Time division multiplexing (TDM) is a technique of multiplexing, where the users are allowed the total available bandwidth on time sharing basis. Here the time domain is divided into several recurrent slots of fixed length, and each signal is allotted a time slot on a round-robin basis.

Concept and Process

In TDM, the data flow of each input stream is divided into units. One unit may be 1 bit, 1 byte, or a block of few bytes. Each input unit is allotted an input time slot. One input unit corresponds to one output unit and is allotted an output time slot. During transmission, one unit of each of the input streams is allotted one-time slot, periodically, in a sequence, on a rotational basis. This system is popularly called round-robin system.

Uses and Applications:
It is widely used in telephone and cellular networks.

Types of TDM:

i) Synchronous TDM
ii) Asynchronous or Statistical TDM

 Synchronous TDM:
In Synchronous TDM, the input is connected to a frame. If there are ‘n’ number of connections, then the frame is divided into ‘n’ time slots. One slot is allocated for each input line.

Statistical TDM:
In STDM, the time slots are dynamically allocated to the slots according to demand. The multiplexer checks each input stream in a round – robin manner and allocates a slot to an input line only if data is present there, otherwise, it skips to the next stream and checks it.