Transcript chap05

Chapter 5
Wireless
Technologies
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Objectives
In this chapter, you will learn to:
• Describe the status of wireless e-business today
• Discuss the origins of wireless communications
and the commercialization of the radio range of
the electromagnetic spectrum
• Describe two major short-range wireless
technologies
• Describe a wireless LAN and identify the IEEE
802.11 family of wireless LAN standards
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Objectives
In this chapter, you will learn to:
• Describe pager, cellular, satellite, and other
wireless networks
• Describe the devices, protocols, and languages
of the wireless Web
• Identify expectations for future wireless ebusiness
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Valued Gateway
Client:
Wireless E-Business
• Wireless technologies include:
– Wireless LANs where laptop computers
transmit documents to printers three feet away
– Information transmitted between two PDAs
– Location positioning from an automobile
– Medical images transmitted anywhere via
satellite networks
• As a practical matter, any WAN uses wireless
communications since they are ubiquitous to long
distance communications
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Wireless E-Business
• Analysts predict a huge explosion in the demand for
wireless devices, wireless e-business services, and the
number of wireless Web users within the next three to five
years
• Future growth of wireless e-business based on wireless
technologies advantages including:
– Immediacy - e-business must occur with immediacy
– Personalization - rational or not, users believe wireless
technologies are personal as opposed to public
– Localization - just like a wired connection, a physical
location can be determined for each wireless connection
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A Brief History of Wireless
Communication
• In 1865, James Clerk Maxwell published his theory of
electromagnetic radiation
• In 1873, Heinrich Hertz corroborated Maxwell’s theory when
he proved that electricity could be transmitted via
electromagnetic waves
• In 1895, a young inventor named Guglielmo Marconi began
experimenting with radio waves to send messages
• On December 12, 1901, first wireless transatlantic radio
transmission sent from Cornwall, England to Signal Hill, St.
John’s, Newfoundland
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Electromagnetic Spectrum
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Radio: lowest frequency; the longest wavelength
Microwave: next shortest wavelength
Infrared: slightly longer wavelength than visible
Visible light: range of colors correspond to
frequencies
• Ultraviolet: just beyond the violet end of visible
spectrum
• X-rays: very short wavelength and high-energy
• Gamma rays: shortest wavelength, highest
frequency radiation
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Commercialization of the Radio
Spectrum
• 1920: KDKA, Pittsburgh, PA, the first commercial radio
station in the U.S.
• Circa 1920: Vladimir Zworykin developed technology to
capture, transmit, and view images via wire
• 1927: Philo Farnsworth was first to actually transmit images
via radio waves
• Federal Communications Commission (FCC) regulates the
radio spectrum in U.S.
• U.S. commercial radio spectrum is allocated in two parts:
the FM band from 88.1 to 107.9 MHz, and the AM band from
540 to 1700 kHz
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Short-Range Wireless Technologies
• Wireless technologies that work within the range
of convenience:
– about 10 feet (how does this help security?)
• Technologies support such devices as:
– Remote controls
– PDA to PDA signaling
– Wireless communication between laptops and
printers
• Two wireless technologies satisfy these needs:
IrDA and Bluetooth
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IrDA
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Infrared radiation (IR), part of
the electromagnetic spectrum
that lies just below the visible
red range
The Infrared Data Association
(IrDA) establishes standards
for the IR hardware and
software
IrDA communications require
both devices have a
transceiver (a combination
transmitter and receiver)
IrDA requires a line-of-sight
link
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Bluetooth
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Radiofrequency (RF)
technology operating at 2.45
GHz
Originally created to allow
mobile phones to
communicate with
accessories
Requires small, low-power
transceivers that can be
added to a wireless device for
Bluetooth transmissions
Operates on an unregulated
section of the radio spectrum
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Wireless LANs
• Usually include:
– a wired LAN with computers, printers, servers, and
other devices
– portable devices such as laptops that can connect
when necessary
– access points (also called base stations) that allow
devices to use RF transmissions -- access points
are generally connected to a wire
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IEEE 802.11 Standards
• Define the operation of
wireless networks
• Original standard specified
transmission rate of one to
two Mbps at 2.4 GHz range
• 802.11b specifies up to 11
Mbps
• 802.11a specifies up to 54
Mbps at 5.4 GHz
know how 802.11a differs
from 802.11c - see Table 5-1
• 802.11g specifies up to 54
Mbps at 2.4 GHz
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Long Distance Wireless Networks
• Networks that provide wireless communications
over longer distances than a wireless LAN
include:
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Pager
Cellular phone
Mobile data
Fixed wireless and fixed wireless broadband
Free space optics
Satellite networks
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Pager and Pager Networks
• Pager networks include: paging terminals,
transmitters, and pagers
• Paging terminals accept messages and route
messages to a transmitter for the local pager
area or zone
• The transmitter sends the message to the
appropriate pager
• Multiple local pager zones can be connected to
form a wide area pager network
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Cellular Phones and Cellular Networks
• Metropolitan areas are
divided into transmission
areas called cells
• Base stations service
transmissions with cellular
phones inside cell and
with other cells
• Base stations negotiate
disconnect/connect of
cellular phones as they
move from cell to cell
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Advanced Mobile Phone Systems
(AMPS)
• Analog cell phone standard used in U.S.,
Japan, Scandinavia
• Built on Frequency Division Multiple
Access (FDMA) standard
• Each call used two frequencies: one for
transmitting and one for receiving
• Assigned frequencies to one user at a
time
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Time Division Multiple Access (TDMA)
• Increases the capacity of a radio frequency (over
AMPS) by dividing a frequency or channel into
time slots
• Allows up to six users to send timed,
synchronized conversation fragments over a
shared channel
• Supports digital transmissions for voice, fax, data
(at rates of 64 Kbps to 120 Mbps), multimedia and
videoconferencing, and short text messaging via
Short Message Service (SMS)
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Global System for Mobile (GSM)
Communication
• Hybrid technology, FDMA and TDMA
based
• Allows multiple users to share an RF
channel (up to eight users)
• Supports digital data transmissions
• Supports text messaging with SMS
• Operates at 900, 1800, and 1900 MHz
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Code Division Multiple Access (CDMA)
• Based on direct sequence spread spectrum
(DSSS) technology
• Breaks up digitized and compressed voice data
into many pieces, assigns code to each piece,
then sends the pieces over many different
frequencies — whichever frequencies happen to
be available at transmission time
• Upon arrival at the base station, voice data is
then reassembled using these unique codes
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3G Digital Cellular Networks
• Enables users to receive high-speed voice, data, and
multimedia transmissions via a cell phone
3G
Technologies
CDMA 2000 — Enables broadband video
and multimedia services; has strong vendor
support
W-CDMA —Enables superior voice quality
and high-speed data transmissions
TD-SCDMA —Enhances roaming
capabilities
Universal Mobile Telecommunications
Service (UMTS) — Enables high-speed IP
data and voice transmissions from
anywhere
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Mobile Data Networks
• MDNs provide data services to organizations
with mobile employees
• Subscribers can transmit data from their mobile
devices to base stations positioned in specific
areas
• Base stations then forward the transmissions to
a central messaging switch which is cabled to
an organization’s LAN or mainframe
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Fixed Wireless Broadband Systems
• Provide wireless
communications to or
from a fixed location
• Operate between 90 MHz
to 40 GHz
• Require line-of-sight
positioning of antennae
over relatively short
ranges
• Fixed Wireless Broadband
(FWB) supports a data
transmission rate of about
1 Mbps
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Free Space Optics
• Uses laser to send light pulses through the air to a detector
that can be up to three miles away
• High transmission speeds (144 Mbps – 10 Gbps) over an
unregulated portion of the radio spectrum
• Can provide the “last mile of connectivity” between fiberoptic cable and nearby office buildings
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Communication Satellite Networks
• Satellite networks consist of:
– strategically positioned Earthbound antennae
– ground control facilities
– thousands of weather, scientific, military, and
navigational satellites orbiting the Earth
• Communications satellites act as orbiting radio relay
stations, containing thousands of transponders that
receive voice, video, or data transmissions from Earth
on one frequency and then relay them back to Earth on
another frequency
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Geostationary Orbit (GEO)
Satellite Network
• Positioned 22,300 miles from Earth above
the equator
• Support two-way voice, video, and data
communications
• GEO satellites’ speed matches the Earth’s
rotation, keeping a GEO satellite
positioned directly above the same spot
on Earth
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Low-Earth Orbit (LEO)
Satellite Networks
• Positioned from 400 – 1,600 miles above the
Earth
• Due to their proximity to the Earth, LEO satellites
orbit the Earth in 1.5 – 2 hours to avoid the pull of
gravity
• A LEO satellite network is designed so that more
than one satellite in the network is always visible
• There are two kinds of LEO satellite networks:
little LEO and big LEO
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Medium-Earth Orbit (MEO)
Satellite Networks
• Positioned from 1,500 – 6,500 miles above the
Earth
• Require fewer satellites per coverage area than
LEO networks
• Less transmission latency than GEO networks
• Two MEO networks currently under development
by: Teledesic LLC and ICO Global
Communications, Inc.
• Both networks are designed for high-speed IP
data transmissions, voice, and broadband
Internet access
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Global Positioning System (GPS)
• Uses a network of 24 satellites to establish
position of people, objects, etc.
• Location-based services enable e-businesses to
target offerings to customers based upon
physical location
• Use restricted by law to:
– Locating people in emergencies
– Providing telecommunications services
– Requires customer consent to receive locationbased service offerings
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The Wireless Web
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Improvements in digital cellular technologies
enabled processing of data, pictures, and voice
on wireless handhelds
Long-term success of the wireless Web hinges
on three major issues:
1. Improving view-ability of Web-based
information on hand-held wireless devices
2. Mitigating slow transmission speeds
3. Ease of navigation
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Wireless Application Protocol (WAP)
• Protocol suite or stack that makes it possible to access
Internet resources from a hand-held wireless device
• WAP was developed as a standard for the wireless Web by
the WAP Forum, a consortium of wireless vendors
• The WAP standard defines the wireless application
environment and protocols which work across different
platforms
• WAP suite functions similarly to the protocols in the TCP/IP
suite, but not compatible
• Requires WAP gateway to communicate between wireless
and TCP/IP networks IP
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WAP Protocol Suite
WAP Suite
Description
Wireless Application
Environment (WAE)
Presentation layer: where WML and
WMLScript tools reside
Wireless Session
Protocol (WTP)
Session layer: makes and maintains the
connection
Wireless Transaction
Protocol (WTP)
Transaction layer: keeps data moving
logically and smoothly; confirmations
Wireless Transport
Security layer: data integrity checks,
Layer Security (WTLS) encryption, and authentication
Wireless Datagram
Protocol (WDP)
Data Transport layer: provides common
interface between bearers
Bearer Method
Network Carrier: SMS, GPRS, GSM, etc.
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Wireless Markup Language
• Wireless applications are created with the
Wireless Markup Language and the WMLScript
• The Wireless Markup Language (WML), based on
XML, is used to design content for small-screen
devices
• A WML document (page) is called a deck
• Each deck contains one or more cards containing
text, images, markup instructions, etc.
• WMLScript, similar to JavaScript, manipulates the
content on small screens and performs math
functions
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WAP Gateway
• A WAP-enabled client
issues a request for a WML
page
• The request is sent to a
WAP gateway
• The WAP gateway formats
the HTTP request,
forwarding it to the Web
server
• The Web server sends a
response to the WAP
gateway
• The WAP gateway formats
the data, and sends it to
the wireless device
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Accessing the Wireless Web
• Palm VII PDA was first
hand-held wireless device
to make wireless data
transmissions possible
• PDA not equipped for
phone calls, users needed
separate cellular phone to
get both wireless
voice/data
• Wireless industry
developing hybrid wireless
devices
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Effects of Wireless Technologies
on E-Business
• U.S. consumers see no compelling reason to
make purchases using a wireless device
• Neither the technologies nor the content exist to
ensure positive wireless purchasing experience
• Service providers and equipment vendors are
moving ahead with developing, testing, and
implementing variety of trial wireless e-business
propositions
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Effects of Wireless Technologies
on E-Business
• Wireless becoming a larger part of
vendor/enterprise/customer integration for B2B
purchasing and production
• Knowledge management simplified by wireless
• Improvements in wireless technology make it
cheaper/faster/more convenient to use
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