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CWNA Guide to Wireless LANs, Second Edition

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Title: 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

4
Wireless Personal Area Networks (continued)
Figure 12-1 Wireless network distances
5
Wireless Personal Area Networks (continued)
Figure 12-2 Point-to-point transmission
6
Wireless Personal Area Networks (continued)
Figure 12-3 Point-to-multipoint transmission
7
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

8
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

9
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

10
WPANs IEEE 802.15.1 (continued)
Figure 12-4 Piconet
11
WPANs IEEE 802.15.1 (continued)
Figure 12-5 Slave device detected by a master
device
12
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

13
WPANs IEEE 802.15.1 (continued)
Figure 12-6 Scatternet
14
WPANs IEEE 802.15.1 (continued)
Table 12-1 Comparison of 802.15.1 speed
15
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

16
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
17
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

18
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
19
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
20
WPANs Radio Frequency ID (RFID)
Figure 12-8 RFID tag
21
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
22
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

23
WPANs IrDA (continued)
Figure 12-9 IrDA diodes in device
24
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

25
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

26
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

27
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

28
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

29
Wireless Metropolitan Area Networks LMDS
(continued)
Figure 12-11 LMDS cell
30
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

31
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

32
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

33
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)

34
Wireless Wide Area Networks (WWANS)
  • Wireless networks extending beyond 50 kilometers
    (31 miles)
  • Two primary technologies
  • Digital cellular telephony
  • Satellites

35
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

36
Digital Cellular Telephony (continued)
Figure 12-13 Frequency reuse
37
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

38
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

39
Satellites (continued)
Figure 12-14 LEO coverage area
40
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

41
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

42
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

43
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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