Digital communication

Digital communication 

A digital communication system consists of six basic blocks. The functional blocks at the transmitter are responsible for processing the input message, encoding, modulating, and transmitting over the communication channel.

• In this diagram three basic signal processing operations have been included. They are:

  1.Source coding:

  • In source coding the encoder converts the digital signal generated at the source output into another signal in digital form.

  • Different source coding techniques are PCM (Pulse code modulation) DM(Delta modulation).

  2.Channel coding:

  • Channel encoding is done to minimize the effect of channel noise.

  • This will reduce the number of errors in the received data and will make the system more reliable.

  3.Modulation:

  • Modulation is used for providing an efficient transmission of the signal over the channel.

  • The detector is used for demodulation channel decoder and source decoder has exactly the opposite roles to play as compared to the channel encoder and source encoder respectively.

• If the information rate is maximum Digital modulation technique can be used because due to the digital nature of the signal, it is possible to use the advanced processing techniques such as digital signal processing, image processing, and data compression

Advantages:

1. The digital communication systems are simpler and cheaper compared to analog communication systems because of the advances made in the IC technologies.
2. In digital communication, the speech, video and other data may be merged and transmitted over a common channel using multiplexing.
3. Using data encryption, only permitted receivers may be allowed to detect the transmitted data. This property is of its most importance in military applications.
4. Since the transmission is digital and the channel encoding is used, therefore the noise does not accumulate from repeater to repeater in long distance communications.
5. Since the transmitted signal is digital in nature, therefore, a large amount of noise interference may be tolerated.
6. Since in digital communication, channel coding is used, therefore, the errors may be detected and corrected in the receivers.
7. Digital communication is adaptive to other advanced branches of data processing such as digital signal processing, image processing and data compression, etc.

Disadvantages

1. Due to analog to digital conversion, the data rate becomes high. therefore more transmission bandwidth is required for digital communication.
2. Digital communication needs synchronization in case of synchronous modulation.