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CWNA guide to wireless LANs 2nd ch12

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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