MULTIPLEXING
DEL ROSARIO | TUNGOL
WHAT IS MULTIPLEXING?
It is the process where multiple
message signals, analog or digital, are
combined into one signal.
There are set of techniques that allows
the simultaneous transmission of
multiple signals across a single data
link.
FREQUENCY-DIVISION MULTIPLEXING
It is a multiplexing technique that
combines several analog signals in
a single link with a greater
bandwidth than the combined
bandwidth of the signals to be
transmitted.
Path Physical link
Guard band
Channel Portion of the path that carries a
transmission between a given pair of devices.
MULTIPLEXING
DEMULTIPLEXING
Bandpass Filters
FDM HEIRARCHY
FDM HEIRARCHY
# of Voice Channels
Bandwidth
Terminology
12
48 kHz
Group
60
240 kHz
Supergroup
600
2.52 Mhz
Master group
3600
16.984 Mhz
Jumbo group
Group
Supergroup
Master group
Jumbo group
1 group
5 groups
1 supergroup
50 groups
10
supergroups
300 groups
60
supergroups
1 master
group
6 master
groups
1 jumbo
group
EXAMPLE
PAGE 108, Problem 1
Problem 1. Five channels, each with a
100-kHz bandwidth, are to be
multiplexed together. What is the
minimum bandwidth of the link if there is
a need for a guard band of 10 kHz
between then channels to prevent
interference?
EXAMPLE
Problem 2. Assume that a voice channel
occupies a bandwidth of 4 kHz. We
need to combine three voice channels
into a link with a bandwidth of 12 kHz,
from 20 to 32 kHz. Show the
configuration, using the frequency
domain. Assume there are no guard
bands.
EXAMPLE
Problem 3. How many supergroups are
there in 4 master groups?
Group
Supergroup
Master group
Jumbo group
1 group
5 groups
1 supergroup
50 groups
10
supergroup
s
300 groups
60
supergroups
1 master
group
6 master
groups
1 jumbo
group
PROBLEM
Problem 1.
A single link has a bandwidth
of 15 kHz. Assuming that it
was occupied by 4 channels
with a guard band of 1 kHz,
what is the bandwidth of each
channel?
PROBLEM
Problem 2.
Assume that a voice channel
occupies a bandwidth of 3 kHz.
We need to combine four voice
channels into a link with a
bandwidth of 15 kHz, from 32 to
47 kHz. Show the configuration,
using the frequency domain.
Assume a guard band of 1 kHz.
PROBLEMS
Problem 3.
How many supergroups
are there in 3 jumbo
groups?
Group
Supergroup
Master group
Jumbo group
1 group
5 groups
1 supergroup
50 groups
10
supergroups
300 groups
60
supergroups
1 master
group
6 master
groups
1 jumbo
group
PROBLEMS
Problem 4.
How many master
groups can you create
in 67 supergroups?
Group
Supergroup
Master group
Jumbo group
1 group
5 groups
1 supergroup
50 groups
10
supergroups
300 groups
60
supergroups
1 master
group
6 master
groups
1 jumbo
group
ANALOG SERVICES
Analog Switched
Service
A dial-up service
usually encountered
when using a home
telephone
Uses two-wire
twisted pair cable to
connect handset to
the network
Connection is called
local loop
Analog Leased
Service
Permanently
connected to another
customer
No dialing needed.
WAVE-DIVISION MULTIPLEXING
Also called wavelength division
multiplexing
Multiple beams of light at different
frequency
Carried by optical fiber
A form of FDM
Each color of light (wavelength) carries
separate data channel
1997 Bell Labs 100 beams Each at
10 Gbps Giving 1 terabit per second
(Tbps)
Commercial systems of 160 channels
of 10 Gbps now available
Lab systems (Alcatel) 256 channels at
39.8 Gbps each 10.1 Tbps Over
100km
WDM OPERATION
Number of sources generating laser beams at
different frequencies
Multiplexer consolidates sources for
transmission over single fiber
Optical amplifiers amplify all wavelengths
Typically tens of km apart
Demux separates channels at the destination
Mostly 1550nm wavelength range
Was 200MHz per channel, Now 50GHz
Coarse WDM (CWDM) has wider channel spacing (20
nm) low cost
Dense WDM (DWDM) has dense channel spacing (0.8
nm) which allows simultaneous transmission of 16+
wavelengths high capacity
