Frequency Division Multiplexing

&
Time Division Multiplexing
Group TOPNOTCHERS:
Cantoria, Kyle
Doriquez, James Russell
Hubilla, Jake
Furio, John Carlo
Sicad, Jaynebeth
Miday, Donalyn
Jeresano, Rica
What is
MULTIPLEXING?
Multiplexing is the process of
simultaneously transmitting two
or more individual signals over a
single communication channel,
cable or wireless.
 Two predominant ways to
MULTIPLEX

01. FREQUENCY
DIVISION
02. TIME
DIVISION
MULTIPLEXING MULTIPLEXING

-this multiplexing method deals with analog -this method deals with digital information
information where the frequency spectrum can where the transmission of information from
be divided up and parts of it allocated to different several sources over a signal medium is not at the
users on a full-time basis. same time. The transmission is interleaved in the
time domain.
 01. FREQUENCY
DIVISION
MULTIPLEXING

-In this method, multiple sources that originally occupied the same frequency
band (frequency translation) and transmitted simultaneously over a single
transmission medium. It is an analog multiplexing scheme where information
entering an FDM system is analog remains analog throughout transmission.

Frequency Division Multiplexing is used in:

• Television Broadcasting, when audio and video signals share a single channel
• FM radio broadcasting, when two audio signals share a single channel
• A single microwave beam carries microwave transmission of long-distance telephone calls, when60 or
more conversations.

-Note that in fiber optics communications, wavelengths division multiplexing is the method used. This is
basically similar to FDM but instead of frequency several wavelengths (color) of laser light to carry different
signals are used.
Example of communications systems using FDM principle
are:
• AM commercial broadcast (Band: 535-1605
kHz)
• FM commercial broadcast (Band: 88-108 MHz)
• TV commercial broadcast (Band: 54-890 MHz)
 Application of FDM:

1.FDM in AM Commercial
Broadcasting

L-To allow multiple AM stations to broadcast in the AM

Band (535 – 1605 kHz), the entire band is subdivided
into smaller narrow 10 kHz channels so a total of 107
of 10 kHz channels are available. One channel can
be assigned to one station with a specifi c and distinct
carriers frequency. SPCP or single carrier per channel
is used. When the AM band is saturated, it means
that there are 107 AM stations operating at the same
time in one location.
 The number of Channels in the AM Band

10kHZ = international standard bandwidth per AM channel

-Note that without multiplexing, only one station can

broadcast at one time in the AM band in one area since
interference will result if several stations of the same
frequencies will broadcast all together
Application of FDM:

1.FDM in FM Broadcasting

- Just like in AM broadcasting, to allow several

FM stations to broadcasting in the FM band (88-
108 MHz), the FM band is subdivided into 200
kHz channel where there could be a total of 100
channels of 200 kHz each in that given band.
The channel numbering is from 201 to 300
(not from 1 to 100).
The number of Channels in the AM Band

200kHZ = international standard bandwidth per FM

channel
 Example:

A cable TV service uses a single coaxial cable with a

bandwidth of 860 MHz to transmit multiple TV signals to
subscribers. Each TV signal is 6 MHz wide. How many
channels can be carried?
The transmitting Section of an FDM System

-Multiple signals (of same

original frequency) are first
translated into another
frequency spectrum by using
an initial carrier. After
translation they can be
combined in a linear summer
before they will finally
modulate one carrier in one
transmitter and transmitted
as one composite signal via
one antenna facility.
The receiving end of an FDM System

-The composite signal is

received by one antenna
initially demodulated by
one receiver. The band
pass filter can separate
the composite signal into
their respective intended
receiver for final
demodulation to recover
the original signal
transmitted.
 FDM Terminologies

A. Message Channel The message channel is the basic building block of

the FDM hierarchy. The Basic voice frequency (VF)
from 300 to 3000 Hz is a message channel. The
practical voice channel is from 300 – 3400 Hz is
considered the message channel in telephony.

B. Basic Group The basic group is the next higher level in the FDM
hierarchy above the basic message channel. It is the
fi rst multiplexing step for the message channel
comprised of 12 voices band channels stacked on the
top of each other in the frequency domain.

C. Basic Supergroup The basic supergroup in the next higher level in the
FDM hierarchy. It is a combination of fi ve (5) groups
and can carry information from 60 VB channels or
handle high-speed data up to 250 kbps.
 FDM Terminologies

D. Basic Mastergroup The basic mastergroup is the next higher level of

FDM hierarchy. It is comprised of 10 supergroups
equal to 50 groups equal to 600 VB channels.

E. Jumbogroup The jumbogroup is the next higher level after

mastergroup. It is consisting of 9 mastergroups or
3600 voice band channels.

F. Super Jumbogroup The superjumbogroup is the highest level in the North

American (AT & T standard). It is composed of 3
jumbogroups or 10800 voice band channels.

G. Super Mastergroup The supermastergroup is the highest in the CCITT

defi nes hierarchy (a European standard). It is
consisting of 3 mastergroups or 900 voice band
channels. Note that for CCITT mastergroup, the
capacity is 300 voice band channels not 600.
 CCITT
Consultative Committee for International Telegraphy
and Telephony

AT & T
American Telephone and Telegraph Company
Time Division Multiplexing

In time-division multiplexing
(TDM), each signal occupies the
entire bandwidth of the channel.
However, each signal is transmitted
for only a brief time. In other words,
multiple signals take turns
transmitting over the single channel.

Time Division Multiplexing is often

used in the construction of digital
computers. When information can be
stored into or retrieved from the
computer ’s memory at a much greater
rate than it can be supplied or used
by an external device can share a
single multiplexed data channel.
 Basic Principle of
TDM
• If there are four channels that will use one transmission
medium, they will take turn transmitting. In
transmitting section, the multiplexer is acting as a
switch to 4 and then back to 1 and so on and so forth.
One frame to transmit has four channels or the four
channels will become one frame and can be
transmitted by one medium (multiplexing function). In
the receiving section, the demultiplexer has the same
function but with reserve process. The one frame will be
demultiplexed back to four individual channels
(demultiplexed back to four individual channels
(demultiplexing function).
 Basic Principle of
TDM
• Note that the multiplexer and demultiplexer are
perfectly synchronized so that when channel 1
transmits channel 1 receives or channel 1 signal is to
be send to channel 1 receiver. Since synchronizing
pulses are required, this system is suited only to digital
transmission (signals transmitted are digital signals
where the clocking information can be easily
recovered). Clock signals cannot be recovered from a
continuous-type analog signal.
• -If original signals are analog signals. Some sort of
conversion is required before time division multiplexing
them. In this case, the most widely used method to
digitalize analog signal is known as PCM-TDM.
 TDM
Terminologies:
T-Carriers D- Type Channel Bank

T-carriers are digital The D-type channel banks

carriers. They involve the perform the sampling,
transmission of PCM- encoding and multiplexing
encoded time-division, of N voices band channels
time-division-multiplexed where N or number of voice
digital signals using special band channels depend on
line-encoded signals and what T-carrier is used.
metallic cables.
 TDM
Terminologies:
Muldem Framing BIt Line Coding

a multiplexer or Line coding involves

A framing bit is used
demultiplexer device converting standard
for synchronization
used to upgrade from logic levels to a form
between the
one level to the next more suitable to
transmitter and
higher level and vice telephone line
receiver.
versa. transmission.
Thank you
very
much!
BSECE-3A