How we prepared the network in Kazan for the overload of the Universiade
All these people needed cellular communication at the Universiade 2013 in Kazan.
Large sporting events are always overloads for individual sections of the network where the largest number of subscribers is observed. This is not similar in profile to seasonal peaks, for example, for the New Year - there are as many subscribers in a cell as usual, they just all start ringing at about the same time. In the case of the Universiade, the number of subscribers per hundred places simply exhausted the channel capacity.
Preparation began in 2012. The backbone network was modernized (so that the outgoing channel from the city does not turn into a “bottleneck”), the core of the mobile network; construction of new base stations was carried out; construction of new cable lines; work on the transport network.
Perhaps the most difficult thing in just 5 working days was to establish coverage at the newly opened metro stations.
Capacity and coating
The frequency resource allocated for each of the operators is limited. Moreover, the number of physical communication channels, respectively, is also limited. Therefore, in cellular communications the same frequency channels are used repeatedly, but in different territories, in different sectors. To provide coverage in the area of dense development, for example, megacities, the operator needs to use the same frequencies in closely located territories. This causes channel interference.
The closer the BS using the same frequencies, the higher the interference. At some point, the level of interference does not allow building base stations closer to each other. In this case, the maximum density of the coating is achieved. If you build a new base station in such a territory (or bring a mobile one), this will increase the signal level - but not the number of simultaneously talking subscribers. You can’t deceive physics: there will be no more channels.
The base station near the stadium solves two problems: it allows not to mount an additional one (providing maximum capacity) and gives a good signal at the entrance. The chassis is a van.
This is what a mobile BS looks like on the other hand - it’s behind a yellow car.
In Kazan, it is possible to run into such maximum coverage only where new base stations appeared - that is, near the Universiade facilities. In the sense that we do not have a metropolis, and there was no maximum coverage density before. By the Universiade, we upgraded our network to provide capacity close to the maximum.
We replaced the old BS with new ones somewhere entirely, somewhere only separate modules of the distributed BS, modernized the power and air conditioning systems. Implemented HSPA +, the second carriers on 3G, connected 3G BS packet Ethernet / IP.
The planning department also calculated all possible points with increased workload (for example, at railway stations, in residential areas, and so on) - in them we also modified base stations.
There is one more limitation - the main channel. In our case, by the beginning of the Universiade, the main projects for the modernization of the DWDM “Great European Ring” FOL were completed. На базе новых и расширенных существующих каналов DWDM n x 40G проведена следующая подготовка на сети IPBB:
- Организованы новые прямые направления n x 10GE (Уфа – Москва, Волгоград – Москва, Самара — Москва). Traffic from Ufa then went a direct DWDM channel to Moscow, without loading the Kazan-Moscow channel. Physically, Ufa-Moscow still passes through Kazan, but only through DWDM spectral channels, without passing through our routers.
- Added additional capacity to the existing Tula-Moscow and Nizhny Novgorod-Moscow directions;
- The traffic redistribution was carried out, which led to a decrease in the congested Kazan-Moscow direction from 92% to 40%,
To ensure communication in the metro, the not simplest scheme with several antennas and couplers on the feeder path is used. The planning of such a route and the location of the antennas depends on the layout of the premises. Antennas are located at various points in the lobby of the station in order to cover it as efficiently as possible. Special antennas are sent to the tunnels, but the connection in the tunnels depends on their configuration. In straight lines it can be on the whole stretch, but in winding signals there will be no after a couple of bends.
In almost any city where there is a metro, it’s not easy to carry out work - they are allowed only after complex approvals
Both for the construction of new BSs and for the deployment of a mobile BS, it is required, as usual, to obtain new permissions and frequencies. Fortunately, for a number of new facilities we received temporary permits under the accelerated procedure so that we could work during the Universiade.
During the ceremonies, the situation was constantly monitored by engineers and, with a serious increase in traffic, made changes to the settings of the BS to improve service depending on the traffic profile. Priority was given to voice traffic, that is, if the voice load grew, the resources of base stations were redistributed so as to provide subscribers with the opportunity to talk. This was done almost on-line. I remind you that the usual consumption profile is about 5% of the main voice data traffic.
To provide HSPA +, there are certain requirements for the equipment of the BS and the transport network that transmits traffic between the network core and the BS. In some places (mainly on new BSs) it was enough to just download the license, somewhere they did it right after the modernization of the transport network and expansion of channels, and in many cases it was necessary to reinstall the boards providing resources, replace radio modules, and so on. Different actions required different BSs, and there were a lot of them - we worked without a break for several months until the Universiade.
At the same time, we have just finished work on transferring the cable from the city lighting poles to the sewer. This was done as follows: a new line or its new section was being built, the places where the new line was coupled with existing lines or nodes were determined, and a switching plan was drawn up. If a new line is from node to node, then switching was rather simple and often could be done during the day (if there are backup channels for traffic); if the section of the line changed, then welding of optical couplings was required, during which the fibers switched to a new section - such work was carried out only at night with the least load on the network to minimize the impact on the service and customers.
The entrance area, people are much more than usual.
The most significant peak moments were the opening and closing ceremonies, as well as the Sabantuy festival, which gathered a lot of people. As I said, we covered these objects with modified BS, plus we used mobile base stations deployed on the spot.
Near the stadium turnstiles, a mobile BS was used in the configuration of 2G 900 MHz, 2G 1800 MHz, 3G. When deploying, neighbors were registered (to ensure a seamless transition to other neighboring BSs), frequencies were calculated for a 2G BS, immediately after the deployment, the planning and optimization engineer with test equipment checked the interference and the BS's work on passing handovers. The channel from the mobile BS was organized by radio (RRL), with a capacity of 200 Mbps.
Sabantuy was held not in the center, but in a Birch grove near the village of Mirny. There are usually quite a few people there, so I just needed a mobile BS. It was used in the configuration of 2G 900 MHz, 2G 1800 MHz, 3G. At the next BS, 2G transmitters were added to increase capacity in a 2G network, 3G stations were transferred to transport via Ethernet, plus second carrier frequencies were added.
After the Universiade
After Sabantuy, the BS configuration was reduced to 2G, since at normal times there is no such load. Mobile BS were minimized.
Otherwise, we did not change the network configuration in the direction of reduction, that is, in Kazan there is now sufficient reserve for the city to grow several years ahead and other such major events.