Computers Are Your Future Twelfth Edition

Computers Are Your FutureTwelfth Edition

Chapter 8: Wired and Wireless Communication

Copyright © 2012 Pearson Education, Inc. Publishing as Prentice Hall 1

Wired and Wireless Communication


Objectives • Differentiate between bandwidth

and throughput, and discuss the bandwidth needs of typical users.

• Discuss how modems transform digital computer signals into analog signals and analog into digital.

• List various physical and wireless transmission media and explain several transmission methods.


Objectives • Explain the limitations of the public

switched telephone network (PSTN) for sending and receiving computer data.

• Describe digital telephony and multiplexing, including their impact on line usage.

• Discuss last-mile technologies that connect users with their communication providers.


Objectives • Provide examples of how

digitization and convergence are blurring the boundaries that distinguish popular communications devices, including phones and computers.

• Discuss various wired and wireless applications.


Moving Data: Bandwidth and Modems

• Communicationso Process of sending and receiving messages

electronically between two pointso Sending device—initiates the transmissiono Receiving device—accepts the transmission

and responds• Communications channel

o Path to send and receive messages



• Analog signalso Continuous waves

• Digital signalso Discontinuous, discrete pulses

• Converterso Translate signals:

• Analog-to-digital converter (ADC)• Digital-to-analog converter (DAC)


Moving Data:Bandwidth and Modems

• Digital signal sampling



• Bandwidtho The maximum amount of data transmitted

through a communication channel at one time• Throughput

o The actual amount of data transmitted



• Broadbando Any transmission medium that carries several

channels transporting data at high speeds• Streaming

o The ability to hear or see content while it is being downloaded from a Web site



• Modemo A communication device used to send and

receive datao The term modem comes from modulate and

demodulate.• The sender uses modulation to transmit

digital signals.• The receiver uses demodulation to return

signals to digital form.





• Types of modemso Analogo Digital subscriber line (DSL)o Cableo Integrated Services Digital Network (ISDN)

• Data transfer rateo Rate at which two modems exchange datao Measured in bits per second (bps)

• Baudo Number of signaling elements per second


Wired TransmissionMedia

• Wiring closet• Houses wiring that supports most types of data

transfer needed



• Twisted-pair wire• Copper wire used for

telephone and data communication

o Two pairs of interweaved wires twisted together

o Inexpensive, but bandwidth too low for video, voice, and data at the same time



• Key variations of twisted-wire pairo Category 5 (Cat-5)o Category 5 enhanced (Cat-5e)o Category 6 (Cat-6)



• Coaxial cableo Consists of copper wire

surrounded by insulation and braided wire

• Broadband communication

• Cable TV• 10 Mbps transfer rate



• Fiber-optic cableo Consists of thin strands

of glass or plastic that carry data through pulses of light

• Broadband communication

• 10 Gbps transfer rate


Wireless TransmissionMedia

• Infraredo Wireless transmission

medium that carries data through the air using light beams

o Sending and receiving devices must be in line of sight

o Uses an IrDA port to enable data transfer



• Radio transmissiono Enables music, photos, and voice to travel

through the air as radio frequency or radio waves

o Bluetooth—radio transmission enables devices within 30 feet to communicate wirelessly

o Does not require direct line of sight





• Microwaveso Transmit data via

electromagnetic radio waves with short frequencies



• Satelliteso Microwave relay stations in space that transmit

data through microwave signalso Direct broadcast satellite (DBS)—consumer

satellite technology that receives digital TV signals through a reception dish

o Requires the computer system to have a special communications device called a network access point—sends and receives data between computer that contain wireless adapters


Wired Communication via the PSTN

• Public switched telephone network (PSTN)o Worldwide telephone system used for data

and voice communicationso Primarily digital

• Subscriber loop carrier (SLC)o Links home and business telephoneso Accommodates analog devices

• Local loopo Area served by an SLC

• Local exchange switcho Digital device capable of handling thousands of calls o Located at the local telephone’s central office




• Digital telephonyo Telephones and transmissions are digitalo Companies—use a private branch exchange

(PBX)• Multiplexing

o Allows multiple calls over a single lineo Long-distance carriers—transmit many calls

in digital format in a single circuit



• Last-mile problemo Inability to access the PSTN’s high-speed,

fiber-optic cables o Bottleneck of data on the last mile of twisted-

pair phone lines• Last-mile technologies

o Provide solutions for bottleneckso Used while local loops are upgraded



• Last-mile technologies (con’t.)o Integrated services digital networking

(ISDN) • Standard that provides digital telephone and

data service• No lengthy dial-in procedures or connection

delay• Requires an ISDN adapter/digital modem to

connect computers to ISDN lines • May be the only broadband solution in rural

areas



• Last-mile technologies (con’t.)o Digital subscriber line (DSL) (Also called xDSL)

• Broad term for group of technologies offering high-speed accesso ADSL (asymmetric digital subscriber line)o SDSL (symmetric digital subscriber line)o HDSL (high bit-rate digital subscriber line)o VDSL (very high bit-rate digital subscriber

line)• Requires DSL modem—modulate and demodulate

analog and digital signals• More expensive than dial-up—cheaper than other

broadband options





• Last-mile technologies (con’t.)o Cable-based broadband

• Provides Internet access through cable TV connections

• Uses cable modems to obtain higher speeds than DSL

o Leased lines • Specially conditioned telephone lines between

two pointso Example: T1 lines



• Last-mile technologies (con’t.) o T2 and T3 lineso SONET (synchronous optical network)o MMDS (Multichannel multipoint

distribution service)o WiMAX (Worldwide interoperability for

microwave access)



Convergence: Is It aPhone or a Computer?

• Digitizationo Process of

transforming data into a digital form

• Convergenceo Blendingo Multiple industries

• Examples: Computers, consumer electronics, telecommunications

o Productso Examples: Personal

computers, telephonesCopyright © 2012 Pearson Education, Inc. Publishing as Prentice Hall 33

• Cellular telephoneso Digital transmission of voice, text, images,

and videoo Classified by generations—4G (fourth

generation)—the current generationo Cell sites—network of transmitters

broadcasts signals throughout geographic areas called cells

Convergence: Is It APhone or A Computer?


• Each cellular network includes multiple mobile switching centers (MSCs) that control communication within a set of cells.



• Personal communication service (PCS)oGroup of digital cellular technologies replacing

most analog cellular serviceso2G (second generation)—used to make

smartphones, with features of phones and computing devices

o3G—more data and voice customers and higher data transfer rates

o4G—improved connectivity, data transfer rates, and support for the next generation of multimedia



• Web-enabled devices o Display and respond to

markup languages• Examples: HTML, XML—

used to build Web pageso Examples

• PDAs • Smartphones—replacing

PDAs• Notebooks



• WAP (Wireless Application Protocol)o Standard—specifies how users can access

the Web securely using:• Pagers• Smartphones• PDAs• Other wireless devices

o Requires a microbrowser



Wired and Wireless Applications

• Internet telephony, or VoIP (Voice over Internet Protocol) o Offers computer-to-phone and phone-to-phone

transmission through the Interneto Placing calls requires:

• Computer with a microphone, speakers or headphones

• Internet connection• Telephony-enabled program



• Internet telephonyo Videoconferencing (Web conferencing)—

transmits sound and video images using:• Video camera (Webcams)• Skype software

o Whiteboards—enable participants to create a shared workspace

o Webcams—inexpensive, low-resolution analog or digital video cameras

o Internet TV—ability to view television shows, videos, and movies over the Internet





• Facsimile transmission (fax)o Transmits documents over a telephone line

or the Internet using either:• Standalone fax machine• Computer with a fax modem and a

scanner



• Satellite technology o Satellite radio

• Not affected by location, distance, or obstructions

• Uses satellites orbiting the Earth• Permits usage in areas with restricted local

radio stations or poor AM/FM reception



• Satellite technology (con’t.) o GPS (Global Positioning System)

• System of 27 satellites allowing a receiver to pinpoint locations

• Mobile units for cars• Installed car systems







• Text messaging (SMS)o Using cell phone for

applications previously used on computers

o Instant messagingo Brief e-mail



• Picture messaging o MMS (multimedia messaging system)o Transmits color pictures and backgrounds o Cellular telephone acts as a camera

• Location awarenesso Also known as position awarenesso Uses GPS-enabled chips to pinpoint the

location of a cell phoneo Popular with parents of teenagers



• Surfing safely at public wireless hot spotso Malicious network (evil twin)—network set

up by a hacker within the operating area of a legitimate hot spot

o Use firewalls and antivirus softwareo Use legitimate networks to avoid “evil twins”o Do not perform financial transactionso Select appropriate operating system settings

to avoid being detected




Summary• Differentiate between bandwidth

and throughput, and discuss the bandwidth needs of typical users.

• Discuss how modems transform digital computer signals into analog signals and analog into digital.

• List various physical and wireless transmission media and explain several transmission methods.


Summary• Explain the limitations of the public

switched telephone network (PSTN) for sending and receiving computer data.

• Describe digital telephony and multiplexing, including their impact on line usage.

• Discuss last-mile technologies that connect users with their communication providers.


Summary• Provide examples of how

digitization and convergence are blurring the boundaries that distinguish popular communications devices, including phones and computers.

• Discuss various wired and wireless applications.


54

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Copyright © 2012 Pearson Education, Inc. Publishing as Prentice Hall

Computers Are Your Future Twelfth Edition

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