TABLEOFCONTENTS:
1.Wi-FiProtocol:Networking,Frame
Formats,Security,Attributes
2.OSIModelforWi-Fi
3.ArchitectureandNetworkTopology
4.Security,ServicesandApplications
Wi-FiProtocol:Networking,FrameFormats,Security,
Attributes
WirelessFidelity,moreknownbyitsshortformWi-Fi,isadigital
communicationsprotocol,throughwhichgadgetscancommunicate
witheachotherinaunicastorabroadcastingmannerwithoutusing
anywires.TheideaoffastspeedwirelessLANoriginatedwhenthe
UnitedStatesFederalCommunicationsCouncil,acommunication
agencyoftheUSgovernment,decidedintheyear1985toutilizea
fewbandsofwirelessspectrumwithoutsubjectingthemtoalicense
fee.Followingthis,theIEEEcommitteefor802standardswhich
managesnetworkingprotocolsamongelectronicdevices,formedanextension802.11whichwouldworkonthewireless
mode.Thiscommitteewasfoundedintheyear1990andwasheadedbyVictorHayes,FatherofWi-Fi.Takingonthe
licensefreebands(nowbeingtermedasISMbands)andcollaboratingwithnetworkinggiantssuchasNokia,Motorola
etc,thecommitteeintroducedWLANlegacyofWi-Fiintheyear1997.Thehypecreatedbythestandardwassohigh
thatmanymanufacturershadalreadystartedshippinggadgetswiththestandardbeforethestandardbecameofficial.
InordertomaintaintheQoS,serviceswiththeelectronicgadgetsbeingproduced,WirelessEthernetCompatibility
Association(WECA)wassetupintheyear1999andintheyear2002,itsnamegotchangedtoWi-Fialliance.This
tradeorganizationisresponsiblefortestingthegadgetsthatclaimstofulfillthecriteriaofWi-Fibasednetworking.
StartedbyafewcommunicationbasedcompanieslikeNokia,Motorola,Alcatel,theassociationnowhasmorethan
500networkinggiantsthatareinvolvedintesting,sponsoringandworkingofthealliance.TheallianceownstheWi-Fi
trademarkandonlythosedevicesthatcomplywithWi-Fistandards,cangetthetrademarkprintedorengravedontheir
gadget.ItisnowregardedasahighspeedwirelesstransmissionofEthernetservicesthatisenablingsmart
communicategadgetsconnecttoeachotherandtheinternet.
Beingawirelessprotocol,Wi-FistandardusestheISM(Industrial,ScientificandMedical)bandoffrequencywhichare
freetouseandrequirenolicensing.Launchedin2.4GHzwithtransmissionratesof1-2mbps,Wi-Finowworksat5GHz
frequencyalsowithastoundingdatatransmissionratesreachingupto54mbpsatbothfrequencies.
Wi-Fiisamarketingtermappliedto802.11bIEEEstandard,butitnowubiquitouslyusedforallthestandardsthatfall
under802.11categoryofWirelessLAN.So,Wi-Fidefines802.11xstandardswherexistherespectiveWi-Fiversion.
PopularWi-Fiversionarea,b,gandn.
Theterm“Wi-Fi”wasaddedonlytomakethestandardmorecommonandrhymingwith“hifi”,itwaslaterthat“wireless
fidelity”tookthefullformofthisterm.
Abasicnecessityinalmosteverytypeofcomputer,Wi-Fi,hasnowbeenventuredintovariousconsumerappliances
makingthem“smart”enoughtoconnecttotheinternetorstreammediawirelessly.Hence,frombeinganeedforsmart
computinggadgetslikesmartphoneorgamingconsoles,Wi-Finowbeingimplementedinautomobilesandindustries.
Wi-FiisbasedonOSIprotocolandusesthephysicallayerandMACsub0-layeroftheDataLinkLayer.Theother
layershavebeenleftundefinedsothatthemanufacturerisabletocustomizeitaspertherequirementsofthegadget.
Why802.11WLAN?
Ideaofestablishingwirelessnetworkingsystemswasnotoriginatedwiththe802.11standards.Therehavebeen
previouspartiallysuccessfulattemptsthroughALOHA,slottedALOHA,ARDIS,Ricochetetc.wirelessnetworking
systems.However,allofthemlackedthroughputefficiency(outputperunittime)whencomparedtoEthernetandfast
Ethernetsystems.Moreover,securitywasalsoamajorconcernthatrestrictedthesesystemstogoathigherlevels
wherelargeco-operationsordefenseforceswouldadoptthem.802.11waslaunchedwithdatatransmissionspeedsof
1-2mbpswiththeQoSfactorbeingmaintained.Hence,itwaswidelyacceptedforhomeaswellasindustrialnetworking
purposesallovertheworld.
Bluetoothv/sWi-Fi
BluetoothandWi-FibothstandaswirelesscommunicationprotocolsandevensharesomefrequenciesundertheISM
band.However,significantnumbersofdifferencesaretherebetweenthesetwotechnologiesintermsofrange,power
consumption,applicationsetc.MaximumoperatingrangeforBluetoothis10mwhilethatforWi-Fiisaround
100m.Bluetoothprovideseasypairingupbetweendevicesandconsumelesspowerbuttradeoffsaremadeintermsof
securityanddataexchangespeeds.Ontheotherhand,Wi-Fiset-upsarecomplicatedandconsumerhigheramountof
powerbutaresecureandprovidehigherdataexchangespeeds.
CommunicationinWi-Fi
DataexchangeinWi-Ficanbesummarizedintothreephases:
PhaseI:Wheredataispreparedfortransmission;itisencoded;changedintoframes(digitalsignalsaresentinframes
forbetterQoS).Thefrequencyfordatatransmissionisalsochosendependinguponthetechniqueusedtosendthe
signalswirelessly.
PhaseII:Wheredataistransmittedwithairasthemediumofwavetransmission
PhaseIII:Wheredataisreceived,decoded,acknowledgedandthenused.
Allofthesephasesapplysomeofthepopulardigitalcommunicationsspreadspectrumtechniquesforsignal
multiplexing(FHSS,Infrared,OFDMetc.),makeuseofsecuritymethods(WEP,WPA).Let’sfindoutthetechnical
insidesoftheWi-Filegacy.
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