Multiplexing and its ddetailed types with examples

1. Multiplexing

2. Definition
• It is the set of techniques that allows the
simultaneous transmission of multiple signals
across a single data link.

3. Multiplexer - MUX
• It combines different transmission streams
into a single stream. (Many to One)

4. Demultiplexer - DEMUX
• It separates the stream back into its
component transmissions and directs them to
their corresponding lines. (One to Many)
• Link is a physical path, whereas Channel refers
to the portion of a link that carries a
transmission.

5. Frequency Division Multiplexing
• It is an analog technique that can be applied
when the bandwidth of a link is greater than
the combined bandwidths of the signals to be
transmitted.
• So signal generated by each sending device
modulate different carrier frequencies.
• Those modulated signals are combined into a
single composite signal that can be transported
by the link.

6. Frequency Division Multiplexing
• Bandwidth ranges are channels.
• Each channel is separated by unused
bandwidth – guard bands

7. Frequency Division Multiplexing
• Multiplexing Process
– Each source generates a signal of a similar frequency range.
– In multiplexer, these signals modulates different carrier
frequencies.
– Resulting carrier frequencies are combined into a single
composite signal that is sent out over media link.
• Demultiplexing Process
– In demultiplexer, filters decompose the signal into its
component signals.
– Individual signals the passed to demodulator that separates
them from their carrier and passes them to output lines.

8. Wavelength Division Multiplexing
• It is designed to use the high data rate of
capability of fiber-optic.
• It is also an analog technique.
• Process of same as of FDM but involves fiber-
optic and very high frequencies.

9. Synchronous Time Division Multiplexing
• It is digital technique.
• It allows several connections to share the high
bandwidth of a link.
• Instead of sharing a portion of the bandwidth,
time is shared.
• In synchronous, each input connection has an
allotment in the output even if it is not
sending data.

10. Synchronous Time Division Multiplexing
• Time Slot
– Each input connection is divided into units, each input occupies one
input time slot.
– Unit is bit, byte, or block of data.
– Each input unit becomes one output unit and occupies one output
time slot.
– Each output time slot is n times shorter than input time slot.
• Frame
– A round of data units from each input connections is called frame. So
for n connections, a frame is divided n times.
• Output link must be n times the data rate of a connection.

11. Synchronous Time Division Multiplexing
• Interleaving
– Two devices are synchronized to send and receive
data exactly. Setting the devices to receive their
actual time slot to receive data or produce data.
• Empty Slot
– If a source does not have data to send, the
corresponding slot in output frame is empty.

12. Synchronous Time Division Multiplexing
• Data Rate Management
– There may be disparity in the input data rates.
Data rate must be same before sending data.
• Multilevel Multiplexing
– If data rate of input devices is a multiple of others.
• Multiple Slot Allocation
– Allocating more than one slot to single input line,
if data rate is multiple of others.

13. Synchronous Time Division Multiplexing
• Pulse Stuffing
– If data rate of input lines is different
– Adding the bits to input line to make it equal to
highest.
• Frame Synchronizing
– To send and receive bits accurately, a bit, framing
bits, added beginning of each frame.

14. Synchronous Time Division Multiplexing
• Slots are allocated dynamically, if it need to send
data.
• Receiver address is required, as there is no
relationship between inputs and outputs
• Slot size includes data as well as address and ratio
between data and address must be reasonable.
• No synchronization bit is required at frame level.
• Bandwidth capacity of the link is normally less
than the sum of the capacities of each channel.