Explain the Time Division Multiplexing (TDM)

The Time Division Multiplexing (TDM) is a digital procedure. Here, each sender is given the entire possession of the whole bandwidth of the channel for a fixed duration of time. After this, the control is moved to the next sender, and the process continues on a round-robin basis.

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


The following variants on TDM are as follows −

  • ATDM (Asynchronous Time Division Multiplexing): Multiplexing in which the data is transmitted asynchronously.

  • STDM (Statistical Time Division Multiplexing): A multiplexing method that polls nodes and immediately skips any nodes with nothing to send.

  • STM (Synchronous Transfer Node): Designer for use in BISDN (broadband ISDN) and also supported in the SONET (Asynchronous Optical Network) architecture.


There are two types of TDM which are as follows −

Synchronous TDM

Synchronous TDM is known as synchronous and is essential because, each time slot is pre-assigned to a constant source. The time slots are sent irrespective of whether the sources have a few records to share or not.

TDM devices can manage the source of various data rates. This is completed by authorising fewer slots per cycle to the passive input devices than the rapid device.

Both multiplexing and demultiplexing operations for synchronous TDM, are demonstrated in the figure given below.

Statistical TDM 

One disadvantage of the TDM method is that some of the time slots in the frame are wasted. A specific terminal has no information to send to a particular instant of time and will share an unfilled time slot. It is also called asynchronous TDM or intelligent TDM.