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CWNA Guide to Wireless
LANs, Second Edition
Chapter Twelve
Personal, Metropolitan, and Wide Area
Wireless Networks
Objectives
• Define a wireless personal area network
• List the technologies of a wireless metropolitan
area network
• Describe the features of a wireless wide area
network
• Discuss the future of wireless networking
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Wireless Personal Area Networks
• Wireless networks classified into four broad
categories:
– Wireless personal area network (WPAN): Handheld and portable devices; slow to moderate
transmission speeds
– Wireless local area network (WLAN): i.e., IEEE
802.11a/b/g
– Wireless metropolitan area network (WMAN):
Range up to 50 kilometers
– Wireless wide area network (WWAN): Connects
networks in different geographical areas
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Wireless Personal Area Networks
(continued)
Figure 12-1: Wireless network distances
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Wireless Personal Area Networks
(continued)
Figure 12-2: Point-to-point transmission
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Wireless Personal Area Networks
(continued)
Figure 12-3: Point-to-multipoint transmission
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Wireless Personal Area Networks
(continued)
• WPANs encompass technology designed for
portable devices
– PDAs, cell phones, tablet or laptop computers
– Low transmission speeds
• Three main categories:
– IEEE 802.15 standards
– Radio frequency ID (RFID)
– IrDA
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WPANs: IEEE 802.15.1 (Bluetooth)
• Bluetooth uses short-range RF transmissions
– Users can connect wirelessly to wide range of
computing and telecommunications devices
– Rapid and ad hoc connections between devices
• 802.15.1 adapted and expanded from Bluetooth
– Designed for area of about 10 meters
– Rate of transmission below 1 Mbps
• Two types of 802.15.1 network topologies
– Piconet
– Scatternet
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WPANs: IEEE 802.15.1 (continued)
• Piconet: When two 802.15.1 devices come within
range, automatically connect
– Master: Controls wireless traffic
– Slave: Takes commands from master
– Piconet has one master and at least one slave
• Active slave: Connected to piconet and sending
transmissions
• Parked slave: Connected but not actively
participating
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WPANs: IEEE 802.15.1 (continued)
Figure 12-4: Piconet
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WPANs: IEEE 802.15.1 (continued)
Figure 12-5: Slave device detected by a master device
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WPANs: IEEE 802.15.1 (continued)
• Devices in piconet can be in one of five modes:
– Standby: Waiting to join a piconet
– Inquire: Device looking for devices to connect to
– Page: Master device asking to connect to specific
slave
– Connected: Active slave or master
– Park/Hold: Part of piconet but in low-power state
• Scatternet: Group of piconets in which
connections exist between different piconets
• 802.15.1 uses FHSS
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WPANs: IEEE 802.15.1 (continued)
Figure 12-6: Scatternet
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WPANs: IEEE 802.15.1 (continued)
Table 12-1: Comparison of 802.15.1 speed
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WPANs: IEEE 802.15.3
• Created in response to limitations of 802.15.1
– High-rate WPANs
• Two main applications:
– Video and audio distribution for home entertainment
systems
• High-speed digital video transfer
• High-density MPEG2 transfer between video
players/gateways and multiple HD displays
• Home theater
• PC to LCD projector
• Interactive video gaming
– High speed data transfer
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WPANs: IEEE 802.15.3 (continued)
• Differences between 802.15.3 and 802.15.1
–
–
–
–
–
Quality of Service (QoS)
Security
High data rates
Spectrum utilization
Coexistence
Table 12-2: IEEE 802.15.3 security modes
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WPANs: IEEE 802.15.3 (continued)
• 802.15.3a: Will support data transfers up to 110
Mbps between max of 245 devices at 10 meters
– Ultrawideband (UWB)
– Intended to compete with USB 2.0 and FireWire
• IEEE 802.15.3b task group working on improving
implementation and interoperability of 802.15.3
• IEEE 802.15.3c task group developing alternative
physical layer standard that could increase speeds
up to 2 Gbps
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WPANs: IEEE 802.15.4
• Sometimes preferable to have low-speed, lowpower wireless devices
– Size can be dramatically reduced
• IEEE 802.15.4 standard addresses requirements
for RF transmissions requiring low power
consumption and cost
Table 12-3: IEEE 802.15.4 data rates and frequencies
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WPANs: IEEE 802.15.4 (continued)
• ZigBee Alliance: Industry consortium that
promotes 802.15.4 standard
Figure 12-7: ZigBee and IEEE 802.15.4
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WPANs: Radio Frequency ID (RFID)
Figure 12-8: RFID tag
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WPANs: Radio Frequency ID
(continued)
• Passive RFID tags: No power supply
– Can be very small
– Limited amount of information transmitted
• Active RFID tags: Must have power source
– Longer ranges/larger memories than passive tags
Table 12-4: RFID tags
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WPANs: IrDA
• Infrared Data Association
• IrDA specifications include standards for physical
devices and network protocols they use to
communicate
• Devices communicate using infrared light-emitting
diodes
– Recessed into device
– Many design considerations affect IrDA performance
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WPANs: IrDA (continued)
Figure 12-9: IrDA diodes in device
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WPANs: IrDA (continued)
• IrDA drawbacks:
– Designed to work like standard serial port on a
personal computer, which is seldom used today
– Cannot send and receive simultaneously
– Strong ambient light can negatively impact
transmissions
– Angle and distance limitation between
communicating devices
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Wireless Metropolitan Area Networks
• Cover an area of up to 50 kilometers (31 miles)
• Used for two primary reasons:
– Alternative to an organization’s wired backhaul
connection
• i.e., T1, T3, T4 lines
– Fiber Optics
• Very expensive to install backhaul connections
• Often less expensive to use a WMAN to link remote
sites
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Wireless Metropolitan Area Networks
(continued)
• Used for two primary reasons (continued):
– Overcome last mile connection
• Connection that begins at a fast Internet service
provider, goes through local neighborhood, and ends
at the home or office
• Slower-speed connection
– Bottleneck
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Wireless Metropolitan Area Networks:
Free Space Optics
• Optical, wireless, point-to-point, line-of-sight
wireless technology
– Able to transmit at speed comparable to Fiber Optics
– Transmissions sent by low-powered IR beams
• Advantages compared to fiber optic and RF:
–
–
–
–
Lower installation costs
Faster installation
Scaling transmission speed
Good security
• Atmospheric conditions can affect transmission
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Wireless Metropolitan Area Networks:
Local Multipoint Distribution Service
(LMDS)
• LMDS provides wide variety of wireless services
– High-frequency, low-powered RF waves have limited
range
– Point-to-multipoint signal transmission
• Signals transmitted back are point-to-point
– Voice, data, Internet, and video traffic
– Local carrier determines services offered
• LMDS network is composed of cells
– Cell size affected by line of site, antenna height,
overlapping cells, and rainfall
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Wireless Metropolitan Area Networks:
LMDS (continued)
Figure 12-11: LMDS cell
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Wireless Metropolitan Area Networks:
Multichannel Multipoint Distribution
Service (MMDS)
• Many similarities to LMDS
– Differs in area of transmission
– Higher downstream transmission, lower upstream
transmission, greater range
• In homes, alternative to cable modems and DSL
service
• For businesses, alternative to T1 or fiber optic
connections
• MMDS hub typically located at a very high point
– On top of building, towers, mountains
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Wireless Metropolitan Area Networks:
MMDS (continued)
• Hub uses point-to-multipoint architecture
– Multiplexes communications to multiple users
– Tower has backhaul connection
• MMDS uses cells
– Single MMDS cell as large as 100 LDMS cells
• Receiving end uses pizza box antenna
• Advantages:
– Transmission range, cell size, low vulnerability to
poor weather conditions
• Still requires line-of-site, not encrypted
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Wireless Metropolitan Area Networks:
IEEE 802.16 (WiMAX)
• High potential
– Can connect IEEE 802.11 hotspots to Internet
– Can provide alternative to cable and DSL for last
mile connection
– Up to 50 kilometers of linear service area range
– Does not require direct line of sight
– Provides shared data rates up to 70 Mbps
• Uses scheduling system
– Device competes once for initial network entry
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Wireless Metropolitan Area Networks:
IEEE 802.16 (continued)
• Currently addresses only devices in fixed positions
– 802.16e will add mobile devices to the standard
• IEEE 802.20 standard: Sets standards for mobility
over large areas
– Will permit users to roam at high speeds
• WiMAX base stations installed by a wireless
Internet service provider (wireless ISP) can send
high-speed Internet connections to homes and
businesses in a radius of up to 50 km (31 miles)
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Wireless Wide Area Networks
(WWANS)
• Wireless networks extending beyond 50 kilometers
(31 miles)
• Two primary technologies:
– Digital cellular telephony
– Satellites
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Digital Cellular Telephony
• Two keys to cellular telephone networks:
– Coverage area divided into cells
•
•
•
•
Cell transmitter at center
Mobile devices communicate with cell center via RF
Transmitters connected to base station,
Each base station connected to a mobile
telecommunications switching office (MTSO)
– Link between cellular and wired telephone network
– All transmitters and cell phones operate at low
power
• Enables frequency reuse
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Digital Cellular Telephony (continued)
Figure 12-13: Frequency reuse
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Satellites
• Satellite use falls into three broad categories:
– Acquire scientific data, perform research
– Examine Earth
• Military and weather satellites
– “Reflectors”
• Relay signals
• Communications, navigation, broadcast
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Satellites (continued)
• Satellite systems classified by type of orbit:
– Low earth orbiting (LEO): Small area of earth
coverage
• Over 225 satellites needed for total coverage of earth
• Must travel very fast
– Medium earth orbiting (MEO): Larger area of
coverage than LEO
• Do not need to travel as fast
– Geosynchronous earth orbiting (GEO): orbit
matches earth’s rotation
• “Fixed” position
• Very large coverage area
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Satellites (continued)
Figure 12-14: LEO coverage area
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The Future of Wireless Networks
• IEEE 802.11 subcommittees currently at work:
– 802.11d: Supplementary to 802.11 MAC layer
• Promote worldwide use of 802.11 WLANs
– 802.11f: Inter-Access Point Protocol (IAPP)
• Will assist with faster handoff from one AP to another
– 802.11h: Supplement to MAC layer to comply with
European regulations for 5 GHz WLANs
– 802.11j: Incorporates Japanese regulatory
extensions to 802.11a standard
– 802.11s: Defines a mesh wireless network
• Devices configure themselves and are intelligent
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Summary
• WPANs encompass technology that is designed for
portable devices, typically PDAs, cell phones, and
tablet or laptop computers at transmission speeds
lower than the other types of networks
• The IEEE 802.15 standards address wireless
personal area networks
• RFID is not a standard but is a technology that
uses RF tags to transmit information
• IrDA technology uses infrared transmissions to
transmit data at speeds from 9,600 bps to 16 Mbps
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Summary (continued)
• FSO is an optical, wireless, point-to-point wireless
metropolitan area network technology
• LMDS can provide a wide variety of wireless
services, including high-speed Internet access,
real-time multimedia file transfer, remote access to
local area networks, interactive video, video-ondemand, video conferencing, and telephone
• MMDS has many of similarities to LMDS, yet has a
longer distance range
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Summary (continued)
• The IEEE 802.16 (WiMAX) standard holds great
promise for providing higher throughput rates for
fixed location and mobile users
• Wireless wide area network (WWAN) technology
encompasses digital cellular telephony and satellite
• The future of wireless networks is hard to predict,
but most experts agree that wireless networks will
be faster, more global, and easier to use in the
years ahead
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