How we set the highest altitude base station in Eastern Europe

    Recently, we provided high-speed mobile Internet and mobile communications to the upper sections of the Elbrus ski slopes. Now the signal there reaches a height of 5100 meters. And it was not the easiest installation of equipment - the installation took place over two months in difficult climatic conditions. We’ll tell you how it was.


    Builder Adaptation

    It was important to adapt builders to high mountain conditions. Arrivals took place two days before the start of work. Two nights in one of the houses for climbers did not reveal a tendency to mountain sickness (nausea, dizziness, shortness of breath). On the second day, the installers began light work on preparing the site. Technological breaks of 3-5 days each were arranged twice, when the builders went down to the plain. Re-adaptation was easier and faster (enough days). Of course, sudden changes in the weather dictated their conditions. For example, it was necessary to purchase self-heating heating pads to ensure normal working conditions for installers.

    Site selection

    At the stage of selecting the site for the construction of the base station, first of all, it was necessary to take into account the specific meteorological conditions of the highlands. First of all, the site must be purged. At the same time, windward and leeward snow deposits should not be created that impede access to the site. In order to fulfill these conditions, it is important to identify the direction of the prevailing wind, from whose side the air flow to this area most often comes + its strength.

    Long-term meteorological observations gave such averaged values ​​of the wind rose (%). The dominant direction is highlighted in red.


    As a result, it was possible to pick up a small ledge, which can be reached without much difficulty in the most snowy period. Its height is 3888 meters above sea level.


    Installation of BS equipment

    The lifting of materials and equipment was carried out on the snow groomers, since the wheeled machinery was useless due to the beginning of snowfalls. During daylight hours the snowcat managed to rise no more than two times.


    Smaller equipment was delivered by cable car. Work began at sunrise. It is possible to predict the weather on the slope of Elbrus, but with a small degree of probability. In the most clear weather, a cloud may appear above the peaks (as they say - Elbrus put a hat on). Then it can either melt, or in an hour turn into fog, snow, wind. If the weather worsens, it is important to cover the tool and materials in time so as not to dig out later.


    During the design, the “site” was raised almost three meters above the ground, pouring soil. This was done so that the site is not covered with snow and there is no need for regular rolling of snow groomers.

    The second task was to securely fix the design of the "site", since the wind speed at the altitude of the base station reaches 140-160 km / h. Given the highly located center of mass, the height of the structure and its windage, it was decided not to be limited to concreting the pipe supports into the pit. Moreover, when developing the soil for the installation of supports, very hard rock was found, therefore, it was possible to deepen only by a meter (under normal conditions, deepening takes place by more than two meters). I had to additionally mount gabion type weights (mesh with stones - see the first photo).

    The design parameters of the base station on Elbrus turned out to be the following: the width of the base was 2.5 * 2.5 meters (based on the dimensions of the heating cabinet where the equipment had to be installed). Height - 9 meters. They raised it so high that there was a blown through station and it was not covered with snow. For comparison, flat base stations do not raise to such a height.

    The third task was to provide sufficient structural rigidity necessary for the stable operation of microwave equipment in high winds. For this, the structure was reinforced with cable ties.

    Equally difficult was the provision of thermal mode equipment. As a result, all the equipment of the station, which receives and transmits a radio signal, was placed in a special protective box, which ensures uninterrupted operation of the station in any weather conditions. Such so-called Arctic containers are designed for the harsh conditions of the Arctic - high wind loads and freezing temperatures. They can withstand temperatures up to -60 degrees in high humidity.

    Do not forget that during operation the equipment also heats up, so a lot of effort was spent on ensuring normal heat mode. Here we had to take into account the following factors: greatly reduced atmospheric pressure (520 - 550 mm Hg) significantly worsens the heat transfer of air. In addition, the technological holes immediately freeze, and snow accumulates through any gap in the room, so it is impossible to use free-cooling systems.

    As a result, the area of ​​wall insulation and the operating mode of the heating cabinet were selected empirically.


    I also had to solve the problem of grounding and lightning protection. The problem is the same as that of colleagues in the northern regions on permafrost. Only here we had bare rocks. The resistance of the circuit varies slightly depending on the weather, but always 2-3 orders of magnitude higher than permissible. Therefore, I had to pull the fifth wire along with the power supply to the cable car electrical substation.


    Technical characteristics of the base station

    Taking into account the wishes of the Ministry of Emergencies of the Russian Federation, in addition to the base station of the 3G range, the project provided for the construction of a 2G BS. As a result, we got high-quality coverage of UMTS 2100 MHz and GSM 900 MHz of the entire southern slope of Elbrus, including the main ascent to the bend (5416 m) of the saddle.

    As a result of work on the “site”, two distributed-type base stations were mounted, consisting of a base frequency processing unit (BBU) and an external radio frequency unit (RRU). The CPRI interface is used between the RRUs and the BBUs, which connects the two modules using optical cables.

    GSM standard - 900 MHz - DBS3900 manufactured by Huawei (China).
    WCDMA standard - 2100 MHz - RBS 6601 manufactured by Ericsson (Sweden).
    Transmitter power is limited to 20 watts.

    The base station is powered by cableway power grids - there is no alternative. When the power is turned off, the 3G base station is turned off by operating personnel and only one 2G sector remains, looking towards Elbrus. This helps to always stay in touch, including rescuers. Standby power is enough for 4-5 hours. When providing access for personnel to repair equipment, special problems should not arise when the cableway is operating. In case of emergency and increased urgency, a snowmobile lift is provided.

    Posted by Sergey Elzhov, Technical Director of MTS in the CBD

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