Introduction to Digital Communication

With the development of electronics engineering, a need was felt to introduce a system that would help in the transfer of analog signals efficiently by converting them to digital form. This domain of electronics engineering is known as digital communication. In this article, we will study what Digital Communication is and what components make up Digital Communication.

Later, we will study the classification system in Digital Communication and the characteristics of this system. We will also study Digital Communication systems' advantages, disadvantages, and applications. The article concludes with some frequently asked questions for readers.

What is Digital communication?

Digital Communication is a branch of electronics that deals with the transmission of data in digital format. The transmission of these signals is needed mainly because they are present in analogue format. A basic digital communication system that involves the transmission of signal, encoding, modulation, and decoding of signals. Let us look at the formal definition of Digital Communication

Digital Communication can be defined as a mode of communication that encodes analog data to digital form and sends it to the receiver after demodulation.

What is a Signal?

The message needs to be converted into a format that is suitable for transmission across communication channels, this codified message that encodes the message for transmission purposes is known as a signal. The signal is passed through various channels and then it is decoded at the receiver end to generate the original message. There are different types of signals and we are interested in digital signal

Digital Signal

When the signal is represented at discrete instants of time then this signal is known as discrete signal. These signals are generally used for quantities that need to be specified at specific instants of time rather than a continuous time interval. These signals can only take a certain set of values. Let us see the categorization of digital signals.

Types of Digital Signal

Digital signals can be of different types depending on the output generated by them. Here are some of them:

• Unit step signal: The unit step signal is a type of digital signal which has output value 1 for t>=0 and is 0 for rest of the intervals i.e. t<0. Here is how the Unit step signal looks like.

f(n) = 1 ; for n>=0

f(n) = 0 ; for n<0

• Unit impulse signal: Unit impulse signal is a type of digital signal which has output value 1 for t=0 and is 0 for rest of the intervals i.e. t≠0. Here is how the Unit impulse signal looks like.

δ[n]=1 for n=0

?[?]=0δ[n]=0  for n≠0

Digital Communication System

Let us study the components of Digital Communication

• Source: A source is the device that feeds the input signal into the system for processing. This can be a microphone, signal generator, or any other device capable of producing a signal.
• Transducer: The transducer is a device needed for generating electrical signals from the input signal. These electronic signals are important since data can't be transferred in any form and needs to be converted into some sort of signal.
• Source Encoder: A Source Encoder is used for encoding data by compressing it into bits that can help in reducing the bandwidth needed for transmission.
• Channel Encoder: During the transmission of data, errors are bound to get introduced therefore, a channel encoder is needed to eliminate errors due to noise. It intentionally adds some redundant bits that can be removed at the end.
• Digital Modulator: The modulation of the signal is performed by a Digital Modulator. This is necessary to convert the signal into a format that can be easily transmitted in a medium.
• Channel: This is the midway component in the system that helps to pass the signal from the transmitter end to the receiver end.
• Digital Demodulator: Once the signal has reached the receiver end, the signal needs to be converted from digital to analog form. This reconstruction of a signal is known as demodulation and is performed by the demodulator.
• Channel Decoder: Just like the channel encoder, the Channel Decoder is used for correction of errors at the receiver end. These errors are corrected using the redundant bits added.
• Source Decoder: This step is necessary to obtain a proper digitized signal therefore steps like sampling and quantizing are performed in the source decoder.
• Output Transducer: This part involves the conversion of an electronic signal into a physical form that can be perceived by the device. Loudspeakers are a type of output transducer.
• Output Signal: The final step is the collection of Output Signal that is generated after the entire process.
  

Characteristics

Let us study the characteristics of Digital Communication

Modulation

The process of encoding a signal using its amplitude, frequency, or phase is known as digital modulation. Modulation is necessary to transfer the signal efficiently in a given bandwidth. There are various modulation techniques like

• Amplitude Shift Keying: This is a modulation technique which is used for representing binary data as a variation of signal amplitude. This form of modulation shows output for high input and 0 for low input.
• Phase Shift Keying: In this form of modulation technique, the phase of carrier signal varies in proportion to digital signal. In PSK, output is high when input phase is high and low when input phase is low.
• Frequency Shift Keying: In this form of modulation technique, the frequency of carrier signal varies in proportion to digital signal. In FSK, output is high when input frequency is high and low when input frequency is low.

Multiplexing

Digital Communication can be used for transmission of multiple signals through a single channel. This helps to send multiple signals through a single cable. In digital communication, multiplexing is done by transferring data in the form of discrete bits. These are the different multiplexing techniques

• Time Division Multiplexing: This is a multiplexing technique transfers signal through a single channel by giving time slots to the signals.
• Frequency Division Multiplexing: This is a multiplexing technique transfers signal through a single channel by dividing frequency slots to the signals.
• Code Division Multiplexing: This is a multiplexing technique transfers signal through a single channel by assigning some code to the signals.

Difference Between Analog and Digital Communication

Let us study the difference between analog and digital communication

Advantages

Let us study the advantages of Digital Communication

• The speed of data transmission is quite high therefore, message transfer occurs almost instantly.
• The process of digital communication is quite efficient because speed and accuracy are always maintained in this system.
• The wireless nature of digital communication can be used to establish connections globally without major geographical constraints.
• Digital Communication has the ability to minimize bandwidth consumption by multimedia sharing using bandwidth division.
• Digital communication is a cost-effective method as compared to other forms of communication that need a central system and other stations.

Disadvantages

Let us study the disadvantages of Digital Communication

• Digital Communication lacks a personal touch due to a lack of proper interaction between users at both the ends of channel.
• Maintaining security in Digital Communication becomes a difficult task, therefore data leakage and privacy can be at major risk.
• Since Digital Communication is technology-dependent, technological errors can lead to faults in message transfer which can cause network outage.
• With an increase in network coverage, the complexity of digital communication systems increases and therefore, implementation of such circuits is difficult.
• Digital Communication involves different steps that can introduce errors in the system like sampling error which can deteriorate the signal.

Applications

Let us study the applications of Digital Communication

• Digital Communication is used for the transfer of messages all over the globe using features like Emails, instant messaging, and video conferencing.
• Electronics and communication systems make use of Digital Communication in domains like pattern detection, robotics, and image enlargement.
• Digital Communication is used in the compression of signals like video compression to save the bandwidth of transmission.
• Fields in electronics engineering like digital signal processing make the use of digital communication to understand signal processing.
• Digital Communication is used in spacecraft for space communication between space and Earth using signals.

Digital Vs Data Communication

Let us see the difference between data and digital communication

Conclusion

We have seen how Digital Communication plays a significant role in electronics and communication. We have seen the necessary components that make up the Digital Communication system. It is used in different appliances like signal processing and signal compression.

Despite, the advantages of the digital communication system there are certain limitations that have been discussed. It is important to understand the workings of digital communication systems to develop a better understanding. Readers can refer to frequently asked questions in case of any doubts.