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General Block Diagram of a Communication System
Definition of CommunicationCommunication is the transmission of information from a source to a user.
This definition suggests a certain block diagram configuration for a communication system (see next slide) and introduces additional terms which will be defined as we examine the block diagram.
SourceInfo.
Transmitter
Transmitted signal
User
Received signal
Receiver
Received info.
Noise
Channel
General Block Diagram of a Communication System
General Block Diagram of a Communication System
SourceInfo.
Transmitter
Transmitted signal
User
Received signal
Receiver
Received info.
Noise
Channel
Information:
Data which the user did not possess prior to communicating with the source. This is a very important definition and is deceptively simple. The key concept is the fact that the data which the user receives was unknown to the user before the source began communicating.
General Block Diagram of a Communication System
Source:
The source is the originator of the information. The source may be a human voice, music, digital data from a computer, etc.
Source
Info.Transmitter
Transmitted signal
User
Received signal
Receiver
Received info.
Noise
Channel
General Block Diagram of a Communication System
User:
The user is the recipient of the information
Source
Info.Transmitter
Transmitted signal
User
Received signal
Receiver
Received info.
Noise
Channel
General Block Diagram of a Communication System
SourceInfo.
Transmitter
Transmitted signal
User
Received signal
Receiver
Received info.
Noise
Channel
Channel:
The channel is the physical transmission medium over which the communication is sent. It may be wires, radio airwaves, fiber optics, etc. All channels have physical limitations which will distort and attenuate the transmitted signal and which will add noise to the transmitted signal. Thus, the received signal will not be an exact duplicate of the transmitted signal.
General Block Diagram of a Communication System
Source
Info.
Transmitter
Transmitted signal
User
Received signal
Receiver
Received info.
Noise
Channel
Transmitter:
We could try to send the source output directly through the channel, but, generally speaking, the channel will add unacceptable amounts of noise and distortion to the signal. We use the transmitter to reformat and reshape the signal so that the channel will not distort it as much. After reformatting and reshaping, the transmitter may also boost the power of the signal.
General Block Diagram of a Communication System
Source
Info.Transmitter
Transmitted signal
User
Received signal
Receiver
Received info.
Noise
Channel
Receiver:
The receiver attempts to translate the received signal back into the original information sent by the source. This involves basically two steps:
1) Compensating, as best as possible, for the noise and distortion added by the channel
2) “Undoing” the shaping and formatting from the transmitter
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