CWNA Guide to Wireless
LANs, Second Edition
Chapter One
It’s a Wireless World
Objectives
• Describe how wireless technology is used in daily
activities
• Tell how wireless local area networks are used in
applications such as education, business, travel,
construction, and other areas
• Explain the advantages and disadvantages of
wireless technology
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A Day in the Life of a Wireless User:
Home
• Hotspots: Locations where wireless data services
are available
• Wireless local area network (WLAN): Essentially
identical to standard local area network (LAN)
– Except devices not connected by wires
– Can increase productivity
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A Day in the Life of a Wireless User:
Car
• Bluetooth wireless standard: Enables short
range wireless communication
– Used in many small devices
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A Day in the Life of a Wireless User:
Office
• Fixed broadband wireless: Wireless
transmissions between immobile devices
– Typically between office buildings
– Utilizes small, customized antennas
• Free space optics (FSO): Alternative to highspeed fiber optic transmissions
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A Day in the Life of a Wireless User:
Field
• Handheld devices used to connect to nearest cell
tower
– Cell tower connects to local telephone company
– Telephone company connects to appropriate
resources
• Such as e-mail servers
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A Day in the Life of a Wireless User:
On Site
• Radio frequency identification (RFID) tags:
– “Electronic barcodes”
– Used to identify items
– Can be read if anywhere within range of transmitted
radio signal
• Depending on device
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A Look at Wireless Technologies
• Wireless technology woven throughout many
aspects of life
• Useful to get overview of some current
technologies in today’s wireless world
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Wireless Local Area Networks
(WLANs)
• Wi-Fi (Wireless Fidelity): Based on standard that
transmits at up to 11 Mbps
• Computers on WLAN must have wireless network
interface cards (wireless NIC or Wireless
adapter)
– Performs same basic functions as standard NIC,
plus more
• Access point (AP): Transfers signals between
wireless NICs
• Patch cable connects AP to wired LAN or Internet
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Wireless Local Area Networks
(continued)
Figure 1-3: Wireless LAN
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Wireless Local Area Networks
(continued)
Figure 1-4: Home wireless LAN
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What is a wireless LAN?
• Wireless LAN (WLAN) - provides all the features
and benefits of traditional LAN technologies such
as Ethernet and Token Ring, but without the
limitations of wires or cables.
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http://earlyradiohistory.us/1920au.htm
What is a wireless LAN?
• WLAN, like a LAN, requires a physical medium to transmit
signals.
• Instead of using UTP, WLANs use:
– Infrared light (IR)
• 802.11 does include an IR specification
• limitations, easily blocked, no real 802.11 products (IrDA)
– Radio frequencies (RFs)
• toCan
penetrate
‘most’
office obstructions
CWNA Guide
Wireless
LANs, Second
Edition
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What is a
wireless LAN?
More later!
• WLANs use the 2.4 GHz and 5-GHz frequency bands.
• ISM (Industry, Scientific, Medical) license-free (unlicensed)
frequency bands.
• S-Band ISM
– 802.11b and 802.11g: 2.4- 2.5 GHz
• C-Band ISM
– 802.11a: 5.725 – 5.875 GHz
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Icons – Wireless Devices and
Functions
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Icons - Buildings
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Icons – Typical Wired Network Devices
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Icons – Wireless LAN Antenna
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IEEE 802.11 and the Wi-Fi Alliance
• IEEE LAN/MAN Standards Committee (LMSC)
– First 802.11 standard released in 1997, several since then
•
Wireless Ethernet Compatibility Alliance (WECA)
– Advertises its Wi-Fi (wireless fidelity) program
– Any 802.11 vendor can have its products tested for
interoperability
CWNA Guide to Wireless LANs, Second Edition
– Cisco is a founding member
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Wi-Fi™
• Wi-Fi™ Alliance
–
–
–
–
WECA changed its name to Wi-Fi
Wireless Fidelity Alliance
170+ members
Over 350 products certified
• Wi-Fi’s™ Mission
– Certify interoperability of WLAN products (802.11)
– Wi-Fi™ is the “stamp of approval”
– Promote Wi-Fi™ as the global standard
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Other Wireless Technologies
Not discussed in this course:
• Cellular
• Bluetooth or PAN (Personal Area Network)
• 3G (3rd Generation)
• UWB (Ultra Wide Band)
• FSO (Free Space Optics)
CWNA
Guide to
Wireless off
LANs,
Second Edition
• Radio
waves
meteor
trails!
21
Why Wireless?
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WLAN Evolution
•Warehousing
•Retail
•Healthcare
•Education
•Businesses
•Home
Speed
860 Kbps
Network
Radio
Standards-based
Proprietary
900 MHz
2.4 GHz

1986
1988
11 Mbps 54 Mbps
1 and
1 and
2 Mbps
2 Mbps
1990
IEEE 802.11Begins
Drafting
1992
1994
5 GHz
2.4 GHz
1996
802.11
Ratified
802.11a,b 802.11g
Ratified
Drafted
1998
2000
2002
Current Standards – a, b, g
Speed
860 Kbps
Radio
900 MHz
2.4 GHz

1986
Standards-based
Proprietary
Network
1988
11 Mbps 54 Mbps
1 and
1 and
2 Mbps
2 Mbps
1990
IEEE 802.11Begins
Drafting
1992
1994
5 GHz
2.4 GHz
1996
802.11
Ratified
802.11a,b 802.11g
Ratified
Ratified
1998
2000
2003
• 802.11a
– Up to 54 Mbps
– 5 GHz
– Not compatible with either 802.11b or 802.11g
• 802.11b
– Up to 11 Mbps
– 2.4 GHz
• 802.11g
– Up to 54 Mbps
– 2.4 GHz
802.11g is backwards compatible
with 802.11b, but with a drawback
(later)
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802.11 PHY (Physical Layer) Technologies
Speed
860 Kbps
Radio
900 MHz
2.4 GHz

1986
Standards-based
Proprietary
Network
1988
11 Mbps 54 Mbps
1 and
1 and
2 Mbps
2 Mbps
1990
IEEE 802.11Begins
Drafting
1992
1994
5 GHz
2.4 GHz
1996
802.11
Ratified
802.11a,b 802.11g
Ratified
Ratified
1998
2000
2003
• Infrared light
• Three types of radio transmission within the unlicensed 2.4-GHz
frequency bands:
– Frequency hopping spread spectrum (FHSS) 802.11b (not used)
– Direct sequence spread spectrum (DSSS) 802.11b
– Orthogonal frequency-division multiplexing (OFDM) 802.11g
• One type of radio transmission within the unlicensed 5-GHz
frequency bands:
– Orthogonal frequency-division multiplexing (OFDM) 802.11a
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Major Factors
• There are four major factors to consider before
implementing a wireless network:
• High availability
• Scalability
• Manageability
• Open architecture
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Atmosphere: the wireless medium
• Wireless signals are electromagnetic waves
• No physical medium is necessary
• The ability of radio waves to pass through walls and cover
great
makes
wireless a versatile way to build a
CWNA
Guidedistances
to Wireless LANs,
Second Edition
network.
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Electromagnetic
Spectrum
The
Electromagnetic
Spectrum Chart
• The waves differ only in their frequency.
• All of these waves share some very important characteristics.
– Travel at the speed of light
– Obey the equation (frequency) x (wavelength) = c (speed of light).
– Very different interactions with various materials.
• Low frequency electromagnetic waves have a long wavelength,
while high frequency electromagnetic waves have a short
wavelength.
• Wavelength represents the distance from one peak to the next on
the sine wave.
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The Electromagnetic Wave Equation
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The size of a bit
• “Speed of the link” or “Speed of the network”
• Sometimes we forget that the speed of the data
always travels near the speed of light:
– 180,000 miles/second or 300,000 meters/second
• What changes is the length of the bit.
• Using the formula: speed of light = frequency x
wavelength
• 1 bps =
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Distance versus Speed
• WLANs are only one usage of the radio frequency (RF)
spectrum.
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Bluetooth
• Low-power wireless data and voice transmission
technology
• Bluetooth devices communicate via radio modules
– Link manager: Software that helps identify other
Bluetooth devices, creates links between devices,
and sends and receives data
• Transmit data at up to 1 Mbps over 10 meters
• Bluetooth devices within range of each other
automatically connect
– Master and slave
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Bluetooth (continued)
• Piconet: Bluetooth network containing a master
and at least one slave
Figure 1-5: Bluetooth device
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Bluetooth
• Uses devices with small radio transceivers, called radio
modules, built onto microprocessor chips
• Special software, called a link manager, identifies other
Bluetooth devices, creates links with them, and sends and
receives data
• Transmits at up to 1 Mbps over a distance of 33 feet and is
not impeded by physical barriers
• Bluetooth products created by over 1500 computer,
telephone, and peripheral vendors
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Bluetooth Headset
• The Bluetooth
headset
automatically
establishes a
connection
with the telephone
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Piconet
• Two or more Bluetooth devices that send and
receive data make up a personal area network
(PAN), also called a piconet
• Figure 1-3 shows a Bluetooth network
Bluetooth was named after the 10th century
Danish King Harold Bluetooth, who was
responsible for unifying Scandinavia
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Bluetooth Network
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Telecommunications Links
• Integrated Services Digital Networks (ISDN):
Transmits at 256 Kbps
• T-1 lines: Transmit at 1.544 Mbps
• Cable modems: Use television cable connection
• Digital subscriber lines (DSL): Use telephone
lines
• WiMax: Signal transmitted between antennas
– Up to 75 Mbps and over up to 35 miles
– Fixed Broadband
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Telecommunications Links (continued)
• FSO: Transmit at speeds up to 1.25 Gbps over up
to 4 miles
– Line-of-site transmission
Figure 1-6: Free space optics transceiver
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Telecommunications Links (continued)
Figure 1-7: Wireless office technologies
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2G Digital Cellular
• Personal Digital Assistant
(PDA)
• Hand-held device
• May include a barcode
scanner and keyboard, as
shown in Figure 1-6
• Data may be transmitted
to
a terminal using wireless
digital cellular technology
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Three Standards
• The second generation (2G) standard sends data
at rates up to 14 thousand bits per second (kilobits
per second or Kbps)
• In the future, the third generation (3G) technology
may transmit up to 2 Mbps using a universal
standard
• An interim technology known as 2.5 G offers a
bandwidth of up to 384 Kbps
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Digital Cellular Network
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Cellular Telephony
• Global Systems for Mobile (GSM)
communications technology: Coverage includes
most of US and parts of Europe and Japan
– Transmission speeds up to 9.6 Kbps
– Information transmitted based on Wireless
Application Protocol (WAP)
• Standard way to transmit, format, and display data for
devices like cell phones and handheld devices
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Cellular Telephony (continued)
Figure 1-8: Browsing the World Wide Web
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Cellular Telephony (continued)
• WAP cell phone runs a microbrowser that uses
Wireless Markup Language (WML) instead of
HTML
• WAP gateway or proxy: Translates between WML
and HTML
Figure 1-9: WAP communications
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Radio Frequency Identification (RFID)
• Like an electronic barcode:
– Can contain larger amounts of updatable information
– Information transmitted via radio waves
– Range typically about 1 foot at 5 Mbps
Figure 1-10: RFID tag
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Fixed Broadband Wireless and Other
Alternatives
• Integrated Service Digital Networks (ISDN)—
consist of leased lines that transmit at 256 Kbps
• Expensive T-1 lines—transmit at 1.544 Mbps
• Cable modems—use television cable connections
• Digital subscriber lines (DSL)—have limited
availability
• Fixed broadband wireless—a faster less expensive
choice
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Fixed Broadband Wireless
• Fixed broadband transmits as far as 35 miles at
speeds up to 1 billion bits per second (gigabits or
Gbps) for downloads and 512 Kbps for uploads
• Uses small custom antenna on roof of each
connected building
• Figure 1-11 shows fixed broadband wireless
network
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Fixed Broadband Wireless Network
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Satellite
• Transmits data to/from satellite circling the earth
• A repeater in the satellite simply “repeats” the
signal to another location
• Earth station transmits at one frequency and
receives the signal at another frequency
• Transmission time from one earth station to
another is approximately 250 milliseconds
• See Figure 1-4
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Satellite Frequency Transmission
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A Satellite Network
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Wireless Technology Categories
Table 1-1: Typical wireless technologies
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Wireless LAN Applications: Education
• Educational institutions some of first adopters of
WLANs
– Dramatic advantages in teaching and learning
• Wireless LAN connections offer students important
degree of freedom
• WLAN technology translates into cost savings for
colleges
– Reduces need for wiring and infrastructure
– Fewer computer labs necessary
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Wireless LAN Applications: Education
(continued)
Figure 1-11: Campus access point locations
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Wireless LAN Applications: Business
• Wireless LAN technologies have significantly
changed how business conducted
– Meetings not confined to conference rooms
– Easier to connect to network resources and Internet
– Can create office in space where traditional
infrastructure does not exist
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Wireless LAN Applications: Travel
• Travel industry perhaps adopted wireless
technologies more than any other industry
– Many airport terminals provide wireless hotspots
– Several large airlines providing wireless capabilities
to passengers during flights
– Some airlines use WLAN technology to
communicate with aircraft on ground
– Some airlines use WLAN technology to facilitate
maintenance tasks
– Some airlines use new wireless data service to send
and receive messages
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Wireless LAN Applications:
Construction
• Wireless technology has greatly benefited
construction industry
– Better management of resources
– Better management of paperwork
• Construction equipment being fitted with wireless
terminals
– “Smart” equipment
– GPS information can provide location information to
within centimeters
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Wireless LAN Applications:
Warehouse Management
• New products arrive continuously
– Must be inventoried and stored
• Products being shipped must first be located then
transferred to correct location and truck
– Mistakes in inventory or inability to locate items can
be devastating
– Mark inventory with RFID tags
• Warehouse management system (WMS)
software: Can manage all activities from receiving
through shipping
– Utilize wireless technology
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Wireless LAN Applications: Public
Safety
• Public safety departments using WLANs and GSM
to communicate information with public safety
vehicles
– City-owned buildings equipped with APs
– Large volumes of data can be quickly downloaded to
vehicles
• e.g., building floor plans, photographs of criminal
suspects, and maps
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Wireless LAN Applications: Healthcare
• Wireless LAN point-of-care computer systems
allow medical staff to access and update patient
records immediately
– Document patient’s medication administration
immediately
– Extensive use of RFID tags
• Identify healthcare professionals, patients,
medications
– System verifies that medication being administered
to correct patient in correct dosage
• Eliminates potential errors and documentation
inefficiencies
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Wireless LAN Applications: Healthcare
(continued)
• Documentation process takes place at bedside
where care delivered
– Improves accuracy
• Hospital personnel have real-time access to latest
medication and patient status information
• Wireless technology also used in other medical
areas:
– e.g., video pills
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Wireless LAN Applications: Healthcare
(continued)
Figure 1-12: Video pill
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Wireless Advantages and
Disadvantages: Advantages
• Mobility: Primary advantage of wireless
technology
– Enables individuals to use devices no matter where
users roam within range of network
– Increasingly mobile workforce is characteristic of
today’s business world
– WLANs give mobile workers freedom while allowing
them to access network resources
– “Flatter” organizations: WLANs give team-based
workers ability to access network resources needed
while collaborating in team environment
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Wireless Advantages and
Disadvantages: Advantages
(continued)
• Easier and Less Expensive Installation:
Installing network cabling in older buildings difficult
and costly
– Wireless LAN is ideal solution
– Eliminating need for cabling results in cost savings
• Significant time savings as well
– Allows offices to reorganize easily
• Increased Reliability: Wireless LAN technology
eliminates certain types of cable failures and
increases overall network reliability
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Wireless Advantages and
Disadvantages: Advantages
(continued)
• Disaster Recovery: Documented disaster
recovery plan vital to every business
– Hot site: Off-site facility that can run business’s
operations if primary site is not available
• Generally maintained by third party
• Expensive
– Cold site: Customer provides and installs
equipment
• Many businesses use cold sites and WLANs as major
piece of disaster recovery plan
– No consideration given to network cabling
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Wireless Advantages and
Disadvantages: Disadvantages
• Security: Wireless signals broadcast in open air
– Security for wireless LANs is prime concern
• Unauthorized users might access network
– War driving
• Attackers might view transmitted data
• Employees could install rogue access points
• Attackers could easily crack existing wireless security
– Older wireless products have very weak security
features
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Wireless Advantages and
Disadvantages: Disadvantages
(continued)
• Radio Signal Interference: Signals from other
devices can disrupt wireless transmissions
– Or wireless device may be source of interference for
other devices
– e.g., Microwave ovens, elevator motors,
photocopying machines, theft protection devices,
cordless telephones
– Solution: Locate source of interference and remove
• Health Risks: Wireless devices emit RF energy
– Not known if or to what extent low levels of RF might
cause adverse health effects
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Summary
• Wireless devices and technologies enable users to
roam almost anywhere and remain connected to
data and voice networks
• A WLAN, also known as Wi-Fi, functions the same
as a standard wired network except devices send
radio frequency signals through the air instead of
being connected to the network by cabling
• Bluetooth devices communicate using small radio
transceivers called radio modules that are built into
microprocessor chips
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Summary (continued)
• Two popular technologies are WiMax and free
space optics (FSO)
• Handheld devices can send and receive wireless
signals using the Global System for Mobile (GSM)
communications technology
• RFID tags function as electronic barcodes
• Wireless personal area networks (WPANs) cover
technologies where the transmission generally
extends only a few meters or feet, whereas
wireless local area networks (WLANs) are
generally restricted to 112 meters (375 feet)
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Summary (continued)
• Wireless LAN applications can be found in
industries in which employees need the freedom to
conduct business without being confined to a
specific location
• Wireless LANs have significant advantages,
including increased mobility, easier and less
expensive network installations, increased network
reliability, and disaster recovery
• Some of the disadvantages of wireless LANs
include security, radio signal interference, and
health concerns
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