Conducting Site Surveys for WLAN Performance and Reliability
Mike Diss
SE, EMEA, [email protected]
June 16, 2010
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AirMagnet Overview
• Founded in 2001; based in Sunnyvale, California, USA• Amassed over 8,500 customers – 75 of the Fortune 100
– 25,000+ Product Licenses Sold
• Worldwide support in more than 120 countries• Global footprint of authorized resellers and distributors• Recently acquired by Fluke Networks (Worldwide HQ: Everett,
WA)
AirMagnet is the leader in wireless LAN security, performance and compliance solutions for wireless LANs.
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WLAN Lifecycle: Best Practice to Cope with Constant Changes in Wireless
• Pre-Deployment Design and Planning
– Design wireless network tailored to environment, user and application needs
• Operational Management– Proactively monitor WiFi, RF,
Voice performance to identify problems before impact
• Security Management– Iron-clad protection with visibility
and defense from all forms of wireless threats
Conducting Site Surveys for WLAN Performance and Reliability
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History of WLAN Design Goals
• Old Way– Minimum # of Access Points– Maximum Power– 30+ Users per AP– Bandwidth… what Bandwidth…
• New Way– 10 Users per AP– Minimum Power– Lots of Access Points– Network Performance (& Signal Quality) is Paramount
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Need for Site Surveys
• New Installations– How many APs needed?– Where should they be placed?– How should they be configured?
• Existing Installations– Were the correct number of APs deployed?– Were they deployed in the best location?
• Ongoing Network Optimization– Support for new users– Support for new technology– Support for new applications
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Site Surveying Phases
1. Preparation
2. Site Survey
3. Analysis
4. Reporting & Sign-off
5. Periodic Site Surveys
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Phase 1: Preparation Phase
• Preparation checklist – Questions to ask– Do you know all the stakeholders?
– Is wireless access needed for indoors or outdoors or both?
– Are any building blueprints or street maps available?
– Where do you require coverage?
– What type of business is it?
– Is this a new deployment or an add-on to the existing one?
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Phase 1: Preparation Phase (Continued)
– If adding to an existing wireless network:• Are you unhappy with it? Are users complaining? Or is
your business expanding?
• What equipment have you installed? Where are they installed?
– Think about capacity• How many users require wireless service and what
applications will they use?
• What is the geographical distribution for the users?
• Will they be using applications where they need to roam? What are their throughput requirements?
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Phase 1: Preparation Phase (Continued)
– Are there any known major non Wi-Fi interfering sources? Do you know their locations?
– Is this a multi-floor deployment?
– What are the security requirements?
– Where are the power and Ethernet drops throughout the facility? Is the customer open to installing new drops?
– What is the anticipated growth for the future?
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Phase 1: Preparation Phase (for 802.11n)
• Questions to ask for 802.11n networks– Am I deploying an 802.11n Greenfield network or do I
need to support legacy 802.11a/b/g devices?
– Will the 802.11n devices be deployed in the 2.4 GHz or 5 GHz Band? Or do you want the Site Survey product to recommend the choice?
– What type of clients will be connecting to the network?
– Will I deploy 802.11n devices for my Guest Network?
– Do I see coverage overlap from APs that belong to my neighbor? Is that coverage from 802.11n or legacy 802.11a/b/g devices?
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Phase 2: Site Survey
• Load floor plan maps
– Supported format
– Simple, black and white plans
– Calibrate your floor map scale
• Survey tips and tricks
– Perform a visual inspection of the facility• Can I get everywhere I need to?
– Figure out where you require coverage and where you don’t including areas that obscure results
– Perform survey during “normal” business hours
– Don’t scan unwanted channels• Exterior survey to discover RF channels being used
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Phase 2: Site Survey• Survey tips and tricks
– Make good judgement on the “Signal Propagation Assessment” value
– “Measurement intervals” accuracy• Auto Logging Data Period• No further than what your Signal Propagation
Assessment is set to
– Take readings on both sides of the wall
– Also take readings along the perimeter of the rooms
– Recommendation: Plan your walking path• Results in more accurate clicking
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Phase 2: Site Survey• Survey tips and tricks
– Take readings around the outside of your building
– Place your man where you are headed for and then click when you reach that location
– Don’t try and do it all in one go• Enable you to “retract” when necessary
– Switch between auto sampling and click only sampling as you walk around• Auto sampling for straight line walks (i.e. corridors)• Click only for points within a room
– Size of hashing at click points indicates range of Signal Propagation Assessment
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Phase 2: Site Survey
• Perform your surveys – Passive Surveys
• Collect signal data from all APs & Stations in the area
– Active Surveys• Collect actual performance metrics
(data rate, retries, etc)
• Mandatory for 802.11n deployments
– Iperf Surveys• Collect uplink/downlink performance
statistics
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RF Spectrum Site Survey• Gather RF Spectrum Data
– Non Wi-Fi devices operate in the same spectrum as Wi-Fi
– Cause interference and severely degrade the overall network performance
– Even more important for time sensitive applications
– Locate interfering devices on floor map
– Preferred method: Collect RF data at the same time as a Wi-Fi Survey
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Phase 3: Analysis Phase• Visualize Wi-Fi signal
coverage
• Visualize real-world user performance metrics
– Data rates, retries, losses
– Uplink/downlink performance
• Visualize Roaming areas
• Visualize areas that suffer from Channel Interference
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RF Coverage Analysis
• Visualize Wi-Fi signal coverage at every location
• Locate “dead spots” in your coverage
• Know coverage for your “backup” APs
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RF Coverage Analysis
• 3D view
– Displays signal strength using height instead of heat map
– Visual representation of where there may be issues (valleys, mountains)
• “Overlap” shows area (in red) where 2 or more APs meet certain conditions– On SSID – good
– On Channel – bad
• Multiview– Bleed from multiple floors
– Bleed from outside to inside
– Between buildings
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Simulate “What-if” scenarios
• Optional step in the site survey process
• Simulate different scenarios and AP settings to minimize “dead zones” and “interference”
• No need to walk the floor again
• Visualize how simulating a new AP, plugs the “coverage hole”
• Simulate noise in the environment
• Helps determine the optimal AP configuration settings
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Visualize real-world user performance
• Why do you need this?– Visualize what real users will experience
• AirMagnet Solution– Visualize data rates, packet retries & losses– Accounts for conditions at every location– Obtain uplink/downlink performance metrics
• Critical for 802.11n networks
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Network Design Validation
• Design validation
– “Certify” if the installed Wireless LAN actually meets the initial design specifications
– Mitigates against troubleshooting ‘tail chasing’
– Critical for specialized applications such as voice and video
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Design Validation example for voice
Non-green areas indicate regions that do not meet
the design requirement
Green area indicate regions
that meet the design
requirement
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RF Security
• RF Security – Minimize RF spillage outside
corporate boundary
– Visualize if neighbors or attackers in the parking lot can see your network
– Conduct site survey outside the corporate office boundary
– APs may need re-location, different antennas or configuration changes to minimize leakage
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Phase 4: Reporting & Sign-off
• Most important output for a Site Survey product or in many cases - the “only output”
• Serve as a map for the current recommendations
• Act as a future reference for surveys and other deployment changes
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Phase 5: Periodic Site Surveys
• Critical to account for changes in the environment, interference sources, user behaviour, obstacle changes, etc.
– Introduction of a new microwave in the cafeteria
– Introduction of new access points by neighbours
