6/22/2015Wireless Networking J. Bernardini1 Wireless Networking WLAN Site Survey Module-09 Jerry Bernardini Community College of Rhode Island 6/22/20151Wireless

04/18/23 Wireless Networking J. Bernardini 1

Wireless Networking

WLAN Site SurveyModule-09

Jerry BernardiniCommunity College of Rhode Island

04/18/23 1Wireless Networking J. Bernardini


Presentation Reference Material

• CWNA Certified Wireless Network Administration Official Study Guide

(PWO-104), David Coleman, David Westcott, 2009, Chapter-15,16

• CWNA Certified Wireless Network Administration Official Study Guide, Fourth Edition, Tom Carpenter, Joel Barrett –

– Chapter 6, pages 232-318

• The California Regional Consortium for Engineering Advances in Technological Education (CREATE) project



What is a Site Survey?

• Process of planning a WLAN to meet design goals• When installing a WLAN for an organization, areas of

dead space might not be tolerated– Ensure blanket coverage, meet per-user bandwidth requirements,

minimize “bleeding” of signal

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


What is a Site Survey?

• Factors affecting wireless coverage goals (continued):– Expansion of physical plant or growth of organization– Existing WLANs

• Both inside organization, and within nearby organizations

• Site survey: Process of planning a WLAN to meet design goals– Effectiveness of a WLAN often linked to thoroughness of the site

survey


Design goals for a site survey

• Achieve best possible performance from WLAN• Certify that installation will operate as promised• Determine best location for APs• Develop networks optimized for variety of

applications• Ensure coverage will fulfill organization’s

requirements• Locate unauthorized APs


More Site Survey Goals

• Map nearby wireless networks to determine existing radio interference

• Reduce radio interference as much as possible• Make wireless network secure• Survey provides realistic understanding of

infrastructure required for proposed wireless link• Assists in predicting network capability and

throughput• Helps determine exact location of APs and power

levels required


When to perform a site survey

• Before installing a new wireless network• Before changing an existing wireless network• When there are significant changes in personnel• When there are changes in network needs• After making physical changes to a building

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Project Planning Overview

• User’s Requirements

Budget Population

Applications Performance

Security Coverage Area

Physical & Logical Network Site Environment

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Site Survey

• A site survey is very important before you deploy a wireless network.

• A site survey involves analyzing a site from an RF perspective.– Coverage– Interference Sources– Equipment Placement– Power Requirements– Wiring Requirements

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Preparing for a Site Survey

• Preliminary Plan

– Existing Network– Towers and Roofs– Coverage– Access Point Locations– Security

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Facility Analysis

• What type of Facility?– Personal– Small Office – Home Office, (SOHO)– Real-estate Office– Small Warehouse– Hospital– Manufacturing Plant– Corporate or Educational Campus

Physical and RF Site Surveys

• Two major categories of site surveys• Physical Survey and RF Survey• Physical Survey

– Examination of physical environment

• RF Survey– Examination of RF activity


Questions Answered by Physical Site Surveys


Questions Answered by RF Site Survey


Manual RF Site Survey Breakdown



Obtaining Business Requirements

• Determine business reasons why WLAN being proposed or extended– If this step skipped, almost impossible to properly design and

implement the network– Primary data gathering method is interviewing– Must determine type of mobility required within organization– Must determine per-user bandwidth requirements

• May be different “types” of users with different bandwidth requirements

Overall Business Objectives

• Quality improvement (Better)• Efficiency improvement ( Faster)• Cost reduction (Cheaper)• Increased production (More)• Organizational continuity (Continue to exist)• Sarbanes-Oxley (accountability)


Organization’s Needs and Objectives

• Determine business requirements• User requirements-bandwidth related• Functional requirements• Budgetary Constraints• Regulatory Constraints



Site Survey Tools: Wireless Tools

• Most basic tool is AP itself:– Position AP in various locations, monitor signal as you move – APs should have ability to adjust output power– APs should have external antenna connectors

• Test effectiveness of different antenna types in different situations– May need DC-to-AC converter for testing

• Notebook computer with wireless NIC also essential for testing– Previously configured and tested


Site Survey Tools: Measurement Tools

• Site Survey Analyzers: Specifically designed for conducting WLAN site surveys– Software often built into AP– Receive Signal Strength Indicator (RSSI) value– Full-featured site survey analyzer software settings:

• Destination MAC Address• Continuous Link Test• Number of Packets• Packet Size• Data Retries


Site Survey Tools: Measurement Tools (continued)

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

• Data Rate• Delay Between Packets• Packet Tx Type

– Unicast or multicast

• Percent Success Threshold

– Basic survey analyzer software contains far fewer features


Spectrum Analyzers

• Scan radio frequency spectrum and provides graphical display of results– Typically measure signal-to-noise ratio– Single-frequency analyzers measure signal-to-noise ratio at specified

frequency– Helpful in identifying interference problems

• Thus, helps properly position/orient AP

• Costly $500 $50,000

Spectrum Analyzer Measures RF energy


Frequency range: 100kHz - 6 GHz.Internal preamplifier with frequency range from 100 kHz - 6 GHz.Displayed average noise level typ. -135 dBm (RBW 100 Hz).0.5 dB typ. level accuracy up to 6 GHz.Resolution bandwidths 100 Hz - 1 MHz, 1 and 3 steps.Wide range of detectors; sample, max/min peak, auto peak, RMS.

Cost: $13,500

WiFi Hopper


Website: http://wifihopper.com/overview.html

http://wifihopper.com/overview.html


Airmagnet Site Survey Tool



AirMagnet Survey

• AirMagnet Survey This WLAN planning solution stands apart from other market planning solutions by enabling enterprises to collect live signal, packet and spectrum data during their site surveys. This allows enterprises to simulate and measure network performance in the most scientific way possible—with the most accurate depiction of a real-world user experience-which ultimately results in a better performing network.



Site Survey Tools: Documentation Tools

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

• Site survey report should include:– Purpose of report– Survey methods– RF coverage details (frequency and channel plan)– Throughput findings– Sources of interference


Site Survey Report Material

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

• Use plain paper and building layout blueprints as tools

• Advisable to create database to store site survey information and generate reports


Survey Security and Site Documents• Defining Security Requirements: Consider type of data encryption and type of

authentication that will take place across WLAN– Consider existing security policies and procedures

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

• Show specific building infrastructure components– Inspecting the site

• Document changes to blueprints and get visual perspective– Behind-the-scenes site inspection

• Documenting Existing Network Characteristics: New or expanded WLAN will “dovetail” into network already in place– Determine degree to which WLAN will interact with other wired networks– Legacy systems may require additional equipment to support WLAN


Performing a Site Survey: Performing the Survey

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

• Use digital camera

– Position AP• Initial location will depend on antenna type• Document starting position of AP

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

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


Position of APs


Collecting RF Information

• Continue moving until data collected for all areas• Data collected used to produce:

• Coverage pattern: Area where signal can be received from the AP• Data rate boundaries: Range of coverage for a specific transmission

speed• Throughput: Number of packets sent and received and data rates for each• Total transmission range: Farthest distance at which signal can be

received by wireless device


Survey Data rate boundaries


RF Data Collection

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

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

– Electrical and network connections

• Outdoor Surveys: Similar to indoor surveys, but must consider climatic conditions, trees, different possibilities for antenna positions


Performing a Site Survey: Performing the Survey

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

• GPS• Range finder• Tape measure• Lighting beacons, flares, and spotlights

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


Creating the Site Survey Report

• Narrative section:– State customer requirements– Outline methodology

• Outline all steps taken during survey

– Clearly state results of measurements• May have tables of measurements

– Recommendations• Should always address security

• Graphic section: – Generally includes maps and diagrams of coverage area

• Data rate coverage map• Signal-to-noise ratio plot


Table of measurements


Data rate coverage map


3-D signal-to-noise ratio plot is the output of some survey applications

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Preparing for a Site Survey

• Facilities Analysis (Floor Plan, Maps, Satellite Imagery)

Floor Plan – Network

Satellite or Ariel Imagery

Maps of Campus/Facilities

WLAN

Santa Maria,SM

BLDG-A BLDG-B

RM-12-AP3 RM-12-AP4 RM-10-AP2wlan-sm-bldga-rm12ap3

Naming Convention

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Existing Networks

• Is there already a network in place?

– Wired– Wireless– Wired-Wireless– Topology – Location of existing equipment– Current User’s Requirements

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Area Usage and Towers

• Indoors, outdoors, or both.– Indoor

• Building Type Floor Plan• HVAC Security

– Outdoor• Weather Security• Towers Power• Environmental Obstructions (RF)

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Purpose & Business Requirement

• Purpose, Needs, and Expectations

– Define Business Model– User needs– Interview with client and users– Wireless impact on business operation

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Bandwidth & Roaming

• Bandwidth and Throughput– 802.11 a, b, g, n and Bluetooth– Number of Users– Types of Applications– Environmental changes as a function of

seasons.– Mobility or Roaming needs

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Available Resources

• Project Budget• Time Line• Trained Personnel• Floor Plans, CAD• Existing Site Survey Reports• Access to Equipment and Site Areas

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Security Requirements

• Network Security – Wired and Wireless

– Corporate Mandated Security – Current Security Policies– Hierarchy of Data Security– Training of Users

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Site Survey Equipment

• Access Point, PC Card, and USB Adaptor• Antennas, Cables, and Connectors• Desktops, Laptops, and PDA’s• Power Supplies and Batteries• Ladder, Measure, and Hand Tools• Analysis Software• GPS, Cell Phone, Walkie-Talkie• Forms, Floor Plans, and Paper

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Site Survey Equipment

http://www.terra-wave.com/Detail.bok?searchpath=d18e4017fc6a7b286abd&category=Site+Survey+Tools&start=1&total=12&no=104

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Site Survey Software

Netstumbler - www.netstumbler.comThis program is great for seeing what other access points are nearby. This can help you by seeing what other SSID's are around so you know what NOT to name yours, as well as help you pick a channel that doesn't have a lot of people using it, giving you a better signal between your access point and your client. Works only with certain cards. Windows and PocketPC versions are available.

Kismet - www.kismetwireless.netThis program is similar to Netstumbler, though for the open source world. Additional features that Kismet has include the ability to log any traffic heard, as well as providing additional detailed information. Unlike Netstumbler, Kismet is COMPLETELY passive, meaning no transmitting is done to obtain any of the information shown. Great for finding rogue access points as well as their users in a corporate environment. *nix, Familiar (Linux on iPAQ) and Sharp Zaurus versions are available.

http://www.netstumbler.com/

http://www.kismetwireless.net/

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Site Survey Software

Airsnort - airsnort.shmoo.comThis program was used in the early days of 802.11b to determine whether or not your access point and/or wireless adapters used insecure initialization values for the RC4 encryption used by WEP. Many newer AP's and cards have resolved this by not using the 3000-something weak IV's that could lead to the WEP key being cracked. *nix/X-Windows version available. Also WPA and WPA2 are now in use.

http://airsnort.shmoo.com/

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Access Point

Electrical SpecificationsUsing the Power AdapterVoltage (Input) = 100 to 240 VAC (50-60 Hz) @ 0.4 AVoltage (Output) = 12 VDCPower Consumption = 10 WattsUsing Active EthernetInput Voltage = 42 to 60 VDCOutput Current = 200mA at 48VPower Consumption = 10 Watts

Recommend: 12 volts DC at 1.5 Ampere Power Source 48 volts DC at 250 mA Power Source

Variable RF power output would be a nice feature. If not available consider fix or stepped attenuators.

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Access Point Remote Power

12 volt, 7-amp/hr recharge in less than 12 hours.

12 volt, 17-amp/hr recharge in less than 12 hours.

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Laptops & PDAs

1

43

2

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Spectrum Analyzer

2.0 5.0Frequency, f (GHz)

Two basic types:Hardware and Software

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Network & Protocol Analyzer

FlukeAirMagnet

Wireshark

http://en.wikipedia.org/wiki/Image:Wireshark_Icon.svg

http://en.wikipedia.org/wiki/Image:Wireshark_Icon.svg

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Site Survey Kit Checklist

• See Site Survey Kit Checklist in the text.Laptop or PDAWireless PC card and AP as needed.Power PackSite Survey SoftwareLocation maps and building diagramsCables & ConnectorsProper Clothing

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Site Survey Kit Checklist

Hand Tools and mounting hardwareDigital CameraGPS, Terrestrial Telescope, BinocularsMeasuring wheel, tape measure, and levelAppropriate transporting equipmentDocumentation and writing materialsAntennasAnything else you meant to bring.

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Conducting a Site Survey

• Examine the network usage problems the wireless LAN solves.

• Study blueprints of the proposed wireless LAN site.• Conduct a physical walk-through and inventory. • Measure the radio frequency (RF) transmissions.• Indoor and/or Outdoor Survey.

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Indoor Survey

• AC Power Outlets and Grounds• Wired Network Connectivity• Potential RF Obstructions (Metal)• Potential Interference Sources• Access to all areas

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Floor Plan65 feet

42feet

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Indoor Survey65 feet

42feet

Utilitiesand POP

1

32

Ethernet

RF Field

Gateway

Access Points

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Outdoor Survey

• Trees, buildings, lakes, mountains, or other obstructions between linked sites.

• Consider growth and foliage of trees, bushes, and plants.

• Line of Sight and distance between stations.• Weather common to location.• Towers and roofs.

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RF Information Gathering

• Range and Coverage Patterns• Data Rate Boundaries• Documentation• Throughput Test and Capacity• Interference Sources• Wired Data Connectivity• AC/DC Power Requirements• Outdoor Antennas

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Range and Coverage Patterns

AP

Think Three Dimensional!

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AP

-47 dB

-61 dB

AP

- 61 dB

AP

-61 dB

1

2

New Coverage Area

http://home.pacbell.net/mariusm/netstumbler_big.jpg

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AP

A dead spot is an area or zone where wireless network services are notavailable because the signal between the client and the AP is blocked orattenuated, usually by terrain, excessive foliage, buildings, or architectural features.

Dead Spot

Dead SpotDead Spot

Coverage MapCoverage Map

12

3

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Range and Coverage Patterns6 11

11

11 6

6

1

1

11 1 6

1

6 11

11

11 6

6

1

36

36 44

48

40

44

40 44 48

40

802.11b/g

802.11a

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Data Rate Boundaries

AP

5.5 Mbps

2 Mbps

Data Rates

Color Code

11 Mbps

5.5 Mbps

2 Mbps

1 MbpsAP

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Throughput Test & Capacity

• Live testing of the network with actual data transfers.

• Traffic congestion, bottlenecks, and future expansion.

• Document baseline measurements for deliverables, (User Requirements) and maintenance and troubleshooting.

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Interference Sources

• Active Interference – 2.4 GHz cordless phones, Medical Equipment, Microwave Ovens/sources, Bluetooth, X10 Devices, Other 802.11 Devices…

• Passive Interference – Path Loss, Metal Walls, Concrete, Brick, Stucco, Foliage, Glass, People, Vehicles…

• Signal Reflections - Multipath

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AC/DC Power Requirements

• Is AC circuit available and at what rating?• Is a ground available?• Power over Ethernet?• Wired Network Connectivity• Backup Power

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Outdoor Antennas

• Temporary Antennas for a Site Survey.

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Site Survey Report Format• Title Page• Abstract• User’s Requirements• RF Coverage Area• Throughput• Interference Sources• Problem Areas• Drawings

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Site Survey Report Format• Installation/Configuration Information• Cost Analysis• Conclusion• Appendices


Summary

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

• Three categories of tools used– Wireless tools include the access point and notebook computers with

a wireless NIC– Measurement tools include site survey analyzers, spectrum analyzers,

and network analyzers– Documentation tools create a “hard copy” of the site survey results

for future reference