The Value of a Wireless Site Survey
By Jason Cornish, Senior Systems Engineer
During my more than 13-year career as a senior systems engineer, I have always tried to help our customers acquire the most appropriate wireless equipment to fit their needs. To do this, I start out by asking the most important question first, “Have you ever had a wireless site survey done?”
Believe me, I have heard every answer out there—from the confident people who don't think they need one, to the inexperienced folks who haven’t even heard of a wireless site survey. When this happens, I know I need to educate them on the benefits of conducting a wireless site survey. It’s situations like these that have inspired me to write on this subject as my first blog topic.
Starting out with the basics of a wireless site survey
When I first meet with a client, I usually start out by describing the terms, the value, and the process of a wireless site survey. I explain that this type of survey is usually performed to gather the radio frequency (RF) characteristics of the WIFI atmosphere. I break it down even further and discuss that a wireless site survey is usually performed to provide any of the following:
- Access point placement
- Client connectivity issues
- Wireless enhancement
- Security issues
- Many more issues unique to the customer and the application
Read these case studies where a wireless site survey helped two clients:
Three types of wireless site surveys: Active, Predictive, and Verification
As the conversation with the client continues, I explain that wireless site surveys are broken down into three categories—active, predictive and verification.
Active wireless site surveys are used when trying to determine the proper locations to install wireless access points. This survey consists of using an access point, placed in a proposed installation location, to capture the RF characteristics of that access point location. This process is repeated over and over until all of the wireless goals are met.
This survey is sometimes referred to as the AP-on-a-Stick survey because that is usually how to replicate the installation of the AP on the ceiling. This active site survey will be able to provide optimal RF characteristics including signal strength, RF noise levels, signal to noise ratio (which determines data rates), and the predicted data rate coverage.
Once the active survey is completed, a final report is created and will present heat maps of the RF characteristics mentioned, as well as hardware equipment quantities needed and installation locations. The active survey is usually the most time-consuming, but gives the best detail of what is needed for a successful wireless installation.
Predictive wireless site surveys are an inexpensive way for a customer to get an idea on how many access points will be needed and where to place them, with the added bonus of forgoing someone coming onsite. The predictive survey is based off of the mathematical signal loss of the materials that the walls are made of. When performing this type of survey, it’s important to know just what every wall is made of: whether it’s wood, glass, concrete, or cinder block. We do this in order to get a close estimation of how the signal is going to cover in that location.
There are drawbacks to conducting a predictive survey. With this type of survey, clients are unable to gather any information about the RF atmosphere, such as noise, other wireless networks, and items inside the walls that may cause interference.
Due to these drawback issues, it is highly recommended to have a verification survey performed to tune and optimize the new deployment.
Verification surveys are the most important surveys to have performed on a wireless environment. This survey is used to provide a look into the existing wireless environment, whether it be to troubleshoot connectivity and coverage issues, or to tune and optimize the current radio atmosphere. A verification survey, when used to troubleshoot, can provide details on the following:
- Potential RF interference issues from non-WIFI devices such as microwaves, DECT phones, and radar to name a few.
- Possible WIFI dead spots. These are areas that do not have adequate signal coverage to provide optimal client connectivity.
- Potential configuration issues that are causing issues. These can include channel plan, radio transmit power, and other configuration settings for the WLANs.
- Recommendations for AP additions, moves, or deletions to optimize the RF in order to meet the client’s end goal.
In order to keep up with the RF environment, the verification survey should be performed once a year or whenever the building structure has changed. This includes the building’s physical characteristics, such as new walls, ceilings, or doors.
Also, a new survey should be performed if there is an increase in the area’s personnel capacity levels, because people are the biggest attenuators of a RF signal. After all, the human body is mostly water and water absorbs radio waves!
A definite need for a wireless site survey
As the demands for wireless communications continue to grow, it’s critical that a wireless site survey be conducted. I highly recommend having a survey completed as it will provide a look into your RF world, determine the right equipment to fit your needs, and help keep your wireless network optimized and you happy.