When a child turns on a tap, he cannot hide his astonished face when he sees water coming out. The same thing happens when you press the light switch and the room lights up. They are such everyday actions that adults, with our diminished capacity for wonder, are no longer able to admire. In the eyes of a child, they are almost magical processes, and as soon as we adults stop to think about it, we would realize how extraordinary there is behind many of our little routines.
Have we stopped to think what happens when we call someone on their mobile? Isn’t it really surprising that our interlocutor, wherever he is, can communicate with us in a matter of seconds? It might seem like a great magic trick, but behind this amazing milestone in telecommunications there is a very complex technological framework that allows us to travel with our voice to any point on the planet in an instant.
The mobility challenge
Before the arrival of the mobile phone, the process of making a phone call was simpler, mainly because we knew where the recipient of the call was: at home, in his office, always next to a fixed terminal. The prefix and the phone number told us where to direct the call.
But when mobile terminals appeared, a new challenge arose: finding the interlocutor wherever he was, even if he was in full displacement. “In the world of mobile telecommunications, the network must solve two fundamental problems: to whom is the call destined and how to reach that subject”. This is how Teresa Herrero, Manager of Strategy and Network Capacity at Telefónica, sums it up.
To make this possible, a complex infrastructure is necessary, composed mainly of base stations, radio controllers, switching centers, kilometers of cable and databases. In addition to permanent and real-time supervision to guarantee the quality of each of the more than 300 million calls that occur every day in a country like Spain.
A journey that begins in the air
Every time we dial a phone number, our call request “flies” through electromagnetic waves, which emit at a certain frequency within the spectrum reserved for this type of service, to one of the more than 22,000 base stations that Telefónica has deployed in our country.
These base stations are the ones that guarantee coverage and, as we move, our signal goes from one to another, depending on their proximity. “Each base station can cover up to 70 km if the propagation conditions are optimal, but Telefónica has stations much closer to each other to guarantee the best coverage,” explains Andrés Ruiz, Telefónica’s Radio Optimization Manager. Sometimes, when there is an increase in the number of users – for example, in summer on the beaches, or in large concentrations of people such as a soccer World Cup – it is necessary to reinforce the coverage of the base stations with other systems, which are normally vehicles who travel to those places to meet the increase in telephone demand.
All the management of the movement of our mobile is done through the radio controllers: “The radio controller is a kind of intelligence that controls the resources of the base station and also coordinates its operation. For example, when a call has to go from one coverage area to another, the radio controller coordinates that process ”he continues. “In order to understand the importance of the base stations in this whole process, it is necessary to think that each one can simultaneously handle up to 300 calls and in a busy hour they can serve up to 5,000 clients.”
Core network: the heart of the system
But despite what one might think, our mobile calls do not only travel through the air, from antenna to antenna: “Once the call leaves the base station, it goes to the core of the network. The core of the network is a set of infrastructures – centrals, databases, kilometers of cable – that is responsible for the connection and provision of voice and data services of the mobile network ”, explains Jorge de los Ríos , Manager of Planning and Control Engineering and Network Core of Telefónica.
The network core is the heart of the system and this is in charge of locating the recipient of the call, deciding the best route to reach him and directing it to his terminal.
From the base station, the call is directed, already by land, to one of the mobile network centers that Telefónica has in Spain. Each exchange consists of two parts, the MSC or Mobile Switching Center and the media gateway or gateway. The MSC is in charge of contacting a gigantic database, called FNR ( Flexible Number Register ), which has more than 40 million records. It checks if the recipient of our call is a Movistar customer. If not, the call is directed to another operator’s networks. If you are a Movistar subscriber, the call continues its journey through the Telefónica network.
Once it has been verified that the recipient is a Telefónica customer, it is necessary to consult another database, the HLR or Home Location Register , where some of their data is verified. “The HLR contains the information necessary to establish communication with the client: their identity for the network, the services they have contracted, their voice mailbox number … But its fundamental task consists of locating the receiver. The HLR always has all the telephones located, even before the call takes place ”, explains Jorge.
In fact, every time we activate our mobile phone, it sends a signal to the nearest base station, which communicates our location to a central station, which is sent to the HLR. As we move, our signal passes to another base station and to the associated exchange, keeping the HLR informed at all times of where we are.
Once the MSC has located the recipient of the call, it can decide which is the best way to reach him between the different exchanges and through the different fiber sections that link them. The media gateway then physically routes the call to the receiving mobile. The call has been established, all in a matter of seconds.
Millions of checks, thousands of kilometers by land, sea and air
It is surprising to know that the whole process of locating our recipient among the more than 40 million records of the FNR and the approximately 700,000 that each HLR has does not take more than 2 or 3 seconds. Jorge also explains to us how far a call can travel to reach its destination, once routed: “It depends a lot on where the customers are. A call can travel from hundreds of meters, if they are very close, for example in the same city, to hundreds of kilometers, if they are in different provinces. Even the call can travel thousands of kilometers under the sea if the clients are in different countries. For example, in a call to the other side of the Atlantic Ocean, the signal has to travel through a submarine cable that can be 8,000 meters deep ”, he tells us.
Guardians of the Net
All this complex verification and routing process is carried out for each of the 300 million mobile calls that the Telefónica network manages daily in Spain. And to this enormous volume must be added the management of all the other voice, data and television services offered by the Company.
In order for the entire system to function accurately and to guarantee quality of service, it is necessary that the millions of elements that participate in the process are constantly supervised. The CNSO (National Center for Supervision and Operation) is in charge of this work.
Helena Llamazares, Head of the National Control Table of the CNSO of Aravaca, tells us what the function of this center consists of “At the CNSO we carry out global, comprehensive and real-time monitoring of all the elements of the network. There are more than 2 million network elements constantly monitored, from the more than 100,000 radio cells, to the exchanges and network nodes of all kinds, passing through the hundreds of thousands of circuits that link all the network elements, the hundreds of thousands of kilometers of cables that support them, or the thousands of equipment that allow managing the energy required by all of them. Everything is monitored 24 hours a day to immediately detect any problem and act to resolve it ”.
“For example,” – Helena continues – “each of the 12 cells that a base station can have, which multiplied by the 22,0000 base stations in Spain means 264,000 cells in total, can send more than 200 data every 5 minutes different. In other words, huge amounts of information are handled. In this center between 15 and 20 TB of data information are processed daily ”.
In addition, the CNSO is in charge of detecting possible improvements in the network and providing information to the engineering and planning areas so that they can carry out optimizations in the system.
the future is here
When Alexander Graham Bell invented the telephone, he probably couldn’t imagine how much it would evolve a century and a half later. It also does not seem easy for digital natives to guess what the communications of the future will be like.
Elena Serna, Radio Innovation Analyst at Telefónica and an expert in new technologies, offers us a glimpse of what that future will be like “The mobile call of the future will be much faster thanks to innovative technologies such as voice over 5G. This technology will be much more reliable than traditional voice, and will also allow much shorter call setup times, which will be vital for the provision of communications in critical applications, emergency situations, high security environments, etc. Call establishment times will be reduced by an average of three to eight seconds ”, he tells us.
“But beyond the voice,” – Elena continues – “5G opens up a world of possibilities to enrich communication, making it more complete, starting from services that already exist today, but that thanks to the new 5G capabilities will be awesome
We do not know if technological innovation will be able to fulfill that old human yearning to teleport from one place to another. What is certain is that it is capable of defying the laws of time and space, making what was once just a chimera a reality.
It looks like magic. But it is technology.
