Time-division multiplexing is a method of transmitting and receiving independent signals over a common signal path by means of synchronized switches at each end of the transmission line so that each signal appears on the line only a fraction of time in an alternating pattern.

1. TDMTime Division Multiplexing
Md. Hasan Imam Bijoy
Student of C.S.E
Email: hasan15-11743@diu.edu.bd
Daffodil International University, Dhaka, Bangladesh

2. LET’S PRESENT…
Time Division Multiplexing

3. WHAT IS TDM?
• Time-division multiplexing (TDM) is a method of transmitting and receiving
independent signals over a common signal path by means of synchronized switches at
each end of the transmission line so that each signal appears on the line only a fraction
of time in an alternating pattern.
• TDM is a digital multiplexing technique for combining several low-rate channels into
one high-rate one.

4. IS TDM ANALOG OR DIGITAL?
 There are two common techniques for multiplexing the signals: Time Division Multiplexing
(TDM) and Frequency Division Multiplexing (FDM). As I understand it, FDM is commonly used
to multiples analog signals, while TDM is commonly used to multiplex digital signals.

5. Figure : TDM

6. SCHEMES OF TDM
TDM Scheme
Synchronous Statistical.
 We Can divided TDM into two difference Schemes:

7. SYNCHRONOUS
• Time-division multiplexing (TDM) is a digital process that allows several connections
to share the high bandwidth of a line Instead of sharing a portion of the bandwidth
as in FDM, time is shared
• In Synchronous TDM, each input connection has an allotment in the output even if it
is not sending data
• In synchronous TDM, the data flow of each input connection is divided into units,
where each input occupies one input time slot. A unit can be 1 bit, one character, or
one block of data. Each input unit becomes one output unit and occupies one output
time slot.
Synchronous TDM
Time Slots Frames

8. Figure: Synchronous time-division multiplexing

9. MORE ON SYNCHRONOUS
 In synchronous TDM, a round of data units from each input connection is
collected into a frame (we will see the reason for this shortly). If we have n
connections, a frame is divided into n time slots and one slot is allocated for each
unit, one for each input line.
 Time slots are grouped into frames. A frame consists of one complete cycle of
time slots, with one slot dedicated to each sending device. In a system with n input
lines, each frame has n slots, with each slot allocated to carrying data from a
specific
input line.
 Finally we say that:
In synchronous TDM, the data rate of the link is
times faster, and the unit duration is n times
shorter.

10. INTERLEAVING
 Interleaving Synchronous TDM can be compared to a very fast
rotating switch. As the switch opens in front of a device, that device
has the opportunity to send a specified amount (x bits) of data onto
the path. This process is called interleaving. Interleaving can be done
by bit, by byte, or by any other data unit.
 TDM can be visualized as two fast-rotating switches, one on the
multiplexing side and the other on the demultiplexing side. The
switches are synchronized and rotate at the same speed, but in
opposite directions. On the multiplexing side, as the switch opens in
front of a connection, that connection has the opportunity to send a
unit onto the path. This process is called interleaving.

11. Figure : Interleaving

12. WHY TDM USED IN DIGITAL SIGNAL?
 Because it makes sense, your Rx will (usually )
be simpler that way. If you are going TDM, you
are slicing up Time and giving separate slots of
time to different source signals. So each
source info must need to be digitized and
multiplexed into its assigned Time Slot.
Hence digital.

13. WHAT ARE THE APPLICATIONS OF TDM?
 It used in ISDN (Integrated Services Digital
Network) telephone lines.
 It is used in PSTN (public switched telephone
network).
 It is used for some telephone system.
 It is used in wire line telephone lines.
 There are some applications of time division multiplexing
which are given below:

14. ADVANTAGE OF TDM?
 Time division multiplexing systems are more flexible
than frequency division multiplexing.
 Time division multiplexing circuitry is not complex.
 Problem of cross talk is not severe.
 Full available channel bandwidth can be utilized for
each channel

15. DISADVANTAGE OF TDM?
 Synchronization is required in time division
multiplexing.
 Complex to implement.
 Due to slow narrowband fading, all the TDM
channels may get wiped out.