Let My Spectrum Go
from the denial-of-interference dept
The topic of open spectrum certainly isn’t new. However, it’s suddenly getting a lot more attention. Yesterday, the Economist had a nice backgrounder on the debate (though, they screwed up a few facts), and today Clay Shirky has written up a long piece in defense of opening up more spectrum. Opening up more spectrum, especially a lot of the valuable spectrum the broadcasters are hoarding, would be a huge deal, and could be very helpful for a variety of industries and the overall economy. However, as I pointed out yesterday, it’s not quite that easy. While it’s clear that those who benefit from a world where spectrum is scarce are over-playing the fear of more unlicensed spectrum, interference still is a problem. Shirky cites one test that showed where interference wasn’t a problem, but to use that one story to suggest there are no interference problems denies what plenty of folks in the wireless industry see every day. He also uses WiFi as an example that interference isn’t a problem — which is news to anyone who has ever discovered just how much a problem interference can be on a WiFi system (I had to return a cordless phone that disconnected my home WiFi every time I took a call). I’m all for freeing up more spectrum, but the wireless industry needs to do a better job showing how they will deal with the interference issues, and proving that it really won’t be a problem. Let them come up with real solutions to the interference problems people see every day, and then, absolutely, let’s free up more spectrum.
Comments on “Let My Spectrum Go”
Interference is electronics, not physics
Electromagnetic waves do not interfere with one other. So-called “interference” is really an artifact of engineering design decisions made early in the twentieth century, and perpetuated to this day. Channels can be made arbitrarily narrow, limited only by the cost of the electronics we choose to use. If we’d be willing to increase the cost of any radio-frequency device we use by just a few bucks — and if the FCC would join the 21st century — we’d have arbitrarily as much spectrum as we choose to have. We need to stop perpetuating the myth that spectrum is fundamentally limited. That’s like saying there are only so many colors in the rainbow.
Re: Interference is electronics, not physics
I doubt Shannon would have agreed with you, as you have stated it.
Re: Re: Interference is electronics, not physics
Your comment regarding Shannon is right on the money.
Further there are serious physics / mathemetics problems to consider. First is that all electronics that amplifies is non linear. Hence the interference (IM). Second is that signal processing is necessarilly constraned by being done in minimum phase. Third the Economist article ignores the fact that there is a minimum code seperation in any CDM over FDM schema (as there are minimum frequency distances in a pure FDM schema). Likewise there are minimum distances between slots in a TDM scheme.
I love the directional antenna idea. To get a certain directivity a certain aperture (in wavelengths) is required. For most reaonable size objects this means that wvelengths have to be short.
My point is that the spectrum is a finite resource. The Ecenomist is simply ignoring well known problems. If they know how to solve them then they should say so.
Re: Interference is electronics, not physics
Indeed. You are absolutely right… it is an electronics, not a physics problem. But, let’s face reality, the electronics DO CAUSE INTERFERENCE right now. Simply opening up the spectrum doesn’t change that. Fixing the electronics would. So, let’s fix the electronics and THEN talk about opening the spectrum.
Beyond the physics
Doesn’t this tie into Western notions of respecting personal boundaries/space? Westerners, Americans in particular, take offense when people stand too close to them, or crash into them without saying anything, or reach around them to get a spoon without saying anything. The cell phone culture challenges the culture of personal boundaries, though so far people have not put up great resistance yet. In a “globalized” world, will the airwaves start to look more like a street scene in Calcutta, where a mother in a crowded bus might place a baby on a stranger’s lap without asking, or people go to the bathroom in the middle of the street?
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