Mobile phones played a fundamental role in telecommunications and now are essential devices in everyday life.
But how come, a so small device allows us to communicate with any person around the word, no matter where we are?
In this video we will explain how your mobile phone is able to trasfer the call, and why there are many generations of mobile networks.
The modern mobile phones are able to transfer the calls thanks to the support of the msc, acronym for: MOBILE SWITCHING CENTERS which, as we will see, contains the main information of your sim cards and provides to transfer the calls to the right recipients.
JAES is constantly engaged in the supply of all those spare parts necessary for the proper functioning of the mobile switching centers, which they need to be constantly working, 24 hours a day.
Let’s try to get a closer look of the main components of a mobile phone, which are responsible for the call transfer.
When you want to start a phone conversation, your voice is recorded by a microphone.
The microphone is nothing but a detector and a sound converter, which converts sound pressure into electric signal.
Once the soundwave of your voice has been transformed into an electrical signal, this signal is "sampled" by a tiny sensor inside the phone, called: MEMS sensor.
This sensor basically samples the electric wave of your voice many times per second and digitizes it.
Thus, we pass from the analog world to the digital world, since the wave is "converted" into discrete values, represented by a sequence of zeros and ones.
In this way your voice, after being transformed into a digital signal, can be easily memorized and eventually sent, through the antenna.
The antenna sends the digital signal of your voice in the form of an electromagnetic wave. This wave is able to transmit the zeros and ones of the signal, by modifying its AMPLITUDE, FREQUENCY and PERIOD values, or even changing their combination.
Taking the example of FREQUENCY, the zeros are transmitted in the form of a low-frequency wave, while the ones are transmitted in the form of an high-frequency wave.
The electromagnetic wave containing the information of your voice, must be able to reach the phone receiver of the person with whom you want to talk.
Unfortunately, electromagnetic waves are not able to travel long distances, and lose their power whenever their trajectory is deviated by large buildings, electronic devices, or in the presence of bad weather conditions.
But even if there are no obstacles along the wave trajectory, its linear path could not go on forever, due to the curvature of the Earth.
For this reason, special antennas are installed. The so-called CELLULAR RADIO TOWERS, which use cellular technology to transmit the electromagnetic wave to the right recipient.
Cell towers are distributed throughout the territory, in order to divide it into many hexagonal areas. Each area is simply called CELL, and has its own antenna with its own FREQUENCY BANDS.
Usually CELLS are connected to each other by radio bridges or specific optical fiber cables placed under the ground, or even under water, to ensure national and international connections.
As we’ve already said, the electromagnetic wave produced by your phone contains the information of your voice. This wave is collected by the antennas of the cell tower of the hexagonal area in which you find yourself. The radio cell converts the wave into LIGHT PULSES which are subsequently transferred and collected at the base of the cell tower, right inside the TRANSCEIVER MODULE. After processing the signal, the transceiver sends the latter to the radio cell of destination.
The radio cell of destination in turn re-elaborates the received signals, and transmits it again in the form of an electromagnetic wave to the mobile phone of the person you want to talk to. At this stage, the signal undergoes the inverse process, so the wave containing the information of your voice is converted into an electrical signal, and subsequently into sound. So your voice can now be heard by the receiver.
We can therefore say that the mobile communication network is not only wireless, but also uses LANDLINE TECHNOLOGY too, to transfer the call from your phone to the recipient’s phone.
But how does your cell tower knows what is the exact location of the cell tower of the recipient of your call? Thanks to the Mobile Switching Center.
The Mobile Switching Center is nothing but a telephone switching center for mobile radio users and can simply be defined as the electronic evolution of the switchboard, in which the operator manually patched through the calls to the right recipients.
The MSC therefore represents the central point for a group of cell towers, since inside, it contains all the information stored in the sim card of a group of telephone users.
So the MSC that recorded the information of your sim card in its database, is called HOME MSC. This information can be: the serial number of the sim, the LOCATION AREA IDENTIFIER, that is the last visited geographical area, but also the service plan, the PIN code, but above all: the TELEPHONE NUMBER.
If you travel outside the geographical area covered by your HOME MSC, a new MSC will handle your calls, communicating with your HOME MSC, that will always know your cell location, and therefore will correctly direct your incoming calls to your phone.
A technique of your MSC to know exactly your geographical area is to periodically update information on your position. This updates take place whenever you’re moving through a certain number of cell towers.
To better understand these dynamics we can take the example of a typical call made by a plant technician who wants to contact JAES to have a direct feedback on the supply of an industrial spare part, that should be replaced in the plant as soon as possible.
When the technician dials the mobile phone number of JAES on his phone, the call request arrives at his HOME MSC. His HOME MSC, in turn, provides to send the request to JAES HOME MSC.
Now, JAES HOME MSC checks what is the current JAES MSC, to see if the jaes operators are in the central office or if they are engaged in other plants.
Luckily, the operator who answers the call, is always present at the JAES headquarters and he can immediately answer the call.
If JAES operator is out of the office, JAES HOME MSC simply sends the call request to the MSC of the corresponding geographical area.
When we talk about mobile communication we need to talk about the ELECTROMAGNETIC SPECTRUM, that is the set of all the possible frequencies of the electromagnetic radiations, necessary to transfer the zeros and ones, mentioned at the beginning of this video.
Users are in fact in a certain RANGE OF FREQUENCY, which means that their phone devices have a specific BANDWIDTH, that is different from all the others. But if we look at the billions of mobile phone owners around the word, we can notice that the frequency spectrum available is quite limited.
For this purpose, many bandwidth are carefully distributed in different cell towers, so as to be distributed among the active users, in that specific geographical area.
Mobile communication has significantly evolved in just a few decades, during which different generations of mobile phone technologies, as well as new telecommunications standards have come and gone.
The first generation systems, which appeared in the 1980s under the name 1G, has allowed us to have a completely wireless phone. The problem with these phones was that they could only transmit analog signal and could only handle voice calls.
The analog signal can easily be altered from external sources, therefore, the quality of the communication offered by the first generation of mobile phones, which were very voluminous devices, presented many issues, such as the poor audio quality and the frequent interruptions.
In order to improve transmission quality, system capacity and signal coverage, the second generation of 2G mobile networks has marked a breaking point with the previous technology, focusing on the digital switchover, introduced by the GSM standard.
The use of digital technology marked the birth of the first data transmission services, in the form of Text Messaging Service SMS, MMS and Wireless Application Protocol, which is the standard that allowed us to access, for the first time, to special web contents from our mobile phones.
The 3G technology introduced in the early 2000s, allowed to offer a further speeding up of data transfer thanks to the introduction of the W-CDMA protocol, which stands for “Wideband Code Division Multiple Access” and is a particular technology that increases data transmission rates in GSM systems by using the CDMA air interface instead of TDMA, that stands for “Time Division Multiple Access”.
A further increase in bandwidth has allowed the 3G phones to have a data transmission speed of 2 megabits per second, useful for sending and receiving GPS signals, videos and voice calls.
3G technology actually marks the transition from the common mobile phone to the current smartphone.
The acronym 4G identifies the fourth and current generation of mobile telephone services. This technology allows smartphones to have data rates from 20 to 100 megabits per second, suitable for television and high-resolution movies.
The feature of the next 5G generation that will differentiate it from previous communication standards, is its connection speed. The 5G in fact should be between 100 and 1000 times faster than the 4G.
The 5G in fact will take advantage of the millimeter wave, which is the band of spectrum between 30 gigahertz and 300 gigahertz, the highest possible frequency spectrum.
5G will represent the communicative standard designed for the Internet of Things and Home Automation.