Conducting site surveys for wlan performance and reliability

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

Q & A

[email protected]