Site Survey

Dr. Tahseen Al-DooriDr. Tahseen Al-Doori

Site SurveySite Survey


To get the best performance out of your To get the best performance out of your wireless network, you must both ensure that wireless network, you must both ensure that your access points (AP) are in the most your access points (AP) are in the most optimal locations and that other radio optimal locations and that other radio emitters, which can cause interference, are emitters, which can cause interference, are kept to a minimum. kept to a minimum.

This requires you to periodically perform site This requires you to periodically perform site surveys of your wireless spectrum. surveys of your wireless spectrum.


Depending on the scale of your installation, Depending on the scale of your installation, there are a number of tools available for the there are a number of tools available for the task, such as software that walks you task, such as software that walks you through the site survey process. through the site survey process.

But no matter what size network you will But no matter what size network you will have, you'll need to follow these basic steps:have, you'll need to follow these basic steps:


Step 1Step 1

Have a blueprint or floor plan(s) of the areas you Have a blueprint or floor plan(s) of the areas you want the wireless network to cover. Some software want the wireless network to cover. Some software products can work off these floor plans directly. products can work off these floor plans directly.

Look at your plans and identify major building Look at your plans and identify major building obstacles such as walls, halls, elevators and floors obstacles such as walls, halls, elevators and floors that will block radio signals. Also note where your that will block radio signals. Also note where your users will be located -- and where they won't -- to users will be located -- and where they won't -- to determine coverage areas. determine coverage areas.


Step 2Step 2

Determine where you can locate APs based Determine where you can locate APs based on power and cabling that you can run to on power and cabling that you can run to connect the AP to the rest of the network.connect the AP to the rest of the network.

Remember that you shouldn't place APs Remember that you shouldn't place APs close to metal or concrete walls and you close to metal or concrete walls and you should put them as close to the ceiling as should put them as close to the ceiling as possible. possible.


Step 3Step 3

Estimate the total number of APs needed for Estimate the total number of APs needed for your overall coverage. A good rule of thumb your overall coverage. A good rule of thumb is one AP can cover a circle with a 100-foot is one AP can cover a circle with a 100-foot radius. This will give you preliminary AP radius. This will give you preliminary AP locations that you can use at the beginning locations that you can use at the beginning of your survey. of your survey.

If you already have some APs, note their If you already have some APs, note their locations on your floor plans. locations on your floor plans.


Step 4Step 4

Run the survey tool. Make sure to use the Run the survey tool. Make sure to use the same AP model for the survey that is used same AP model for the survey that is used in your actual infrastructure. in your actual infrastructure.

See below for recommendations about See below for recommendations about which tool to use. which tool to use.


Step 5Step 5

Relocate APs and retest, depending on the Relocate APs and retest, depending on the results of your survey. results of your survey.


Step 6Step 6

Document your findings. Document your findings. Record the locations and log your signal Record the locations and log your signal

readings and data rates observed for future readings and data rates observed for future reference. reference.


So, how do you pick the right tool for So, how do you pick the right tool for your surveying needs? There are your surveying needs? There are

three basic types:three basic types: First, there are First, there are simple Windows-based simple Windows-based

software toolssoftware tools that you can use on a single that you can use on a single laptop used for recording measurements laptop used for recording measurements such as signal strength as you walk around such as signal strength as you walk around your building. You just need to buy a single your building. You just need to buy a single AP and move it around to the potential AP and move it around to the potential locations that you came up with in Step 3. locations that you came up with in Step 3. These tools are good for smaller These tools are good for smaller installations of, say, one to three APs.installations of, say, one to three APs.


They are also good for situations in which They are also good for situations in which you don't have a simple open-office plan but you don't have a simple open-office plan but rather have various corridors and potential rather have various corridors and potential radio dead spots scattered around multiple radio dead spots scattered around multiple floors. floors.

There are free tools, such as NetStumbler, There are free tools, such as NetStumbler, and more capable ones, such as AirMagnet and more capable ones, such as AirMagnet Survey, Visiwave, Fluke Networks Survey, Visiwave, Fluke Networks InterpretAir and Ekahau Site Survey, which InterpretAir and Ekahau Site Survey, which cost several thousand dollars.cost several thousand dollars.


Or, there are Or, there are tools that work in tools that work in conjunction with switched wireless conjunction with switched wireless productsproducts. .

These tools, from Cisco Systems Inc., These tools, from Cisco Systems Inc., Aruba Networks and Trapeze Networks, Aruba Networks and Trapeze Networks, monitor your radio coverage and suggest monitor your radio coverage and suggest where to locate the APs for best coverage.where to locate the APs for best coverage.


The Aruba Mobility Controller tool is available as a free trial The Aruba Mobility Controller tool is available as a free trial and is an integrated part of their wireless switch product. and is an integrated part of their wireless switch product.

The Wireless Control System tool from Cisco costs $4,000, The Wireless Control System tool from Cisco costs $4,000, and Trapeze's RingMaster costs an extra $549. and Trapeze's RingMaster costs an extra $549.

If you haven't decided on a wireless infrastructure vendor, If you haven't decided on a wireless infrastructure vendor, evaluating the analysis tool should be part of your decision evaluating the analysis tool should be part of your decision process. process.

One issue with these tools is that, since they use the actual One issue with these tools is that, since they use the actual wireless infrastructure to report on coverage, they don't do wireless infrastructure to report on coverage, they don't do as good a job of reporting on dead spots and areas of poor as good a job of reporting on dead spots and areas of poor radio coverage. radio coverage.

Depending on your floor plans and the number of Depending on your floor plans and the number of obstacles, such as thick walls and metal walls, you may still obstacles, such as thick walls and metal walls, you may still need to purchase one of the walk-around tools discussed need to purchase one of the walk-around tools discussed previously.previously.


Finally, there are Finally, there are large-scale simulation toolslarge-scale simulation tools. These are . These are useful for multifloor, campus-size assessments and are useful for multifloor, campus-size assessments and are helpful for big deployments involving simulations or require helpful for big deployments involving simulations or require the modeling of various scenarios. the modeling of various scenarios.

These tools include AirTight Networks' SpectraGuard These tools include AirTight Networks' SpectraGuard Planner, Motorola's Wireless Valley LANPlanner, Planner, Motorola's Wireless Valley LANPlanner, AirDefense Survey and Bluesocket's Wireless LAN AirDefense Survey and Bluesocket's Wireless LAN Planner. Trapeze's RingMaster also has the ability to do Planner. Trapeze's RingMaster also has the ability to do radio modeling and simulation. radio modeling and simulation.

These tools are useful for estimating the total number of These tools are useful for estimating the total number of APs you'll need, and they do a relatively good job of APs you'll need, and they do a relatively good job of simulating the eventual environment, but they can't tell you simulating the eventual environment, but they can't tell you about interfering devices or give you a complete overview about interfering devices or give you a complete overview of your wireless networking environment.of your wireless networking environment.


Remember that doing a wireless site survey once Remember that doing a wireless site survey once is not enough. Rather, they must be done is not enough. Rather, they must be done periodically. Your radio environment can change periodically. Your radio environment can change as Bluetooth keyboards and headsets come and as Bluetooth keyboards and headsets come and go, as microwave ovens turn on and off, and as all go, as microwave ovens turn on and off, and as all sorts of other wireless devices pollute the 802.11 sorts of other wireless devices pollute the 802.11 spectrum. spectrum.

So, to stay ahead of users who will inevitably So, to stay ahead of users who will inevitably complain that their signals are too weak and find complain that their signals are too weak and find new dead spots in your buildings, be proactive and new dead spots in your buildings, be proactive and make sure that your surveys are part of general make sure that your surveys are part of general network operations.network operations.


Exercise (Exercise (Manual Coverage Manual Coverage AnalysisAnalysis ) )

In this exercise, you will test-drive a commercial site survey In this exercise, you will test-drive a commercial site survey software application called Air-Magnet Survey to simulate software application called Air-Magnet Survey to simulate manual coverage analysis.manual coverage analysis.

After downloading the AirMagnet Survey demo software, After downloading the AirMagnet Survey demo software, double-click on the executable file. Follow all the double-click on the executable file. Follow all the installation prompts.installation prompts.

From the Windows Start menu, under Programs, run the From the Windows Start menu, under Programs, run the AirMagnet Surveyor Demo.AirMagnet Surveyor Demo.

When prompted to open a sample project, click the Yes When prompted to open a sample project, click the Yes button.button.

In the top-left window of the program, choose In the top-left window of the program, choose PassiveSurvey1.svd. Click the Yes button and watch the PassiveSurvey1.svd. Click the Yes button and watch the demonstration.demonstration.

Observe the colored heat maps that give a graphical Observe the colored heat maps that give a graphical representation of RF coverage areas.representation of RF coverage areas.


In the top-left window of the program, In the top-left window of the program, choose ActiveSurvey1.svd. Click the Yes choose ActiveSurvey1.svd. Click the Yes button and watch the demonstration.button and watch the demonstration.

In the top-left window of the program, In the top-left window of the program, choose MergedPassiveActive.svd. Click the choose MergedPassiveActive.svd. Click the Yes button and watch the demonstration.Yes button and watch the demonstration.

Test-drive some of the other features on the Test-drive some of the other features on the bottom and right menu bars. bottom and right menu bars.

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