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
Wireless 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

3
Wireless Networks Coverage
4
Point-to-point and Point-to-multipoint Networks
Point-Point
Point-to-multipoint
5
Wireless Personal Area Networks-WPAN

• WPANs encompass technology designed for portable
  devices
• PDAs, cell phones, tablet or laptop computers
• Low transmission speeds
• Three main categories
• IEEE 802.15 standards (Bluetooth)
• Radio frequency ID (RFID)
• IrDA

6
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
• Up to 1 mw power consumption
• Two types of 802.15.1 network topologies
• Piconet
• Scatternet

7
Piconet IEEE 802.15.1

• 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

8
Scatternet IEEE 802.15.1 Modes

• 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

9
IEEE 802.15.1 speed Comparison
10
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

11
IEEE 802.15.3 Modes

• 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
12
IEEE 802.15.3a, b ,c

• 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

13
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
14
IEEE 802.15.4 ZigBee

• ZigBee Alliance Industry consortium that
  promotes 802.15.4 standard

Figure 12-7 ZigBee and IEEE 802.15.4
15
Radio Frequency ID

• 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

16
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

IrDA diodes in device
17
IrDA Drawbacks

• 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

18
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

19
Wireless Metropolitan Area Networks - WMAN

• Used for two primary reasons
• Used to cover area of 50km (31 miles)
• Used to replace leased lines, T1 and T3
• Use to replace typical fiber (200,000/mile)
• Use to replace city fiber (up to 3M/mile)
• 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 is a bottleneck for users

20
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

21
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
• Support up to 16,000 telephone calls
• For 51 to 155 Mbps over 8km(5miles)
• LMDS network is composed of cells
• Cell size affected by line of site,
• antenna height
• overlapping cells,
• and rainfall

22
Multichannel Multipoint Distribution Service
(MMDS)

• Many similarities to LMDS
• Longer range than LMDS
• Lower vulnerability to weather than LMDS
• Lower cost than LMDS
• Requires line of sight
• Normally not encrypted
• 1.5 Mbps downstream transmission, 300Kbps
  upstream transmission, up to 56km (35 miles)
• Receiving end uses pizza box antenna
• 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

23
IEEE 802.16 (WiMAX)

• WiMAX Worldwide Interoperability for Microwave
  Access
• Highest potential of all WMAN technology
• 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
• Shared data rates up to 70 Mbps (T1 for up to 60
  businesses)
• Longer range than IEEE 802.11 a/b/g
• Uses scheduling system
• Device competes once for initial network entry
  (unlike CDMA/CD and CDMA/CA)
• A dynamic time slot is assigned to a device
• All other devices must wait their turn

24
IEEE 802.16 and 802.20

• IEEE802.16 currently only devices addresses 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 75 to 93 mph
  roaming)

DEPLOYMENT
25
Wireless Wide Area Networks (WWANS)

• Wireless networks extending beyond 50 kilometers
  (31 miles)
• Two primary technologies
• Digital cellular telephony
• Satellites

26
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

27
Digital Cellular Telephony
Frequency reuse
28
Digital Cellular Telephony

• Has evolved since 1980 (analog)
• Now uses digital packet-switch technologies
• Reuses frequency channels- up to 416 channels
• 2G packet switch -GSM
• 2.5 G - CDMA and GPRS networks
• 3.0 G -data rate of above 144 kbit/s EDGE,
  CDMA200, 1x-RTT

29
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

30
Satellites Three Categories

• Satellite systems classified by type of orbit
• Low earth orbiting (LEO) Small area of earth
  coverage
• Up to 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

31
Satellite Low earth orbiting - LEO

• Orbit Altitude -- 321 to 1,448 km (200 to 900
  miles)
• Orbit Speed -- 27,359 kph (17,000 mph)
• Orbit Time -- 90 minutes
• Round trip time delay 20 to 40 milliseconds
• Total earth coverage 50 to 225 satellites

32
Satellite Medium earth orbiting - MEO

• Orbit Altitude 2,413 to16,090 km (1,500 to
  10,000 miles)
• Orbit Speed --
• Orbit Time 12 hours
• Round trip time delay 50 to 150 milliseconds
• Total earth coverage 10 to 20 satellites

33
Satellite Geosynchronous earth orbiting - GEO

• Orbit Altitude 35,860 km(22,282 miles)
• Orbit Speed fixed over a point
• Orbit Time fixed
• Round trip time delay 250 milliseconds
• Total earth coverage three satellites (less
  polar regions)
• Life 12 to 15 years

34
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
• 802.11n WLAN in 2008?
• 802.11s Defines a mesh wireless network
• Devices configure themselves and are intelligent