site survey

CTS 170: APoS Site Surveys

Historically, AP-on-a-Stick (APoS) surveys were the only way to find out where to place the access points. We didn’t have any of the fancy software we have today to predict how the Wi-Fi signal will behave in our space. However, we still perform APoS today. In this episode, we will explain why we still use them and how they can be beneficial to us Wi-Fi Engineers.

APoS utilizes an AP that will be deployed on-site. The AP would be installed on a “stick” and is used to measure how the Wi-Fi signal behaves in the space that is being surveyed. The advantages are it takes into consideration the behavior of an RF wave and the attenuation, reflection, diffraction, scattering, etc. The disadvantage is it takes time and materials to achieve.

Historically, that was the way we used to define where to place the APs. We would start in a corner of a building and place the first AP, measure the signal to define the edge of the Wi-Fi cell and go on to the next measurement until you covered the whole site and defined the different AP locations.

The introduction of tools allowed us to model and predict how the Wi-Fi signal will propagate in a given space. This allows us to plan and perform our Wi-Fi design “on paper” so to speak. In order for this type of predictive design to be accurate, we still need to understand the physical environment. However, we can predict the signal prediction in the software and save some time.

Why do we still use APoS then? In some environment and cases, the predictive design will not be accurate enough for us to be confident in the design. In these cases, we now use the APoS to validate some of the AP locations defined during the predictive design phase. How much validation do we need to do? It depends 🙂

What material will you require to perform an APoS? The APs and antennas you will be using for your deployment. If you are not too sure which AP or Antenna will be used, test multiple models. A stick (tripod, poles…). If you need to go very high, you might need a scissor lift or other heavier tools. A bracket to install the AP and antenna on (Wi-Fi Stand). If you are planning on using specific angles, it could be useful to have a bracket that displays the angle. A battery to power on the AP. Venvolt from Ventev, Accelerator from AccelTex, A long ethernet cable to connect the battery to the AP (I like the flat ones), A water bottle, Useful add-ons: flashlight, Duck tape, zip ties, marker, security boots, yellow vest, ear plugs, safety glasses.

How do you prepare an APoS? You will need to configure the access point. Configure the access point in a standalone mode. Each vendor has their own way of doing it. Cisco using Mobility Express, Aruba using Instant AP, Meraki using the Survey Mode.

I like to configure 1 SSID per band so that I can analyze the results in an easier matter afterward. It also helps me to make sure I am walking far enough to reach the edge of both frequency cell edge. I use the transmit powers used for the design. You can use the channels you want. In order to plan for the worst case scenario, you could choose the highest channel you can use in your space. (Channel 11 on 2.4GHz and Channel 165 on 5GHz). You should also have your predictive model ready before going onsite for the APoS measurements (as much as you can).

How do you perform an APoS? How do you choose which AP location to test? Place the APoS exactly how you would install the AP in production. Turn on the AP and wait for the SSID to be broadcasted. Use your favorite survey software to measure the signal in passive mode. Keep an eye on the signal strength you receive and make sure you walk past your threshold. Once you are done, freeze your AP (in Ekahau) before you move the AP to the next measurement. Try to document your work as you go by taking pictures of the AP at its measurement location and put in notes in your site survey software.

Analyze the results and compare how the signal propagates in the real world and what you had in the predictive design. Adjust your model so it matches the real world. It will be an iterative process and both can be done on-site while you do your APoS.

Things you can also do while you are on-site: Validate the AP locations will work for all the location you have defined in your predictive model. Mark the AP location if you want to. Test the different options such as height and antennas. Take a look at how the users use Wi-Fi.

Links and Resources

CTS 109: Ekahau Sidekick, Spectrum Analysis, and Finnish Rap

Special guests, Samuel Clements and George Stefanick join the show to discuss the Ekahau Sidekick with Rowell Dionicio and Jussi Kiviniemi.

CTS 109: Ekahau Sidekick, Spectrum Analysis, & Finnish Rap

Ekahau Sidekick

Wireless site surveys have been performed with USB adapters for a long time. Many have had grueling battles with getting these USB adapters working, we’ve had them fail, and have seen varying inconsistencies between adapters. Or if you’re me, I nick my adapters all the time.

Recently, Ekahau came out with a game changer. It replaces all your USB adapters into a shoulder strapped, supercharged, all-in-one measuring device. As said on the product’s website, the Sidekick dramatically streamlines the site survey process by replacing and outperforming the previously-used USB hubs providing greater reliability, accuracy and convenience.

That’s our discussion in this episode regarding the Sidekick. How does it stand out in the field in terms of performance, reliability, and accuracy. The added benefit here is convenience.

In this episode, I start things off by asking why the development and release of the Ekahau Sidekick. You’ll get the response directly from Ekahau but additionally, we hear from two customers – Samuel Clements and George Stefanick.

Some of the reasons why they prefer to use the Ekahau Sidekick:

  • Reliability
  • Consistency
  • Performance
  • Receive sensitivity dial
  • Ease of use

Ekahau decided to build the Sidekick from scratch to produce a device capable performing excellent spectrum analysis and Wi-Fi gathering capabilities. Listen to the episode to hear more of our discussion.

One special treat, Jussi shows us what Wi-Fi sounds like.. Yes you read that right.. what Wi-Fi sounds like. You hear it in this episode.

And finally, Finnish Rap

Links & Resources

CTS 062: K12 Wi-Fi Deployments

Jim Vajda, CWNE #183, is our special guest who has done K12 Wi-Fi deployments. Jim provides insights into his requirements, challenges and design process.

Jim Vajda podcast image.

K12 Wi-Fi Deployments

Requirements in a K12?

A primary requirement for K12 involves a low cost solution. Many schools use tax dollars or E-Rate. When using tax dollars schools must be careful with their spending. E-Rate is a federal program which provides schools with discounts to obtain affordable IT equipment.

Getting to the technical requirements, it must be simple to use. Most IT departments are spread thin. A system that is easy to implement is ideal.

High density is important. Many classrooms are teaching with tablets, such as iPads, and Chromebooks. Each classroom does a 1-to-1 distribution of tablets or Chromebooks. With each classroom containing 20 or so students streaming video or performing online testing, we can see this becoming a high density classroom. This is especially so with Faculty carrying their own devices. Some students have their own devices as well.

Security requirements include Role Based Access Controller (RBAC). RBAC is used to control what network resources a user has access to. This is important in an environment where pre-shared key (PSK) is used heavily in K12 environments.

Content filtering is a must in order to protect children from content they should not be viewing. For simplicity of management, K12 would like to see this implemented in the wireless solution they select. In Jim’s experience, he has seen Meraki being used in the majority of K12 public schools in Ohio.

What is not a requirement is fast roaming, centralized data plane, and layer 3 roaming. Most devices are stationary.

A nice to have is layer 7 visibility and wireless client statistics.

Design Process

With older K12 schools, additions to buildings are common. Be sure to do a walk-through to catch any surprises such as a new concrete wall that was just put up.

Perform your own wall attenuation measurements to include in your predictive site surveys. You will create the most accurate results using this method.

Jim uses a D-Link DIR510 to get his wall measurements. To get the measurement, place the AP in the middle of the room or about 20 feet away from the wall. You can use a laser distance tool to measure the distance. Take your first measurement inside the room next to the wall. Then take your next measurement on the other side of the wall. The difference will be your wall dB loss.

The site survey application of choice for Jim is Ekahau Site Survey Pro. Within his surveys he ensures he is using an AP that will be deployed in the K12 school.

When it comes to channel planning, Jim used to start with 40 MHz channel widths but now starts with 20 MHz. This is because of the channel reuse he can get in 5 GHz spectrum for high density. Jim recommends using DFS channels if you can. Make sure to perform spectrum analysis to discover any radar in the area.

In K12 schools it is very rare to see external antennas used. If they are used, it is usually outdoors for coverage. Indoors, you will not see external antennas.


The major challenges Jim sees in K12 schools:

  • Budget constraints
  • IT lacks clout
  • Limited IT staff
  • Poor RRM settings
  • Tx power set too high
  • Excessive Co-Channel Contention in 2.4 GHz
  • Too many SSIDs being broadcasted
  • 1 AP/Classroom

In regards to 1 AP per classroom, this is really a big marketing push. While many environments may not need 1 AP per classroom, some may push for it because it is easy. In some scenarios, 1 AP per classroom can be justified. This can be due to wall material attenuating signals significantly.

Thank You For Listening

You can learn more about Jim Vajda on his Wi-Fi blog, Frame By Frame Wi-Fi. You can also follow him on Twitter – @jimvajda