Digital Transmission

The fundamental transmission concept is to transmit the minimum possible frequency or the bandwidth with maximum possible number of channels or the bit rate.

When we consider the analog transmission we can’t transmit much distance than digital transmission. Therefore we need to use small bandwidth. Using that small bandwidth can transmit much distance. Therefore we use modulation techniques to reduce the bandwidth. FDM multiplexing system is combining number of channels to convey over common transmission medium. Major advantage of analogue transmission is occupied band width is low When we use frequency modulation in low pass filter there are two, out come upper side bandwidth and lower side bandwidth. By choosing the lower side bandwidth we can reduce bandwidth of the signal.

In digital transmission we can have more than solutions compare to analog.

Theoretically we know Nyquist Theorem, it tells us relationship between bandwidth and channel capacity.

                             C = 2Blog₂M

C- Channel capacity   ,    B – Bandwidth       ,    M – signal levels 

If we want increase channel capacity for a value of bandwidth need to increase signal levels.

In digital transmission we can use time division multiplexing (TDM).using this technique we can reduce bandwidth. In this TDM large numbers of channels are put into one line and transmit. . In the digital transmission can use the available bandwidth of the channel much more efficiently as compared to analogue system.