The issue of expanding radio coverage is important for both mobile operators and their subscribers. What is the need to use repeaters? Let's try to consider this issue using real examples.
First, let's consider the general issue of radio coverage problems. As you know, radio waves have a certain limit of interference penetration. This limit depends on the frequency and power of radio radiation, physical properties and the thickness of the obstacle. In terms of mass application, it makes sense to take into account radio waves in the 3 MHz - 3 GHz range.
– Waves of the high-frequency range (HF, 3-30 MHz), as a rule, spread over long distances, "circling" obstacles. Mostly, such radio communication is used for long-distance and amateur radio communication. Quite dependent on weather conditions and time of day.
– VHF range (30-300 MHz) is used for technological radio communication in the area of direct or slightly "shadowed" visibility. Mobile Communication. Television and FM broadcasting.
– Ultrahigh (UHF) frequencies (300 - 3000 MHz) are used for technological radio communication within direct line of sight, mobile radio communication, television broadcasting, wireless data transmission systems, radio relay lines.
In terms of using repeaters for mobile communication, we will be interested in radio frequency bands from 450 to 2500 MHz. As you can see, these frequencies lie in a range quite sensitive to the penetration of interference.
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 directional donor antenna and transmitted through an amplification and matching unit to omnidirectional antenna or antenna-acceptors located indoors. Similarly, in the reverse way, the signal from the subscriber station located inside the room, where the main radio coverage does not extend, is received by the internal antenna of the repeater and through the amplification and matching unit is transmitted to the external radio field by the external antenna. Thus, there is a two-way signal transmission from subscribers who are in the main radio field to subscribers who are in the zone of "shadowing" or the complete absence of the main radio coverage, and vice versa.
Let's consider the cases of application of radio coverage expansion that are most often encountered in practice.
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, one-level basement, etc.). As a rule, it consists of a donor antenna, a repeater system unit and one to two to four acceptor antennas for internal use. And here, signal amplification of the order of 60 — 75 dB is used.
If it is necessary to expand the radio coverage of a multi-story 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, radio signal amplification at the level of 85-95 dB is used.
Correction of "shadowing" of radio coverage in mountain ranges.
Necessary in cases of using mobile radio communication in mountainous areas, where some villages are in the mountains. The scheme of application is also extremely simple: "donor antenna located in the main radio coverage created by base stations" - "repeater system unit" - "acceptor antenna directed to the area of shading from the main radio coverage".
In this case, external repeaters are used, with an amplification 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 terrain, 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 rectilinear 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 tracks, use a wide-ranging receiver network of antennas, thereby providing internal radio coverage.
In such cases, it is possible to use fiber-optic repeaters to reduce radio signal loss over long (up to 20 km and possibly higher) distances.
Ensuring radio coverage of sparsely populated areas.
In those places where it is economically impractical to use base stations due to the small number or inactivity of the potential subscriber resource, mobile operators can use repeaters to "level" the coverage. As a rule, this question arises at the border of the main radio coverage from base stations - the so-called "decision edge". In this case, technologically, the scheme of application is the same as when expanding radio coverage in mountain ranges.
The issue of expanding radio coverage is currently receiving considerable attention in the world, as it is a logical continuation of the development of mobile operators in terms of improving the quality of service to their subscribers. Especially in the state of competition for ownership of the subscriber base.
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.
Currently, our company, "Celtek", together with some manufacturers of this type of equipment, as well as leading Ukrainian mobile operators, is conducting technical and economic studies and substantiating the wide use of this type of equipment in Ukraine. And soon it will offer its partners a specific type of equipment, schemes and conditions of its use, and price policy.
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