A Communication system and its limitations

Communication System: 

Communication system is the system designed to transmit information. The components of a communication system are as follows:-

Fig: Block diagram of a general communication system

Source: The source originates a message such as human voice. If  the message is nonelectrical, it must be converted by an input transducer into an electrical waveform referred to as the baseband signal or message signal.  

Transmitter: The transmitter modifies the baseband signal for efficient transmission.

Channel: The channel is a medium such as wire, co-axial cable, waveguide, optical fiber or a radio link through  which the transmitter output is sent.

 

Receiver: The receiver reprocesses the signal received from the channel by undoing the signal modifications made at the transmitter and the channel. The receiver output is fed to the output transducer which converts the electrical signal to its original form- the message. 

Destination: The destination is the unit to which the message is communicated.

Limitations of a Communication System: 

In a communication system the efficient transmission depends on bandwidth of the channel, signal power and instrumental requirements. Shanon’s shows that the rate of transmission without error is given as     

           C = B log₂ ( 1 + SNR )       bit/s

Where  B = channel bandwidth,   SNR = signal to noise ratio = signal power / noise power

Bandwidth of a channel is the range of frequencies that it can transmit with reasonable fidelity. So the increase in bandwidth means the increase in number of frequencies. As a result the transmission speed also increase. 

SNR is defined as the ratio of signal power to noise power. As we have no control on noise, increasing the signal power we able to increase SNR. That means reducing the noise effect.

But we can’t increase the signal power and channel bandwidth unlimitedly. Because they are exchangeable. Which describes that increase in bandwidth causes decrease in signal power and vice versa.

From shanon equation we see that if there is no error/noise signal, the rate of transmission will be infinite. Physical meaning of this is that we will able to transmit the signal in any distance without error or loss of energy. In practical, establishing such a system and generation of wave have some difficulties. Therefore we have some fundamental limitations in our communication system.

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