Time Division Multiplexing

An alternative to FDM is TDM (Time Division Multiplexing). Here, the users take turns (in a round-robin fashion), each one periodically getting the entire bandwidth for a little burst of time.Bits from each input stream are taken in a fixed time slot and output to the aggregate stream. This stream runs at the sum rate of the individual streams. For this to work, the streams must be synchronized in time. Small intervals of guard time analogous to a frequency guard band may be added to accommodate small timing variations.

Time Division Multiplexing (TDM).

TDM is used widely as part of the telephone and cellular networks. To avoid one point of confusion, let us be clear that it is quite different from the alternative STDM (Statistical Time Division Multiplexing). The prefix ‘‘statistical’’ is added to indicate that the individual streams contribute to the multiplexed stream not on a fixed schedule, but according to the statistics of their demand. STDM is packet switching by another name.