A telecommunication system is an integral part of our daily life. It actually able us to make long-distance communication. Now if we talk about long-distance communication there especially two kinds of communication analog and digital communication. However, there can be other kinds of communication also like microwave communication, satellite communication, optical communication, etc.
History of Telecommunication
In old days especially digital has not come into the field in that much manner we have used analog communication in a large manner. But with the evolving digital era, we are more focusing on digital technology. In analog and digital communication, the main difference is the type of message signal. In analog communication, we are using analog signals but in digital communication, we are using digital signals. In analog communication, we have to actually use some regenerative repeater that will actually reconstruct the signal. Here we have two kinds of communication band-pass and baseband communication. the square wave signal which we have to send for long-distance communication contains a significant low-frequency signal. As we know frequency is inversely proportional to wavelength, so in that case antenna size is very much high but this much large size of the antenna is not physically realizable. So here modulation comes in to picture . Here using a high-frequency carrier signal we can actually shift the frequency of the resultant signal to a high frequency and thus it makes long-distance communication possible.
Communication in Old Era
In the old era when we have used wire communication but with the growth of technology wireless communication comes in to picture. Previously we use landline phones but now with the development of technologies, we are using mobile phones. Previously we are sending only voice signals but now based on the evolving technology, now we are not only sending voice but also sending a huge amount of data. In telecommunication systems another important thing multiplexing.When we have to send several message signals through a single channel. We can do it either by TDM or by FDM.
In TDM we are taking the sample value of the different signals at a different instance of time and in FDM we are allocating a particular frequency band for a particular source of the signal. In ancient days also communication is done by sending letters by pigeons or by sending signals in case of emergency situations by the smoke or fire. But with the evolving technology wireless communication is developed. Now with the help of the internet, we can connect to the rest of the world very easily. Previously we can only do voice calls but nowadays we can do voice calls as well as video calls.
Noise in Communication
An important concept in communication is noise. There can be many types of noises. Noise holds a disturbance to the main signal. Like in the bad weather we feel the disturbance in the calls. Now comes the question of why ac is used in telecommunication. So DC signal is a signal whose value is constant with respect to time and an AC signal is a signal whose value is changing with respect to time. The ac signal can be a sinusoidal signal, square signal, or any signal that is time-varying. Now if we use an ac signal it actually imposes some disturbance or noise to the power line. In the ac signal, we can see fluctuation in current that can affect the solid-state devices. The noise problem after using the ac signal to the line is more prominent in analog communication.
DC in Telecommunication
DC power is a stable source of backup for a telecommunication system. Most of the signals which we have sent are basically time-varying. So to discard the noise several filtering techniques are used and to avoid the aliasing effect anti-aliasing filtering is used then using demodulation we are getting the demodulated signal. Then using the low pass filter we can actually retrieve the message signal. Sometimes to maintain the security of the message signal several some times several types of encryption technology are used. In that case, the receiver also should be very much aware of which kind of encryption technology is used in the transmitter end.
Finally, we can say in the modern era modern telecommunication is an integral part of our life. In this online age, we are very much dependent upon virtual communication modes. In this era, along with voice communication, data communication like messaging and video communication like video conference calls also play an important role