cwna guide to wireless lan's second edition - chapter 12

CWNA Guide to Wireless LANs, Second Edition

Chapter TwelvePersonal, Metropolitan, and Wide Area

Wireless Networks

CWNA Guide to Wireless LANs, Second Edition 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


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


Wireless Personal Area Networks (continued)

Figure 12-1: Wireless network distances



Figure 12-2: Point-to-point transmission



Figure 12-3: Point-to-multipoint transmission



• 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


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


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



Figure 12-4: Piconet



Figure 12-5: Slave device detected by a master device



• 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



Figure 12-6: Scatternet



Table 12-1: Comparison of 802.15.1 speed


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



• 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



• 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


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



• ZigBee Alliance: Industry consortium that promotes 802.15.4 standard

Figure 12-7: ZigBee and IEEE 802.15.4


WPANs: Radio Frequency ID (RFID)

Figure 12-8: RFID tag


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


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


WPANs: IrDA (continued)

Figure 12-9: IrDA diodes in device


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


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


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


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


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


Wireless Metropolitan Area Networks: LMDS (continued)

Figure 12-11: LMDS cell


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


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


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


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)


Wireless Wide Area Networks (WWANS)

• Wireless networks extending beyond 50 kilometers (31 miles)

• Two primary technologies:– Digital cellular telephony – Satellites


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


Digital Cellular Telephony (continued)

Figure 12-13: Frequency reuse


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


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


Satellites (continued)

Figure 12-14: LEO coverage area


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


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


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


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

cwna guide to wireless lan's second edition - chapter 12

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