CWNA guide to wireless LANs 2nd ch12

Wireless Personal Area Networks continued • WPANs encompass technology designed for portable devices – PDAs, cell phones, tablet or laptop computers – Low transmission speeds • Three mai

CWNA Guide to Wireless LANs, Second Edition

Chapter Twelve

Personal, Metropolitan, and Wide Area

Wireless Networks

• 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

– Wireless wide area network (WWAN): Connects

networks in different geographical areas

Wireless Personal Area Networks

(continued)

Figure 12-1: Wireless network distances

Wireless Personal Area Networks

(continued)

Figure 12-2: Point-to-point transmission

Wireless Personal Area Networks

(continued)

Figure 12-3: Point-to-multipoint transmission

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

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

WPANs: IEEE 802.15.1 (continued)

Figure 12-4: Piconet

WPANs: IEEE 802.15.1 (continued)

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

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

WPANs: IEEE 802.15.1 (continued)

Figure 12-6: Scatternet

WPANs: IEEE 802.15.1 (continued)

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

WPANs: IEEE 802.15.3 (continued)

• Differences between 802.15.3 and 802.15.1

– Quality of Service (QoS)

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

WPANs: IEEE 802.15.4

• Sometimes preferable to have 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

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

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

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

• Satellite use falls into three broad categories:

– Acquire scientific data, perform research

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

• 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