Explain digital communication system with the help of block diagram.
2 Answers
Answer :
Block diagram of digital communication system:-
Explanation:-
DISCRETE INFORMATION SOURCE:
The information to be transmitted originates here. These information/messages may be available in digital form or it may be available in an analog form.
If it is analog it is sampled and digitized using an A/D converter to make the final source output to be digital in form.
SOURCE ENCODER :
The source encoder therefore reduces the redundancy by performing a one to one mapping of its input bit stream in to another bit stream at its output, but with fewer digits.
Thus in a way it performs data compression.
CHANNEL ENCODER:
The channel encoder is intended to introduce controlled redundancy into the bit stream at its input in order to provide some amount of error- correction capability to the data being transmitted.
DIGITAL MODULATOR:
The physical channels are basically analog in nature; the digital modulator takes each digital binary digit at its input and maps it, in a one –to – one fashion, into a continuous waveform.
Binary ‘zero’ at its input is mapped into a continuous signal so(t) and binary ‘one’ is mapped into another continuous signal s1(t).
This is called binary modulation.
PHYSICAL CHANNEL:
The digitally modulated signal is passed on to the physical channel, which is nothing but the physical medium through which the signals are transmitted.
It may take a variety of forms- a pair of twisted wires, coaxial cable, a wave guide, a microwave radio, or an optical fiber.
THE DIGITAL DEMODULATOR:
The digital demodulator of the receiver receives the noise corrupted sequence of waveforms from the channel and by inverse mapping tries to give at its output, an estimate of the sequence of the binary digits that were available at the input of the digital modulator at the transmitting end.
THE CHANNEL DECODER:
The output sequences of digits from the digital demodulator are fed to the channel decoder. Using its knowledge of the type of coding performed by the channel encoder at the transmitting end and using the redundancy introduced by the channel encoder, it produces as its output, the output of the source coder of the transmitter with as few errors as possible.
THE SOURCE DECODER: Using its knowledge of the type of encoding performed by the source encoder of the transmitter, the source decoder of the receiver tries to reproduce at its output, a replica of the output of the digital source at the transmitting end.
Answer :
Source coding:1In source coding the source converts the digital signal generated at the source output into another signal in digital form.
Source coding is needed to reduce or eliminate redundancy for ensuring an efficient representation of the source output.
Channel coding :1 channel coding 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.
Modulation:1 Modulation is used for providing an efficient transmission of the signals over the channel. The modulator can use any of the CW digital Modulation techniques ASK,PSK and FSK.
Source coding is needed to reduce or eliminate redundancy for ensuring an efficient representation of the source output.
Channel coding :1 channel coding 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.
Modulation:1 Modulation is used for providing an efficient transmission of the signals over the channel. The modulator can use any of the CW digital Modulation techniques ASK,PSK and FSK.