# Differentiate between FDM and TDM in Computer Network.

## Frequency Division Multiplexing (FDM)

It is an analog method which is used when the bandwidth of a connection (in hertz) is higher than the linked bandwidth of the signals which are to be communicated.

In FDM, the signals are created by each transmitting device which modulates the multiple carrier frequencies. These modulated signals are then connected to an individual composite signal that the link can transport.

In FDM, different frequencies are combined into a single composite signal and transmitted on the channel. At the receiver end, the reverse phase is applied to get the individual frequencies back for working. The entire bandwidth of the channel is divided into logical channels, and each sending device is given with the possession of a logical channel.

## Time Division Multiplexing (TDM)

In TDM, the pulse is presented for a short period. No signal is present for most of the time between the two pulses. The pulses from other channels can occupy this free space between the pulses and this is called Time Division Multiplexing (TDM).

An example of TDM is the television broadcast. In a television serial, generally, 10 minutes serial is followed by 5 minutes advertisement. The time in which the serial is being broadcasted, the total frequency is dedicated to the serial.

The major differences between Frequency Division Multiplexing (FDM) and Time Division Multiplexing (TDM) are as follows −

FDMTDM
FDM represents Frequency-division multiplexing.TDM represents Time-division multiplexing.
In FDM, the frequency spectrum is split among the logical medium, with each user having restricted control of the frequency band.In TDM, the client turns each periodically getting the entire bandwidth for a bit of time.
It can be used with analog signals.It can be used with digital signals.
There is no framing.There is an essential requirement of framing as the data is sent through the frames.
FDM requires guard bands for channel separation to avoid interference.There is no interference between the channels.
FDM channels capacity is divided into groups, supergroup, master group and master supergroup with the bandwidth in Kilo Hz.The capacity of TDM channels is divided into T1,T2,T3,Ty and super T4in Mbps.
Examples of FDM are radio and television systems.Examples of TDM are SONET system, Integrated Services Digital Network (ISDN) channel.
FDM circuitry is very complicated.TDM circuitry is very easy to develop.
FDM undergoes cross-talk immunity because of Bandpass Filter.TDM is not perceptive for Cross Talk (Noise Immunity).