As we did the cellular coverage inside a large building with a variety of metal structures
We have built a new shopping center in Samara . Large, beautiful and with lots of metal in the designs. Inside 6 hefty commercial floors and 27 office, plus parking. We walked with a measuring instrument over it and got just such a depressing picture of coverage:
Red - RX less than -95 dBm, green -85
Simply put, inside the shopping center our cellular coverage was confident only in the gallery opposite the large window. At the same time on the street in a centimeter from the wall covering 100%.
')
The task is to provide good coverage of 2G and 3G throughout the building. Of the additional conditions - the metal even in the glass (they are tinted), a complex configuration of mines. And yet the finished finish inside virtually eliminates the laying of something more or less serious. Below - how we solved this problem and what we got in the end.
In smaller buildings, in such situations, either a repeater or a single microcell is usually installed. In both situations, we need accurate calculations, but the architecture is quite simple. In this case, the repeater simply would not cover the building, and several hundred need to be combined into a common system with its own characteristics. But I will start from the very beginning - there are still ways to solve the problem.
First, you can take a coaxial cable with directional couplers and power dividers, pull through all the rooms and poke emitters. Something like this is done in the metro in the tunnels - slot radiators on the cable (the details are here ).
Pros - quickly, cheaply, do not need specific equipment, there are practically no restrictions on the frequency ranges. Cons - complex design, high cable losses, plus a very thick cable is needed, which is simply impossible to lay on the finished finish. And even if you suddenly want to expand something, you will have to consider it all over again. In general, the method was rejected.
Option number 2 - switchgear, optical converters and active units, plus antennas in the building.
It is simple to design, easy to adjust and expand, optics does not impose restrictions on the distances inside the building, plus the cable itself is thin, easy to lay. Due to the fact that all elements are active, it is very easy to localize the damage and maintain. But at the same time the active equipment is expensive, you need a lot of cable routes (and this is a long and complex coordination). On common thought, we decided to consider the option with mixed systems.
The idea is simple: a two-rank network, where the first level is active systems, and from them, according to the “wheel and spokes” architecture, passive coaxial cables with radiators diverge. The issue of laying on top of the finish was solved, the cost was reduced. But the risk of design errors rose sharply - and, therefore, the possibility of not getting into the necessary sanitary zones. By common thought, we decided not to do so.
At the stadium Lokomotiv, Donbass Arena and at the stadium in Houston a very interesting solution is used with optical fiber and twisted pair. Fits perfect. Here is the architecture:
The configuration is very flexible, scaling is extremely simple, the distance is up to 20 kilometers to the signal source. You can configure the network for each service, for example, like this:
After technical analysis decided to do this way. Calculated. First, they included one point, measured the coverage (they used the standard Nemo_Outdoor_6.3.1.11, if anyone is interested), did the necessary calculations taking into account the attenuation of the signal in different structures of the building. It turned out only 2-3 points per floor for optimum coverage. They do not break through the floors, so the calculation was quite simple - just in layers in the plane.
We made a remote station in our server room, from the station, coaxially split units, small in size (approximately A4). Then again checked the coverage. Then - compliance with sanitary standards (units emit a maximum of 100 milliwat, in practice - less), that is, the safe distance is strictly in the center of the radiation pattern - 1 meter.
The blocks themselves, which can be seen in the shopping center, are:
Mobile Access MA-1000/2000 / HX transmit, respectively, GSM 14, 12 and 29 dBm.
Our colleagues at the facility solved the problem differently. One technical team put the base station outside with a directional sector on the mall. We walked with our measuring complex - it turned out to be a dotted line of red and yellow areas. The second technical team has put the same passive system. The coverage is “green” with large areas of yellow, the Internet is slower, they have been implemented for a long time, almost a month and a half.
We had this:
It became:
That is, the coverage was good almost throughout the shopping center. Plus there was a fast Internet. For 3G comes the channel at 21 megabits / second. The actual transmission rate for the subscriber under normal conditions is 563 kb / s (-65.5 dBm).
All implementation took 2 weeks.
This is the second such project in Russia, so it was very interesting to compare it with what other technical teams were doing. The experience is definitely cool.
Red - RX less than -95 dBm, green -85
Simply put, inside the shopping center our cellular coverage was confident only in the gallery opposite the large window. At the same time on the street in a centimeter from the wall covering 100%.
')
The task is to provide good coverage of 2G and 3G throughout the building. Of the additional conditions - the metal even in the glass (they are tinted), a complex configuration of mines. And yet the finished finish inside virtually eliminates the laying of something more or less serious. Below - how we solved this problem and what we got in the end.
In smaller buildings, in such situations, either a repeater or a single microcell is usually installed. In both situations, we need accurate calculations, but the architecture is quite simple. In this case, the repeater simply would not cover the building, and several hundred need to be combined into a common system with its own characteristics. But I will start from the very beginning - there are still ways to solve the problem.
Passive systems
First, you can take a coaxial cable with directional couplers and power dividers, pull through all the rooms and poke emitters. Something like this is done in the metro in the tunnels - slot radiators on the cable (the details are here ).
Pros - quickly, cheaply, do not need specific equipment, there are practically no restrictions on the frequency ranges. Cons - complex design, high cable losses, plus a very thick cable is needed, which is simply impossible to lay on the finished finish. And even if you suddenly want to expand something, you will have to consider it all over again. In general, the method was rejected.
Active systems
Option number 2 - switchgear, optical converters and active units, plus antennas in the building.
It is simple to design, easy to adjust and expand, optics does not impose restrictions on the distances inside the building, plus the cable itself is thin, easy to lay. Due to the fact that all elements are active, it is very easy to localize the damage and maintain. But at the same time the active equipment is expensive, you need a lot of cable routes (and this is a long and complex coordination). On common thought, we decided to consider the option with mixed systems.
Mixed systems
The idea is simple: a two-rank network, where the first level is active systems, and from them, according to the “wheel and spokes” architecture, passive coaxial cables with radiators diverge. The issue of laying on top of the finish was solved, the cost was reduced. But the risk of design errors rose sharply - and, therefore, the possibility of not getting into the necessary sanitary zones. By common thought, we decided not to do so.
Mobile Acccess (with low power radio)
At the stadium Lokomotiv, Donbass Arena and at the stadium in Houston a very interesting solution is used with optical fiber and twisted pair. Fits perfect. Here is the architecture:
The configuration is very flexible, scaling is extremely simple, the distance is up to 20 kilometers to the signal source. You can configure the network for each service, for example, like this:
After technical analysis decided to do this way. Calculated. First, they included one point, measured the coverage (they used the standard Nemo_Outdoor_6.3.1.11, if anyone is interested), did the necessary calculations taking into account the attenuation of the signal in different structures of the building. It turned out only 2-3 points per floor for optimum coverage. They do not break through the floors, so the calculation was quite simple - just in layers in the plane.
We made a remote station in our server room, from the station, coaxially split units, small in size (approximately A4). Then again checked the coverage. Then - compliance with sanitary standards (units emit a maximum of 100 milliwat, in practice - less), that is, the safe distance is strictly in the center of the radiation pattern - 1 meter.
The blocks themselves, which can be seen in the shopping center, are:
Mobile Access MA-1000/2000 / HX transmit, respectively, GSM 14, 12 and 29 dBm.
Our colleagues at the facility solved the problem differently. One technical team put the base station outside with a directional sector on the mall. We walked with our measuring complex - it turned out to be a dotted line of red and yellow areas. The second technical team has put the same passive system. The coverage is “green” with large areas of yellow, the Internet is slower, they have been implemented for a long time, almost a month and a half.
Total
We had this:
It became:
That is, the coverage was good almost throughout the shopping center. Plus there was a fast Internet. For 3G comes the channel at 21 megabits / second. The actual transmission rate for the subscriber under normal conditions is 563 kb / s (-65.5 dBm).
All implementation took 2 weeks.
This is the second such project in Russia, so it was very interesting to compare it with what other technical teams were doing. The experience is definitely cool.
Source: https://habr.com/ru/post/194960/
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