Communication channels: types, characteristics

In order to transmit various information, an environment for its distribution must initially be created, which is a set of lines, or data transmission channels with specialized transceiver equipment. Lines, or communication channels, are the connecting link in any modern data transmission system, and from the point of view of the organization they are divided into two main types - these are lines and channels.

A communication line is a set of cables or wires, with the help of which communication points are combined with each other, and subscribers are combined with the nearest nodes. At the same time, communication channels can be created in a variety of ways, depending on the characteristics of a particular object and scheme.

What can they be?

They can be physical wire channels, which are based on the use of specialized cables, and can also be wave. Wave communication channels are formed to organize all kinds of radio communications in a certain environment using antennas, as well as a dedicated frequency band. At the same time, both optical and electrical communication channels are also divided into two main types - wired and wireless. In this regard, the optical and electrical signal can be transmitted through wires, air, and many other ways.

In the telephone network, after a number is dialed, the channel is formed for as long as there is a connection, for example, between two subscribers, and also as long as a voice session is maintained. Wired communication channels are formed through the use of specialized compression equipment, with the help of which it is possible to transmit information through communication lines for a long or short time, which is supplied from a huge number of different sources. Such lines include one or several pairs of cables at the same time and provide the possibility of data transmission over a sufficiently long distance. Regardless of what types of communication channels are considered, in radio communication they are a data transmission medium that is organized for a specific or several communication sessions at the same time. If we are talking about several sessions, then the so-called frequency distribution can be applied.

What are the types?

Just like in modern communications, there are different types of communication channels:

• Digital.
• Analog.
• Analog-digital.

Digital

This option is an order of magnitude more expensive than analog. With the help of such channels, the extremely high quality of data transmission is achieved, and it also becomes possible to introduce various mechanisms that achieve the absolute integrity of the channels, a high degree of information security, as well as the use of a number of other services. In order to ensure the transmission of analog information through technical communication channels of the digital type, this information is initially converted into digital.

In the late 1980s, a dedicated integrated services digital network emerged, better known to many today as ISDN. It is assumed that such a network over time will be able to turn into a global digital backbone, which provides a connection between office and home computers, providing them with a sufficiently high speed of data transmission. The main communication channels of this type can be:

• Fax.
• Telephone.
• Data transfer devices.
• Specialized equipment for teleconferencing.
• And many others.

As a competition to such means, modern technologies that are actively used today in cable television networks can act.

Other varieties

Depending on the speed of transmission of communication channels, they are divided into:

• Low speed. This category includes all sorts of telegraph lines, which are characterized by extremely low (almost non-existent by today's standards) data transfer rate, which reaches a maximum of 200 bps.
• Medium speed. There are analog telephone lines that provide transfer rates up to 56,000 bps.
• High-speed or, as they are also called, broadband. Data transmission over communication channels of this type is carried out at a speed of more than 56,000 bps.

Depending on the possibilities for organizing data transmission directions, communication channels can be divided into the following types:

• Simplex. The organization of communication channels of this type provides the ability to broadcast data only in a certain direction.
• Half duplex. Using such channels, data can be transmitted both in the forward and in the reverse direction.
• Duplex or full duplex. Using such feedback channels, data can be transmitted simultaneously in the forward and reverse directions.

Wired

Wired communication channels include a mass of parallel or twisted copper wires, fiber optic communication lines, and specialized coaxial cables. If we consider which communication channels use cables, it is worth highlighting a few main ones:

• twisted pair. Provides the ability to transfer information at speeds up to 1 Mbps.
• coaxial cables. This group includes TV format cables, including both thin and thick. In this case, the data transfer rate already reaches 15 Mbps.
• Fiber optic cables. The most modern and productive option. Communication channels for transmitting information of this type provide for a speed of about 400 Mbit / s, which significantly exceeds all other technologies.

twisted pair

It consists of insulated conductors that are twisted together in pairs in order to significantly reduce interference between pairs and conductors. It is worth noting that today there are seven categories of twisted pair cables:

• The first and second are used in order to provide low-speed data transfer, and the first is a standard, well-known telephone wire.
• The third, fourth and fifth categories are used to provide transmission rates up to 16, 25 and 155 Mbps, with different categories providing different frequencies.
• The sixth and seventh categories are the most productive. We are talking about the possibility of data transmission at speeds up to 100 Gb / s, which is the most productive characteristics of communication channels.

The third category is by far the most common. Focusing on various promising solutions regarding the need to constantly develop network bandwidth, the most optimal would be to use communication networks (communication channels) of the fifth category, which provide the speed of data transmission through standard telephone lines.

Coaxial cable

A specialized copper conductor is enclosed inside a cylindrical shielding protective sheath, which winds from fairly thin veins, and is also completely isolated from the conductor using a dielectric. This differs from a standard television cable in that it contains wave impedance. Through such information communication channels, data can be transmitted at speeds up to 300 Mbps.

This cable format is divided into thin, which has a thickness of 5 mm, and thick - 10 mm. In modern LANs, it is often customary to use a thin cable, as it is extremely easy to lay and install. The extremely high cost with a difficult laying quite severely limits the possibility of using such cables in modern information transmission networks.

Cable television networks

Such networks are based on the use of a specialized coaxial cable, through which an analog signal can be transmitted over a distance of up to several tens of kilometers. A typical cable television network is characterized by a tree structure, in which the main node receives signals from a specialized satellite or via fiber optics. To date, such networks are actively used that use fiber-optic cable, with the help of which it is possible to serve large areas, as well as broadcast more voluminous data, while maintaining extremely high signal quality in the absence of repeaters.

With a symmetrical architecture, the return and direct signals are broadcast using a single cable in different frequency ranges, and at the same time at different speeds. Accordingly, the reverse signal is slower than the direct one. In any case, using such networks, it is possible to provide data transfer rates several hundred times higher compared to standard telephone lines, in connection with which the latter have long ceased to be used.

In organizations that install their own cable networks, symmetrical schemes are most often used, since in this case both forward and reverse data transmission is carried out at the same speed, which is approximately 10 Mbps.

Features of using wires

The number of wires that can be used to connect home computers and various electronics is increasing every year. According to statistics obtained in the process of research by professional specialists, approximately 3 km of various cables are laid in a 150-meter apartment.

In the 90s of the last century, the British company UnitedUtilities proposed a rather interesting solution to this problem with the help of its own development called DigitalPowerLine, better known today for the DPL reduction. The company proposed using standard power grids as a medium to provide high-speed data transmission, transmitting packets of information or voice over ordinary power grids, the voltage of which was 120 or 220 V.

The most successful in this regard is an Israeli company called Main.net, which was the first to release PLC (Powerline Communications) technology. Using this technology, voice or data transmission was carried out at speeds up to 10 Mbit / s, while the information flow was distributed into several low-speed ones, which were transmitted at separate frequencies, and ultimately re-combined into a single signal.

The use of PLC technology today is relevant only in conditions of data transmission at low speed, and therefore it is used in home automation, various household devices and other equipment. Using this technology, it is possible to access the Internet at a speed of about 1 Mbps for those applications that require a high connection speed.

With a small distance between the building and the intermediate transceiver point, which is a transformer substation, the data transmission speed can reach 4.5 Mbps. The use of this technology is actively carried out when forming a local network in a residential building or a small office, since the minimum transfer rate provides the ability to cover a distance of up to 300 meters. With the help of this technology, it is possible to implement various services related to remote monitoring, protection of objects, as well as managing the modes of objects and their resources, which is part of the elements of an intelligent home.

Fiber optic cable

This cable is made up of a specialized quartz core, the diameter of which is only 10 microns. This core is surrounded by a unique reflective protective sheath with an outer diameter of approximately 200 microns. Data transmission is carried out by transforming electrical signals into light signals, using, for example, some kind of LED. Data encoding is carried out by changing the intensity of the light flux.

When transmitting data, the beam that is reflected from the walls of the fiber, in which it finally arrives at the receiving end, while having minimal attenuation. Using such a cable, an extremely high degree of protection against exposure to any external electromagnetic fields is achieved, and a sufficiently high data transfer rate is achieved, which can reach 1000 Mbps.

Using a fiber optic cable, it is possible to simultaneously organize the work of several hundred thousand telephone, video telephone, and television channels at once. If we talk about other advantages inherent in such cables, it is worth noting the following:

• Extremely high complexity of unauthorized connection.
• The highest degree of protection against any fires.
• Sufficiently high data transfer rate.

However, if we talk about the disadvantages of such systems, it is worth highlighting the fact that they are quite expensive and necessitate the transformation of light lasers into electric ones and vice versa. The use of such cables in the majority of cases is carried out in the process of laying trunk communication lines, and the unique properties of the cable have made it also quite common among providers that provide the organization of the Internet.

Switching

Among other things, communication channels can be switched or non-switched. The first ones are created only for a certain time, while it is necessary to transfer data, while non-switched ones are allocated to the subscriber for a specific period of time, and have no dependence on how long the data transfer took place.

WiMAX

Such lines, unlike traditional radio access technologies, can also operate on the reflected signal, which is not in the line of sight of a particular base station. The opinion of experts today clearly agrees that such mobile networks open up huge prospects for users compared to fixed WiMAX, which is intended for corporate customers. In this case, information can be broadcast over a sufficiently long distance (up to 50 km), while the characteristics of communication channels of this type include speeds up to 70 Mbps.

Satellite

Satellite systems involve the use of specialized microwave antennas that are used to receive radio signals from some ground stations and then relay the received signals back to other ground stations. It should be noted that such networks involve the use of three main types of satellites located in medium or low, as well as geostationary orbits. In the vast majority of cases, it is customary to launch satellites in groups, since, spreading from each other, they provide coverage of the entire surface of our planet.