How MTS launched 3G and LTE in the mountains using a solar-powered repeater
How to make the connection of the third and fourth generation to where only 2G is used due to the fact that the mountains interfere with the direct visibility of base stations, and there are no necessary power capacities for installing additional BS? Our expert Konstantin Kilber will talk about the relevant experience of MTS - the example of installing an active repeater for the radio relay line in a small village in the Republic of Adygea in 2015. So, we pass the word to our specialist.
The task before us was not simple: to ensure the maximum throughput speed from the base station in the village of Guzeripl, the Republic of Adygea. This is such a place at the foot of the Main Caucasian Range, at an altitude of 670 meters above sea level, with a population of just over 100 people.
Mountains became the main problem - they interfered with the direct line of sight of radio relay stations (RRS), which are the transport component for base stations. Previously, a passive repeater was built (without active equipment): two radio-relay antennas connected by a waveguide. The signal from the relay station (RRS 1) arrives at one antenna, through the waveguide the signal enters the second antenna, then the signal goes to the second part of the relay station (RRS 2). The bandwidth of a radio relay line with a passive repeater was no more than 30 Mbps, which is very small for modern communications. In this scenario, only a 2G base station can work, but with 3G and LTE, difficulties already arise.
To remedy the situation, an active solar-powered repeater was needed, since energy problems in the mountains are a big problem. What is an active repeater? In fact, these are two transceivers, with the help of which the throughput of the radio relay line is increased. By increasing the speed (bandwidth), we can use the Internet and watch videos. This is how the repeater installation scheme looks in the network.
It is an active repeater design of two solar panels, two 12 volt batteries and two antennas, a transceiver unit and a compact box, inside which controllers and batteries are located. Active repeaters do not need external power supply, which allows them to be placed where there are problems with power supply and where it is unprofitable to extend a new power line. The device consumes only 5 watts. It turns out that the battery can work for half a month even without charging. The device has a controller that monitors that the battery does not recharge (it cuts it off) or does not go into a deep charge. The sun came out - the charge went. This allows you to save the battery from failure. It turns out that there are two independent energy supply systems that work in parallel. The survivability of the device is very good.
If we talk about panel antennas, it is desirable that they be of good quality. There are several types of antennas, in particular, polycrystal and single crystal. The most productive are single-crystal. They are slightly more expensive, but their efficiency is higher, about 22%. They need the perpendicular direction of sunlight. With scattered light, their performance decreases, and charging is not as intense as with direct rays.
As a result, after installing an active repeater, the throughput in Guzeripl was 10 times higher - from 30 Mbit / s to 300 Mbit / s. Residents were, of course, very happy. This allowed us to connect the category of “VIP-clients” - who need Internet access at high speed.
Another distinctive feature of the active repeater is that its installation does not require large human resources. Although you just need to understand that they are installed, as a rule, in poorly populated places, so it is important to take care of the anti-vandal arrangement. Of course, you won’t be safe from vandals. Hacked even well-protected base stations, what can we say about the active repeater. In Guzeripl, we set up a small turret (16m) and fenced it with an iron fence with barbed wire.
If we talk about the reliability of active repeaters, it’s enough to say that we installed our equipment on June 1, 2015, and so far it has been working flawlessly. They survived both winter and summer, spring and autumn - and never once did the emergency recovery team go there. This means that, firstly, the engineers did everything qualitatively, secondly, the equipment proved its reliability, and thirdly, no hacks occurred.
If we talk about the shortcomings of the device, then they are few. For example, it does not support remote monitoring of parameters. That is, you can not see remotely - the repeater is working or not. It is necessary to judge by speed - if it “fell” or the connection was lost at all, then the active repeater failed. Another minus is the possible “contamination” of the panels. Either from dirt, or from sticking snow. That is, it is not yet possible to completely leave such equipment unattended - at least once every three months you need to visit, wipe the panels and watch the general physical condition. But the benefits are definitely more. Especially payback, given that we do not need to pull power lines - and this is a very expensive pleasure.
Installation of active repeaters
There are two installation methods. The first option is to install a square or triangular iron structure 1-2 m high on a reinforced concrete base. Equipment and antennas are placed on a metal structure. This method is more economical.
The second option involves the construction of a tower in places where it is difficult to achieve line of sight due to terrain or vegetation. Here is a small amateur video from the installation of a repeater in the village of Guzeripl.
For greater reliability of the network, we make both an active repeater and a passive one in parallel. It turns out that the radio relay station operates on two RRL trunks. When everything is working properly, the network works through an active relay, and the second passive is in reserve. If for some reason the active repeater fails, the signal goes to the parallel trunk - where the passive repeater works. In the case of switching to the backup trunk, the transmission rate, of course, drops from 300 Mbit / s to 30 Mbit / s, until the active repeater is restored. By the way, our emergency response team has all the spare parts (spare parts) for the repair of repeaters. Up to the solar panels, the transceiver itself and the batteries. As a rule, in addition to the transceiver and the battery, there is nothing to fail.
Having gained positive experience, we decided to continue to introduce active repeaters. We bought about 20 sets, 6 of them have already been launched: in the Krasnodar Territory and in the Republic of North Ossetia-Alania. Ahead of the launch of other kits.