Computers Are Your Future
Tenth Edition
Chapter 3: Wired & Wireless
Communication
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Publishing as Prentice Hall
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Wired & Wireless
Communication
Copyright © 2009 Pearson Education, Inc. Publishing as Prentice Hall
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What You Will Learn
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Define bandwidth and discuss the
bandwidth needs of typical users
Discuss how modems transform digital
computer signals into analog signals
List transmission media and explain
several transmission methods
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What You Will Learn
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Explain the limitations of the public
switched telephone network (PSTN) for
sending and receiving computer data.
Describe multiplexing and digital
telephony, including their impact on
line usage.
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What You Will Learn
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Provide examples of how digitization
and convergence are blurring the
boundaries that distinguish popular
communications devices, including
phones and computers.
Discuss a variety of wired and wireless
applications.
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Moving Data:
Bandwidth and Modems
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Communications is the method of
sending and receiving messages
electronically between two points.
Communication channels are the
paths through which messages are
passed from one location to another.
Communication occurs over
communication channels.
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Moving Data:
Bandwidth and Modems
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Data movement over communication
channels is performed through analog
and digital signals.
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Analog signals obtain and translate data
into continuous waveforms.
Digital signals change data into discrete,
discontinuous pulses.
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Moving Data:
Bandwidth and Modems
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Moving Data:
Bandwidth and Modems
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The maximum amount of data
transmitted through a communication
channel is referred to as bandwidth.
Broadband is any transmission
medium transporting large amounts of
data at high speeds.
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Moving Data:
Bandwidth and Modems

Communication devices that enable
data transmission over telephone lines
are known as modems.
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Moving Data:
Bandwidth and Modems
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Modulation is the transformation of
digital signals into analog signals.
Demodulation is the transformation of
analog signals into digital signals.
The data transfer rate, the rate at
which two modems exchange data, is
measured in bits per second (bps).
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Wired and Wireless
Transmission Media
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Wired transmission media use solid
forms, such as twisted-pair, coaxial, and
fiber-optic cables, to transmit data.
Wireless transmission media send
data through the air or space by means
of infrared, radio, or microwave signals.
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Wired and Wireless
Transmission Media
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Twisted-pair cables
transmit data using four
insulated twisted wires that
shield against electromagnetic
interference.
Coaxial cables transmit data
and consist of a center copper
wire surrounded by a layer of
braided wire.
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Wired and Wireless
Transmission Media
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Fiber-optic cable is
made up of thin strands
of glass or plastic that
carry data through
pulses of light.
The infrared wireless
transmission medium
carries data through the
air using light beams.
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Wired and Wireless
Transmission Media
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Radio transmissions enable data in
such forms as music, photos, and voice
conversations to travel through the air
as radio frequency or radio waves.
Bluetooth is a short-range radio
transmission technology that enables
devices within 30 feet of each other to
communicate wirelessly.
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Wired and Wireless
Transmission Media
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Microwaves transmit data
and are high-frequency
electro-magnetic radio
waves with very short
frequencies.
Satellites are microwave
relay stations in space that
transmit data through
microwave signals to and
from Earth-based stations.
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Wired and Wireless
Transmission Media
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Direct Broadcast Satellite (DBS) is
a consumer satellite technology that
receives digital TV signals through the
use of a reception dish.
Computer systems using wireless
transmission media require devices for
communication called network access
points.
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Wired Communication via the
Public Switched Telephone
Network
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The public switched telephone
network (PSTN), a worldwide telephone
system, is an immense network used for
data and voice communications.
A subscriber loop carrier (SLC) is a
curbside installation that connects
subscribers.
A local loop is the area served by an SLC.
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Wired Communication via the
Public Switched Telephone
Network
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Wired Communication via the
Public Switched Telephone
Network
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Multiplexing is a technique that
enables sending more than one call
over an individual line.
Last-mile technologies provide
solutions for bottlenecks that result
from the inability of users to access the
PSTN’s high-speed fiber-optic cables.
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Wired Communication via the
Public Switched Telephone
Network
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Integrated Services Digital
Networking (ISDN) is the standard
that makes digital telephone and data
service available.
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Connecting computers to ISDN lines
requires an ISDN adapter/digital
modem.
With ISDN, there is no extended dial-in or
connection delay.
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Wired Communication via the
Public Switched Telephone
Network
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Digital Subscriber Line (DSL) is the
broad term for a group of technologies
that offer high-speed access to the
Internet.
A DSL modem is required to modulate
and demodulate analog and digital
signals.
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Wired Communication via the
Public Switched Telephone
Network
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Wired Communication via the
Public Switched Telephone
Network
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A cable modem is a tool that gives a
computer the ability to access the
Internet through cable TV connections.
Leased lines enable continuous endto-end communication between two
points through specially conditioned
telephone lines, such as T1 lines.
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Wired Communication via the
Public Switched Telephone
Network
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Last-mile technologies include:
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ISDN and DSL
Cable modems and leased lines
T3 lines
Synchronous Optical Network (SONET)
Multichannel Multipoint Distribution Service
(MMDS)
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Convergence: Is It a Phone or
a Computer?
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Digitization is the process of transforming
data into a digital form.
Convergence means two things in IT:
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The blending of multiple industries
such as computers, consumer
electronics, and telecommunications
The blending of products such as
personal computers and telephones
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Convergence: Is It a Phone or
a Computer?
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Cellular telephones, originally analog
devices, are digital devices that use
radio signals to transmit voice, image,
text, and video data.
Cells are the limited geographic areas
through which signals are transmitted.
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Convergence: Is It a Phone or
a Computer?
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Each cellular network
includes multiple
mobile switching
centers (MSCs)
that control
communication
within a set of cells.
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Convergence: Is It a Phone or
a Computer?
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A Personal Communication Service
(PCS) is a group of related digital cellular
technologies that has rapidly replaced the
majority of analog cellular services.
Digital cellular technologies use
convergence to make smartphones,
which combine the features of phones
and computing devices.
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Convergence: Is It a Phone or
a Computer?
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Digital phones resolve some of the
problems of analog telephones by:
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Reducing signal interference
Increasing reception
Enhancing protection from eavesdropping
Making it more difficult to commit cell
phone fraud
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Convergence: Is It a Phone or
a Computer?
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Web-enabled devices
display and respond to
markup languages, such as
HTML or XML, that are
used to build Web pages.
Examples include:
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PDAs
Smartphones
Notebooks
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Wired and Wireless
Applications
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Internet telephony, aka VoIP
(Voice over Internet Protocol), uses
the Internet for real-time voice
communication.
VoIP service providers offer computerto-phone and phone-to-phone services
for long-distance transmission through
the Internet.
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Wired and Wireless
Applications
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Videoconferencing transmits sound and
video images to people in different
locations through digital video technology.
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Wired and Wireless
Applications
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Facsimile transmission (fax) makes
it possible to transmit images of
documents over telephone lines or the
Internet.
A computerized version of a standalone
fax machine is known as a fax
modem, which enables a computer to
perform as a fax machine.
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Wired and Wireless
Applications
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Satellite technology is used for:
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Air navigation
TV and radio broadcasting
Paging
Videoconferencing
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Wired and Wireless
Applications
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Satellite radio is not affected by
location, distance, or obstructions.
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Broadcasts of radio signals are sent
through satellites orbiting the Earth.
Use of satellites permits usage in areas
with restricted local radio stations or bad
AM/FM reception.
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Wired and Wireless
Applications

Global Positioning System (GPS)
is a system of 27 satellites that
interact to allow users to obtain
driving directions and numerous other
types of information.
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Wired and Wireless
Applications

Text messaging
is comparable to
receiving or
transmitting small
e-mail messages or
instant messages
through a cellular
telephone.
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Wired and Wireless
Applications

Picture messaging is the transmission
of color pictures and backgrounds. The
cellular telephone acts as a camera.
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What You’ve Learned
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Bandwidth refers to the maximum data
transfer capacity of a communication
channel.
Modems are used to modulate and
demodulate data sent over dial-up
phone lines.
Communications involve both wired
and wireless media.
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41
What You’ve Learned
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
Use of the public switched telephone
network (PSTN), which is mostly
digital, is decreasing because of the
increase in the use of broadband
alternatives.
Multiplexing is the sending of multiple
telephone calls or messages on a
single line.
Copyright © 2009 Pearson Education, Inc. Publishing as Prentice Hall
42
What You’ve Learned

Digitization is the conversion of voice,
text, graphic, audio, and video data into a
digital format. Convergence is the
merging of products like phones and
computers
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What You’ve Learned

Traditional wired technology can be used
for VoIP and faxing, while wireless
technology makes text and picture
messages, satellite radios, and GPS
services possible.
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