Lecture11.pdf - ITCS424 Wireless and Mobile Computing...

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ITCS424 Wireless and Mobile ComputingLecture 11Introduction to WLAN & Wi-Fi (Part 1)1
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ContentsWLAN DevicesAP, wireless router, wireless bridge802.11 StandardPhysical Layer: a, b, g, n, i, eMAC Layer: CSMA/CAWLAN Configurationad-hoc mode, infrastructure modeWLAN Roaming3
Wireless Technologies Big PictureBase StationPDA4Internet Backbone2G,3G Cellular NetworkWireless Personal Area Network (WPAN)Wireless Local Area Network (WLAN)Wireless Metropolitan Area Network (WMAN)Satellite Network
Wireless LAN TechnologyIEEE 802.11 or Wi-FiDeveloped by IEEE (Institute of Electrical and Electronics Engineers)5
Wireless LAN & Radio FrequencyWireless LANs use radio frequency (RF) transmission, so the medium is really the atmosphereWireless LAN Radio ComponentsRadio transmitter and receiver, or ________________Also called a radio modulator / demodulator (modem)Antenna6RF waves are transmitted through the air by an antenna. transceiver
WLAN Devices`Wireless Clienthas various forms in various devices.`When client stations have a layer 2 connection with an access point, they are known as_________________.7NotebookPDADesktopWiFi-3G phoneWireless Print ServerassociatedAccess Point,Wireless RouterAntenna
Wireless Network Adapters or Network Interface Cards (NICs)May be an internal or external deviceForm factors include:Internal expansion card, network interface cards (NICs) Internal integrated network adaptersExternal PC Card network adaptersExternal USB network adapters8An IEEE 802.11b wireless NIC expansion card (Photo courtesy of D-Link Systems, Inc.)
Key Characteristics of Wireless NICsInterface type (internal, USB, PCI, PCMCIA, etc.)Wireless standard (802.11a, 802.11b, 802.11g, Bluetooth, etc.)Antenna type (detachable, non-detachable)Power output (40mW, 50mW, 200mW)Power modes (PSP, CAM)9Detach = removeConstantly Awake Mode (CAM)Power Savings Polling (PSP)noalot
Power OutputHigheroutput power provides ________RF rangeOutput power ranges from 30 to 200 milliWatts(mW)Interferencemay become a factor when using higher output powerPower consumption may be a factor for a laptop10greaterhigherdBirlongerhungergame
WLAN DevicesAccess Point (AP) is a _____________ device that performs like a Ethernet hub to provide the connection between wireless client and wired networkHalf duplex means AP has only one radio and performs as a transmitter and a receiver at different timeIncludes a radio transceiver, wireline 802.3 interface11Access Point, Wireless Routerhalfduplexcannotsendereceiveatthesametime
AP ConsiderationsCoverage to provide linkage for every wireless LAN station in its cellPlacement location is best if higherNetwork modeAd-hocif wireless devices will roam__________________if position is relatively static12forverysmallnetworkInfrastructureAP68Wad-hocModoInfraof
Multiradio APsSupport two or more WLAN standards simultaneouslyFor example, IEEE802.11a/b/g13An access point with multiple built-in WLAN radios (Photo courtesy of Intermec Technologies Corp.) ISMLt

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