CWNA Guide to Wireless LANs, Second Edition

1
CWNA Guide to Wireless LANs, Second Edition

• Chapter Twelve
• Personal, Metropolitan, and Wide Area Wireless
  Networks

2
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

3
Wireless Personal Area Networks

• Wireless networks classified into four broad
  categories
• Wireless personal area network (WPAN) Hand-held
  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, low-power
  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 organizations 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 earths 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-on-demand, 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