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Wireless Survey

Wireless networking is now considered a must have in nearly all industries. It’s no surprise I get a lot of comments from clients who believe they are experiencing wireless trouble in some form or fashion. They aren’t sure if it’s related to wireless controller configuration, AP placement, coverage gaps, interference, or even client machine problems. Even though Wi-Fi is nearly as prevalent as indoor plumbing, it doesn’t mean it’s always deployed properly, is reliable enough, or fast enough to address our clients needs. When something is not quite right with WIFI performance, what do I do? I’ll tell you what I do! I suggest a wireless survey and wireless assessment. Surveys are the best tool a wireless engineer has available to assist them with visualizing an invisible medium like RF. Actively scanning the frequency ranges often used for Wi-Fi as the physical location is walked is the de-facto way to record concrete data on signal, strength, interference, and a whole range of other valuable information. It’s really the only way to understand exactly what’s happening between a laptop client and the access points that dot a location.

There are several survey options, not all of them involve going onsite and actively scanning an RF environment. Sometimes a new facility is being built or a greenfield office is being setup and the client needs assistance estimating the number of access points and the location they should be mounted. With good floor plans it’s not too difficult to get a general idea on estimated coverage size and AP density and AP placement  planning. This type of guidance is usually provided in the form of a predictive survey. I’ll provide a little more detail on the survey types below.

 

Different Types of Wireless Site Surveys

If you’re serious about uncovering what’s wrong with your wireless network design, you first need to understand the four different kinds of site surveys that address WIFI concerns:

  • Predictive Site Surveys -- With this kind of survey, the wireless engineer doesn’t go onsite and measure, rather he loads the floor plans for the site and uses simulation tools to create a model of the radio frequency (RF) environment at your location. A predictive site survey tends to be quite cost and time effective, as well as relatively accurate. You’ll get the best results from this kind of assessment if you’re able to supply accurate and to scale building blueprints or floor plans. Since Predictive Site Surveys don’t analyze what you currently have in your environment, or tell you why you’ve been having problems, they’re typically best suited for smaller or newer projects.
  • Passive Site Surveys -- The wireless engineer uses software to passively listen to traffic on your wireless network -- looking specifically for problems with access points, signal strength, and environmental noise.
  • Active Site Surveys – This type of survey takes the passive survey and also adds focus on applications that roam across access points (APs) as well as applications that are especially sensitive to latency. The survey tool must be setup with WiFi credentials and will actively communicate with a server on the client network via WiFi.

 

What’s Included with Active/Passive Onsite Wireless Site Survey

So now that know you about the three different categories of site surveys for WiFi design, what can you expect when you invest in a wireless survey? And what’s included?

  • An onsite visit with wireless network design engineers -- Engineer comes onsite with laptop and scanning hardware.
  • Manual inspection of wireless hardware -- Walking the site and noting the mounting location, orientation, and proximity to columns/walls of the access points. Recording any that seem to conflict with industry best practices.
  • Running wireless analysis software to capture data -- The heart of an onsite survey
  • Assessment and analysis of data captured and presented in a report document -- The final report which is presented to the client with all the details. Often a separate summary document is created to highlight some of the critical areas of the generated report.

 

The Onsite Survey Report Outlines

 

  • A floor plan listing routes for the site survey, as well as access point locations
  • Data rate heatmap for both 2.4 GHz and 5 GHz wireless frequencies (the highest possible speed that a wireless device can transmit data)
  • Maximum effective throughput heatmap for both 2.4 GHz and 5 GHz wireless frequencies (Due to its half-duplex nature, true data throughput tends to be about half of the data rate.)
  • RF signal strength/coverage heatmap for both 2.4 GHz and 5 GHz wireless frequencies (the most basic measure of wireless networking health that can often explain problems with unreliable connections and low data throughput)
  • CCI (co-channel interference) analysis that identifies any crosstalk between two different transmitters on the same RF channel
  • Non-WiFi device interfernace analysis that identifies any extraneous power interference from a signal on WIFI band not originating from a WIFI device.

In most wireless site surveys, a floor plan with access point locations, data rate heatmap, throughput heatmap, and signal strength heatmap is created for each floor in the building.

 

Typical Findings

So when a company signs up for a wireless site survey, how do they benefit? And what are some typical findings?

While one of the most common goals is to identify configurations that would negatively impact WIFI network performance, there are several findings that surface quite often. These findings can include:

  • Identifying access points that are deployed for the wrong purpose -- For example, during a recent wireless site survey, one company was using the incorrect models of APs in many locations throughout their facility. Because these APs were using omni-directional antennas and the APs were installed on 20-30 foot ceilings, devices being used at ground level ended up with very low signal levels.
  • Identifying RF cell overlap problems between access points -- Again because this same company had omni-directional antennas on its APs, there were too many RF cell overlaps between the APs.
  • Identifying a coverage gap with APs -- This could be due to bad decisions on mounting heights or spacing the AP density -- basically poorly thought out wireless network design. In this case, changing the AP height altered its coverage because of the antenna’s vertical beamwidth, or by adding another AP to fill a gap.
  • AP power levels left at default configurations or changed from default and not dynamically controlled by wireless controller -- By either not customizing the power levels, or by customizing when it should have been left alone.
  • APs installed/mounted at troublesome locations -- When mounted too close to objects that block or alter the RF signal, signal delivery to client devices takes a hit.

 

When one or more of these findings are acted on and implemented, companies generally see an immediate and dramatic improvement in their wireless network performance.

From these findings, the wireless network design engineers will introduce recommendations that remedy as many of these problems as possible including:

  • Better suited AP models -- especially AP models with an antenna that can better adapt to the client’s environment and needs
  • New indoor RF wireless network design -- that takes into account emerging software application requirements
  • New outdoor RF wireless network design -- that’s better suited for outdoor spaces where there are usually no reflective objects or attenuators
  • Removing channel bonding as needed -- to limit the possibility of channel reuse and all the co-channel and adjacent channel contention problems that crop up. Especially in the 2.4ghz space.
  • Removing lower data rates -- again to improve the design of the wireless network by forcing devices to use closer APs with better signal strength
  • Setting/optimizing symmetric power levels -- to match the lowest power client device
  • Improving AP mounting -- for improved RF signal delivery
  • Improving bridge/mesh links -- to greatly improve signal quality

 

In Summary

If you find yourself with WIFI woes please contact your LookingPoint Account Manager and ask about the wireless survey offerings available to you!

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Written By: Michael Lorincz, LookingPoint Network Engineer 

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