Multiplexing
Group members
* Harpreet kaur
* Amandeep kaur
* Sunnia kataria
What is Multiplexing
It is the process of sending signals from two
or more different sources simultaneously
over a single communication channel.
Multiplexing is done by using a device
called multiplexer(MUX) that combines n
input lines to gernate one output line i.e
(many to one).Therefore multiplexer (MUX)
has serval inputs one output.
At the receiving end , a device
demultiplexer (DEMUX) is used that
separtes signal into its components.so
DEMUX has one input ans seval outputs.
Types of Multiplexing
• Frequency Division Multiplexing (FDM)
• Wave Division Multiplexing (WDM)
• Time Division Multiplexing (TDM)
Frequency Division Multiplexing
• It is analog technique.
• In FDM, signals of different frequencies are
combined into a single composite signal and is
transmitted on single link.
• FDM requires that the bandwidth of a link should
be greater than the combined bandwidths of various
signals to be transmitted.
• Thus each signal having different frequency from a
particular logical channel on the link and follow this
channel only.
• These channels are then separeted by the strips of
unused bandwidth called gurad band.These gurad
bands band prevent the signals from overlapping.
Frequency Division Multiplexing
• In FDM signals to be transmitted must be analog
signals. Thus digital signals need to be converted to
analog form, if they are to use FDM.
Applications of FDM
• FDM is used for FM & AM radio broadcasting.
Each AM & FM radio stations uses a different carries
frequency .
• FDM is used in television broadcasting.
• First generation cellular telephone also uses FDM.
Wave Division Multiplexing
• WDM is the analog multiplexing technique.WDM
is conceptually similar to FDM, in sense that it
combines different signals of different signals of
different frequencies into single composite signal
and transmit it on a single link.
• In WDM the different signals are optical or light
signals that are transmitted through optical
fiber.Wavelength goes up down and vice-verse.
• In WDM various waves from different sources are
combined to form composite light signal that is
transmitted across the channels to the different
receiver.
Wave Division Multiplexing
• At the receiver side, this composite light signal is
broken into different light waves by demultiplexer.
• This combines and splitting of light waves is not by
using a prism.
• One prism is used at the sender side to perform
multiplexing and another prism is used at receiver
side that perform demultiplexing.
• The basic principal behind the usage of prism is
that,the prism bends a beam of light based on the
angle of incidence and the frequency of light wave.
Applications of WDM
• WDM is used in SONET(Synchronous Optical
Network).It makes use of multiple optical fiber lines
which are multiplexed & demultiplexed.
Time Division Multiplexing
• TDM is a digital multiplexing technique.
• In TDM, the channels is not divided on the basis of
frequency but on the basic of time.
• Total time available in the channel is divided
between serveral users.
• Each time is allotted a particular a time interval
called time slot during which the data is transmitted
by that user.
• Each sending device takes control of entire
bandwidth .
Time Division Multiplexing
• There are two types of TDM
* Synchronous TDM
* Asynchronous TDM
Synchronous TDM
•Multiplexer allots the same time slot to each device
at all time either device having data or not.
• If there are n input lines then there are n slots in
one frame. Number of slots = No of input lines.
• Synchronous TDM does not give guarantee that
full capacity of link is used .
• The no of time slot in a frame is always based on
no of input devices .
• The time slots are fixed and predefined.
Asynchronous TDM
•It is also known as STATISTICAL TDM.
•Multiplexer does not allots same time slot to each
device at all time . Time slots are flexible and not
fixed.
• If there are n input lines then there are m slots
perform. m is less than n.
• Asynchronous TDM give guarantee that full
capacity of link is used .
• The no of time slot in a frame is always based on
statistical analysis of no of input devices.
• The time slots are not fixed and predefined.
Reference:
Charanjeet singh
(kalyani Publisher)