Deployment Guide: Higher Education

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Technical Guide

Site Survey

Site Survey Guide

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TableofContents

Introduction .................................................................................................................................3

TypesofSiteSurveys ....................................................................................................................3

SurveyRequirements....................................................................................................................5

EquipmentRequired.....................................................................................................................7

PerformingtheSurvey..................................................................................................................8

GettingStarted.............................................................................................................................9

Summary ....................................................................................................................................11

Wi‐FiTools..................................................................................................................................11

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Introduction Thepurposeofthisguideistoserveasanintroductionandeducationonthebasics,thevalues,andbest

practicesassociatedwithperformingWi‐Fisitesurveys.WewilldescribetheprocessXirrususesforsitesurveysanddemonstratehowthesesameprocessescanbeusedbyanyonewithreadilyavailabletools.

Poorlyperformedsitesurveyscanresultinnotonlycoveragegapsandreducedperformance,butalso

increasedcostsassociatedwithidentifyingandresolvingtheseissuesafterthefact.Thegoalofanysitesurveyistodeterminethenumberandlocationofaccesspoints(APs)requiredtomeetwirelessdesigngoals(suchascoverage,performanceandusercapacity).

Gettingthesitesurveyaccurateisjustasimportantasselectingtheproperhardware.Ifthesitesurveyis

toooptimisticandcallsfortoofewaccesspoints,thefinalinstallationwillyieldpoorcoverageand/orperformance.Thisinturnwillrequireafollow‐upsurveytodeterminewhatchangesmayberequiredtothenumberorlocationofdeployedAPs.TheendresultwillbeincreasedcostsnotonlyinadditionalAPs,but

alsotheassociatedcostsofpullingcable,equipment,contractors,andinstallationeffort.Conversely,ifthesurveyistooconservative,moreaccesspointsthanareneededwillbespecifiedandagainmoneyiswastedonunneededequipmentandlaborcharges.

Types of Site Surveys Active vs. Predictive Therearetwoprimarymethodsinwhichsitesurveyscanbeperformed:ActiveandPredictive.Activesite

surveys,alsocalledlivesurveysuseanactivelytransmittingaccesspointandaWi‐FienabledlaptoporothertooltomeasureWi‐Fisignalstrengthintheactualenvironmenttodeterminehowmanyandwhereaccesspointsarerequired.Predictivesitesurveysusesoftwarepackagestoemulatetheenvironment.Floorplans

ofthesiteareimportedandallowtheusertoassignattenuationvalues(howmuchRFenergyisabsorbed)foreachwallandobjectinthebuilding(mosttoolstypicallyhaveadatabaseofmaterialstochoosefrom),theapplicationwillthenpredictthenumberandlocationofaccesspointsrequiredtomeetthedesired

coverageandperformancegoals.

Active site surveys–measurestherealperformanceofeachaccesspointlocationandinnatelytakesintoaccountthephysicalcharacteristicsandcontentsofthebuilding.Thereisnoneedtoestimatethedensityofthewallsorfloors.Anactivesitesurveyisalsoabletodetectanysourcesofinterferenceand

applythisinformationtodetermineSNR(signaltonoiseratio).Thistypeofsurveynotonlyprovidesthemostaccurateperformanceinformationforeachaccesspoint,italsoallowsforthephysicalinspectionofthesitetoassuretheaccesspointcanbemountedintheselectedlocation.Thedownsideofthistypeof

surveyisitislaborintensive,requiresphysicalaccesstothebuildinganddemandsahigherlevelofRFknowledgetoperform.

Predictive site surveys–maytakelesstimebutstillrequire“seattime”infrontofacomputerprogramversusthe“legtime”neededforanactivesurvey.Asthenameimpliesthesoftwareperformsapredictive

analysisofthebuilding,oncefloorplansareimporteditusesindustrydefinedattenuationvaluesforwalls,

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doors,windows,etc.ThedifficultyhereisthecommonGIGO(GarbageIn‐Garbageout)problemassociatedwithtryingtoaccuratelymodelthecontentsandmakeupofthebuilding(especiallyonesthathavechanged

orremodeledovertime).

SurveyComparison

Active(live)Survey PredictiveSurvey

SurveyEffort Higher PotentiallyLower

AccessPointPlacement ExactLocationschosen Finallocationsstillneedbechosen

WirelessCoverage Measured/Known Predictive:MayrequiremoreAPs

WirelessPerformance Measured/Known Estimated:MayrequiremoreAPs

CablingandEquipment TypicallyAccurate Mayrequirecablestobeaddedormoved

Installation Simplified MayrequiremovingAPsoraddingmoreAPs

Remotevs.On‐SiteSurvey

AlthoughthefollowingdiscussiongoeshandinhandwithActivevs.Predictivesurveys,itisimportanttoidentifytheadditionalvaluebeyondRFanalysisofanon‐siteactivesurveyvs.apredictivesoftwareanalysis.

Thekeypointistounderstandthevalueofwalkingthefacilityasthesurveyisperformedandknowingwhattolookfor.

Theactivesurveynotonlyprovidesthemostaccurateperformanceinformationforeachaccesspoint,italsoallowsforthephysicalinspectionofthesitetoassuretheaccesspointcanbemountedintheselected

location.IfAPplacementisbasedjustonthemarkingonafloorplantheactualinstallersmayfindthelocationunacceptableforinstallation,asitmaynotbephysicallymountableatthepredictedlocation.

Aphysicalwalkthroughoftheinstallationsiteenablesidentificationandaddressingofthefollowingtypesofissuesbeforeinstallationday,wheredelayscanbecostly:

Identifying AP locations – Thisiswillgreatlyassistthosepullingdata/powercablingandavoidcostlychanges.Physical restrictions–AretheremountingissuesthatpreventanAPbeinginstalledwhereitwouldbestbelocated,suchaslighting,airconditioningducts,sprinklers,appropriatemountingpoints,etc.Italsoallowsinstallerstoidentifyalltoolsandanyspecialmountinghardwarerequiredfortheinstall.RF Interference issues–Aretherenearbynon‐802.11devicesthatemitRFenergy(microwaveovens,medicalequipment,airconditioningunits,etc.)thatmayinterferewiththeproperoperationoftheAP?Inaddition,whatotherWi‐Finetworksarelocatedintheenvironment?Ifother5GHznetworksarenearby

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thereistypicallysufficientavailablechannelstoavoidinterference,howeverwith2.4Ghz(11b/g)thereareonly3usablechannelsandanearbynetworkalsousingthesecouldresultininterference.AtthispointthereshouldbesomediscussionbetweenITstaffstosetchannelsandpowertoavoidinterferencethatcoulddegradebothnetworksperformance.Aesthetic Issues–Aretherecorporatepoliciesthatrestrictthelocation,color,shape,etc.,oftheAccessPoint.Regulations/Codes/Policies–Aretheirspecificrulesthatthedeploymentmustconfirmto,suchasACpowerdistribution,cablingruns,RFpowerlimits,plenumrating,orotherissues.Arrivingonsitewithinappropriatecomponentscanaddexpensivedelays. Flexibility of environment–Manyenvironments‐especiallyschools,conferencecenters,warehouses,manufacturingfacilities–canbeveryphysicallydynamic.Fromonedaytothenext,wallscanbemoved,equipmentshuffled,racksrearranged,etc.Avisualwalkthroughandon‐sitediscussioncanidentifyandaddresstheseissuespriortotheinstallandavoidpostinstallcomplications.

Bottom line–Apredictivesurveyisofteneasiertoaccomplishbuthasthepotentialtomaketheactual

installmorecomplexduetounknownsthatcouldbeencountered.Anactivesitesurveythatincludesaphysicalwalkthroughismorecomplex,howeverwillmaketheinstallgosmootherbyidentifyingpotentialissuesupfrontandultimatelyresultinamoresuccessfuldeployment.

Survey Requirements Beforestartingasitesurvey,itisofcriticalimportancetodefinethepurposeofthesurvey.Itmayseemverybasictoincludethisasarequirement,howeveritisamazinghowmanysurveysareconductedwiththefocusonlyonRFcoverageandnoconsiderationgiventothereasonsforinstallingWi‐Fiinthefirstplace.

Thefollowingcomponentsshouldbeconsideredbeforeselectingavendororperformingasurveyastheywillhelpdeterminetheproductandsurveyrequirements.Business Requirements–Whatisthepurposeofadding/upgradingtheWi‐Fiservices?IsthegoaltojustaddWi‐Fihotspots,connectivityintheconferencerooms,orisitabuilding/campus‐widepervasiveWi‐Fiservicethatprovidesseamlesscoverageandroamingthroughouttheenterprise.Theanswertothisquestionwillhelpdeterminethevendors,productsandWi‐Fiarchitectureyouselect.Application Requirements–BandwidthandQoScapabilitiesdefinetheproductspurchased,howeverminimumRFsignalstrengthmustalsobeconsideredforvoiceoverWi‐Fisolutions.ThemajorityofWi‐Fiphonevendorsrequirea‐68dBmRSSI(receivedsignalstrengthindicator)orstrongersignal.Surveyingtothislevelavoidshavingtore‐surveyandaddAPs/cablingatalatertime.Security Requirements–Anothertopicoftenoverlookedduringasitesurveyissecurity.ControllingtheamountofRFenergytransmittedbeyondtheenterpriseboundaries(parkinglots,etc.)shouldalwaysbeaconsideration.WithproperAPplacement,powerlevels,anduseofdirectionalantennas,RFleakagecanbeminimized.ToclearlydefinetheedgeofRFcoverage,varypowerlevelsandrecordsignalstrengthreadingsoninsideandoutsidewallsoffacility.DirectionalantennacanalsobeusedforRFshaping.

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Coverage vs. Capacity–Mostvendorsofferseparatesurveyproceduresforcoverageorcapacitymodels.CoveragesurveysaredesignedtogenerateasolutionwiththeminimumnumberofAPstoguaranteeclientassociation.Capacitysurveysaredesignedtosupportlargernumbersofstationsandofferhigherdataratestoclients;thesetypicallygroupmoreAPsinasinglearea,resultinginsmallercellsandwithmoreradiochoicesforclients.Theresultistypicallystrongersignalstrengthconnectionsforclients,whichresultsinhigherdatarates.Cell Size Planning‐Wi‐Fiinthe5GHzband(802.11a/n)hasslightlysmallercellsthanWi‐Fiinthe2.4GHzband(802.11b/g/n).Designfor5GHzanditwillprettymuchensurecoverageforall802.11a/b/g/nclients.LargercellssizescanreducenumberofAPsrequired,butcouldresultinclientconnectivityproblems.Choosing Between 2.4 GHz or 5 GHz–BothbandsarecommonlydeployedinWi‐Finetworkstodayanditisstronglyrecommendedtoperformthesurveyforbothbands.

Wireless Bridging (WDS) Requirements–WillAPtoAPwirelessbridgingbeused?Thisquestionmaycomeupinoutdoordeployments,inwarehouseswhereintra‐APdistancescouldexceed100metersorevenbuilding‐to‐buildinglinks.Aspartofthesurvey,examinepoint‐to‐pointpathloss.Specialattentionshouldbepaidtoanytreesorfoliageinthepathasseasonalgrowthcouldimpactthelink.Wired Infrastructure –Don’toverlooktheexistingwiredinfrastructure,asitscapabilitiesorlackthereofcanseverelyimpactWi‐Fiperformance.Forexampleifdeploying802.11nWi‐Fi,theuplinkswillrequireGigabitlinks.VerifythecableplantandswitchesarecapableofGigabitEthernetorifawirednetworkupgradewillberequired.Inaddition,verifyAPpoweringoptions.IfPoEwillbeused,verifythatneworexistingPoEproductsprovidesufficientpower(802.3af,802.3at,orother)fortheWi‐Fitobedeployed(forexample802.11nrequiresincreasedpower). The 802.11n Site Survey –Theintroductionof802.11nhasaddedsomeconfusionandcaveatstothetraditionalsitesurvey.802.11nisnotabouthighertransmitpower,butaboutbetterreceiversensitivity(abilitytolisten).802.11nrangeimprovementsrequire11nradiosatbothendsoftheconnection‐thestationandAccessPoint.Themajorityofnetworksdeploymentswillincludeamixofclienttypes(802.11nandnon‐802.11n)andcellsizesshouldthereforeremainthesame.Somerecommendationsforperforming11nsurveysinclude:

• Alwayssurveyforboth2.4/5Ghz‐Thisisthesameasfor802.11a/b/gsurveysandisrecommendedsobothbandswillbeproperlysupported

• Usean802.11abgadapterforsitesurvey–Thisisrecommendedevenfor11nAPsassupportforlegacy802.11a/b/gdeviceswillcontinueforsometime

• Usean802.11abgnadapteronlyifallnetworkdeviceswillbe11ncapable–Althoughsomenetworksmaymeetthiscriteria,thevastmajorityofWi‐Finetworkswillbemixed11a/b/g/nenvironmentsforsometime

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Equipment Required Thissectionidentifiesspecificequipment,tools,andsoftwareXirrusrecommendsforperformingaprofessionalqualitysitesurvey.

Array/APs/Radios: UsethetypeofArrayorAPtobedeployed.Allsurveysshouldbeperformedusingproductsidenticaltothosethatwillbeinstalled;thisapproachhelpstoguaranteeinstalledcoveragematchesthatofthesurvey.Usingdifferentproductsforsurveyandproductioncouldresultinsignificantvariabilityinactualcoverage.

Support Equipment:

• Multiplecopiesofthefloorplanshouldbeavailabletotrackmountinglocations,recordobstructions,andindicatemountingoptionsandgeneralnotetaking.

• SurveysshouldbeconductedwithArrays/APslocatedascloseaspossibletowheretheywillbe

installed.XirrususestripodstolocateArrays.IfusingstandardAPs,itisrecommendtopolemountthemforeasierplacement.

• GeneralpurposeequipmentsuchasACextensioncords,Ethernetcabling,consolecables,ladders,flashlights,etc,shouldbeavailabletoassistonthesurvey.

• Acameraisdesirabletorecorduniquemountingobstaclessoappropriatemountscanbedefined.• Someformoflocationidentifiers(e.g.stickers)toindicatewhereArray/APswillbeplaced.

Software/Firmware Tools

Alaptopwiththefollowingtoolswillberequiredforthesurvey:• RFsurveytool,forexampleAirMagnetSurveyorsimilar.Alternativelyformoresimplesurveys,free

toolsthatreadWi‐Fisignalstrengthcanbeused.TheXirrusWi‐FiMonitorgadgetisafreetoolthatcanbeusedandisavailableathttp://www.xirrus.com/library/wifitools.php.

• OptionallysomeformofRFmonitoringtoolthatwillidentifynearbyAPsandperformSpectrumAnalysistoidentifypotentialnoisesources.TheXirrusWi‐FiArrayhasthesecapabilitiesbuilt‐inandcanbeleveragedduringthesurveyprocess.

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Performing the Survey ThissectiondescribesproceduresusedbyXirrustoperformasitesurvey.UsingthismethodologyandreadilyavailableWi‐Fitools,anITadministratorwithamoderatedegreeofWi‐Fiknowledgecanperformareasonablyaccuratesurveyoftheirown.Aspreviouslydiscussed,thesitesurveyisoneofthemostcrucialstepsinasuccessfulWi‐Finetworkdeployment.WithmanytechniquescommonlyusedforWi‐Fisitesurveysandthemanymodesof802.11a/b/g/n,ensuringthesurveyisdonerightismoreimportantthanever.Apoorlyperformedsitesurveydoesnotonlyimpactyounetworktoday,itcanresultinacostlyredesignwhenit’stimetoupgradeto802.11n.Componentsofaprofessionalsitesurveyperformedbyvendor‐qualifiedindividualsshouldinclude:

• Completeon‐sitesurveyofallareastobecovered,usingsameproductsthatwillbedeployed.

• On‐siteRFspectrumanalysistoidentifypotentialinterferenceissues.

• PostsurveyanalysisandreportincludingcoveragemapsandRSSIvalues.

• PostinstallsurveytoconfirminstalledWi‐Fiequipmentmeetsproposalrequirements.

Recommended Site Survey Parameters

• SignalStrength‐70dBmRSSI(orstronger)inallareastosupportfulldatarates• SignalStrength‐68dBmRSSI(orstronger)inallareastosupportWi‐Fivoicehandsets• Clientshouldbeabletoseeatleast2‐3radiosateverylocationthesesignallevels

Before Arriving On-site

• DiscussbusinessrequirementswithallwhohaveastakeintheWi‐Fisolution• Obtaindigitalfloorplansoffacilitytobecovered(e.g..jpg,.bmp,.png)• Ensureaccesswillbeavailableonthedayofthesurveytoallarea,orarepresentativesubsetof

area,thatistobecoveredbyWi‐Fi

Tips Before Starting

Thissectionincludesanumberoftipsandrecommendationstohelpensureasuccessfulandaccurate

survey.• ItisagoodideatodeployasmanyArraysasreasonable,asthiswillsimplifythesurveyprocessand

providesuperiorsurveymeasurementsvs.justusingjustoneArrayandcontinuallymovingandtakingmeasurements.

• SetupTripod/ArrayinsuchawaythatitcorrectlyrepresentshowtheArraywillbemounted• ForeachArrayandArraylocationduringthesurvey,useaseparateSSIDsospecificcoverageofeach

Arraycanbeeasilydistinguished.• SetArraybeaconrateto20ms‐thisenablesthesurveysoftwaretoreceivemanymorebeacons.

Afterthesurvey,don’tforgettoresetbeaconratetodefault.• Performsurveysunderworst‐caseusageconditionsfortheenvironment,forexampledoorsclosed,

curtainsdrawn,etc.• Beawarethateachclient(laptop/Wi‐Ficard/driver)willhaveslightlydifferentreadings.Thisisa

goodreasontobeconservativewhenperformingWi‐Fisurveys.

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• Performthesurveyatboth5GHzand2.4GHz.• Donotsurveyfor802.11nonlyunlessyouare100%surenolegacy(802.11a/b/g)clientswillbe

supported(notcommon)• Takemeasurementswhereuserswillbelocated:desks,tables,etc.• Takemultiplereadingsineachroom• ConsideradditionalsignalattenuationifArrays/APswillbeplacedinenclosuresoraboveceilings.• Inmulti‐floorbuilding,checkforfloor‐to‐floorbleed‐through.Ifsignificant,planforcoverageof

areasfromArrays/APsplacedabove/belowagivenfloor.StaggerthefinalplacementsoftheArrays/APsbetweenfloorstoaccountforthis.

• Constantlyconsiderinstallationconcernswhensurveyingandprepareaccordingly• Don’trush!

Getting Started ThissectiondemonstratesaprocessthatXirrushasfoundtobesuccessfulandaccurate.

1. StartwithlaptopinafarcornerofthefacilityandtheArray/APplacednearby.MovetheArray/APawayfromthelaptopuntilsignalstrengthdropsto,butnotunder,thespecifiedRSSIvalue(e.g.‐70)

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2. FindtheotheredgeofcoverageareabymovingthelaptopawayfromtheArray/APandsurveying

untilthesignalstrengthdropsto,butnotbelow,thespecifiedsignalstrengthvalues.

3. ThisdefinesthecoverageareaforthesingleArray;identifythelocationbyrecordingtheinformationonafloorplanandalsowithsomeformofphysicaltagging(e.g.stickersontheceiling)toidentifytheexactlocationwheretheArraywillbelocated.

4. Continuetorepeatthisprocessasyoumoveacrossthebuildinguntilthecompletefacilityhasbeensurveyed.Ifsurveyingamulti‐storyfacility,makesuretoverifyfloor‐to‐floorcoveragebeforeturningmovingtheArray.

5. UsetheArray’sRFMonitor/IntrusionDetectionfunction(orsimilartool)tofindotherAPsinthearea.AlldetectedAPsshouldbeidentifiedasknownorunknowndevicesandconsideredintheoverallsurvey.

6. UsetheArray’sRFMonitor/SpectrumAnalyzerfunction(orsimilartool)toidentifysourcesofinterference,either802.11co‐channelinterferenceornon‐802.11noise.Onceanoisesourceisidentified,defineaplanforinterferenceavoidance.Insomecases,discussionswithneighboringWi‐

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FinetworksITstaffshouldbesetuptoarrangeforchannelplanningandpowersettingcoordination.

7. Finally,sharecompletesurveyinformationwithallstakeholders.Discusscoveredareas,RSSIvalues,weakspotsandindicatehowmanyradiosareavailabletomobileusersthroughoutthefacility.Thislastpartiskeyaswerecommendatleast2‐3strongradiostoallclientstoprovideresiliencyandtoreducethepossibilityofasingleradiofailuretakingdownanyarea.

Exampleof‘Active’SiteSurveyresults(usingAirMagnettool)

Summary PredictivesitesurveysmaybeacceptableinsomelesscomplexWi‐Fideployments,howeverthelargerandmorebusinesscriticalyourWi‐Fiprojectis,themoreessentialanactivesitesurveybecomes.RollingoutWi‐Fiforalargeofficebuildingorcampusenvironmentmandatesanaccuratesitesurvey.Withlargeprojects,

evenbeingoffbyasmallpercentagecouldresultinunacceptableadditionalcostsassociatedwithadditionalequipment,cabling,andmanpowerrequirements.

Anactive,on‐sitesurveyusingtriedandtruebestpracticemethodologiesisthemostaccuratetypeofsurveyandXirrusstronglyrecommendsitbemadearequirementofanyWi‐Fideployment.

FinalThought‐YouarebettingthesuccessofyourWi‐Finetworkonthesurvey,andmaybeyourjob!

Wi-Fi Tools • Wi-Fi Basics FAQ – www.xirrus.com/library/faq.php

o Useful Wi-Fi FAQ for understanding the components, requirements and goals associated with performing a site survey

• Wi-Fi Tools – www.xirrus.com/library/wifitools.php o XirrushasassembledseveralusefulWi‐Fitoolsfoundtobeofgreatvalueinplanning,

deploying,andmanagingWi‐Finetworks. • Xirrus Wi-Fi Reference Posters –

www.xirrus.com/posters o Educational/reference

information on Wi-Fi

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• Xirrus Wi-Fi Widgets/Gadgets – www.xirrus.com/library/wifitools.php o The Xirrus Wi-Fi Monitor provides detailed information about surrounding Wi-Fi

networks and your laptop’s current Wi-Fi connection, including SSID, signal strength, IP address, MAC address, security level, vendor, and network type. This free tool can be used to perform simple site surveys.

Guide