Difference between Analog and Digital Communication

Depending on the type of signals used to transmit data or information, the communication system can be divided into two categories – analog communication system and digital communication system. In this article, we are going to discuss what is the difference between analog and digital communication systems.

Difference between Analog and Digital Communication in tabular form

In the following table, we have pointed out the differences between analog and digital communication.

Analog Communication Digital Communication
The communication system that uses analog signals to transmit the data or information is called an analog communication system. The communication system that uses digital signals to transmit the data or information is called a digital communication system.
The Analog communication system is less immune to noise. The digital communication system has higher noise immunity.
Modulation schemes used for analog communication systems are – Amplitude Modulation (AM), Frequency Modulation (FM), Phase Modulation (PM), etc. Modulation schemes used for digital communication systems are – Amplitude Shift Keying (ASK), Frequency Shift Keying (FSK), Phase Shift Keying (PSK), etc.
Analog communication systems do not require Analog-to-Digital Converter or Digital-to-Analog Converter. Digital communication system requires both ADC and DAC as most of the natural signals are analog signals.
The analog communication system is less complex in nature and easier to implement. The digital communication system is more complex in nature and harder to implement.
As an analog communication system is easy to implement, it also costs less. As a digital communication system has a complex structure, it costs more.

What is Analog Communication System?

The communication system which uses analog signals to transfer data is called an analog communication system. We have given the basic block diagram of the analog communication system below. Here we have not considered noise and distortion.

analog communication system

In an analog communication system, first, we take the raw message from the source. This signal is called an input signal. This message is generally an analog signal i.e., this signal’s amplitude has continuum values. Examples of such messages are – voice signals, sound signals, etc. If this input signal is not an electrical signal i.e., the human voice, then this signal is converted into an electrical signal using an input transducer. This signal is called a message signal or baseband signal. We can use this electrical signal to transfer the message signal over a channel or wirelessly.

Depending on the mode of transmission we need to modulate the signal with a signal of higher frequency. There are two specific types of technique for modulation – Amplitude Modulation (AM) and Angle Modulation. Angle Modulation is further divided into two types that are – Frequency Modulation (FM) and Phase Modulation (PM). The transmitter consists of a modulator and may consist of other units. The function of the transmitter is to transmit the signal into the channel. The channel can be any physical media such as coaxial cable, twisted pair cable, optical fiber, or wireless radio link.

The receiver collects the signal from the channel and demodulates it. A receiver consists of a demodulator, and many consist of other units. Then the demodulated signal is passed to the output transducer which converts the electrical signal back into its original form. And we get the original message signal at the output.

What is Digital Communication System?

The communication system that uses digital signals to transfer data from source to destination is called a digital communication system. The basic block diagram of the digital communication system is given below.

Digital Communication System

In a digital communication system, first, we get the message from the source. If it is not an electrical signal, then it is converted into one using a transducer. This signal can be either a digital signal or an analog signal. Next, we have a source encoder that converts this signal into a binary signal. It encodes the signal using the minimum number of bits. Then we have the channel encoder. It plays a great role to reduce the effects of noise and distortion caused by the channel. It adds some additional patterns of bits so that we can detect the original message more precisely at the receiver.

The next unit we have is a transmitter. It consists of a modulator and other units. It modulates the binary signal with a high-frequency signal. The modulation schemes for digital signals are different from that of analog signals. Modulation schemes used in the digital communication system are – Amplitude Shift Keying (ASK), Frequency Shift Keying (FSK), and Phase Shift Keying (PSK).

The receiver consists of a demodulator and other units. It demodulates the signal and sends it to the channel decoder. This eliminates the redundancy in the signal which was introduced by the channel encoder. The next source decoder decodes the signal and the output transducer converts the signal into its original form which we get at the output.

Conclusion

Analog and digital communication systems coexist in the modern communication system. Digital communication system offers many advantages over the analog communication system. This is why most of the systems we can find are digital such as – computer network, e-mail, text messaging, etc. But analog communication system also has some application such as FM radio, video and audio transmission of television, etc.

Author
Subhrajyoti Choudhury

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