Installing repeaters. Tutorial on installing GSM repeaters. More perfect way to measure signal level

17.03.2012

IN this material The question of practical knowledge for selecting and installing signal amplifiers will be considered. cellular communication (GSM repeaters).

Measurement of the GSM signal and definition of the frequencies of base stations of cellular operators

To measure the signal level, we need a simple phone, namely the NetMonitor function, which is absolutely in every phone. In our opinion, SAMSUNG brand phones are suitable for these purposes in the best possible way. In particular, Samsung C170, x820, S5570 Galaxy Mini. And ten more and a half phones. We recruit the code * # 9999 * 0 # and black screen appears with different technical information. Next, by pressing the up-down arrows, it is necessary to get to the page that is shown below.

Now we'll figure it out what kind of values. Column on the left - these are the numbers of the radio channels for which we can determine the frequency and respectively the GSM range. At the same time, the phone shows only the frequencies of that cellular operator, the SIM card of which is inserted into the phone (in this case, the megaphone of the Moscow region).

In general, it looks like this:

Channels 1-124 - this is GSM 900

Channels 512-886 is GSM 1800 (only 374 channels, which is 3 times more than that GSM 900)

Channels 974-1024 - This is an E-GSM (additional 10 MHz to the left of GSM 900). For this range there is no repeaters, but most Picocell models capture channels 1016-1024 slightly with a smaller gain (in more detail it will be described later).

DOWNLINK - Channel of communication from the base station to subscribers

UPLINK - Channel of communication from subscribers to the base station

GSM 900 - UPLINK 890-915 MHz, DOWNLINK 935-960 MHz

E-GSM - UPLINK 880-890 MHz, DOWNLINK 925-935 MHz

GSM 1800 - UPLINK 1710-1785 MHz, DownLink 1805-1880 MHz

That is, in our example, the phone catches signals from the base stations of the GSM 900 standard megaphone (101, 113, 103 channels) E-GSM (1021 channel) and GSM 1800 (638, 632 channels).

The distribution is presented below cellular operators On GSM channels in the Moscow region:

As can be seen in the megaphone, a sufficiently small resource at frequencies is 900 and the largest at 1800 frequencies. Accordingly, if in Moscow in the office you use megaphone as a corporate operator, it is recommended to choose a repeater 1800 range.

GSM 900: F (uplink) \u003d 890 + 0.2 * n, where n is the channel number F (downlink) \u003d 935 + 0.2 * n

E-GSM: F (uplink) \u003d 880 + 0.2 * (N-973), F (downlink) \u003d 925 + 0.2 * (N-973)

GSM 1800: F (uplink) \u003d 1710 + 0.2 * (N-511), F (downlink) \u003d 1805 + 0.2 * (N-511)

In our case, these formulas do not carry practical application

One GSM channel serves 7 simultaneously spoken subscribers. The 1800th range prevails mainly for densely populated items, i.e. cities, because Can serve a greater number of subscribers. And the 900th range is used everywhere. A fundamental advantage of 900 range - a range of up to 35 km in direct visibility, while 1800 frequency - only 8 km.

Now consider the values \u200b\u200bof the second testimony column on our phone. These are signal levels measuring in DBM (English DBM). The values \u200b\u200bare negative, that is, -60 dBm more than -65 dBm.

Based on our example, we have only one 101i and 638Y channels are in the zone of confident signal reception. Accordingly, if we are talking About the country house, you should choose the repeater 900, because 101i channel is more powerful. And what kind of model it will be a little later.

Already at this stage, we can determine which range we need to install the repeater - 900 or 1800. For this, it is necessary to make measurements of all cellular operators, inserting alternately SIM cards from each of them.

More perfect way to measure signal level

The advantage of the aimed antennas is a large gain ratio, but often the basic stations of cellular operators may be provided in different directions. For a more correct measurement of signals, it is recommended to use the phone with a connected external antenna. Adapter under the outer antenna can be bought on a radio station, the sellers know it as an adapter for modem Yota. Samsung SWC-U200.

How to orient an external antenna?

If you need only one operator, for example, MTS. So try to capture several channels. For example, it is better to catch 2-3 channels with a signal -60 level than 1 channel -50, and the remaining -70.
If you need to provide a signal of all cellular operators, then try to put an external antenna so that the signal to the input of the repeater came approximately the same on all cellular operators, otherwise the radius of the internal antenna will be proportional to the incoming signals. For example, MTS "- 70", Beeline "- 60", MegaFon "- 50" will fall to the input of the repeater, then at the output of the internal antennas we will observe such a situation as follows:

Selection of a GSM repeater model

Consider Example №1:

1. Reserved the signal level by the phone at the point pre-installation External antenna - 72 dBm (chose the most powerful channel). The increasing coefficient of the antenna is 11 dB, respectively, at the output of the antenna we have a signal -72 + 11 \u003d -61 dBm. But it is better to measure the signal from the antenna output, through the adapter to the phone.
2. The loss of the signal in the cable is considered very simple: any cable has its radio frequency characteristics on the manufacturer's website. For example, 100 meters of the 5D-FB cable at a frequency of 900 MHz is lost 20 dB. The higher the frequency of the signal, the greater the loss in the cable. You can see the radio frequency characteristics of the cable. In our case, the length of the cable from the external antenna to the repeater is 10 meters, and the losses are considered: 20 dB is lost 100 meters, respectively, 2 dB will be lost 10 meters.
3. A -61 - 2 \u003d -63 dB signal comes to the repeater input.
4. We look at the reinforcement coefficient in its technical characteristics (in our case ku \u003d 70). We obtain at the output of the amplifier - 63 + 70 \u003d + 7 dBm
5. At the output of the antenna, we get +7 (from the output of the repeater) -2 (losses in the cable) + 7 (ku antenna) \u003d + 12 dBm.

ATTENTION: For each channel, it is necessary to separately calculate calculations (calculating 1 channel, the subsequent are considered almost instantly) How to evaluate the approximate area of \u200b\u200bthe coating from the internal antenna? To do this, we look into the matching table of the decibel and watts at a 50-ohm load.

Our +12 dBm corresponds to 16 MW. Further, to simplify the calculation, our number of MW is closer to the coefficient 4 and we obtain the approximate area of \u200b\u200bthe coating from our antenna 16 x 4 \u003d 64 sq.m. in open space. In the presence of walls and partitions, the area may be somewhat less.

Picocell 900 SXA repeater has an amplification coefficient 70 dB and maximum output power 100 MW on the passport. But in our case, the output power was only 5 MW out of 100 possible.

In the case of GSM 1800 and 3G / UMTS2100 systems, to determine the estimated area of \u200b\u200bthe coating, the resulting output power is recommended to multiply by 3, since At higher frequencies, there is a higher attenuation of the signal in the distribution environment.

The miscalculation technique is quite simple: Knowing the original area of \u200b\u200bthe room, which we need to cover, and licked the signals from the base stations of cellular operators, we can calculate the energy balance of the system and choose the proper model correctly.

Videos How to install cellular signal amplifiers

Example number 2 using a divider uneven power distribution

This system uses two internal antennas. One covers area 25 * 4 \u003d 100 sq.m. (which 14 dBm at the output issues), and the second 50 * 4 \u003d 200 sq.m. (17 dBm at the output). In order to distribute the signal, an asymmetrical divider with side attenuation by 10 dB was selected, and in a straight line - 1 dB. This is done in two cases:

1. Compensate the losses on the cable to a distant antenna at the premises of the same area
2. More rationally distribute the power of the signal to cover the premises of various areas.

Enhancing a signal in the E-GSM band

All Picocell 900 repeaters are not initially calculated on the E-GSM frequency. But due to the imperfection of filters, it is partially affected. Approximately it looks like in the figure below. The reinforcement coefficient of the repeater has its own, the figure shows the Picocell 900 SXA characteristic.

With a row of repeater 70: 1024, the channel will be intensified by 70 dB, 1023 - by 69, 1022 - by 68 and so on. The 1014th channel approximately comes with a strengthening of 48-50. The remaining channels up to 1014th try not to take into account.

When you choose a repeater - try not to save on the equipment. Antennas Take with large gain coefficients, and try to take a cable with a large cross section. All this will allow you to get the maximum result after installing the system.

Actually, possessing these knowledge you can choose and put yourself a GSM repeater.

All questions on this topic are invited to discuss on our forum.

This device is a special device that allows users of Wi-Fi modems to significantly increase the area of \u200b\u200bthe territory on which the corresponding signal is distributed.

Alternative name - signal repeater. Most often, its use is relevant in large rooms, if the modem does not transmit a high-quality signal to distant rooms.

Advantages and disadvantages

IN lately Such equipment is becoming increasingly popular, it is connected with the widespread distribution of wireless networks that people unfold both at home and in office premises.

Among the advantages of these devices, the following positive points can be distinguished:

1. Installing the device in a multi-storey country house allows you to post computers in any convenient location. Regardless of the location of the modem. This advantage has already been rated by people who used to have computers in uncomfortable places, since good signal Was only there.
2. The ability to have a stable and high-quality signal in any rooms, even with thick walls and an abundance of various designs, which used to be suppressed before.
3. Modern design and small size allow you to harmoniously enter the device into any room, and it will be actually inconspicuous.

Certain disadvantages may occur in specific models, in general, problems or negative moments during operation similar devices It was not identified if it was not considered to reduce the speed of the network, which always occurs when adding additional equipment.

However, some users have experienced difficulties with the configuration of the device, so it is highly recommended to purchase only high-quality devices from official manufacturers in order to be able to support or update the firmware and software Through the official website of the manufacturer.

TP-LINK TL-WA850RE model review

TP-LINK is today one of the leaders in the production and sales of signal repeaters. All their products are distinguished by high quality and has many positive feedback from users.

The TL-WA850RE device was selected for consideration, among the features of the device and its advantages, the following can be allocated:

1. Basic equipment includes a network patch cord.
2. TP-LINK warranty is given.
3. All accompanying documentation is duplicated in Russian, it is attached to the repeater both in paper and electronically.
4. The absence of a separate power supply, since in the manufacture of this repeater, an innovative type variety was selected, which allows you to connect the device directly to the outlet, which simplifies the operation process.
5. Dimensions of the device 11x6,5x7.5 cm.
6. Plastic was used for the manufacture of the housing high Qualitywhich is an environmentally friendly material and is characterized by a good strength indicator.
7. All indicators and buttons are signed and conveniently located. The reset button has a hidden location that minimizes the likelihood of its accidental pressing.
8. Functioning with a large number of different wireless network standards.
9. The presence of a special port makes it possible to connect additional devices to the repeater, such as game and television consoles or video players.
10. The level consumed by the repeater of energy does not exceed 3 W.
11. To install, connect, and the operation of this equipment does not require any additional software or special drivers.

How to choose

The modern market offers a wide range of models that are fundamentally different from each other according to the characteristics, although it is not always visible.

For this reason, in the implementation of the choice, it was best advised with a specialist who will give advice on acquisition. specific model To meet certain requirements for the device, or get advice from a company manager, which sells repeaters.

The following selection criteria can be distinguished from which the acquisition of a specific repeater will depend on:

1. Device power It depends on the conditions in which the equipment will be operated. For use in the urban apartment there is no need to overpay for heavy duty instruments, since the most common variety is also suitable. However, if you plan to install a repeater in an office space or in a country house, it is recommended to make a choice in favor of more powerful deviceswhich have a significant coverage area and maintaining a strong signal.
2. Availability or absence of external antennas It also depends on the place where the repeater will be installed. There are no special meaning in them, but devices with the antennas have proven their effectiveness in large areas on the area with a poor signal level.
3. Antennas and other repeater elements can be removable or cast type. It is recommended to choose the instruments of the first variety: the more it will be removable parts, the better because the element of the device can be replaced with a new one. This not only allows you to save funds, but also makes it possible to upgrade the signal repeater.

How to connect

Connecting the repeater is carried out in two steps:

1. TO personal computer Or the laptop this equipment is connected using a standard twisted pair.
2. Connecting the power supply is carried out through the PoE injector.

After it is implemented, you can proceed to the execution of the procedure below. Connecting the repeater is considered on the example of the computer with the installed operating system Windows:

1. Through the Start menu, you must go to the "Control Panel", where you will need to find and select a center that is responsible for networks and provide access to them.
2. After moving to the controls of the networks, select "Changing the Adapter Parameters" on the left side.
3. By selecting a string with the title "Connection by local network»You need to press the mouse button context menu And select the "Properties" tab.
4. In the resulting menu, refer to the "Internet Protocol 4 (TCP / IPv4)" and by pressing the appropriate button, go to the change of its properties and parameters.
5. In the new menu, you must refuse to automatically get an IP address and enter all the necessary data manually. Such information as the IP address and mask is specified by the manufacturer for each individual model.

This is completed on this connection, and you can go to the process of setting up this device.

How to setup

The standard process of setting this equipment is usually as follows:

1. In the settings of the used browser, you must disable the use of proxy servers. After that, an IP address is entered into the address string that corresponds to the connected repeater.
2. In the emerging window, you need to enter the ADMIN login and password.
3. After executing the listed actions, the user will have access to the settings and control menu, in which you want to select the Wireless tab located on the left pane. After that, a few more new lines appear, you need to select the first one, called "Wireless Settings" to configure the repeater.
4. After switching to the title tab, you must find a string with the name "Operation Mode" and select the "Universal Repeater" value for it.
5. After confirming the change and save this parameter, a list of all networks that are in the availability of equipment will appear. It will be necessary to detect and choose necessary network, After that, press the "Connect" key opposite it.
6. After saving all network settings that are automatically defined, the device must be restarted. This is done by pressing the "Reboot" button in the same menu. After rebooting the repeater, all the changes made will take effect.
7. After that, you will need to go to the tab with the name "Wireless Security" and set the encryption parameters and the router password. In order for the signal to appear between devices, the values \u200b\u200bof all parameters specified by the repeater must correspond to the router settings.
8. On this setting this equipment completed. To make sure how true it was produced, you can go to the "Status" tab in the menu. If there appears the name of the router, and there are constantly changing numbers, the repeater is configured correctly and a connection is established between it and the router.

Testing speed through repeater

After the introduction of repeaters to the modern computer market, users arose actual question On the effect of these devices for the Internet speed. To give the most complete and reliable response to this topic, many experts conducted a whole set of testing with aIDA programs 32 Network Benchmark, which included the following activities:

1. Speed \u200b\u200bchecking in normal operation, the computer is connected to the router, the signal repeater is missing. The velocity was 17 Mbps.
2. Connecting the computer is left in the same form as the first testing, but a laptop has been added to the network that has a connection to the signal repeater. The speed decreased to a level of 12.5 Mbps.
3. The laptop was connected directly to the router, and the computer through the repeater, the devices were connected to each other using Patch Cord. The signal is characterized by its stability, but the speed fell to 8.5 Mbps.
4. Last testing consisted in the simultaneous connection of the computer and the laptop to the signal repeater, while the experimental purity was used both a wired and wireless connection method. The signal is good, but the speed fluctuates very much, constantly changing its meanings, the highest indicator reached 37 Mbps.

Subjected to the results of testing tests and, comparing them with each other, it can be concluded that the presence of a repeater in the network slightly reduces the speed, but in some cases such a measure is justified, since this device Enhances the signal.

Also, as can be seen from test results, the best speed of speed saving was recorded when the computer and the laptop is connected to each other using the signal repeater and when excluding this router schema.

Wi-Fi repeater (also called a repeater or repeater) is a wireless device used to expand the network coverage. With it, you can connect to wireless Internet in places with a weak signal reception from the router. The repeater in this case will receive a router signal, and relay to its local network clients.

Choosing a Repeater Installation Place

The maximum effectiveness of using the repeater is achieved when installing on the boundary of the stable Wi-Fi reception from the router. When choosing a location, take into account the layout of the room in which the repeater will be used. You should also pay attention to the location of wireless gadgets, which will be connected and Internet access.

During the search for the optimal place to install the repeater, perform measurements of access speeds. To do this, you can use online services, such as Speedtest. To install repeater, the same recommendations are relevant as for others. wireless devices. Do not place a repeater near large electrical appliances that may interfere with the network. If there are antennas, send them perpendicular to the plane in which the propagation of radio waves is required.

Enable Wi-Fi Repeater

Most repeaters have a built-in power supply, so turn on directly into the outlet. This design allows you to get rid of extra wires, as the cable connection of the power supply and the device is not required. The negative side is to reduce mobility. Installing the repeater at a considerable height is possible only when using the extension or transfer of the outlet.

To turn on the device, simply insert it into the outlet. Almost all models of repeaters begin work immediately after the start of supplying power. But if your device has a separate power button, press it. On the start of operation, the LEDs on the housing are indicated. The values \u200b\u200bof different indication modes (continuous luminescence or flicker) can be clarified in the instructions.

Note! A piece of repeaters is equipped with one or more connectors for connecting a network cable. With their help, you can connect the Internet on computers that are not equipped with a Wi-Fi module.

Connection using WPS

If there is a WPS button on the device, press it to activate the Wi-Fi connection mode without selecting the network and enter the password. After that, press the same button on the router, no later than two minutes after enable Wi-Fi PROTECTED SETUP. With a normal signal and the absence of technical difficulties, the repeater will connect to wireless network And starts to duplicate it.

On some routers there is no such button. To connect to them, the WPS is used by the router setting web interface. You can open it in any browser by typing the IP address of the router in the address bar. As a rule, it is indicated on a separate sticker located on the bottom panel of the device. On the same sticker there are data for the entry: the name of the standard account and password.

Tip! Connection is also possible with entering the repeater PIN code into the adjuster of the router. The code can be clarified on a box or separate liner.

Training Video: Quick Repeater Connection

Configure the repeater through the web interface

Specify additional parameters or configure the network when using the router without WPS, you can in the administrative interface of the repeater. As in the case of the web interface of the router, the input and setting is performed through the browser. Authorization data is also indicated on the sticker, liner or instructions.

23365

Cellular operators use two frequency ranges: 900 and 1800 MHz. In settlements with multi-storey building, cellular communication is most often operating in the range of 1800 MHz, and outside the city and in places of low-rise buildings - in the range of 900 MHz. This is due to the peculiarities of radio wave and the number of free channels.

The lower the frequency (900 MHz), the better and further apply radio waves in the conditions of rough terrain. Thanks to this, base stations can be located far from each other. Another important property of the low frequency radio signal is that they penetrate the buildings better than higher frequency signals.

The radio waves of high frequencies (1800 MHz) quickly fade at large distances and worse penetrated the buildings and rooms. However, these seemingly negative properties become an advantage when using higher frequencies in cities: at every point of the city, each subscriber device, roughly speaking, "sees" only a small number of basic stations. Thus, the base stations almost do not "interfere with" each other.

In the GSM-1800 standard, the number of channels is significantly larger than in the GSM-900 standard, which allows you to simultaneously work to work more subscribers. This is another reason why the GSM-1800 is used in the cities, and in the incomplete areas - mainly GSM-900.

Examination of the object.

First you need to find out from the customer, what kind of cellular problems he wants to solve. In this article, we will consider only increased voice communication and will not consider strengthening mobile Internet (However, the installation of repeaters for the mobile Internet is different from the installation of repeaters for mobile communications Only in small details).

The customer may want to enhance the signal as one operator and the signals of several or immediately all operators.
The distribution of radio frequency bands (i.e. channels) between the operators differs between the regions, this information can be seen in the following tables: for 900 MHz and 1800 MHz.

From these tables can be seen at what frequencies the operators you are interested in. Therefore, already at this stage of work, you can roughly appreciate their complexity and cost.

The object examination should be carried out using the spectrum analyzer. NetMonitor on the phone can only be used as an auxiliary tool, since NetMonitor is not a measuring means and its readings cannot serve as a basis for making any solutions. However, NetMonitor can still be useful, as it, in contrast to the spectrum analyzer, shows the channel number and the name of the operator. With NetMonitor, it is well controlled by the correctness of the measurements performed by the spectrum analyzer.

Before leaving the object, the engineer must familiarize himself with the map location of the base stations. Basically, these cards are created by amateurs and are not official source information. But they can help at least approximately navigate in the situation. These cards are easily accessible on the Internet and are constantly updated.

When arriving at the object, the engineer should examine it and determine the places where it will be possible to put external and internal antennas.

The definition of possible installation sites antennas should be taken into account by several factors:

• directions to the necessary basic stations for external antennas;
• required coverage areas inside indoor antennas;
• the relative position of the internal and external antennas (to prevent self-excitation);
• ease of installation;
• the location of the antennas, amplifiers, cables should arrange the customer.

Definition of the radio frequency environment.

At the next step, it is necessary to measure the levels of downlink signals (i.e. from base stations) at each point possible installation external antennas. Measurements must be carried out using the spectrum analyzer and measuring external antenna. It is necessary to make up the signal dependences tables from the reception frequency.
For example, it is worth the task to strengthen three operators (Beeline, MegaFon and MTS) in the Voronezh region. In the figure (this is a top view of the roof of the house), three points are shown, where there is an access to the roof and where therefore it is possible to establish external antennas (points A1, A2 and A3).

The procedure for action is:

1. In the radio frequency distribution table, we find that in the Voronezh region, operators operate at the following frequencies:

2. With NetMonitor, each operator in each frequency range is chosen by the channel on which the DOWNLINK channels are located. Channels should be selected so that the frequencies from different operators are as large as possible from each other (at least 5-10 MHz). It should be noted that the base station can work only on several channels, and these channels can sometimes change.

3. With the help of the formulas given below, we calculate the frequencies that correspond to each selected channel (N is the channel number).

4. Record the data obtained in the table. For example, these values \u200b\u200bmay be:

5. It turned out six frequencies on which we will carry out measurements. At each point, the possible installation of the external antenna must be found, firstly, the directions from which the levels of signals on each of the six frequencies have maxima, and, secondly, write the values \u200b\u200bof these maxima. All data obtained must be applied to the table and apply to the drawing. In the following figure, the arrows show directions in which the signals have maxima. For clarity, the length of the arrows is proportional to the levels of received signals.

6. From the table and the figure it became clear that the external antennas to enhance the Bilain and MTCA signals can be put at point A1 or A2, to enhance the megaphone - only at the point A3.

In the example we considered, all base stations operate both in the range of 900 MHz and in the range of 1800 MHz. In practice, it is most likely to never, since each BS works in a single range.

Select the location of the internal antennas

We solved the first task - identified for external antennas of the direction to the necessary base stations.

The following task is to determine the necessary zones of indoor coverage for internal antennas:

• the location of the internal antennas depends on the configuration of the inner premises and on what premises the customer wants to strengthen the signal;
• it is necessary to take into account from which materials are the external walls of the building, overlapping and internal partitions. A solid metal roof loosens a 40-60 dB signal; Thick brick, reinforced concrete walls and overlaps weaken the signal at 20-40 dB; Plasterboard, wooden partitions weaken a 10-20 dB signal. It should be considered that higher frequencies of the range of 1800 MHz weakened stronger than the frequency of the 900 MHz range.
• the mutual arrangement of the internal and external antennas should be such that there is no self-excitation of the amplifier, i.e. Such a situation in which the signal from the inner antenna is captured by an external antenna, increases, is supplied to the inner antenna, and so on.

If competently and reliably increase the downlink signal (i.e. from the BS to the phone), then problems with the UPLink signal (i.e., from the phone to the BS) should not be. When using such a signal will also increase. Usually, the uplink gain in the repeater is made with a gain at 5 ... 10 dB smaller than the enhancement of the DOWNLINK channel. So that the phone reliably received the DOWNLINK signal, it should be at least -80 dBm (at the point where the phone is located). So that the base station reliably accepted the UPLINK signal, it should be at least -95 dBm (at the point of space where the base station receiver is located). This is due to the fact that low-noise channel filters and amplifiers that can be enhanced at base stations are used. weak signals from phones. Such an amplifier narrows the signal reception band up to 100 times, reducing up to 10 ... 20 dB its own level of noise of the base station receiver.

However, phones can only receive relatively powerful signals, since there are a number of technical restrictions on the possibility of receiving a signal with greater sensitivity. This is due to the technical complexity of the implementation in the sizes of the telephone antenna with high amplification and the input filter - the receiver preelector.

Phone operating modes when receiving DOWNLINK signals of different power:

Calculation of the DOWNLINK signal

Calculate the DOWNLINK signal for each point of the possible installation of external and internal antennas. To do this, fold:

• signal level at the point of installation of an external antenna;
• strengthening external antenna;
• losses in connectors and cable;
• strengthening the repeater;
• losses in connectors and cable;
• losses in signal splitters (if available);
• amplification of the internal antenna;
• flowing signal inside the room.

It is necessary to make it so that in the room where we want to strengthen cellular communication, the level of the DOWNLink signal was not below -80 ... -75 dBm.

The table below shows the attenuation of the signal in the free space depending on the distance to the antenna. Using this table, it is necessary to amend the attenuation indoors (the maximum distance from the inner antenna is taken to the far corner of the room).

An example of calculating the DOWNLink signal with bs bilayne in the range of 1800 MHz with an antenna installation at point A2:

-81 dBm (DOWNLINK signal with BS bs at A2 point in the range of 1800 MHz)
+14 dB. (strengthening external antenna)
-4 dB. (The external antenna at point A2 may be directed between Bilayne base stations and MTCA, so the antenna amplification will be slightly less than nominal)
-7 dB. (Approximate losses in connectors and cable 10 m long between the external antenna and the repeater)
+ Kr (Remaining the repeater coefficient, we just have to find it)
-7 dB. (Approximate losses in connectors and cable 10 m long between the repeater and the internal antenna)
+8 dB. (strengthening the internal antenna)
-58 dB. (approximate signal attenuation in the room at a distance of 10 meters from the antenna to the long-range corner of the room)

We calculate: -81 + 14-4-7 + KR-7 + 8-58

It turned out (CR-135) dB.

As already mentioned, the level of the downlink signal should be not lower than -80 ... -75 dBm. Therefore, kr \u003d 135-75 \u003d 60 dB. Thus, the minimum reinforcement of the repeater should be at least 60 dB. Since each repeater has an error in specifying the gain (approximately 3 dB), the unevenness of the frequency response (approximately 3 dB) and the noise coefficient (approximately 6 dB), then as a result, it is necessary to choose a repeater with a heart rate of about 70 dB. The specific characteristics of each repeater must be viewed in his passport, but do not forget that repeaters from unfamiliar or unreliable manufacturers can have a very overestimated passport ratio, uneven response and noise coefficient.

Thus, when installing the repeater with a gain of 70 dB inside the room in the far corner, the DOWNLink signal from biline will be -65 dBm.

• sinala level from BS MTCA \u003d -55 dBm
• the BS signal from the megaphone \u003d -87 dBm (we deducted another 10 dB, since the external antenna with a reinforcement 14 dB at a point A2 will receive a signal from the MEGAFON BS with an amplification of about 0 dB, as it will be directed away from the direction of the maximum).

Calculation of the external antenna rejection relative to the internal

Calculations on the interchange of the inner and external antennas must be carried out for all signals of the same range. If one operator works in one range, and the second is different, then their mutual influence will be minimal in this case.

Choosing a repeater taking into account the radio frequency setting

Thus, after studying the radio frequency situation on the object, we received information about the DOWNLINK signals from various operators, namely the levels of channels of each operator. Depending on which operator, on which channels and with what levels signals, the choice of other gain scheme should be selected.

Briefly about reinforcement

Consider a repeater with a gain of 50 dB. Everything is simple here: feeding the signal to its input with the level -83 dBm, we get at the exit -83 + 50 \u003d -33 dBm. However, each repeater, in addition to the gain, indicate the maximum output power (another value is called a "point of compression"). This is the maximum possible output signal of the amplifier, above which the distortions begin to grow and falls the general strengthening of the repeater. Until this magnitude, the gain can be considered linear.

But the fact is that everything without exception manufacturers of repeaters are chatted, indicating the gain and amplitude-frequency response for one channel. And we need to strengthen the set of channels. When multipling multiple channels, the reinforcement coefficient decreases in recalculation to one channel. But more on that later.
The repeater should not work in the mode close to the compression point (for the repeater under consideration it is 20 dBm - this value is indicated in the passport of the repeater and is called the maximum output power), as intermodulation distortion will grow.
Therefore, the repeater must operate in mode in which the outlet power is less than a 10-15 dB compression point.
That is, in the repeater in question, the input can be submitted to the maximum -40 dBm. Then at the output of the repeater will be 10 dBm, which is just 10 dB there is less compression point for this repeater.

How can intermodulation distortion manifest

So, repeat again: the repeater should not work in mode close to the maximum output power.

What does "reinforcement coefficient" mean "

Consider a repeater with a gain of 50 dB and a maximum output level of 20 dBm. This means that the repeater will strengthen one incoming channel with a 50 dB coefficient, provided that there are no other incoming signals in the reinforcement range. This is an ideal case and such almost never happens. There are always several channels at the entrance and some noises and interference. Each additional channel reduces the gain coefficient by 10LG (N / 2). This formula is valid when signal levels are approximately the same and differ from no more than 1 dB. For example, for 10 channels at the input, the reinforcement of the repeater will drop by about 7 dB. And, accordingly, the maximum output level will already be 20-7 \u003d 13 dBm.

If there are not only useful signals at the repeater input, but also interference, they will also reduce the gain in recalculation to the useful channels.

Thus, the reinforcement reinforcement coefficient depends on the amount of enhanced channels. It is important to know that at night the base station can work only on one or two channels, since the number of calls is small. Accordingly, the reinforcement coefficient will be large. In the afternoon, the number of active subscribers increases, the base stations automatically increase the number of channels, and the reinforcement coefficient is naturally reduced.

Ahh repeaters

Ahh is an amplitude-frequency characteristic - the dependence of the reinforcement coefficient from frequency. Ahh repeaters are always non-linear, has dumps at the boundaries of the ranges of 3-8 dB. In addition, the accomplication of each particular repeater differs from achm of another repeater.
ACH perfect Rampirator GSM-900 Range with 50 dB gains should look like this:

But the world of electronics is imperfect, and in the real repeater, the frequency response looks like this (the figure shows the frequency respiter Vector R-610):

As you can see, the repeater will enhance some channels better, and some worse. Especially attentive should be when the channels are at the borders of the ranges.
By virtue of the characteristics of the schemes of cheap repeaters, the higher the reinforcement of the repeater, the more uneven response, it has. The authors of this article came across Chinese and Russian copies of repeaters, having non-uniformity frequency response in the operating range of up to 18 dB. It also needs to be considered when installing.

It is necessary to pay attention

• If the frequency difference in the incoming channels is 5-10 MHz with the difference of their levels of 10 dBm, then all these channels will increase without distortion.
• If the frequency differences of the incoming channels are about 1 MHz with a difference of their levels of 10 dB, the weak signal can be depressed stronger. In this case, it is necessary to either enhance the channels separately using different repeaters, or attempt to find other channels, strongerly separated from each other.

Ways to improve gain quality

• You can use channel repeaters. They enhance only a narrow strip with the necessary channels. Such repeaters are somewhat more expensive than normal, but sometimes only their use can enhance the signal in a complex radio frequency setting.
• It is necessary to buy equipment (repeater, cables, connectors, filters, etc.) only in reliable suppliers and desirable for those who themselves are engaged in the installation of repeaters, since only then the risk to run into the left equipment with incomprehensible characteristics will be minimal.
• You can use Uplink and DownLink signals on those frequencies that we want to strengthen. This is a way that can only use very experienced installers directly interacting with repeater manufacturers.

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