WIRELESS LAN
Presented by
Ching-Man Chong
Tracy Tien
Johnny Wong
Zhong Wei Yu
WIRELESS LAN
WIRLESS LOCAL AREA NETWORK
WIRELESS LAN
Introduction
 Wireless Technology
 Wireless LAN
 Configuration
 Differences between wired LAN vs
wireless LAN
 Cost-Benefit Study
 Customer Considerations
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INTRODUCTION
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Data communications system
Alternates wired LAN
Transmits and receives data over the air
Minimize the need for wired connections
Become more popular in general-purpose
alternative of business customers.
Benefited several industries in productivity
and mobility
WHY WIRELESS?
Advantages:
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MOBILITY
INSTALLATION
COST
SCALABILITY
MOBILITY
Real-time information access from
anywhere at any time
 Increases productivity and flexibility
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INSTALLATION
Fast and easy
 No cable needed
 No frustration with wiring
 Go where wires cannot go
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COST
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Short run
– Initial investment is higher than wired LAN
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Long run
– Long-term costs is essentially lower than
wired LAN
– Long-term cost and benefits are very
important in dynamic and ever-changing
business environments
SCALABILITY
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Can be configured in different topologies to
meet the specification of applications and
installations
Can be easily changed from peer-to-peer
networks (small # of users) to full
infrastructure networks (thousands of users)
IN THE REAL WORLD
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Not a replacement for the wired infrastructure
Great complement to what currently exists
Examples
– Doctors and nurses
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more productive in delivering patients’ information and
status instantly
– Student
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access the Internet to consult the catalog of the Library
of Congress
– Network managers
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provide backup for mission-critical applications
HOW IT WORKS
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Use electromagnetic airwaves to
communicate information
Data imposed on radio carrier (radio wave)
RF electromagnetic wave can easily
pass through ordinary wall, it needs to
implement with heavy concrete or metal
screening.
WIRELESS TECHNOLOGY
WIRELESS TECHNOLOGY
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Satellite-Based System
– Geosynchronous Earth Orbiting (GEO)
– Low Earth Orbiting (LEO)
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Land-Based Network Access System
– Wireless WAN
– Wireless LAN
GEO SATELLITES
Circle the earth from a height of 22,300
miles
 3 satellites can be used to provide
worldwide coverage
 used for:
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– television broadcasts, long distance
telecommunications, and various science
and military applications
LEO SATELLITES
Orbit no higher than 500 miles above
the earth
 Travel the earth in a couple of hours
 Multiple satellites needed
 Allow access to very low-power devices
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WIRELESS WAN
Provide nationwide or citywide coverage
 Example: Ricochet Micro-Cell
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Coverage in Washington
D.C., San Francisco, and
Seattle
Source: http://dcs.umd.edu
WIRELESS LAN
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Wireless LAN Topology
– 2 main components
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Access Points
Adapters
– Roaming
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Wireless LAN Technology
– Types
– Standard
– Configuration
ACCESS POINTS
Connects to the wired network
 single access point can support a small
group of users within a range of several
hundred feet
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Wireless Clients Connected to LAN
via Access Point
Source: http://dcs.umd.edu
ADAPTERS
Users used wireless-LAN adapters to
connect to access points
 Implemented as :
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– PC cards in notebook computers
– ISA or PCI cards in desktop computers
– Integrated within hand-held computers
ROAMING
Each access point can provide between
50,000 to 250,000 square feet of
coverage
 Example: Hospital Environment
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Source: http://dcs.umd.edu
WIRELESS LAN TECHNOLOGY
Narrowband Technology
 Spread Spectrum Technology
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– Frequency-Hopping Spread Spectrum
Technology
– Direct-Sequence Spread Spectrum
Technology
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Infrared Technology
NARROWBAND TECHNOLOGY
Transmits and receives user information
on a specific radio frequency
 keeps the radio signal frequency as
narrow as possible
 Radio receiver filters out all radio
signals except the ones on its
designated frequency
 Example: private telephone lines
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SPREAD SPECTRUM
TECHNOLOGY
Mostly used in wireless LAN system
 Trades of bandwidth efficiency for
reliability, integrity, and security
 Signal looks like background noise if not
turned to the right frequency
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FREQUENCY-HOPPING SPREAD
SPECTRUM TECHNOLOGY
Uses a narrowband carrier that changes
frequency in a pattern known to both
transmitter and receiver
 Maintain a single logical channel
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FREQUENCY-HOPPING SPREAD
SPRECTRUM TECHNOLOGY (con’t)
Source: www.wlana.com
DIRECT-SEQUENCE SPREAD
SPECTRUM TECHNOLOGY
Generates a redundant bit (chip)
pattern for each bit to be transmitted
 The longer the chip, the greater the
probability that the original data can be
recovered
 To unintended receivers:
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– Viewed as low-power wideband noise
– Rejected by most narrowband receivers
DIRECT-SEQUENCE SPREAD
SPECTRUM TECHNOLOGY (con’t)
Source: www.wlana.com
INFRARED (IR) TECHNOLOGY
Little used in commercial wireless LANs
 Use very high frequencies
 Inexpensive, but provide very limited
range (3ft)
 Typically used for personal area
networks
 Used only to implement fixed
subnetworks
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WIRELESS STANDARD
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IEEE 802.11
– represent the 1st standard for wireless LAN
– standardize radio equipment and networks
operating system for wireless LAN
– Addresses for:
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Physical (PHY) layer
Media Access Control (MAC)
CONFIGURATION
Peer-to-peer network
 Client and Access point
 Multiple access points and roaming
 Using an extension point
 Using directional antennas
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PEER-TO-PEER NETWORK
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Wireless adapter cards
– Connect 2 PCs
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Client access only to each other, not
with a central server
Source: http://www.proxim.com
CLIENT & ACCESS POINT (AP)
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Access point
– Must be wired to the
network
– Extend the range of the
network
– Allow access from clientto-server and among each
workstation
– Real-world: each Access
Point can accommodate
from 15-50 client devices
Source: http://www.proxim.com
MULPTIPLE AP & ROAMING
In large facility, more than one AP
might be needed to coverage the whole
area
 Access Point range:
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– Indoor = 500 ft; Outdoor = 1,000 ft
Source: http://www.proxim.com
EXTENTION POINT (EP)
EP can be connected to the network
without wiring.
 EP extend the range of the network by
relaying signals from a client to an AP
or another EP.
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Source: http://www.proxim.com
DIRECTIONAL ANTENNAS
Extend the wireless networks between
buildings
 Antenna must be connected to an AP of
the network
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Source: http://www.proxim.com
PHYSICAL LAYER
MEDIUM ACCESS CONTROL
A collision may occur when 2 stations
transmit data simultaneously
 Detects the collision and ignores the
message
 Each station that wants to transmit
waits a random amount of time and
then attempts to transmit again
 The random transmission delays reduce
the probability that the stations will
transmit simultaneously again.
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DIFFERENCES BETWEEN
WIRED LAN
AND
WIRELESS LAN
WIRED vs. WIRELESS LAN
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Wired
– Link clients,
printers, and
network
equipment
using cables
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Wireless
– Basic building
block is the Cell
Source:
www.breezecom.com
WIRED
WIRELESS
WIRE vs. WIRELESS (con’t)
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Bridging
– Wired
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Access point connects
to the backbone of a
wired Ethernet LAN
via a simple cable
– Wireless
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can be mounted
back-to-back with an
access point
Able to link buildings
that are miles apart
Source: www.breezecom.com
WIRED vs. WIRELESS (con’t)
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Cells
– Linked Cells (Wired)
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user can walk from
Cell A to overlap Cell
B without interrupting
a work session
– Multi-cells (Wireless)
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Position Access Points
at different locations
in the coverage areas
with their directional
antennas
Source: www.breezecom.com
WHEN DO YOU NEED
WIRELESS LAN
TECHNOLOGY?
WHEN?
When you truly need mobility
 When you plan to move or remodel
soon
 When set up a portable buildings for
temporary use
 When you don’t have time to configure
and maintain a wiring scheme
 When running cable is too expensive
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Cost-Benefit Study
COST-BENEFIT STUDY
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89% successful implementation
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92% of respondents believe the
definite economic and business
benefit after installation
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92% continue to deploy wireless
technology in their network
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Payback was less than 1 year across
all industries surveyed.
Source: www.wlana.com
COST/BENEFIT STUDY (con’t)
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Economic Benefits
– Payback
Source: www.wlana.com
COST/BENEFIT STUDY (con’t)
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Broad cross-section of the
representative industries with successful
implementation of wireless LAN
– Education: 23%
– Healthcare: 23%
– Manufacturing/Warehouse: 21%
– Retail: 15%
– Financial/Office Automation: 18%
Source: www.wlana.com
Wireless LAN Market
WIRELESS LAN MARKET
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Customer considerations
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Range and coverage
Throughput
Compatibility
Interoperability
Interference and Coexistence
Licensing issues
Simplicity
Security
Cost
Major vendors
Scalability
Customer Considerations
CUSTOMER CONSIDERATIONS
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Range and coverage
– Mostly use Radio Frequency because it can
penetrate most indoor walls and obstacles
– Range varies from under 100 feet to more
than 300 feet
– Coverage can be extended
CUSTOMER CONSIDERATIONS
(con’t)
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Throughput
– Actual throughput is product and set-up
dependent
– Affecting factors:
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# of users
Range and multipath
Type of wireless LAN system used
CUSTOMER CONSIDERATIONS
(con’t)
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Compatibility with existing network
– Most wireless LANs provide industrystandard interconnection with wired
networks such as Ethernet or Token Ring.
– Wireless LAN nodes are supported by
network operating systems through uses of
appropriate drivers.
CUSTOMER CONSIDERATIONS
(con’t)
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Interoperability of wireless devices
– Different vendors might not be
interoperable
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Three reasons
– System based on spread spectrum frequency
hopping (FHSS) will not communicate with direct
sequence (DSSS).
– Different frequency bands will not interoperate even
with same technology.
– Differences in implementation.
CUSTOMER CONSIDERATIONS
(con’t)
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Interferences and Coexistence
– Unlicensed wireless transmitting energy in
same frequency spectrum can provide
interference. (ex. Microwave oven)
– Co-location of multiple wireless LANs:
more wireless LANs, more interferences.
CUSTOMER CONSIDERATIONS
(con’t)
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Licensing
– Federal Communications Commission (FCC)
– Wireless LANs operate in portions of radio
spectrum: end user does not require license.
– Manufacturer must ensure certification by agency
in that country to distribute the use of wireless
LANs.
– In US: broadcast over ISM (Instrumentation,
Scientific, and Medical) bands.
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Bands: 902-928MHz, 2.4-2.483 GHz, 5.15-5.35 GHz,
5.725-5.875 GHz.
CUSTOMER CONSIDERATIONS
(con’t)
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Simplicity
– Wireless is transparent to users.
– Applications is same with wired LANs.
– Only access points is require cabling.
– Portable from place to place after
configured.
CUSTOMER CONSIDERATIONS
(con’t)
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Security
– Complex encryption techniques is used.
– Individual nodes must be security enable
before they are allowed to participate in
network traffic.
CUSTOMER CONSIDERATIONS
(con’t)
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Cost
– Infrastructure costs
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Wireless access points.
Number of access points deployed ($1,000 to
$2,000).
Coverage region/type of users serviced.
– User costs
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Wireless LAN adapters.
Price range from $300 to $1,000.
CUSTOMER CONSIDERTAIONS
(con’t)
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Cost of Installation and Maintenance
– Lower direct cost
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Eliminates direct costs of cabling, labor
associated with installing and repair.
– Lower indirect cost
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Reduce indirect costs of user downtime and
administrative overhead as it simplify moves,
adds, and changes
CUSTOMER CONSIDERATIONS
(con’t)
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MAJOR VENDORS
– 6 major vendors for the wireless LAN
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Aironet
AMD
Digital Equipment Corporation
Harris Semiconductor
Intermec Technologies Corporation
Lucent Technologies
CUSTOMER CONSIDERATIONS
(con’t)
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Scalability
– Adding access points: to extend coverage.
SUMMARY OF THE PROJECT
More to discover about wireless LAN
 Wireless is very popular and exciting
 Much knowledge was gained through
this project
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References
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dcs.umd.edu/telecom/library/paper.html
www.biz.uiowa.edu
www.blackbox.com
www.breezecom.com/TechSupport/brztov.htm
www.geocities.com/CapeCanaveral/Orbit/2694/wlanl.
htm
www.k12.hi.us.htm
www.proxim.com
www.wirelesslan.com
www.wlana.com
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