Base stations - micro cells - on poles. What it is?
Many Habr's readers began to pay attention to the new equipment on the lighting masts. In general, many new boxes on poles have appeared, and you are probably wondering what it is.
This is what we hang new micro cells. Here is an example of installation:
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In the photo, from the bottom up:
The architecture is standard: the base itself, the transport unit, the power supply. Sometimes an antenna is displayed at the top of the pole to improve coverage (as in the photo), but more often the antenna is simply embedded in the base itself.
Here is another pillar. This is not our equipment, but it has already been discussed at Habré (http://habrahabr.ru/qa/27971/), and identified as the “Device for recording traffic congestion of streets by motor transport” installed by the Moscow traffic police. Such blocks began to appear in parallel with ours, so they are often confused.
This train has nothing to do with cellular networks, so I will return to our base stations.
The base itself when opening the box will look like this:
Here, from right to left, the following blocks are present:
At the same time, these blocks are similar to those used in standard base stations , they are simply placed in a compact package, and are designed for low productivity.
For critical areas where the loss of traffic is not allowed, batteries can be installed in the power converter unit to ensure uninterrupted operation of the base station in the absence of external power for several tens of minutes or hours. However, in general, such batteries are not used, and in the event of a power failure, the base station will simply turn off. Since the designation of such stations is an increase in network capacity, it is usually not at peak times, which means that the macro cell located nearby will “pick up” the signal - subscribers will continue to talk, and those who have used 3G Internet will experience some speed degradation.
Small dimensions, and as a result, less power and capacity. Typical power of such base stations is 5-10W (37 ... 40 dBm), while for standard base stations it is 20W. The number of sectors in a micro base station is usually one, and a maximum of two carrier frequencies in a given sector. The standard macro base supports 3 sectors and up to 3-6 carriers (depending on the standard) in each sector.
It is possible to achieve small dimensions by sacrificing the most important parameter for any equipment that provides wireless communication - the coverage radius that such a base creates. If a standard base station can provide a cover radius of 30–35 km under ideal conditions, and up to 120 km when using additional software options, then the coverage radius of a microcell does not exceed 1 kilometer, and that with the use of a good antenna.
This type of equipment is intended, first of all, to increase the capacity of the mobile network in places of local accumulation of subscribers, as well as to improve the quality of communication in places where it will be too expensive and not very effective to do it with the help of ordinary bases. Therefore, they appear on pillars along the roads, providing communication for buildings near the road and motorists who are bored in traffic jams.
Also a common option for the use of such base stations - shopping complexes or production, where the signal from the street is shielded by thick walls, and the number of people and the need for communication are very large. My colleague from Kazan will talk about this in more detail later, indoor-covering is a separate large topic.
The need for such compact bases was clear from the very beginning of the development of cellular networks; therefore, these solutions evolved along with the development of the entire industry. The first options for GSM networks were still great and heavy:
Here, radio transmitters and control units must be combined in one case. The dimensions of each such base are about 1.3x0.3x0.5 meters, weight 40-50 kg.
In the future, the thought of engineers focused on separating the functionality of the base station, the processor unit stands out in one case, and the unit responsible for generating the radio signal in another, which is just taken out to the antennas. It turned out the so-called distributed base stations. These solutions can not be called micro base stations, but often the equipment that falls on the pillars is not a base station, but only a radio module. Here, for example, RRU and antennas, which are simply tilted away from the main blocks of the base station and are connected to them by fiber:
In the future, the development of this direction will lead to the integration of the transmitter into the antenna, and the emergence of so-called active antenna systems. Many equipment manufacturers are now talking about them, and in the very near future, they may appear in the networks of operators:
However, micro base stations are still solutions in which all the blocks are integrated in one building, and their development continues towards further miniaturization. They can be like this:
New devices - only 10 liters by volume, weight - about 10 kilograms. Micro base stations of these new types are now being actively tested, and this year they will appear on the streets of Russian cities.
Microglasses of the first generation are used in our network quite widely, but most often indoors, and not on poles, since the bases are still too big and heavy.
In the photo with a pillar at the beginning of the topic - RBS3308 standard UMTS, it is used in Moscow and in some other major cities quite often.
More widely distributed variants of distributed base stations, using outdoor transmitters connected to the digital unit with an optical cable. There are a lot of such base stations in Moscow and Russia.
A related issue - for example, new stations are mounted with regard to the “green” technology of BTS Power Saving - and these are distributed BSs where cooling of a radio unit is not done by air conditioning in a room or container, but by ambient air near the antenna. They are used almost everywhere in Russia, except for some of the southern regions - it’s still very hot outside.
In the future, the number of such base stations will steadily grow, all suppliers will release new generations of micro base stations, with smaller dimensions, mass and power consumption. Already, in the VimpelCom network, pilot projects are underway to launch new types of micro base stations, the results of which will make decisions about the large-scale use of new types of bases in a commercial network. In general, they have proven themselves very well, but we have not yet completed the full cycle of testing.
The safety of radiation from a base station antenna was analyzed in detail in the topic here . In short, we have a base station output of 5-10 watts. Horizontal pattern. At a distance of about a meter vertically, it is already completely safe in accordance with the rigid (compared to Western) SanPiN norms. But I would not advise climbing a pole and hugging a sector.
Since the range of action of micro-cells is small (up to a kilometer, typically 200-500 meters), for vehicles moving at high speed, service continuity can be ensured only with careful planning and tuning of all environmental parameters. Seamless voice interconnect (voice handover) is almost always possible.
There is another interesting point. For speeds above 120 km / h, depending on the communication standard, there may be negative effects associated with the time of signaling messages in the operator’s network. The Doppler effect has nothing to do with it, but just know - at a speed of 180 kilometers per hour you cannot watch streaming video in a 3G network simply because of the physics of the process.
If you suddenly find an incomprehensible piece of iron on a pole that cannot be identified immediately, but presumably a telecommunication one - please attach a comment at any time after publication. I am very interested in this topic, so we will try to understand what it is, together with colleagues and habrachchiteli.
This is what we hang new micro cells. Here is an example of installation:
')
In the photo, from the bottom up:
- Power converter (on the right side of the pole).
- UMTS base station itself in a protective box.
- Antenna base station in street performance.
- Radio relay unit for communication with the operator’s platform (BS outgoing channel).
The architecture is standard: the base itself, the transport unit, the power supply. Sometimes an antenna is displayed at the top of the pole to improve coverage (as in the photo), but more often the antenna is simply embedded in the base itself.
Other type of equipment
Here is another pillar. This is not our equipment, but it has already been discussed at Habré (http://habrahabr.ru/qa/27971/), and identified as the “Device for recording traffic congestion of streets by motor transport” installed by the Moscow traffic police. Such blocks began to appear in parallel with ours, so they are often confused.
This train has nothing to do with cellular networks, so I will return to our base stations.
What is inside a microcell?
The base itself when opening the box will look like this:
Here, from right to left, the following blocks are present:
- Digital block processing traffic and transmitting it to the operator's site (long white boards).
- A power supply that stabilizes and converts external power to the required -48DC (gray block at the bottom of the base).
- Radio unit of the required range, for Russia - 2100 MHz.
- Radio filter for receiving and transmitting signals from the antenna.
At the same time, these blocks are similar to those used in standard base stations , they are simply placed in a compact package, and are designed for low productivity.
For critical areas where the loss of traffic is not allowed, batteries can be installed in the power converter unit to ensure uninterrupted operation of the base station in the absence of external power for several tens of minutes or hours. However, in general, such batteries are not used, and in the event of a power failure, the base station will simply turn off. Since the designation of such stations is an increase in network capacity, it is usually not at peak times, which means that the macro cell located nearby will “pick up” the signal - subscribers will continue to talk, and those who have used 3G Internet will experience some speed degradation.
How is this BS different from normal?
Small dimensions, and as a result, less power and capacity. Typical power of such base stations is 5-10W (37 ... 40 dBm), while for standard base stations it is 20W. The number of sectors in a micro base station is usually one, and a maximum of two carrier frequencies in a given sector. The standard macro base supports 3 sectors and up to 3-6 carriers (depending on the standard) in each sector.
It is possible to achieve small dimensions by sacrificing the most important parameter for any equipment that provides wireless communication - the coverage radius that such a base creates. If a standard base station can provide a cover radius of 30–35 km under ideal conditions, and up to 120 km when using additional software options, then the coverage radius of a microcell does not exceed 1 kilometer, and that with the use of a good antenna.
What are they needed for?
This type of equipment is intended, first of all, to increase the capacity of the mobile network in places of local accumulation of subscribers, as well as to improve the quality of communication in places where it will be too expensive and not very effective to do it with the help of ordinary bases. Therefore, they appear on pillars along the roads, providing communication for buildings near the road and motorists who are bored in traffic jams.
Also a common option for the use of such base stations - shopping complexes or production, where the signal from the street is shielded by thick walls, and the number of people and the need for communication are very large. My colleague from Kazan will talk about this in more detail later, indoor-covering is a separate large topic.
How did the technology evolve?
The need for such compact bases was clear from the very beginning of the development of cellular networks; therefore, these solutions evolved along with the development of the entire industry. The first options for GSM networks were still great and heavy:
Here, radio transmitters and control units must be combined in one case. The dimensions of each such base are about 1.3x0.3x0.5 meters, weight 40-50 kg.
In the future, the thought of engineers focused on separating the functionality of the base station, the processor unit stands out in one case, and the unit responsible for generating the radio signal in another, which is just taken out to the antennas. It turned out the so-called distributed base stations. These solutions can not be called micro base stations, but often the equipment that falls on the pillars is not a base station, but only a radio module. Here, for example, RRU and antennas, which are simply tilted away from the main blocks of the base station and are connected to them by fiber:
In the future, the development of this direction will lead to the integration of the transmitter into the antenna, and the emergence of so-called active antenna systems. Many equipment manufacturers are now talking about them, and in the very near future, they may appear in the networks of operators:
However, micro base stations are still solutions in which all the blocks are integrated in one building, and their development continues towards further miniaturization. They can be like this:
New devices - only 10 liters by volume, weight - about 10 kilograms. Micro base stations of these new types are now being actively tested, and this year they will appear on the streets of Russian cities.
Practice use
Microglasses of the first generation are used in our network quite widely, but most often indoors, and not on poles, since the bases are still too big and heavy.
In the photo with a pillar at the beginning of the topic - RBS3308 standard UMTS, it is used in Moscow and in some other major cities quite often.
More widely distributed variants of distributed base stations, using outdoor transmitters connected to the digital unit with an optical cable. There are a lot of such base stations in Moscow and Russia.
A related issue - for example, new stations are mounted with regard to the “green” technology of BTS Power Saving - and these are distributed BSs where cooling of a radio unit is not done by air conditioning in a room or container, but by ambient air near the antenna. They are used almost everywhere in Russia, except for some of the southern regions - it’s still very hot outside.
In the future, the number of such base stations will steadily grow, all suppliers will release new generations of micro base stations, with smaller dimensions, mass and power consumption. Already, in the VimpelCom network, pilot projects are underway to launch new types of micro base stations, the results of which will make decisions about the large-scale use of new types of bases in a commercial network. In general, they have proven themselves very well, but we have not yet completed the full cycle of testing.
Need a foil cap?
The safety of radiation from a base station antenna was analyzed in detail in the topic here . In short, we have a base station output of 5-10 watts. Horizontal pattern. At a distance of about a meter vertically, it is already completely safe in accordance with the rigid (compared to Western) SanPiN norms. But I would not advise climbing a pole and hugging a sector.
Communication when driving in a car
Since the range of action of micro-cells is small (up to a kilometer, typically 200-500 meters), for vehicles moving at high speed, service continuity can be ensured only with careful planning and tuning of all environmental parameters. Seamless voice interconnect (voice handover) is almost always possible.
There is another interesting point. For speeds above 120 km / h, depending on the communication standard, there may be negative effects associated with the time of signaling messages in the operator’s network. The Doppler effect has nothing to do with it, but just know - at a speed of 180 kilometers per hour you cannot watch streaming video in a 3G network simply because of the physics of the process.
Oh, and what a strange piece of iron on my post in front of the house?
If you suddenly find an incomprehensible piece of iron on a pole that cannot be identified immediately, but presumably a telecommunication one - please attach a comment at any time after publication. I am very interested in this topic, so we will try to understand what it is, together with colleagues and habrachchiteli.
Source: https://habr.com/ru/post/194000/
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