communication involves implicitly the transmission of information from one point to another through a succession of processes . Digital communication is a mode of communication. It occurs when the information or the thought is encoded digitally as discreet signals and then is electronically transferred to the recipients. Digital communication is most commonly used mode of communication nowadays . It is a quick way to communicate , information can reach the recipient within a fraction of seconds. As a single individual is capable of doing digital communication , hence it requires less manpower and is a cheap mode of communication. Building blocks of digital communication are : 1 Input source and input transducer :- source of information can be analog or digital. 2 Source encoder : signal produced by source is converted into digital signal including ‘0’ and ‘1’. 3 Source encoding and data compression: the process of efficiently converting the output of analog and digital source into a sequence of binary digits is known as source encoding. 4 Channel encoder : the information sequence is passed through the channel encoder. 5 Digital modulator : the binary sequence is passed to digital modulator which in turn convert the signal into electric signal so that we can transmit them on channel ,it processes the channel corrupted transmitted waveform and reduces the waveform to sequence of number that represents estimates of transmitted data symbols. 6 Channel decoder : the sequence of numbers then passed through the channel decoder which attempts to reconstruct the original information sequence from the knowledge of code used by the channel encoder and the redundancy contained in the received data. Channel of digital communication, the modulation and coding used in digital communication system depend on characteristics of channel . The two main characteristics of channel are BANDWIDTH and POWER. In addition the other characteristics are whether the channel is linear and nonlinear , and how free is the channel from external interference. Five channels considered in digital communication : telephone channel, coaxial cables, optical fiber , microwave radio and satellite channel. Mina factors of degradation of signal in digital communication : loss in signal to noise ratio, signal distortion caused inter signal interference , distance.
works at ISRO
Dr APJ Abdul Kalam Technical University
Gyan Ganga Institute of technology and sciences jabalpur
Delhi Technological University