FAQ - GSM, DCS, 3G repeater
Original Polish version by Lukasz Kopciuch
Mobile phone conversations in buildings are often difficult to carry on, if not impossible. This is due to the signal attenuation through walls, window panes, ceilings (underground). The problems occur in markets, tunnels, underground car parks, petrol stations, airport halls, hotels. A similar situation can be found in buildings located on the border range of base stations (recreational areas, mountains etc).
The solution to such problems is application of GSM, DCS, 3G repeaters - two-way amplifiers of cellular signals, which significantly improve the quality of data transmission.
In Poland, we organize courses for installers of such repeaters. After passing final exam, each successful candidate gets a special certificate.
Below we have collected frequently asked questions on installation of cellular signal repeaters and answers to the questions.
- What is the principle of GSM, DCS, 3G repeater operation?
- Repeaters are used to amplify signals of GSM, DCS or 3G and to distribute them inside buildings. Any repeater has to be connected to an external antenna directed toward the base station of the particular network, and an internal antenna that distributes the amplified downlink signals and receives uplink signals from the terminals (phones or modems).
GSM Amplifier/Repeater SIGNAL GSM-305 A6765
GSM Amplifier/Repeater SIGNAL GSM-505 A6775
GSM Amplifier/Repeater SIGNAL GSM-1205 A6785
- How to choose a suitable repeater?
- The basic information that one should know before purchasing a repeater is the kind of cellular service which will be used:
- GSM, EGSM - used mainly outside cities, but also in many metropolitan areas; the bands ensure voice connections and low/medium speed Internet connectivity.
- DCS - used mainly in cities (due to higher capacity of a single base station).
- WCDMA (3G) - used in cities, ensures high-speed data transmission (HSDPA), video calls and other 3G services.
- Another important information is how much area is to be covered with the amplified signal:
- How to choose a suitable outdoor antenna and where to place it?
- Suitable antenna type depends on the kind of service (frequency band) and distance from the base station.
- GSM systems:
- DCS systems:
- An ideal antenna in terms of looks and gain (DCS systems are used in metropolitan areas) is A741020.
- 3G systems:
- When the repeater Signal 3G-500 A67100 is located somewhere in a city center, the optimum antenna is A741020 (wide radiation angle); for installations outside the downtown, at distances over 5 km from the base station, the suitable device is the antenna supplied with the repeater (high gain and directivity, small side lobs).
It is very important not to use an antenna with too large gain which would dramatically increase the probability of overdriving the repeater and even pose a risk of parasitic oscillation, causing the device to be inoperative and interfering nearby base stations. One should observe the rule that higher gain of the outdoor antenna requires greater separation from the indoor antenna/s.
- How to choose and place indoor antennas?
- When deploying indoor antennas, one should pay attention to the number of rooms that are to be covered by the amplified signals and the total area. During installation, it is important to keep large distance between the outdoor and indoor antennas. The installation should be started from the lowest level since it is often possible to cover two floors with antenna/s located on one floor. We offer three antennas from TRANS-DATA series, specially designed for cellular amplifiers: A741001, A741002 and A741020.
An example of placing indoor antennas
Another example of placing indoor antennas
- What are the proper cables and connectors?
- GSM, DCS, 3G systems require high quality components: connectors - N-male E84130, N-female E84135, SMA RP male E84150, SMA RP female E84130 - designed for Tri-Lan 240 and Belden H-155 cables. The connectors can be used in installations up 6 GHz, so they ensure a wide margin of performance. They are characterized by low loss, high return loss and screening efficiency. Good impedance matching and screening efficiency of the cables and connectors are vital for the performance and stability of the system, limiting to a minimum incoming and outgoing interference.
- How many users can simultaneously use the GSM, DCS or 3G repeater?
- The maximum number of users depends only on the capacity of the base station of the particular cellular service.
- Does the equipment simultaneously amplify signals of different operators?
- It is possible - the repeater amplifies all signals of cellular operators which are correctly received by the outdoor antenna.
- After installing a repeater, cellular connections are still being interrupted. What is the remedy?
- Usually, the solution to this problem is to find a better location for the outdoor antenna, sometimes also for the indoor antenna/s.
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