Electronic Communication, Electronics

Difference Between TDM and FDM

In this article we will learn what are the difference between TDM and FDM. We will start with the basics and we will see each of the differences between them.

In telecommunication, Multiplexing is the process of sending two or more individual signals over a single communication channel this is usually achieved by an electronic circuit known as multiplexer.

In telecommunication, the two most common type of multiplexing technique are TDM and FDM.Both have their own advantages and uses, in this article we will cover all Differences between TDM and FDM.


Difference Between TDM and FDM (With Comparison Chart)

Definition TDM is the transmission technique in which different signal are transmitted over a common channel and each signal occupies entire range of bandwidth in the time domain.FDM is the transmission technique in which different signal are transmitted over a common channel and each signal occupies different slot within that bandwidth of the frequency domain.
Stands ForTDM means Time-Division MultiplexingFDM means Frequency-Division Multiplexing
Useful forTDM can be used for both Analog and Digital signals.FDM can be used for Analog signals only.
SynchronizationTDM requires Synchronization.FDM does not requires Synchronization.
CircuitTDM circuitry is very simple to built.FDM circuitry is very complex.
Cross TalkTDM is not sensitive for Cross Talk (Noise Immunity)FDM suffers from the cross talk immunity due to Bandpass Filter.
RequirementTDM requires sync pulse for its operation.FDM requires Guard bands for its operation.
EffiecientTDM is more efficient and is widely used technique in multiplexing.FDM is less efficient compared to TDM.
ApplicationsTDM is used in Pulse code modulation.FDM is used in TV and RADIO broadcasting.

What is TDM:

Time-division multiplexing (TDM) is a method of transmitting and receiving multiple signals over a single channel; each signal occupies entire bandwidth of the channel. However, each signal is transmitted for a short period of time or in other words, each signal is allowed to use a channel for a fixed time.

One of the major difference is that TDM can be used for both digital and analog signals.

Figure down below shows the concept of Time-Division Multiplexing:

TDM (Time-division Multiplexing)


What Is FDM:

Frequency-division multiplexing (FDM) is a method of transmitting and receiving multiple signals over a single channel, each signal being allocated a portion of the spectrum within that bandwidth. FDM can be used for analog signals only. FDM technique is most widely used technique in multiplexing.

The most common example of FDM is TV and RADIO broadcasting, in which number of RADIO signals at different frequencies are passed through the air at the same time.

Another good example is cable TV, in cable Television different television channels are carried at the same time on a single cable.

Figure down below shows the concept of Frequency-Division Multiplexing:

Differece between TDM and FDM


Key Differences

  1. FDM divides the channel bandwidth into smaller frequency ranges so each user can transmit data simultaneously through a common channel, while TDM allocate a fixed time for each user for the transmission of data over a common channel.
  2. FDM uses Analog transmission system
  3. TDM uses both analog and digital transmission system.
  4. In FDM Synchronization is not required between Signals and multiplexer Circuit.
  5. In TDM synchronization is required between signals.
  6. FDM provides less flexibility compared to TDM.
  7. FDM circuitry is more complex than TDM circuitry.
  8. TDM is employed in Pulse-Code-Modulation transmission.
  9. FDM is employed in Telemetry systems, RADIO and TV broadcasting.
  10. FDM suffers more Cross talk issue compared to TDM.



Both FDM And TDM are the techniques of multiplexing, the only difference between TDM and FDA is that in FDM, individual signals for transmission are given a different frequency within a common bandwidth. In TDM, the multiple signals are transmitted in different time slots on a single channel.

Also FDM is used for analog transmission of signals for example transmission of Audio signal at RADIO is achieve by FDM. Whereas TDM can be used for both analog and digital signals in computer based communications TDM is widely used, However in terms of their efficiency TDM has much greater efficiency than FDM.

Source of images: Multiplexing and spreading

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