In networking, the technique of combining separate communication channels from different sources into a single channel for transmission over a wide area network (WAN) link. For example, you can combine input from various pieces of data terminal equipment (DTE) using a multiplexer and transmit it over a single digital data line. The line must have a bandwidth equal to or greater than the combined bandwidth of the signals from the pieces of DTE.
Graphic M-23. Multiplexing.
A number of multiplexing methods are used in telecommunications and networking, each one suited to a different form of communication. Analog signals are often multiplexed using a technique called frequency-division multiplexing (FDM), in which the total bandwidth of the carrier is subdivided into a series of subchannels with different frequencies.
Digital signals are often multiplexed using a technique called time-division multiplexing (TDM), in which multiple signals are combined into a single communication channel or bitstream by alternating them in brief time slots or intervals.
Another digital multiplexing technology is statistical packet multiplexing (SPM), which is more efficient than TDM in dynamically allocating bandwidth for each multiplexed channel. A newer multiplexing technology is dense wavelength division multiplexing (DWDM), which is used in fiber-optic networks.