Expert: Cezar L. Palconet - 3/29/2011

Question
Hello, I was wondering if you could briefly talk to me about TDM. I don't mind what you tell me, I just want to understand this term that I have been told about. I would like to know whether TDM uses more bandwidth compared to, say pulse code modulation. Thanks!!

Answer
Hi, Jay

Time-division multiplexing (TDM) is a type of multiplexing,  in which two or more digital bit stream signals are imposed on the carrier simultaneously as sub-channels within a  communication channel occupying a particular bandwidth.

This mode are physically taking turns using the channel, referred to as time slots, since each cycles of the multiplex offers an available time slot for the other to use, The time domain is divided into several repeating  timeslots of fixed length.
TDM is used for circuit mode communication with a fixed number of channels and constant bandwidth per channel.

Bandwidth utilization distinguishes time-division multiplexing from statistical multiplexing such as packet mode communication, in that the time-slots cycles  in a fixed order. Statistical time-domain multiplexing is very similar to, but should not be considered the same as time-division multiplexing.

TDM and PCM are world apart both in technology and use, PCM is a form of modulation, applied when an analog information is converted to a digital form, and TDM is a multiplexing process, where bits of digital information are imposed on a carrier or bearer channel.

You could say that PCM is the initial stage in  a digital communication process, as digitizing analog information, and TDM is the stage where the digital information is stacked into a bearer or carrier channel.

regards.