Mul-ti-plex [m´ulte pl`eks] n (plural mul-ti-plex-es)
electronic engineering multiple transmission: the simultaneous transmission
of two or more signals along one communications channel
(Microsoft Encarta Reference Library, 2004) [3].
‘Multiplexers (MUXs) act as both concentrators and contention devices to allow multiple, relatively low-speed terminal devices to share a single, highcapacity circuit (physical path) between two points in a network. ‘ (Horak 1996) [2]. Multiplexing is sending multiple signals or streams of information on a carrier at the same time in the form of a single, complex signal and then recovering the separate signals at the receiving end. (Whatis.com 2004) [4].
MUX exists in both end-point. At one point, it combines several circuits, usually a set of four or multiples of four into one high-capacity circuit and the other end-point is to split them back into several circuits. By putting the wire all together in a single high-capacity line, multiple communications can now be achieved. Multiplexing can be implemented in current transmission media such as twisted pair, coaxial, fiber optic cables, microwave, satellite and radio systems.
The main advantage to use multiplexing is for economic reason. (Horak 1996) [2]. Imagine that without using multiplexer shown in Figure 1, each computer will need its own dedicated physical connection which can cost more rather than combining several circuit into one.
Multiplexing works in a such way that the hosts will not experience what is happening in between. It is MUX job to craft the electric signal and put it into one high-capacity circuit. On another end, other MUX will examine the signal and forward it to a designated host.
As the technology of transmission medium is constanly advancing time to achieve faster delivery and bigger amount of data that can be carried, Multiplexing evolves as well to take advantages of newer technology.
Figure 1: Multiplexed Circuit
Nowadays, there are several methods to carry data in a multiplexed environment. This article will describe the varieties of multiplexing technology based on a chronological order. These methods are Frequency Division Multiplexing, Time Division Multiplexing, and Statistical Division Multiplexing.