Wi-Fi interference

In this research report, Craig Mathias undertook the challenge to quantify the problem of interference in wireless LANs and defined a methodology for evaluating the effects of interference on WLANs.

The history of wireless LANs has been punctuated with one major concern after another. We started with the standard, "It will never work," and proceeded to issues relating to price, performance, security, total cost of ownership and return on investment, management, and integration. One challenge that has remained pervasive over the past 15 years or so is interference. Wireless LANs operate in the unlicensed bands and have no particular claim to the spectrum they use. They must share frequencies not just with other wireless LANs but with a broad range of products, from cordless phones to microwave ovens to wireless video surveillance cameras. So it's fair to ask whether interference really is a problem, or even a showstopper, as WLANs continue to grow in popularity.

With this in mind, I began a project last summer to quantify the problem, define a methodology for evaluating the effects of interference on wireless LANs, and to actually run detailed experiments on just how bad the problem might be. The results can be seen in a series of Farpoint Group White Papers and Technical Notes, which you can find below. The experiments I ran evaluated the impacts of a number of forms of interference on general Wi-Fi traffic, voice over IP over Wi-Fi (VoFi) traffic, and video over Wi-Fi (VidFi) traffic. And they weren't at all pretty in a number of cases.

A bigger challenge, though, is exactly how to monitor for and correct interference issues when they occur. As it turns out, we're now seeing the availability of a new class of Wi-Fi management products -- what I call Spectrum Assurance (SA) tools -- that can identify any form of interference, even that from non-Wi-Fi sources, and recommend how to correct the situation. I expect these tools will be integrated into system-level wireless LAN management products over the next few years. So, as you'll see in the reports noted above, though interference can have a positively devastating impact on WLAN traffic, help is on the way. For that reason, I've concluded that even as more products and systems occupy the unlicensed bands, we have the technology to ensure the performance of WLAN systems well into the future.

Wi-Fi interference reports in PDF
The effect of interference on general wireless LAN traffic
The effect of interference and wireless LANs
Evaluating interference in wireless LANs
The effect of interference on voice over Wi-Fi traffic
The effect of interference on video over Wi-Fi traffic
Interference and metro-scale Wi-Fi mesh networks

About the author: Craig Mathias is a principal with Farpoint Group, an advisory firm based in Ashland, Mass., specializing in wireless networking and mobile computing. The firm works with manufacturers, enterprises, carriers, government, and the financial community on all aspects of wireless and mobile. He can be reached at craig@farpointgroup.com.

This was last published in March 2007

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