Wireless Networks Step By Step

Dr.ShahbazChatthaYanbuUniversityCollege,2017
Drr..ShaahbaazzChaatttthaa
WirelessNetworks2017
CSETDepartment.

YanbuUniversityCollege
Dr.ShahbazChattha
Office:J1Room20
Email:shahbazchattha@gmail.com

IntroductiontoWLANs
3

IntroductiontoWLANs
4

IntroductiontoWLANs
WiredNetwork
5
WirelessNetwork

Dr.ShahbazChattha
YanbuUniversityCollege
Introduction
Incomputing,WirelessLocalArea
Network(WLAN)isatermtorefertoa
LocalAreaNetworkthatdoesnotneed
cablestoconnectthedifferentdevices.
Instead,radiowavesandIEEE802.11
areusedtocommunicate.
6

IntroductiontoWLANs
Awirelesslocalareanetwork(WLAN)isawirelesscomputer
networkthatlinkstwoormoredevicesusingawireless
distributionmethod(oftenspread-spectrumorOFDMradio)within
alimitedareasuchasahome,school,computerlaboratory,or
officebuilding.
Thisgivesuserstheabilitytomovearoundwithinalocal
coverageareaandyetstillbeconnectedtothenetwork.
AWLANcanalsoprovideaconnectiontothewiderInternet.
MostmodernWLANsarebasedonIEEE802.11standardsand
aremarketedundertheWi-Fibrandname.
7

EvolutionOfCommunication-From1Gto4G&Towards5G

WirelessNetworks

WirelessWideAreaNetworks
*AWANcanspanalargegeographicalarea(acountry,multiplecountries,andevencontinents).
TheInternetisaclassicexampleofaWAN.
AWirelessWideAreaNetwork(WWAN)isa
classofWAN*technologiesthatusesmostly
cellularandsatelliteinfrastructurestoenable
interconnectivityoveraWANviaseveral
services,suchas:
GlobalSystemforMobile(GSM).
UniversalMobileTelecom.System
(UMTS).
LongTermEvolution(LTE).

WirelessWideAreaNetworks

WirelessMetropolitanArea
Networks
AMANcanspanamoderatelylargegeographicalarea.Thescopeofthearea
coveredbyaMANisoftenwithinacitybutalmostcertainlyrestrictedtowithin
acountry.
AWMANreferstowirelesstechnologies
thatfacilitateinterconnectivitywirelessly
inametropolitanarea.
WMANscanbeconsideredmid-range
networks.
Theynormallydonotusethecellular
networkinfrastructure,butinsteadmake
useofsomevendor-specific
technology.

Networks
WiMAXOverview
WorldwideInteroperabilityforMicrowaveAccess(WiMAX)isusedin
buildingWMANnetworks.
thatitcanbeusedtobypassthetraditionalcableorwired
infrastructuretoprovideconnectivitybetweenthecommunications
providerandthecustomer.
WiMAXoperatesinthe266GHzfrequencyrange.
WiMAXisgovernedbythedetailsspecifiedintheIEEE802.16
WirelessMAN.

Networks
WiMAXIncarnations
Twoincarnationsofthestandardareimportanttowirelessnetworkadministrators:
FixedWiMAXThisfirstmainstreamversionofWiMAXwaswidelyadopted.Itis
especiallysuitedforpoint-to-multipoint(one-many)applications.Itsinner
workingsarespecifiedinIEEE802.16d.
FixedWiMAXispurportedtosupportwirelesscoverageofupto30miles(50
km).
MobileWiMAXThedetailsoftheinnerworkingsofMobileWiMAXaregoverned
bytheIEEE802.16estandard.Itwasdevelopedtosupportmobilewireless
clients.
MobileWiMAXispurportedtosupportwirelesscoverageofupto10miles(15
km).Smartantennatechnology,suchasMIMO,isusedinMobileWiMAXto
improvegainandprovidebetterthroughputs.

WirelessPersonalArea
Networks
AWPANisusedfor
facilitatingcommunication
betweendevicesinavery
smallarea.
WPANcanbeconsideredashort-rangenetworkbecausethe
rangeandreachofthiswirelessnetworktypeistypicallyquite
limited.
AWPANrequireslittleexternalinfrastructuretooperate;most
WPANsareself-contained.
TheIEEE802.15standardsdescribespecificationsforthe
innerworkingsofWPANs.
SeveraltechnologiesexistforenablingWPANs,suchas:
Bluetooth
ZigBee
Z-Wave
InfraredDataAssociation(IrDA)
Ultra-Wideband(UWB)

Networks
BluetoothOverview
Bluetoothtechnologyreplacesthecablestraditionallyusedfor
connectingnumerouselectronicdevices.
Bluetoothusesthefrequency-hoppingspreadspectrum(FHSS)
modulationtechnique.
Itsdevicesoperateinthe2.42.4835GHzunlicensedfrequency
range.

Networks
BluetoothOverview
Bluetoothtechnologyreplacesthecablestraditionallyusedfor
connectingnumerouselectronicdevices.
Bluetoothusesthefrequency-hoppingspreadspectrum(FHSS)
Itsdevicesoperateinthe2.42.4835GHzunlicensedfrequency
range.
IEEE802.15.1-2002
IEEE802.15.1-2005

Networks
ZigBeeOverview
ZigBeeisespeciallysuitedforuseinembeddedapplications
thatrequirelowdataratesandlowpowerconsumption.
ZigBeeistargetedforuseinwirelessmonitoringandcontrol
systemsandautomationtypeapplications.
ZigBeeusesthedirect-sequencespreadspectrum(DSSS)
IEEE802.15.4
Itoperatesindifferentfrequencybandsinvariouspartsoftheworld:
868868.8MHzrange(Europe).
902928MHzrange(NorthAmerica).
24002483.5MHzrange(Worldwide).

IEEE802.11operationmodes
InfrastructureMode(usedto
connectcomputerswithwirelessnetwork
adapterstoanexistingwirednetwork
withthehelpfromwirelessrouteror
accesspoint).
AdHocMode(usedtoconnect
wirelessclientsdirectlytogether
needforawirelessrouteroraccess
point).
MeshMode(usedtoconnect
wirelessMeshnodestoeachother
wirelesslyratherthanviaEthernet).
26

Anaccesspoint(AP)isa
stationthatprovidesframe
distributionserviceto
stationsassociatedwith
it.TheAPitselfistypically
connectedbywiretoaLAN.
Awirelessnetworkinterface
card(adapter)isadevice,
calledastation,providing
thenetworkphysicallayer
overaradiolinktoanother
station.
27
WIRELESSLAN

EachAPhasa0to32bytelongServiceSet
Identifier(SSID)thatisalsocommonlycalled
anetworkname.
ThestationandAPeachcontainanetwork
interfacethathasaMediaAccessControl
(MAC)address,justaswirednetworkcards
do.
Thisaddressisaworld-wide-unique48-bit
number,assignedtoitatthetimeof
manufacture.
The48-bitaddressisoftenrepresentedasa
stringofsixoctetsseparatedbycolons(e.g.,
00:02:2D:17:B9:E8)orhyphens(e.g.,00-02-
2D-17-B9-E8).
WhiletheMACaddressasassignedbythe
manufacturerisprintedonthedevice,the
addresscanbechangedinsoftware.
WIRELESSLAN
28

TheIEEE802.11standard
establishesanddefinesthe
modeofchannelingthe
unlicensedradiofrequency
bandsinWLANs.
The2.4GHzbandisbroken
downinto11channelsforNorth
Americaand13channelsfor
Europe.Thesechannelshavea
centerfrequencyseparationof
only5MHzandanoverall
channelbandwidth(or
frequencyoccupation)of22
MHz.
WIRELESSLAN
29

IEEE802.11referstoafamilyof
specificationsdevelopedbytheIEEE
forover-the-airinterfacebetweena
wirelessclientandanAccessPoint
(betweentwowirelessclients).
Tobecalled802.11devices,they
mustconformtotheMediumAccess
Control(MAC)andPhysicalLayer
specifications.
TheIEEE802.11standardcoversthe
Physical(Layer1)andDataLink
(Layer2)layersoftheOSIModel.
WIRELESSLAN
30

WirelessStandards
Organizations
TheInternationalTelecommunicationUnionRadio
CommunicationSector(ITU-R).
FederalCommunicationsCommission(FCC).
Eachofthestandardsorganizationshelptoguidea
differentaspectofthewirelessnetworkingindustryand
settherulesforwhattheusercandowitharadio
transmitter.
31

WirelessStandards
Organizations
IEEE(InstituteofElectricalandElectronicsEngineers)is
thelargestprofessionalorganizationforstandardsinthe
world.
IEEE802referstoafamilyofIEEEstandardsdealingwith
localareanetworksandmetropolitanareanetworks.
Morespecifically,theIEEE802standardsarerestrictedto
networkscarryingvariable-sizepackets.
Thenumber802wassimplythenextfreenumberIEEE
couldassign,though802issometimesassociatedwith
thedatethefirstmeetingwasheldFebruary1980.
IEEE-802standardshavebeenadoptedbyISDasinter
nationalstandardsknownasISO8802.
32

NAMEDESCRIPTIONNOTE
IEEE802.1Bridging(networking)andNetworkManagement
IEEE802.2LLCinactive
IEEE802.3Ethernet
IEEE802.4Tokenbusdisbanded
IEEE802.5DefinestheMAClayerforaTokenRinginactive
IEEE802.6MANs(DQDB)disbanded
IEEE802.7BroadbandLANusingCoaxialCabledisbanded
IEEE802.8FiberOpticTAGdisbanded
IEEE802.9IntegratedServicesLAN(ISLANorisoEthernet)disbanded
IEEE802.10InteroperableLANSecuritydisbanded
IEEE802.11
WirelessLAN(WLAN)&Mesh(Wi-Fi
certification)
IEEE802.12100BaseVGdisbanded
IEEE802.13Unused
ReservedforFastReservedforFast
EthernetEthernet
development
IEEE802.14Cablemodemsdisbanded
IEEE802StandardsTable
33
NAMEDESCRIPTIONNOTE
IEEE802.15WirelessPAN
IEEE802.15.1Bluetoothcertification
IEEE802.15.2IEEE802.15andIEEE802.11coexistence
IEEE802.15.3HighHigh-High-RatewirelessPAN(e.g.,UWB,etc.)
IEEE802.15.4
LowLow-Low-RatewirelessPAN(e.g.,ZigBee,LowRatewirelessPAN(e.g.,ZigBee,RatewirelessPAN(e.g.,ZigBee,RatewirelessPAN(e.g.,ZigBee,
WirelessHART,MiWi,etc.)
IEEE802.15.5MeshnetworkingforWPAN
IEEE802.15.6Bodyareanetwork
IEEE802.16
BroadbandWirelessAccess(WiMAX
certification)
IEEE802.16.1LocalMultipointDistributionService
IEEE802.17Resilientpacketring
IEEE802.18RadioRegulatoryTAG
IEEE802.19CoexistenceTAG
IEEE802.20MobileBroadbandWirelessAccess
IEEE802.21MediaIndependentHandoff
IEEE802.22WirelessRegionalAreaNetwork
IEEE802.23EmergencyServicesWorkingGroup
IEEE802.24SmartGridTAG
NewNew
(November,(November,
2012)
IEEE802.25OmniOmni-Omni-RangeAreaNetwork
NotyetNotyet
ratified

WhatisWi-Fi?
Wi-Fiisawirelessnetworkingtechnologythatallows
computersandotherdevicestocommunicateovera
wirelesssignal.
Itdescribesnetworkcomponentsthatarebasedonone
ofthe802.11standardsdevelopedbytheIEEEand
adoptedbytheWi-FiAlliance.
ExamplesofWi-Fistandards,inchronologicalorder,
include:
802.11a
802.11b
802.11g
802.11n
802.11ac
WIRELESSLAN
34

802.11a
TheIEEE802.11aadoptedthe
OrthogonalFrequency-Division
Multiplexing(OFDM)modulation
techniqueandusesthe5GHz
band.
The802.11adevicesoperatingin
the5GHzbandarelesslikelyto
experienceinterferencethan
devicesthatoperateinthe2.4
GHzbandbecausethereare
fewerconsumerdevicesthatuse
the5GHzband.Also,higher
frequenciesallowfortheuseof
smallerantennas.
WIRELESSLAN
Advantages:
Speed:UsesuptoUpto54
Mbps
Hasthefastesttransmission
speed.
Allowsformore
simultaneoususers.
Usesthe5GHzfrequency,
whichlimitsinterference
fromotherdevices.
Disadvantages:
Higherfrequencyradio
wavesaremoreeasily
absorbedbyobstaclessuch
aswalls,making802.11a
susceptibletopoor
performancedueto
obstructions.
Higherfrequencybandhas
slightlypoorerrangethan
either802.11bor802.11g.
Also,somecountries,
includingRussia,donot
permittheuseofthe5GHz
band,whichmaycontinueto
curtailitsdeployment.
Isnotcompatiblewith
802.11bnetworkadapters,
routers,andaccesspoints.
35

802.11b
Thiswasthefirstand,until
recently,themostcommon
wirelessvariantused.With
transmissionspeedsofjust
11Mbpsitisalsotheslowestusing
the2.4GHzband.
Italsousedthe40bitWireless
EquivalencyPrivacy(WEP)
securityprotocol,whichwasfound
tohaveanumberofdeficiencies.
Anewerversionofthis,802.11b+
maintainsspeedsto22Mbits/sec.
WIRELESSLAN
36

802.11g
Thisisthemostrecentand
popularinusenow,
offeringmorerespectable
datatransferspeedsofup
to54Mbps,usingthe2.4
GHzband.
Italsousesanupgraded
formofWi-FiProtected
Access(WPA)security
protocol.
WIRELESSLAN
Advantages:
Speed:UsesUpto54
Mbps,Hasa
transmissionspeed
comparableto802.11a
underoptimal
conditions
Allowsformore
simultaneoususers
Hasthebestsignal
rangeandisnot
easilyobstructed
Iscompatiblewith
802.11bnetwork
adapters,routers,
andaccesspoints.
Disadvantages:
Usesthe2.4GHz
frequencysoithas
thesame
interference
problemsas
802.11b
Costsmorethan
802.11b
37

802.11n
The802.11ndraftstandardisintendedtoimprovewirelessdataratesand
rangewithoutrequiringadditionalpowerorradiofrequencybandallocation
usingthe2.4GHzor5GHzfrequencybands.
The802.11nusesmultipleradiosandantennaeatendpoints,each
broadcastingonthesamefrequencytoestablishmultiplestreams.
Themultipleinput/multipleoutputtechnologysplitsahighdata-ratestreaminto
multiplelowerratestreamsandbroadcasts,meanwhileovertheavailable
radiosandantennae.
Thisallowsforaspeculativemaximumdatarateof248Mb/susingtwo
streams.
WIRELESSLAN
38

802.11ac
802.11acisthenextgenerationofWi-Fithefifth,tobespecificanditisexpectedtobeat
leastthreetimesfasterthan802.11nintheory,asmuchas10timesfaster.
Operatinginthe5GHzband.IntheUS,5.0GHzoffers23non-overlappingchannelsand
haslessnoise,whichmeanshigherbandwidth.However,italsomeansithasshorterrange
anddoesnotpenetratesolidobjectswell.ThismeansmoreAPsareneeded.
Togetmorethan75Mbps,twotechniquesareusedchannelbondingandspatialstream
multiplexing.
In802.11nchannelbondingisdonebycombiningtwo20MHzstreamstoget40MHz
spectrum,orbandwidthof150Mbpsperstream.
With802.11ac,morechannelsarebondedtoget80MHzandeventually160MHz
spectrum,whichcancarry433Mbpsand866Mbpsperstream,respectively.(Note:
802.11acdevicesdonotsupportthe160MHzspectrum).
WIRELESSLAN
39

Typesofwirelesscommunication
cellularwirelesscomputernetworkradioservice
40

Electromagneticradiationspectrum
41

Electromagneticradiationspectrum
42

WavelengthofSome
Technologies
GSMPhones:
frequency~=900Mhz
wavelength~=33cm
PCSPhones
frequency~=1.8Ghz
wavelength~=17.5cm
Bluetooth:
frequency~=2.4Gz
wavelength~=12.5cm
43

Typesofelectromagneticcarriers
Whenthedistancebetweenthesenderandreceiveris
short(e.g.TVboxandaremotecontrol)infrared
wavesareused.
Forlongrangedistancesbetweensenderandreceiver
(e.g.TVbroadcastingandcellularservice)both
microwavesandradiowavesareused:
Radiowavesareidealwhenlargeareasneedtobe
coveredandobstaclesexistinthetransmissionpath.
Microwavesaregoodwhenlargeareasneedtobecovered
andnoobstaclesexistinthetransmissionpath.
44

Wirelessapplications(services)
45

Advantagesanddisadvantagesofwireless
communication
46
Advantages:
Mobility
Awirelesscommunicationnetworkisasolutioninareaswhere
cablesareimpossibletoinstall(e.g.hazardousareas,long
distancesetc.)
Easiertomaintain
Disadvantages:
Hassecurityvulnerabilities
Highcostsforsettingtheinfrastructure
Unlikewiredcomm.,wirelesscomm.isinfluencedbyphysical
obstructions,climaticconditions,interferencefromotherwireless
devices

FrequencyCarries/Channels
47
Theinformationfromsendertoreceiveriscarrierovera
welldefinedfrequencyband.
Thisiscalledachannel.
Eachchannelhasafixedfrequencybandwidth(inKHz)
andCapacity(bit-rate).
Differentfrequencybands(channels)canbeusedto
transmitinformationinparallelandindependently.

Radiowavesgeneration
48
whenahigh-frequencyalternatingcurrent(AC)passesthrougha
copperconductoritgeneratesradiowaveswhicharepropagatedinto
theairusinganantenna.
Radiowaveshavefrequenciesbetween:
3Hz300KHz-lowfrequency
300KHz30MHzhighfrequency
30MHz300MHzveryhighfrequency
300MHz300GHzultrahighfrequency

RadioPropagation
49

RadioPropagation
50
Radiowavesaregeneratedbyanantennaandtheypropagateinall
directionsasastraightline.
Radiowavestravelatavelocityof186,000milespersecond.
Radiowavesbecomeweakerastheytravelalongdistance.

RadioPropagation
Thereare3modesofpropagation:
Surfacemodeforlowfrequencywaves.
Directmodeforhighfrequencywaves.
Ionosphericmodelongdistancehighfrequencywaves.
51

Modulation
Modulation:
Addinginformation(e.g.voice)
toacarrierelectromagnetic
(radio)signal.
52
AmplitudeModulation(AM).
FrequencyModulation(FM).

Radiofrequencyinterference
53

Radiosignalattenuation(path
loss)
54

Radiosignalattenuation(path
loss)
55

ConceptofAntenna
Anantenna,oraerial,isanelectricaldevicewhich
convertselectricpowerintoradiowaves,andviceversa.
Intransmission,aradiotransmittersuppliesanelectric
currentoscillatingatradiofrequency(i.e.ahighfrequency
alternatingcurrent(AC))totheantenna'sterminals,and
theantennaradiatestheenergyfromthecurrentas
electromagneticwaves(radiowaves).
Inreception,anantennainterceptssomeofthepowerof
anelectromagneticwaveinordertoproduceatiny
voltageatitsterminals,thatisappliedtoareceivertobe
amplified.
56

ConceptofAntenna
57

ConceptofAntenna
58
Animationofahalf-wavedipoleantenna
transmittingradiowaves,showingthe
electricfieldlines.
Theantennainthecenteristwovertical
metalrods,withanalternatingcurrent
appliedatitscenterfromaradiotransmitter
(notshown).
Thevoltagechargesthetwosidesofthe
antennaalternatelypositive(+)and
negative().
Loopsofelectricfield(blacklines)leavethe
antennaandtravelawayatthespeedof
light;thesearetheradiowaves.

ConceptofAntenna
59
Animateddiagramofahalf-wavedipoleantennareceivingenergyfromaradio
wave.TheantennaconsistsoftwometalrodsconnectedtoareceiverR.The
electricfield(E,greenarrows)oftheincomingwavepushestheelectronsin
therodsbackandforth,chargingtheendsalternatelypositive(+)and
negative().Sincethelengthoftheantennaisonehalfthewavelengthofthe
wave,theoscillatingfieldinducesstandingwavesofvoltage(V,represented
byredband)andcurrentintherods.Theoscillatingcurrents(blackarrows)
flowdownthetransmissionlineandthroughthereceiver(representedbythe
resistanceR).

ConceptofAntenna
60
Accordingtotheirapplicationsandtechnologyavailable,antennasgenerallyfallinoneoftwo
categories:
Omnidirectionaloronlyweaklydirectionalantennaswhichreceiveorradiatemoreorlessinall
directions.Theseareemployedwhentherelativepositionoftheotherstationisunknownor
arbitrary.Theyarealsousedatlowerfrequencieswhereadirectionalantennawouldbetoolarge,
orsimplytocutcostsinapplicationswhereadirectionalantennaisn'trequired.
Directionalorbeamantennaswhichareintendedtopreferentiallyradiateorreceiveinaparticular
directionordirectionalpattern.
Incommonusage"omnidirectional"usuallyreferstoallhorizontaldirections,typicallywithreduced
performanceinthedirectionoftheskyortheground(atrulyisotropicradiatorisnotevenpossible).
A"directional"antennausuallyisintendedtomaximizeitscouplingtotheelectromagneticfieldinthe
directionoftheotherstation,orsometimestocoveraparticularsectorsuchasa120°horizontalfan
patterninthecaseofapanelantennaatacellsite.
Isotropicantennaisahypothetical(notphysicallyrealizable)concept,usedasausefulreference
todescriberealantennas.Isotropicantennaradiatesequallyinalldirections.

AntennaCharacterization
61
AntennasgenerateEMfieldpatternnotalwayspossibleto
modelmathematically.
difficulttoaccountforobstacles.
antennasarestudiedinEMisolatedroomstoextractkey
performancecharacteristics.

TypesofAntenna
62
Dipole
Fractal
Loop
Satellitedish
Television
Whip

OmnidirectionalAntenna
63
Anantenna,whichhas
anon-directional
patterninaplane.
Itisusuallydirectional
inotherplanes

DirectionalAntenna
64
Directionalantennaisanantenna,whichradiates(orreceives)muchmore
powerin(orfrom)somedirectionsthanin(orfrom)others.
Note:Usually,thistermisappliedtoantennaswhosedirectivityismuchhigher
thanthatofahalf-wavelengthdipole.

Beamwidth
65
Half-powerbeamwidth(HPBW)istheangle
betweentwovectorsfromtheorigintothe
pointsofthemajorlobewheretheradiationintensity
ishalfitsmaximum
Oftenusedtodescribetheantennaresolution
properties
Importantinradartechnology,radioastronomy,
etc.
First-nullbeamwidth(FNBW)istheanglebetween
twovectors,originatingattheoriginand
tangenttothemainbeamatitsbase.
OftenFNBW2*HPBW

Patternlobes&BeamWidths
66

AntennaGain
67
ThetermAntennaGaindescribeshowmuchpoweristransmittedin
thedirectionofpeakradiationtothatofanisotropicsource.
Antennagainismorecommonlyquotedthandirectivityinan
antenna'sspecificationsheetbecauseittakesintoaccounttheactual
lossesthatoccur.

AntennaGain
68
AntennaGain=(P/Po)S=S0

AntennaGainsGi,Gd
69
Unlessotherwisespecified,thegainreferstothedirectionof
maximumradiation.
Gainisadimension-lessfactorrelatedtopowerandusually
expressedindecibels.
GiPowertheoreticalconcept,thereference
antennaisisotropic.
Gd-thereferenceantennaisahalf-wavedipole

TypicalGainandBeamWidth
70

PolarizationofAntennas
71
Thepolarizationofanantennainaspecificdirectionis
definedtobethepolarizationofthewaveproducedbythe
antennaatagreatdistanceatthisdirection

PolarizationofAntennas
72
Antennasarealsoclassifiedbytheirpolarization;thisdefinesthetypeofplane
wavepolarizationtheantennaismostsensitiveto.Thisisafundamentalantenna
concept.
Thissimpleconceptisimportantforantennatoantennacommunication.First,a
horizontallypolarizedantennawillnotcommunicatewithaverticallypolarized
antenna.Duetothereciprocitytheorem,antennastransmitandreceiveinexactly
thesamemanner.Hence,averticallypolarizedantennatransmitsandreceives
verticallypolarizedfields.Consequently,ifahorizontallypolarizedantennaistrying
tocommunicatewithaverticallypolarizedantenna,therewillbenoreception.
Ingeneral,fortwolinearlypolarizedantennasthatarerotatedfromeachotherbyan
angle,thepowerlossduetothispolarizationmismatchwillbedescribedbythe
PolarizationLossFactor(PLF):

EllipticalPolarization
73

Polarizationellipse
74
Thesuperpositionoftwoplane-wave
componentsresultsinanellipticallypolarized
wave
Thepolarizationellipseisdefinedbyitsaxial
ratioN/M(ellipticity),tiltangleandsenseof
rotation

LightFidelity(Li-Fi)isabidirectional,high-speedandfullyn

WirelessCommunication
Components
78
TypesofWirelessLANs:
ItispossibletoconfigureWLANsintodifferentarchitectures,
dependingontherequirementsofthesystem.Thephysical
architecturesincludethefollowing:
Adhoc
Infrastructure
Mesh

WirelessInfrastructureLANs:
79
Mostcompanies,public
hotspots,andhomeowners
implementinfrastructure
WLANs.
InfrastructureWLANstoextend
awirednet-work.
Oneormoreaccesspoints
interfacewirelessmobile
devicestothedistribution
system.
Eachaccesspointformsaradio
cell,alsocalledabasicservice
set(BSS).
WirelessInfrastructureNetwork

WirelessAdHocLANs
80
AdhocWLANs(sometimesreferred
-to-
Onlyrequire802.11clientradiosin
theclientdevicesthatconnecttothe
network.
NoaccesspointorWLANcontroller.
Thesenetworksrequireno
administrationandverylittlepre-
configuration.
WLANistosetthe802.11radioin
MicrosoftWindows-basedclient
devicestoadhocmode.
Note:The802.11standardreferstoanad
hocWLANasanindependentbasicservice
set(IBSS).

WirelessMeshLANs
81
Wirelessmeshnetworksmakeuseofmesh
nodes.
Meshnodesconnecttoeachotherwirelessly
ratherthanviaEthernet.
MeshnetworksavoidtheneedforEthernet
connections.
Ameshnetworkisbeneficialinareaswhereitis
notfeasibletoinstallatraditionalWLAN
consistingofaccesspoints.
Ameshnetworkoffersmultiplepathsfrom
sourcetodestination.
Intelligentroutingalgorithmsalloweachnodeto
makeadecisiononwhichpathtoforward
packetsthroughthenetworktoimprove
performance.
WirelessMeshNetwork

WirelessLANComponents
82
ClientDevices
ClientRadio
AccessPoints
Wi-FiRouters
MeshNodes
Antennas
RFAmplifiers
Repeaters
Bridges

AccessPoints
83
Theaccesspointistheprimary
componentofaninfrastructure
WLAN.
ItimplementsthecommonMAC
functionsandspecificphysical
layersandprovidesaconnection
toacommondistributionsystem
(generallyEthernet).

AccessPoints(continue)
84
An802.11AccessPointIncludesComponentsNecessarytoForman
InfrastructureWirelessLAN

85
AutonomousAccessPoints:
Anautonomousaccesspointisrelatively
intelligentandimplementsenoughfunctions
tobeabletointerconnectwithotheraccess
pointsviaconventionalEthernetswitches.
Theconfigurationoftheaccesspointsis
eitherdonethroughspecializedmanagement
soft-wareorbyloggingintoeachaccess
pointindividually.

86
Controller-BasedAccess
Points:
Asanalternativetotraditionalintelligentaccess
-
accesspointsthatimplementthebasic802.11
functions.
Theselightweightaccesspointsconnecttoa
WLANcontroller,whichprovidescentralized
enhancementsformanagement,security,and
performance.
Controller-BasedAccessPointsProvideCentralized
ManagementandControl

Wi-FiRouters
87
Aroutertransferspacketsbetween
networks.
Therouterchoosesthenextbest
linktosendpacketsontoreachthe
destination.
RoutersuseIPpacketheadersand
routingtables,andtheyuseinternal
protocolstodeterminethebestpath
foreachpacket.

Wi-FiRouters(continue)
88
AWLANrouteraddsthefunctionof
anaccesspointtoamulti-port
Ethernetrouter.Thiscombines
multipleEthernetnetworkswith
wirelessconnections,too.
AtypicalWLANrouterincludesfour
Ethernetports,an802.11access
point,andsometimesaparallelor
USBportsoitcanbeaprintserver.
Thisgiveswirelessusersthesame
abilityaswireduserstosendand
receivepacketsovermultiple
networks.

DifferencebetweenWLANroutersandAccess
Points
89
Accesspoints(AP)allow
wirelessclientsaccesstoa
singlenetwork.
AccesspointsignoretheIP
addressandforwardall
packets.
WLANroutersallowclientstobrowseseveral
differentnetworks.
ArouteralwaystakestheIPaddressintoaccount
tomakedecisionsonhowtoforward(route)the
packet.
WLANroutersimplementtheNetworkAddress
Translation(NAT)protocol,whichenablesmultiple
networkdevicestoshareasingleIPaddress,
generallyprovidedbytheInternetserviceprovider
(ISP).
WirelessLANroutershavethecapabilityto
provideport-basedcontrol,firewallmanagement,
andDynamicHostConfigurationProtocol(DHCP)
servicesforclientdevices.WirelessLANRoutersAreBeneficialforSharingaSingleOfficialIP
AddressandDistributingUniqueIPAddressestoEachClientRadio

MeshNodes
90
Ameshnodeistheprimarycomponentofameshnetwork.Each
meshnodeincludesanaccesspoint,whichimplements802.11
andinter-nodewirelessconnectivitytoenablecommunications
betweenmeshnodes.Clientdevicesequippedwithan802.11
radiodeviceconnecttotheaccesspointfunctionalityofthemesh
node.Asingleradiocanimplementboththeaccesspointand
theinter-nodewirelessconnectivity.
Inmulti-radioimplementations,theaccesspointcanoperate
independentlyonadedicatedRFchannel,whiletheinternode
communicationstakesplaceonadifferentRFchannel.Inthis
case,communicationsbetweentheclientdevicesandthemesh
nodecanoccursimultaneouslywiththeinternode
communications.Asaresult,multi-radiomeshnodesprovide
betterperformancethansingle-radiosolutions.

Repeaters
91
Arepeaterregeneratesradiosignalstoextend
therangeofaWLAN.
Arepeaterdoesnotphysicallyconnectbywire
toanypartofthenetwork.
Arepeaterreceivesradiosignals(802.11
frames)onaparticularRFchanneland
retransmitstheframeswithoutchangingthe
framecontentsonthesameRFchannel.
Arepeaterlocatedbetweenanaccesspointand
adistantuser.
Wirelessrepeatersareaneffectivesolutionto
overcomesignalimpairmentssuchasRF
attenuation.
Thewirelessrepeaterfillsinthecoverageholes.

Bridges
92
Abridgeprovidesamethodforconnecting
dissimilarnetworks.
Aremotebridgeconnectsnetworksthatare
notnexttoeachother,suchasnetworksin
differentbuildings.
Directionalantennasaremostoftenusedto
formapoint-to-pointorpoint-to-multipoint
network.
Workgroupbridgesareadvantageousfor
connectingoneormoreclientdevices(which
donothavewirelessclientradios)toaWLAN.
Thedevice,suchasaprinter,PC,orvideo
gameconsole,hasanEthernetportandno
802.11radiocard.

NetworkInfrastructure
Components
93
NetworkDistributionSystems
Switches
OpticalFiber
PoweroverEthernet
ApplicationConnectivitySoftware
TerminalEmulation
Browser-BasedApproaches
DirectDatabaseInterfaces
WirelessMiddleware

10MinsBreak

WirelessLANImplications
95
SecurityVulnerabilities
RadioSignalInterference
ImpactsofMulti-pathPropagation
RoamingIssues
BatteryLimitations
InteroperabilityProblems
InstallationIssues

96
Security
Vulnerabilities:
Networksecurityreferstotheprotection
ofinformationandresourcesfromloss,
corruption,andimproperuse.With
WLANs,securityvulnerabilitiesfallwithin
thefollowingareas:
Passivemonitoring
Unauthorizedaccess
Denial-of-serviceattacks

97
RadioSignal
Interference
Radiosignalinterferenceinvolvesthe
presenceofunwanted,interferingradio
signalsthatdisruptnormalWLANoperations.
Becauseofthe802.11MediumAccess
Control(MAC)protocols,aninterferingradio
signalofsufficientamplitudeandfrequency
canappearasabogus802.11station
transmittingapacket.Thiscauseslegitimate
802.11stationstowaitforindefiniteperiods
oftimebeforeattemptingtoaccessthe
mediumuntiltheinterferingsignalgoes
away.
MicrowaveOvenInterference
CordlessPhoneInterference
BluetoothInterference
NeighboringWirelessLAN
Interference

98
ImpactsofMultipathPropagation
Delayscausedbymultipathpropagationresultintheinformation
symbolsrepresentedintheradiowavesmearing.
Itisreferredtoasintersymbolinterference(ISI).
Becausetheshapeofthesignalconveystheinformationbeing
transmitted,thereceiverwillmakemistakeswhendemodulating
Ifthedelaysaregreatenough,biterrorsinthepacketwilloccur,
especiallywhendataratesarehigh.
Thereceiverwillnotbeabletodistinguishthesymbolsand
interpretthecorrespondingbitscorrectly.
Whenmultipathstrikesinthisway,thereceivingstationmust
haveanerror-checkingprocesstoensurethatthedataitreceives
isokay.
WLANsemployaprotocolthatcausesthesourcetransceiverto
retransmitthedataifthedestinationtransceiverdetectserrorsin
thedataatthedestination.

99
RoamingIssues:
The802.11radioinsidetheuserdeviceautomatically
roamsfromoneaccesspointtoanother,asneeded,to
provideseamlessconnectivity.
Ingeneral,wirelesstechnologiesprovideaccesspoint
roamingprotocols.
Theclientradiomakesadecisiontohandofftothe
nextaccesspointwhenretransmissionsandreceived
signallevelsindicateaneedtohandoff.
Adecisiontohandofftoosoongenerallyleadsto
skippingbackandforthbetweenaccesspoints.
Asaresult,clientradiomanufacturersgenerallychoose
todampenthehandoffprocessandwaituntilitis
absolutelynecessarytohandofftothenextaccess
point.

100
BatteryLimitations:
Theextraloadoftheradiocardinthesituationcansignificantlydecreasethe
amountoftimeavailabletooperatethecomputerbeforeneedingtorecharge
thebattery.
Theoperatingtime,therefore,mightdecreasetolessthananhouriftheclient
deviceaccessesthenetworkoftenorperformsotherfunctions,suchas
printing.
Tocounterthisproblem,mostimplementpowermanagementtechniquesin
theclientdevicesandradios.
Dozemode:keepstheradiooffmostofthe
timeandwakesitupperiodically.
Sleepmode:theradiowakesupand
sendsinformationifnecessary,butitisnot
capableofreceivinganyinformation.

101
InteroperabilityProblems:
Toensureinteroperabilitywith
WLANs,itisbesttoimplement
clientradiosandaccesspoints
(ifpossible)fromthesame
vendor.

102
InstallationIssues:
AWLANinstallationisnotaspredictable.
ItisdifficultifnotimpossibletodesignaWLAN
bymerelyinspectingthefacility.
Predictingthewayinwhichthecontourofthe
buildingwillaffectthepropagationofradio
wavesisdifficult.
Walls,ceilings,andotherobstaclesattenuate
thesignalsmoreinsomedirectionsthanothers
andevencauseradiowavestochangetheir
pathsoftransmission.
Eventheopeningofabathroomdoorcan
changethepropagationpattern.

103
SSID:
Theservicesetidentifier(SSID)isthenamegiventotheWLANthat
clientradiosmusthaveinordertoassociatewiththenetwork.Itis
generallybesttouseacommonSSIDforallaccesspointsto
improvetheabilityofclientdevicestoroam.
Eachaccesspointformsaradiocell,alsocalledabasicserviceset
(BSS),whichenableswirelessuserslocatedwithinthecellto
connecttotheaccesspoint

10MinsBreak

DesigningWirelessLAN
105
DesignWLAN:
1.NumberofDevices
2.AreaofCoverage
3.SecurityConsideration
4.HardwareConsideration

106
SiteSurvey
Inordertoimplementawirelessnetworkwithoptimalcoverage,
youhavetofirsthaveasolidunderstandingoftheradiofrequency
behavioronsite.
Awirelesssitesurveyisthebestwaytogainthisinformation,
becauseitwillrevealareasofchannelinterferenceandidentifyany
deadzones,helpingyouavoidproblemsasyoubuildthenetwork
andpreventobstaclesfornetworkusers.

107
SiteSurvey
Themaingoalofperformingawirelesssitesurveyistodetermine
twothings:
First,youwanttodeterminethefeasibilityofbuildingawireless
networkonyoursite.
thebestplaceforaccesspointsandotherequipmentsuchas
antennasandcables.
Asitesurveyalsohelpsyoutodeterminewhattypeofequipment
youwillneed,whereitwillgo,andhowitneedstobeinstalled.

108
Sitesurveytypes
Therearethreedifferenttypesofsitesurveyswidelyusedinthe
industry:
1.Passivesitesurvey.
2.Activesitesurvey.
3.Predictivesitesurvey.

109
Sitesurveytypes
Apassivesitesurveytoollistenstoexistingaccesspointsand,outsideyourmanagedinfrastructure,
forsignalstrength,interference,andAPcoverage.Passivesitesurveys,inwhichsurveyedWiFi
adaptersdon'tneedtoassociatetotheAPorSSID,giveagoodoverallpictureoftheRF
characteristicsofexistingwirelessnetworks.
Duringanactivesitesurvey,thesurveyWiFiadapterisassociatedtotheAP(s)andexchanges
packets.Thisallowsgatheringofverydetailedinformation.Actualnetworktraffic,throughputpacket
loss,andphysical(PHY)ratescanbecaptured.ActivesurveysarecommonlyusedfornewWLAN
deployments.
Apredictivesitesurveyisperformedwithoutanytypeoffieldmeasurements.ItusesRFplanning
softwaretoolsthatcanpredictwirelesscoverageoftheAPs.Toperformthissitesurvey,afloor-plan
drawing(AutoCAD,JPEG,PDF)isamust-have.Predictivesitesurveysareusedwhenthesiteor
buildingisnotyetbuiltandarehelpfulforbudgetingpurposes.

110
Sitesurveytypes
Thegoalofallofthesewirelesssitesurveysistoprovide
coverage.Beforeimplementingorattemptingtooptimizea
interference,APplacements,powerconsiderations,andwiring
requirementsthatareneeded.Awirelesssitesurveycan
provideallofthisinformationandmore,soyouhavethetools
youneedtodesign,implement,andoptimizeyourwireless
network.

113

114

119
450/255Mbps
80-90%
50%50%
65/30Mbps
110Mbps
15Mbps
125Mbps

120
200Users
400Devices
200Laptops300/150Mbps
200Tablets65/30Mbps
App=1Mbps
1/150=0.66%x200=133%
1/30=3.33%x200=666%
800%
/80%
10AP
5AP
multiradio

10MinsBreak

WLANSecurity
ThesecurityofawirelessLAN(WLAN)is
veryimportant,especiallyforapplications
hostingvaluableinformation.
Forexample,networkstransmittingcredit
cardnumbersforverificationorstoring
sensitiveinformationaredefinitely
candidatesforemphasizingsecurity.In
proactivelysafeguardthenetworkagainst
securityattacks.

WLANSecurity
SecurityElements
Encryption
Authentication
RogueAccessPoint
Detection
RFShielding
WirelessSecurityPolicies

WLANSecurity
Thefollowingaresecurityelementsthatyoushouldconsiderwhen
designingaWLANsystem:
Encryption:Encryptionscramblesthedatabitsofan802.11frameto
keepunauthorizedpeoplefromseeingtheactualinformationcontent
oftheframe.Youneedtochooseanencryptiontypethatprovidesan
adequatelevelofprotection.
Authentication:Authenticationensuresthatclientdevicesconnecting
toanaccesspointareauthorizedtoaccessprotectedresources.This
isnecessarytoprovidesolidsecurity.

WLANSecurity
Rogueaccesspointdetection:Sometimesemployeesorhackers
maypurposelyormistakenlyplantarogueaccesspointthatprovides
openaccesstoprotectedresources.Methodsmustbeinplaceto
locateandeliminaterogues.
Radiofrequency(RF)shielding:ConsiderusingRFshieldingpaint
andwindowfilmtohighlyattenuateradiowavesandminimizespillage
ofsignalcoverageoutsidecontrolledareas.
Securitypolicies:Definesecuritypolicies,suchas
encryption/authenticationmethods,thatbestsatisfyrequirements.

WLANSecurity
EncryptionProducesCiphertext,WhichIsaScrambledFormoftheActualInformationContentofthe
Frame
The802.11standardincludesseveraldifferent
methodsforencryptingdatathatissentoverthe
wirelessmedium.Thesemethodsincludethe
following:
WiredEquivalentPrivacy(WEP):WEPisthe
originalmethodforencrypting802.11dataframes.It
usesstatickeysthatmakeitvulnerableto
compromise.
TemporalKeyIntegrityProtocol(TKIP):TKIPisa
strongersecuritymethodthanWEPbecauseit
rotatesencryptionkeysregularly.
CCMP:Overall,CCMP,whichusesAdvanced
EncryptionStandard(AES),isthemostsecure
802.11encryptionmethod.

WLANSecurity
SecurityManagement
AfterdeployingaWLAN,youshouldimplementsecurityassessments
regularlytoensurethattheWLANcomplieswitheffectivesecurity
policies.
Formostsituations,thisisnecessarywhetherornotthenetwork
implementseffectivesecuritymechanisms.
Donotputtoomuchtrustinthedesignofasystem.
Itisbesttorunteststobecertainthatthenetworkishardenedenough
toguardagainstunauthorizedpersonsattackingcompanyresources.

WLANSecurity
SecurityManagement
WhenperformingaWLANsecurityassessment,considercompletingthestepsdiscussedinthe
following:
ReviewingExistingSecurityPolicies
ReviewingtheSystemArchitecture
ReviewingManagementToolsandProcedures
InterviewingUsers
VerifyingConfigurationsofWirelessDevices
InvestigatingPhysicalInstallationsofAccessPoints
IdentifyingRogueAccessPoints
PerformingPenetrationTests
AnalyzingSecurityGaps
RecommendingImprovements

TroubleshootingaWirelessLAN
TroubleshootingMethodology
Troubleshootinginvolvesthefollowingsteps:
Step1.Identifytheproblem.
Step2.Identifytheunderlyingcauseoftheproblem.
Step3.Fixtheproblem.
Step4.Documentthefix.

CommonProblemsinWLAN:
ConnectionProblems:
InsufficientSignalCoverage
AccessPointFailure
IncompatibleClientRadio
FaultyFirmware
IncorrectClientRadioConfiguration

CommonProblemsinWLAN:
PerformanceProblems:
InsufficientSignalCoverage
FaultyFirmware
Non-optimalClientRadioConfiguration
Non-optimalAccessPointConfiguration
MisalignedAntennas
HighUtilization

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