Thinking About Interference

2:00 PM -- I’m still hearing that WiFi ain’t ever going to get off the ground because of the possibility of radio-frequency interference in the public ISM and U-NII bands. Licensed bandwidth, despite its enormous cost and limited availability, is therefore the only way to go. Hogwash. I wonder how many people who rail against WiFi also do the same regarding Ethernet. Hey, we can’t be using the devil’s wire, we might have a collision! That’s what interference is called in the wired world. And wouldn’t such just ruin our days for all eternity?

OK, the let’s-go-licensed crowd has a point. I’ve been doing studies of this issue, with results to be published shortly, and I’ll be the first to admit that interference is occasionally a problem today, and that it’s likely to be a much bigger challenge in both the 2.4 and 5GHz. bands in the future. Note that interference can come from both foreign WiFi systems as well as the zillion or so other wireless gadgets that operate in these bands. And the problem will be seen in the residence (where media applications will play a much bigger role), the enterprise (where WLANs will become the default voice and data vehicle for most of us) and even outdoors, where metro-scale meshes will blanket the city.

The solution is to extend today’s RF Spectrum Management (RFSM) and Wireless LAN Assurance (WLA) tools with new functionality -- what we call Spectrum Assurance (SA) (enough acronyms for you?). These are basically spectrum analyzers designed for use in a WiFi environment, and the one I really like (and use and recommend) is Spectrum Expert from Cognio Inc. I’ve been using this product for a bunch of production and experimental exercises, and I’ve found it invaluable for identifying and mitigating interference -- in other words, dealing, and rather effectively, with the problem some believe is insurmountable. Again, I’ll shortly publish the results of some real-world interference analysis I’ve been doing, but for now have a look at our latest White Paper and Tech Note on this subject, which you can find here and here. I’ll have the test results for you later this month or thereabouts.

— Craig Mathias is Principal Analyst at the Farpoint Group , an advisory firm specializing in wireless communications and mobile computing. Special to Unstrung

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