We all use a mobile phone a.k.a. cell phone, but few people wonder how it actually works — the answer to this question precisely in the name of the object in question: the mobile phone. Surely the object can be defined as a telephone, as it is useful to take away our voice ("telephone" is in fact composed of the Greek words tèle, which means "far, at a distance" and phonè, which means "sound, voice "), but why is the word" mobile "added to this word?
It is easy to say that the term refers precisely to the type of technology that allows our mobile terminal to function. It is only through the division of the territory into "cells," often partially overlapping, that it is possible to provide the mobile communication service that we all use.
For mobile communication to work properly, it is necessary for our terminal to be connected to the network and for this connection not to be disturbed or interrupted by being in motion. The best solution identified to make sure these two characteristics are always satisfied (or almost) is precisely to implement a network of antennas organized according to a "cell" scheme, not very different from the typical structure, although only in two dimensions, of a beehive.
WHY IS IT CALLED "CELLULAR NETWORK"?
A typical cellular network is constituted by a scheme with contiguous cells, each containing a radio antenna able to connect with the mobile terminals and to maintain the connection itself, at least within a certain distance.
It is intuitive to understand that the power and quality of the signal degrade proportionally to the distance you are at the antenna.
Virtually every mobile phone on the market has a function (the famous "notches") that continuously updates us on how strong our connection with the reference antenna is.
As a general rule, each mobile terminal connects with the antenna from which, as the crow flies, it is less. It is said that the mobile terminal falls into one of the cells managed by that antenna. Each cell can actually have variable dimensions and even very different shapes compared to the hexagon. Each cell, or the portion of space subtended by a certain antenna, is characterized by the fact that it does not have another antenna closer than the reference one.
When we move towards the edge that separates two contiguous cells, what happens is that we move towards an area where at least two different antennas are equidistant from us. Once crossed the edge and passed into the adjacent cell will be the new antenna that manages over the new cell to connect to our mobile terminal. Although, in some cases, depending on the network technologies and the type of mobile terminal in use, this may not even happen, thus allowing us to take advantage of a redundancy in connection for the benefit of communication stability and navigation speed.
However, there are other cases in which the rule of the connection to the nearest antenna is broken, and therefore, our terminal will find itself connected to a different antenna than the nearest one. A certain antenna is congested due to the presence of too many mobile terminals inside the cell that it subtends. A typical case is large gatherings of people like concerts, rallies, etc.) or the presence of natural obstacles or architectural ones that prevent. Otherwise, deteriorate the connection with the nearest antenna, making a connection with a more distant antenna but with a more precise line of sight preferable.
SWITCH FROM ONE CELL TO ANOTHER
We have seen that if during a move, one moves too far away from the antenna of the mobile network to which one is connected, one ends up entering another cell, thus finding oneself closer to an antenna other than the initial one. In this case, the system that manages the cellular network will ensure that our mobile terminal is connected to the new antenna to keep our connection fast and stable.
The procedure of switching from one antenna to another, handover jargon, or even cell switching usually happens without any communication in progress (a phone call, an exchange of data with the network, etc.) being interrupted. In such cases, the cellular network management system can detect the fact that a particular mobile terminal, identified by a unique code (USIM, Universal Subscriber Identity Module). It is connected to several antennas and also which of the antenna has the best connection (the famous "notches" that practically all our mobile phones expose to us).
Thus it gives order to the less performing antennas to interrupt the connection that is managed by the reference cell.
In cellular telephony, the possibility to use, in addition to the voice transmission service, also a data exchange system was introduced starting from the "second generation" ("2G") of mobile telecommunication technologies, also known as the acronym GSM (Global System for Mobile Communication).
In recent years this feature, due to the great expansion of Internet services worldwide, has become increasingly important in the field of cellular telephony, so that it has now become almost its main feature. The most recent mobile terminals (whether they are smartphones, tablets, smart watches, etc.) increasingly exploit these capabilities by multiplying the features and services that make use of mobile bandwidth.
To date, the most widespread mobile telecommunication technology is the "4th generation" & ("3.5G"), 3.5 G is bases on its connectivity, as far as data exchange is concerned, on the HSDPA protocol (High-Speed Downlink Packet Access). It is an evolution of the most successful "third-generation" technology ("3G") better known with the acronym UMTS (Universal Mobile Telecommunications System).
The use of the HSDPA protocol makes it possible to obtain mobile browsing speeds comparable to those of ADSL connections from the fixed network and, more precisely, a maximum theoretical bandwidth of 42.2 Mbit / s. With this type of technology, it is possible to speak effectively with mobile broadband connectivity. 4G was introduced in many countries and this year 5G was launched in some countries too.
Dec 02, 2019