General Block Diagram of a Communication System

Definition of Communication Communication 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.

Source Info. Transmitter Transmitted signal User Received signal Receiver Received info. Noise Channel General Block Diagram of a Communication System

Source Info. 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 Source Info. 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