3. • Multiplexing (Muxing) is a
term used in the field of
communications and
computer networking. It
generally refers to the process
and technique of
transmitting multiple analog
or digital input signals or
data streams over a single
channel. By using
multiplexing, communication
carriers can avoid
maintaining multiple lines,
therefore, operating costs
are effectively saved.
MULTIPLEXING
5. FREQUENCY DIVISION
MULTIPLEXING
Frequency Division
Multiplexing (FDM) is a
networking technique in which
multiple data signals are
combined for simultaneous
transmission via a shared
communication medium. FDM
uses a carrier signal at a
discrete frequency for each
data stream and then
combines many modulated
signals.
6. • Advantages:
• A large number of signals(channels) can be transmitted simultaneously.
• FDM does not need synchronization between its transmitter and receiver for proper operation.
• Demodulation of FDM is easy.
• Due to slow narrow band fading only a single channel gets affected.
Advantages &Disadvantages of FDM
Disadvantages:
•The communication channel must have a very large bandwidth.
•Intermodulation distortion takes place.
•Large number of modulators and filters are required.
•FDM suffers from the problem of crosstalk.
•All the FDM channels get affected due to wideband fading.
7. • Some of the importance applications of FDM are:
• Telephone systems.
• AM(amplitude modulation) and FM(frequency
modulation) radio broadcasting.
• TV broadcasting.
• First generation of cellular phones used FDM.
Applications of FDM
8. TIME DIVISION
MULTIPLEXING
• Time division multiplexing (TDM)
is a communications process that
transmits two or more streaming
digital signals over a common
channel. In TDM, incoming
signals are divided into equal
fixed-length time slots. After
multiplexing, these signals are
transmitted over a shared
medium and reassembled into
their original format after de-
multiplexing. Time slot selection
is directly proportional to overall
system efficiency.
9. • Advantages:
• Full available channel bandwidth can be utilised for each
channel
• Intermodulation distortion is absent
• TDM circuitry is not very complex
• The problem of crosstalk is not severe
Advantages and disadvantages of TDM
•Disadvantages:
•Synchronization is essential for proper operation
•Due to slow narrowband fading, all the TDM channels may get wiped out
10. • Multiplexing of digital signals
• Digital telephone
• Satellite communications
• Fiber optic communication
• Wireless communication applications
Application of TDM
11. DIFFERENCE BETWEEN FDM AND TDM
BASIS FOR COMPARISON FREQUENCY DIVISION
MULTIPLEXING
TIME DIVISION
MULTIPLEXING
BASIC Frequency is shared Time scale is shared
USED WITH Analog signal Digital and Analog signals
NECESSARY REQUIREMENTS Synchronisation not required Synchronisation required
INTERFERENCE High Low or negligible
CIRCUITARY Complex Simpler
UTILISATION Ineffective Efficiently used
12. • Crosstalk:
• It basically means interference between the adjacent TDM channels.
It is the unwanted coupling of information from one channel to the
other.
• Guard Time:
• It is time spacing introduced between the adjacent TDM channels.
CROSSTALK AND GUARD TIME
13. Demultiplex is a process
reconverting a signal
containing multiple analog
or digital signal streams back
into the original separate
and unrelated signals.
Demultiplexer (Demux) is a
device that performs the
reverse process of
multiplexer.
DEMULTIPLEXING
