Multiplexing is the process of transmitting several different signals or information streams via a single carrier. The transmission of all these signals or streams takes place simultaneously by combining the several signals into one common signal that will efficiently moves through the carrier bandwidth. Once the signal reaches the destination point for one of the transmissions, that integrated signal re-assimilates into its original form and is received.
The exact configuration of the process depends a great deal on the mode or type of transmission. When dealing with an analog transmission, the signals are multiplexed using a process that is known as frequency-based multiplexing. This form, usually referred to as FDM, uses a process of dividing the bandwidth into a series of subchannels that will accommodate the transmissions and more or less allow them to flow forward in a parallel fashion.
A second common type is time-division multiplexing, or TDM. With TDM, the various signals or transmissions are carried over a common channel in much the same way as with FDM. The main difference is that the time-division approach allows for the signals to be transmitted in a series of alternating time slots. These alternating slots are still carried within a common channel, and still fit neatly into the available bandwidth.
Multiplexing is one of the common tools used today in just about every form of communications. A wide range of telephony services, including online applications, are able to function with such a high degree of efficiency because of the current technological advances this process has made possible. Optical networks also rely heavily on multiplexing to carry voice and video transmissions along concurrent but separate wavelengths from a point of origin to various points of determination. With an increasing range of communication functions taking place across the Internet, it has become an effective tool that aids in everything from videoconferences and web conferences to large data transmissions to even making a simple point-to-point telephone call.