Multiplexing
Using the technique of multiplexing we
may make efficient use of bandwidth used for transmission. These days, there
are countless number of networks; large quantity of data is transferred through
them. This results in use of techniques of multiplexing. Multiplexing can be of
following types: Frequency division multiplexing, Wavelength division
multiplexing, and Time division multiplexing.
Frequency division multiplexing
Frequency division multiplexing is an
analog technique. Analog in the sense because frequency of component analog
signals is multiplexed to form one composite signal for transmission. A source
generating component signals, generates them in a similar frequency range. The
signals have their own component carrier frequencies. The modulated signals
(source signal with its carrier wave) are multiplexed inside a device named
multiplexer to get the composite signal. Similarly, this composite signal is
de-multiplexed by the device named de-multiplexer. FM radio broadcasting is
done using frequency division multiplexing.
Wavelength division multiplexing
Wavelength division multiplexing is
also an analog technique. Optical signals are multiplexed using WDM. An optical
signal has a high value of frequency; since value of frequency increases, the
value of wavelength becomes less and such that it is better to multiplex
signals based on the values of wavelength.
Time division multiplexing
Time division multiplexing is a digital
technique. It combines components according to their time slots. If in diagram
both A and B would be sending 2 packets in 1 second on single line, they tend
to become 4 packets sent through one line in 1 second. There are two types of
time division multiplexing: synchronous TDM and statistical TDM. In synchronous
TDM each input time slot has a reserved time slot in composite signal. Whereas
in statistical TDM these time slots are allocated dynamically, and thus
bandwidth efficiency is increased.
