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Carrier WiFi

Is Jamming Really a Problem?

3:00 PM -- In my recent White Paper on Interference, I alluded to the possibility of outright jamming of the unlicensed bands. By this I mean someone building a device that would simply put up an impenetrable blanket of radiation (Gaussian white noise comes to mind) at significantly greater power than the 100 mW that is more or less typical in WLANs today. To my knowledge, no one has ever attempted such a wireless denial of service attack in anger, but it’s certainly possible. I’m not even sure if such would be illegal if the power level of the jammer were within the regulatory limits -- and that’s 1 Watt plus 6 dBi of antenna gain -- or about 4 watts!

I’m often asked if this is easy to do. And, yes, it is. And criminals might not want to stop at 4 Watts; ignoring the law is what makes them criminals, after all. Anyone with a basic knowledge of electronics should be able to build such a device, but you can even buy one today if you want. I’ve had second thoughts about providing the following link, but, heck, readers of this blog tend to be a pretty bright bunch and finding something like this really doesn’t take all that much work. But, anyway, click here. Want a jammer? You got it, although (fortunately) it’s not really cheap.

The real kicker is that even in the presence of a jamming signal, users might see five bars worth of signal and zero throughput. The help desk would likely be puzzled as well. The solution, of course, is a spectrum assurance (SA) tool, always monitoring for such energy, and alerting operations staff when it appears. Dealing with the threat involves localization and then what I call crowbar remediation -- finding the offending device and sending it to electronics heaven with gentle taps from a crowbar.

Want to really lose some sleep? Just how hard might it be to jam cellular or other licensed signals? Like I said, criminals really don’t care. And this implies spectrum assurance for all wireless signals and services is likely to become a core requirement over time.

— 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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