Telecommunication is the transmission of data by various types of technologies over wire, radio, optical or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that feasible with the human voice, but with an identical scale of expediency; thus, slow systems (such as postal mail) are excluded from the sector.
Transmission media in telecommunication
The transmission media in telecommunication have evolved through numerous stages of technology, from beacons and other visual signals to electrical charge, electromagnetic radiation and light. These transmission paths are divided into communication channels, which afford the benefits of multiplexing multiple concurrent communication sessions. Telecommunication is usually used in its plural form, because it involves various technologies.
How does a mobile phone work?
Now a day, a mobile phone is a part of our lives. But I’m sure our curious minds have always been struck by such questions as how our voice transmit from one place to another using phone call, and why there are different generations of mobile communications? Let’s explore the technology behind mobile communications.
When we speak on our phone, our voice is picked up by our phone’s microphone. The microphone turns our voice into a digital signal with the help of MEMS sensor and IC. The digital signal contains our voice in the form of 0s and 1s. An antenna inside the phone receives these 0s and 1s and transmits them in the form of electromagnetic waves.
Electromagnetic waves transmit the 0s and 1s by altering the wave characteristics, such as the amplitude, frequency, phase, or combinations of these. For examples, in the case of frequency, 0 and 1 are transmitted by using low and high frequencies respectively. So, if we could find a way to transmit these electromagnetic waves to our friend’s phone, we would be able to establish a call.
Problems in Telecommunication
Electromagnetic waves are incapable of traveling long distances. They lose their strength due to the presence of physical objects, electrical equipment, and some other environmental factors. In fact, if there were no such issues, still electromagnetic waves would not carry on forever, due to the Earth’s curved structure.
To avoid these issues, cell towers were introduced, using the concept of cellular technology. In cellular technology, a geographical area is divided into hexagonal cells with each cell having its own tower and frequency slot. Generally, these cell towers are connected through wires, or more specifically, optical fibre cables. These optical fibre cables are laid under the ground or the ocean, to provide national or international connectivity.
The electromagnetic waves produced by our phone are picked up by the tower in our cell and convert them into high frequency light pulses. These light pulses are carried to the base transceiver box, located at the base of the tower for further signal processing, after processing; our voice signal is routed towards the destination tower.
After receiving those pulses, the destination tower radiates it outwards in the form of electromagnetic waves, and then our friend’s phone receives the signal. This signal undergoes a reverse process, and our friend hears our voice. So, it’s true that mobile communications aren’t entirely wireless; they do use a wired medium too. This is how mobile communications are carried out.
However, there was a big issue that we intentionally left unanswered. Mobile communication is only successful when our tower transfers the signal to our friend’s tower. But how does our tower know in which cell tower area our friend is located? For this process, the cell tower gets help from a mobile switching center. The MSC is the central point of a group of cell towers.
What does it mean by MSC in Telecommunication?
When we purchase a SIM card, all the subscription information is registered in a specified MSC. This MSC will be our home MSC. The home MSC stores information such as service plans, our current location, and our activity status. If we move outside the range of our home MSC, the new MSC, which serves us instead, is known as a foreign MSC. As we enter a foreign MSC region, it communicates with our home MSC. In short, our home MSC always knows which MSC area we are in.
To know in which cell location the subscriber is within the MSE area, the MSC uses a few techniques. One way is to update the subscriber’s location after a certain period. When the phone crosses a predefined number of cell towers, the location update is again get updated. The last one of these is when the phone is turned on. Let’s try to understand all of these procedures with an example.
Suppose, Zunu wants to call Ram. When Zunu dials Ram’s number, the call request arrives at Zunu’s home MSC. Upon receiving Ram’s number, the request will be forwarded to Ram’s home MSC. Now, Ram’s MSC checks for his current MSC. If Ram is in his home MSC, the call requests will be immediately sent to his current cell location, and it checks whether Ram is engaged on another call, or if his mobile is switched off. If everything is positive, Ram’s phone rings, and the call will be connected. However, if Ram is not in his home MSC, Ram’s home MSC simply forwards the call request to the foreign MSC.
The foreign MSC will follow the previously explained procedure to locate Ram’s phone, and will then establish the call. Now, the question comes in mind is why the frequency spectrum is quite important in mobile phone communications. To transfer 0s and 1s in digital communication, each subscriber is allocated a frequency range.
However, the frequency spectrum available for cellular communications is quite limited, and there are billions of subscribers who are trying to gain access to it. This issue is solved with the help of two technologies, one is frequency slot distribution, and another is multiple access technique. In the frequency slot distribution technique, different frequency slots are allocated to different cell towers very carefully. In the multiple access technique, this frequency slot is efficiently distributed among all the active users in that particular cell area.
Also read : What is Internet and how it works?
Different generations of mobile phone technology.
1G (First Generation)
1G originally allowed user, for the first time, to carry a phone without a cable attached to it. But 1G suffered from two various problems. The major problem was that the wireless transmission was in an analog format. Because analog signals that are easily altered by external sources. So, it provided poor voice quality and poor security also. Then another problem was that it used the frequency division multiple access technique, which used the available spectrum in an inefficient way. These factors paved the way for the second generation of mobile communications.
2G (Second Generation)
2G used digital multiple access technologies, namely TDMA (Time Division Multiple Access), or CDMA (Code-division Multiple Access) technology. The second generation introduced a revolutionary data service, SMS (Short Message Services), and internet browsing also.
3G (Third Generation)
3G technology was focused on giving a higher data transfer speed which was the demand of time. It used a WCD (Wireless Collision Detect) multiple access technique, along with an increase in bandwidth. To achieve this, the 3G speed of two Mbps allowed the transfer of data for uses such as GPS (Global Positioning System), videos, voice calls, et cetera. 3G was a huge step in the transformation of the basic phone to a smartphone.
4G (Fourth Generation)
Next came 4G, which is the fourth generation of broadband cellular network technology, succeeding 3G. It achieved speeds of 20 to 100 Mbps. This was suitable for high resolution movies, television and other different media. This higher speed was made possible due to the OFD (Orthogonal Frequency-division) multiple access technology, and MIMO (Multiple Input Multiple Output) technology. MIMO uses multiple transmitter receiver antennas inside both the mobile phone and the towers.
5G (Fifth Generation)
The next generation of mobile communication is 5G, which is to be rolled out soon, will use enhanced MIMO technology and millimetre waves. It will be faster and able to handle lots of devices. It will provide seamless connectivity to support the internet of things, such as driver less cars and other technical devices.