The issue of expanding radio coverage is important both for mobile operators and their subscribers. Why is it necessary to use repeaters? Let's try to consider this question on real examples.
First, consider the general issue of radio coverage problems. As you know, radio waves have a certain limit of penetration of obstacles. This limit depends on the frequency and power of radio emission, the physical properties and thickness of the obstacle. In terms of mass application, it makes sense to take into account radio waves in the range of 3 MHz - 3 GHz.
— Waves of the HF range (HF, 3-30 MHz), as a rule, propagate over long distances, "going around" obstacles. For the most part, such radio communications are used for long-distance and amateur radio communications. Quite dependent on weather conditions and time of day.
— The VHF band (30-300 MHz) is used for technological radio communication in the zone of direct or slightly "shadowed" visibility. Mobile connection. Television and FM-broadcasting.
— Ultra-high (UHF) frequencies (300 - 3000 MHz) are used for technological radio communications within line of sight, mobile radio communications, television broadcasting, wireless data transmission systems, radio relay lines.
In terms of the use of repeaters for mobile communications, we will be interested in the radio frequency ranges from 450 to 2500 MHz. As you can see, these frequencies lie in a range that is quite sensitive to the penetration of obstacles.
The standard scheme for using a radio coverage repeater is quite simple: an external radio signal of a certain frequency and with characteristic properties that depend on the type of mobile radio communication system (GSM, CDMA, WCDMA, DCS etc.) is received by a narrowly directed donor antenna and transmitted through an amplification and matching unit to an omnidirectional antenna or acceptor antennas located indoors. Similarly, in the opposite way - a signal from a subscriber station located indoors, where the main radio coverage does not extend, is received by the internal antenna of the repeater and transmitted through the amplification and matching unit to the external radio field, by an external antenna. Thus, there is a bidirectional signal transmission from subscribers located in the main radio field to subscribers located in the zone "shadowing" or the complete absence of the main radio coverage, and vice versa.
Let's consider the most common cases in practice of using the radio coverage extension.
Expansion of internal radio coverage of premises.
It can be a system for expanding radio coverage within a small spacious room (home apartment, private house, office, conference hall, assembly hall, cafe, shop, single-level basement, etc.). As a rule, it consists of a donor antenna, a repeater system unit and one - two - up to four acceptor antennas for internal use. In this case, a signal amplification of the order of 60 - 75 dB is used.
If it is necessary to expand the radio coverage of a multi-storey building, an apartment building, a multi-section shopping center, repeaters of a higher class are used, capable of providing the operation of about 20 - 40 internal antennas. In this case, a radio signal gain of 85 - 95 dB is used..
Correction of "shading" of radio coverage in mountain ranges.
It is necessary in cases of using mobile radio communications in mountainous areas, where some villages are located in the intermountain. The application scheme is also unusually simple: “donor antenna located in the main radio coverage created by base stations” - “repeater system unit” - “acceptor antenna aimed at the shadow area from the main radio coverage”.
In such cases, outdoor repeaters are used, with a gain of 60 - 90 dB.
Expansion of radio coverage in tunnels.
This issue is relevant both for short-length road and railway tunnels in mountainous or hilly areas, and for underground transport systems such as the subway, tunnel systems for laying cable lines, underground civil defense systems, etc.
As a rule, these systems consist of straight tunnel sections, which makes it possible to use narrowly directed antennas, for example, of the “wave channel” type, as acceptor antennas.
Also, such systems can be (and are) applicable in underground mining mines. Multi-horizon mines, with many drifts, use a widely branched acceptor antenna network, thereby providing internal radio coverage.
In such cases, it is possible to use repeaters with fiber optic communication to reduce radio signal losses over large (up to 20 km and possibly more) distances.
Ensuring radio coverage of sparsely populated areas.
In those places where it is not economically feasible to use base stations due to the small number or low activity of a potential subscriber resource, mobile operators can use repeaters to “equalize” coverage. As a rule, this question arises at the border of the main radio coverage from base stations - the so-called "edge-solution". In this case, the technological scheme of application is the same as with the expansion of radio coverage in mountain ranges.
The issue of expanding radio coverage is now being given considerable attention in the world, since this is a logical continuation of the development of mobile operators to increase the quality of service for their subscribers. Especially, in a state of competition for the possession of a subscriber park.
Such issues can be resolved both centrally, with the participation of a specific mobile operator, and individually - by the subscriber, if this subscriber has experience in installing, configuring and maintaining this or similar equipment.
At the moment, our company, Celtec, together with some manufacturers of this type of equipment, as well as leading Ukrainian mobile operators, is conducting feasibility studies and justifying the widespread use of this type of equipment in Ukraine. And soon he will offer his partners a specific type of equipment, schemes and conditions for its use, as well as a pricing policy.