CWNA Guide to Wireless LANs, Second Edition Chapter Seven Conducting a Site Survey

CWNA Guide to Wireless CWNA Guide to Wireless LANs, Second EditionLANs, Second Edition

Chapter SevenChapter Seven

Conducting a Site SurveyConducting a Site Survey

Wireless NewsWireless News

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EarthLink Launches The City Of EarthLink Launches The City Of Anaheim Municipal Wireless NetworkAnaheim Municipal Wireless Network• Will provide inexpensive, high-speed Will provide inexpensive, high-speed

Internet access for the City’s residents, Internet access for the City’s residents, businesses, visitors and municipal businesses, visitors and municipal employees. employees.

• $3.95 – 1-hour of access$3.95 – 1-hour of access• $15.95 – 3-days of access$15.95 – 3-days of access• $21.95 per month$21.95 per month

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Wireless NewsWireless News Chamber Releases RFP for OKC Wi-Fi Chamber Releases RFP for OKC Wi-Fi

Network Network • Oklahoma City Chamber today (6/28/06) Oklahoma City Chamber today (6/28/06)

released a Request for Proposals (RFP) to released a Request for Proposals (RFP) to create a public-access Wi-Fi network in several create a public-access Wi-Fi network in several "Hot Spots" in Oklahoma City, including the "Hot Spots" in Oklahoma City, including the Central Business District, Bricktown, the Arts Central Business District, Bricktown, the Arts District/Myriad Gardens, the Oklahoma City District/Myriad Gardens, the Oklahoma City National Memorial, the Oklahoma River (from I-National Memorial, the Oklahoma River (from I-35 to Broadway) and the Native American 35 to Broadway) and the Native American Cultural Center. Cultural Center.

• OKC State Fair Park and Will Rogers IAP OKC State Fair Park and Will Rogers IAP already have WiFialready have WiFi

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FCC Readies To Auction Wireless FCC Readies To Auction Wireless SpectrumSpectrum• To be held August 9To be held August 9thth

• FCC has received 252 applications to bid FCC has received 252 applications to bid for advanced wireless spectrum for advanced wireless spectrum

Verizon, Cablevision, Cable-One, T-Mobile, Verizon, Cablevision, Cable-One, T-Mobile, Cingular, etc.Cingular, etc.

• Some 1,200-plus licenses, reclaimed from Some 1,200-plus licenses, reclaimed from government use, are up for grabs, enough government use, are up for grabs, enough to build a national network. to build a national network.

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New York State Parks go wirelessNew York State Parks go wireless• The first of the 18 locations was The first of the 18 locations was

activated last Thursday. activated last Thursday. Eight hot spots will be in Central ParkEight hot spots will be in Central Park Two hot spots in Prospect Park in BrooklynTwo hot spots in Prospect Park in Brooklyn All will be free/open!All will be free/open!

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ObjectivesObjectives

Explain what a site survey isExplain what a site survey is Describe the tools used in a site Describe the tools used in a site

surveysurvey Describe how to perform a site surveyDescribe how to perform a site survey

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What is a Site Survey?What is a Site Survey?

When installing a WLAN for an organization, When installing a WLAN for an organization, areas of dead space might not be toleratedareas of dead space might not be tolerated• Ensure Ensure blanket coverageblanket coverage, meet , meet per-user per-user

bandwidthbandwidth requirements, requirements, minimize “bleeding”minimize “bleeding” of of signalsignal

FactorsFactors affecting wireless coverage goals: affecting wireless coverage goals:• Devices emitting RF signalsDevices emitting RF signals• Building structure (walls, construction materials)Building structure (walls, construction materials)• Open or closed office doorsOpen or closed office doors• Stationary versus mobile machinery/equipmentStationary versus mobile machinery/equipment• Movement of mobile walls (e.g., cubicles)Movement of mobile walls (e.g., cubicles)

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What is a Site Survey? What is a Site Survey?

FactorsFactors affecting wireless coverage goals: affecting wireless coverage goals:• Expansion of physical plant or growth of Expansion of physical plant or growth of

organizationorganization• Existing WLANsExisting WLANs

Both inside organization, and within nearby Both inside organization, and within nearby organizationsorganizations

Site survey:Site survey: Process of planning a WLAN Process of planning a WLAN to meet design goalsto meet design goals• Effectiveness of a WLAN often linked to Effectiveness of a WLAN often linked to

thoroughness of the site surveythoroughness of the site survey

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Design goals for a site survey:Design goals for a site survey:• Achieve Achieve best possible performancebest possible performance from WLAN from WLAN• Certify that installation will Certify that installation will operate as promisedoperate as promised• Determine Determine best locationbest location for APs for APs• Develop networks optimized for variety of Develop networks optimized for variety of

applicationsapplications• Ensure Ensure coveragecoverage will fulfill organization’s will fulfill organization’s

requirementsrequirements• Locate unauthorized APsLocate unauthorized APs

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What is a Site Survey? What is a Site Survey? Design goals for a site survey (continued):Design goals for a site survey (continued):

• MapMap nearby wireless nearby wireless networksnetworks to determine to determine existing radio interferenceexisting radio interference

• Reduce radio interferenceReduce radio interference as much as possible as much as possible• Make wireless network secureMake wireless network secure

Survey provides realistic understanding of Survey provides realistic understanding of infrastructure required for proposed wireless infrastructure required for proposed wireless linklink• Assists in predicting Assists in predicting network capabilitynetwork capability and and

throughputthroughput• Helps determine exact Helps determine exact location of APslocation of APs and power and power

levels requiredlevels required

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When to perform a site survey:When to perform a site survey:• Before installing a new wireless networkBefore installing a new wireless network• Before changing an existing wireless Before changing an existing wireless

networknetwork• When there are significant changes in When there are significant changes in

personnelpersonnel• When there are changes in network When there are changes in network

needsneeds• After making physical changes to a After making physical changes to a

buildingbuilding

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Site Survey Tools: Wireless ToolsSite Survey Tools: Wireless Tools

Most basic tool is AP itself:Most basic tool is AP itself:• Position AP in various locations, monitor signal as Position AP in various locations, monitor signal as

you move you move • APs should have ability to adjust output powerAPs should have ability to adjust output power• APs should have external antenna connectorsAPs should have external antenna connectors

Test effectiveness of different antenna types in different Test effectiveness of different antenna types in different situationssituations

• May need DC-to-AC converter for testingMay need DC-to-AC converter for testing Notebook computer with wireless NIC also Notebook computer with wireless NIC also

essential for testingessential for testing• Previously configured and testedPreviously configured and tested

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Site Survey Tools: Wireless ToolsSite Survey Tools: Wireless Tools

Figure 7-1: Adjusting AP power levels

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Site Survey Tools: Wireless Site Survey Tools: Wireless ToolsTools

Figure 7-2: External antenna connectors

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Site Survey Tools: Site Survey Tools: Measurement ToolsMeasurement Tools

Site Survey Analyzers: Site Survey Analyzers: Specifically Specifically designed for conducting WLAN site surveysdesigned for conducting WLAN site surveys• Software often built into APSoftware often built into AP• Receive Signal Strength Indicator (RSSI)Receive Signal Strength Indicator (RSSI)

valuevalue• Full-featured site survey analyzer software Full-featured site survey analyzer software

settings:settings: Destination MAC AddressDestination MAC Address Continuous Link TestContinuous Link Test Number of PacketsNumber of Packets Packet SizePacket Size Data RetriesData Retries

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Site Survey Analyzers (continued):Site Survey Analyzers (continued):• Full-featured site survey analyzer software Full-featured site survey analyzer software

settings (continued):settings (continued): Data RateData Rate Delay Between PacketsDelay Between Packets Packet Tx TypePacket Tx Type

• Unicast or multicastUnicast or multicast Percent Success ThresholdPercent Success Threshold

• Basic survey analyzer software contains Basic survey analyzer software contains far fewer featuresfar fewer features

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Figure 7-3: Full-featured site survey analyzer software setup

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Figure 7-4: Full-featured site survey analyzer software results

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Figure 7-6: Basic site survey analyzer software results

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Spectrum Analyzers: Spectrum Analyzers: Scan radio Scan radio frequency spectrum and provides frequency spectrum and provides graphical display of resultsgraphical display of results• Typically measure signal-to-noise ratioTypically measure signal-to-noise ratio• Single-frequency analyzers measure Single-frequency analyzers measure

signal-to-noise ratio at specified signal-to-noise ratio at specified frequencyfrequency

• Helpful in identifying interference Helpful in identifying interference problemsproblems

Thus, helps properly position/orient APThus, helps properly position/orient AP

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Site Survey Tools: Site Survey Tools: Measurement Tools (continued)Measurement Tools (continued)

Figure 7-7: Single-frequency analyzer

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Figure 7-8: Spectrum analyzer

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Network Analyzers: Network Analyzers: Can be used to Can be used to pick up packets being transmitted by pick up packets being transmitted by other WLANs in area other WLANs in area • Provide additional information on Provide additional information on

transmissionstransmissions• Packet sniffers or protocol analyzersPacket sniffers or protocol analyzers• Not used in placement of APNot used in placement of AP

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Site Survey Tools: Site Survey Tools: Documentation ToolsDocumentation Tools

Create a “hard copy” of site survey results Create a “hard copy” of site survey results • Make available for future referenceMake available for future reference• No industry-standard form for site survey No industry-standard form for site survey

documentationdocumentation Site survey report should include:Site survey report should include:

• Purpose of reportPurpose of report• Survey methodsSurvey methods• RF coverage details (frequency and channel RF coverage details (frequency and channel

plan)plan)• Throughput findingsThroughput findings• Sources of interferenceSources of interference

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Site survey report should include Site survey report should include (continued):(continued):• Problem zonesProblem zones• Marked-up facility drawings with access point Marked-up facility drawings with access point

placementplacement• Access point configurationAccess point configuration

Use building layout blueprints as toolsUse building layout blueprints as tools Advisable to create database to store site Advisable to create database to store site

survey information and generate reportssurvey information and generate reports

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Figure 7-9: Sample site survey form

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Performing a Site Survey: Performing a Site Survey: Gathering DataGathering Data

Obtaining Business Requirements: Obtaining Business Requirements: Determine business reasons why WLAN Determine business reasons why WLAN being proposed or extendedbeing proposed or extended• If this step skipped, almost impossible to If this step skipped, almost impossible to

properly design and implement the networkproperly design and implement the network• Primary data gathering method is interviewingPrimary data gathering method is interviewing• Must determine type of mobility required Must determine type of mobility required

within organizationwithin organization• Must determine per-user bandwidth Must determine per-user bandwidth

requirementsrequirements May be different “types” of users with different May be different “types” of users with different

bandwidth requirementsbandwidth requirements

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Performing a Site Survey: Performing a Site Survey: Gathering DataGathering Data

Defining Security Requirements: Defining Security Requirements: Consider Consider type of data encryption and type of type of data encryption and type of authentication that will take place across authentication that will take place across WLANWLAN• Consider existing security policies and proceduresConsider existing security policies and procedures

Gathering Site-Specific Documentation:Gathering Site-Specific Documentation:• Blueprints, facility drawings, and other documentsBlueprints, facility drawings, and other documents

Show specific building infrastructure componentsShow specific building infrastructure components

• Inspecting the siteInspecting the site Document changes to blueprints and get visual Document changes to blueprints and get visual

perspectiveperspective

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Performing a Site Survey: Performing a Site Survey: Gathering Data (continued)Gathering Data (continued)

Gathering Site-Specific Documentation Gathering Site-Specific Documentation (continued):(continued):• Behind-the-scenes site inspectionBehind-the-scenes site inspection

May require ladder, flashlight, and an escortMay require ladder, flashlight, and an escort Documenting Existing Network Documenting Existing Network

Characteristics: Characteristics: New or expanded WLAN New or expanded WLAN will “dovetail” into network already in placewill “dovetail” into network already in place• Determine degree to which WLAN will interact Determine degree to which WLAN will interact

with other wired networkswith other wired networks• Legacy systems may require additional Legacy systems may require additional

equipment to support WLANequipment to support WLAN

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Performing a Site Survey: Performing a Site Survey: Performing the SurveyPerforming the Survey

Collecting RF Information:Collecting RF Information:• Note objects in and layout of roomNote objects in and layout of room

Use digital cameraUse digital camera

• Position APPosition AP Initial location will depend on antenna typeInitial location will depend on antenna type Document starting position of APDocument starting position of AP

• Using notebook computer with site survey Using notebook computer with site survey analyzer software running, walk slowly away analyzer software running, walk slowly away from APfrom AP

Observe data displayed by analyzer programObserve data displayed by analyzer program• Data rate, signal strength, noise floor, and signal-to-Data rate, signal strength, noise floor, and signal-to-

noise rationoise ratio

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Figure 7-10: Position of APs

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Collecting RF Information (continued):Collecting RF Information (continued):• Continue moving until data collected for all Continue moving until data collected for all

areasareas• Data collected used to produce:Data collected used to produce:

Coverage pattern:Coverage pattern: Area where signal can be Area where signal can be received from the APreceived from the AP

Data rate boundaries: Data rate boundaries: Range of coverage for a Range of coverage for a specific transmission speedspecific transmission speed

Throughput:Throughput: Number of packets sent and received Number of packets sent and received and data rates for eachand data rates for each

Total transmission range:Total transmission range: Farthest distance at Farthest distance at which signal can be received by wireless devicewhich signal can be received by wireless device

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Figure 7-11: Coverage pattern

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Figure 7-12: Data rate boundaries

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Collecting Non-RF Information:Collecting Non-RF Information:• Sources of interference can include:Sources of interference can include:

Wire mesh security windows, Aquariums, Outer walls, Wire mesh security windows, Aquariums, Outer walls, Ceramic or marble floors, Concrete floors or pillars, Ceramic or marble floors, Concrete floors or pillars, Security booth bullet-proof glass, Mirrors, and Security booth bullet-proof glass, Mirrors, and Elevator shafts or filing cabinetsElevator shafts or filing cabinets

• Electrical and network connectionsElectrical and network connections Outdoor Surveys: Outdoor Surveys: Similar to indoor Similar to indoor

surveys, but must consider climatic surveys, but must consider climatic conditions, trees, different possibilities for conditions, trees, different possibilities for antenna positionsantenna positions

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Outdoor Surveys (continued):Outdoor Surveys (continued):• Different tools may be requiredDifferent tools may be required

GPSGPS Range finderRange finder Tape measureTape measure Lighting beacons, flares, and spotlightsLighting beacons, flares, and spotlights

Finalizing the Survey Documents: Finalizing the Survey Documents: Final result is map of optimal areas of Final result is map of optimal areas of coverage for placement of access pointcoverage for placement of access point• If results unacceptable, must relocate AP and If results unacceptable, must relocate AP and

start overstart over

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Performing a Site Survey: Performing a Site Survey: Creating the Site Survey ReportCreating the Site Survey Report

Narrative section:Narrative section:• State customer requirementsState customer requirements• Outline methodologyOutline methodology

Outline all steps taken during surveyOutline all steps taken during survey

• Clearly state results of measurementsClearly state results of measurements May have tables of measurementsMay have tables of measurements

• RecommendationsRecommendations Should always address securityShould always address security

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Figure 7-13: Table of measurements

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Graphic section:Graphic section: • Generally includes maps and diagrams Generally includes maps and diagrams

of coverage areaof coverage area Data rate coverage mapData rate coverage map Signal-to-noise ratio plotSignal-to-noise ratio plot

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Figure 7-14: Data rate coverage map

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Figure 7-15: 3-D signal-to-noise ratio plot

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SummarySummary

A site survey is an in-depth examination A site survey is an in-depth examination and analysis of a proposed wireless LAN and analysis of a proposed wireless LAN site to meet design goalssite to meet design goals

Three categories of tools usedThree categories of tools used• Wireless tools include the access point and Wireless tools include the access point and

notebook computers with a wireless NICnotebook computers with a wireless NIC• Measurement tools include site survey Measurement tools include site survey

analyzers, spectrum analyzers, and network analyzers, spectrum analyzers, and network analyzersanalyzers

• Documentation tools create a “hard copy” of Documentation tools create a “hard copy” of the site survey results for future referencethe site survey results for future reference

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SummarySummary

Three steps in conducting a site Three steps in conducting a site surveysurvey• Gather the background dataGather the background data• Perform the actual surveyPerform the actual survey• Create the site survey report, containing Create the site survey report, containing

a narrative and a graphical sectiona narrative and a graphical section

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Wireless Survey with Wireless Survey with NetstumblerNetstumbler

NetStumbler is an excellent free tool NetStumbler is an excellent free tool for performing Wireless site surveysfor performing Wireless site surveys

• It’s easy when combined with the Excel It’s easy when combined with the Excel Wireless SpreadsheetWireless Spreadsheet

http://wildbill.org/rose/Summer06/wireless_lan_survey.ziphttp://wildbill.org/rose/Summer06/wireless_lan_survey.zip

Netstumbler tracks access points along Netstumbler tracks access points along with signal strength at predetermine with signal strength at predetermine sampling pointssampling points

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Wireless SurveyWireless Survey

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Walk around the site with a laptop Walk around the site with a laptop running NetStumblerrunning NetStumbler• Follow a predetermined pathFollow a predetermined path• Use a site/building diagramUse a site/building diagram

Annotate Access PointsAnnotate Access Points Determine and annotate sampling points on Determine and annotate sampling points on

diagramdiagram

• Using, Ctrl-Shft-A to log to spreadsheet Using, Ctrl-Shft-A to log to spreadsheet when you are at a sampling pointwhen you are at a sampling point

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Export the Netstumbler session to a Export the Netstumbler session to a text filetext file

Using the spreadsheet (run report Using the spreadsheet (run report button), import the Netstumbler filebutton), import the Netstumbler file

This updates spreadsheet and you This updates spreadsheet and you can review the power levels by can review the power levels by sampling point.sampling point.

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Thursday we will do a wireless survey Thursday we will do a wireless survey of this buildingof this building

Bring your own laptop or use one Bring your own laptop or use one supplied by Rosesupplied by Rose

We will team up in PairsWe will team up in Pairs One will carry the laptop and the One will carry the laptop and the

other the survey paperwork (building other the survey paperwork (building diagram and note paper)diagram and note paper)