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Comment by wpietri | Hacker News Reader

How is wi-fi interference an "imaginary" problem?

Note, for example, the many stories people tell about microwave ovens interfering with wifi:

https://www.google.com/search?q=wifi+interference+microwave

And when open up a spectrum analyzer and look at how much power is on the wifi bands around me, it sure looks like interference is an actual thing. So it seems to me that interference is a real problem, which is why we have the FCC regulating this stuff in the first place.

The right they have, by the way, is that we the people created the FCC to solve the problem of radio interference:

https://en.wikipedia.org/wiki/Federal_Radio_Commission

Now it could be that there are better ways to solve the problem. But given the people totally losing their shit in classic "ehrmegerd guvmint steelin my freedums" style, I am wondering if this issue belongs in my bucket labeled "antivax, fiat money, 911 truth, etc".

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2.4 Ghz was chosen because it has interference from microwaves:

http://www.wired.com/2010/09/wireless-explainer/

The "imaginary problem" (I don't know how imaginary it is) is people modifying software so that their devices interfere with other, licensed frequencies.

Personally, I don't think there are many people that will buy an SDR and amplify the signal outside of legal ranges. I also think that any people that will do that are also capable and willing to that without the convenience of SDR.

I can imagine this theoretically being a problem with wifi routers: "Download this custom build of OpenWRT and this custom wifi driver, and you can get wifi without interference from your neighbors".

The reason there is so much interference on WiFi channels is because there is little regulation within the assigned frequencies.

People playing around with unlocked SDRs is not even a rounding error when it comes to causes of interference.

The myth of interference – Internet architect David Reed explains how bad science created the broadcast industry.

http://www.salon.com/2003/03/12/spectrum/

And when someone proposes a viable technology that could actually work the way Reed contemplates, we can and should review these kinds of regulations.

Right now, today, in the real world, it doesn't matter whether the phenomenon we commonly call interference is a property of radio waves or a property of the receivers we use or the will of benevolent aliens watching us in their lab. The fact is that it causes communications systems not to work properly.

Ultrawideband exists today. It's not in common use because the FCC restricted it to such low power it has about a 30 foot range.

What would be the effect of the Ultrawideband that exists today on other devices using the relevant radio frequencies, absent that regulation? Put another way, what was the justification for imposing such a restrictive rule?

> what was the justification for imposing such a restrictive rule?

This is a totally worthless question to ask about a law or rule.

The general form would be "why was the law created?"

And of course, there's never a law with the (disclosed) purpose of killing all kittens, giving money to friends or destroying an enemy. On the contrary, every law is always spun on some kind of "will you think of the children".

The only good question you can ask about a law:

"What are its consequences?"

Interestingly, your first question was more in this sense.

I believe that Silhouette's question was rhetorical. The answer, of course, is that UWB radio broadcast significantly impair conventional heterodyne radio receivers.

> The only good question you can ask about a law:

> "What are its consequences?"

Also, what are the consequences of not having the law?

Which I suspect was the intended meaning of:

> what was the justification for imposing such a restrictive rule?

The effect would be an increase in the noise floor. Narrowband incumbents claimed it would be very disruptive, UWB advocates claimed it would be slight. I don't have the expertise to say who's correct, but find myself more suspicious of the side with billions invested in narrowband spectrum that could be made obsolete, and less suspicious of the academic researchers advocating UWB.

Nobody could make a UWB system that runs effectively over coax for cable companies. That isn't FCC getting in the way.

More interesting is the question of whether there are other forces involved. Cringely postulates the NSA, but I do think incumbents more likely:

http://www.cringely.com/2014/05/15/nsa-help-kill-uwb/

I don't see how trouble with coax is relevant to wireless. The main point of UWB is high-bandwidth wireless, and the FCC is certainly preventing that.

The main point of UWB was making it work.

UWB should, in theory, be able to pump a lot more bandwidth down the same wires. Both the cable companies and the phone companies would be salivating at a system that effectively automatically avoids nulls on coax or twisted pair.

However, UWB requires highly accurate, synchronized clocks. Keeping those clocks in sync is non-trivial.

The fact that they could never get it to work over wire means that they had no hope over wireless.

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