastic fibers, possibly coated with one or two layers of varnish. The varnish layer protects the fibers from damage and serves to color-code the fibers (transparent or colored).

Plastic tubes containing filaments - light guides and filled with hydrophobic gel. The number of tubes varies from 1 or more, the number of fibers in a tube - from 4 to 12, the total number of fibers in a cable - from 8 to 144 (often 32, 48, 64). To maintain the overall dimensions of the cable with a small number of fibers, black plugs can be inserted instead of tubes.

A film entwining the tubes, tied with threads and moistened with a hydrophobic gel. It has damping properties and is designed to reduce friction inside the cable, provide additional protection from moisture, retain hydrophobic liquid in the space between modules, etc.

A layer of thin inner polyethylene shell designed for additional protection against moisture (may be missing).

A layer of Kevlar threads or armor. Armor - a rectangular rod or round wires made of steel (imported cable), nail iron (domestic cable) or fiberglass (the same as the central power element). Kevlar is lightweight and has a permissible tensile force of 6-9 kN). The purpose of Kevlar is to act as a cable in places where noise interference is unacceptable, for example, along railway tracks (contact wire, voltage up to 27.5 kV); perception of wind load. The purpose of the armor is to protect cables laid in the ground without protection in the form of a plastic pipe, cable duct, etc.

A layer consisting of a polyethylene film and a certain amount of hydrophobic gel (may be absent). Designed for additional protection against moisture.

A layer that is a thick and soft shell of polyethylene. Designed to protect internal layers from environmental influences.

Information about the color of the fibers in the cable, their type and location in the tubes is not standardized and is indicated by each manufacturer in the cable passport.

Satellite communications for technology. Technical Customer Support

Send your good work in the knowledge base is simple. Use the form below

Similar documents

Service maintenance.

Technical Customer Support

Training your staff

Network maintenance

Customer information support

What is VSAT?

How does the VSAT network work?

Network topology

iDirect technology

Communication topologies

Corporate satellite networks

Corporate network using Stratos-MT Central Station

Local corporate network with a center at the Customer’s office

Corporate network using mobile stations

Backup corporate network

Technologies used

TechnologyMCPC (Multichannel Per Carrier)

Using the ND SATCOM platform (SKYWAN®)

Using the platformiDirect

Composition of the service and commercial terms of provision

Dedicated satellite channels

Main characteristics

Satellite Internet access channel

Main characteristics

Satellite communications for the fuel and energy sector

Fixed satellite communications

Mobile satellite communication

Broadband in Action

ServicesBGAN Inmarsat:

Benefits of BGAN Inmarsat

Mobile satellite communication services BGAN Inmarsat

AdvantagesBGAN Inmarsat:

ServicesBGAN Inmarsat:

BGAN coverage areaInmarsat

Composition of Services

Tariff plans for the Inmarsat BGAN system

Package plans for the Inmarsat BGAN system

VSAT based solution for river and sea vessels

Marine VSAT

Services are implemented on the basis of high-speed satellite channels to solve the following problems:

Benefits of a Marine VSAT solution

VSAT based services

Typical service organization diagram

Main characteristics of satellite communication systems

Popular articles

Latest articles

Sections

Pages

Special projects

Contacts